10-Q

UNITED STATES SECURITIES AND EXCHANGE COMMISSION

WASHINGTON, D.C. 20549

FORM 10-Q

ý	QUARTERLY REPORT PURSUANT TO SECTION 13 OR 15(d) OF
	THE SECURITIES EXCHANGE ACT OF 1934

For The Quarterly Period Ended March 31, 2013

OR

o	TRANSITION REPORT PURSUANT TO SECTION 13 OR 15(d) OF
	THE SECURITIES EXCHANGE ACT OF 1934

For the Transition Period from _____________ to ______________

Commission file number 1-3480

MDU Resources Group, Inc.

(Exact name of registrant as specified in its charter)

Delaware	41-0423660
(State or other jurisdiction of incorporation or organization)	(I.R.S. Employer Identification No.)

1200 West Century Avenue

P.O. Box 5650

Bismarck, North Dakota 58506-5650

(Address of principal executive offices)

(Zip Code)

(701) 530-1000

(Registrant's telephone number, including area code)

Indicate by check mark whether the registrant (1) has filed all reports required to be filed by Section 13 or 15(d) of the Securities Exchange Act of 1934 during the preceding 12 months (or for such shorter period that the registrant was required to file such reports), and (2) has been subject to such filing requirements for the past 90 days. Yes ý No o.

Indicate by check mark whether the registrant has submitted electronically and posted on its corporate Web site, if any, every Interactive Data File required to be submitted and posted pursuant to Rule 405 of Regulation S-T during the preceding 12 months (or for such shorter period that the registrant was required to submit and post such files). Yes ý No o.

Indicate by check mark whether the registrant is a large accelerated filer, an accelerated filer, a non-accelerated filer, or a smaller reporting company. See the definition of "large accelerated filer," "accelerated filer" and "smaller reporting company" in Rule 12b-2 of the Exchange Act (Check one):

Large accelerated filer ý	Accelerated filer o
Non-accelerated filer o	Smaller reporting company o

(Do not check if a smaller reporting company)

Indicate by check mark whether the registrant is a shell company (as defined in Rule 12b-2 of the Exchange Act). Yes o No ý.

Indicate the number of shares outstanding of each of the issuer's classes of common stock, as of April 30, 2013: 188,830,529 shares.

DEFINITIONS

The following abbreviations and acronyms used in this Form 10-Q are defined below:

Abbreviation or Acronym
2012 Annual Report	Company's Annual Report on Form 10-K for the year ended December 31, 2012
Alusa	Tecnica de Engenharia Electrica - Alusa
ASC	FASB Accounting Standards Codification
BART	Best available retrofit technology
Bbl	Barrel
Bicent	Bicent Power LLC
Big Stone Station	475-MW coal-fired electric generating facility near Big Stone City, South Dakota (22.7 percent ownership)
BOE	One barrel of oil equivalent - determined using the ratio of one barrel of crude oil, condensate or natural gas liquids to six Mcf of natural gas
BOPD	Barrels of oil per day
Brazilian Transmission Lines	Company's equity method investment in the company owning ECTE, ENTE and ERTE (ownership interests in ENTE and ERTE were sold in the fourth quarter of 2010 and portions of the ownership interest in ECTE were sold in the third quarter of 2012 and the fourth quarters of 2011 and 2010)
Btu	British thermal unit
Calumet	Calumet Specialty Products Partners, L.P.
Cascade	Cascade Natural Gas Corporation, an indirect wholly owned subsidiary of MDU Energy Capital
CELESC	Centrais Elétricas de Santa Catarina S.A.
CEM	Colorado Energy Management, LLC, a former direct wholly owned subsidiary of Centennial Resources (sold in the third quarter of 2007)
CEMIG	Companhia Energética de Minas Gerais
Centennial	Centennial Energy Holdings, Inc., a direct wholly owned subsidiary of the Company
Centennial Capital	Centennial Holdings Capital LLC, a direct wholly owned subsidiary of Centennial
Centennial Resources	Centennial Energy Resources LLC, a direct wholly owned subsidiary of Centennial
Colorado State District Court	Colorado Thirteenth Judicial District Court, Yuma County
Company	MDU Resources Group, Inc.
Coyote Creek	Coyote Creek Mining Company, LLC, a subsidiary of The North American Coal Corporation
Coyote Station	427-MW coal-fired electric generating facility near Beulah, North Dakota (25 percent ownership)
Dakota Prairie Refining	Dakota Prairie Refining, LLC
dk	Decatherm
Dodd-Frank Act	Dodd-Frank Wall Street Reform and Consumer Protection Act
ECTE	Empresa Catarinense de Transmissão de Energia S.A. (5.01 percent ownership interest at March 31, 2013, 2.5, 2.5 and 14.99 percent ownership interests were sold in the third quarter of 2012 and the fourth quarters of 2011 and 2010, respectively)
ENTE	Empresa Norte de Transmissão de Energia S.A. (entire 13.3 percent ownership interest sold in the fourth quarter of 2010)
EPA	U.S. Environmental Protection Agency
ERTE	Empresa Regional de Transmissão de Energia S.A. (entire 13.3 percent ownership interest sold in the fourth quarter of 2010)
Exchange Act	Securities Exchange Act of 1934, as amended
FASB	Financial Accounting Standards Board
Fidelity	Fidelity Exploration & Production Company, a direct wholly owned subsidiary of WBI Holdings
GAAP	Accounting principles generally accepted in the United States of America
GHG	Greenhouse gas
Great Plains	Great Plains Natural Gas Co., a public utility division of the Company
Hawaiian Cement	Hawaiian Cement, an indirect wholly owned subsidiary of Knife River
Intermountain	Intermountain Gas Company, an indirect wholly owned subsidiary of MDU Energy Capital
JTL	JTL Group, Inc., an indirect wholly owned subsidiary of Knife River
Knife River	Knife River Corporation, a direct wholly owned subsidiary of Centennial
Knife River - Northwest	Knife River Corporation - Northwest, an indirect wholly owned subsidiary of Knife River
kWh	Kilowatt-hour

2

LPP	Lea Power Partners, LLC, a former indirect wholly owned subsidiary of Centennial Resources (member interests were sold in October 2006)
LWG	Lower Willamette Group
MBbls	Thousands of barrels
MBOE	Thousands of BOE
Mcf	Thousand cubic feet
MDU Brasil	MDU Brasil Ltda., an indirect wholly owned subsidiary of Centennial Resources
MDU Construction Services	MDU Construction Services Group, Inc., a direct wholly owned subsidiary of Centennial
MDU Energy Capital	MDU Energy Capital, LLC, a direct wholly owned subsidiary of the Company
MMBtu	Million Btu
MMcf	Million cubic feet
MMdk	Million decatherms
Montana-Dakota	Montana-Dakota Utilities Co., a public utility division of the Company
Montana DEQ	Montana Department of Environmental Quality
Montana First Judicial District Court	Montana First Judicial District Court, Lewis and Clark County
Montana Seventeenth Judicial District Court	Montana Seventeenth Judicial District Court, Phillips County
MTPSC	Montana Public Service Commission
MW	Megawatt
NDPSC	North Dakota Public Service Commission
New York Supreme Court	Supreme Court of the State of New York, County of New York
NGL	Natural gas liquids
Oil	Includes crude oil and condensate
Omimex	Omimex Canada, Ltd.
OPUC	Oregon Public Utility Commission
Oregon DEQ	Oregon State Department of Environmental Quality
Prairielands	Prairielands Energy Marketing, Inc., an indirect wholly owned subsidiary of WBI Holdings
PRP	Potentially Responsible Party
psi	pounds per square inch
ROD	Record of Decision
SDPUC	South Dakota Public Utilities Commission
SEC	U.S. Securities and Exchange Commission
Securities Act	Securities Act of 1933, as amended
SourceGas	SourceGas Distribution LLC
VIE	Variable interest entity
WBI Energy	WBI Energy, Inc., an indirect wholly owned subsidiary of WBI Holdings
WBI Energy Midstream	WBI Energy Midstream, LLC an indirect wholly owned subsidiary of WBI Holdings (previously Bitter Creek Pipelines, LLC, name changed effective July 1, 2012)
WBI Energy Transmission	WBI Energy Transmission, Inc., an indirect wholly owned subsidiary of WBI Holdings (previously Williston Basin Interstate Pipeline Company, name changed effective July 1, 2012)
WBI Holdings	WBI Holdings, Inc., a direct wholly owned subsidiary of Centennial
WUTC	Washington Utilities and Transportation Commission

3

INTRODUCTION

The Company is a diversified natural resource company, which was incorporated under the laws of the state of Delaware in 1924. Its principal executive offices are at 1200 West Century Avenue, P.O. Box 5650, Bismarck, North Dakota 58506-5650, telephone (701) 530-1000.

Montana-Dakota, through the electric and natural gas distribution segments, generates, transmits and distributes electricity and distributes natural gas in Montana, North Dakota, South Dakota and Wyoming. Cascade distributes natural gas in Oregon and Washington. Intermountain distributes natural gas in Idaho. Great Plains distributes natural gas in western Minnesota and southeastern North Dakota. These operations also supply related value-added services.

The Company, through its wholly owned subsidiary, Centennial, owns WBI Holdings (comprised of the pipeline and energy services and the exploration and production segments), Knife River (construction materials and contracting segment), MDU Construction Services (construction services segment), Centennial Resources and Centennial Capital (both reflected in the Other category). For more information on the Company's business segments, see Note 15.

4

INDEX

Part I -- Financial Information	Page
Consolidated Statements of Income -- Three Months Ended March 31, 2013 and 2012	6
Consolidated Statements of Comprehensive Income -- Three Months Ended March 31, 2013 and 2012	7
Consolidated Balance Sheets -- March 31, 2013 and 2012, and December 31, 2012	8
Consolidated Statements of Cash Flows -- Three Months Ended March 31, 2013 and 2012	9
Notes to Consolidated Financial Statements	10
Management's Discussion and Analysis of Financial Condition and Results of Operations	29
Quantitative and Qualitative Disclosures About Market Risk	43
Controls and Procedures	44
Part II -- Other Information
Legal Proceedings	44
Risk Factors	44
Mine Safety Disclosures	45
Exhibits	45
Signatures	46
Exhibit Index	47
Exhibits

5

PART I -- FINANCIAL INFORMATION

ITEM 1.  FINANCIAL STATEMENTS

MDU RESOURCES GROUP, INC.

CONSOLIDATED STATEMENTS OF INCOME

(Unaudited)

	Three Months Ended
	March 31,
	2013			2012
	(In thousands, except per share amounts)
Operating revenues:
Electric, natural gas distribution and pipeline and energy services	$	424,124		$	395,081
Exploration and production, construction materials and contracting, construction services and other	507,480			457,726
Total operating revenues	931,604			852,807
Operating expenses:
Fuel and purchased power	21,608			18,420
Purchased natural gas sold	199,187			185,428
Operation and maintenance:
Electric, natural gas distribution and pipeline and energy services	66,101			68,401
Exploration and production, construction materials and contracting, construction services and other	394,019			376,146
Depreciation, depletion and amortization	93,561			85,380
Taxes, other than income	52,597			47,975
Total operating expenses	827,073			781,750
Operating income	104,531			71,057
Earnings (loss) from equity method investments	(311		)	1,253
Other income	1,242			1,098
Interest expense	20,874			19,439
Income before income taxes	84,588			53,969
Income taxes	27,996			18,079
Income from continuing operations	56,592			35,890
Loss from discontinued operations, net of tax (Note 9)	(77		)	(100		)
Net income	56,515			35,790
Dividends declared on preferred stocks	171			171
Earnings on common stock	$	56,344		$	35,619
Earnings per common share - basic:
Earnings before discontinued operations	$	.30		$	.19
Discontinued operations, net of tax	—			—
Earnings per common share - basic	$	.30		$	.19
Earnings per common share - diluted:
Earnings before discontinued operations	$	.30		$	.19
Discontinued operations, net of tax	—			—
Earnings per common share - diluted	$	.30		$	.19
Dividends declared per common share	$	.1725		$	.1675
Weighted average common shares outstanding - basic	188,831			188,811
Weighted average common shares outstanding - diluted	189,222			189,182

The accompanying notes are an integral part of these consolidated financial statements.

6

MDU RESOURCES GROUP, INC.

CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME

(Unaudited)

	Three Months Ended
	March 31,
	2013			2012
	(In thousands)
Net income	$	56,515		$	35,790
Other comprehensive loss:
Net unrealized loss on derivative instruments qualifying as hedges:
Net unrealized loss on derivative instruments arising during the period, net of tax of $(3,168) and $(2,225) in 2013 and 2012, respectively	(5,849		)	(3,770		)
Less: Reclassification adjustment for gain on derivative instruments included in net income, net of tax of $1,626 and $1,366 in 2013 and 2012, respectively	2,772			2,329
Net unrealized loss on derivative instruments qualifying as hedges	(8,621		)	(6,099		)
Net unrealized gain (loss) on available-for-sale investments:
Net unrealized loss on available-for-sale investments arising during the period, net of tax of $(24) and $(2) in 2013 and 2012, respectively	(44		)	(4		)
Less: Reclassification adjustment for loss on available-for-sale investments included in net income, net of tax of $(19) and $(16) in 2013 and 2012, respectively	(35		)	(30		)
Net unrealized gain (loss) on available-for-sale investments	(9		)	26
Amortization of postretirement liability losses included in net periodic benefit cost, net of tax of $319 in 2013	648			—
Foreign currency translation adjustment, net of tax of $37 and $138 in 2013 and 2012, respectively	88			144
Other comprehensive loss	(7,894		)	(5,929		)
Comprehensive income	$	48,621		$	29,861

The accompanying notes are an integral part of these consolidated financial statements.

7

MDU RESOURCES GROUP, INC.

CONSOLIDATED BALANCE SHEETS

(Unaudited)

	March 31, 2013			March 31, 2012			December 31, 2012
(In thousands, except shares and per share amounts)
ASSETS
Current assets:
Cash and cash equivalents	$	74,149		$	91,389		$	49,042
Receivables, net	635,564			539,589			678,123
Inventories	334,872			313,341			317,415
Deferred income taxes	29,885			42,239			22,846
Commodity derivative instruments	5,936			26,698			18,304
Prepayments and other current assets	68,828			64,897			42,351
Total current assets	1,149,234			1,078,153			1,128,081
Investments	106,846			113,799			103,243
Property, plant and equipment	8,303,065			7,798,770			8,107,751
Less accumulated depreciation, depletion and amortization	3,678,535			3,419,574			3,608,912
Net property, plant and equipment	4,624,530			4,379,196			4,498,839
Deferred charges and other assets:
Goodwill	636,039			635,389			636,039
Other intangible assets, net	16,318			19,991			17,129
Other	295,215			312,103			299,160
Total deferred charges and other assets	947,572			967,483			952,328
Total assets	$	6,828,182		$	6,538,631		$	6,682,491
LIABILITIES AND EQUITY
Current liabilities:
Short-term borrowings	$	37,500		$	—		$	28,200
Long-term debt due within one year	171,094			202,215			134,108
Accounts payable	375,942			321,369			388,015
Taxes payable	55,748			51,019			46,475
Dividends payable	32,744			31,800			171
Accrued compensation	31,382			28,463			48,448
Commodity derivative instruments	7,379			20,183			—
Other accrued liabilities	205,394			255,172			204,698
Total current liabilities	917,183			910,221			850,115
Long-term debt	1,618,569			1,213,974			1,610,867
Deferred credits and other liabilities:
Deferred income taxes	802,805			798,669			755,102
Other liabilities	814,643			842,169			818,159
Total deferred credits and other liabilities	1,617,448			1,640,838			1,573,261
Commitments and contingencies
Equity:
Preferred stocks	15,000			15,000			15,000
Common stockholders' equity:
Common stock
Authorized - 500,000,000 shares, $1.00 par value
Shares issued - 189,369,450 at March 31, 2013 and 2012 and December 31, 2012	189,369			189,369			189,369
Other paid-in capital	1,038,970			1,035,800			1,039,080
Retained earnings	1,480,784			1,589,985			1,457,146
Accumulated other comprehensive loss	(56,615		)	(52,930		)	(48,721		)
Treasury stock at cost - 538,921 shares	(3,626		)	(3,626		)	(3,626		)
Total common stockholders' equity	2,648,882			2,758,598			2,633,248
Total stockholders' equity	2,663,882			2,773,598			2,648,248
Noncontrolling interest	11,100			—			—
Total equity	2,674,982			2,773,598			2,648,248
Total liabilities and equity	$	6,828,182		$	6,538,631		$	6,682,491

The accompanying notes are an integral part of these consolidated financial statements.

8

MDU RESOURCES GROUP, INC.

CONSOLIDATED STATEMENTS OF CASH FLOWS

(Unaudited)

	Three Months Ended
	March 31,
	2013			2012
	(In thousands)
Operating activities:
Net income	$	56,515		$	35,790
Loss from discontinued operations, net of tax	(77		)	(100		)
Income from continuing operations	56,592			35,890
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation, depletion and amortization	93,561			85,380
Earnings, net of distributions, from equity method investments	1,277			1,181
Deferred income taxes	44,663			32,596
Changes in current assets and liabilities, net of acquisitions:
Receivables	32,206			101,917
Inventories	(19,126		)	(38,357		)
Other current assets	(25,855		)	(21,556		)
Accounts payable	(35,091		)	(29,851		)
Other current liabilities	(7,338		)	(33,751		)
Other noncurrent changes	(4,318		)	(8,349		)
Net cash provided by continuing operations	136,571			125,100
Net cash provided by (used in) discontinued operations	303			(107		)
Net cash provided by operating activities	136,874			124,993
Investing activities:
Capital expenditures	(188,475		)	(174,429		)
Acquisitions, net of cash acquired	—			(242		)
Net proceeds from sale or disposition of property and other	18,176			18,256
Investments	(514		)	(27		)
Net cash used in continuing operations	(170,813		)	(156,442		)
Net cash provided by discontinued operations	—			—
Net cash used in investing activities	(170,813		)	(156,442		)
Financing activities:
Issuance of short-term borrowings	9,300			—
Issuance of long-term debt	112,015			—
Repayment of long-term debt	(67,123		)	(8,297		)
Proceeds from issuance of common stock	—			88
Dividends paid	(171		)	(31,794		)
Excess tax benefit on stock-based compensation	—			26
Contribution from noncontrolling interest	5,000			—
Net cash provided by (used in) continuing operations	59,021			(39,977		)
Net cash provided by discontinued operations	—			—
Net cash provided by (used in) financing activities	59,021			(39,977		)
Effect of exchange rate changes on cash and cash equivalents	25			43
Increase (decrease) in cash and cash equivalents	25,107			(71,383		)
Cash and cash equivalents -- beginning of year	49,042			162,772
Cash and cash equivalents -- end of period	$	74,149		$	91,389

The accompanying notes are an integral part of these consolidated financial statements.

9

MDU RESOURCES GROUP, INC.

NOTES TO CONSOLIDATED

FINANCIAL STATEMENTS

March 31, 2013 and 2012

(Unaudited)

Note 1 - Basis of presentation

The accompanying consolidated interim financial statements were prepared in conformity with the basis of presentation reflected in the consolidated financial statements included in the Company's 2012 Annual Report, and the standards of accounting measurement set forth in the interim reporting guidance in the ASC and any amendments thereto adopted by the FASB. Interim financial statements do not include all disclosures provided in annual financial statements and, accordingly, these financial statements should be read in conjunction with those appearing in the 2012 Annual Report. The information is unaudited but includes all adjustments that are, in the opinion of management, necessary for a fair presentation of the accompanying consolidated interim financial statements and are of a normal recurring nature. Depreciation, depletion and amortization expense is reported separately on the Consolidated Statements of Income and therefore is excluded from the other line items within operating expenses. Management has also evaluated the impact of events occurring after March 31, 2013, up to the date of issuance of these consolidated interim financial statements.

Note 2 - Seasonality of operations

Some of the Company's operations are highly seasonal and revenues from, and certain expenses for, such operations may fluctuate significantly among quarterly periods. Accordingly, the interim results for particular businesses, and for the Company as a whole, may not be indicative of results for the full fiscal year.

Note 3 - Accounts receivable and allowance for doubtful accounts

Accounts receivable consists primarily of trade receivables from the sale of goods and services which are recorded at the invoiced amount net of allowance for doubtful accounts, and costs and estimated earnings in excess of billings on uncompleted contracts. The total balance of receivables past due 90 days or more was $39.6 million, $34.6 million and $34.3 million as of March 31, 2013 and 2012, and December 31, 2012, respectively.

The allowance for doubtful accounts is determined through a review of past due balances and other specific account data. Account balances are written off when management determines the amounts to be uncollectible. The Company's allowance for doubtful accounts as of March 31, 2013 and 2012, and December 31, 2012, was $10.8 million, $12.2 million and $10.8 million, respectively.

Note 4 - Inventories and natural gas in storage

Inventories, other than natural gas in storage for the Company's regulated operations, were stated at the lower of average cost or market value. Natural gas in storage for the Company's regulated operations is generally carried at average cost, or cost using the last-in, first-out method. The portion of the cost of natural gas in storage expected to be used within one year was included in inventories. Inventories consisted of:

	March 31, 2013		March 31, 2012		December 31, 2012
	(In thousands)
Aggregates held for resale	$	98,120	$	85,958	$	87,715
Asphalt oil	94,332		82,949		67,480
Materials and supplies	75,868		68,369		69,390
Merchandise for resale	24,342		28,459		31,172
Natural gas in storage (current)	12,811		15,475		29,030
Other	29,399		32,131		32,628
Total	$	334,872	$	313,341	$	317,415

The remainder of natural gas in storage, which largely represents the cost of gas required to maintain pressure levels for normal operating purposes, was included in other assets and was $49.6 million, $50.3 million, and $49.7 million at March 31, 2013 and 2012, and December 31, 2012, respectively.

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Note 5 - Earnings per common share

Basic earnings per common share were computed by dividing earnings on common stock by the weighted average number of shares of common stock outstanding during the applicable period. Diluted earnings per common share were computed by dividing earnings on common stock by the total of the weighted average number of shares of common stock outstanding during the applicable period, plus the effect of outstanding performance share awards. Common stock outstanding includes issued shares less shares held in treasury. Net income was the same for both the basic and diluted earnings per share calculations. A reconciliation of the weighted average common shares outstanding used in the basic and diluted earnings per share calculation was as follows:

	Three Months Ended
	March 31,
	2013	2012
	(In thousands)
Weighted average common shares outstanding - basic	188,831	188,811
Effect of dilutive stock options and performance share awards	391	371
Weighted average common shares outstanding - diluted	189,222	189,182
Shares excluded from the calculation of diluted earnings per share	—	—

Note 6 - Cash flow information

Cash expenditures for interest and income taxes were as follows:

	Three Months Ended
	March 31,
	2013			2012
	(In thousands)
Interest, net of amount capitalized	$	21,857		$	22,433
Income taxes paid (refunded), net	$	(7,246	)	$	285

Noncash investing transactions were as follows:

	March 31,
	2013		2012
	(In thousands)
Property, plant and equipment additions in accounts payable	$	92,236	$	51,739

Note 7 - New accounting standards

Reporting of Amounts Reclassified Out of Accumulated Other Comprehensive Income In February 2013, the FASB issued guidance on the reporting of amounts reclassified out of accumulated other comprehensive income. This guidance requires an entity to report the effect of significant reclassifications out of accumulated other comprehensive income on the respective line items in net income if the amount being reclassified is required to be reclassified in its entirety to net income. Entities may present this information either on the face of the statement where net income is presented or in the notes. This guidance was effective for the Company on January 1, 2013, and is to be applied prospectively. The guidance required additional disclosures, however it did not impact the Company's results of operations, financial position or cash flows.

Disclosures about Offsetting Assets and Liabilities In December 2011, the FASB issued guidance on the disclosure requirements related to balance sheet offsetting. The new disclosure requirements relate to the nature of an entity's rights of offset and related arrangements associated with its financial instruments and derivative instruments. In January 2013, the FASB issued guidance clarifying the scope of the disclosures related to balance sheet offsetting. The amendments clarify that this guidance only applies to derivative instruments, repurchase agreements and securities lending transactions that are either offset or subject to an enforceable master netting arrangement. The guidance was effective for the Company on January 1, 2013, and must be applied retrospectively. The guidance required additional disclosures, however it did not impact the Company's results of operations, financial position or cash flows.

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Note 8 - Comprehensive income (loss)

The after-tax changes in the components of accumulated other comprehensive loss as of March 31, 2013, were as follows:

	Net Unrealized Gain (Loss) on Derivative  Instruments  Qualifying as Hedges			Net Unrealized Gain (Loss) on Available-for-sale Investments			Postretirement  Liability Adjustment			Foreign Currency Translation Adjustment			Total Accumulated  Other Comprehensive  Loss
	(In thousands)
Balance at December 31, 2012	$	6,018		$	119		$	(54,347	)	$	(511	)	$	(48,721	)
Other comprehensive income (loss) before reclassifications	(5,849		)	(44		)	—			88			(5,805		)
Amounts reclassified from accumulated other comprehensive loss	(2,772		)	35			648			—			(2,089		)
Net current-period other comprehensive loss	(8,621		)	(9		)	648			88			(7,894		)
Balance at March 31, 2013	$	(2,603	)	$	110		$	(53,699	)	$	(423	)	$	(56,615	)

Reclassifications out of accumulated other comprehensive loss were as follows:

	Three Months Ended			Location on Consolidated Statements of Income
	March 31,
	2013
	(In thousands)
Reclassification adjustment for gain (loss) on derivative instruments included in net income
Commodity derivative instruments	$	4,513		Operating revenues
Interest rate derivative instruments	(115		)	Interest expense
	4,398
	(1,626		)	Income taxes
	2,772
Amortization of postretirement liability losses included in net periodic benefit cost	(967		)	(a)
	319			Income taxes
	(648		)
Reclassification adjustment for loss on available-for-sale investments included in net income	(54		)	Other income
	19			Income taxes
	(35		)
Total reclassifications	$	2,089

(a) Included in net periodic pension cost (see Note 16 for additional details).

Note 9 - Discontinued operations

In 2007, Centennial Resources sold CEM to Bicent. In connection with the sale, Centennial Resources had agreed to indemnify Bicent and its affiliates from certain third party claims arising out of or in connection with Centennial Resources' ownership or operation of CEM prior to the sale. In addition, Centennial had previously guaranteed CEM's obligations under a construction contract. The Company incurs legal expenses and has accrued liabilities related to this matter. These items are reflected as discontinued operations in the consolidated financial statements and accompanying notes. Discontinued operations are included in the Other category. For more information, see Note 18.

Note 10 - Equity method investments

Investments in companies in which the Company has the ability to exercise significant influence over operating and financial policies are accounted for using the equity method. The Company's equity method investments at March 31, 2013, include ECTE.

In August 2006, MDU Brasil acquired ownership interests in the Brazilian Transmission Lines. The electric transmission lines are primarily in northeastern and southern Brazil. The transmission contracts provide for revenues denominated in the Brazilian

12

Real, annual inflation adjustments and change in tax law adjustments. The functional currency for the Brazilian Transmission Lines is the Brazilian Real.

In 2009, multiple sales agreements were signed for the Company to sell its ownership interest in the Brazilian Transmission Lines. In November 2010, the Company completed the sale of its entire ownership interest in ENTE and ERTE and 59.96 percent of the Company's ownership interest in ECTE. The remaining interest in ECTE is being purchased over a four-year period. In August 2012 and November 2011, the Company completed the sale of one-fourth of the remaining interest in each year. Alusa, CEMIG and CELESC hold the remaining ownership interests in ECTE.

At March 31, 2013 and 2012, and December 31, 2012, the equity method investments had total assets of $142.9 million, $105.3 million and $129.0 million, respectively, and long-term debt of $63.9 million, $35.9 million and $65.5 million, respectively. The Company's investment in its equity method investments was approximately $5.7 million, $8.2 million and $6.9 million, including undistributed earnings of $2.2 million, $2.2 million and $3.4 million, at March 31, 2013 and 2012, and December 31, 2012, respectively.

Note 11 - Goodwill and other intangible assets

The changes in the carrying amount of goodwill were as follows:

Three Months Ended March 31, 2013	Balance as of January 1, 2013*		Goodwill Acquired During the Year		Balance as of March 31, 2013*
	(In thousands)
Natural gas distribution	$	345,736	$	—	$	345,736
Pipeline and energy services	9,737		—		9,737
Construction materials and contracting	176,290		—		176,290
Construction services	104,276		—		104,276
Total	$	636,039	$	—	$	636,039

* Balance is presented net of accumulated impairment of $12.3 million at the pipeline and energy services segment, which occurred in prior periods.

Three Months Ended March 31, 2012	Balance as of January 1, 2012*		Goodwill Acquired During the Year**		Balance as of March 31, 2012*
	(In thousands)
Natural gas distribution	$	345,736	$	—	$	345,736
Pipeline and energy services	9,737		—		9,737
Construction materials and contracting	176,290		—		176,290
Construction services	103,168		458		103,626
Total	$	634,931	$	458	$	635,389

* Balance is presented net of accumulated impairment of $12.3 million at the pipeline and energy services segment, which occurred in prior periods.

** Includes contingent consideration that was not material related to an acquisition in a prior period.

13

Year Ended December 31, 2012	Balance as of January 1, 2012*		Goodwill Acquired During the Year**		Balance as of December 31, 2012*
	(In thousands)
Natural gas distribution	$	345,736	$	—	$	345,736
Pipeline and energy services	9,737		—		9,737
Construction materials and contracting	176,290		—		176,290
Construction services	103,168		1,108		104,276
Total	$	634,931	$	1,108	$	636,039

  * Balance is presented net of accumulated impairment of $12.3 million at the pipeline and energy services segment, which occurred in prior periods.

** Includes contingent consideration that was not material related to an acquisition in a prior period.

Other amortizable intangible assets were as follows:

	March 31, 2013			March 31, 2012			December 31, 2012
	(In thousands)
Customer relationships	$	21,310		$	21,010		$	21,310
Accumulated amortization	(12,211		)	(10,197		)	(11,701		)
	9,099			10,813			9,609
Noncompete agreements	7,236			7,086			7,236
Accumulated amortization	(5,439		)	(4,921		)	(5,326		)
	1,797			2,165			1,910
Other	10,979			11,442			10,979
Accumulated amortization	(5,557		)	(4,429		)	(5,369		)
	5,422			7,013			5,610
Total	$	16,318		$	19,991		$	17,129

Amortization expense for amortizable intangible assets for the three months ended March 31, 2013 and 2012, was $800,000 and $900,000, respectively. Estimated amortization expense for amortizable intangible assets is $3.7 million in 2013, $3.5 million in 2014, $2.6 million in 2015, $2.2 million in 2016, $1.9 million in 2017 and $3.2 million thereafter.

Note 12 - Derivative instruments

The Company's policy allows the use of derivative instruments as part of an overall energy price, foreign currency and interest rate risk management program to efficiently manage and minimize commodity price, foreign currency and interest rate risk. As of March 31, 2013, the Company had no outstanding foreign currency hedges. The following information should be read in conjunction with Notes 1 and 7 in the Company's Notes to Consolidated Financial Statements in the 2012 Annual Report.

Cascade

Cascade has historically utilized natural gas swap agreements to manage a portion of its regulated natural gas supply portfolio in order to manage fluctuations in the price of natural gas related to core customers in accordance with authority granted by the WUTC and OPUC. Core customers consist of residential, commercial and smaller industrial customers. As of March 31, 2013 and December 31, 2012, Cascade has no outstanding swap agreements. As of March 31, 2012, Cascade held a natural gas swap agreement with total forward notional volumes of 214,000 MMBtu. The fair value of derivative instruments must be estimated as of the end of each reporting period and is recorded on the Consolidated Balance Sheets as an asset or a liability. Periodic changes in the fair market value of the derivative instruments are recorded on the Consolidated Balance Sheets as a regulatory asset or a regulatory liability, and settlements of these arrangements are expected to be recovered through the purchased gas cost adjustment mechanism. Gains and losses on the settlements of these derivative instruments are recorded as a component of purchased natural gas sold on the Consolidated Statements of Income as they are recovered through the purchased gas cost adjustment mechanism. Under the terms of these arrangements, Cascade either pays or receives settlement payments based on the difference between the fixed strike price and the monthly index price applicable to each contract. For the three months ended March 31, 2012, the change in the fair market value of the derivative instruments of $52,000 was recorded as an increase to regulatory assets.

14

Fidelity

At March 31, 2013 and 2012, and December 31, 2012, Fidelity held oil swap and collar agreements with total forward notional volumes of 2.8 million, 4.0 million and 2.6 million Bbl, respectively, and natural gas swap agreements with total forward notional volumes of 25.9 million, 10.9 million  and 11.0 million MMBtu, respectively. In addition, at March 31, 2012, Fidelity held natural gas basis swap agreements with total forward notional volumes of 2.6 million MMBtu. Some of these agreements were designated as cash flow hedging instruments. Fidelity utilizes these derivative instruments to manage a portion of the market risk associated with fluctuations in the price of oil and natural gas and basis differentials on its forecasted sales of oil and natural gas production.

Centennial

At March 31, 2013 and 2012, and December 31, 2012, Centennial held interest rate swap agreements with total notional amounts of $40.0 million, $60.0 million and $50.0 million, respectively, which were designated as cash flow hedging instruments. Centennial entered into these interest rate derivative instruments to manage a portion of its interest rate exposure on the forecasted issuance of long-term debt. Centennial's interest rate swap agreements have mandatory termination dates ranging from May through June 2013.

Fidelity and Centennial

The fair value of the derivative instruments must be estimated as of the end of each reporting period and is recorded on the Consolidated Balance Sheets as an asset or liability. Changes in the fair value attributable to the effective portion of hedging instruments, net of tax, are recorded in stockholders' equity as a component of accumulated other comprehensive income (loss). To the extent that the hedges are not effective, the ineffective portion of the changes in fair market value is recorded directly in earnings.

There were no components of the derivative instruments' gain or loss excluded from the assessment of hedge effectiveness. Gains and losses must be reclassified into earnings as a result of the discontinuance of cash flow hedges if it is probable that the original forecasted transactions will not occur, and there were no such reclassifications.

Gains and losses on the oil and natural gas derivative instruments are reclassified from accumulated other comprehensive income (loss) into operating revenues on the Consolidated Statements of Income at the date the oil and natural gas quantities are settled. The proceeds received for oil and natural gas production are generally based on market prices. Gains and losses on the interest rate derivatives are reclassified from accumulated other comprehensive income (loss) into interest expense on the Consolidated Statements of Income in the same period the hedged item affects earnings. The gains and losses on derivative instruments were as follows:

	Three Months Ended
	March 31,
	2013			2012
	(In thousands)
Commodity derivatives designated as cash flow hedges:
Amount of loss recognized in accumulated other comprehensive loss (effective portion), net of tax	$	(6,154	)	$	(4,659	)
Amount of gain reclassified from accumulated other comprehensive loss into operating revenues (effective portion), net of tax	2,843			2,343
Amount of loss recognized in operating revenues (ineffective portion), before tax	(1,422		)	(4,251		)
Interest rate derivatives designated as cash flow hedges:
Amount of gain recognized in accumulated other comprehensive loss (effective portion), net of tax	305			889
Amount of loss reclassified from accumulated other comprehensive loss into interest expense (effective portion), net of tax	(71		)	(14		)
Amount of loss recognized in interest expense (ineffective portion), before tax	(159		)	—
Commodity derivatives not designated as hedging instruments:
Amount of gain (loss) recognized in operating revenues, before tax	(4,410		)	55

As of March 31, 2013, the maximum term of the derivative instruments, in which the exposure to the variability in future cash flows for forecasted transactions is being hedged, is 33 months.

15

Based on March 31, 2013, fair values, over the next 12 months net gains of approximately $1.5 million (after tax) are estimated to be reclassified from accumulated other comprehensive income (loss) into earnings, as the hedged transactions affect earnings.

Certain of Fidelity's and Centennial's derivative instruments contain cross-default provisions that state if Fidelity or any of its affiliates or Centennial fails to make payment with respect to certain indebtedness, in excess of specified amounts, the counterparties could require early settlement or termination of derivative instruments in liability positions. The aggregate fair value of Fidelity's and Centennial's derivative instruments with credit-risk-related contingent features that are in a liability position at March 31, 2013, was $12.4 million. The aggregate fair value of assets that would have been needed to settle the instruments immediately if the credit-risk-related contingent features were triggered on March 31, 2013, was $12.4 million.

The location and fair value of the gross amount of the Company's derivative instruments on the Consolidated Balance Sheets were as follows:

Asset Derivatives	Location on Consolidated Balance Sheets	Fair Value at March 31, 2013		Fair Value at March 31, 2012		Fair Value at December 31, 2012
		(In thousands)
Designated as hedges:
Commodity derivatives	Commodity derivative instruments	$	1,623	$	25,560	$	18,084
	Other assets - noncurrent	—		537		—
		1,623		26,097		18,084
Not designated as hedges:
Commodity derivatives	Commodity derivative instruments	4,313		1,138		220
	Other assets - noncurrent	243		45		—
		4,556		1,183		220
Total asset derivatives		$	6,179	$	27,280	$	18,304

Liability Derivatives	Location on Consolidated Balance Sheets	Fair Value at March 31, 2013		Fair Value at March 31, 2012		Fair Value at December 31, 2012
		(In thousands)
Designated as hedges:
Commodity derivatives	Commodity derivative instruments	$	5,994	$	18,964	$	—
	Other liabilities - noncurrent	534		6,098		—
Interest rate derivatives	Other accrued liabilities	4,458		1,168		6,255
	Other liabilities - noncurrent	—		2,153		—
		10,986		28,383		6,255
Not designated as hedges:
Commodity derivatives	Commodity derivative instruments	1,385		1,219		—
	Other liabilities - noncurrent	74		49		—
		1,459		1,268		—
Total liability derivatives		$	12,445	$	29,651	$	6,255

16

All of the Company's commodity and interest rate derivative instruments at March 31, 2013 and 2012, and December 31, 2012, were subject to legally enforceable master netting agreements. However, the Company's policy is to not offset fair value amounts for derivative instruments and, as a result, the Company's derivative assets and liabilities are presented gross on the Consolidated Balance Sheets. The gross derivative assets and liabilities (excluding settlement receivables and payables that may be subject to the same master netting agreements) presented on the Consolidated Balance Sheets and the amount eligible for offset under the master netting agreements is presented in the following table:

March 31, 2013	Gross Amounts Recognized on the Consolidated Balance Sheets		Gross Amounts Not Offset on the Consolidated Balance Sheets			Net
	(In thousands)
Assets:
Commodity derivatives	$	6,179	$	(3,578	)	$	2,601
Total assets	$	6,179	$	(3,578	)	$	2,601
Liabilities:
Commodity derivatives	$	7,987	$	(3,578	)	$	4,409
Interest rate derivatives	4,458		—			4,458
Total liabilities	$	12,445	$	(3,578	)	$	8,867

March 31, 2012	Gross Amounts Recognized on the Consolidated Balance Sheets		Gross Amounts Not Offset on the Consolidated Balance Sheets			Net
	(In thousands)
Assets:
Commodity derivatives	$	27,280	$	(15,805	)	$	11,475
Total assets	$	27,280	$	(15,805	)	$	11,475
Liabilities:
Commodity derivatives	$	26,330	$	(15,805	)	$	10,525
Interest rate derivatives	3,321		—			3,321
Total liabilities	$	29,651	$	(15,805	)	$	13,846

December 31, 2012	Gross Amounts Recognized on the Consolidated Balance Sheets		Gross Amounts Not Offset on the Consolidated Balance Sheets		Net
	(In thousands)
Assets:
Commodity derivatives	$	18,304	$	—	$	18,304
Total assets	$	18,304	$	—	$	18,304
Liabilities:
Interest rate derivatives	$	6,255	$	—	$	6,255
Total liabilities	$	6,255	$	—	$	6,255

Effective April 1, 2013, the Company has elected to de-designate all of its commodity derivative contracts that existed at March 31, 2013, that had been previously designated as cash flow hedges, and has elected to discontinue hedge accounting for its commodity derivatives prospectively. As a result, Fidelity will recognize all future gains and losses from prospective changes in commodity derivative fair values immediately in earnings rather than deferring any such amounts in accumulated other comprehensive income (loss).

17

Note 13 - Fair value measurements

The Company measures its investments in certain fixed-income and equity securities at fair value with changes in fair value recognized in income. The Company anticipates using these investments, which consist of an insurance contract, to satisfy its obligations under its unfunded, nonqualified benefit plans for executive officers and certain key management employees, and invests in these fixed-income and equity securities for the purpose of earning investment returns and capital appreciation. These investments, which totaled $53.3 million, $48.7 million and $48.9 million, as of March 31, 2013 and 2012, and December 31, 2012, respectively, are classified as Investments on the Consolidated Balance Sheets. The net unrealized gains on these investments were $4.4 million and $5.0 million for the three months ended March 31, 2013 and 2012, respectively. The change in fair value, which is considered part of the cost of the plan, is classified in operation and maintenance expense on the Consolidated Statements of Income.

The Company did not elect the fair value option, which records gains and losses in income, for its remaining available-for-sale securities, which include auction rate securities, mortgage-backed securities and U.S. Treasury securities. These available-for-sale securities are recorded at fair value and are classified as Investments on the Consolidated Balance Sheets. The Company's auction rate securities approximated cost and, as a result, there were no accumulated unrealized gains or losses recorded in accumulated other comprehensive income (loss) on the Consolidated Balance Sheets related to these investments. In the second quarter of 2012, the Company sold its auction rate securities at cost and did not realize any gains or losses. Unrealized gains or losses on mortgage-backed securities and U.S. Treasury securities are recorded in accumulated other comprehensive income (loss). Details of available-for-sale securities were as follows:

March 31, 2013	Cost		Gross Unrealized Gains		Gross Unrealized Losses			Fair Value
	(In thousands)
Insurance contract	$	37,270	$	16,064	$	—		$	53,334
Mortgage-backed securities	8,749		133		(3		)	8,879
U.S. Treasury securities	1,301		39		—			1,340
Total	$	47,320	$	16,236	$	(3	)	$	63,553

March 31, 2012	Cost		Gross Unrealized Gains		Gross Unrealized Losses			Fair Value
	(In thousands)
Insurance contract	$	37,250	$	11,454	$	—		$	48,704
Auction rate securities	11,400		—		—			11,400
Mortgage-backed securities	7,952		119		(1		)	8,070
U.S. Treasury securities	1,968		49		(1		)	2,016
Total	$	58,570	$	11,622	$	(2	)	$	70,190

December 31, 2012	Cost		Gross Unrealized Gains		Gross Unrealized Losses			Fair Value
	(In thousands)
Insurance contract	$	37,250	$	11,648	$	—		$	48,898
Mortgage-backed securities	8,054		144		(3		)	8,195
U.S. Treasury securities	1,763		43		—			1,806
Total	$	47,067	$	11,835	$	(3	)	$	58,899

The fair value of the Company's money market funds approximates cost.

Fair value is defined as the price that would be received to sell an asset or paid to transfer a liability (an exit price) in an orderly transaction between market participants at the measurement date. The ASC establishes a hierarchy for grouping assets and liabilities, based on the significance of inputs.

The estimated fair values of the Company's assets and liabilities measured on a recurring basis are determined using the market approach.

18

The Company's Level 2 money market funds consist of investments in short-term unsecured promissory notes and the value is based on comparable market transactions taking into consideration the credit quality of the issuer. The estimated fair value of the Company's Level 2 mortgage-backed securities and U.S. Treasury securities are based on comparable market transactions, other observable inputs or other sources, including pricing from outside sources.

The estimated fair value of the Company's Level 2 insurance contract is based on contractual cash surrender values that are determined primarily by investments in managed separate accounts of the insurer. These amounts approximate fair value. The managed separate accounts are valued based on other observable inputs or corroborated market data.

The estimated fair value of the Company's Level 2 commodity derivative instruments is based upon futures prices, volatility and time to maturity, among other things. Counterparty statements are utilized to determine the value of the commodity derivative instruments and are reviewed and corroborated using various methodologies and significant observable inputs. The Company's and the counterparties' nonperformance risk is also evaluated.

The estimated fair value of the Company's Level 2 interest rate derivative instruments is measured using quoted market prices or pricing models using prevailing market interest rates as of the measurement date. Counterparty statements are utilized to determine the value of the interest rate derivative instruments and are reviewed and corroborated using various methodologies and significant observable inputs. The Company's and the counterparties' nonperformance risk is also evaluated.

Though the Company believes the methods used to estimate fair value are consistent with those used by other market participants, the use of other methods or assumptions could result in a different estimate of fair value. For the three months ended March 31, 2013 and 2012, there were no transfers between Levels 1 and 2.

The Company's assets and liabilities measured at fair value on a recurring basis are as follows:

	Fair Value Measurements at March 31, 2013, Using
	Quoted Prices in Active Markets for Identical Assets (Level 1)		Significant Other Observable Inputs (Level 2)		Significant Unobservable Inputs (Level 3)		Balance at March 31, 2013
	(In thousands)
Assets:
Money market funds	$	—	$	31,281	$	—	$	31,281
Available-for-sale securities:
Insurance contract*	—		53,334		—		53,334
Mortgage-backed securities	—		8,879		—		8,879
U.S. Treasury securities	—		1,340		—		1,340
Commodity derivative instruments	—		6,179		—		6,179
Total assets measured at fair value	$	—	$	101,013	$	—	$	101,013
Liabilities:
Commodity derivative instruments	$	—	$	7,987	$	—	$	7,987
Interest rate derivative instruments	—		4,458		—		4,458
Total liabilities measured at fair value	$	—	$	12,445	$	—	$	12,445

*  The insurance contract invests approximately 29 percent in common stock of mid-cap companies, 28 percent in common stock of small-cap companies, 28 percent in common stock of large-cap companies and 15 percent in fixed-income and other investments.

19

	Fair Value Measurements at March 31, 2012, Using
	Quoted Prices in Active Markets for Identical Assets (Level 1)		Significant Other Observable Inputs (Level 2)		Significant Unobservable Inputs (Level 3)		Balance at March 31, 2012
	(In thousands)
Assets:
Money market funds	$	—	$	9,942	$	—	$	9,942
Available-for-sale securities:
Insurance contract*	—		48,704		—		48,704
Auction rate securities	—		11,400		—		11,400
Mortgage-backed securities	—		8,070		—		8,070
U.S. Treasury securities	—		2,016		—		2,016
Commodity derivative instruments	—		27,280		—		27,280
Total assets measured at fair value	$	—	$	107,412	$	—	$	107,412
Liabilities:
Commodity derivative instruments	$	—	$	26,330	$	—	$	26,330
Interest rate derivative instruments	—		3,321		—		3,321
Total liabilities measured at fair value	$	—	$	29,651	$	—	$	29,651

*  The insurance contract invests approximately 29 percent in common stock of mid-cap companies, 29 percent in common stock of small-cap companies, 29 percent in common stock of large-cap companies and 13 percent in fixed-income and other investments.

	Fair Value Measurements at December 31, 2012, Using
	Quoted Prices in Active Markets for Identical Assets (Level 1)		Significant Other Observable Inputs (Level 2)		Significant Unobservable Inputs  (Level 3)		Balance at December 31, 2012
	(In thousands)
Assets:
Money market funds	$	—	$	24,240	$	—	$	24,240
Available-for-sale securities:
Insurance contract*	—		48,898		—		48,898
Mortgage-backed securities	—		8,195		—		8,195
U.S. Treasury securities	—		1,806		—		1,806
Commodity derivative instruments	—		18,304		—		18,304
Total assets measured at fair value	$	—	$	101,443	$	—	$	101,443
Liabilities:
Interest rate derivative instruments	$	—	$	6,255	$	—	$	6,255
Total liabilities measured at fair value	$	—	$	6,255	$	—	$	6,255

* The insurance contract invests approximately 28 percent in common stock of mid-cap companies, 28 percent in common stock of small-cap companies, 29 percent in common stock of large-cap companies and 15 percent in fixed-income and other investments.

20

The Company's long-term debt is not measured at fair value on the Consolidated Balance Sheets and the fair value is being provided for disclosure purposes only. The fair value was based on discounted future cash flows using current market interest rates. The estimated fair value of the Company's Level 2 long-term debt was as follows:

	Carrying Amount		Fair Value
	(In thousands)
Long-term debt at March 31, 2013	$	1,789,663	$	1,925,859
Long-term debt at March 31, 2012	$	1,416,189	$	1,578,395
Long-term debt at December 31, 2012	$	1,744,975	$	1,888,135

The carrying amounts of the Company's remaining financial instruments included in current assets and current liabilities approximate their fair values.

Note 14 - Income taxes

In connection with the income tax examination for the 2007 through 2009 tax years, the Company recorded income tax expense of $2.2 million for unrecognized tax positions in the first quarter of 2012.

In addition, the Company had a reduction of deferred income tax expense of $2.5 million in the first quarter of 2012, due to a deferred income tax rate reduction related to state income tax apportionment.

It is likely that substantially all of the unrecognized tax benefits of $14.9 million, as well as interest, at March 31, 2013, will be settled in the next 12 months due to the anticipated settlement of federal and state audits.

Note 15 - Business segment data

The Company's reportable segments are those that are based on the Company's method of internal reporting, which generally segregates the strategic business units due to differences in products, services and regulation. The internal reporting of these operating segments is defined based on the reporting and review process used by the Company's chief executive officer and other management. The vast majority of the Company's operations are located within the United States. The Company also has an investment in a foreign country, which consists of Centennial Resources' equity method investment in ECTE.

The electric segment generates, transmits and distributes electricity in Montana, North Dakota, South Dakota and Wyoming. The natural gas distribution segment distributes natural gas in those states as well as in Idaho, Minnesota, Oregon and Washington. These operations also supply related value-added services.

The pipeline and energy services segment provides natural gas transportation, underground storage, processing and gathering services, as well as oil gathering, through regulated and nonregulated pipeline systems primarily in the Rocky Mountain and northern Great Plains regions of the United States. This segment is constructing a diesel topping plant to refine crude oil and also provides cathodic protection and other energy-related services.

The exploration and production segment is engaged in oil and natural gas acquisition, exploration, development and production activities in the Rocky Mountain and Mid-Continent regions of the United States and in and around the Gulf of Mexico.

The construction materials and contracting segment mines aggregates and markets crushed stone, sand, gravel and related construction materials, including ready-mixed concrete, cement, asphalt, liquid asphalt and other value-added products. It also performs integrated contracting services. This segment operates in the central, southern and western United States and Alaska and Hawaii.

The construction services segment specializes in constructing and maintaining electric and communication lines, gas pipelines, fire suppression systems, and external lighting and traffic signalization equipment. This segment also provides utility excavation services and inside electrical wiring, cabling and mechanical services, sells and distributes electrical materials, and manufactures and distributes specialty equipment.

The Other category includes the activities of Centennial Capital, which insures various types of risks as a captive insurer for certain of the Company's subsidiaries. The function of the captive insurer is to fund the deductible layers of the insured companies' general liability and automobile liability coverages. Centennial Capital also owns certain real and personal property. The Other category also includes Centennial Resources' equity method investment in ECTE.

21

The information below follows the same accounting policies as described in Note 1 of the Company's Notes to Consolidated Financial Statements in the 2012 Annual Report. Information on the Company's businesses was as follows:

Three Months Ended March 31, 2013	External Operating Revenues		Inter- segment Operating Revenues			Earnings on Common Stock
	(In thousands)
Electric	$	64,654	$	—		$	9,825
Natural gas distribution	331,754		—			32,518
Pipeline and energy services	27,716		18,718			2,330
	424,124		18,718			44,673
Exploration and production	115,363		9,812			20,284
Construction materials and contracting	161,977		4,294			(20,582		)
Construction services	229,806		1,574			11,664
Other	334		1,818			305
	507,480		17,498			11,671
Intersegment eliminations	—		(36,216		)	—
Total	$	931,604	$	—		$	56,344

Three Months Ended March 31, 2012	External Operating Revenues		Inter- segment Operating Revenues			Earnings on Common Stock
	(In thousands)
Electric	$	57,963	$	—		$	7,559
Natural gas distribution	307,891		—			25,508
Pipeline and energy services	29,227		20,409			2,760
	395,081		20,409			35,827
Exploration and production	88,494		11,328			12,930
Construction materials and contracting	149,268		151			(24,932		)
Construction services	218,151		25			11,403
Other	1,813		327			391
	457,726		11,831			(208		)
Intersegment eliminations	—		(32,240		)	—
Total	$	852,807	$	—		$	35,619

Earnings from electric, natural gas distribution and pipeline and energy services are substantially all from regulated operations. Earnings from exploration and production, construction materials and contracting, construction services and other are all from nonregulated operations.

22

Note 16 - Employee benefit plans

The Company has noncontributory defined benefit pension plans and other postretirement benefit plans for certain eligible employees. Components of net periodic benefit cost for the Company's pension and other postretirement benefit plans were as follows:

							Other
							Postretirement
	Pension Benefits						Benefits
Three Months Ended March 31,	2013			2012			2013			2012
	(In thousands)
Components of net periodic benefit cost:
Service cost	$	40		$	345		$	504		$	412
Interest cost	4,018			4,554			940			1,143
Expected return on assets	(5,083		)	(5,886		)	(1,107		)	(1,244		)
Amortization of prior service cost (credit)	18			(21		)	(364		)	(272		)
Amortization of net actuarial loss	1,864			1,681			671			526
Amortization of net transition obligation	—			—			—			532
Net periodic benefit cost, including amount capitalized	857			673			644			1,097
Less amount capitalized	110			234			29			138
Net periodic benefit cost	$	747		$	439		$	615		$	959

Defined pension plan benefits to all nonunion and certain union employees hired after December 31, 2005, were discontinued. Employees that would have been eligible for defined pension plan benefits are eligible to receive additional defined contribution plan benefits. Effective January 1, 2010, all benefit and service accruals for nonunion and certain union plans were frozen. Effective June 30, 2011 and September 30, 2012, all benefit and service accruals for certain additional union employees were frozen. These employees will be eligible to receive additional defined contribution plan benefits.

In addition to the qualified plan defined pension benefits reflected in the table, the Company has unfunded, nonqualified benefit plans for executive officers and certain key management employees that generally provide for defined benefit payments at age 65 following the employee's retirement or to their beneficiaries upon death for a 15-year period. The Company's net periodic benefit cost for this plan for the three months ended March 31, 2013 and 2012, was $1.9 million and $2.1 million, respectively.

In 2012, the Company modified health care coverage for certain retirees. Effective January 1, 2013, post-65 coverage is replaced by a fixed-dollar subsidy for retirees and spouses to be used to purchase individual insurance through an exchange.

Note 17 - Regulatory matters and revenues subject to refund

On September 26, 2012, Montana-Dakota filed an application with the MTPSC for a natural gas rate increase. Montana-Dakota requested a total increase of $3.5 million annually or approximately 5.9 percent above current rates. The requested increase includes the costs associated with the increased investment in facilities, including ongoing investment in new and replacement distribution facilities, the landfill gas production facility, a region operations building, automated meter reading and a new customer billing system. Montana-Dakota requested an interim increase, subject to refund, of $1.7 million or approximately 2.9 percent. On April 12, 2013, the MTPSC issued an interim order authorizing an interim increase of $850,000 annually to be effective with service rendered on or after April 15, 2013, subject to refund. A hearing scheduled for May 1, 2013, was postponed with no date currently set.

On December 21, 2012, Montana-Dakota filed an application with the SDPUC for a natural gas rate increase. Montana-Dakota requested a total increase of $1.5 million annually or approximately 3.3 percent above current rates. The requested increase includes the costs associated with the increased investment in facilities, including ongoing investment in new and replacement distribution facilities, the landfill gas production facility, an operations building, automated meter reading and a new customer billing system.

On February 11, 2013, Montana-Dakota filed an application with the NDPSC for approval of an environmental cost recovery rider for recovery of Montana-Dakota's share of the costs resulting from the environmental retrofit required to be installed at the Big Stone Station. The costs proposed to be recovered are associated with the ongoing construction costs for the installation of the BART air-quality control system. On February 27, 2013, the NDPSC suspended the filing pending further review.

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Note 18 - Contingencies

The Company is party to claims and lawsuits arising out of its business and that of its consolidated subsidiaries. The Company accrues a liability for those contingencies when the incurrence of a loss is probable and the amount can be reasonably estimated. If a range of amounts can be reasonably estimated and no amount within the range is a better estimate than any other amount, then the minimum of the range is accrued. The Company does not accrue liabilities when the likelihood that the liability has been incurred is probable but the amount cannot be reasonably estimated or when the liability is believed to be only reasonably possible or remote. For contingencies where an unfavorable outcome is probable or reasonably possible and which are material, the Company discloses the nature of the contingency and, where feasible, an estimate of the possible loss. The Company had accrued liabilities of $33.3 million, $70.7 million and $22.5 million for contingencies, including litigation and environmental matters, as of March 31, 2013 and 2012, and December 31, 2012, respectively, which includes amounts that may have been accrued for matters discussed in Litigation and Environmental matters within this note.

Litigation

Guarantee Obligation Under a Construction Contract Centennial guaranteed CEM's obligations under a construction contract with LPP for a 550-MW combined-cycle electric generating facility near Hobbs, New Mexico. Centennial Resources sold CEM in July 2007 to Bicent. In February 2009, Centennial received a Notice and Demand from LPP under the guarantee agreement alleging that CEM did not meet certain of its obligations under the construction contract and demanding that Centennial indemnify LPP against all losses, damages, claims, costs, charges and expenses arising from CEM's alleged failures. In December 2009, LPP submitted a demand for arbitration of its dispute with CEM to the American Arbitration Association seeking compensatory damages of $149.7 million. An arbitration award was issued January 13, 2012, awarding LPP $22.0 million. Centennial subsequently received a demand from LPP for payment of the arbitration award plus interest and attorneys' fees. An accrual related to the guarantee as a result of the arbitration award was recorded in discontinued operations on the Consolidated Statement of Income in the fourth quarter of 2011. CEM filed a petition with the New York Supreme Court to vacate the arbitration award in favor of LPP. On October 19, 2012, Centennial moved to intervene in the New York Supreme Court action to vacate the arbitration award and also filed a complaint with the New York Supreme Court seeking a declaration that LPP is not entitled to indemnification from Centennial under the guaranty for the arbitration award. The New York Supreme Court granted CEM's petition to vacate the arbitration award on November 20, 2012, and entered a written order to that effect on April 11, 2013. Due to the vacation of the arbitration award, the Company no longer believes the loss related to this matter to be probable and thus the liability that was previously recorded in 2011 was reversed in the fourth quarter of 2012. Centennial anticipates LPP will appeal the order. We believe that it is reasonably possible that a loss related to this matter could result if LPP is successful in its appeal, the arbitration award is affirmed and LPP continues to assert its demand against Centennial under the guarantee for payment of the arbitration award, attorneys' fees and interest. For more information regarding discontinued operations, see Note 9.

Construction MaterialsUntil the fall of 2011 when it discontinued active mining operations at the pit, JTL operated the Target Range Gravel Pit in Missoula County, Montana under a 1975 reclamation contract pursuant to the Montana Opencut Mining Act. In September 2009, the Montana DEQ sent a letter asserting JTL was in violation of the Montana Opencut Mining Act by conducting mining operations outside a permitted area. JTL filed a complaint in Montana First Judicial District Court in June 2010, seeking a declaratory order that the reclamation contract is a valid permit under the Montana Opencut Mining Act. The Montana DEQ filed an answer and counterclaim to the complaint in August 2011, alleging JTL was in violation of the Montana Opencut Mining Act and requesting imposition of penalties of not more than $3.7 million plus not more than $5,000 per day from the date of the counterclaim. The Company believes the operation of the Target Range Gravel Pit was conducted under a valid permit; however, the imposition of civil penalties is reasonably possible. The Company filed an application for amendment of its opencut mining permit and intends to resolve this matter through settlement or continuation of the Montana First Judicial District Court litigation.

Natural Gas Gathering Operations In January 2010, SourceGas filed an application with the Colorado State District Court to compel WBI Energy Midstream to arbitrate a dispute regarding operating pressures under a natural gas gathering contract on one of WBI Energy Midstream's pipeline gathering systems in Montana. WBI Energy Midstream resisted the application and sought a declaratory order interpreting the gathering contract. In May 2010, the Colorado State District Court granted the application and ordered WBI Energy Midstream into arbitration. An arbitration hearing was held in August 2010. In October 2010, the arbitration panel issued an award in favor of SourceGas for approximately $26.6 million. As a result, WBI Energy Midstream, which is included in the pipeline and energy services segment, recorded a $26.6 million charge ($16.5 million after tax) in the third quarter of 2010. On April 20, 2011, the Colorado State District Court confirmed the arbitration award as a court judgment. WBI Energy Midstream filed an appeal from the Colorado State District Court's order and judgment to the Colorado Court of Appeals. The Colorado Court of Appeals issued a decision on May 24, 2012, reversing the Colorado State District Court order compelling arbitration, vacating the final award and remanding the case to the Colorado State District Court to determine SourceGas's claims and WBI Energy Midstream's counterclaims. As a result of the Colorado Court of Appeals

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decision, in the second quarter of 2012, WBI Energy Midstream changed its estimated loss related to this matter. This resulted in a reduction of expense of $24.1 million ($15.0 million after tax). On August 2, 2012, SourceGas filed a petition for writ of certiorari with the Colorado Supreme Court for review of the Colorado Court of Appeals decision. WBI Energy Midstream anticipates that if the Colorado Supreme Court were to grant a writ of certiorari and remand the matter to the Colorado State District Court, SourceGas will assert claims similar to those asserted in the arbitration proceeding.

In a related matter, Omimex filed a complaint against WBI Energy Midstream in Montana Seventeenth Judicial District Court in July 2010 alleging WBI Energy Midstream breached a separate gathering contract with Omimex as a result of the increased operating pressures demanded by SourceGas on the same natural gas gathering system. In December 2011, Omimex filed an amended complaint alleging WBI Energy Midstream breached obligations to operate its gathering system as a common carrier under United States and Montana law. WBI Energy Midstream removed the action to the United States District Court for the District of Montana. Expert reports submitted by Omimex contended its damages as a result of the increased operating pressures were $16.1 million to $22.6 million, however, the experts have since revised their calculation of Omimex's damages to $1.0 million. The Company believes the claims asserted by Omimex are without merit and an award is not deemed probable. The Company intends to vigorously defend against the claims. A trial on the matter is scheduled for July 2013.

The Company also is involved in other legal actions in the ordinary course of its business. After taking into account liabilities accrued for the foregoing matters, management believes that the outcomes with respect to the above and other legal proceedings will not have a material effect upon the Company's financial position, results of operations or cash flows.

Environmental matters

Portland Harbor Site In December 2000, Knife River - Northwest was named by the EPA as a PRP in connection with the cleanup of a riverbed site adjacent to a commercial property site acquired by Knife River - Northwest from Georgia-Pacific West, Inc. in 1999. The riverbed site is part of the Portland, Oregon, Harbor Superfund Site. The EPA wants responsible parties to share in the cleanup of sediment contamination in the Willamette River. To date, costs of the overall remedial investigation and feasibility study of the harbor site are being recorded, and initially paid, through an administrative consent order by the LWG, a group of several entities, which does not include Knife River - Northwest or Georgia-Pacific West, Inc. Investigative costs are indicated to be in excess of $70 million. It is not possible to estimate the cost of a corrective action plan until the remedial investigation and feasibility study have been completed, the EPA has decided on a strategy and a ROD has been published. Corrective action will be taken after the development of a proposed plan and ROD on the harbor site is issued. Knife River - Northwest also received notice in January 2008 that the Portland Harbor Natural Resource Trustee Council intends to perform an injury assessment to natural resources resulting from the release of hazardous substances at the Harbor Superfund Site. The Portland Harbor Natural Resource Trustee Council indicates the injury determination is appropriate to facilitate early settlement of damages and restoration for natural resource injuries. It is not possible to estimate the costs of natural resource damages until an assessment is completed and allocations are undertaken.

Based upon a review of the Portland Harbor sediment contamination evaluation by the Oregon DEQ and other information available, Knife River - Northwest does not believe it is a Responsible Party. In addition, Knife River - Northwest has notified Georgia-Pacific West, Inc., that it intends to seek indemnity for liabilities incurred in relation to the above matters pursuant to the terms of their sale agreement. Knife River - Northwest has entered into an agreement tolling the statute of limitations in connection with the LWG's potential claim for contribution to the costs of the remedial investigation and feasibility study. By letter in March 2009, LWG stated its intent to file suit against Knife River - Northwest and others to recover LWG's investigation costs to the extent Knife River - Northwest cannot demonstrate its non-liability for the contamination or is unwilling to participate in an alternative dispute resolution process that has been established to address the matter. At this time, Knife River - Northwest has agreed to participate in the alternative dispute resolution process.

The Company believes it is not probable that it will incur any material environmental remediation costs or damages in relation to the above referenced administrative action.

Manufactured Gas Plant Sites There are three claims against Cascade for cleanup of environmental contamination at manufactured gas plant sites operated by Cascade's predecessors.

The first claim is for contamination at a site in Eugene, Oregon which was received in 1995. There are PRPs in addition to Cascade that may be liable for cleanup of the contamination. Some of these PRPs have shared in the investigation costs. It is expected that these and other PRPs will share in the cleanup costs. Several alternatives for cleanup have been identified, with preliminary cost estimates ranging from approximately $500,000 to $11.0 million. The Oregon DEQ is preparing a staff report which will recommend a cleanup alternative for the site. It is not known at this time what share of the cleanup costs will actually be borne by Cascade; however, Cascade anticipates its proportional share could be approximately 50 percent. Cascade

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has accrued $1.3 million for remediation of this site. In January 2013, the OPUC approved Cascade's application to defer environmental remediation costs at the Eugene site for a period of 12 months starting November 30, 2012.

The second claim is for contamination at a site in Bremerton, Washington which was received in 1997. A preliminary investigation has found soil and groundwater at the site contain contaminants requiring further investigation and cleanup. EPA conducted a Targeted Brownfields Assessment of the site and released a report summarizing the results of that assessment in August 2009. The assessment confirms that contaminants have affected soil and groundwater at the site, as well as sediments in the adjacent Port Washington Narrows. Alternative remediation options have been identified with preliminary cost estimates ranging from $340,000 to $6.4 million. Data developed through the assessment and previous investigations indicates the contamination likely derived from multiple, different sources and multiple current and former owners of properties and businesses in the vicinity of the site may be responsible for the contamination. In April 2010, the Washington Department of Ecology issued notice it considered Cascade a PRP for hazardous substances at the site. In May 2012, the EPA added the site to the National Priorities List. Cascade has entered into an administrative settlement agreement and consent order with the EPA regarding the scope and schedule for a remedial investigation and feasibility study for the site. Cascade has accrued $6.7 million for the remedial investigation and feasibility study and $6.4 million for remediation of this site. In April 2010, Cascade filed a petition with the WUTC for authority to defer the costs, which are included in other noncurrent assets, incurred in relation to the environmental remediation of this site until the next general rate case. The WUTC approved the petition in September 2010, subject to conditions set forth in the order.

The third claim is for contamination at a site in Bellingham, Washington. Cascade received notice from a party in May 2008 that Cascade may be a PRP, along with other parties, for contamination from a manufactured gas plant owned by Cascade and its predecessor from about 1946 to 1962. The notice indicates that current estimates to complete investigation and cleanup of the site exceed $8.0 million. Other PRPs have reached an agreed order and work plan with the Washington Department of Ecology for completion of a remedial investigation and feasibility study for the site. A report documenting the initial phase of the remedial investigation was completed in June 2011. There is currently not enough information available to estimate the potential liability to Cascade associated with this claim although Cascade believes its proportional share of any liability will be relatively small in comparison to other PRPs. The plant manufactured gas from coal between approximately 1890 and 1946. In 1946, shortly after Cascade's predecessor acquired the plant, it converted the plant to a propane-air gas facility. There are no documented wastes or by-products resulting from the mixing or distribution of propane-air gas.

Cascade has received notices from certain of its insurance carriers that they will participate in defense of Cascade for these contamination claims subject to full and complete reservations of rights and defenses to insurance coverage. To the extent these claims are not covered by insurance, Cascade will seek recovery through the OPUC and WUTC of remediation costs in its natural gas rates charged to customers. The accruals related to these matters are reflected in regulatory assets.

Halawa Quarry The State of Hawaii Department of Health issued a Notice of Violation to Hawaiian Cement dated August 31, 2012, alleging violations of Hawaii's Water Pollution statute at Hawaiian Cement's Halawa Quarry by failure to comply with the quarry's National Pollutant Discharge Elimination System permit by failing to design, construct and maintain a facility to contain or treat the volume of all process wastewater and storm water that would result from a 10-year, 24-hour rainfall event. The Notice of Violation also alleged Hawaiian Cement violated the quarry's permit by discharging pollution, including levels of pH and total suspended solids in excess of the permit limits, on three occasions in January, June and December 2011. The Notice of Violation sought development and implementation of corrective action plans and unspecified administrative penalties. Hawaiian Cement resolved the Notice of Violation through a negotiated settlement which included payment of a monetary penalty of $100,000 as well as development and implementation of corrective action plans, the final cost of which are not expected to be material.

Guarantees

Centennial guaranteed CEM's obligations under a construction contract. For more information, see Litigation in this note.

In connection with the sale of the Brazilian Transmission Lines, as discussed in Note 10, Centennial has agreed to guarantee payment of any indemnity obligations of certain of the Company's indirect wholly owned subsidiaries who are the sellers in three purchase and sale agreements for periods ranging up to 10 years from the date of sale. The guarantees were required by the buyers as a condition to the sale of the Brazilian Transmission Lines.

WBI Holdings has guaranteed certain of Fidelity's oil and natural gas swap and collar agreement obligations. There is no fixed maximum amount guaranteed in relation to the oil and natural gas swap and collar agreements as the amount of the obligation is dependent upon oil and natural gas commodity prices. The amount of hedging activity entered into by the subsidiary is limited by corporate policy. The guarantees of the oil and natural gas swap and collar agreements at March 31, 2013, expire in the years ranging from 2013 to 2015; however, Fidelity continues to enter into additional hedging activities and, as a result,

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WBI Holdings from time to time may issue additional guarantees on these hedging obligations. The amount outstanding by Fidelity was $4.5 million and was reflected on the Consolidated Balance Sheet at March 31, 2013. In the event Fidelity defaults under its obligations, WBI Holdings would be required to make payments under its guarantees.

Certain subsidiaries of the Company have outstanding guarantees to third parties that guarantee the performance of other subsidiaries of the Company. These guarantees are related to construction contracts, natural gas transportation and sales agreements, gathering contracts and certain other guarantees. At March 31, 2013, the fixed maximum amounts guaranteed under these agreements aggregated $74.6 million. The amounts of scheduled expiration of the maximum amounts guaranteed under these agreements aggregate $17.4 million in 2013; $38.4 million in 2014; $300,000 in 2015; $100,000 in 2016; $600,000 in 2018; $300,000 in 2019; $13.5 million, which is subject to expiration on a specified number of days after the receipt of written notice; and $4.0 million, which has no scheduled maturity date. The amount outstanding by subsidiaries of the Company under the above guarantees was $200,000 and was reflected on the Consolidated Balance Sheet at March 31, 2013. In the event of default under these guarantee obligations, the subsidiary issuing the guarantee for that particular obligation would be required to make payments under its guarantee.

Certain subsidiaries have outstanding letters of credit to third parties related to insurance policies and other agreements, some of which are guaranteed by other subsidiaries of the Company. At March 31, 2013, the fixed maximum amounts guaranteed under these letters of credit, aggregated $32.3 million. In 2013 and 2014, $3.3 million and $29.0 million, respectively, of letters of credit are scheduled to expire. There were no amounts outstanding under the above letters of credit at March 31, 2013.

WBI Holdings has an outstanding guarantee to WBI Energy Transmission. This guarantee is related to a natural gas transportation and storage agreement that guarantees the performance of Prairielands. At March 31, 2013, the fixed maximum amount guaranteed under this agreement was $5.0 million and is scheduled to expire in 2014. In the event of Prairielands' default in its payment obligations, WBI Holdings would be required to make payment under its guarantee. The amount outstanding by Prairielands under the above guarantee was $900,000. The amount outstanding under this guarantee was not reflected on the Consolidated Balance Sheet at March 31, 2013, because this intercompany transaction was eliminated in consolidation.

In addition, Centennial, Knife River and MDU Construction Services have issued guarantees to third parties related to the routine purchase of maintenance items, materials and lease obligations for which no fixed maximum amounts have been specified. These guarantees have no scheduled maturity date. In the event a subsidiary of the Company defaults under these obligations, Centennial, Knife River and MDU Construction Services would be required to make payments under these guarantees. Any amounts outstanding by subsidiaries of the Company for these guarantees were reflected on the Consolidated Balance Sheet at March 31, 2013.

In the normal course of business, Centennial has surety bonds related to construction contracts and reclamation obligations of its subsidiaries, as well as an arbitration award. In the event a subsidiary of Centennial does not fulfill a bonded obligation, Centennial would be responsible to the surety bond company for completion of the bonded contract or obligation. A large portion of the surety bonds is expected to expire within the next 12 months; however, Centennial will likely continue to enter into surety bonds for its subsidiaries in the future. As of March 31, 2013, approximately $639 million of surety bonds were outstanding, which were not reflected on the Consolidated Balance Sheet.

Variable interest entities

The Company evaluates its arrangements and contracts with other entities to determine if they are VIEs and if so, if the Company is the primary beneficiary. GAAP provides a framework for identifying VIEs and determining when a company should include the assets, liabilities, noncontrolling interest, and results of activities of a VIE in its consolidated financial statements.

A VIE should be consolidated if a party with an ownership, contractual, or other financial interest in the VIE (a variable interest holder) has the power to direct the VIE's most significant activities and the obligation to absorb losses or right to receive benefits of the VIE that could be significant to the VIE. A variable interest holder that consolidates the VIE is called the primary beneficiary. Upon consolidation, the primary beneficiary generally must initially record all of the VIE's assets, liabilities, and noncontrolling interests at fair value and subsequently account for the VIE as if it were consolidated.

The Company's evaluation of whether it qualifies as the primary beneficiary of a VIE is highly complex and involves significant judgments, estimates and assumptions and includes a qualitative analysis of the activities that most significantly impact the VIE's economic performance and whether the Company has the power to direct those activities, the design of the entity, the rights of the parties, and the purpose of the arrangement.

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Dakota Prairie Refining, LLCOn February 7, 2013, WBI Energy and Calumet formed a limited liability company, Dakota Prairie Refining, and entered into an operating agreement to develop, build and operate a diesel topping plant in southwestern North Dakota. WBI Energy and Calumet each have a fifty percent ownership interest in Dakota Prairie Refining. WBI Energy's and Calumet's capital commitments under the agreement are $150 million and $75 million, respectively. Dakota Prairie Refining entered into a term loan for project debt financing of $75 million on April 22, 2013. The agreement provides for allocation of profits and losses consistent with ownership interests; however, deductions attributable to project financing debt will be allocated to Calumet. Calumet's future cash distributions from Dakota Prairie Refining will be decreased by the principal and interest to be paid on the project debt, while the cash distributions to WBI Energy will not be decreased. Pursuant to the agreement, Centennial agreed to guarantee Dakota Prairie Refining's obligation under the term loan. For more information on the guarantee, see Note 19.

Dakota Prairie Refining has been determined to be a VIE, and the Company has determined that it is the primary beneficiary as it has an obligation to absorb losses that could be potentially significant to the VIE through WBI Energy's equity investment and Centennial's guarantee of the third-party term loan. Accordingly, the Company consolidates Dakota Prairie Refining in its financial statements and records a noncontrolling interest for Calumet's ownership interest.

Construction on the diesel topping plant began in early 2013 and the plant is not yet operational. The assets of Dakota Prairie Refining shall be used solely for the benefit of Dakota Prairie Refining. The total assets and liabilities of Dakota Prairie Refining reflected on the Company's Consolidated Balance Sheets were as follows:

	March 31, 2013
	(In thousands)
ASSETS
Current assets:
Cash and cash equivalents	$	10,793
Total current assets	10,793
Net property, plant and equipment	27,356
Total assets	$	38,149
LIABILITIES
Current liabilities:
Accounts payable	$	10,948
Total liabilities	$	10,948

Fuel Contract On October 10, 2012, the Coyote Station entered into a new coal supply agreement with Coyote Creek that will replace a coal supply agreement that expires in May 2016. The new agreement provides for the purchase of coal necessary to supply the coal requirements of the Coyote Station, of which the Company is a 25.0 percent owner, for the period May 2016 through December 2040.

The new coal supply agreement creates a variable interest in Coyote Creek due to the transfer of all operating and economic risk to the Coyote Station owners as the agreement is structured so the price of the coal will cover all costs of operations as well as future reclamation costs. The Coyote Station owners are also providing a guarantee of the value of the assets of Coyote Creek as they would be required to buy the assets at book value should they terminate the contract prior to the end of the contract term and are providing a guarantee of the value of the equity of Coyote Creek in that they are required to buy the entity at the end of the contract term at equity value. Although the Company has determined that Coyote Creek is a VIE, the Company has concluded that it is not the primary beneficiary of Coyote Creek because the authority to direct the activities of the entity is shared by the four unrelated owners of the Coyote Station with no primary beneficiary existing. As a result, Coyote Creek is not required to be consolidated in the Company's financial statements.

At March 31, 2013, Coyote Creek was not yet operational. The assets and liabilities of Coyote Creek and exposure to loss as a result of the Company's involvement with the VIE at March 31, 2013, is not material.

Note 19 - Subsequent event

In connection with the Company's variable interest in Dakota Prairie Refining, as discussed in Note 18, Centennial has agreed to guarantee repayment of the Dakota Prairie Refining term loan, which was entered into on April 22, 2013. The term loan maturity dates range from April 2018 to April 2023.

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ITEM 2. MANAGEMENT'S DISCUSSION AND ANALYSIS OF FINANCIALCONDITION AND RESULTS OF OPERATIONS

OVERVIEW

The Company's strategy is to apply its expertise in energy and transportation infrastructure industries to increase market share, increase profitability and enhance shareholder value through:

• Organic growth as well as a continued disciplined approach to the acquisition of well-managed companies and properties

• The elimination of system-wide cost redundancies through increased focus on integration of operations and standardization and consolidation of various support services and functions across companies within the organization

• The development of projects that are accretive to earnings per share and return on invested capital

The Company has capabilities to fund its growth and operations through various sources, including internally generated funds, commercial paper facilities, revolving credit facilities and the issuance from time to time of debt and equity securities. For more information on the Company's net capital expenditures, see Liquidity and Capital Commitments.

The key strategies for each of the Company's business segments and certain related business challenges are summarized below. For a summary of the Company's business segments, see Note 15.

Key Strategies and Challenges

Electric and Natural Gas Distribution

Strategy Provide competitively priced energy and related services to customers. The electric and natural gas distribution segments continually seek opportunities to retain, grow and expand their customer base through extensions of existing operations, including building and upgrading electric generation and transmission and natural gas systems, and through selected acquisitions of companies and properties at prices that will provide stable cash flows and an opportunity for the Company to earn a competitive return on investment.

Challenges Both segments are subject to extensive regulation in the state jurisdictions where they conduct operations with respect to costs and permitted returns on investment as well as subject to certain operational, system integrity and environmental regulations. These regulations can require substantial investment to upgrade facilities. The ability of these segments to grow through acquisitions is subject to significant competition. In addition, the ability of both segments to grow service territory and customer base is affected by the economic environment of the markets served and competition from other energy providers and fuels. The construction of any new electric generating facilities, transmission lines and other service facilities are subject to increasing cost and lead time, extensive permitting procedures, and federal and state legislative and regulatory initiatives, which will necessitate increases in electric energy prices. Legislative and regulatory initiatives to increase renewable energy resources and reduce GHG emissions could impact the price and demand for electricity and natural gas.

Pipeline and Energy Services

Strategy Utilize the segment's existing expertise in energy infrastructure and related services to increase market share and profitability through optimization of existing operations, internal growth, and acquisitions of energy-related assets and companies. Incremental and new growth opportunities include: access to new energy sources for storage, gathering and transportation services; expansion of existing gathering, transmission and storage facilities; incremental expansion of pipeline capacity; expansion of midstream business to include liquid pipelines and processing/refining activities; and expansion of related energy services.

Challenges Challenges for this segment include: energy price volatility; natural gas basis differentials; environmental and regulatory requirements; recruitment and retention of a skilled workforce; and competition from other pipeline and energy services companies.

Exploration and Production

Strategy Apply technology and utilize existing exploration and production expertise, with a focus on operated properties, to increase production and reserves from existing leaseholds, and to seek additional reserves and production opportunities both in new and existing areas to further expand the segment's asset base. By optimizing existing operations and taking advantage of new and incremental growth opportunities, this segment is focused on balancing the oil and natural gas commodity mix to maximize profitability with its goal to add value by increasing both reserves and production over the long term so as to generate competitive returns on investment.

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Challenges Volatility in natural gas and oil prices; timely receipt of necessary permits and approvals; environmental and regulatory requirements; recruitment and retention of a skilled workforce; availability of drilling rigs, materials, auxiliary equipment and industry-related field services; inflationary pressure on development and operating costs; and competition from other exploration and production companies are ongoing challenges for this segment.

Construction Materials and Contracting

Strategy Focus on high-growth strategic markets located near major transportation corridors and desirable mid-sized metropolitan areas; strengthen long-term, strategic aggregate reserve position through purchase and/or lease opportunities; enhance profitability through cost containment, margin discipline and vertical integration of the segment's operations; develop and recruit talented employees; and continue growth through organic and acquisition opportunities. Vertical integration allows the segment to manage operations from aggregate mining to final lay-down of concrete and asphalt, with control of and access to permitted aggregate reserves being significant. A key element of the Company's long-term strategy for this business is to further expand its market presence in the higher-margin materials business (rock, sand, gravel, liquid asphalt, asphalt concrete, ready-mixed concrete and related products), complementing and expanding on the Company's expertise.

Challenges Recruitment and retention of key personnel and volatility in the cost of raw materials such as diesel, gasoline, liquid asphalt, cement and steel, continue to be a concern. This business unit expects to continue cost containment efforts, positioning its operations for the resurgence in the private market, while continuing the emphasis on industrial, energy and public works projects.

Construction Services

Strategy Provide a competitive return on investment while operating in a competitive industry by: building new and strengthening existing customer relationships; effectively controlling costs; retaining, developing and recruiting talented employees; focusing our efforts on projects that will permit higher margins while properly managing risk.

Challenges This segment operates in highly competitive markets with many jobs subject to competitive bidding. Maintenance of effective operational and cost controls, retention of key personnel, managing through downturns in the economy and effective management of working capital are ongoing challenges.

For more information on the risks and challenges the Company faces as it pursues its growth strategies and other factors that should be considered for a better understanding of the Company's financial condition, see Item 1A - Risk Factors, as well as Part I, Item 1A - Risk Factors in the 2012 Annual Report. For more information on each segment's key growth strategies, projections and certain assumptions, see Prospective Information. For information pertinent to various commitments and contingencies, see Notes to Consolidated Financial Statements.

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Earnings Overview

The following table summarizes the contribution to consolidated earnings by each of the Company's businesses.

	Three Months Ended
	March 31,
	2013			2012
(Dollars in millions, where applicable)
Electric	$	9.8		$	7.5
Natural gas distribution	32.5			25.5
Pipeline and energy services	2.3			2.8
Exploration and production	20.3			12.9
Construction materials and contracting	(20.6		)	(24.9		)
Construction services	11.7			11.4
Other	.4			.5
Earnings before discontinued operations	56.4			35.7
Loss from discontinued operations, net of tax	(.1		)	(.1		)
Earnings on common stock	$	56.3		$	35.6
Earnings per common share - basic:
Earnings before discontinued operations	$	.30		$	.19
Discontinued operations, net of tax	—			—
Earnings per common share - basic	$	.30		$	.19
Earnings per common share - diluted:
Earnings before discontinued operations	$	.30		$	.19
Discontinued operations, net of tax	—			—
Earnings per common share - diluted	$	.30		$	.19

Three Months Ended March 31, 2013 and 2012 Consolidated earnings for the quarter ended March 31, 2013, increased $20.7 million (58 percent) from the comparable prior period largely due to:

• Increased oil production, partially offset by decreased natural gas production and higher depreciation, depletion and amortization expense at the exploration and production business

• Increased retail sales volumes and a gain on the sale of a nonregulated appliance service and repair business at the natural gas distribution business

• Higher aggregate, asphalt and construction margins at the construction materials and contracting business

• Increased retail sales volumes at the electric business

FINANCIAL AND OPERATING DATA

Below are key financial and operating data for each of the Company's businesses.

Electric

	Three Months Ended
	March 31,
	2013		2012
(Dollars in millions, where applicable)
Operating revenues	$	64.6	$	58.0
Operating expenses:
Fuel and purchased power	21.6		18.4
Operation and maintenance	16.4		16.2
Depreciation, depletion and amortization	8.6		8.1
Taxes, other than income	2.9		2.7
	49.5		45.4
Operating income	15.1		12.6
Earnings	$	9.8	$	7.5
Retail sales (million kWh)	842.6		769.7
Sales for resale (million kWh)	7.4		1.9
Average cost of fuel and purchased power per kWh	$	.024	$	.022

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Three Months Ended March 31, 2013 and 2012 Electric earnings increased $2.3 million (30 percent) due to:

• Increased retail sales volumes of 9 percent, primarily to residential and small commercial and industrial customers due to colder weather than last year, as well as increased customer growth

• Higher other income of $300,000 (after tax), largely allowance for funds used during construction

Partially offsetting these increases was higher depreciation, depletion and amortization expense of $300,000 (after tax), including the effects of higher property, plant and equipment balances.

Natural Gas Distribution

	Three Months Ended
	March 31,
	2013			2012
(Dollars in millions, where applicable)
Operating revenues	$	331.7		$	307.9
Operating expenses:
Purchased natural gas sold	213.4			199.3
Operation and maintenance	34.1			35.3
Depreciation, depletion and amortization	12.2			11.2
Taxes, other than income	16.3			16.1
	276.0			261.9
Operating income	55.7			46.0
Earnings	$	32.5		$	25.5
Volumes (MMdk):
Sales	44.9			38.7
Transportation	38.2			37.9
Total throughput	83.1			76.6
Degree days (% of normal)*
Montana-Dakota/Great Plains	98		%	77		%
Cascade	99		%	101		%
Intermountain	114		%	93		%
Average cost of natural gas, including transportation, per dk	$	4.75		$	5.15
* Degree days are a measure of the daily temperature-related demand for energy for heating.

Three Months Ended March 31, 2013 and 2012 Earnings at the natural gas distribution business increased $7.0 million (27 percent) due to:

• Increased retail sales volumes of 16 percent, largely resulting from colder weather than last year, partially offset by weather normalization in certain jurisdictions

• A $2.9 million (after tax) gain on the sale of Montana-Dakota's nonregulated appliance service and repair business

• Lower net interest expense of $500,000 (after tax), primarily due to lower average borrowings

Partially offsetting these increases was increased depreciation, depletion and amortization expense of $600,000 (after tax), including the effects of higher property, plant and equipment balances.

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Pipeline and Energy Services

	Three Months Ended
	March 31,
	2013			2012
	(Dollars in millions)
Operating revenues	$	46.4		$	49.6
Operating expenses:
Purchased natural gas sold	12.8			16.0
Operation and maintenance	17.2			17.1
Depreciation, depletion and amortization	7.2			6.2
Taxes, other than income	3.4			3.5
	40.6			42.8
Operating income	5.8			6.8
Earnings	$	2.3		$	2.8
Transportation volumes (MMdk)	36.8			32.0
Natural gas gathering volumes (MMdk)	9.9			14.2
Customer natural gas storage balance (MMdk):
Beginning of period	43.7			36.0
Net withdrawal	(19.0		)	(8.7		)
End of period	24.7			27.3

Three Months Ended March 31, 2013 and 2012 Pipeline and energy services earnings decreased $500,000 (16 percent) due to lower earnings of $1.6 million (after tax) resulting from lower natural gas gathering volumes from existing operations, largely resulting from customers experiencing production curtailments, normal declines and deferral of natural gas development activity. This decrease was partially offset by higher oil and natural gas gathering and processing volumes from a May 2012 acquisition.

Results also reflect lower operating revenues and lower purchased natural gas sold, both related to lower natural gas sales volumes.

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Exploration and Production

	Three Months Ended
	March 31,
	2013		2012
(Dollars in millions, where applicable)
Operating revenues:
Oil	$	97.8	$	63.7
NGL	7.5		9.7
Natural gas	19.9		26.4
	125.2		99.8
Operating expenses:
Operation and maintenance:
Lease operating costs	20.8		18.5
Gathering and transportation	4.3		4.3
Other	10.2		9.2
Depreciation, depletion and amortization	43.1		36.8
Taxes, other than income:
Production and property taxes	11.6		9.5
Other	.3		.4
	90.3		78.7
Operating income	34.9		21.1
Earnings	$	20.3	$	12.9
Production:
Oil (MBbls)	1,118		767
NGL (MBbls)	201		190
Natural gas (MMcf)	6,713		10,047
Total production (MBOE)	2,438		2,632
Average realized prices (including hedges):
Oil (per Bbl)	$	87.42	$	83.14
NGL (per Bbl)	$	37.33	$	50.85
Natural gas (per Mcf)	$	2.97	$	2.63
Average realized prices (excluding hedges):
Oil (per Bbl)	$	89.44	$	93.01
NGL (per Bbl)	$	37.33	$	50.85
Natural gas (per Mcf)	$	2.86	$	1.94
Average depreciation, depletion and amortization rate, per BOE	$	16.90	$	13.32
Production costs, including taxes, per BOE:
Lease operating costs	$	8.54	$	7.02
Gathering and transportation	1.76		1.63
Production and property taxes	4.74		3.62
	$	15.04	$	12.27

Three Months Ended March 31, 2013 and 2012 Exploration and production earnings increased $7.4 million (57 percent) due to:

• Increased oil production of 46 percent, primarily related to drilling activity in the Bakken area, as well as the Paradox Basin

• Higher average realized natural gas prices of 13 percent

• Higher average realized oil prices of 5 percent

Partially offsetting these increases were:

• Decreased natural gas production of 33 percent, largely related to production curtailments, normal declines and deferral of certain natural gas development activity

• Higher depreciation, depletion and amortization expense of $4.0 million (after tax) due to higher depletion rates, partially offset by lower volumes

• Lower average realized NGL prices of 27 percent

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• Increased lease operating expenses of $1.5 million (after tax), largely related to higher costs in the Bakken area resulting from increased production volumes, partially offset by lower costs at certain natural gas properties where curtailments of production have occurred

• Higher production taxes of $1.3 million (after tax), primarily resulting from higher revenues

• Higher net interest expense of $1.0 million (after tax), primarily due to lower capitalized interest and higher average borrowings, partially offset by lower effective interest rates

Construction Materials and Contracting

	Three Months Ended
	March 31,
	2013			2012
	(Dollars in millions)
Operating revenues	$	166.3		$	149.4
Operating expenses:
Operation and maintenance	166.6			157.0
Depreciation, depletion and amortization	19.0			19.8
Taxes, other than income	8.5			8.0
	194.1			184.8
Operating loss	(27.8		)	(35.4		)
Loss	$	(20.6	)	$	(24.9	)
Sales (000's):
Aggregates (tons)	2,958			2,493
Asphalt (tons)	149			100
Ready-mixed concrete (cubic yards)	480			468

Three Months Ended March 31, 2013 and 2012 Construction materials and contracting experienced a seasonal first quarter loss of $20.6 million compared to a loss of $24.9 million a year ago. The decreased seasonal loss was the result of:

• Higher earnings of $2.8 million (after tax) resulting from higher aggregate and asphalt margins, primarily due to lower costs

• Increased construction margins of $1.0 million (after tax)

• Lower selling, general and administrative costs of $700,000 (after tax)

Partially offsetting these increases was higher interest expense of $500,000 (after tax) resulting from higher average interest rates, as well as higher average borrowings.

Construction Services

	Three Months Ended
	March 31,
	2013		2012
	(In millions)
Operating revenues	$	231.4	$	218.2
Operating expenses:
Operation and maintenance	198.4		187.9
Depreciation, depletion and amortization	3.0		2.8
Taxes, other than income	9.6		7.8
	211.0		198.5
Operating income	20.4		19.7
Earnings	$	11.7	$	11.4

Three Months Ended March 31, 2013 and 2012 Construction services earnings increased $300,000 (2 percent), primarily due to higher equipment sales and rental margins, partially offset by lower margins in the Central and Mountain regions.

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Other and Intersegment Transactions

Amounts presented in the preceding tables will not agree with the Consolidated Statements of Income due to the Company's other operations and the elimination of intersegment transactions. The amounts relating to these items are as follows:

	Three Months Ended
	March 31,
	2013		2012
	(In millions)
Other:
Operating revenues	$	2.2	$	2.1
Operation and maintenance	1.3		1.3
Depreciation, depletion and amortization	.5		.5
Intersegment transactions:
Operating revenues	$	36.2	$	32.2
Purchased natural gas sold	27.0		29.9
Operation and maintenance	9.2		2.3

For more information on intersegment eliminations, see Note 15.

PROSPECTIVE INFORMATION

The following information highlights the key growth strategies, projections and certain assumptions for the Company and its subsidiaries and other matters for certain of the Company's businesses. Many of these highlighted points are "forward-looking statements." There is no assurance that the Company's projections, including estimates for growth and changes in earnings, will in fact be achieved. Please refer to assumptions contained in this section, as well as the various important factors listed in Part II, Item 1A - Risk Factors, as well as Part I, Item 1A - Risk Factors in the 2012 Annual Report. Changes in such assumptions and factors could cause actual future results to differ materially from the Company's growth and earnings projections.

MDU Resources Group, Inc.

• Earnings per common share for 2013, diluted, are projected in the range of $1.30 to $1.40. The Company expects the approximate percentage of 2013 earnings per common share by quarter to be:

◦ Second quarter – 20 percent

◦ Third quarter – 30 percent

◦ Fourth quarter – 25 percent

• The Company's long-term compound annual growth goals on earnings per share from operations are in the range of 7 to 10 percent.

• The Company continually seeks opportunities to expand through organic growth and strategic acquisitions.

• The Company focuses on creating value through vertical integration between its business units. For example, the pipeline and energy services business' partially owned diesel topping plant under construction in the Bakken region, will have the construction materials and services business involved in constructing the facility, the exploration and production business supplying production to the plant, the pipeline transporting natural gas to the plant, and the utility supplying electricity.

Electric and natural gas distribution

• The Company filed an application February 11, 2013, with the NDPSC for approval of an environmental cost recovery rider related to costs for the required environmental retrofit at the Big Stone Station, as discussed in Note 17.

• The Company filed an application December 21, 2012, with the SDPUC for a natural gas rate increase, as discussed in Note 17.

• The Company filed an application September 26, 2012, with the MTPSC for a natural gas rate increase, as discussed in Note 17.

• The EPA approved the South Dakota Regional Haze Program, which requires the Big Stone Station to install and operate a BART air-quality control system to reduce emissions of particulate matter, sulfur dioxide and nitrogen oxides. The

36

Company's share of the cost for the installation is estimated at $100 million and is expected to be complete in 2015. The NDPSC has approved advance determination of prudence for recovery of costs related to this system in electric rates charged to customers.

• The Company plans to construct and operate an 88-MW simple-cycle natural gas turbine and associated facilities, with an estimated project cost of $86 million and a projected in-service date in late 2014. It will be located on owned property that is adjacent to the Company's Heskett Generating Station near Mandan, North Dakota. The capacity is necessary to meet the requirements of the Company's integrated electric system customers and will be a partial replacement for third-party contract capacity expiring in 2015. Advance determination of prudence and a Certificate of Public Convenience and Necessity have been received from the NDPSC.

• Planned investments are approximately $75 million for 2013 to serve the growing electric and natural gas customer base associated with the Bakken oil development in western North Dakota and eastern Montana.

• Rate base growth is projected to be approximately 6 percent compounded annually over the next five years.

• The Company is analyzing potential projects for accommodating load growth in its industrial and agricultural sectors, with company- and customer-owned pipeline facilities designed to serve existing facilities served by fuel oil or propane, and to serve new customers. The Company is currently engaged in a 30-mile natural gas line project into the Hanford Nuclear Site in Washington.

• The Company is involved with a number of pipeline projects to enhance the reliability and deliverability of its system in the Pacific Northwest and Idaho.

• Opportunities associated with the potential development of high-voltage transmission lines and system enhancements targeted toward delivery of energy to major market areas are being pursued.

• On March 13, 2013, the OPUC approved an extension of Cascade's decoupling mechanism, as reported in Items 1 and 2 - Business and Properties - General in the 2012 Annual Report, until December 31, 2015.

Pipeline and energy services

• The Company has formed a limited liability company with Calumet, called Dakota Prairie Refining, to develop, build and operate a 20,000 barrel-per-day diesel topping plant in southwestern North Dakota. Construction began on the facility in late March 2013 and when complete will process Bakken crude and market the diesel within the Bakken region. Total project costs are estimated to be approximately $300 million, with a projected in-service date in late 2014.

• In May 2012, the Company purchased a 50 percent undivided interest in Whiting Oil and Gas Corporation's Pronghorn natural gas and oil midstream assets near Belfield, North Dakota, in the Bakken area. The Company invested approximately $100 million in 2012 including the purchase price. The Belfield natural gas processing plant has an inlet processing capacity of 35 MMcf per day. The Company will receive a full year of benefit from this acquisition in 2013.

• In August 2012, the Company placed in service approximately 13 miles of high-pressure transmission pipeline from the Stateline processing facilities in northwestern North Dakota to deliver natural gas into the Northern Border Pipeline, which is expected to result in increased transportation volumes for 2013.

• Dry natural gas gathering volumes are expected to be lower in 2013 compared to 2012 because of curtailments and the deferral of development activity by producers.

• The Company recently reached an agreement to construct a pipeline in 2014 to connect the planned Garden Creek II gas processing plant in northwestern North Dakota to deliver natural gas into the Northern Border Pipeline.

• The Company continues to pursue expansion of facilities and services offered to customers. Energy development within its geographic region, which includes portions of Colorado, Montana, North Dakota and Wyoming, is expanding, most notably the Bakken area of North Dakota and eastern Montana. The Company owns an extensive natural gas pipeline system in the Bakken area. Ongoing energy development is expected to have many direct and indirect benefits to this business.

Exploration and production

• The Company expects to spend approximately $400 million in capital expenditures in 2013. With improving well cost efficiencies and having essentially completed the extensive 2012 exploration program, the capital program will focus on

37

growth projects where the Company expects higher returns, namely the Bakken, Paradox Basin and Texas, as described below. Follow-up on development activity of the 2012 exploration program (beyond the activity in the Paradox) could take place in late 2013 or early 2014 depending upon the economic competitiveness of those plays once they are fully appraised. The 2013 planned capital expenditure total does not include potential acquisitions.

• For 2013, the Company expects a 25 to 30 percent increase in oil production, a flat to slight increase in NGL production, and a 15 to 25 percent decrease in natural gas production. The majority of the capital program is focused on growing oil production considering current relative commodity prices. The Company expects to return to some natural gas development when the commodity prices make it more profitable to do so.

• The Company has a total of five drilling rigs deployed on its acreage in the Bakken, Paradox and Texas areas.

• Bakken areas

◦ The Company owns a total of approximately 127,000 net acres of leaseholds in Mountrail, Stark and Richland counties.

◦ Capital expenditures are expected to total approximately $200 million in 2013. The Company is currently operating three rigs in the play; with improving drilling efficiencies and other factors that number could vary across the year from two to three rigs.

• Paradox Basin, Utah

◦ The Company has increased its holding to approximately 92,000 net acres and also has an option to lease another 20,000 acres.

◦ The Cane Creek 18-1 well was brought on line in April 2013 and is currently flowing at approximately 1,000 BOPD with a flowing tube pressure of approximately 2,000 psi.

◦ The Company is continuing to proceed systematically in this play, and anticipates spending $70 million of capital expenditures in 2013. As the play is fully understood, the opportunity to ramp up to full-scale development could increase the planned investment. At this point, the potential appears very significant.

◦ Approximately 50 to 75 future net locations have been identified. Estimated gross ultimate recovery rates per well range from 250,000 to 1 million Bbls.

• Texas

◦ The Company is targeting areas that have the potential for higher liquids content with approximately $40 million of capital planned for this year.

• Other opportunities

◦ The Company completed drilling a horizontal well during April 2013 in Sioux County, Nebraska. Completion operations will be conducted during the second quarter of 2013. Upon evaluation of this well, the Company may exercise an option to purchase a 65 percent working interest in approximately 79,000 gross acres.

◦ The remaining forecasted 2013 capital has been allocated to other operated and non-operated opportunities.

• Earnings guidance reflects estimated average NYMEX index prices for May through December in the ranges of $85.00 to $95.00 per Bbl of crude oil, and $3.75 to $4.25 per Mcf of natural gas. Estimated prices for NGL are in the range of $30.00 to $45.00 per Bbl.

• For the last nine months of 2013, the Company has hedged 9,000 BOPD utilizing swaps and costless collars with a weighted average price of $98.67 and $92.50/$107.03 (floor/ceiling) respectively, and 50,000 MMBtu of natural gas per day, with an additional 10,000 MMBtu per day for September through December, utilizing swaps at a weighted average price of $3.76. 

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• For the first six months of 2014, the Company has hedged 2,000 BOPD utilizing swaps with a weighted average price of $95.075, and for 2014 the Company has hedged 20,000 MMBtu of natural gas per day utilizing swaps at a weighted average price of $4.13.

• For 2015, the Company has hedged 10,000 MMBtu of natural gas per day utilizing a swap at $4.2825.

• The hedges that are in place as of April 30, 2013, are summarized in the following chart:

Commodity	Type	Index	Period Outstanding	Forward Notional Volume (Bbl/MMBtu)	Price (Per Bbl/MMBtu)
Crude Oil	Collar	NYMEX	4/13 - 12/13	275,000	$95.00-$117.00
Crude Oil	Collar	NYMEX	4/13 - 12/13	275,000	$90.00-$97.05
Crude Oil	Swap	NYMEX	4/13 - 12/13	137,500	$95.00
Crude Oil	Swap	NYMEX	4/13 - 12/13	137,500	$95.30
Crude Oil	Swap	NYMEX	4/13 - 12/13	137,500	$100.00
Crude Oil	Swap	NYMEX	4/13 - 12/13	137,500	$100.02
Crude Oil	Swap	NYMEX	4/13 - 12/13	275,000	$102.00
Crude Oil	Swap	NYMEX	4/13 - 12/13	275,000	$104.00
Crude Oil	Swap	NYMEX	4/13 - 12/13	275,000	$98.00
Crude Oil	Swap	NYMEX	4/13 - 12/13	137,500	$94.15
Crude Oil	Swap	NYMEX	4/13 - 12/13	137,500	$94.00
Crude Oil	Swap	NYMEX	4/13 - 12/13	275,000	$97.45
Crude Oil	Swap	NYMEX	1/14 - 6/14	181,000	$95.15
Crude Oil	Swap	NYMEX	1/14 - 6/14	181,000	$95.00
Natural Gas	Swap	NYMEX	4/13 - 12/13	2,750,000	$3.76
Natural Gas	Swap	NYMEX	4/13 - 12/13	2,750,000	$3.90
Natural Gas	Swap	NYMEX	4/13 - 12/13	2,750,000	$4.00
Natural Gas	Swap	NYMEX	4/13 - 12/13	5,500,000	$3.50
Natural Gas	Swap	NYMEX	9/13 - 12/14	4,870,000	$4.13
Natural Gas	Swap	NYMEX	1/14 - 12/14	3,650,000	$4.13
Natural Gas	Swap	NYMEX	1/15 - 12/15	3,650,000	$4.2825

• Effective April 1, 2013, the Company has elected to discontinue hedge accounting, as discussed in Note 12.

Construction materials and contracting

• Approximate work backlog as of March 31, 2013, was $589 million, compared to $532 million a year ago. Private work represents 12 percent of construction backlog, up from 9 percent a year ago. Public work represents 88 percent of backlog. The backlog includes a variety of projects such as highway paving projects, airports, bridge work, reclamation and harbor expansions.

• The Company's approximate backlog in North Dakota was $67 million, compared to approximately $40 million a year ago.

• Projected revenues included in the Company's 2013 earnings guidance are in the range of $1.5 billion to $1.7 billion.

• The Company anticipates margins in 2013 to be higher compared to 2012.

• The Company continues to pursue opportunities for expansion in energy projects such as refineries, transmission, wind towers and geothermal. Initiatives are aimed at capturing additional market share and expanding into new markets.

• As the country's fifth-largest sand and gravel producer, the Company will continue to strategically manage its 1.1 billion tons of aggregate reserves in all its markets, as well as take further advantage of being vertically integrated.

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• Of the four labor contracts that Knife River was negotiating, as reported in Items 1 and 2 - Business and Properties - General in the 2012 Annual Report, three have been ratified. The one remaining contract is still in negotiations.

Construction services

• Approximate work backlog as of March 31, 2013, was $465 million, compared to $333 million a year ago. The backlog includes a variety of projects such as substation and line construction, solar and other commercial, institutional and industrial projects including refinery work.

• Projected revenues included in the Company's 2013 earnings guidance are in the range of $900 million to $1 billion.

• The Company anticipates margins in 2013 to be lower compared to 2012.

• The Company continues to pursue opportunities for expansion in energy projects such as refineries, transmission, substations, utility services, as well as solar. Initiatives are aimed at capturing additional market share and expanding into new markets.

NEW ACCOUNTING STANDARDS

For information regarding new accounting standards, see Note 7, which is incorporated by reference.

CRITICAL ACCOUNTING POLICIES INVOLVING SIGNIFICANT ESTIMATES

The Company's critical accounting policies involving significant estimates include impairment testing of oil and natural gas properties, impairment testing of long-lived assets and intangibles, revenue recognition, pension and other postretirement benefits, and income taxes. There were no material changes in the Company's critical accounting policies involving significant estimates from those reported in the 2012 Annual Report. For more information on critical accounting policies involving significant estimates, see Part II, Item 7 in the 2012 Annual Report.

LIQUIDITY AND CAPITAL COMMITMENTS

At March 31, 2013, the Company had cash and cash equivalents of $74.1 million and available capacity of $401.5 million under the outstanding credit facilities of the Company and its subsidiaries. The Company expects to meet its obligations for debt maturing within one year from various sources, including internally generated funds; the Company's credit facilities, as described later; and through the issuance of long-term debt and the Company's equity securities.

Cash flows

Operating activitiesThe changes in cash flows from operating activities generally follow the results of operations as discussed in Financial and Operating Data and also are affected by changes in working capital.

Cash flows provided by operating activities in the first three months of 2013 increased $11.9 million from the comparable period in 2012. Excluding working capital requirements, the Company experienced increased cash flows from operating activities primarily at the exploration and production business and electric and natural gas distribution businesses, as well as higher deferred income taxes of $12.1 million. The increase in cash flows provided by operating activities was partially offset by higher working capital requirements of $33.6 million.

Investing activities Cash flows used in investing activities in the first three months of 2013 increased $14.4 million from the comparable period in 2012. The increase was primarily due to higher ongoing capital expenditures of $14.0 million, including electric generation projects at the electric business, as well as higher capital expenditures at the natural gas distribution business.

Financing activities Cash flows provided by financing activities in the first three months of 2013 increased $99.0 million from the comparable period in 2012, primarily due to higher issuance of long-term debt of $112.0 million, largely due to the issuance of $100.0 million of Senior Notes in February 2013, as discussed later; as well as lower dividends paid of $31.6 million resulting from the Company accelerating the payment date for the quarterly common stock dividend from January 1, 2013 to December 31, 2012. Partially offsetting the increase in cash flows provided by financing activities was higher repayment of long-term debt of $58.8 million.

Defined benefit pension plans

There were no material changes to the Company's qualified noncontributory defined benefit pension plans from those reported in the 2012 Annual Report. For more information, see Note 16 and Part II, Item 7 in the 2012 Annual Report.

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Capital expenditures

Net capital expenditures for the first three months of 2013 were $198.7 million and are estimated to be approximately $860 million (excluding noncontrolling interest capital expenditures) for 2013. Estimated capital expenditures include:

• System upgrades

• Routine replacements

• Service extensions

• Routine equipment maintenance and replacements

• Buildings, land and building improvements

• Pipeline, gathering and other midstream projects

• Further development of existing properties, acquisition of additional leasehold acreage and exploratory drilling at the exploration and production segment

• Power generation and transmission opportunities, including certain costs for additional electric generating capacity

• Environmental upgrades

• The diesel topping plant at the pipeline and energy services segment

• Other growth opportunities

The Company continues to evaluate potential future acquisitions and other growth opportunities; however, they are dependent upon the availability of economic opportunities and, as a result, capital expenditures may vary significantly from the estimated 2013 capital expenditures referred to previously. The Company expects the 2013 estimated capital expenditures to be funded by various sources, including internally generated funds; the Company's credit facilities, as described later; and through the issuance of long-term debt and the Company's equity securities.

Capital resources

Certain debt instruments of the Company and its subsidiaries, including those discussed later, contain restrictive covenants and cross-default provisions. In order to borrow under the respective credit agreements, the Company and its subsidiaries must be in compliance with the applicable covenants and certain other conditions, all of which the Company and its subsidiaries, as applicable, were in compliance with at March 31, 2013. In the event the Company and its subsidiaries do not comply with the applicable covenants and other conditions, alternative sources of funding may need to be pursued. For additional information on the covenants, certain other conditions and cross-default provisions, see Part II, Item 8 - Note 9, in the 2012 Annual Report.

The following table summarizes the outstanding credit facilities of the Company and its subsidiaries at March 31, 2013:

Company	Facility		Facility Limit			Amount Outstanding			Expiration Date
			(In millions)
MDU Resources Group, Inc.	Commercial paper/ Revolving credit agreement	(a)	$	125.0		$	72.0	(b)	10/4/17
Cascade Natural Gas Corporation	Revolving credit agreement		$	50.0	(c)	$	17.0		12/27/13
Intermountain Gas Company	Revolving credit agreement		$	65.0	(d)	$	20.5		8/11/13
Centennial Energy Holdings, Inc.	Commercial paper/ Revolving credit agreement	(e)	$	500.0		$	229.0	(b)	6/8/17
(a) The $125 million commercial paper program is supported by a revolving credit agreement with various banks totaling $125 million (provisions allow for increased borrowings, at the option of the Company on stated conditions, up to a maximum of $150 million). There were no amounts outstanding under the credit agreement. (b) Amount outstanding under commercial paper program. (c) Certain provisions allow for increased borrowings, up to a maximum of $75 million. (d) Certain provisions allow for increased borrowings, up to a maximum of $80 million. (e) The $500 million commercial paper program is supported by a revolving credit agreement with various banks totaling $500 million (provisions allow for increased borrowings, at the option of Centennial on stated conditions, up to a maximum of $650 million). There were no amounts outstanding under the credit agreement.

The Company's and Centennial's respective commercial paper programs are supported by revolving credit agreements. While the amount of commercial paper outstanding does not reduce available capacity under the respective revolving credit agreements, the Company and Centennial do not issue commercial paper in an aggregate amount exceeding the available

41

capacity under their credit agreements. The commercial paper borrowings may vary during the period, largely the result of fluctuations in working capital requirements due to the seasonality of the construction businesses.

The following includes information related to the preceding table.

MDU Resources Group, Inc. The Company's revolving credit agreement supports its commercial paper program. Commercial paper borrowings under this agreement are classified as long-term debt as they are intended to be refinanced on a long-term basis through continued commercial paper borrowings. The Company's objective is to maintain acceptable credit ratings in order to access the capital markets through the issuance of commercial paper. Downgrades in the Company's credit ratings have not limited, nor are currently expected to limit, the Company's ability to access the capital markets. If the Company were to experience a downgrade of its credit ratings, it may need to borrow under its credit agreement and may experience an increase in overall interest rates with respect to its cost of borrowings.

Prior to the maturity of the credit agreement, the Company expects that it will negotiate the extension or replacement of this agreement. If the Company is unable to successfully negotiate an extension of, or replacement for, the credit agreement, or if the fees on this facility become too expensive, which the Company does not currently anticipate, the Company would seek alternative funding.

Due to the $246.8 million after-tax noncash write-downs of oil and natural gas properties in 2012, earnings were insufficient by $17.2 million and $51.2 million to cover fixed charges for the 12 months ended March 31, 2013 and December 31, 2012, respectively. If the $246.8 million after-tax noncash write-downs were excluded, the coverage of fixed charges including preferred stock dividends would have been 4.6 times and 4.4 times for the 12 months ended March 31, 2013 and December 31, 2012, respectively.

The coverage of fixed charges including preferred stock dividends, that excludes the effect of the after-tax noncash write-downs of oil and natural gas properties is a non-GAAP financial measure. The Company believes that this non-GAAP financial measure is useful because the write-downs excluded are not indicative of the Company's cash flows available to meet its fixed charges obligations. The presentation of this additional information is not meant to be considered a substitute for the financial measure prepared in accordance with GAAP.

Total equity as a percent of total capitalization was 59 percent, 66 percent and 60 percent at March 31, 2013 and 2012 and December 31, 2012, respectively. This ratio is calculated as the Company's total equity, divided by the Company's total capital. Total capital is the Company's total debt, including short-term borrowings and long-term debt due within one year, plus total equity. This ratio indicates how a company is financing its operations, as well as its financial strength.

The Company currently has a shelf registration statement on file with the SEC, under which the Company may issue and sell any combination of common stock and debt securities. The Company may sell all or a portion of such securities if warranted by market conditions and the Company's capital requirements. Any public offer and sale of such securities will be made only by means of a prospectus meeting the requirements of the Securities Act and the rules and regulations thereunder. The Company's board of directors currently has authorized the issuance and sale of up to an aggregate of $1.0 billion worth of such securities. The Company's board of directors reviews this authorization on a periodic basis and the aggregate amount of securities authorized may be increased in the future.

MDU Energy Capital, LLC MDU Energy Capital has contracted to issue $25.0 million of Senior Notes on May 15, 2013, under a note purchase agreement dated October 22, 2012.

Centennial Energy Holdings, Inc. Centennial's revolving credit agreement supports its commercial paper program. Commercial paper borrowings under this agreement are classified as long-term debt as they are intended to be refinanced on a long-term basis through continued commercial paper borrowings. Centennial's objective is to maintain acceptable credit ratings in order to access the capital markets through the issuance of commercial paper. Downgrades in Centennial's credit ratings have not limited, nor are currently expected to limit, Centennial's ability to access the capital markets. If Centennial were to experience a downgrade of its credit ratings, it may need to borrow under its credit agreement and may experience an increase in overall interest rates with respect to its cost of borrowings.

Prior to the maturity of the Centennial credit agreement, Centennial expects that it will negotiate the extension or replacement of this agreement, which provides credit support to access the capital markets. In the event Centennial is unable to successfully negotiate this agreement, or in the event the fees on this facility become too expensive, which Centennial does not currently anticipate, it would seek alternative funding.

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On February 20, 2013, under a note purchase agreement dated December 20, 2012, Centennial issued $100.0 million of Senior Notes with due dates ranging from December 2019 to December 2027 at a weighted average interest rate of 4.7 percent.

Off balance sheet arrangements

In connection with the sale of the Brazilian Transmission Lines, Centennial has agreed to guarantee payment of any indemnity obligations of certain of the Company's indirect wholly owned subsidiaries who are the sellers in three purchase and sale agreements for periods ranging up to 10 years from the date of sale. The guarantees were required by the buyers as a condition to the sale of the Brazilian Transmission Lines.

Centennial continues to guarantee CEM's obligations under a construction contract for an electric generating facility near Hobbs, New Mexico. For more information, see Note 18.

Contractual obligations and commercial commitments

There are no material changes in the Company's contractual obligations relating to long-term debt, estimated interest payments, operating leases, purchase commitments, derivatives, asset retirement obligations and minimum funding requirements for its defined benefit plans for 2013 from those reported in the 2012 Annual Report.

For more information on the Company's uncertain tax positions, see Note 14.

For more information on contractual obligations and commercial commitments, see Part II, Item 7 in the 2012 Annual Report.

ITEM 3. QUANTITATIVE AND QUALITATIVE DISCLOSURES ABOUT MARKET RISK

The Company is exposed to the impact of market fluctuations associated with commodity prices, interest rates and foreign currency. The Company has policies and procedures to assist in controlling these market risks and utilizes derivatives to manage a portion of its risk.

For more information on derivative instruments and commodity price risk, see Part II, Item 7A in the 2012 Annual Report, the Consolidated Statements of Comprehensive Income and Note 12.

Commodity price risk

Fidelity utilizes derivative instruments to manage a portion of the market risk associated with fluctuations in the price of oil and natural gas and basis differentials on forecasted sales of oil and natural gas production.

The following table summarizes derivative agreements entered into by Fidelity as of March 31, 2013. These agreements call for Fidelity to receive fixed prices and pay variable prices.

	(Forward notional volume and fair value in thousands)
		Weighted Average Fixed Price (Per Bbl/MMBtu)		Forward Notional Volume (Bbl/MMBtu)	Fair Value
Oil swap agreements maturing in 2013		$	98.67	1,925	$	3,633
Oil swap agreements maturing in 2014		$	95.08	362	$	482
Natural gas swap agreements maturing in 2013		$	3.76	14,970	$	(5,464	)
Natural gas swap agreements maturing in 2014		$	4.13	7,300	$	(709	)
Natural gas swap agreement maturing in 2015		$	4.28	3,650	$	(74	)
		Weighted Average Floor/Ceiling Price (Per Bbl)		Forward Notional Volume (Bbl)	Fair Value
Oil collar agreements maturing in 2013		$92.50/$107.03		550	$	324

Interest rate risk

There were no material changes to interest rate risk faced by the Company from those reported in the 2012 Annual Report.

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Centennial entered into interest rate swap agreements to manage a portion of its interest rate exposure on the forecasted issuance of long-term debt. The agreements call for Centennial to receive payments from or make payments to counterparties based on the difference between fixed and variable rates as specified by the interest rate swap agreements.

The following table summarizes derivative instruments entered into by Centennial as of March 31, 2013. The agreements call for Centennial to receive variable rates and pay fixed rates.

(Notional amount and fair value in thousands)
	Weighted Average Fixed Interest Rate		Notional Amount		Fair Value
Interest rate swap agreements with mandatory termination dates in 2013	3.23	%	$	40,000	$	(4,458	)

Foreign currency risk

The Company's equity method investment in ECTE is exposed to market risks from changes in foreign currency exchange rates between the U.S. dollar and the Brazilian Real. For more information, see Part II, Item 8 - Note 4 in the 2012 Annual Report.

At March 31, 2013, the Company had no outstanding foreign currency hedges.

ITEM 4. CONTROLS AND PROCEDURES

The following information includes the evaluation of disclosure controls and procedures by the Company's chief executive officer and the chief financial officer, along with any significant changes in internal controls of the Company.

Evaluation of disclosure controls and procedures

The term "disclosure controls and procedures" is defined in Rules 13a-15(e) and 15d-15(e) under the Exchange Act. The Company's disclosure controls and other procedures are designed to provide reasonable assurance that information required to be disclosed in the reports that the Company files or submits under the Exchange Act is recorded, processed, summarized and reported within the time periods specified in the SEC's rules and forms. The Company's disclosure controls and procedures include controls and procedures designed to provide reasonable assurance that information required to be disclosed is accumulated and communicated to management, including the Company's chief executive officer and chief financial officer, to allow timely decisions regarding required disclosure. The Company's management, with the participation of the Company's chief executive officer and chief financial officer, has evaluated the effectiveness of the Company's disclosure controls and procedures. Based upon that evaluation, the chief executive officer and the chief financial officer have concluded that, as of the end of the period covered by this report, such controls and procedures were effective at a reasonable assurance level.

Changes in internal controls

No change in the Company's internal control over financial reporting (as defined in Rules 13a-15(f) and 15d-15(f) under the Exchange Act) occurred during the quarter ended March 31, 2013, that has materially affected, or is reasonably likely to materially affect, the Company's internal control over financial reporting.

PART II -- OTHER INFORMATION

ITEM 1. LEGAL PROCEEDINGS

For information regarding legal proceedings, see Note 18, which is incorporated herein by reference.

ITEM 1A. RISK FACTORS

This Form 10-Q contains forward-looking statements within the meaning of Section 21E of the Exchange Act. Forward-looking statements are all statements other than statements of historical fact, including without limitation those statements that are identified by the words "anticipates," "estimates," "expects," "intends," "plans," "predicts" and similar expressions.

The Company is including the following factors and cautionary statements in this Form 10-Q to make applicable and to take advantage of the safe harbor provisions of the Private Securities Litigation Reform Act of 1995 for any forward-looking statements made by, or on behalf of, the Company. Forward-looking statements include statements concerning plans,

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objectives, goals, strategies, future events or performance, and underlying assumptions (many of which are based, in turn, upon further assumptions) and other statements that are other than statements of historical facts. From time to time, the Company may publish or otherwise make available forward-looking statements of this nature, including statements contained within Prospective Information. All these subsequent forward-looking statements, whether written or oral and whether made by or on behalf of the Company, also are expressly qualified by these factors and cautionary statements.

Forward-looking statements involve risks and uncertainties, which could cause actual results or outcomes to differ materially from those expressed. The Company's expectations, beliefs and projections are expressed in good faith and are believed by the Company to have a reasonable basis, including without limitation, management's examination of historical operating trends, data contained in the Company's records and other data available from third parties. Nonetheless, the Company's expectations, beliefs or projections may not be achieved or accomplished.

Any forward-looking statement contained in this document speaks only as of the date on which the statement is made, and the Company undertakes no obligation to update any forward-looking statement or statements to reflect events or circumstances that occur after the date on which the statement is made or to reflect the occurrence of unanticipated events. New factors emerge from time to time, and it is not possible for management to predict all of the factors, nor can it assess the effect of each factor on the Company's business or the extent to which any factor, or combination of factors, may cause actual results to differ materially from those contained in any forward-looking statement.

There are no material changes in the Company's risk factors from those reported in Part I, Item 1A - Risk Factors in the 2012 Annual Report. These factors and the other matters discussed herein are important factors that could cause actual results or outcomes for the Company to differ materially from those discussed in the forward-looking statements included elsewhere in this document.

ITEM 4. MINE SAFETY DISCLOSURES

For information regarding mine safety violations or other regulatory matters required by Section 1503(a) of the Dodd-Frank Act and Item 104 of Regulation S-K, see Exhibit 95 to this Form 10-Q, which is incorporated herein by reference.

ITEM 6. EXHIBITS

See the index to exhibits immediately preceding the exhibits filed with this report.

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SIGNATURES

Pursuant to the requirements of the Exchange Act, the registrant has duly caused this report to be signed on its behalf by the undersigned thereunto duly authorized.

		MDU RESOURCES GROUP, INC.
DATE:	May 7, 2013	BY:	/s/ Doran N. Schwartz
			Doran N. Schwartz
			Vice President and Chief Financial Officer
		BY:	/s/ Nicole A. Kivisto
			Nicole A. Kivisto
			Vice President, Controller and Chief Accounting Officer

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EXHIBIT INDEX

Exhibit No.
3	Company Bylaws, as amended and restated, on March 4, 2013
+10(a)	MDU Resources Group, Inc. Executive Incentive Compensation Plan, as amended March 4, 2013, and Rules and Regulations, as amended March 4, 2013
12	Computation of Ratio of Earnings to Fixed Charges and Combined Fixed Charges and Preferred Stock Dividends
31(a)	Certification of Chief Executive Officer filed pursuant to Section 302 of the Sarbanes-Oxley Act of 2002
31(b)	Certification of Chief Financial Officer filed pursuant to Section 302 of the Sarbanes-Oxley Act of 2002
32	Certification of Chief Executive Officer and Chief Financial Officer furnished pursuant to 18 U.S.C. Section 1350, as adopted pursuant to Section 906 of the Sarbanes-Oxley Act of 2002
95	Mine Safety Disclosures
101	The following materials from MDU Resources Group, Inc.'s Quarterly Report on Form 10-Q for the quarter ended March 31, 2013, formatted in XBRL (eXtensible Business Reporting Language): (i) the Consolidated Statements of Income, (ii) the Consolidated Statements of Comprehensive Income, (iii) the Consolidated Balance Sheets, (iv) the Consolidated Statements of Cash Flows and (v) the Notes to Consolidated Financial Statements, tagged in summary and detail

+ Management contract, compensatory plan or arrangement.

MDU Resources Group, Inc. agrees to furnish to the SEC upon request any instrument with respect to long-term debt that MDU Resources Group, Inc. has not filed as an exhibit pursuant to the exemption provided by Item 601(b)(4)(iii)(A) of Regulation S-K.

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EX-3

Bylaws of

MDU RESOURCES

GROUP, INC.

TABLE OF CONTENTS

TO BYLAWS

		Page No.
OFFICES		1
	1.01 Registered Office	1
	1.02 Other Offices	1
MEETINGS OF STOCKHOLDERS		1
	2.01 Place of Meetings	1
	2.02 Annual Meetings	1
	2.03 Notice of Annual Meeting	2
	2.04 Stockholders List	2
	2.05 Notice of Special Meeting	2
	2.06 Quorum; Adjournment; and Organization	2
	2.07 Voting Rights	3
	2.08 Nominations for Director	3
	2.09 Business at Meetings of Stockholders	7
DIRECTORS		9
	3.01 Authority of Directors	9
	3.02 Qualifications	9
	3.03 Place of Meetings	9
	3.04 Annual Meetings	9
	3.05 Regular Meetings	9
	3.06 Special Meetings	9
	3.07 Quorum	10
	3.08 Participation of Directors by Conference Telephone	10
	3.09 Written Action of Directors	10
	3.10 Committees	10
	3.11 Reports of Committees	10
	3.12 Compensation of Directors	11
	3.13 Chairman of the Board	11
NOTICES		11
	4.01 Notices	11
	4.02 Waiver	11
OFFICERS		11
	5.01 Election, Qualifications	11
	5.02 Additional Officers	12
	5.03 Salaries	12
	5.04 Term	12

	5.05 Chief Executive Officer	12
	5.06 The President	12
	5.07 The Vice Presidents	12
	5.08 The Secretary and Assistant Secretaries	12
	5.09 Treasurer and Assistant Treasurers	13
	5.10 General Counsel	13
	5.11 Authority and Duties	14
	5.12 Execution of Instruments	14
	5.13 Execution of Proxies	14
CERTIFICATES OF STOCK		14
	6.01 Certificates	14
	6.02 Signatures	14
	6.03 Special Designation on Certificates	15
	6.04 Lost Certificates	15
	6.05 Transfers of Stock	15
	6.06 Record Date	15
	6.07 Registered Stockholders	15
GENERAL PROVISIONS		16
	7.01 Dividends	16
	7.02 Checks	16
	7.03 Fiscal Year	16
	7.04 Seal	16
	7.05 Inspection of Books and Records	16
	7.06 Amendments	16
	7.07 Indemnification of Officers, Directors, Employees and Agents	17
	7.08 Severability	18

BYLAWS OF
MDU RESOURCES GROUP, INC.

OFFICES

1.01    Registered Office. The registered office shall be in the City of Wilmington, County of New Castle, State of Delaware.

1.02    Other Offices. The Corporation may also have offices at such other places, both within and without the State of Delaware, as the Board of Directors may from time to time determine or the business of the Corporation may require.

MEETINGS OF STOCKHOLDERS

2.01    Place of Meetings. All meetings of the stockholders for the election of Directors shall be held in the City of Bismarck, State of North Dakota, at such place as may be fixed from time to time by the Board of Directors, or at such other place, either within or without the State of Delaware, as shall be designated from time to time by the Board of Directors, or, in the sole discretion of the Board of Directors, by means of remote communication as authorized by the laws of Delaware, as shall be stated in the notice of the meeting. Meetings of stockholders for any other purpose may be held at such time and place, within or without the State of Delaware, or, in the sole discretion of the Board of Directors, by means of remote communication as authorized by the laws of Delaware as shall be stated in the notice of the meeting or in a duly executed waiver of notice thereof.

2.02    Annual Meetings. Annual meetings of stockholders shall be held on the fourth Tuesday of April in each year, if not a legal holiday, and if a legal holiday, then on the next secular day following, at 11:00 A.M., or at such other date and time as shall be designated from time to time by the Board of Directors and stated in the notice of the meeting, at which they shall elect a Board of Directors and transact such other business as may properly be brought before the meeting. The election of directors shall be by written ballot including, if authorized by the Board of Directors, by ballot submitted by electronic transmission in compliance with the laws of Delaware.

Except as otherwise provided in the Certificate of Incorporation or these Bylaws, each director shall be elected by the vote of the majority of the votes cast with respect to the director at any meeting for the election of directors at which a quorum is present, provided that if, as of the day next preceding the date the Corporation first gives its notice of meeting for such meeting of stockholders, the number of nominees (including any nominees stockholders have proposed to nominate by giving notice pursuant to Section 2.08 hereof) exceeds the number of directors to be elected, the directors shall be elected by a plurality of the votes of the shares present in person or represented by proxy at any such meeting and entitled to vote on the election of directors. For purposes of this Section, a majority of the votes cast means that the number of

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votes cast “for” a director’s election must exceed the number of votes cast “against” that director’s election (with “abstentions” and “broker nonvotes” not counted as a vote cast either “for” or “against” that director’s election). If directors are to be elected by a plurality of the votes of the shares present in person or represented by proxy at any such meeting and entitled to vote on the election of directors, stockholders shall not be permitted to vote “against” a nominee.

2.03    Notice of Annual Meeting. Notice, in writing or by a form of electronic transmission in compliance with the laws of Delaware, of the annual meeting, stating the place, if any, date and hour of the meeting, and the means of remote communications, if any, by which stockholders and proxy holders may be deemed to be present in person and vote at such meeting, shall be given to each stockholder entitled to vote at such meeting not less than ten nor more than sixty days before the date of the meeting.

2.04    Stockholders List. The officer who has charge of the stock ledger of the Corporation shall prepare and make, at least ten days before every meeting of the stockholders, a complete list of the stockholders entitled to vote at the meeting, arranged in alphabetical order, and showing the address of each stockholder and the number of shares registered in the name of each stockholder. Such list shall be open to the examination of any stockholder, for any purpose germane to the meeting, for a period of at least ten days prior to the meeting: (i) on a reasonably accessible electronic network, provided that the information required to gain access to such list is provided with the notice of the meeting or (ii)during ordinary business hours, at the principal place of business of the Corporation. If the meeting is to be held at a place, then the list shall also be produced and kept at the time and place of the meeting during the whole time thereof, and may be inspected by any stockholder who is present. If the meeting is to be held solely by means of remote communication, then the list shall also be open to the examination of any stockholder during the meeting on a reasonably accessible electronic network, and the information required to access the electronic list shall be provided with the notice of the meeting.

2.05    Notice of Special Meeting. Notice of a special meeting, in writing or by a form of electronic transmission as determined solely by the Board of Directors in compliance with the laws of Delaware, stating the place, date and hour of the meeting, the means of remote communications, if any, by which the stockholders and proxy holders may be deemed to be present in person and vote at such meeting, and the purpose or purposes for which the meeting is called, shall be given not less than ten (10) nor more than sixty (60) days before the date of the meeting, to each stockholder entitled to vote at such meeting. Business transacted at a special meeting of stockholders shall be confined to the purpose or purposes of the meeting specified in the notice of meeting (or supplement thereto) given by or at the direction of the Board of Directors. Stockholders may not make nominations for directors or bring any business before a special meeting of stockholders.

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2.06    Quorum; Adjournment; and Organization.

(a) Quorum. The holders of a majority of the stock issued and outstanding and entitled to vote in person or by proxy, shall constitute a quorum at all meetings of the stockholders for the transaction of business, except as provided herein and except as otherwise provided by statute or by the Certificate of Incorporation. If, however, such quorum shall not be present or represented at any meeting of the stockholders, the meeting may be adjourned from time to time in accordance with paragraph (b) of this Section 2.06 until a quorum shall be so present or represented. For purposes of the foregoing, where a separate vote by a class or classes is required for any matter, the holders of a majority of the outstanding shares of such class or classes entitled to vote, present in person or represented by proxy, shall constitute a quorum to take action with respect to that vote on that matter, except as provided herein and except as otherwise provided by statute or by the Certificate of Incorporation. Two or more classes or series of stock shall be considered a single class if the holders thereof are entitled to vote together as a single class at the meeting.

(b) Adjournment. Any meeting of stockholders, annual or special, whether or not a quorum is present, may be adjourned for any reason from time to time by either (i) the chairman of the meeting or (ii) the stockholders by the vote of the holders of a majority of the stock entitled to vote, present in person or represented by proxy, without notice of the adjourned meeting, if the time and place thereof, and the means of remote communications, if any, by which stockholders and proxy holders may be deemed to be present in person and vote at such adjourned meeting are announced at the meeting at which the adjournment is taken. At such adjourned meeting, any business may be transacted which might have been transacted at the original meeting. If the adjournment is for more than thirty days, or if, after the adjournment, a new record date is fixed for the adjourned meeting, a notice of the adjourned meeting shall be given to each stockholder of record entitled to vote at the meeting.

(c)Organization. Meetings of stockholders shall be presided over by the Chairman of the Board, or in the absence of the Chairman of the Board by the Chief Executive Officer, or in the absence of the Chief Executive Officer by a person designated by the Board of Directors, or in the absence of such designation by a chairman chosen at the meeting. The Secretary shall act as secretary of the meeting, but in his or her absence the chairman of the meeting may appoint any person to act as secretary of the meeting. The order of business at each such meeting shall be as determined by the chairman of the meeting. The chairman of the meeting shall have the right and authority to prescribe such rules, regulations and procedures and to do all such acts and things as, in the judgment of the chairman of the meeting, are necessary or desirable for the proper conduct of the meeting and are not inconsistent with any rules or regulations adopted by the Board of Directors, including the establishment of procedures for the maintenance of order and safety, limitations on the time allotted to questions or comments on the affairs of the Corporation, restrictions on entry to such meeting after the time prescribed for the commencement thereof and the opening and closing of the voting polls for each item upon which a vote is to be taken. Rules, regulations or procedures established by the chairman of the meeting need not be in writing.

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2.07    Voting Rights. When a quorum is present at any meeting, the vote of the holders of a majority of the stock having voting power, present in person or represented by proxy, shall decide any question brought before such meeting, unless the question is one upon which, by express provision of the statutes, the Certificate of Incorporation or these Bylaws, a different vote is required, in which case such express provision shall govern and control the decision of such question. Unless otherwise provided in the Certificate of Incorporation, each stockholder shall, at every meeting of the stockholders, be entitled to one vote in person or by proxy for each share of the capital stock having voting power held by such stockholder, but no proxy shall be voted on after three years from its date, unless the proxy provides for a longer period.

2.08    Nominations for Director. Nominations of persons for election to the Board of Directors of the Corporation may be made only (i) by the Board of Directors at any meeting of stockholders and (ii) at an annual meeting of stockholders, by any stockholder of the Corporation who is entitled to vote for the election of directors and who has complied with the procedures established by this Section 2.08. For a nomination to be properly brought before an annual meeting by a stockholder, the stockholder intending to make the nomination (the “Proponent”) must have given timely and proper notice thereof in writing to the Secretary of the Corporation, in accordance with, and containing all information and the completed questionnaire provided for in, this Section 2.08.

To be timely, a Proponent’s notice must be delivered to or mailed to the Secretary of the Corporation and received at the principal executive offices of the Corporation not later than the close of business 90 days prior to the first anniversary of the preceding year’s annual meeting of stockholders; provided, however, in the event the date of the annual meeting is advanced more than 30 days prior to such anniversary date or delayed more than 60 days after such anniversary date then to be timely such notice must be received by the Corporation not later than the close of business on the later of the 90th day prior to the date of the meeting or the 10th day following the date of Public Disclosure (defined below) of the date of the annual meeting. In no event shall any adjournment or postponement of an annual meeting of stockholders or announcement thereof commence a new time period or extend any time period for the giving of a Proponent’s notice as required by this Section 2.08.

A Proponent’s notice to the Secretary shall set forth: (a) as to each person the Proponent proposes to nominate for election as a director at the annual meeting, (i) the name, age, business address, residence address and telephone number of such nominee and the name, business address and residence address of any Nominee Associated Persons (defined below), (ii) the principal occupation or employment of such nominee, (iii) the class and number of shares of stock of the Corporation that are owned (beneficially and of record) by or on behalf of such nominee and by or on behalf of any Nominee Associated Person, as of the date of the Proponent’s notice, (iv) a description of such nominee’s qualifications to be a director and (v) a statement as to whether such nominee would be an independent director, and the basis therefor, under the listing standards of the New York Stock Exchange and the Corporate Governance Guidelines and (b) as to the Proponent and any Stockholder Associated Person (defined below) on whose behalf the nomination is being made, (i) the

4

name and address of the Proponent, and any holder of record of the Proponent’s shares of stock, as they appear on the Corporation’s books, and of any Stockholder Associated Person, (ii) the class and number of shares of stock of the Corporation that are owned (beneficially and of record) by or on behalf of the Proponent and by or on behalf of any Stockholder Associated Person, as of the date of the Proponent’s notice, the date such shares were acquired and the investment intent with respect thereto, (iii) a representation and agreement that the Proponent will notify the Corporation in writing of the class and number of shares of stock of the Corporation that are owned (beneficially and of record) by or on behalf of the Proponent and by or on behalf of any Stockholder Associated Person, as of the record date for the meeting, not later than the close of business on the third business day following the later of the record date or the date of Public Disclosure of the record date, (iv) a description of all purchases and sales of, or other transactions involving in any way, shares of stock of the Corporation by or on behalf of the Proponent and by or on behalf of any Stockholder Associated Person during the twenty-four month period prior to the date of the Proponent’s notice, including the date of the transactions, the class and number of shares and the consideration (without regard to whether such shares were or were not owned by the Proponent or any such person), (v) a description of any agreement, arrangement or understanding, including any Derivative Instrument (defined below), that has been entered into or is in effect as of the date of the Proponent’s notice, by or on behalf of the Proponent, any Stockholder Associated Person, any nominee or any Nominee Associated Person, the effect or intent of which is to mitigate loss to, manage risk or benefit of stock price changes for, or increase or decrease the voting power of, the Proponent, any Stockholder Associated Person, any nominee or any Nominee Associated Person with respect to the Corporation’s securities, (vi) a representation and agreement that the Proponent will notify the Corporation in writing of any such agreement, arrangement or understanding, including any Derivative Instrument, that has been entered into or is in effect as of the record date for the meeting, not later than the close of business on the third business day following the later of the record date or the date of Public Disclosure of the record date, (vii) a description of any other agreement, arrangement or understanding that has been entered into or is in effect as of the date of the Proponent’s notice, between or among the Proponent, any Stockholder Associated Person, any nominee, any Nominee Associated Person or any other person, and that relates to such nomination or such nominee’s service as a director of the Corporation, (viii) a representation and agreement that the Proponent will notify the Corporation in writing of any such agreement, arrangement or understanding that has been entered into or is in effect as of the record date for the meeting, not later than the close of business on the third business day following the later of the record date or the date of Public Disclosure of the record date, (ix) a representation that the Proponent is the holder of record or beneficial owner of shares of stock of the Corporation entitled to vote for the election of directors at the annual meeting and intends to appear in person or by proxy at the meeting to nominate any such nominee and (x) a representation as to whether the Proponent intends to deliver a proxy statement and/or form of proxy to stockholders and/or otherwise to solicit proxies from stockholders in support of such nomination.

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The Proponent’s notice shall also include a completed questionnaire (in the form provided by the Secretary of the Corporation upon request by the Proponent) signed by such nominee with respect to information of the type required by the Corporation’s Questionnaires for Directors and Officers of the Corporation in connection with the Annual Meeting of Stockholders and Various Reports to the Securities and Exchange Commission. The completed questionnaire shall include a statement that such nominee, if elected, before such nominee is nominated to serve on the Board of Directors at the next meeting of stockholders at which such nominee would face election, will tender to the Board of Directors his or her irrevocable resignation that will be effective in an uncontested election of Directors only, upon (i) such nominee’s receipt of a greater number of votes “against” election than votes “for” election at the Corporation’s meeting of stockholders and (ii) acceptance of such resignation by the Board of Directors, in accordance with the Corporation’s Corporate Governance Guidelines. The questionnaire shall also include a representation and agreement that such nominee (i) is not and will not become a party to (A) any agreement, arrangement or understanding with, and has not given any commitment or assurance to, any person or entity as to how such nominee, if elected as a director of the Corporation, will act or vote on any issue or question (a “Voting Commitment”) that has not been, or will not be within three business days thereafter, disclosed to the Corporation or (B) any Voting Commitment that could limit or interfere with the nominee’s ability to comply, if elected as a director of the Corporation, with such nominee’s fiduciary duties under applicable law, (ii) is not and will not become a party to any agreement, arrangement or understanding with any person or entity other than the Corporation with respect to any direct or indirect compensation, reimbursement or indemnification in connection with service or action as a director of the Corporation that has not been, or will not be within three business days thereafter, disclosed to the Corporation and (iii) in such nominee’s individual capacity and on behalf of any person or entity on whose behalf the nomination is being made, would be in compliance, if elected as a director of the Corporation, and will comply, with applicable law and all applicable corporate governance, code of conduct and ethics, conflict of interest, corporate opportunities, confidentiality and stock ownership and trading policies and guidelines of the Corporation.

No person proposed to be nominated by a stockholder shall be eligible for election as a director of the Corporation unless such person is nominated in accordance with the procedures set forth in this Section 2.08. If the Proponent intending to nominate a person for election as a director of the Corporation at an annual meeting pursuant to this Section 2.08 does not give timely and proper notice thereof in writing to the Secretary of the Corporation, in accordance with, and containing all information and the completed questionnaire provided for in, this Section 2.08, or if the Proponent (or a qualified representative of the Proponent) does not appear at the meeting to nominate such person for election as a director of the Corporation, then, in any such case, such proposed nomination shall not be made, notwithstanding the fact that proxies in respect of such nomination may have been solicited or obtained. The chairman of the meeting shall, if the facts warrant, determine that the nomination was not properly made in accordance with the provisions of this Section 2.08, and, if the chairman should so determine, he or she shall declare to the meeting that such nomination was not properly made and shall be disregarded.

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The requirements of this Section 2.08 shall apply to the nomination by a stockholder of a person for election as a director without regard to whether such nomination also is intended to be included in the Corporation’s proxy statement pursuant to Rule 14a-8 of the Securities Exchange Act of 1934, as amended (the “Exchange Act”), or whether such nomination is presented to stockholders by means of a proxy solicitation by any person other than by or on behalf of the Board of Directors.

For purposes of the Bylaws:

“Derivative Instrument” means any option, warrant, convertible security, stock appreciation right, swap or similar right with an exercise or conversion privilege or a settlement payment or mechanism at a price related to any class or series of shares of stock of the Corporation or with a value derived in whole or in part from the value of any class or series of shares of stock of the Corporation, whether or not such instrument or right shall be subject to settlement in the underlying class or series of shares of stock of the Corporation or otherwise directly or indirectly owned and any other direct or indirect opportunity to profit or share in any profit derived from any increase or decrease in the value of shares of stock of the Corporation.

“Nominee Associated Person” of any nominee for election as a director means (i) any affiliate or associate (as such terms are defined for purposes of the Exchange Act) of the nominee and any other person acting in concert with any of the foregoing, (ii) any beneficial owner of shares of stock of the Corporation owned of record or beneficially by such nominee and (iii) any person controlling, controlled by or under common control with such Nominee Associated Person.

“Public Disclosure” means disclosure made in a press release reported by Dow Jones News Service, Associated Press or a comparable national news service or in a document filed by the Corporation pursuant to Section 13, 14 or 15(d) of the Exchange Act.

“Stockholder Associated Person” of any stockholder means (i) any affiliate or associate (as such terms are defined for purposes of the Exchange Act) of the stockholder and any other person acting in concert with any of the foregoing, (ii) any beneficial owner of shares of stock of the Corporation owned of record or beneficially by such stockholder and (iii) any person controlling, controlled by or under common control with such Stockholder Associated Person.

2.09    Business at Meetings of Stockholders. At any meeting of stockholders, only such business shall be transacted as shall have been properly brought before the meeting. To be properly brought before a meeting of stockholders, business must be (a) specified in the notice of meeting (or any supplement thereto) given by or at the direction of the Board of Directors, (b) otherwise properly brought before the meeting by or at the direction of the Board of Directors or (c) in the case of an annual meeting of stockholders, properly brought before the meeting by a stockholder who is entitled to vote and who has complied with the procedures established by this Section 2.09. For business to be properly brought before an annual meeting by a stockholder (other than the nomination of a person for election as a director, which is governed by Section 2.08 of these Bylaws), the Proponent (defined in Section 2.08) must have given timely and proper

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notice thereof in writing to the Secretary of the Corporation, in accordance with, and containing all information provided for, in this Section 2.09, and such business must be a proper matter for stockholder action under the General Corporation Law of Delaware.

To be timely, a Proponent’s notice must be delivered to or mailed to the Secretary of the Corporation and received at the principal executive offices of the Corporation not later than the close of business 90 days prior to the first anniversary of the preceding year’s annual meeting of stockholders; provided, however, in the event the date of the annual meeting is advanced more than 30 days prior to such anniversary date or delayed more than 60 days after such anniversary date, then to be timely such notice must be received by the Corporation not later than the close of business on the later of the 90th day prior to the date of the meeting or the 10th day following the date of Public Disclosure (defined in Section 2.08) of the date of the annual meeting. In no event shall any adjournment or postponement of an annual meeting of stockholders or announcement thereof commence a new time period or extend any time period for the giving of a Proponent’s notice as required by this Section 2.09.

A Proponent’s notice to the Secretary shall set forth: (a) as to each matter the Proponent proposes to bring before the annual meeting, a description of the business desired to be brought before the annual meeting, the reasons for transacting such business at the meeting and the text of any resolutions to be proposed, and whether the Proponent has communicated with any other stockholder or beneficial owner of shares of stock of the Corporation regarding such business and (b) as to the Proponent and any Stockholder Associated Person (defined in Section 2.08) on whose behalf the proposal is being made, (i) the name and address of the Proponent, and any holder of record of the Proponent’s shares of stock, as they appear on the Corporation’s books, and of any Stockholder Associated Person, (ii) the class and number of shares of stock of the Corporation that are owned (beneficially and of record) by or on behalf of the Proponent and by or on behalf of any Stockholder Associated Person, as of the date of the Proponent’s notice, the date such shares were acquired and the investment intent with respect thereto, (iii) a representation and agreement that the Proponent will notify the Corporation in writing of the class and number of shares of stock of the Corporation that are owned (beneficially and of record) by or on behalf of the Proponent and by or on behalf of any Stockholder Associated Person, as of the record date for the meeting, not later than the close of business on the third business day following the later of the record date or the date of Public Disclosure of the record date, (iv) a description of all purchases and sales of, or other transactions involving in any way, shares of stock of the Corporation by or on behalf of the Proponent and by or on behalf of any Stockholder Associated Person during the twenty-four month period prior to the date of the Proponent’s notice, including the date of the transactions, the class and number of shares and the consideration (without regard to whether such shares involved were or were not owned by the Proponent or any such person), (v) a description of any agreement, arrangement or understanding, including any Derivative Instrument (defined in Section 2.08), that has been entered into or is in effect as of the date of the Proponent’s notice, by or on behalf of the Proponent or any Stockholder Associated Person, the effect or intent of which is to mitigate loss to, manage risk or benefit of stock price changes for, or increase or decrease the voting power of, the Proponent or any

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Stockholder Associated Person with respect to the Corporation’s securities, (vi) a representation and agreement that the Proponent will notify the Corporation in writing of any such agreement, arrangement or understanding, including any Derivative Instrument, that has been entered into or is in effect as of the record date for the meeting, not later than the close of business on the third business day following the later of the record date or the date of Public Disclosure of the record date, (vii) any material interest of the Proponent or any Stockholder Associated Person in such business, (viii) a description of any other agreement, arrangement or understanding that has been entered into or is in effect as of the date of the Proponent’s notice, between or among the Proponent, any Stockholder Associated Person or any other person, and that relates to such business, (ix) a representation and agreement that the Proponent will notify the Corporation in writing of any such agreement, arrangement or understanding that has been entered into or is in effect as of the record date for the meeting, not later than the close of business on the third business day following the later of the record date or the date of Public Disclosure of the record date, (x) a representation that the Proponent is the holder of record or beneficial owner of shares of stock of the Corporation entitled to vote for the election of directors at the annual meeting and intends to appear in person or by proxy at the meeting to propose such business and (xi) a representation as to whether the Proponent intends to deliver a proxy statement and/or form of proxy to stockholders and/or otherwise to solicit proxies from stockholders in support of such proposal.

No business proposed by a stockholder shall be transacted at an annual meeting of stockholders except in accordance with the procedures set forth in this Section 2.09. If the Proponent intending to propose business at an annual meeting pursuant to this Section 2.09 does not give timely and proper notice thereof in writing to the Secretary of the Corporation, in accordance with, and containing all information provided for in, this Section 2.09, or if the Proponent (or a qualified representative of the Proponent) does not appear at the meeting to present the proposed business, then, in any such case, such business shall not be transacted, notwithstanding the fact that proxies in respect of such business may have been solicited or obtained. The chairman of the meeting shall, if the facts warrant, determine that the business was not properly brought before the meeting in accordance with the provisions of this Section 2.09, and, if the chairman should so determine, he or she shall declare to the meeting that such business was not properly brought before the meeting and shall not be transacted.

The requirements of this Section 2.09 shall apply to any business to be brought before an annual meeting of stockholders by a stockholder (other than the nomination by a stockholder of a person for election as a director, which is governed by Section 2.08 of these Bylaws) without regard to whether such business also is intended to be included in the Corporation’s proxy statement pursuant to Rule 14a-8 of the Exchange Act or whether such business is presented to stockholders by means of a proxy solicitation by any person other than by or on behalf of the Board of Directors.

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DIRECTORS

3.01    Authority of Directors. The business of the Corporation shall be managed by its Board of Directors which may exercise all such powers of the Corporation and do all such lawful acts and things as are not by statute or by the Certificate of Incorporation or by these Bylaws directed or required to be exercised or done by the stockholders.

3.02    Qualifications. A person who is not an officer of the Corporation shall be ineligible to serve as a Director beyond the first regular meeting of the Board of Directors after the date he shall have attained the age of seventy-four (74). A person who is a “high ranking executive” (as defined in Section 5.01) of the Corporation shall be ineligible to serve as a Director beyond the first regular meeting of the Board of Directors after the date he shall have attained the age of sixty-five (65). A person shall be ineligible as a Director if, at the time he would otherwise be eligible for election, he is a former officer of the Corporation. Other restrictions and qualifications for Directors may be fixed from time to time by resolution passed by a majority of the whole Board of Directors.

3.03    Place of Meetings. The Board of Directors of the Corporation may hold meetings, both regular and special, either within or without the State of Delaware.

3.04    Annual Meetings. The first meeting of each newly elected Board of Directors shall be held at such time and place as shall be specified in a notice given as herein provided for regular meetings of the Board of Directors, or as shall be specified in a duly executed waiver of notice thereof.

3.05    Regular Meetings. Regular meetings of the Board of Directors may be held at the office of the Corporation in Bismarck, North Dakota, on the second Thursday following the first Monday of February, May, August and November of each year; provided, however, that if a legal holiday, then on the next preceding day that is not a legal holiday. Regular meetings of the Board of Directors may be held at other times and other places within or without the State of North Dakota on at least five days’ notice to each Director, either personally or by mail, telephone or another form of electronic transmission in compliance with the laws of Delaware.

3.06    Special Meetings. Special meetings of the Board may be called by the Chairman of the Board, Chief Executive Officer or President on three days’ notice to each Director, either personally or by mail, telephone or another form of electronic transmission in compliance with the laws of Delaware; special meetings shall be called by the Chairman, Chief Executive Officer, President or Secretary in like manner and on like notice on the written request of a majority of the Board of Directors.

3.07    Quorum. At all meetings of the Board, a majority of the Directors shall constitute a quorum for the transaction of business and the act of a majority of the Directors present at any such meeting at which there is a quorum shall be the act of the Board of Directors, except as may be otherwise specifically provided by statute, the Certificate of Incorporation or by these Bylaws. If a quorum shall not be present at any meeting

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of the Board of Directors, the Directors present may adjourn the meeting from time to time, without notice other than announcement at the meeting, until a quorum shall be present.

3.08    Participation of Directors by Conference Telephone. Unless otherwise restricted by the Certificate of Incorporation or these Bylaws, any member of the Board, or of any committee designated by the Board, may participate in any meeting of such Board or committee by means of conference telephone or other communications equipment by means of which all persons participating in the meeting can hear each other. Participation in any meeting by means of conference telephone or other communications equipment shall constitute presence in person at such meeting.

3.09    Written Action of Directors. Unless otherwise restricted by the Certificate of Incorporation
or these Bylaws, any action required or permitted to be taken at any meeting of the Board of Directors
or of any committee thereof may be taken without a meeting, if all members of the Board or committee, as the case may be, consent thereto in writing or by electronic transmission, and the writing or writings or electronic transmission or transmissions are filed with the minutes of proceedings of the Board or committee.

3.10    Committees. The Board of Directors may by resolution passed by a majority of the whole Board designate one or more committees, each committee to consist of two or more Directors of the Corporation. The Board may designate one or more Directors as alternate members of any committee who may replace any absent or disqualified member at any meeting of the committee. In the absence or disqualification of a member of a committee, the member or members thereof present at any meeting and not disqualified from voting, whether or not he or they constitute a quorum, may unanimously appoint another member of the Board of Directors to act at the meeting in the place of any such absent or disqualified member. The Chairman of the Board shall appoint another member of the Board of Directors to fill any committee vacancy which may occur. At all meetings of any such committee, fifty percent of the total number of committee members shall constitute a quorum for the transaction of business and the act of a majority of the committee members present at any such meeting at which there is a quorum shall be the act of any such committee, except as may be otherwise specifically provided by statute, the Certificate of Incorporation or by these Bylaws. Any such committee shall have, and may exercise, the power and authority specifically granted by the Board to the committee, but no such committee shall have the power or authority to amend the Certificate of Incorporation, adopt an agreement of merger or consolidation, recommend to the stockholders the sale, lease or exchange of the Corporation’s property and assets, recommend to the stockholders a dissolution of the Corporation or a revocation of a dissolution, or amend the Bylaws of the Corporation. Such committee or committees shall have such name or names as may be determined from time to time by resolution adopted by the Board of Directors.

3.11    Reports of Committees. Each committee shall keep regular minutes of its meetings and report the same to the Board of Directors when required.

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3.12    Compensation of Directors. Unless otherwise restricted by the Certificate of Incorporation, the Board of Directors shall have the authority to fix the compensation of Directors. The Directors may be paid their expenses, if any, of attendance at each meeting of the Board of Directors and may be paid a fixed sum for attendance at each meeting of the Board of Directors or a stated salary as Director. No such payment shall preclude any Director from serving the Corporation in any other capacity and receiving compensation therefor. Members of special or standing committees may be allowed compensation for attending committee meetings.

3.13    Chairman of the Board. The Chairman of the Board of Directors shall be chosen by the Board of Directors at its first meeting after the annual meeting of the stockholders of the Corporation. No director shall serve as Chairman of the Board who has not been determined to be independent by the Board of Directors in accordance with the director independence standards contained in the Corporate Governance Guidelines, as these provisions currently exist or may be amended. If the Board of Directors determines that a Chairman who was independent at the time of election is no longer independent, the Board shall select a new Chairman who satisfies these requirements within 60 days of such determination. The Chairman shall preside at all meetings of the Board of Directors and stockholders of the Corporation, and shall, subject to the direction and control of the Board, be its representative and medium of communication, and shall perform such duties as may from time to time be assigned to the Chairman of the Board.

NOTICES

4.01    Notices. Whenever, under the provisions of the statutes or of the Certificate of Incorporation or of these Bylaws, notice is required to be given to any Director or stockholder, it shall not be construed to mean personal notice, but such notice may be given in writing, by mail, addressed to such Director or stockholder, at his address as it appears on the records of the Corporation, with postage thereon prepaid, and such notice shall be deemed to be given at the time when the same shall be deposited in the United States mail. Notice to Directors may also be given by telephone or another form of electronic transmission in compliance with the laws of Delaware. Notice to the stockholders may also be given by a form of electronic transmission consented to by the stockholder to whom the notice is given, as provided by the laws of Delaware.

4.02    Waiver. Whenever notice is required to be given under any provision of the statutes or the Certificate of Incorporation or these Bylaws, a written waiver, signed by the person entitled to notice, or a waiver by electronic transmission by the person entitled to notice, whether before or after the time stated therein, shall be deemed equivalent to notice.

OFFICERS

5.01    Election, Qualifications. The officers of the Corporation shall be chosen by the Board of Directors at its first meeting after each annual meeting of the stockholders and shall include a President, a Chief Executive Officer, a Vice President, a Secretary, a Treasurer and a General Counsel. The Board of Directors may also choose a Vice Chairman of the Corporation, who shall report to the Chief Executive Officer,

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additional Vice Presidents, and one or more Assistant Vice Presidents, Assistant Secretaries and Assistant Treasurers. Any number of offices may be held by the same person, unless the Certificate of Incorporation or these Bylaws otherwise provide. Except for an officer serving as a Director who may serve through the first regular meeting of the Board of Directors after he has attained the age of sixty-five (65), no “high ranking executive” of the Corporation may serve in that capacity beyond the date he shall have attained the age of sixty-five (65); “high ranking executive” shall mean the President, the Chief Executive Officer, the Vice Chairman of the Corporation, any Vice President, the Secretary, the Treasurer, the General Counsel, the chief executive officers of the Corporation’s public utility divisions, and any other officer of the Corporation so designated by the Board of Directors.

5.02    Additional Officers. The Board of Directors may appoint such other officers and agents as it shall deem necessary, who shall hold their offices for such terms and shall exercise such powers and perform such duties as shall be determined from time to time by the Board.

5.03    Salaries. The salaries of all principal officers of the Corporation shall be fixed by the Board
of Directors.

5.04    Term. The officers of the Corporation shall hold office until their successors are chosen and qualify. Any officer elected or appointed by the Board of Directors may be removed at any time by the affirmative vote of a majority of the Board of Directors. Any vacancy occurring in any office of the Corporation shall be filled by the Board of Directors.

5.05    Chief Executive Officer. The Chief Executive Officer shall, subject to the authority of the Board of Directors, determine the general policies of the Corporation. The Chief Executive Officer shall submit a report of the operations of the Company for the fiscal year to the stockholders at their annual meeting and from time to time shall report to the Board of Directors all matters within his knowledge which the interests of the Corporation may require be brought to the Board’s notice.

5.06    The President. The President shall have general and active management of the business of the Corporation and shall see that all orders and resolutions of the Board of Directors are carried into effect.

5.07    The Vice Presidents. In the absence of the President or in the event of his inability or refusal to act, the Vice President (or in the event there be more than one Vice President, the Vice Presidents in the order designated, or in the absence of any designation, then in the order of their election) shall perform the duties of the President, and when so acting, shall have all the powers of and be subject to all the restrictions upon the President. The Vice Presidents shall perform such other duties and have such other powers as the Board of Directors may from time to time prescribe.

5.08    The Secretary and Assistant Secretaries. The Secretary shall record all the proceedings of the meetings of the stockholders and Directors in a book to be kept for that purpose. He shall give, or cause to be given, notice of all meetings of the stockholders and special meetings of the Board of Directors, and shall

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perform such other duties as may be prescribed by the Board of Directors or Chief Executive Officer, under whose supervision he shall be. He shall have custody of the corporate seal of the Corporation and he, or an assistant secretary, shall have authority to affix the same to any instrument requiring it. The Board of Directors may give general authority to any other officer to affix the seal of the Corporation.

The Assistant Secretary, or if there be more than one, the Assistant Secretaries in the order determined by the Board of Directors (or if there be no such determination, then in the order of their election) shall, in the absence of the Secretary or in the event of his inability or refusal to act, perform the duties and exercise the powers of the Secretary and shall perform such other duties and have such other powers as the Board of Directors may from time to time prescribe.

5.09    Treasurer and Assistant Treasurers. The Treasurer shall have the custody of the corporate funds and securities and shall keep full and accurate accounts of receipts and disbursements in books belonging to the Corporation and shall deposit all moneys and other valuable effects in the name and to the credit of the Corporation in such depositories as may be designated by the Board of Directors.

He shall disburse the funds of the Corporation as may be ordered by the Board of Directors, taking proper vouchers for such disbursements, and shall render to the President and the Board of Directors, at its regular meetings, or when the Board of Directors so requires, an account of all his transactions as Treasurer and of the financial condition of the Corporation.

If required by the Board of Directors, he shall give the Corporation a bond (which shall be renewed every six years) in such sum and with such surety or sureties as shall be satisfactory to the Board of Directors for the faithful performance of the duties of his office and for the restoration to the Corporation, in case of his death, resignation, retirement or removal from office, of all books, papers, vouchers, money and other property of whatever kind in his possession or under his control belonging to the Corporation.

The Assistant Treasurer, or if there shall be more than one, the Assistant Treasurers in the order determined by the Board of Directors (or if there be no such determination, then in the order of their election), shall, in the absence of the Treasurer or in the event of his inability or refusal to act, perform the duties and exercise the powers of the Treasurer and shall perform such other duties and have such other powers as the Board of Directors may from time to time prescribe.

5.10    General Counsel. The General Counsel shall be the legal advisor to the Corporation, the Chairman of the Board, the Chief Executive Officer, the Board of Directors and committees of the Board of Directors and provide legal counsel to all business segments of the Corporation. The General Counsel shall be responsible for the management of all legal matters involving the Corporation.

The General Counsel shall be responsible for the review of the adequacy of the Corporation’s corporate governance procedures and for reporting to senior management, the Board of Directors and committees of the Board of Directors on recommended changes, except in those instances in which such duties have been

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delegated by the Board of Directors to another officer or agent of the Corporation. The General Counsel shall have responsibility for monitoring and assessing developments in corporate governance including, but not limited to, stock exchange listing standards, legislative enactments, administrative agency regulations and judicial decisions. The General Counsel shall report to senior management, the Board of Directors and committees of the Board of Directors regarding matters of significant importance and make recommendations regarding corporate governance guidelines, policies and procedures.

5.11    Authority and Duties. In addition to the foregoing authority and duties, all officers of the Corporation shall respectively have such authority and perform such duties in the management of the business of the Corporation as may be designated from time to time by the Board of Directors.

5.12    Execution of Instruments. All deeds, bonds, mortgages, notes, contracts and other instruments shall be executed on behalf of the Corporation by the Chief Executive Officer, the President, any Vice President or Assistant Vice President, the General Counsel or such other officer or agent of the Corporation as shall be duly authorized by the Board of Directors. Any officer or agent executing any such documents on behalf of the Corporation may do so (except as otherwise required by applicable law) either under or without the seal of the Corporation and either individually or with an attestation, according to the requirements of the form of the instrument. If an attestation is required, the document shall be attested by the Secretary or an Assistant Secretary or by the Treasurer or an Assistant Treasurer or any other officer or agent authorized by the Board of Directors. When authorized by the Board of Directors, the signature of any officer or agent of the Corporation may be a facsimile.

5.13    Execution of Proxies. All capital stocks in other corporations owned by the Corporation shall be voted at the meetings, regular and/or special, of stockholders of said other corporations by the Chief Executive Officer or President of the Corporation, or, in the absence of any of them, by a Vice President, and in the event of the presence of more than one Vice President of the Corporation, then by a majority of said Vice Presidents present at such stockholder meetings, and the Chief Executive Officer or President and Secretary of the Corporation are hereby authorized to execute in the name and under the seal of the Corporation proxies in such form as may be required by the corporations whose stock may be owned by the Corporation, naming as the attorney authorized to act in said proxy such individual or individuals as said Chief Executive Officer or President and Secretary shall deem advisable, and the attorney or attorneys so named in said proxy shall, until the revocation or expiration thereof, vote said stock at such stockholder meetings only in the event that none of the officers of the Corporation authorized to execute said proxy shall be present thereat.

CERTIFICATES OF STOCK

6.01    Certificates. Shares of the Corporation’s stock may be certificated or uncertificated, as provided under Delaware law. All certificates of stock of the Corporation shall be numbered and shall be entered in the books of the Corporation as they are issued. They shall exhibit the holder’s name and number of shares

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and shall be signed by the Chairman of the Board of Directors, or the Chief Executive Officer, the President or a Vice President and by the Treasurer or an Assistant Treasurer or the Secretary or an Assistant Secretary.    

6.02    Signatures. Any of or all the signatures on the certificates may be facsimile. In case any officer, transfer agent or registrar who has signed or whose facsimile signature has been placed upon a certificate shall have ceased to be such officer, transfer agent or registrar before such certificate is issued, it may be issued by the Corporation with the same effect as if he were such officer, transfer agent or registrar at the date of issue.

6.03    Special Designation on Certificates. If the Corporation shall be authorized to issue more than one class of stock or more than one series of any class, the powers, designations, preferences and relative, participating, optional or other special rights of each class of stock or series thereof and the qualifications, limitations, or restrictions of such preferences and/or rights shall be set forth in full or summarized on the face or back of the certificate which the Corporation shall issue to represent such class or series of stock, provided, that, except as otherwise provided in Section 202 of the General Corporation Law of Delaware in lieu of the foregoing requirements, there may be set forth on the face or back of the certificate which the Corporation shall issue to represent such class or series of stock, a statement that the Corporation will furnish, without charge to each stockholder who so requests, the powers, designations, preferences and relative, participating, optional or other special rights of each class of stock or series thereof and the qualifications, limitations or restrictions of such preferences and/or rights.

6.04    Lost Certificates. The Board of Directors may direct a new certificate or certificates to be issued in place of any certificate or certificates theretofore issued by the Corporation alleged to have been lost, stolen or destroyed, upon the making of an affidavit of that fact by the person claiming the certificate of stock to be lost, stolen or destroyed. When authorizing such issue of a new certificate or certificates, the Board of Directors may, in its discretion and as a condition precedent to the issuance thereof, require the owner of such lost, stolen or destroyed certificate or certificates, or his legal representative, to advertise the same in such manner as it shall require and/or to give the Corporation a bond in such sum as it may direct as indemnity against any claim that may be made against the Corporation with respect to the certificate alleged to have been lost, stolen or destroyed.

6.05    Transfers of Stock. Transfers of stock shall be made on the books of the Corporation only by the record holder of such stock, or by attorney lawfully constituted in writing, and, in the case of stock represented by a certificate, upon surrender of the certificate.

6.06    Record Date. In order that the Corporation may determine the stockholders entitled to notice of or to vote at any meeting of stockholders or any adjournment thereof, or entitled to receive payment of any dividend or other distribution or allotment of any rights, or entitled to exercise any rights in respect of any change, conversion or exchange of stock or for the purpose of any other lawful action, the Board of Directors may fix, in advance, a record date, which shall not be more than sixty days nor less than ten days before the

16

date of such meeting, nor more than sixty days prior to any other action. A determination of stockholders of record entitled to notice of or to vote at a meeting of stockholders shall apply to any adjournment of the meeting; provided, however, that the Board of Directors may fix a new record date for the adjourned meeting.

6.07    Registered Stockholders. The Corporation shall be entitled to recognize the exclusive right of a person registered on its books as the owner of shares to receive dividends, and to vote as such owner, and to hold liable for calls and assessments a person registered on its books as the owner of shares, and shall not be bound to recognize any equitable or other claim to or interest in such share or shares on the part of any other person, whether or not it shall have express or other notice thereof, except as otherwise provided by the laws of Delaware.

GENERAL PROVISIONS

7.01    Dividends. Dividends upon the capital stock of the Corporation, subject to the provisions of the Certificate of Incorporation, if any, may be declared by the Board of Directors at any regular or special meeting, pursuant to law. Dividends may be paid in cash, in property, or in shares of the capital stock, subject to the provisions of the Certificate of Incorporation.

Before payment of any dividend, there may be set aside out of the funds of the Corporation available for dividends such sum or sums as the Directors from time to time, in their absolute discretion, think proper as a reserve or reserves for meeting contingencies, or for equalizing dividends, or for repairing or maintaining any property of the Corporation, or for such other purpose as the Directors shall think conducive to the interest of the Corporation, and the Directors may modify or abolish any such reserve in the manner in which it was created.

7.02    Checks. All checks or demands for money and notes of the Corporation shall be signed by such officer or officers or such other person or persons as the Board of Directors may from time to time designate or as designated by an officer of the company if so authorized by the Board of Directors.

7.03    Fiscal Year. The fiscal year of the Corporation shall be the calendar year.

7.04    Seal. The corporate seal shall have inscribed thereon the name of the Corporation, the year of its organization and the words “Corporate Seal, Delaware.” The seal may be used by causing it or a facsimile thereof to be impressed or affixed or imprinted, or otherwise.

7.05    Inspection of Books and Records. Any stockholder of record, in person or by attorney or other agent, shall, upon written demand under oath stating the purpose thereof, have the right, during the usual hours of business, to inspect for any proper purpose the Corporation’s stock ledger, a list of its stockholders, and its other books and records, and to make copies or extracts therefrom. A proper purpose shall mean a purpose reasonably related to such person’s interest as a stockholder. In every instance where an attorney or other agent shall be the person who seeks the right to inspection, the demand under oath shall be

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accompanied by a power of attorney or such other writing which authorizes the attorney or other agent to so act on behalf of the stockholder. The demand under oath shall be directed to the Corporation at its registered office in the State of Delaware or at its principal place of business in Bismarck, North Dakota.

7.06    Amendments. These Bylaws may be altered, amended or repealed or new Bylaws may be adopted by the stockholders or by the Board of Directors, when such power is conferred upon the
Board of Directors by the Certificate of Incorporation, at any regular meeting of the stockholders
or of the Board of Directors or at any special meeting of the stockholders or of the Board of Directors if notice of such alteration, amendment, repeal or adoption of new Bylaws be contained in the notice of such special meeting.

7.07    Indemnification of Officers, Directors, Employees and Agents.

(a)    Indemnification Granted. The Corporation shall indemnify and hold harmless, to the fullest extent permitted by applicable law as it presently exists or may hereafter be amended, any director or former director or officer or former officer of the Corporation (a “Director or Officer”) who was or is made or is threatened to be made a party or is otherwise involved in any action, suit or proceeding, whether civil, criminal, administrative or investigative (a “Proceeding”) by reason of the fact that he or she is or was a director or officer of the Corporation or is or was serving at the request of the Corporation as a director, officer, employee or agent of another corporation or of a partnership, limited liability company, joint venture, trust, non-profit entity or other enterprise, including service with respect to employee benefit plans, against expenses (including attorneys’ fees), judgments, fines, penalties, excise taxes and penalties assessed with respect to employee benefit plans, and amounts paid in settlement actually and reasonably incurred by such Director or Officer. The Corporation shall be required to indemnify a Director or Officer in connection with a Proceeding (or part thereof) initiated by such Director or Officer only if the Proceeding (or part thereof) was authorized by the Board of Directors.

(b)    Consent to Settlement or Nonadjudicated Disposition. No indemnification pursuant to this Section 7.07 shall be required with respect to any settlement or other nonadjudicated disposition of any threatened or pending Proceeding unless the Corporation has given its prior consent to such settlement or disposition.

(c)    Advancement of Expenses. The Corporation shall pay the expenses incurred by a Director or Officer in defending any Proceeding in advance of its final disposition, provided, however, that the payment of such expenses shall be made only upon receipt of an undertaking by the Director or Officer to repay all amounts advanced if it shall ultimately be determined that the Director or Officer is not entitled to be indemnified.

(d)    Claims. If a claim for indemnification (following a final full or partial disposition of a Proceeding with respect to which indemnification is sought) or advancement of expenses (including attorneys’ fees) under this Section 7.07 is not paid in full within sixty (60) days after a written claim therefor has been

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received by the Corporation, the Director or Officer may file suit to recover the unpaid amount of such claim and, if successful in whole or in part, shall be entitled to be paid the expense of prosecuting such claim, to the fullest extent permitted by applicable law. In any such action, the Corporation shall have the burden of proving that the Director or Officer was not entitled to the requested indemnification or advancement of expenses under this Section 7.07 or applicable law.

(e)    Other Indemnification and Advancement of Expenses. The Corporation may provide indemnification and advancement of expenses (including attorneys’ fees) to employees and agents to the extent permitted by applicable law.

(f)    Non-exclusivity of Rights. The rights conferred on any Director or Officer by this Section 7.07 shall not be exclusive of other rights to which such Director or Officer may have or hereafter acquire under any statute, provision of the Certificate of Incorporation, these Bylaws, agreement, vote of stockholders or disinterested directors or otherwise. Nothing in this Section 7.07 shall limit the power of the Corporation or the Board of Directors to grant indemnification and advancement of expenses, including attorneys’ fees, to directors, officers, employees and agents otherwise than pursuant to this Section 7.07.

(g)    Other Source Indemnification. The Corporation’s obligation to indemnify any Director or Officer who was or is serving at its request as a director, officer, employee or agent of another corporation or of a partnership, limited liability company, joint venture, trust, non-profit entity or other enterprise shall be reduced by any amount such Director or Officer may collect as indemnification from such other corporation, partnership, limited liability company, joint venture, trust, non-profit entity or other enterprise.

(h)    Repeal or Modification; Legal Representatives. Any repeal or modification of the foregoing provisions of this Section 7.07 shall not adversely affect any right or protection hereunder of any Director or Officer in respect of any act or omission occurring prior to the time of such repeal or modification. The rights provided to any Director or Officer by this Section 7.07 shall inure to the benefit of such Director’s or Officer’s legal representative.

7.08    Severability. If any provision of these Bylaws (or any portion, including words or phrases, thereof) or the application of any provision (or any portion, including words or phrases, thereof) to any person or circumstance shall be held invalid, illegal or unenforceable in any respect under applicable law by a court of competent jurisdiction, such invalidity, illegality or unenforceability shall not affect any other provisions hereof (or the remaining portion thereof) or the application of such provision to any other persons or circumstances, which unaffected provisions (or portions thereof) shall remain valid, legal and enforceable to the fullest extent permitted by law.

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EX-10.A

MDU RESOURCES GROUP, INC.

EXECUTIVE INCENTIVE COMPENSATION PLAN

____________________________________________________________

I.    ESTABLISHMENT AND PURPOSE

The Executive Incentive Compensation Plan (the “Plan”) was adopted by the Board of Directors of MDU Resources Group, Inc. (“MDUR”) on November 4, 1982 and subsequently amended. Effective January 1, 2012, the Plan was further amended, and the Montana-Dakota Utilities Co. Executive Incentive Compensation Plan, the MDU Construction Services Group, Inc. Executive Incentive Compensation Plan, the Knife River Corporation Executive Incentive Compensation Plan and the WBI Holdings, Inc. Executive Incentive Compensation Plan (collectively, the “Business Unit Plans”) were merged into the Plan. All awards with respect to services performed in 2011 and earlier that were earned and deferred pursuant to any of the Business Unit Plans shall be subject to the terms of the applicable Business Unit Plans in effect at the time the awards were granted. Deferral elections for awards relating to services to be performed during 2012 made pursuant to any of the Business Unit Plans shall be deemed to have been made pursuant to the Plan.

The purpose of the Plan is to provide an incentive for key executives of MDUR, its business segments, divisions and subsidiaries to focus their efforts on the achievement of corporate performance goals. The Plan is designed to reward successful performance as measured against specified performance goals. When performance reaches or exceeds the performance targets, incentive compensation awards, in conjunction with salaries, will provide a level of compensation which recognizes the skills and efforts of the key executives.

II.     DEFINITIONS

Capitalized terms not otherwise defined herein shall have the meanings given them in the Rules and Regulations.

III.    BASIC PLAN CONCEPT

The Plan provides an opportunity to earn annual incentive compensation based on the achievement of specified annual performance goals. A target incentive award for each individual within the Plan is established based on the position level and base salary (“Salary”). The target incentive award represents the amount to be paid, subject to the achievement of the performance goals established each year. Larger incentive awards than target may be authorized when performance exceeds targets; lesser or no amounts may be paid when performance is below target.

It is recognized that during a Plan Year major unforeseen changes in economic and environmental conditions or other significant factors beyond the control of management may substantially affect the ability of the Participants to achieve the specified performance goals. Therefore, in its review of performance the Administrator may modify the performance targets. However, it is contemplated that such target modifications will be necessary only in years of unusually adverse or favorable external conditions.

IV.    ADMINISTRATION

The Plan shall be administered by the Compensation Committee of the Board of Directors of MDUR (the “Administrator”). The Compensation Committee of the Board of Directors of MDUR shall adopt Rules and Regulations for the administration of the Plan. With respect to employees who are not subject to Section 16 of the Securities Exchange Act of 1934, as amended, the Chief Executive Officer of MDUR, with respect to MDUR employees, and

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the chief executive officer of each business segment, in conjunction with the Chief Executive Officer of MDUR, with respect to the business segment’s employees, shall be the Administrator.

The Administrator shall approve the list of eligible Participants and the target incentive award level for each position within the Plan. The Plan’s performance targets for the year shall be approved by the Administrator no later than 90 days after the beginning of that Plan Year. The Administrator shall have final discretion to determine actual award payment levels, method of payment, and whether or not payments shall be made for any Plan Year.

The Board of Directors of MDUR may, at any time and from time to time, alter, amend, supersede or terminate the Plan in whole or in part, provided that no termination, amendment or modification of the Plan shall adversely affect in any material way an award that has met all requirements for payment without the written consent of the Participant holding such award, unless such termination, modification or amendment is required by applicable law.

V.    ELIGIBILITY

Executives who are determined by the Administrator to have a key role in both the establishment and achievement of their company’s objectives shall be eligible to participate in the Plan.

Nothing in the Plan shall interfere with or limit in any way the right of an employer to terminate any Participant’s employment at any time, for any reason or no reason in its sole discretion, or confer upon any Participant any right to remain employed by the employer. No executive shall have the right to be selected to receive an award under the Plan, or, having been so selected, to be selected to receive a future award.

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VI.    PLAN PERFORMANCE MEASURES

Performance measures shall be established that consider shareholder and/or customer interests. These measures shall be evaluated annually based on achievement of specified goals.

The performance measures will be determined by the Administrator. These measures may be applied at the MDUR level, the business segment level and/or a division or subsidiary level. The Administrator may assign different performance measures and/or different weights to performance measures for each Participant.

The Administrator may establish threshold, target and/or maximum award levels annually for some or all of the performance measures. The Administrator will retain the right to make all interpretations as to the actual attainment of the desired results and will determine whether any circumstances beyond the control of management need to be considered.

VII.    TARGET INCENTIVE AWARDS

Target incentive awards will be expressed as a percentage of each Participant’s Salary. These percentages shall vary by position and reflect larger reward opportunity for positions having greater effect on the establishment and accomplishment of the corporate objectives. A schedule showing the target awards as a percentage of Salary for eligible positions will be prepared for each Plan Year.

VIII.    INCENTIVE FUND DETERMINATION

The target incentive fund is the sum of the individual target incentive awards for all eligible Participants. Once the incentive targets have been determined by the Administrator, a target incentive fund shall be established and accrued ratably by MDUR and each of its business segments, divisions and/or

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subsidiaries, as applicable. The incentive fund and accruals may be adjusted during the year.

At the close of each Plan Year, the Chief Executive Officer of MDUR will cause to be prepared an analysis showing performance in relation to each of the performance measures employed. This will be provided to the Administrator for review and comparison to threshold, target and/or maximum, if applicable, performance levels. In addition, any recommendations of the Chief Executive Officer of MDUR or the Administrator will be presented at this time. The Administrator will then determine the amount of the target incentive fund earned.

IX.    INDIVIDUAL AWARD DETERMINATION

Each individual Participant's award will be based upon the level of performance achieved relative to the established performance measures, as determined by a percentage from 0 percent to a maximum of 250 percent, as determined by the Administrator.

X.    PAYMENT OF AWARDS

Except as provided below or as otherwise determined by the Administrator, in order to receive an award under the Plan, the Participant must remain in the employment of the Participant’s employer for the entire Service Year. If a Participant terminates employment with MDUR pursuant to Section 5.01 of MDUR’s Bylaws which provides for mandatory retirement for certain officers on their 65th birthday (or terminates employment with a business segment, division and/or subsidiary of MDUR pursuant to a similar company Bylaw provision) and if the Participant’s 65th birthday occurs during the Service Year, determination of whether the performance measures have been met will be made at the end of the Service Year, and to the extent met, payment of the award will be made to the Participant, prorated. Proration of awards

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shall be based upon the number of full months elapsed from and including January to and including the month in which the Participant’s 65th birthday occurs. The prorated award shall be paid as soon as practicable in the year following the Service Year, but in all events between January 1 and March 10.

A Participant who transfers between the Participant’s employer at the time the award is granted and MDUR or any of its business segments, divisions or subsidiaries may receive a prorated award at the discretion of the Administrator.

Payments made under the Plan will not be considered part of compensation for pension purposes. Payments will be made in cash as soon as practicable in the year following the Service Year, but in all events between January 1 and March 10.

To the extent approved by the Administrator of the Plan with respect to executives of MDUR, its business segments, divisions or subsidiaries, as applicable, incentive awards may be deferred if the appropriate elections have been executed prior to the beginning of the Service Year. A deferral election will be effective only for the incentive award earned in the Service Year following the Plan Year in which the election is made. Deferral elections may not be changed or revoked after the Service Year begins. Deferred amounts shall be subject to the terms of the Plan and the Rules and Regulations and, to the extent not inconsistent therewith, the deferral election forms pursuant to which the amounts were deferred. Deferred amounts will accrue interest at a rate determined annually by the Compensation Committee of the Board of Directors of MDUR and specified in the Rules and Regulations.

In the event of a "Change in Control" (as defined in the Rules and Regulations) then any award deferred by each Participant shall become immediately payable to the Participant in cash, together with accrued interest thereon to the date of payment. In the event the Participant files suit to collect the

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Participant's deferred award then all of the court costs, other expenses of litigation, and attorneys' fees shall be paid by MDUR or one of its business segments, divisions or subsidiaries, as applicable, in the event the Participant prevails upon any of the Participant's claims for payment of a deferred award.

XI.    ACCOUNTING RESTATEMENTS

This Section XI shall apply to incentive awards granted to all Participants in the Plan. Notwithstanding anything in the Plan or the Rules and Regulations to the contrary, if MDUR’s audited financial statements are restated, the Compensation Committee of the Board of Directors of MDUR (the “Compensation Committee”) may, in accordance with its Guidelines for Repayment of Incentives Due to Accounting Restatements, take such actions as it deems appropriate (in its sole discretion) with respect to

(a)    unpaid incentive awards under the Plan (including incentive awards relating to completed Plan Years, but with respect to which payments have not yet been made or deferred) ("Outstanding Awards") and

(b)    prior incentive awards that were paid (or deferred) within the three-year period preceding the restatement ("Prior Awards"), provided such Prior Awards were not paid prior to the date the Plan was amended to add this Section XI,

if the calculation of the amounts payable, paid or deferred under such awards are, or would have been, directly impacted by the restatement, including, without limitation, (i) securing (or causing to be secured) repayment of some or all payments made pursuant to (or deferrals relating to) Prior Awards, (ii) making (or causing to be made) additional payments (or crediting additional deferrals), (iii) reducing or otherwise adjusting the amount payable pursuant to Outstanding Awards and/or (iv) causing the forfeiture of Outstanding Awards. The Compensation Committee

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may, in its sole discretion, take different actions pursuant to this Section XI with respect to different awards, different Participants (or beneficiaries) and/or different classes of awards or Participants (or beneficiaries). The Compensation Committee has no obligation to take any action permitted by this Section XI. The Compensation Committee may consider any factors it chooses in taking (or determining whether to take) any action permitted by this Section XI, including, without limitation, the following:

(A)    The reason for the restatement of the financial statements;

(B)    The amount of time between the initial publication and subsequent restatement of the financial statements; and

(C)    The Participant's current employment status, and the viability of successfully obtaining repayment.

If the Compensation Committee requires repayment of all or part of a Prior Award, the amount of repayment may be based on, among other things, the difference between the amount paid to the individual and the amount that the Compensation Committee determines in its sole discretion should have been paid based on the restated results. The Compensation Committee shall determine whether repayment shall be effected (i) by seeking repayment from the Participant, (ii) by reducing (subject to applicable law and the terms and conditions of the applicable plan, program or arrangement) the amount that would otherwise be provided to the Participant under any compensatory plan, program or arrangement maintained by MDUR or any of its business segments, divisions or subsidiaries, (iii) by withholding payment of future increases in compensation (including the payment of any discretionary bonus amount) or grants of compensatory awards that would otherwise have been made in accordance with otherwise applicable compensation practices of MDUR or its business segments, divisions or subsidiaries, as applicable, or (iv) by any

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combination of the foregoing. Additionally, by accepting an incentive award under the Plan, Participants acknowledge and agree that the Compensation Committee may take any actions permitted by this Section XI with respect to Outstanding Awards to the extent repayment is to be made pursuant to another plan, program or arrangement maintained by MDUR or any of its business segments, divisions or subsidiaries.

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MDU RESOURCES GROUP, INC.

EXECUTIVE INCENTIVE COMPENSATION PLAN

RULES AND REGULATIONS

The Compensation Committee of the Board of Directors of MDU Resources Group, Inc. (“MDUR”) adopted Rules and Regulations for the administration of the Executive Incentive Compensation Plan (the "Plan") on February 9, 1983, following adoption of the Plan by the Board of Directors of MDUR on November 4, l982, which Rules and Regulations were subsequently amended and are hereby further amended effective January 1, 2013.

I. DEFINITIONS

The following definitions shall be used for purposes of these Rules and Regulations and for the purpose of administering the Plan:

1. The “Administrator” shall be the Compensation Committee of the Board of Directors of MDUR with respect to employees subject to Section 16 of the Securities Exchange Act of 1934, as amended. With respect to employees who are not subject to Section 16, the Chief Executive Officer of MDUR, with respect to MDUR employees, and the chief executive officer of each business segment, in conjunction with the Chief Executive Officer of MDUR, with respect to the business segment’s employees, shall be the Administrator.

2. "Change in Control" shall mean the occurrence of any of the following transactions or events: (a) any person (which shall not include MDUR, any subsidiary of MDUR or any employee benefit plan of MDUR or of any subsidiary of MDUR) ("Person") or group (as that term is defined in Treasury Regulation Section 1.409A-3(i)(5)(v)(B)), acquires (or has acquired during the 12-month period ending on the date of the most recent acquisition by such Person or Persons) ownership of stock of MDUR possessing 30% or more of the total voting power of the stock of MDUR; (b) any Person or group (as that term is defined in Treasury Regulation Section 1.409A-3(i)(5)(v)(B)), acquires ownership of the stock of MDUR that, together with stock held by such Person or group, constitutes more

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than 50% of the total fair market value or total voting power of the stock of MDUR (this part (b) applies only when there is a transfer of stock of MDUR and MDUR's stock remains outstanding after the transaction); (c) a majority of the members of the Board of Directors of MDUR is replaced during any 12-month period by directors whose appointment or election is not endorsed by a majority of the members of the Board of Directors of MDUR; or (d) any Person or group (as that term is defined in Treasury Regulation Section 1.409A-3(i)(5)(v)(B)), acquires (or has acquired during the 12-month period ending on the date of the most recent acquisition by such Person or Persons) assets from MDUR that have a gross fair market value equal to or more than 40% of the total gross fair market value of all of the assets of MDUR immediately before such acquisition or acquisitions.

Notwithstanding anything contained herein to the contrary, no transaction or event shall constitute a Change in Control for purposes of the Plan unless the transaction or event constitutes a change in the ownership of a corporation (as defined in Treasury Regulation Section 1.409A-3(i)(5)(v)), a change in effective control of a corporation (as defined in Treasury Regulation Section 1.409A-3(i)(5)(vi)) or a change in the ownership of a substantial portion of the assets of a corporation (as defined in Treasury Regulation Section 1.409A-3(i)(5)(vii)) and the term Change in Control shall be interpreted in a manner consistent with the proper interpretation of the similar provisions in the Section 409A Treasury Regulations.

3. The “Code” shall mean the Internal Revenue Code of 1986, as amended.

4. The “Compensation Committee” shall be the Compensation Committee of the Board of Directors of MDUR.

5. "MDUR" shall refer to MDU Resources Group, Inc. alone and shall not refer to any of its business segments, divisions or subsidiaries.

6. The "Moody's Rate" is defined as the average of (i) the number that results from adding the daily Moody’s U.S. Long-Term Corporate Bond Yield

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Average for “A” rated companies as of the last day of each month for the 12-month period ending October 31 and dividing by 12 and (ii) the number that results from adding the daily Moody’s U.S. Long-Term Corporate Bond Yield Average for “BBB” rated companies as of the last day of each month for the 12-month period ending October 31 and dividing by 12.

7. "Participants" for any Plan Year shall be those executives who have been approved by the Administrator as eligible for participation in the Plan for such Plan Year.

8. "Payment Date" shall be the date set by the Administrator for payment of awards pursuant to Section X of the Plan, other than those awards deferred pursuant to Section X of the Plan and Section VII of these Rules and Regulations.

9. The "Plan" shall refer to the Executive Incentive Compensation Plan, as it has been and may be amended.

10. The "Plan Year" shall be the calendar year.

11. “Retirement” means the later of the day the Participant attains age 55 or the day the Participant ceases to be an employee of MDUR or any of its business segments, divisions or subsidiaries.

12. “Service Year” means the Plan Year during which the services giving rise to the incentive award are performed.

13. “Specified Employee” means an employee who, as of the date the employee separates from service, is a “specified employee” (as that term is used in Section 409A(a)(2)(B) of the Code), as determined under MDUR's policy for determining specified employees.

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II. ADMINISTRATION

1. The Compensation Committee shall have the full power to construe and interpret the Plan and to establish and to amend these Rules and Regulations for its administration.

2. The Administrator shall not participate in a decision as to the Administrator’s eligibility for, or award of, an incentive award payment.

3. For each Plan Year, the Administrator shall approve a list of eligible executives and notify those so approved that they are eligible to participate in the Plan for such Plan Year.

4. No later than 90 days after the beginning of each Plan Year, the Administrator shall approve the Plan’s performance measures, performance targets and target incentive award levels for each salary grade covered by the Plan for the Plan Year.

5. The Administrator shall have final discretion to determine actual award payment levels, method of payment, and whether or not payments shall be made for any Plan Year. However, unless the Plan's performance goals are met for the Plan Year, no award shall be made for that Plan Year. Performance targets modified pursuant to Section III of the Plan will be deemed performance targets for purposes of determining whether or not these targets have been met.

III.    PLAN PERFORMANCE MEASURES

1. The Administrator shall establish the percentage attainment of performance measures. The Administrator may establish more or fewer performance measures as it deems necessary.

2. The performance measures may be set by reference to earnings, return on invested capital or any other measure or combination of measures deemed appropriate by the Administrator. They may be established for MDUR or any of its business segments, divisions or subsidiaries. The Administrator may assign different performance measures and/or different weights to performance measures for each Participant.

3. The Administrator shall cause to be prepared a list of individuals to whom the Plan performance measures will be applied and shall identify the applicable performance measures for each Participant, which may vary among Participants.

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4. The Administrator may set threshold, target and/or maximum award levels for some or all of the performance measures, and those levels shall be included on the list referred to in paragraph 3 above.

5. The Administrator will retain the authority to determine whether or not the actual attainment of these measures has been made.

IV.    TARGET INCENTIVE AWARDS

1. Target incentive awards will be a percentage of each Participant’s Salary, as defined in the Plan.

2. Target incentive awards shall be set by the Administrator annually and will be included on the list referred to above.

V.    INCENTIVE FUND DETERMINATION

1. The target incentive fund is the sum of the individual target incentive awards for all eligible Participants.

2. Once individual incentive targets have been determined, a target incentive fund shall be established and accrued ratably by MDUR and each of its business segments, divisions and/or subsidiaries, as applicable. The incentive fund and accruals may be adjusted during the year.

3. As soon as practicable following the close of each Plan Year, the Chief Executive Officer of MDUR will cause to be prepared an analysis showing performance in relation to the performance measures. The Administrator will review the analysis and determine, in its sole discretion, the amount of the actual incentive fund.

4. In determining the actual incentive fund, any recommendations of the Chief Executive Officer of MDUR or the Administrator will be considered.

VI.    INDIVIDUAL AWARD DETERMINATION

1. The Administrator shall have the sole discretion to determine each individual Participant's award.

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The Administrator's decision will be based upon the level of performance achieved.

2. Each individual Participant’s award will be based upon the level of performance achieved relative to the established performance measures, as determined by a percentage from 0 percent to a maximum of 250 percent, as determined by the Administrator.

VII.    PAYMENT OF AWARDS

1. On the date the Administrator determines the awards to be made to individual Participants, it shall also establish the Payment Date.

2. Except as provided below or in the Plan or as the Administrator otherwise determines, in order to receive an award under the Plan, a Participant must remain in the employment of the Participant’s employer for the entire Service Year.

3. If a Participant terminates employment with MDUR pursuant to Section 5.01 of MDUR’s Bylaws, which provides for mandatory retirement for certain officers on their 65^th birthday (or terminates employment with a business segment, division and/or subsidiary of MDUR pursuant to a similar company Bylaw provision), and if the Participant’s 65^th birthday occurs during the Service Year, determination of whether the performance measures have been met will be made at the end of the Service Year, and to the extent met, payment of the award will be made to the Participant, prorated. Proration of awards shall be based upon the number of full months elapsed from and including January to and including the month in which the Participant’s 65^th birthday occurs.

4. Payment of the awards shall be made in cash. Payments shall be made on the Payment Date unless the Participant has deferred, in whole or in part, the receipt of the award by making an election on the deferral form attached hereto, prior to the beginning of the Service Year. Deferral elections may not be changed or revoked after the Service Year begins.

MDUR - 15

5. In the event a Participant has elected to defer receipt of all or a portion of the award, MDUR or one of its business segments, divisions or subsidiaries, as applicable shall set up an account in the Participant's name. The amount of the Participant's award to the extent deferred will be credited to the Participant's account on the Payment Date.

6. The balance credited to an account of a Participant who has elected to defer receipt of an award will be an unsecured, unfunded obligation of MDUR or one of its business segments, divisions or subsidiaries, as applicable.

7. Interest shall accrue on the balance credited to a Participant's account from the date the balance is credited. The rate of interest for each Plan Year shall be the Moody’s Rate.

8. Interest shall be compounded and credited to the account monthly.

9. A Participant may elect to defer any percentage, not to exceed l00, of an annual award.

10. A Participant electing to defer any part of an award must elect one of the following dates on which (a) payment will be made, if payment will be made in a lump sum or (b) payments will commence, if payment will be made in monthly installments:

(1) Between January 1 and March 10 next following termination of employment with MDUR, its business segments, divisions and subsidiaries, as applicable; or

(2) Between January 1 and March 10 of the fifth year following the year in which the award would have been paid had it not been deferred.

For Participants who previously elected to have payments made or commence on the Payment Date next following termination of employment, their payments will be made or commence between January 1 and March 10 next following their termination of employment with MDUR, its business segments, divisions and subsidiaries, as applicable. For Participants who elected to have payments made or

MDUR - 16

commence on the Payment Date of the fifth year following the year in which the award may be made, their payments will be made or commence between January 1 and March 10 of the fifth year following the year in which the award would have been paid had it not been deferred.

11. A Participant may elect to receive the deferred amounts accumulated in the Participant's account in monthly installments, not to exceed 120. In the event the Participant elects to receive the amounts in the Participant's account in more than one installment, interest shall continue to accrue on the balance remaining in their account at the applicable rate or rates determined annually by the Compensation Committee.

12. Notwithstanding anything contained in the Plan or these Rules and Regulations to the contrary, if a Specified Employee's employment terminates, to the extent required by Section 409A(a)(2)(B) of the Code, except as otherwise provided in paragraph 13 below of this Section VII of these Rules and Regulations, payment of any deferred amounts under the Plan that are to be paid during the 6-month period following the Specified Employee's termination of employment shall not be paid or provided until the first business day after the date that is 6 months following the Specified Employee's termination of employment. Any payment that is made pursuant to the prior sentence shall include the cumulative amount of any amounts that could not be paid during the 6-month period following the Specified Employee's termination of employment. To the extent payments are deferred pursuant to the prior sentence, such deferred amounts shall continue to accrue interest pursuant to Section VII of these Rules and Regulations until payment occurs.

For all purposes under the Plan and these Rules and Regulations, references to termination of employment and similar terms shall be interpreted to mean “separation from service,” as that term is used in Section 409A of the Code, and the Participant's employment shall not be deemed to have terminated for purposes of the Plan or these Rules and Regulations unless and until a separation from service shall have occurred for purposes of Section 409A of the Code.

13. In the event of the death of a Participant in whose name a deferred account has been set up, MDUR or one of its business segments, divisions or subsidiaries, as applicable, shall, within 90 days thereafter, pay to the Participant's estate or the designated beneficiary the entire amount in the deferred account.

14. In the event of a "Change in Control" then any award deferred by each Participant shall become immediately payable to the Participant. In the event the Participant files suit to collect a deferred award then all of the Participant's court costs, other expenses of litigation, and attorneys' fees shall be paid by MDUR or one of its business segments, divisions or subsidiaries, as applicable, in the event the Participant prevails upon any of the Participant's claims for payment.

MDUR - 17

PAYROLL ELECTION FORM

Election for Deferred Compensation

and Beneficiary Designation

Pursuant to the MDU Resources Group, Inc. Executive Incentive Compensation Plan and the MDU Resources Group, Inc. Executive Incentive Compensation Plan Rules and Regulations (the "Plan"), I elect to defer receipt of

_______________________________ percent of the cash portion of any award which may be

(not to exceed 100)

payable to me in [ ] for Plan Year incentive earned in [ ], until the event specified below:

Check one:

Between January 1 and March 10 of the year following the year my employment with MDU Resources Group, Inc., its business segments, division

_________________and subsidiaries, as applicable is terminated.

Between January 1 and March 10 of [ ] the fifth year following the year in

__________________which the award would have been paid had it not been deferred).

I elect to receive any amounts deferred pursuant to the designation above and accumulated in my account in

___________________________ monthly installments; provided, however,

(not to exceed 120)

that in the event of a Change in Control (as defined in the Plan) all amounts deferred shall become immediately payable in cash, together with accrued interest thereon to the date of payment.

In the event of my death prior to receipt of the balance of such accumulated amounts, I designate

___________________________________________________________________ whose address is

___________________________________________________________________ as my beneficiary

to receive such balance.

MDUR - 18

I understand that this election shall become irrevocable on December 31,[ ]. I further understand that (1) if I am a “specified employee” (as that term is used in Section 409A of the Internal Revenue Code of 1986, as amended (the “Code”)) when my employment terminates, to the extent required by Section 409A(a)(2)(B), payment of any deferred amounts under the Plan that are subject to Section 409A of the Code and that are to be paid during the 6 month period following my termination of employment shall not be paid or provided until the first business day after the date that is 6 months following termination of my employment or, if earlier, within 90 days after my death and (2) for purposes of this election form, I shall not be deemed to have terminated employment with MDU Resources Group, Inc. or an affiliated company unless and until a "separation from service" (as that term is used in Section 409A of the Code) shall have occurred. Any payment with respect to any deferred amounts paid out in installment payments shall be treated as a series of separate payments for purposes of Section 409A of the Code.

I am aware that this election is being made under the Plan and that this election is governed by the Plan. I acknowledge that this election and the Plan together constitute an agreement between the Company and me, which can only be revoked or changed as provided in the Plan.

(Print Name)	(Signature)
	(Date)

MDUR - 19

MDUR - 20

EX-12

MDU RESOURCES GROUP, INC.

COMPUTATION OF RATIO OF EARNINGS TO FIXED CHARGES

AND COMBINED FIXED CHARGES AND PREFERRED STOCK DIVIDENDS

	Twelve Months Ended March 31, 2013					Year Ended December 31, 2012
	(In thousands of dollars)
Earnings Available for Fixed Charges:
Net Income (a)		$	5,858				$	(14,939	)
Income Taxes		(21,229		)			(31,146		)
		(15,371		)			(46,085		)
Rents (b)		14,705					13,716
Interest (c)		85,866					83,781
Total Earnings Available for Fixed Charges		$	85,200				$	51,412
Preferred Dividend Requirements		$	685				$	685
Ratio of Income Before Income Taxes to Net Income		N/M					308		%
Preferred Dividend Factor on Pretax Basis		685					2,110
Fixed Charges (d)		101,759					100,516
Combined Fixed Charges and Preferred Stock Dividends		$	102,444				$	102,626
Ratio of Earnings to Fixed Charges		—			(e)		—			(e)
Ratio of Earnings to Combined Fixed Charges and Preferred Stock Dividends		—			(e)		—			(e)

N/M Not Meaningful

(a) Net income excludes undistributed income for equity investees.

(b) Represents interest portion of rents estimated at 33 1/3%.

(c) Represents interest, amortization of debt discount and expense on all indebtedness and amortization of interest capitalized, and excludes amortization of gains or losses on reacquired debt (which, under the Federal Energy Regulatory Commission Uniform System of Accounts, is classified as a reduction of, or increase in, interest expense in the Consolidated Statements of Income) and interest capitalized.

(d) Represents rents (as defined above), interest, amortization of debt discount and expense on all indebtedness, and excludes amortization of gains or losses on reacquired debt (which, under the Federal Energy Regulatory Commission Uniform System of Accounts, is classified as a reduction of, or increase in, interest expense in the Consolidated Statements of Income).

(e) Due to the $246.8 million after-tax noncash write-downs of oil and natural gas properties in 2012, earnings were insufficient by $17.2 million and $51.2 million to cover fixed charges for the 12 months ended March 31, 2013 and December 31, 2012, respectively. If the $246.8 million after-tax noncash write-downs were excluded, the ratio of earnings to fixed charges and the ratio of earnings to combined fixed charges and preferred stock dividends would have been 4.7 times and 4.6 times for the twelve months ended March 31, 2013, respectively, and would both have been 4.4 times for the twelve months ended December 31, 2012.

The above ratios related to fixed charges and combined fixed charges and preferred stock dividends that exclude the effect of after-tax noncash write-downs of oil and natural gas properties are non-GAAP financial measures. The Company believes that these non-GAAP financial measures are useful because the write-downs excluded are not indicative of the Company's cash flows available to meet its fixed charges obligations. The presentation of this additional information is not meant to be considered a substitute for financial measures prepared in accordance with GAAP.

EX-31.A

CERTIFICATION

I, David L. Goodin, certify that:

1. I have reviewed this quarterly report on Form 10-Q of MDU Resources Group, Inc.;

2. Based on my knowledge, this report does not contain any untrue statement of a material fact or omit to state a material fact necessary to make the statements made, in light of the circumstances under which such statements were made, not misleading with respect to the period covered by this report;

3. Based on my knowledge, the financial statements, and other financial information included in this report, fairly present in all material respects the financial condition, results of operations and cash flows of the registrant as of, and for, the periods presented in this report;

4. The registrant's other certifying officer and I are responsible for establishing and maintaining disclosure controls and procedures (as defined in Exchange Act Rules 13a-15(e) and 15d-15(e))and internal control over financial reporting (as defined in Exchange Act Rules 13a-15(f) and 15d-15(f)) for the registrant and have:

(a)Designed such disclosure controls and procedures, or caused such disclosure controls and procedures to be designed under our supervision, to ensure that material information relating to the registrant, including its consolidated subsidiaries, is made known to us by others within those entities, particularly during the period in which this report is being prepared;

(b)Designed such internal control over financial reporting, or caused such internal control over financial reporting to be designed under our supervision, to provide reasonable assurance regarding the reliability of financial reporting and the preparation of financial statements for external purposes in accordance with generally accepted accounting principles;

(c)Evaluated the effectiveness of the registrant's disclosure controls and procedures and presented in this report our conclusions about the effectiveness of the disclosure controls and procedures, as of the end of the period covered by this report based on such evaluation; and

(d)Disclosed in this report any change in the registrant's internal control over financial reporting that occurred during the registrant's most recent fiscal quarter (the registrant's fourth fiscal quarter in the case of an annual report) that has materially affected, or is reasonably likely to materially affect, the registrant's internal control over financial reporting; and

5. The registrant's other certifying officer and I have disclosed, based on our most recent evaluation of internal control over financial reporting, to the registrant's auditors and the audit committee of the registrant's board of directors (or persons performing the equivalent functions):

(a)All significant deficiencies and material weaknesses in the design or operation of internal control over financial reporting which are reasonably likely to adversely affect the registrant's ability to record, process, summarize and report financial information; and

(b)Any fraud, whether or not material, that involves management or other employees who have a significant role in the registrant's internal control over financial reporting.

Date:  May 7, 2013

/s/ David L. Goodin

David L. Goodin

President and Chief Executive Officer

EX-31.B

CERTIFICATION

I, Doran N. Schwartz, certify that:

1. I have reviewed this quarterly report on Form 10-Q of MDU Resources Group, Inc.;

2. Based on my knowledge, this report does not contain any untrue statement of a material fact or omit to state a material fact necessary to make the statements made, in light of the circumstances under which such statements were made, not misleading with respect to the period covered by this report;

3. Based on my knowledge, the financial statements, and other financial information included in this report, fairly present in all material respects the financial condition, results of operations and cash flows of the registrant as of, and for, the periods presented in this report;

4. The registrant's other certifying officer and I are responsible for establishing and maintaining disclosure controls and procedures (as defined in Exchange Act Rules 13a-15(e) and 15d-15(e))and internal control over financial reporting (as defined in Exchange Act Rules 13a-15(f) and 15d-15(f)) for the registrant and have:

(a)Designed such disclosure controls and procedures, or caused such disclosure controls and procedures to be designed under our supervision, to ensure that material information relating to the registrant, including its consolidated subsidiaries, is made known to us by others within those entities, particularly during the period in which this report is being prepared;

(b)Designed such internal control over financial reporting, or caused such internal control over financial reporting to be designed under our supervision, to provide reasonable assurance regarding the reliability of financial reporting and the preparation of financial statements for external purposes in accordance with generally accepted accounting principles;

(c)Evaluated the effectiveness of the registrant's disclosure controls and procedures and presented in this report our conclusions about the effectiveness of the disclosure controls and procedures, as of the end of the period covered by this report based on such evaluation; and

(d)Disclosed in this report any change in the registrant's internal control over financial reporting that occurred during the registrant's most recent fiscal quarter (the registrant's fourth fiscal quarter in the case of an annual report) that has materially affected, or is reasonably likely to materially affect, the registrant's internal control over financial reporting; and

5. The registrant's other certifying officer and I have disclosed, based on our most recent evaluation of internal control over financial reporting, to the registrant's auditors and the audit committee of the registrant's board of directors (or persons performing the equivalent functions):

(a)All significant deficiencies and material weaknesses in the design or operation of internal control over financial reporting which are reasonably likely to adversely affect the registrant's ability to record, process, summarize and report financial information; and

(b)Any fraud, whether or not material, that involves management or other employees who have a significant role in the registrant's internal control over financial reporting.

Date:  May 7, 2013

/s/ Doran N. Schwartz

Doran N. Schwartz

Vice President and Chief Financial Officer

EX-32

CERTIFICATION PURSUANT TO 18 U.S.C. SECTION 1350,

AS ADOPTED PURSUANT TO SECTION 906

OF THE SARBANES-OXLEY ACT OF 2002

Each of the undersigned, David L. Goodin, the President and Chief Executive Officer, and Doran N. Schwartz, the Vice President and Chief Financial Officer of MDU Resources Group, Inc. (the "Company"), DOES HEREBY CERTIFY that:

1.  The Company's Quarterly Report on Form 10-Q for the quarter ended March 31, 2013 (the "Report"), fully complies with the requirements of Section 13(a) of the Securities Exchange Act of 1934; and

2.  Information contained in the Report fairly presents, in all material respects, the financial condition and results of operations of the Company.

IN WITNESS WHERE OF, each of the undersigned has executed this statement this 7th day of May, 2013.

/s/ David L. Goodin

David L. Goodin

President and Chief Executive Officer

/s/ Doran N. Schwartz

Doran N. Schwartz

Vice President and Chief Financial Officer

A signed original of this written statement required by Section 906 has been provided to MDU Resources Group, Inc. and will be retained by MDU Resources Group, Inc. and furnished to the Securities and Exchange Commission or its staff upon request.

EX-95

MDU RESOURCES GROUP, INC.

MINE SAFETY INFORMATION

The Dodd-Frank Wall Street Reform and Consumer Protection Act (Dodd-Frank Act) requires issuers to include in periodic reports filed with the SEC certain information relating to citations or orders for violations of standards under the Federal Mine Safety and Health Act of 1977 (Mine Act), as amended by the Mine Improvement and New Emergency Response Act of 2006 (Mine Safety Act). The Dodd-Frank Act requires reporting of the following types of citations or orders:

1. Citations issued under Section 104 of the Mine Safety Act for violations that could significantly and substantially contribute to the cause and effect of a coal or other mine safety or health hazard.

2. Orders issued under Section 104(b) of the Mine Safety Act. Orders are issued under this section when citations issued under Section 104 have not been totally abated within the time period allowed by the citation or subsequent extensions.

3. Citations or orders issued under Section 104(d) of the Mine Safety Act. Citations or orders are issued under this section when it has been determined that the violation is caused by an unwarrantable failure of the mine operator to comply with the standards. An unwarrantable failure occurs when the mine operator is deemed to have engaged in aggravated conduct constituting more than ordinary negligence.

4. Citations issued under Section 110(b)(2) of the Mine Safety Act for flagrant violations. Violations are considered flagrant for repeat or reckless failures to make reasonable efforts to eliminate a known violation of a mandatory health and safety standard that substantially and proximately caused, or reasonably could have been expected to cause, death or serious bodily injury.

5. Imminent danger orders issued under Section 107(a) of the Mine Safety Act. An imminent danger is defined as the existence of any condition or practice in a coal or other mine which could reasonably be expected to cause death or serious physical harm before such condition or practice can be abated.

6. Notice received under Section 104(e) of the Mine Safety Act of a pattern of violations or the potential to have such a pattern of violations that could significantly and substantially contribute to the cause and effect of mine health and safety standards.

During the three months ended March 31, 2013, none of the Company's operating subsidiaries received citations or orders under the following sections of the Mine Safety Act: 104(b), 104(d), 107(a), 110(b)(2) or 104(e). In addition, the Company did not have any mining-related fatalities during this period.

1

MSHA Identification Number	Section 104 S&S Citations (#)	Total Dollar Value of MSHA Assessments Proposed ($)		Legal Actions Pending as of Last Day of Period (#)	Legal Actions Initiated During Period (#)	Legal Actions Resolved During Period (#)
04-00081	—	$	—	4	—	—
04-01698	—	1,000		3	—	2
04-05140	—	—		3	—	—
10-02089	—	100		—	—	1
21-00462	—	—		1	—	—
21-03133	—	100		—	—	—
21-03416	—	200		—	—	—
21-03560	—	100		—	—	—
24-02022	1	290		1	1	—
24-02414	—	100		1	1	—
35-00495	—	390		—	—	—
35-02968	—	500		—	—	—
35-03022	1	—		—	—	—
35-03449	—	—		—	—	5
35-03478	—	300		—	—	—
35-03581	—	200		—	—	—
35-03667	1	100		3	—	—
41-02639	—	—		—	—	1
41-03931	—	100		—	—	—
48-01383	—	2,369		4	4	—
51-00036	5	6,801		4	4	—
51-00171	—	100		—	—	—
51-00195	—	100		—	—	—
51-00241	—	100		—	—	—
	8	$	12,950	24	10	9

Legal actions pending before the Federal Mine Safety and Health Review Commission (the Commission) may involve, among other questions, challenges by operators to citations, orders and penalties they have received from the Federal Mine Safety and Health Administration (MSHA) or complaints of discrimination by miners under section 105 of the Mine Act. The following is a brief description of the types of legal actions that may be brought before the Commission.

• Contests of Citations and Orders - A contest proceeding may be filed with the Commission by operators, miners or miners' representatives to challenge the issuance of a citation or order issued by MSHA.

• Contests of Proposed Penalties (Petitions for Assessment of Penalties) - A contest of a proposed penalty is an administrative proceeding before the Commission challenging a civil penalty that MSHA has proposed for the alleged violation contained in a citation or order.

• Complaints for Compensation - A complaint for compensation may be filed with the Commission by miners entitled to compensation when a mine is closed by certain withdrawal orders issued by MSHA. The purpose of the proceeding is to determine the amount of compensation, if any, due miners idled by the orders.

• Complaints of Discharge, Discrimination or Interference - A discrimination proceeding is a case that involves a miner's allegation that he or she has suffered a wrong by the operator because he or she engaged in some type of activity protected under the Mine Act, such as making a safety complaint.

• Applications for Temporary Relief - Applications for temporary relief from any modification or termination of any order or from any order issued under section 104 of the Mine Act.

• Appeals of Judges' Decisions or Orders to the Commission - A filing with the Commission for discretionary review of a judge's decision or order by a person who has been adversely affected or aggrieved by such decision or order.

2

The following table reflects the types of legal actions pending before the Commission as of March 31, 2013:

MSHA Identification Number	Contests of Citations and Orders	Contests of Proposed Penalties	Complaints for Compensation	Complaints of Discharge, Discrimination or Interference	Applications for Temporary Relief	Appeals of Judges' Decisions or Orders to the Commission
04-00081	—	—	—	—	—	4
04-01698	—	3	—	—	—	—
04-05140	3	—	—	—	—	—
21-00462	1	—	—	—	—	—
24-02022	1	—	—	—	—	—
24-02414	1	—	—	—	—	—
35-03667	—	3	—	—	—	—
48-01383	—	4	—	—	—	—
51-00036	—	4	—	—	—	—
	6	14	—	—	—	4

3

XML

Earnings per common share (Details) In Thousands, unless otherwise specified	3 Months Ended
	Mar. 31, 2013	Mar. 31, 2012
Earnings per common share [Abstract]
Weighted average common shares outstanding - basic	188,831	188,811
Effect of dilutive stock options and performance share awards	391	371
Weighted average common shares outstanding - diluted	189,222	189,182
Shares excluded from the calculation of diluted earnings per share	0	0

XML

Business segment data (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended
	Mar. 31, 2013	Mar. 31, 2012
Segment Reporting Information [Line Items]
Total external operating revenues	$ 931,604	$ 852,807
Total intersegment operating revenues	0	0
Earnings (loss) on common stock	56,344	35,619
Regulated Operation [Member]
Segment Reporting Information [Line Items]
Total external operating revenues	424,124	395,081
Total intersegment operating revenues	18,718	20,409
Earnings (loss) on common stock	44,673	35,827
Unregulated Operation [Member]
Segment Reporting Information [Line Items]
Total external operating revenues	507,480	457,726
Total intersegment operating revenues	17,498	11,831
Earnings (loss) on common stock	11,671	(208)
Electric [Member] | Regulated Operation [Member]
Segment Reporting Information [Line Items]
Total external operating revenues	64,654	57,963
Total intersegment operating revenues	0	0
Earnings (loss) on common stock	9,825	7,559
Natural gas distribution [Member] | Regulated Operation [Member]
Segment Reporting Information [Line Items]
Total external operating revenues	331,754	307,891
Total intersegment operating revenues	0	0
Earnings (loss) on common stock	32,518	25,508
Pipeline and energy services [Member] | Regulated Operation [Member]
Segment Reporting Information [Line Items]
Total external operating revenues	27,716	29,227
Total intersegment operating revenues	18,718	20,409
Earnings (loss) on common stock	2,330	2,760
Exploration and production [Member] | Unregulated Operation [Member]
Segment Reporting Information [Line Items]
Total external operating revenues	115,363	88,494
Total intersegment operating revenues	9,812	11,328
Earnings (loss) on common stock	20,284	12,930
Construction materials and contracting [Member] | Unregulated Operation [Member]
Segment Reporting Information [Line Items]
Total external operating revenues	161,977	149,268
Total intersegment operating revenues	4,294	151
Earnings (loss) on common stock	(20,582)	(24,932)
Construction services [Member] | Unregulated Operation [Member]
Segment Reporting Information [Line Items]
Total external operating revenues	229,806	218,151
Total intersegment operating revenues	1,574	25
Earnings (loss) on common stock	11,664	11,403
Other [Member] | Unregulated Operation [Member]
Segment Reporting Information [Line Items]
Total external operating revenues	334	1,813
Total intersegment operating revenues	1,818	327
Earnings (loss) on common stock	305	391
Intersegment Elimination [Member]
Segment Reporting Information [Line Items]
Total external operating revenues	0	0
Total intersegment operating revenues	(36,216)	(32,240)
Earnings (loss) on common stock	$ 0	$ 0

XML

Derivative instruments (Details 3) (USD $) In Thousands, unless otherwise specified	Mar. 31, 2013	Dec. 31, 2012	Mar. 31, 2012
Derivatives, Fair Value [Line Items]
Derivative asset, fair value, gross asset	$ 6,179	$ 18,304	$ 27,280
Derivative liability fair value gross liability	12,445	6,255	29,651
Designated as hedging instrument [Member]
Derivatives, Fair Value [Line Items]
Derivative instruments in hedges, assets, at fair value	1,623	18,084	26,097
Derivative instruments in hedges, liabilities, at fair value	10,986	6,255	28,383
Not designated as hedging instrument [Member]
Derivatives, Fair Value [Line Items]
Other derivatives not designated as hedging instruments assets at fair value	4,556	220	1,183
Other derivatives not designated as hedging instruments liabilities at fair value	1,459	0	1,268
Interest rate swap [Member] | Designated as hedging instrument [Member] | Other accrued liabilities [Member]
Derivatives, Fair Value [Line Items]
Derivative instruments in hedges, liabilities, at fair value	4,458	6,255	1,168
Interest rate swap [Member] | Designated as hedging instrument [Member] | Other liabilities noncurrent [Member]
Derivatives, Fair Value [Line Items]
Derivative instruments in hedges, liabilities, at fair value	0	0	2,153
Commodity contract [Member] | Designated as hedging instrument [Member] | Commodity derivative instruments - current assets [Member]
Derivatives, Fair Value [Line Items]
Derivative instruments in hedges, assets, at fair value	1,623	18,084	25,560
Commodity contract [Member] | Designated as hedging instrument [Member] | Other assets noncurrent [Member]
Derivatives, Fair Value [Line Items]
Derivative instruments in hedges, assets, at fair value	0	0	537
Commodity contract [Member] | Designated as hedging instrument [Member] | Commodity derivative instruments - current liabilities [Member]
Derivatives, Fair Value [Line Items]
Derivative instruments in hedges, liabilities, at fair value	5,994	0	18,964
Commodity contract [Member] | Designated as hedging instrument [Member] | Other liabilities noncurrent [Member]
Derivatives, Fair Value [Line Items]
Derivative instruments in hedges, liabilities, at fair value	534	0	6,098
Commodity contract [Member] | Not designated as hedging instrument [Member] | Commodity derivative instruments - current assets [Member]
Derivatives, Fair Value [Line Items]
Other derivatives not designated as hedging instruments assets at fair value	4,313	220	1,138
Commodity contract [Member] | Not designated as hedging instrument [Member] | Other assets noncurrent [Member]
Derivatives, Fair Value [Line Items]
Other derivatives not designated as hedging instruments assets at fair value	243	0	45
Commodity contract [Member] | Not designated as hedging instrument [Member] | Commodity derivative instruments - current liabilities [Member]
Derivatives, Fair Value [Line Items]
Other derivatives not designated as hedging instruments liabilities at fair value	1,385	0	1,219
Commodity contract [Member] | Not designated as hedging instrument [Member] | Other liabilities noncurrent [Member]
Derivatives, Fair Value [Line Items]
Other derivatives not designated as hedging instruments liabilities at fair value	$ 74	$ 0	$ 49

XML

Employee benefit plans (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended
	Mar. 31, 2013	Mar. 31, 2012
Pension plans, defined benefit [Member]
Defined benefit plan disclosure, net periodic benefit cost [Line Items]
Defined benefit plan, service cost	$ 40	$ 345
Defined benefit plan, interest cost	4,018	4,554
Defined benefit plan, expected return on plan assets	(5,083)	(5,886)
Defined benefit plan, amortization of prior service cost (credit)	18	(21)
Defined benefit plan, amortization of net actuarial (gain) loss	1,864	1,681
Defined benefit plan, amortization of net transition obligation	0	0
Net periodic benefit cost, including amount capitalized	857	673
Net periodic benefit cost amount capitalized	110	234
Net periodic benefit cost	747	439
Other postretirement benefit plans, defined benefit [Member]
Defined benefit plan disclosure, net periodic benefit cost [Line Items]
Defined benefit plan, service cost	504	412
Defined benefit plan, interest cost	940	1,143
Defined benefit plan, expected return on plan assets	(1,107)	(1,244)
Defined benefit plan, amortization of prior service cost (credit)	(364)	(272)
Defined benefit plan, amortization of net actuarial (gain) loss	671	526
Defined benefit plan, amortization of net transition obligation	0	532
Net periodic benefit cost, including amount capitalized	644	1,097
Net periodic benefit cost amount capitalized	29	138
Net periodic benefit cost	615	959
Supplemental employee retirement plans, defined benefit [Member]
Defined benefit plan disclosure, net periodic benefit cost [Line Items]
Net periodic benefit cost	$ 1,900	$ 2,100

XML

Derivative instruments (Details) (USD $)	3 Months Ended
	Mar. 31, 2013	Mar. 31, 2012 MMBTU	Dec. 31, 2012
Derivative instruments [Line Items]
Natural gas swap agreement total forward notional volumes in MMBtu		214,000
Change in fair value of derivative instruments not designated as hedging instruments recorded as increase (decrease) to regulatory assets		$ 52,000
Notional amount of interest rate derivatives	40,000,000	60,000,000	50,000,000
Cash flow hedge gain (loss) to be reclassified within twelve months from AOCI into earnings	1,500,000
Derivatives with credit-risk-related contingent feature in net liability position, aggregate fair value	12,400,000
Assets needed for immediate settlement, of credit-risk-related contingent features, aggregate fair value	$ 12,400,000
Maximum length of time hedged in swap, collar and/or put cash flow hedge agreements (in months)	33 months
Oil swap and\or collar [Member]
Derivative instruments [Line Items]
Derivative, nonmonetary notional amount	2,800,000	4,000,000	2,600,000
Natural gas swap and\or collar [Member]
Derivative instruments [Line Items]
Derivative, nonmonetary notional amount	25,900,000	10,900,000	11,000,000
Natural gas basis swap [Member]
Derivative instruments [Line Items]
Derivative, nonmonetary notional amount	2,600,000

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Fair value measurements (Tables)

3 Months Ended

Mar. 31, 2013

Fair Value Disclosures [Abstract]

Available-for-sale securities

Details of available-for-sale securities were as follows:

March 31, 2013	Cost		Gross Unrealized Gains		Gross Unrealized Losses			Fair Value
	(In thousands)
Insurance contract	$	37,270	$	16,064	$	—		$	53,334
Mortgage-backed securities	8,749		133		(3		)	8,879
U.S. Treasury securities	1,301		39		—			1,340
Total	$	47,320	$	16,236	$	(3	)	$	63,553

March 31, 2012	Cost		Gross Unrealized Gains		Gross Unrealized Losses			Fair Value
	(In thousands)
Insurance contract	$	37,250	$	11,454	$	—		$	48,704
Auction rate securities	11,400		—		—			11,400
Mortgage-backed securities	7,952		119		(1		)	8,070
U.S. Treasury securities	1,968		49		(1		)	2,016
Total	$	58,570	$	11,622	$	(2	)	$	70,190

December 31, 2012	Cost		Gross Unrealized Gains		Gross Unrealized Losses			Fair Value
	(In thousands)
Insurance contract	$	37,250	$	11,648	$	—		$	48,898
Mortgage-backed securities	8,054		144		(3		)	8,195
U.S. Treasury securities	1,763		43		—			1,806
Total	$	47,067	$	11,835	$	(3	)	$	58,899

Assets and liabilities measured at fair value on a recurring basis

The Company's assets and liabilities measured at fair value on a recurring basis are as follows:

	Fair Value Measurements at March 31, 2013, Using
	Quoted Prices in Active Markets for Identical Assets (Level 1)		Significant Other Observable Inputs (Level 2)		Significant Unobservable Inputs (Level 3)		Balance at March 31, 2013
	(In thousands)
Assets:
Money market funds	$	—	$	31,281	$	—	$	31,281
Available-for-sale securities:
Insurance contract*	—		53,334		—		53,334
Mortgage-backed securities	—		8,879		—		8,879
U.S. Treasury securities	—		1,340		—		1,340
Commodity derivative instruments	—		6,179		—		6,179
Total assets measured at fair value	$	—	$	101,013	$	—	$	101,013
Liabilities:
Commodity derivative instruments	$	—	$	7,987	$	—	$	7,987
Interest rate derivative instruments	—		4,458		—		4,458
Total liabilities measured at fair value	$	—	$	12,445	$	—	$	12,445

*  The insurance contract invests approximately 29 percent in common stock of mid-cap companies, 28 percent in common stock of small-cap companies, 28 percent in common stock of large-cap companies and 15 percent in fixed-income and other investments.

	Fair Value Measurements at March 31, 2012, Using
	Quoted Prices in Active Markets for Identical Assets (Level 1)		Significant Other Observable Inputs (Level 2)		Significant Unobservable Inputs (Level 3)		Balance at March 31, 2012
	(In thousands)
Assets:
Money market funds	$	—	$	9,942	$	—	$	9,942
Available-for-sale securities:
Insurance contract*	—		48,704		—		48,704
Auction rate securities	—		11,400		—		11,400
Mortgage-backed securities	—		8,070		—		8,070
U.S. Treasury securities	—		2,016		—		2,016
Commodity derivative instruments	—		27,280		—		27,280
Total assets measured at fair value	$	—	$	107,412	$	—	$	107,412
Liabilities:
Commodity derivative instruments	$	—	$	26,330	$	—	$	26,330
Interest rate derivative instruments	—		3,321		—		3,321
Total liabilities measured at fair value	$	—	$	29,651	$	—	$	29,651

*  The insurance contract invests approximately 29 percent in common stock of mid-cap companies, 29 percent in common stock of small-cap companies, 29 percent in common stock of large-cap companies and 13 percent in fixed-income and other investments.

	Fair Value Measurements at December 31, 2012, Using
	Quoted Prices in Active Markets for Identical Assets (Level 1)		Significant Other Observable Inputs (Level 2)		Significant Unobservable Inputs  (Level 3)		Balance at December 31, 2012
	(In thousands)
Assets:
Money market funds	$	—	$	24,240	$	—	$	24,240
Available-for-sale securities:
Insurance contract*	—		48,898		—		48,898
Mortgage-backed securities	—		8,195		—		8,195
U.S. Treasury securities	—		1,806		—		1,806
Commodity derivative instruments	—		18,304		—		18,304
Total assets measured at fair value	$	—	$	101,443	$	—	$	101,443
Liabilities:
Interest rate derivative instruments	$	—	$	6,255	$	—	$	6,255
Total liabilities measured at fair value	$	—	$	6,255	$	—	$	6,255

* The insurance contract invests approximately 28 percent in common stock of mid-cap companies, 28 percent in common stock of small-cap companies, 29 percent in common stock of large-cap companies and 15 percent in fixed-income and other investments.

Fair value of long term debt outstanding

The estimated fair value of the Company's Level 2 long-term debt was as follows:

	Carrying Amount		Fair Value
	(In thousands)
Long-term debt at March 31, 2013	$	1,789,663	$	1,925,859
Long-term debt at March 31, 2012	$	1,416,189	$	1,578,395
Long-term debt at December 31, 2012	$	1,744,975	$	1,888,135

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Litigation (Details) (USD $)	Mar. 31, 2013	Mar. 31, 2012	Dec. 31, 2011	Aug. 31, 2011 Litigation related to construction materials [Member]	Mar. 31, 2013 Natural gas gathering operations [Member]	Jun. 30, 2012 Natural gas gathering operations [Member]	Oct. 31, 2010 Natural gas gathering operations [Member]	Sep. 30, 2010 Natural gas gathering operations [Member]	Jan. 13, 2012 Guarantee obligation under construction contract [Member]	Dec. 31, 2009 Guarantee obligation under construction contract [Member]
Loss Contingencies [Line Items]
Potential liabilities related to litigation and environmental matters	$ 33,300,000	$ 70,700,000	$ 22,500,000
Amount of compensatory damages in LPP's notice of demand										149,700,000
Arbitration award							26,600,000		22,000,000
Estimated damages in pending litigation, low estimate					16,100,000
Estimated damages in pending litigation, high estimate					22,600,000
Loss contingency, estimate of possible loss				3,700,000
Additional amount per day of potential penalties				5,000
Amount of expense (benefit) recorded in operation and maintenance expense related to natural gas gathering contract dispute, before tax						(24,100,000)		26,600,000
Amount of expense (benefit) recorded in operation and maintenance expense related to natural gas gathering contract dispute, after tax						(15,000,000)		16,500,000
Revised damage calculation	$ 1,000,000

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Contingencies

3 Months Ended

Mar. 31, 2013

Commitments and Contingencies Disclosure [Abstract]

Contingencies

Contingencies

The Company is party to claims and lawsuits arising out of its business and that of its consolidated subsidiaries. The Company accrues a liability for those contingencies when the incurrence of a loss is probable and the amount can be reasonably estimated. If a range of amounts can be reasonably estimated and no amount within the range is a better estimate than any other amount, then the minimum of the range is accrued. The Company does not accrue liabilities when the likelihood that the liability has been incurred is probable but the amount cannot be reasonably estimated or when the liability is believed to be only reasonably possible or remote. For contingencies where an unfavorable outcome is probable or reasonably possible and which are material, the Company discloses the nature of the contingency and, where feasible, an estimate of the possible loss. The Company had accrued liabilities of $33.3 million, $70.7 million and $22.5 million for contingencies, including litigation and environmental matters, as of March 31, 2013 and 2012, and December 31, 2012, respectively, which includes amounts that may have been accrued for matters discussed in Litigation and Environmental matters within this note.

Litigation

Guarantee Obligation Under a Construction Contract Centennial guaranteed CEM's obligations under a construction contract with LPP for a 550-MW combined-cycle electric generating facility near Hobbs, New Mexico. Centennial Resources sold CEM in July 2007 to Bicent. In February 2009, Centennial received a Notice and Demand from LPP under the guarantee agreement alleging that CEM did not meet certain of its obligations under the construction contract and demanding that Centennial indemnify LPP against all losses, damages, claims, costs, charges and expenses arising from CEM's alleged failures. In December 2009, LPP submitted a demand for arbitration of its dispute with CEM to the American Arbitration Association seeking compensatory damages of $149.7 million. An arbitration award was issued January 13, 2012, awarding LPP $22.0 million. Centennial subsequently received a demand from LPP for payment of the arbitration award plus interest and attorneys' fees. An accrual related to the guarantee as a result of the arbitration award was recorded in discontinued operations on the Consolidated Statement of Income in the fourth quarter of 2011. CEM filed a petition with the New York Supreme Court to vacate the arbitration award in favor of LPP. On October 19, 2012, Centennial moved to intervene in the New York Supreme Court action to vacate the arbitration award and also filed a complaint with the New York Supreme Court seeking a declaration that LPP is not entitled to indemnification from Centennial under the guaranty for the arbitration award. The New York Supreme Court granted CEM's petition to vacate the arbitration award on November 20, 2012, and entered a written order to that effect on April 11, 2013. Due to the vacation of the arbitration award, the Company no longer believes the loss related to this matter to be probable and thus the liability that was previously recorded in 2011 was reversed in the fourth quarter of 2012. Centennial anticipates LPP will appeal the order. We believe that it is reasonably possible that a loss related to this matter could result if LPP is successful in its appeal, the arbitration award is affirmed and LPP continues to assert its demand against Centennial under the guarantee for payment of the arbitration award, attorneys' fees and interest. For more information regarding discontinued operations, see Note 9.

Construction MaterialsUntil the fall of 2011 when it discontinued active mining operations at the pit, JTL operated the Target Range Gravel Pit in Missoula County, Montana under a 1975 reclamation contract pursuant to the Montana Opencut Mining Act. In September 2009, the Montana DEQ sent a letter asserting JTL was in violation of the Montana Opencut Mining Act by conducting mining operations outside a permitted area. JTL filed a complaint in Montana First Judicial District Court in June 2010, seeking a declaratory order that the reclamation contract is a valid permit under the Montana Opencut Mining Act. The Montana DEQ filed an answer and counterclaim to the complaint in August 2011, alleging JTL was in violation of the Montana Opencut Mining Act and requesting imposition of penalties of not more than $3.7 million plus not more than $5,000 per day from the date of the counterclaim. The Company believes the operation of the Target Range Gravel Pit was conducted under a valid permit; however, the imposition of civil penalties is reasonably possible. The Company filed an application for amendment of its opencut mining permit and intends to resolve this matter through settlement or continuation of the Montana First Judicial District Court litigation.

Natural Gas Gathering Operations In January 2010, SourceGas filed an application with the Colorado State District Court to compel WBI Energy Midstream to arbitrate a dispute regarding operating pressures under a natural gas gathering contract on one of WBI Energy Midstream's pipeline gathering systems in Montana. WBI Energy Midstream resisted the application and sought a declaratory order interpreting the gathering contract. In May 2010, the Colorado State District Court granted the application and ordered WBI Energy Midstream into arbitration. An arbitration hearing was held in August 2010. In October 2010, the arbitration panel issued an award in favor of SourceGas for approximately $26.6 million. As a result, WBI Energy Midstream, which is included in the pipeline and energy services segment, recorded a $26.6 million charge ($16.5 million after tax) in the third quarter of 2010. On April 20, 2011, the Colorado State District Court confirmed the arbitration award as a court judgment. WBI Energy Midstream filed an appeal from the Colorado State District Court's order and judgment to the Colorado Court of Appeals. The Colorado Court of Appeals issued a decision on May 24, 2012, reversing the Colorado State District Court order compelling arbitration, vacating the final award and remanding the case to the Colorado State District Court to determine SourceGas's claims and WBI Energy Midstream's counterclaims. As a result of the Colorado Court of Appeals decision, in the second quarter of 2012, WBI Energy Midstream changed its estimated loss related to this matter. This resulted in a reduction of expense of $24.1 million ($15.0 million after tax). On August 2, 2012, SourceGas filed a petition for writ of certiorari with the Colorado Supreme Court for review of the Colorado Court of Appeals decision. WBI Energy Midstream anticipates that if the Colorado Supreme Court were to grant a writ of certiorari and remand the matter to the Colorado State District Court, SourceGas will assert claims similar to those asserted in the arbitration proceeding.

In a related matter, Omimex filed a complaint against WBI Energy Midstream in Montana Seventeenth Judicial District Court in July 2010 alleging WBI Energy Midstream breached a separate gathering contract with Omimex as a result of the increased operating pressures demanded by SourceGas on the same natural gas gathering system. In December 2011, Omimex filed an amended complaint alleging WBI Energy Midstream breached obligations to operate its gathering system as a common carrier under United States and Montana law. WBI Energy Midstream removed the action to the United States District Court for the District of Montana. Expert reports submitted by Omimex contended its damages as a result of the increased operating pressures were $16.1 million to $22.6 million, however, the experts have since revised their calculation of Omimex's damages to $1.0 million. The Company believes the claims asserted by Omimex are without merit and an award is not deemed probable. The Company intends to vigorously defend against the claims. A trial on the matter is scheduled for July 2013.

The Company also is involved in other legal actions in the ordinary course of its business. After taking into account liabilities accrued for the foregoing matters, management believes that the outcomes with respect to the above and other legal proceedings will not have a material effect upon the Company's financial position, results of operations or cash flows.

Environmental matters

Portland Harbor Site In December 2000, Knife River - Northwest was named by the EPA as a PRP in connection with the cleanup of a riverbed site adjacent to a commercial property site acquired by Knife River - Northwest from Georgia-Pacific West, Inc. in 1999. The riverbed site is part of the Portland, Oregon, Harbor Superfund Site. The EPA wants responsible parties to share in the cleanup of sediment contamination in the Willamette River. To date, costs of the overall remedial investigation and feasibility study of the harbor site are being recorded, and initially paid, through an administrative consent order by the LWG, a group of several entities, which does not include Knife River - Northwest or Georgia-Pacific West, Inc. Investigative costs are indicated to be in excess of $70 million. It is not possible to estimate the cost of a corrective action plan until the remedial investigation and feasibility study have been completed, the EPA has decided on a strategy and a ROD has been published. Corrective action will be taken after the development of a proposed plan and ROD on the harbor site is issued. Knife River - Northwest also received notice in January 2008 that the Portland Harbor Natural Resource Trustee Council intends to perform an injury assessment to natural resources resulting from the release of hazardous substances at the Harbor Superfund Site. The Portland Harbor Natural Resource Trustee Council indicates the injury determination is appropriate to facilitate early settlement of damages and restoration for natural resource injuries. It is not possible to estimate the costs of natural resource damages until an assessment is completed and allocations are undertaken.

Based upon a review of the Portland Harbor sediment contamination evaluation by the Oregon DEQ and other information available, Knife River - Northwest does not believe it is a Responsible Party. In addition, Knife River - Northwest has notified Georgia-Pacific West, Inc., that it intends to seek indemnity for liabilities incurred in relation to the above matters pursuant to the terms of their sale agreement. Knife River - Northwest has entered into an agreement tolling the statute of limitations in connection with the LWG's potential claim for contribution to the costs of the remedial investigation and feasibility study. By letter in March 2009, LWG stated its intent to file suit against Knife River - Northwest and others to recover LWG's investigation costs to the extent Knife River - Northwest cannot demonstrate its non-liability for the contamination or is unwilling to participate in an alternative dispute resolution process that has been established to address the matter. At this time, Knife River - Northwest has agreed to participate in the alternative dispute resolution process.

The Company believes it is not probable that it will incur any material environmental remediation costs or damages in relation to the above referenced administrative action.

Manufactured Gas Plant Sites There are three claims against Cascade for cleanup of environmental contamination at manufactured gas plant sites operated by Cascade's predecessors.

The first claim is for contamination at a site in Eugene, Oregon which was received in 1995. There are PRPs in addition to Cascade that may be liable for cleanup of the contamination. Some of these PRPs have shared in the investigation costs. It is expected that these and other PRPs will share in the cleanup costs. Several alternatives for cleanup have been identified, with preliminary cost estimates ranging from approximately $500,000 to $11.0 million. The Oregon DEQ is preparing a staff report which will recommend a cleanup alternative for the site. It is not known at this time what share of the cleanup costs will actually be borne by Cascade; however, Cascade anticipates its proportional share could be approximately 50 percent. Cascade has accrued $1.3 million for remediation of this site. In January 2013, the OPUC approved Cascade's application to defer environmental remediation costs at the Eugene site for a period of 12 months starting November 30, 2012.

The second claim is for contamination at a site in Bremerton, Washington which was received in 1997. A preliminary investigation has found soil and groundwater at the site contain contaminants requiring further investigation and cleanup. EPA conducted a Targeted Brownfields Assessment of the site and released a report summarizing the results of that assessment in August 2009. The assessment confirms that contaminants have affected soil and groundwater at the site, as well as sediments in the adjacent Port Washington Narrows. Alternative remediation options have been identified with preliminary cost estimates ranging from $340,000 to $6.4 million. Data developed through the assessment and previous investigations indicates the contamination likely derived from multiple, different sources and multiple current and former owners of properties and businesses in the vicinity of the site may be responsible for the contamination. In April 2010, the Washington Department of Ecology issued notice it considered Cascade a PRP for hazardous substances at the site. In May 2012, the EPA added the site to the National Priorities List. Cascade has entered into an administrative settlement agreement and consent order with the EPA regarding the scope and schedule for a remedial investigation and feasibility study for the site. Cascade has accrued $6.7 million for the remedial investigation and feasibility study and $6.4 million for remediation of this site. In April 2010, Cascade filed a petition with the WUTC for authority to defer the costs, which are included in other noncurrent assets, incurred in relation to the environmental remediation of this site until the next general rate case. The WUTC approved the petition in September 2010, subject to conditions set forth in the order.

The third claim is for contamination at a site in Bellingham, Washington. Cascade received notice from a party in May 2008 that Cascade may be a PRP, along with other parties, for contamination from a manufactured gas plant owned by Cascade and its predecessor from about 1946 to 1962. The notice indicates that current estimates to complete investigation and cleanup of the site exceed $8.0 million. Other PRPs have reached an agreed order and work plan with the Washington Department of Ecology for completion of a remedial investigation and feasibility study for the site. A report documenting the initial phase of the remedial investigation was completed in June 2011. There is currently not enough information available to estimate the potential liability to Cascade associated with this claim although Cascade believes its proportional share of any liability will be relatively small in comparison to other PRPs. The plant manufactured gas from coal between approximately 1890 and 1946. In 1946, shortly after Cascade's predecessor acquired the plant, it converted the plant to a propane-air gas facility. There are no documented wastes or by-products resulting from the mixing or distribution of propane-air gas.

Cascade has received notices from certain of its insurance carriers that they will participate in defense of Cascade for these contamination claims subject to full and complete reservations of rights and defenses to insurance coverage. To the extent these claims are not covered by insurance, Cascade will seek recovery through the OPUC and WUTC of remediation costs in its natural gas rates charged to customers. The accruals related to these matters are reflected in regulatory assets.

Halawa Quarry The State of Hawaii Department of Health issued a Notice of Violation to Hawaiian Cement dated August 31, 2012, alleging violations of Hawaii's Water Pollution statute at Hawaiian Cement's Halawa Quarry by failure to comply with the quarry's National Pollutant Discharge Elimination System permit by failing to design, construct and maintain a facility to contain or treat the volume of all process wastewater and storm water that would result from a 10-year, 24-hour rainfall event. The Notice of Violation also alleged Hawaiian Cement violated the quarry's permit by discharging pollution, including levels of pH and total suspended solids in excess of the permit limits, on three occasions in January, June and December 2011. The Notice of Violation sought development and implementation of corrective action plans and unspecified administrative penalties. Hawaiian Cement resolved the Notice of Violation through a negotiated settlement which included payment of a monetary penalty of $100,000 as well as development and implementation of corrective action plans, the final cost of which are not expected to be material.

Guarantees

Centennial guaranteed CEM's obligations under a construction contract. For more information, see Litigation in this note.

In connection with the sale of the Brazilian Transmission Lines, as discussed in Note 10, Centennial has agreed to guarantee payment of any indemnity obligations of certain of the Company's indirect wholly owned subsidiaries who are the sellers in three purchase and sale agreements for periods ranging up to 10 years from the date of sale. The guarantees were required by the buyers as a condition to the sale of the Brazilian Transmission Lines.

WBI Holdings has guaranteed certain of Fidelity's oil and natural gas swap and collar agreement obligations. There is no fixed maximum amount guaranteed in relation to the oil and natural gas swap and collar agreements as the amount of the obligation is dependent upon oil and natural gas commodity prices. The amount of hedging activity entered into by the subsidiary is limited by corporate policy. The guarantees of the oil and natural gas swap and collar agreements at March 31, 2013, expire in the years ranging from 2013 to 2015; however, Fidelity continues to enter into additional hedging activities and, as a result, WBI Holdings from time to time may issue additional guarantees on these hedging obligations. The amount outstanding by Fidelity was $4.5 million and was reflected on the Consolidated Balance Sheet at March 31, 2013. In the event Fidelity defaults under its obligations, WBI Holdings would be required to make payments under its guarantees.

Certain subsidiaries of the Company have outstanding guarantees to third parties that guarantee the performance of other subsidiaries of the Company. These guarantees are related to construction contracts, natural gas transportation and sales agreements, gathering contracts and certain other guarantees. At March 31, 2013, the fixed maximum amounts guaranteed under these agreements aggregated $74.6 million. The amounts of scheduled expiration of the maximum amounts guaranteed under these agreements aggregate $17.4 million in 2013; $38.4 million in 2014; $300,000 in 2015; $100,000 in 2016; $600,000 in 2018; $300,000 in 2019; $13.5 million, which is subject to expiration on a specified number of days after the receipt of written notice; and $4.0 million, which has no scheduled maturity date. The amount outstanding by subsidiaries of the Company under the above guarantees was $200,000 and was reflected on the Consolidated Balance Sheet at March 31, 2013. In the event of default under these guarantee obligations, the subsidiary issuing the guarantee for that particular obligation would be required to make payments under its guarantee.

Certain subsidiaries have outstanding letters of credit to third parties related to insurance policies and other agreements, some of which are guaranteed by other subsidiaries of the Company. At March 31, 2013, the fixed maximum amounts guaranteed under these letters of credit, aggregated $32.3 million. In 2013 and 2014, $3.3 million and $29.0 million, respectively, of letters of credit are scheduled to expire. There were no amounts outstanding under the above letters of credit at March 31, 2013.

WBI Holdings has an outstanding guarantee to WBI Energy Transmission. This guarantee is related to a natural gas transportation and storage agreement that guarantees the performance of Prairielands. At March 31, 2013, the fixed maximum amount guaranteed under this agreement was $5.0 million and is scheduled to expire in 2014. In the event of Prairielands' default in its payment obligations, WBI Holdings would be required to make payment under its guarantee. The amount outstanding by Prairielands under the above guarantee was $900,000. The amount outstanding under this guarantee was not reflected on the Consolidated Balance Sheet at March 31, 2013, because this intercompany transaction was eliminated in consolidation.

In addition, Centennial, Knife River and MDU Construction Services have issued guarantees to third parties related to the routine purchase of maintenance items, materials and lease obligations for which no fixed maximum amounts have been specified. These guarantees have no scheduled maturity date. In the event a subsidiary of the Company defaults under these obligations, Centennial, Knife River and MDU Construction Services would be required to make payments under these guarantees. Any amounts outstanding by subsidiaries of the Company for these guarantees were reflected on the Consolidated Balance Sheet at March 31, 2013.

In the normal course of business, Centennial has surety bonds related to construction contracts and reclamation obligations of its subsidiaries, as well as an arbitration award. In the event a subsidiary of Centennial does not fulfill a bonded obligation, Centennial would be responsible to the surety bond company for completion of the bonded contract or obligation. A large portion of the surety bonds is expected to expire within the next 12 months; however, Centennial will likely continue to enter into surety bonds for its subsidiaries in the future. As of March 31, 2013, approximately $639 million of surety bonds were outstanding, which were not reflected on the Consolidated Balance Sheet.

Variable interest entities

The Company evaluates its arrangements and contracts with other entities to determine if they are VIEs and if so, if the Company is the primary beneficiary. GAAP provides a framework for identifying VIEs and determining when a company should include the assets, liabilities, noncontrolling interest, and results of activities of a VIE in its consolidated financial statements.

A VIE should be consolidated if a party with an ownership, contractual, or other financial interest in the VIE (a variable interest holder) has the power to direct the VIE's most significant activities and the obligation to absorb losses or right to receive benefits of the VIE that could be significant to the VIE. A variable interest holder that consolidates the VIE is called the primary beneficiary. Upon consolidation, the primary beneficiary generally must initially record all of the VIE's assets, liabilities, and noncontrolling interests at fair value and subsequently account for the VIE as if it were consolidated.

The Company's evaluation of whether it qualifies as the primary beneficiary of a VIE is highly complex and involves significant judgments, estimates and assumptions and includes a qualitative analysis of the activities that most significantly impact the VIE's economic performance and whether the Company has the power to direct those activities, the design of the entity, the rights of the parties, and the purpose of the arrangement.

Dakota Prairie Refining, LLCOn February 7, 2013, WBI Energy and Calumet formed a limited liability company, Dakota Prairie Refining, and entered into an operating agreement to develop, build and operate a diesel topping plant in southwestern North Dakota. WBI Energy and Calumet each have a fifty percent ownership interest in Dakota Prairie Refining. WBI Energy's and Calumet's capital commitments under the agreement are $150 million and $75 million, respectively. Dakota Prairie Refining entered into a term loan for project debt financing of $75 million on April 22, 2013. The agreement provides for allocation of profits and losses consistent with ownership interests; however, deductions attributable to project financing debt will be allocated to Calumet. Calumet's future cash distributions from Dakota Prairie Refining will be decreased by the principal and interest to be paid on the project debt, while the cash distributions to WBI Energy will not be decreased. Pursuant to the agreement, Centennial agreed to guarantee Dakota Prairie Refining's obligation under the term loan. For more information on the guarantee, see Note 19.

Dakota Prairie Refining has been determined to be a VIE, and the Company has determined that it is the primary beneficiary as it has an obligation to absorb losses that could be potentially significant to the VIE through WBI Energy's equity investment and Centennial's guarantee of the third-party term loan. Accordingly, the Company consolidates Dakota Prairie Refining in its financial statements and records a noncontrolling interest for Calumet's ownership interest.

Construction on the diesel topping plant began in early 2013 and the plant is not yet operational. The assets of Dakota Prairie Refining shall be used solely for the benefit of Dakota Prairie Refining. The total assets and liabilities of Dakota Prairie Refining reflected on the Company's Consolidated Balance Sheets were as follows:

	March 31, 2013
	(In thousands)
ASSETS
Current assets:
Cash and cash equivalents	$	10,793
Total current assets	10,793
Net property, plant and equipment	27,356
Total assets	$	38,149
LIABILITIES
Current liabilities:
Accounts payable	$	10,948
Total liabilities	$	10,948

Fuel Contract On October 10, 2012, the Coyote Station entered into a new coal supply agreement with Coyote Creek that will replace a coal supply agreement that expires in May 2016. The new agreement provides for the purchase of coal necessary to supply the coal requirements of the Coyote Station, of which the Company is a 25.0 percent owner, for the period May 2016 through December 2040.

The new coal supply agreement creates a variable interest in Coyote Creek due to the transfer of all operating and economic risk to the Coyote Station owners as the agreement is structured so the price of the coal will cover all costs of operations as well as future reclamation costs. The Coyote Station owners are also providing a guarantee of the value of the assets of Coyote Creek as they would be required to buy the assets at book value should they terminate the contract prior to the end of the contract term and are providing a guarantee of the value of the equity of Coyote Creek in that they are required to buy the entity at the end of the contract term at equity value. Although the Company has determined that Coyote Creek is a VIE, the Company has concluded that it is not the primary beneficiary of Coyote Creek because the authority to direct the activities of the entity is shared by the four unrelated owners of the Coyote Station with no primary beneficiary existing. As a result, Coyote Creek is not required to be consolidated in the Company's financial statements.

At March 31, 2013, Coyote Creek was not yet operational. The assets and liabilities of Coyote Creek and exposure to loss as a result of the Company's involvement with the VIE at March 31, 2013, is not material.

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Available-for-sale securities (Details) (USD $)	3 Months Ended
	Mar. 31, 2013	Mar. 31, 2012	Dec. 31, 2012
Schedule of available-for-sale securities [Line Items]
Investments used to satisfy obligations under nonqualified benefit plans	$ 53,300,000	$ 48,700,000	$ 48,900,000
Net unrealized gain (loss) of investments used to satify obligations under nonqualified benefit plans	4,400,000	5,000,000
Available-for-sale securities [Abstract]
Available-for-sale securities, amortized cost basis	47,320,000	58,570,000	47,067,000
Available-for-sale securities, gross unrealized gains	16,236,000	11,622,000	11,835,000
Available-for-sale securities, gross unrealized losses	(3,000)	(2,000)	(3,000)
Available-for-sale securities	63,553,000	70,190,000	58,899,000
Insurance contract [Member]
Available-for-sale securities [Abstract]
Available-for-sale securities, amortized cost basis	37,270,000	37,250,000	37,250,000
Available-for-sale securities, gross unrealized gains	16,064,000	11,454,000	11,648,000
Available-for-sale securities, gross unrealized losses	0	0	0
Available-for-sale securities	53,334,000	48,704,000	48,898,000
Auction rate securities [Member]
Available-for-sale securities [Abstract]
Available-for-sale securities, amortized cost basis		11,400,000
Available-for-sale securities, gross unrealized gains		0
Available-for-sale securities, gross unrealized losses		0
Available-for-sale securities		11,400,000
Collateralized mortgage backed securities [Member]
Available-for-sale securities [Abstract]
Available-for-sale securities, amortized cost basis	8,749,000	7,952,000	8,054,000
Available-for-sale securities, gross unrealized gains	133,000	119,000	144,000
Available-for-sale securities, gross unrealized losses	(3,000)	(1,000)	(3,000)
Available-for-sale securities	8,879,000	8,070,000	8,195,000
US Treasury securities [Member]
Available-for-sale securities [Abstract]
Available-for-sale securities, amortized cost basis	1,301,000	1,968,000	1,763,000
Available-for-sale securities, gross unrealized gains	39,000	49,000	43,000
Available-for-sale securities, gross unrealized losses	0	(1,000)	0
Available-for-sale securities	$ 1,340,000	$ 2,016,000	$ 1,806,000

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Comprehensive income (loss) reclassifications (Details 2) (USD $) In Thousands, unless otherwise specified	3 Months Ended
	Mar. 31, 2013	Mar. 31, 2012
Other comprehensive income (loss), reclassification adjustment on derivatives included in net income, before tax	$ 4,398
Less: Reclassification adjustment for gain on derivative instruments included in net income, tax	(1,626)	(1,366)
Amounts reclassified from accumulated other comprehensive gain (loss)	2,772	2,329
Other comprehensive income (loss) amortization of postretirement losses included in net periodic benefit cost, before tax	(967)
Amortization of postretirement liability losses included in net periodic benefit cost, tax	319	0
Other comprehensive income reclassification of defined benefit plans amortization of gain (loss) recognized in net periodic benefit cost, net of tax	(648)	0
Other comprehensive income (loss), reclassification adjustment for sale of securities included in net income, before tax	(54)
Less: Reclassification adjustment for loss on available-for-sale investments included in net income, tax	19	16
Other comprehensive income (loss), reclassification adjustment for sale of securities included in net income, net of tax	(35)	(30)
Other comprehensive income loss reclassification adjustments net of tax	2,089
Commodity derivative instruments
Other comprehensive income (loss), reclassification adjustment on derivatives included in net income, before tax	4,513
Interest rate derivative instruments
Other comprehensive income (loss), reclassification adjustment on derivatives included in net income, before tax	$ (115)

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Accounts receivable and allowance for doubtful accounts (Details) (USD $) In Millions, unless otherwise specified	Mar. 31, 2013	Dec. 31, 2012	Mar. 31, 2012
Accounts receivable and allowance for doubtful accounts [Abstract]
Receivables past due 90 days or more	$ 39.6	$ 34.3	$ 34.6
Allowance for doubtful accounts receivable	$ 10.8	$ 10.8	$ 12.2

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Fair value measurements (Details 3) (USD $) In Thousands, unless otherwise specified	Mar. 31, 2013	Dec. 31, 2012	Mar. 31, 2012
Carrying (reported) amount, fair value disclosure [Member]
Fair value, balance sheet grouping, financial statement captions [Line Items]
Long-term debt	$ 1,789,663	$ 1,744,975	$ 1,416,189
Estimate of fair value, fair value disclosure [Member]
Fair value, balance sheet grouping, financial statement captions [Line Items]
Long-term debt	$ 1,925,859	$ 1,888,135	$ 1,578,395

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Gains and losses on derivatives instruments (Details 2) (USD $) In Thousands, unless otherwise specified	3 Months Ended
	Mar. 31, 2013	Mar. 31, 2012
Derivative instruments [Line Items]
Amount of gain (loss) recognized in accumulated other comprehensive loss (effective portion), net of tax	$ (5,849)	$ (3,770)
Amounts reclassified from accumulated other comprehensive gain (loss)	2,772	2,329
Commodity derivatives designated as cash flow hedges [Member]
Derivative instruments [Line Items]
Amount of gain (loss) recognized in accumulated other comprehensive loss (effective portion), net of tax	(6,154)	(4,659)
Amounts reclassified from accumulated other comprehensive gain (loss)	2,843	2,343
Amount of gain (loss) recognized in income statement (ineffective portion), before tax	(1,422)	(4,251)
Interest rate derivatives designated as cash flow hedges [Member]
Derivative instruments [Line Items]
Amount of gain (loss) recognized in accumulated other comprehensive loss (effective portion), net of tax	305	889
Amounts reclassified from accumulated other comprehensive gain (loss)	(71)	(14)
Amount of gain (loss) recognized in income statement (ineffective portion), before tax	(159)	0
Commodity derivatives not designated as hedging instruments:
Derivative instruments [Line Items]
Amount of gain (loss) recognized in operating revenues, before tax	$ (4,410)	$ 55

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Seasonality of operations

3 Months Ended

Mar. 31, 2013

Seasonality of operations [Abstract]

Seasonality of operations

Seasonality of operations

Some of the Company's operations are highly seasonal and revenues from, and certain expenses for, such operations may fluctuate significantly among quarterly periods. Accordingly, the interim results for particular businesses, and for the Company as a whole, may not be indicative of results for the full fiscal year.

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Equity method investments (Details) (USD $) In Millions, unless otherwise specified	Mar. 31, 2013	Dec. 31, 2012	Mar. 31, 2012	Aug. 31, 2012 ECTE [Member]	Nov. 30, 2011 ECTE [Member]	Nov. 30, 2010 ECTE [Member]	Nov. 30, 2010 ENTE [Member]	Nov. 30, 2010 ERTE [Member]
Schedule of Equity Method Investments [Line Items]
Percentage ownership interest in equity method investment sold						59.96%	100.00%	100.00%
Number of years over which remaining ownership interest in equity method investment will be sold						4 years
Portion of remaining interest sold				25.00%	25.00%
Total assets of equity method investments	$ 142.9	$ 129.0	$ 105.3
Total long-term debt of equity method investments	63.9	65.5	35.9
Investment in equity method investments	5.7	6.9	8.2
Undistributed earnings of equity method investments	$ 2.2	$ 3.4	$ 2.2

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Cash flow information (Tables)

3 Months Ended

Mar. 31, 2013

Cash flow information [Abstract]

Supplemental cash flow information

Cash expenditures for interest and income taxes were as follows:

	Three Months Ended
	March 31,
	2013			2012
	(In thousands)
Interest, net of amount capitalized	$	21,857		$	22,433
Income taxes paid (refunded), net	$	(7,246	)	$	285

Noncash investing transactions were as follows:

	March 31,
	2013		2012
	(In thousands)
Property, plant and equipment additions in accounts payable	$	92,236	$	51,739

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Earnings per common share (Tables)

3 Months Ended

Mar. 31, 2013

Earnings Per Share [Abstract]

Schedule of weighted average number of shares [Table Text Block]

A reconciliation of the weighted average common shares outstanding used in the basic and diluted earnings per share calculation was as follows:

	Three Months Ended
	March 31,
	2013	2012
	(In thousands)
Weighted average common shares outstanding - basic	188,831	188,811
Effect of dilutive stock options and performance share awards	391	371
Weighted average common shares outstanding - diluted	189,222	189,182
Shares excluded from the calculation of diluted earnings per share	—	—

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Regulatory matters and revenues subject to refund (Details) (USD $)	Apr. 12, 2013 MTPSC [Member]	Sep. 26, 2012 MTPSC [Member]	Dec. 21, 2012 SDPUC [Member]
Regulatory matters and revenues subject to refund [Line Items]
Total gas rate increase requested		$ 3,500,000	$ 1,500,000
Percent above current rates requested		5.90%	3.30%
Amount of requested interim increase in annual gas rates		1,700,000
Requested percentage of interim gas rate increase		2.90%
Authorized interim increase	$ 850,000

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Goodwill rollforward (Details) (USD $)	3 Months Ended				12 Months Ended
	Mar. 31, 2013		Mar. 31, 2012		Dec. 31, 2012
Goodwill [Roll Forward]
Balance as of beginning of period	$ 636,039,000	[1]	$ 634,931,000	[1]	$ 634,931,000	[1]
Goodwill acquired during the year	0		458,000	[2]	1,108,000	[2]
Balance as of end of period	636,039,000	[1]	635,389,000	[1]	636,039,000	[1]
Natural gas distribution [Member]
Goodwill [Roll Forward]
Balance as of beginning of period	345,736,000		345,736,000		345,736,000
Goodwill acquired during the year	0		0	[2]	0	[2]
Balance as of end of period	345,736,000		345,736,000		345,736,000
Pipeline and energy services [Member]
Goodwill [Line Items]
Goodwill, impaired, accumulated impairment loss	12,300,000		12,300,000		12,300,000
Goodwill [Roll Forward]
Balance as of beginning of period	9,737,000	[1]	9,737,000	[1]	9,737,000	[1]
Goodwill acquired during the year	0		0	[2]	0	[2]
Balance as of end of period	9,737,000	[1]	9,737,000	[1]	9,737,000	[1]
Construction materials and contracting [Member]
Goodwill [Roll Forward]
Balance as of beginning of period	176,290,000		176,290,000		176,290,000
Goodwill acquired during the year	0		0	[2]	0	[2]
Balance as of end of period	176,290,000		176,290,000		176,290,000
Construction services [Member]
Goodwill [Roll Forward]
Balance as of beginning of period	104,276,000		103,168,000		103,168,000
Goodwill acquired during the year	0		458,000	[2]	1,108,000	[2]
Balance as of end of period	$ 104,276,000		$ 103,626,000		$ 104,276,000

[1] Balance is presented net of accumulated impairment of $12.3 million at the pipeline and energy services segment, which occurred in prior periods.

[2] Includes contingent consideration that was not material related to an acquisition in a prior period.

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Comprehensive income (loss) (Tables)

3 Months Ended

Mar. 31, 2013

Comprehensive income (loss) [Abstract]

Comprehensive income (loss)

The after-tax changes in the components of accumulated other comprehensive loss as of March 31, 2013, were as follows:

	Net Unrealized Gain (Loss) on Derivative  Instruments  Qualifying as Hedges			Net Unrealized Gain (Loss) on Available-for-sale Investments			Postretirement  Liability Adjustment			Foreign Currency Translation Adjustment			Total Accumulated  Other Comprehensive  Loss
	(In thousands)
Balance at December 31, 2012	$	6,018		$	119		$	(54,347	)	$	(511	)	$	(48,721	)
Other comprehensive income (loss) before reclassifications	(5,849		)	(44		)	—			88			(5,805		)
Amounts reclassified from accumulated other comprehensive loss	(2,772		)	35			648			—			(2,089		)
Net current-period other comprehensive loss	(8,621		)	(9		)	648			88			(7,894		)
Balance at March 31, 2013	$	(2,603	)	$	110		$	(53,699	)	$	(423	)	$	(56,615	)

Reclassification out of accumulated other comprehensive income

Reclassifications out of accumulated other comprehensive loss were as follows:

	Three Months Ended			Location on Consolidated Statements of Income
	March 31,
	2013
	(In thousands)
Reclassification adjustment for gain (loss) on derivative instruments included in net income
Commodity derivative instruments	$	4,513		Operating revenues
Interest rate derivative instruments	(115		)	Interest expense
	4,398
	(1,626		)	Income taxes
	2,772
Amortization of postretirement liability losses included in net periodic benefit cost	(967		)	(a)
	319			Income taxes
	(648		)
Reclassification adjustment for loss on available-for-sale investments included in net income	(54		)	Other income
	19			Income taxes
	(35		)
Total reclassifications	$	2,089

(a) Included in net periodic pension cost (see Note 16 for additional details).

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Goodwill and other intangible assets (Tables)

3 Months Ended

Mar. 31, 2013

Goodwill and Intangible Assets Disclosure [Abstract]

Changes in the carrying amount of goodwill

The changes in the carrying amount of goodwill were as follows:

Three Months Ended March 31, 2013	Balance as of January 1, 2013*		Goodwill Acquired During the Year		Balance as of March 31, 2013*
	(In thousands)
Natural gas distribution	$	345,736	$	—	$	345,736
Pipeline and energy services	9,737		—		9,737
Construction materials and contracting	176,290		—		176,290
Construction services	104,276		—		104,276
Total	$	636,039	$	—	$	636,039

* Balance is presented net of accumulated impairment of $12.3 million at the pipeline and energy services segment, which occurred in prior periods.

Three Months Ended March 31, 2012	Balance as of January 1, 2012*		Goodwill Acquired During the Year**		Balance as of March 31, 2012*
	(In thousands)
Natural gas distribution	$	345,736	$	—	$	345,736
Pipeline and energy services	9,737		—		9,737
Construction materials and contracting	176,290		—		176,290
Construction services	103,168		458		103,626
Total	$	634,931	$	458	$	635,389

* Balance is presented net of accumulated impairment of $12.3 million at the pipeline and energy services segment, which occurred in prior periods.

** Includes contingent consideration that was not material related to an acquisition in a prior period.

Year Ended December 31, 2012	Balance as of January 1, 2012*		Goodwill Acquired During the Year**		Balance as of December 31, 2012*
	(In thousands)
Natural gas distribution	$	345,736	$	—	$	345,736
Pipeline and energy services	9,737		—		9,737
Construction materials and contracting	176,290		—		176,290
Construction services	103,168		1,108		104,276
Total	$	634,931	$	1,108	$	636,039

  * Balance is presented net of accumulated impairment of $12.3 million at the pipeline and energy services segment, which occurred in prior periods.

** Includes contingent consideration that was not material related to an acquisition in a prior period.

Other amortizable intangible assets

Other amortizable intangible assets were as follows:

	March 31, 2013			March 31, 2012			December 31, 2012
	(In thousands)
Customer relationships	$	21,310		$	21,010		$	21,310
Accumulated amortization	(12,211		)	(10,197		)	(11,701		)
	9,099			10,813			9,609
Noncompete agreements	7,236			7,086			7,236
Accumulated amortization	(5,439		)	(4,921		)	(5,326		)
	1,797			2,165			1,910
Other	10,979			11,442			10,979
Accumulated amortization	(5,557		)	(4,429		)	(5,369		)
	5,422			7,013			5,610
Total	$	16,318		$	19,991		$	17,129

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Basis of presentation

3 Months Ended

Mar. 31, 2013

Organization, Consolidation and Presentation of Financial Statements [Abstract]

Basis of presentation

Basis of presentation

The accompanying consolidated interim financial statements were prepared in conformity with the basis of presentation reflected in the consolidated financial statements included in the Company's 2012 Annual Report, and the standards of accounting measurement set forth in the interim reporting guidance in the ASC and any amendments thereto adopted by the FASB. Interim financial statements do not include all disclosures provided in annual financial statements and, accordingly, these financial statements should be read in conjunction with those appearing in the 2012 Annual Report. The information is unaudited but includes all adjustments that are, in the opinion of management, necessary for a fair presentation of the accompanying consolidated interim financial statements and are of a normal recurring nature. Depreciation, depletion and amortization expense is reported separately on the Consolidated Statements of Income and therefore is excluded from the other line items within operating expenses. Management has also evaluated the impact of events occurring after March 31, 2013, up to the date of issuance of these consolidated interim financial statements.

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Derivative instruments (Tables)

3 Months Ended

Mar. 31, 2013

Derivative Instruments and Hedging Activities Disclosure [Abstract]

Schedule of derivative instruments, gain (losses)

The gains and losses on derivative instruments were as follows:

	Three Months Ended
	March 31,
	2013			2012
	(In thousands)
Commodity derivatives designated as cash flow hedges:
Amount of loss recognized in accumulated other comprehensive loss (effective portion), net of tax	$	(6,154	)	$	(4,659	)
Amount of gain reclassified from accumulated other comprehensive loss into operating revenues (effective portion), net of tax	2,843			2,343
Amount of loss recognized in operating revenues (ineffective portion), before tax	(1,422		)	(4,251		)
Interest rate derivatives designated as cash flow hedges:
Amount of gain recognized in accumulated other comprehensive loss (effective portion), net of tax	305			889
Amount of loss reclassified from accumulated other comprehensive loss into interest expense (effective portion), net of tax	(71		)	(14		)
Amount of loss recognized in interest expense (ineffective portion), before tax	(159		)	—
Commodity derivatives not designated as hedging instruments:
Amount of gain (loss) recognized in operating revenues, before tax	(4,410		)	55

Derivative instruments (Tables)

The location and fair value of the gross amount of the Company's derivative instruments on the Consolidated Balance Sheets were as follows:

Asset Derivatives	Location on Consolidated Balance Sheets	Fair Value at March 31, 2013		Fair Value at March 31, 2012		Fair Value at December 31, 2012
		(In thousands)
Designated as hedges:
Commodity derivatives	Commodity derivative instruments	$	1,623	$	25,560	$	18,084
	Other assets - noncurrent	—		537		—
		1,623		26,097		18,084
Not designated as hedges:
Commodity derivatives	Commodity derivative instruments	4,313		1,138		220
	Other assets - noncurrent	243		45		—
		4,556		1,183		220
Total asset derivatives		$	6,179	$	27,280	$	18,304

Liability Derivatives	Location on Consolidated Balance Sheets	Fair Value at March 31, 2013		Fair Value at March 31, 2012		Fair Value at December 31, 2012
		(In thousands)
Designated as hedges:
Commodity derivatives	Commodity derivative instruments	$	5,994	$	18,964	$	—
	Other liabilities - noncurrent	534		6,098		—
Interest rate derivatives	Other accrued liabilities	4,458		1,168		6,255
	Other liabilities - noncurrent	—		2,153		—
		10,986		28,383		6,255
Not designated as hedges:
Commodity derivatives	Commodity derivative instruments	1,385		1,219		—
	Other liabilities - noncurrent	74		49		—
		1,459		1,268		—
Total liability derivatives		$	12,445	$	29,651	$	6,255

All of the Company's commodity and interest rate derivative instruments at March 31, 2013 and 2012, and December 31, 2012, were subject to legally enforceable master netting agreements. However, the Company's policy is to not offset fair value amounts for derivative instruments and, as a result, the Company's derivative assets and liabilities are presented gross on the Consolidated Balance Sheets. The gross derivative assets and liabilities (excluding settlement receivables and payables that may be subject to the same master netting agreements) presented on the Consolidated Balance Sheets and the amount eligible for offset under the master netting agreements is presented in the following table:

March 31, 2013	Gross Amounts Recognized on the Consolidated Balance Sheets		Gross Amounts Not Offset on the Consolidated Balance Sheets			Net
	(In thousands)
Assets:
Commodity derivatives	$	6,179	$	(3,578	)	$	2,601
Total assets	$	6,179	$	(3,578	)	$	2,601
Liabilities:
Commodity derivatives	$	7,987	$	(3,578	)	$	4,409
Interest rate derivatives	4,458		—			4,458
Total liabilities	$	12,445	$	(3,578	)	$	8,867

March 31, 2012	Gross Amounts Recognized on the Consolidated Balance Sheets		Gross Amounts Not Offset on the Consolidated Balance Sheets			Net
	(In thousands)
Assets:
Commodity derivatives	$	27,280	$	(15,805	)	$	11,475
Total assets	$	27,280	$	(15,805	)	$	11,475
Liabilities:
Commodity derivatives	$	26,330	$	(15,805	)	$	10,525
Interest rate derivatives	3,321		—			3,321
Total liabilities	$	29,651	$	(15,805	)	$	13,846

December 31, 2012	Gross Amounts Recognized on the Consolidated Balance Sheets		Gross Amounts Not Offset on the Consolidated Balance Sheets		Net
	(In thousands)
Assets:
Commodity derivatives	$	18,304	$	—	$	18,304
Total assets	$	18,304	$	—	$	18,304
Liabilities:
Interest rate derivatives	$	6,255	$	—	$	6,255
Total liabilities	$	6,255	$	—	$	6,255

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Cash flow information (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended
	Mar. 31, 2013	Mar. 31, 2012
Cash flow information [Abstract]
Interest, net of amount capitalized	$ 21,857	$ 22,433
Income taxes paid (refunded), net	(7,246)	285
Property, plant and equipment additions in accounts payable	$ 92,236	$ 51,739

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Income taxes (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended
	Mar. 31, 2013	Mar. 31, 2012
Income Tax Disclosure [Abstract]
Income tax expense for unrecognized tax positions		$ 2.2
Reduction in deferred income tax expense due to deferred income tax rate reduction		2.5
Unrecognized tax benefits to be settled within 12 months	$ 14.9
Anticipated settlement of federal and state audits	12 months

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Consolidated Statements of Income (USD $) In Thousands, except Per Share data, unless otherwise specified	3 Months Ended
	Mar. 31, 2013	Mar. 31, 2012
Operating revenues:
Electric, natural gas distribution and pipeline and energy services	$ 424,124	$ 395,081
Exploration and production, construction materials and contracting, construction services and other	507,480	457,726
Total operating revenues	931,604	852,807
Operating expenses:
Fuel and purchased power	21,608	18,420
Purchased natural gas sold	199,187	185,428
Operation and maintenance:
Electric, natural gas distribution and pipeline and energy services	66,101	68,401
Exploration and production, construction materials and contracting, construction services and other	394,019	376,146
Depreciation, depletion and amortization	93,561	85,380
Taxes, other than income	52,597	47,975
Total operating expenses	827,073	781,750
Operating income	104,531	71,057
Earnings (loss) from equity method investments	(311)	1,253
Other income	1,242	1,098
Interest expense	20,874	19,439
Income before income taxes	84,588	53,969
Income taxes	27,996	18,079
Income from continuing operations	56,592	35,890
Loss from discontinued operations, net of tax	(77)	(100)
Net income	56,515	35,790
Dividends declared on preferred stocks	171	171
Earnings on common stock	$ 56,344	$ 35,619
Earnings per common share - basic:
Earnings before discontinued operations	$ 0.30	$ 0.19
Discontinued operations, net of tax	$ 0.00	$ 0.00
Earnings per common share - basic	$ 0.30	$ 0.19
Earnings per common share - diluted:
Earnings before discontinued operations	$ 0.30	$ 0.19
Discontinued operations, net of tax	$ 0.00	$ 0.00
Earnings per common share - diluted	$ 0.30	$ 0.19
Dividends declared per common share	$ 0.1725	$ 0.1675
Weighted average common shares outstanding - basic	188,831	188,811
Weighted average common shares outstanding - diluted	189,222	189,182

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Other intangible assets (Details 2) (USD $)	3 Months Ended
	Mar. 31, 2013	Mar. 31, 2012	Dec. 31, 2012
Finite-Lived Intangible Assets [Line Items]
Intangible assets, net (excluding goodwill)	$ 16,318,000	$ 19,991,000	$ 17,129,000
Amortization of intangible assets	800,000	900,000
Estimated amortization expense for amortizable intangible assets [Abstract]
2013	3,700,000
2014	3,500,000
2015	2,600,000
2016	2,200,000
2017	1,900,000
Thereafter	3,200,000
Customer relationships [Member]
Finite-Lived Intangible Assets [Line Items]
Finite-lived intangible assets, gross	21,310,000	21,010,000	21,310,000
Finite-lived intangible assets, accumulated amortization	(12,211,000)	(10,197,000)	(11,701,000)
Intangible assets, net (excluding goodwill)	9,099,000	10,813,000	9,609,000
Noncompete agreements [Member]
Finite-Lived Intangible Assets [Line Items]
Finite-lived intangible assets, gross	7,236,000	7,086,000	7,236,000
Finite-lived intangible assets, accumulated amortization	(5,439,000)	(4,921,000)	(5,326,000)
Intangible assets, net (excluding goodwill)	1,797,000	2,165,000	1,910,000
Other intangible assets [Member]
Finite-Lived Intangible Assets [Line Items]
Finite-lived intangible assets, gross	10,979,000	11,442,000	10,979,000
Finite-lived intangible assets, accumulated amortization	(5,557,000)	(4,429,000)	(5,369,000)
Intangible assets, net (excluding goodwill)	$ 5,422,000	$ 7,013,000	$ 5,610,000

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Consolidated Balance Sheets (Parenthetical) (USD $)	Mar. 31, 2013	Dec. 31, 2012	Mar. 31, 2012
Stockholders' equity:
Common stock, shares authorized	500,000,000	500,000,000	500,000,000
Common stock, par value	$ 1.00	$ 1.00	$ 1.00
Common stock, shares issued	189,369,450	189,369,450	189,369,450
Treasury shares	538,921	538,921	538,921

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Gurantees (Details 3) (USD $)	Mar. 31, 2013
Guarantor Obligations [Line Items]
Amount of hedging obligations guaranteed reflected on balance sheet	$ 4,500,000
Guarantor obligations, maximum exposure, undiscounted	74,600,000
Fixed maximum amounts guaranteed by year 2013	17,400,000
Fixed maximum amounts guaranteed by year 2014	38,400,000
Fixed maximum amounts guaranteed by year 2015	300,000
Fixed maximum amounts guaranteed by year 2016	100,000
Fixed maximum amounts guaranteed by year 2018	600,000
Fixed maximum amounts guaranteed by year 2019	300,000
Expires on a specified number of days after the receipt of written notice	13,500,000
No scheduled maturity date	4,000,000
Amount outstanding under guarantees that is reflected on balance sheet	200,000
Letters of credit	32,300,000
Letters of credit set to expire - 2013	3,300,000
Letters of credit set to expire - 2014	29,000,000
Outstanding letters of credit	0
Natural gas transportation and storage agreement fixed maximum amount of performance guarantee of a related party	5,000,000
Amount outstanding by a related party under the guarantee	900,000
Amount of surety bonds outstanding	$ 639,000,000

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Employee benefit plans (Tables)

3 Months Ended

Mar. 31, 2013

Employee Benefit Plans [Abstract]

Schedule of net benefit costs

Components of net periodic benefit cost for the Company's pension and other postretirement benefit plans were as follows:

							Other
							Postretirement
	Pension Benefits						Benefits
Three Months Ended March 31,	2013			2012			2013			2012
	(In thousands)
Components of net periodic benefit cost:
Service cost	$	40		$	345		$	504		$	412
Interest cost	4,018			4,554			940			1,143
Expected return on assets	(5,083		)	(5,886		)	(1,107		)	(1,244		)
Amortization of prior service cost (credit)	18			(21		)	(364		)	(272		)
Amortization of net actuarial loss	1,864			1,681			671			526
Amortization of net transition obligation	—			—			—			532
Net periodic benefit cost, including amount capitalized	857			673			644			1,097
Less amount capitalized	110			234			29			138
Net periodic benefit cost	$	747		$	439		$	615		$	959

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Business segment data

3 Months Ended

Mar. 31, 2013

Segment Reporting [Abstract]

Business segment data

Business segment data

The Company's reportable segments are those that are based on the Company's method of internal reporting, which generally segregates the strategic business units due to differences in products, services and regulation. The internal reporting of these operating segments is defined based on the reporting and review process used by the Company's chief executive officer and other management. The vast majority of the Company's operations are located within the United States. The Company also has an investment in a foreign country, which consists of Centennial Resources' equity method investment in ECTE.

The electric segment generates, transmits and distributes electricity in Montana, North Dakota, South Dakota and Wyoming. The natural gas distribution segment distributes natural gas in those states as well as in Idaho, Minnesota, Oregon and Washington. These operations also supply related value-added services.

The pipeline and energy services segment provides natural gas transportation, underground storage, processing and gathering services, as well as oil gathering, through regulated and nonregulated pipeline systems primarily in the Rocky Mountain and northern Great Plains regions of the United States. This segment is constructing a diesel topping plant to refine crude oil and also provides cathodic protection and other energy-related services.

The exploration and production segment is engaged in oil and natural gas acquisition, exploration, development and production activities in the Rocky Mountain and Mid-Continent regions of the United States and in and around the Gulf of Mexico.

The construction materials and contracting segment mines aggregates and markets crushed stone, sand, gravel and related construction materials, including ready-mixed concrete, cement, asphalt, liquid asphalt and other value-added products. It also performs integrated contracting services. This segment operates in the central, southern and western United States and Alaska and Hawaii.

The construction services segment specializes in constructing and maintaining electric and communication lines, gas pipelines, fire suppression systems, and external lighting and traffic signalization equipment. This segment also provides utility excavation services and inside electrical wiring, cabling and mechanical services, sells and distributes electrical materials, and manufactures and distributes specialty equipment.

The Other category includes the activities of Centennial Capital, which insures various types of risks as a captive insurer for certain of the Company's subsidiaries. The function of the captive insurer is to fund the deductible layers of the insured companies' general liability and automobile liability coverages. Centennial Capital also owns certain real and personal property. The Other category also includes Centennial Resources' equity method investment in ECTE.

The information below follows the same accounting policies as described in Note 1 of the Company's Notes to Consolidated Financial Statements in the 2012 Annual Report. Information on the Company's businesses was as follows:

Three Months Ended March 31, 2013	External Operating Revenues		Inter- segment Operating Revenues			Earnings on Common Stock
	(In thousands)
Electric	$	64,654	$	—		$	9,825
Natural gas distribution	331,754		—			32,518
Pipeline and energy services	27,716		18,718			2,330
	424,124		18,718			44,673
Exploration and production	115,363		9,812			20,284
Construction materials and contracting	161,977		4,294			(20,582		)
Construction services	229,806		1,574			11,664
Other	334		1,818			305
	507,480		17,498			11,671
Intersegment eliminations	—		(36,216		)	—
Total	$	931,604	$	—		$	56,344

Three Months Ended March 31, 2012	External Operating Revenues		Inter- segment Operating Revenues			Earnings on Common Stock
	(In thousands)
Electric	$	57,963	$	—		$	7,559
Natural gas distribution	307,891		—			25,508
Pipeline and energy services	29,227		20,409			2,760
	395,081		20,409			35,827
Exploration and production	88,494		11,328			12,930
Construction materials and contracting	149,268		151			(24,932		)
Construction services	218,151		25			11,403
Other	1,813		327			391
	457,726		11,831			(208		)
Intersegment eliminations	—		(32,240		)	—
Total	$	852,807	$	—		$	35,619

Earnings from electric, natural gas distribution and pipeline and energy services are substantially all from regulated operations. Earnings from exploration and production, construction materials and contracting, construction services and other are all from nonregulated operations.

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Contingencies Commitment and Contingencies Disclosure (Tables)

3 Months Ended

Mar. 31, 2013

Commitments and Contingencies Disclosure [Abstract]

Limited liability project reflected on consolidated balance sheet [Table Text Block]

The total assets and liabilities of Dakota Prairie Refining reflected on the Company's Consolidated Balance Sheets were as follows:

	March 31, 2013
	(In thousands)
ASSETS
Current assets:
Cash and cash equivalents	$	10,793
Total current assets	10,793
Net property, plant and equipment	27,356
Total assets	$	38,149
LIABILITIES
Current liabilities:
Accounts payable	$	10,948
Total liabilities	$	10,948

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Regulatory matters and revenues subject to refund

3 Months Ended

Mar. 31, 2013

Regulated Operations [Abstract]

Regulatory matters and revenues subject to refund

Regulatory matters and revenues subject to refund

On September 26, 2012, Montana-Dakota filed an application with the MTPSC for a natural gas rate increase. Montana-Dakota requested a total increase of $3.5 million annually or approximately 5.9 percent above current rates. The requested increase includes the costs associated with the increased investment in facilities, including ongoing investment in new and replacement distribution facilities, the landfill gas production facility, a region operations building, automated meter reading and a new customer billing system. Montana-Dakota requested an interim increase, subject to refund, of $1.7 million or approximately 2.9 percent. On April 12, 2013, the MTPSC issued an interim order authorizing an interim increase of $850,000 annually to be effective with service rendered on or after April 15, 2013, subject to refund. A hearing scheduled for May 1, 2013, was postponed with no date currently set.

On December 21, 2012, Montana-Dakota filed an application with the SDPUC for a natural gas rate increase. Montana-Dakota requested a total increase of $1.5 million annually or approximately 3.3 percent above current rates. The requested increase includes the costs associated with the increased investment in facilities, including ongoing investment in new and replacement distribution facilities, the landfill gas production facility, an operations building, automated meter reading and a new customer billing system.

On February 11, 2013, Montana-Dakota filed an application with the NDPSC for approval of an environmental cost recovery rider for recovery of Montana-Dakota's share of the costs resulting from the environmental retrofit required to be installed at the Big Stone Station. The costs proposed to be recovered are associated with the ongoing construction costs for the installation of the BART air-quality control system. On February 27, 2013, the NDPSC suspended the filing pending further review.

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Consolidated Statements of Cash Flows (USD $) In Thousands, unless otherwise specified	3 Months Ended
	Mar. 31, 2013	Mar. 31, 2012
Operating activities:
Net income	$ 56,515	$ 35,790
Loss from discontinued operations, net of tax	(77)	(100)
Income from continuing operations	56,592	35,890
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation, depletion and amortization	93,561	85,380
Earnings, net of distributions, from equity method investments	1,277	1,181
Deferred income taxes	44,663	32,596
Changes in current assets and liabilities, net of acquisitions:
Receivables	32,206	101,917
Inventories	(19,126)	(38,357)
Other current assets	(25,855)	(21,556)
Accounts payable	(35,091)	(29,851)
Other current liabilities	(7,338)	(33,751)
Other noncurrent changes	(4,318)	(8,349)
Net cash provided by continuing operations	136,571	125,100
Net cash provided by (used in) discontinued operations	303	(107)
Net cash provided by operating activities	136,874	124,993
Investing activities:
Capital expenditures	(188,475)	(174,429)
Acquisitions, net of cash acquired	0	(242)
Net proceeds from sale or disposition of property and other	18,176	18,256
Investments	(514)	(27)
Net cash used in continuing operations	(170,813)	(156,442)
Net cash provided by discontinued operations	0	0
Net cash used in investing activities	(170,813)	(156,442)
Financing activities:
Issuance of short-term borrowings	9,300	0
Issuance of long-term debt	112,015	0
Repayment of long-term debt	(67,123)	(8,297)
Proceeds from issuance of common stock	0	88
Dividends paid	(171)	(31,794)
Excess tax benefit on stock-based compensation	0	26
Contribution from noncontrolling interest	5,000	0
Net cash provided by (used in) continuing operations	59,021	(39,977)
Net cash provided by discontinued operations	0	0
Net cash provided by (used in) financing activities	59,021	(39,977)
Effect of exchange rate changes on cash and cash equivalents	25	43
Increase (decrease) in cash and cash equivalents	25,107	(71,383)
Cash and cash equivalents - beginning of year	49,042	162,772
Cash and cash equivalents - end of year	$ 74,149	$ 91,389

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Consolidated Statements of Comprehensive Income (USD $) In Thousands, unless otherwise specified	3 Months Ended
	Mar. 31, 2013	Mar. 31, 2012
Consolidated Statements of Comprehensive Income [Abstract]
Net income (loss)	$ 56,515	$ 35,790
Net unrealized loss on derivative instruments qualifying as hedges:
Net unrealized loss on derivative instruments arising during the period, net of tax of $(3,168) and $(2,225) in 2013 and 2012, respectively	(5,849)	(3,770)
Less: Reclassification adjustment for gain on derivative instruments included in net income, net of tax	2,772	2,329
Net unrealized loss on derivative instruments qualifying as hedges	(8,621)	(6,099)
Net unrealized gain (loss) on available-for-sale investments:
Net unrealized loss on available-for-sale investments arising during the period, net of tax of $(24) and $(2) in 2013 and 2012, respectively	(44)	(4)
Less: Reclassification adjustment for loss on available-for-sale investments included in net income, net of tax of $(19) and $(16) in 2013 and 2012, respectively	(35)	(30)
Net unrealized gain (loss) on available-for-sale investments	(9)	26
Amortization of postretirement liability losses included in net periodic benefit cost, net of tax	648	0
Foreign currency translation adjustment, net of tax of $37 and $138 in 2013 and 2012, respectively	88	144
Other comprehensive loss	(7,894)	(5,929)
Comprehensive income	$ 48,621	$ 29,861

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Equity method investments

3 Months Ended

Mar. 31, 2013

Equity Method Investments and Joint Ventures [Abstract]

Equity method investments

Equity method investments

Investments in companies in which the Company has the ability to exercise significant influence over operating and financial policies are accounted for using the equity method. The Company's equity method investments at March 31, 2013, include ECTE.

In August 2006, MDU Brasil acquired ownership interests in the Brazilian Transmission Lines. The electric transmission lines are primarily in northeastern and southern Brazil. The transmission contracts provide for revenues denominated in the Brazilian Real, annual inflation adjustments and change in tax law adjustments. The functional currency for the Brazilian Transmission Lines is the Brazilian Real.

In 2009, multiple sales agreements were signed for the Company to sell its ownership interest in the Brazilian Transmission Lines. In November 2010, the Company completed the sale of its entire ownership interest in ENTE and ERTE and 59.96 percent of the Company's ownership interest in ECTE. The remaining interest in ECTE is being purchased over a four-year period. In August 2012 and November 2011, the Company completed the sale of one-fourth of the remaining interest in each year. Alusa, CEMIG and CELESC hold the remaining ownership interests in ECTE.

At March 31, 2013 and 2012, and December 31, 2012, the equity method investments had total assets of $142.9 million, $105.3 million and $129.0 million, respectively, and long-term debt of $63.9 million, $35.9 million and $65.5 million, respectively. The Company's investment in its equity method investments was approximately $5.7 million, $8.2 million and $6.9 million, including undistributed earnings of $2.2 million, $2.2 million and $3.4 million, at March 31, 2013 and 2012, and December 31, 2012, respectively.

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Document And Entity Information	3 Months Ended
	Mar. 31, 2013	Apr. 30, 2013
Entity Information [Line Items]
Entity Registrant Name	MDU RESOURCES GROUP INC
Entity Central Index Key	0000067716
Current Fiscal Year End Date	--12-31
Entity Filer Category	Large Accelerated Filer
Entity Common Stock, Shares Outstanding		188,830,529
Document Fiscal Year Focus	2013
Document Fiscal Period Focus	Q1
Document Type	10-Q
Amendment Flag	false
Document Period End Date	Mar. 31, 2013

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Goodwill and other intangible assets

3 Months Ended

Mar. 31, 2013

Goodwill and Intangible Assets Disclosure [Abstract]

Goodwill and other intangible assets

Goodwill and other intangible assets

The changes in the carrying amount of goodwill were as follows:

Three Months Ended March 31, 2013	Balance as of January 1, 2013*		Goodwill Acquired During the Year		Balance as of March 31, 2013*
	(In thousands)
Natural gas distribution	$	345,736	$	—	$	345,736
Pipeline and energy services	9,737		—		9,737
Construction materials and contracting	176,290		—		176,290
Construction services	104,276		—		104,276
Total	$	636,039	$	—	$	636,039

* Balance is presented net of accumulated impairment of $12.3 million at the pipeline and energy services segment, which occurred in prior periods.

Three Months Ended March 31, 2012	Balance as of January 1, 2012*		Goodwill Acquired During the Year**		Balance as of March 31, 2012*
	(In thousands)
Natural gas distribution	$	345,736	$	—	$	345,736
Pipeline and energy services	9,737		—		9,737
Construction materials and contracting	176,290		—		176,290
Construction services	103,168		458		103,626
Total	$	634,931	$	458	$	635,389

* Balance is presented net of accumulated impairment of $12.3 million at the pipeline and energy services segment, which occurred in prior periods.

** Includes contingent consideration that was not material related to an acquisition in a prior period.

Year Ended December 31, 2012	Balance as of January 1, 2012*		Goodwill Acquired During the Year**		Balance as of December 31, 2012*
	(In thousands)
Natural gas distribution	$	345,736	$	—	$	345,736
Pipeline and energy services	9,737		—		9,737
Construction materials and contracting	176,290		—		176,290
Construction services	103,168		1,108		104,276
Total	$	634,931	$	1,108	$	636,039

  * Balance is presented net of accumulated impairment of $12.3 million at the pipeline and energy services segment, which occurred in prior periods.

** Includes contingent consideration that was not material related to an acquisition in a prior period.

Other amortizable intangible assets were as follows:

	March 31, 2013			March 31, 2012			December 31, 2012
	(In thousands)
Customer relationships	$	21,310		$	21,010		$	21,310
Accumulated amortization	(12,211		)	(10,197		)	(11,701		)
	9,099			10,813			9,609
Noncompete agreements	7,236			7,086			7,236
Accumulated amortization	(5,439		)	(4,921		)	(5,326		)
	1,797			2,165			1,910
Other	10,979			11,442			10,979
Accumulated amortization	(5,557		)	(4,429		)	(5,369		)
	5,422			7,013			5,610
Total	$	16,318		$	19,991		$	17,129

Amortization expense for amortizable intangible assets for the three months ended March 31, 2013 and 2012, was $800,000 and $900,000, respectively. Estimated amortization expense for amortizable intangible assets is $3.7 million in 2013, $3.5 million in 2014, $2.6 million in 2015, $2.2 million in 2016, $1.9 million in 2017 and $3.2 million thereafter.

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Consolidated Statements of Comprehensive Income - Parenthetical (USD $) In Thousands, unless otherwise specified	3 Months Ended
	Mar. 31, 2013	Mar. 31, 2012
Net unrealized loss on derivative instruments arising during the period, tax	$ (3,168)	$ (2,225)
Less: Reclassification adjustment for gain on derivative instruments included in net income, tax	1,626	1,366
Net unrealized gains on available-for-sale investments arising during the period, tax	(24)	(2)
Less: Reclassification adjustment for loss on available-for-sale investments included in net income, tax	(19)	(16)
Amortization of postretirement liability losses included in net periodic benefit cost, tax	319	0
Foreign currency translation adjustment, tax	$ 37	$ 138

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Earnings per common share

3 Months Ended

Mar. 31, 2013

Earnings Per Share [Abstract]

Earnings per common share

Earnings per common share

Basic earnings per common share were computed by dividing earnings on common stock by the weighted average number of shares of common stock outstanding during the applicable period. Diluted earnings per common share were computed by dividing earnings on common stock by the total of the weighted average number of shares of common stock outstanding during the applicable period, plus the effect of outstanding performance share awards. Common stock outstanding includes issued shares less shares held in treasury. Net income was the same for both the basic and diluted earnings per share calculations. A reconciliation of the weighted average common shares outstanding used in the basic and diluted earnings per share calculation was as follows:

	Three Months Ended
	March 31,
	2013	2012
	(In thousands)
Weighted average common shares outstanding - basic	188,831	188,811
Effect of dilutive stock options and performance share awards	391	371
Weighted average common shares outstanding - diluted	189,222	189,182
Shares excluded from the calculation of diluted earnings per share	—	—

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Inventories and natural gas in storage

3 Months Ended

Mar. 31, 2013

Inventories and natural gas in storage [Abstract]

Inventories and natural gas in storage

Inventories and natural gas in storage

Inventories, other than natural gas in storage for the Company's regulated operations, were stated at the lower of average cost or market value. Natural gas in storage for the Company's regulated operations is generally carried at average cost, or cost using the last-in, first-out method. The portion of the cost of natural gas in storage expected to be used within one year was included in inventories. Inventories consisted of:

	March 31, 2013		March 31, 2012		December 31, 2012
	(In thousands)
Aggregates held for resale	$	98,120	$	85,958	$	87,715
Asphalt oil	94,332		82,949		67,480
Materials and supplies	75,868		68,369		69,390
Merchandise for resale	24,342		28,459		31,172
Natural gas in storage (current)	12,811		15,475		29,030
Other	29,399		32,131		32,628
Total	$	334,872	$	313,341	$	317,415

The remainder of natural gas in storage, which largely represents the cost of gas required to maintain pressure levels for normal operating purposes, was included in other assets and was $49.6 million, $50.3 million, and $49.7 million at March 31, 2013 and 2012, and December 31, 2012, respectively.

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Employee benefit plans

3 Months Ended

Mar. 31, 2013

Employee Benefit Plans [Abstract]

Pension and Other Postretirement Benefits Disclosure

Employee benefit plans

The Company has noncontributory defined benefit pension plans and other postretirement benefit plans for certain eligible employees. Components of net periodic benefit cost for the Company's pension and other postretirement benefit plans were as follows:

							Other
							Postretirement
	Pension Benefits						Benefits
Three Months Ended March 31,	2013			2012			2013			2012
	(In thousands)
Components of net periodic benefit cost:
Service cost	$	40		$	345		$	504		$	412
Interest cost	4,018			4,554			940			1,143
Expected return on assets	(5,083		)	(5,886		)	(1,107		)	(1,244		)
Amortization of prior service cost (credit)	18			(21		)	(364		)	(272		)
Amortization of net actuarial loss	1,864			1,681			671			526
Amortization of net transition obligation	—			—			—			532
Net periodic benefit cost, including amount capitalized	857			673			644			1,097
Less amount capitalized	110			234			29			138
Net periodic benefit cost	$	747		$	439		$	615		$	959

Defined pension plan benefits to all nonunion and certain union employees hired after December 31, 2005, were discontinued. Employees that would have been eligible for defined pension plan benefits are eligible to receive additional defined contribution plan benefits. Effective January 1, 2010, all benefit and service accruals for nonunion and certain union plans were frozen. Effective June 30, 2011 and September 30, 2012, all benefit and service accruals for certain additional union employees were frozen. These employees will be eligible to receive additional defined contribution plan benefits.

In addition to the qualified plan defined pension benefits reflected in the table, the Company has unfunded, nonqualified benefit plans for executive officers and certain key management employees that generally provide for defined benefit payments at age 65 following the employee's retirement or to their beneficiaries upon death for a 15-year period. The Company's net periodic benefit cost for this plan for the three months ended March 31, 2013 and 2012, was $1.9 million and $2.1 million, respectively.

In 2012, the Company modified health care coverage for certain retirees. Effective January 1, 2013, post-65 coverage is replaced by a fixed-dollar subsidy for retirees and spouses to be used to purchase individual insurance through an exchange.

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Derivative instruments

3 Months Ended

Mar. 31, 2013

Derivative Instruments and Hedging Activities Disclosure [Abstract]

Derivative Instruments

Derivative instruments

The Company's policy allows the use of derivative instruments as part of an overall energy price, foreign currency and interest rate risk management program to efficiently manage and minimize commodity price, foreign currency and interest rate risk. As of March 31, 2013, the Company had no outstanding foreign currency hedges. The following information should be read in conjunction with Notes 1 and 7 in the Company's Notes to Consolidated Financial Statements in the 2012 Annual Report.

Cascade

Cascade has historically utilized natural gas swap agreements to manage a portion of its regulated natural gas supply portfolio in order to manage fluctuations in the price of natural gas related to core customers in accordance with authority granted by the WUTC and OPUC. Core customers consist of residential, commercial and smaller industrial customers. As of March 31, 2013 and December 31, 2012, Cascade has no outstanding swap agreements. As of March 31, 2012, Cascade held a natural gas swap agreement with total forward notional volumes of 214,000 MMBtu. The fair value of derivative instruments must be estimated as of the end of each reporting period and is recorded on the Consolidated Balance Sheets as an asset or a liability. Periodic changes in the fair market value of the derivative instruments are recorded on the Consolidated Balance Sheets as a regulatory asset or a regulatory liability, and settlements of these arrangements are expected to be recovered through the purchased gas cost adjustment mechanism. Gains and losses on the settlements of these derivative instruments are recorded as a component of purchased natural gas sold on the Consolidated Statements of Income as they are recovered through the purchased gas cost adjustment mechanism. Under the terms of these arrangements, Cascade either pays or receives settlement payments based on the difference between the fixed strike price and the monthly index price applicable to each contract. For the three months ended March 31, 2012, the change in the fair market value of the derivative instruments of $52,000 was recorded as an increase to regulatory assets.

Fidelity

At March 31, 2013 and 2012, and December 31, 2012, Fidelity held oil swap and collar agreements with total forward notional volumes of 2.8 million, 4.0 million and 2.6 million Bbl, respectively, and natural gas swap agreements with total forward notional volumes of 25.9 million, 10.9 million  and 11.0 million MMBtu, respectively. In addition, at March 31, 2012, Fidelity held natural gas basis swap agreements with total forward notional volumes of 2.6 million MMBtu. Some of these agreements were designated as cash flow hedging instruments. Fidelity utilizes these derivative instruments to manage a portion of the market risk associated with fluctuations in the price of oil and natural gas and basis differentials on its forecasted sales of oil and natural gas production.

Centennial

At March 31, 2013 and 2012, and December 31, 2012, Centennial held interest rate swap agreements with total notional amounts of $40.0 million, $60.0 million and $50.0 million, respectively, which were designated as cash flow hedging instruments. Centennial entered into these interest rate derivative instruments to manage a portion of its interest rate exposure on the forecasted issuance of long-term debt. Centennial's interest rate swap agreements have mandatory termination dates ranging from May through June 2013.

Fidelity and Centennial

The fair value of the derivative instruments must be estimated as of the end of each reporting period and is recorded on the Consolidated Balance Sheets as an asset or liability. Changes in the fair value attributable to the effective portion of hedging instruments, net of tax, are recorded in stockholders' equity as a component of accumulated other comprehensive income (loss). To the extent that the hedges are not effective, the ineffective portion of the changes in fair market value is recorded directly in earnings.

There were no components of the derivative instruments' gain or loss excluded from the assessment of hedge effectiveness. Gains and losses must be reclassified into earnings as a result of the discontinuance of cash flow hedges if it is probable that the original forecasted transactions will not occur, and there were no such reclassifications.

Gains and losses on the oil and natural gas derivative instruments are reclassified from accumulated other comprehensive income (loss) into operating revenues on the Consolidated Statements of Income at the date the oil and natural gas quantities are settled. The proceeds received for oil and natural gas production are generally based on market prices. Gains and losses on the interest rate derivatives are reclassified from accumulated other comprehensive income (loss) into interest expense on the Consolidated Statements of Income in the same period the hedged item affects earnings. The gains and losses on derivative instruments were as follows:

	Three Months Ended
	March 31,
	2013			2012
	(In thousands)
Commodity derivatives designated as cash flow hedges:
Amount of loss recognized in accumulated other comprehensive loss (effective portion), net of tax	$	(6,154	)	$	(4,659	)
Amount of gain reclassified from accumulated other comprehensive loss into operating revenues (effective portion), net of tax	2,843			2,343
Amount of loss recognized in operating revenues (ineffective portion), before tax	(1,422		)	(4,251		)
Interest rate derivatives designated as cash flow hedges:
Amount of gain recognized in accumulated other comprehensive loss (effective portion), net of tax	305			889
Amount of loss reclassified from accumulated other comprehensive loss into interest expense (effective portion), net of tax	(71		)	(14		)
Amount of loss recognized in interest expense (ineffective portion), before tax	(159		)	—
Commodity derivatives not designated as hedging instruments:
Amount of gain (loss) recognized in operating revenues, before tax	(4,410		)	55

As of March 31, 2013, the maximum term of the derivative instruments, in which the exposure to the variability in future cash flows for forecasted transactions is being hedged, is 33 months.

Based on March 31, 2013, fair values, over the next 12 months net gains of approximately $1.5 million (after tax) are estimated to be reclassified from accumulated other comprehensive income (loss) into earnings, as the hedged transactions affect earnings.

Certain of Fidelity's and Centennial's derivative instruments contain cross-default provisions that state if Fidelity or any of its affiliates or Centennial fails to make payment with respect to certain indebtedness, in excess of specified amounts, the counterparties could require early settlement or termination of derivative instruments in liability positions. The aggregate fair value of Fidelity's and Centennial's derivative instruments with credit-risk-related contingent features that are in a liability position at March 31, 2013, was $12.4 million. The aggregate fair value of assets that would have been needed to settle the instruments immediately if the credit-risk-related contingent features were triggered on March 31, 2013, was $12.4 million.

The location and fair value of the gross amount of the Company's derivative instruments on the Consolidated Balance Sheets were as follows:

Asset Derivatives	Location on Consolidated Balance Sheets	Fair Value at March 31, 2013		Fair Value at March 31, 2012		Fair Value at December 31, 2012
		(In thousands)
Designated as hedges:
Commodity derivatives	Commodity derivative instruments	$	1,623	$	25,560	$	18,084
	Other assets - noncurrent	—		537		—
		1,623		26,097		18,084
Not designated as hedges:
Commodity derivatives	Commodity derivative instruments	4,313		1,138		220
	Other assets - noncurrent	243		45		—
		4,556		1,183		220
Total asset derivatives		$	6,179	$	27,280	$	18,304

Liability Derivatives	Location on Consolidated Balance Sheets	Fair Value at March 31, 2013		Fair Value at March 31, 2012		Fair Value at December 31, 2012
		(In thousands)
Designated as hedges:
Commodity derivatives	Commodity derivative instruments	$	5,994	$	18,964	$	—
	Other liabilities - noncurrent	534		6,098		—
Interest rate derivatives	Other accrued liabilities	4,458		1,168		6,255
	Other liabilities - noncurrent	—		2,153		—
		10,986		28,383		6,255
Not designated as hedges:
Commodity derivatives	Commodity derivative instruments	1,385		1,219		—
	Other liabilities - noncurrent	74		49		—
		1,459		1,268		—
Total liability derivatives		$	12,445	$	29,651	$	6,255

All of the Company's commodity and interest rate derivative instruments at March 31, 2013 and 2012, and December 31, 2012, were subject to legally enforceable master netting agreements. However, the Company's policy is to not offset fair value amounts for derivative instruments and, as a result, the Company's derivative assets and liabilities are presented gross on the Consolidated Balance Sheets. The gross derivative assets and liabilities (excluding settlement receivables and payables that may be subject to the same master netting agreements) presented on the Consolidated Balance Sheets and the amount eligible for offset under the master netting agreements is presented in the following table:

March 31, 2013	Gross Amounts Recognized on the Consolidated Balance Sheets		Gross Amounts Not Offset on the Consolidated Balance Sheets			Net
	(In thousands)
Assets:
Commodity derivatives	$	6,179	$	(3,578	)	$	2,601
Total assets	$	6,179	$	(3,578	)	$	2,601
Liabilities:
Commodity derivatives	$	7,987	$	(3,578	)	$	4,409
Interest rate derivatives	4,458		—			4,458
Total liabilities	$	12,445	$	(3,578	)	$	8,867

March 31, 2012	Gross Amounts Recognized on the Consolidated Balance Sheets		Gross Amounts Not Offset on the Consolidated Balance Sheets			Net
	(In thousands)
Assets:
Commodity derivatives	$	27,280	$	(15,805	)	$	11,475
Total assets	$	27,280	$	(15,805	)	$	11,475
Liabilities:
Commodity derivatives	$	26,330	$	(15,805	)	$	10,525
Interest rate derivatives	3,321		—			3,321
Total liabilities	$	29,651	$	(15,805	)	$	13,846

December 31, 2012	Gross Amounts Recognized on the Consolidated Balance Sheets		Gross Amounts Not Offset on the Consolidated Balance Sheets		Net
	(In thousands)
Assets:
Commodity derivatives	$	18,304	$	—	$	18,304
Total assets	$	18,304	$	—	$	18,304
Liabilities:
Interest rate derivatives	$	6,255	$	—	$	6,255
Total liabilities	$	6,255	$	—	$	6,255

Effective April 1, 2013, the Company has elected to de-designate all of its commodity derivative contracts that existed at March 31, 2013, that had been previously designated as cash flow hedges, and has elected to discontinue hedge accounting for its commodity derivatives prospectively. As a result, Fidelity will recognize all future gains and losses from prospective changes in commodity derivative fair values immediately in earnings rather than deferring any such amounts in accumulated other comprehensive income (loss).

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Comprehensive income (loss)

3 Months Ended

Mar. 31, 2013

Comprehensive income (loss) [Abstract]

Comprehensive income (loss)

Comprehensive income (loss)

The after-tax changes in the components of accumulated other comprehensive loss as of March 31, 2013, were as follows:

	Net Unrealized Gain (Loss) on Derivative  Instruments  Qualifying as Hedges			Net Unrealized Gain (Loss) on Available-for-sale Investments			Postretirement  Liability Adjustment			Foreign Currency Translation Adjustment			Total Accumulated  Other Comprehensive  Loss
	(In thousands)
Balance at December 31, 2012	$	6,018		$	119		$	(54,347	)	$	(511	)	$	(48,721	)
Other comprehensive income (loss) before reclassifications	(5,849		)	(44		)	—			88			(5,805		)
Amounts reclassified from accumulated other comprehensive loss	(2,772		)	35			648			—			(2,089		)
Net current-period other comprehensive loss	(8,621		)	(9		)	648			88			(7,894		)
Balance at March 31, 2013	$	(2,603	)	$	110		$	(53,699	)	$	(423	)	$	(56,615	)

Reclassifications out of accumulated other comprehensive loss were as follows:

	Three Months Ended			Location on Consolidated Statements of Income
	March 31,
	2013
	(In thousands)
Reclassification adjustment for gain (loss) on derivative instruments included in net income
Commodity derivative instruments	$	4,513		Operating revenues
Interest rate derivative instruments	(115		)	Interest expense
	4,398
	(1,626		)	Income taxes
	2,772
Amortization of postretirement liability losses included in net periodic benefit cost	(967		)	(a)
	319			Income taxes
	(648		)
Reclassification adjustment for loss on available-for-sale investments included in net income	(54		)	Other income
	19			Income taxes
	(35		)
Total reclassifications	$	2,089

(a) Included in net periodic pension cost (see Note 16 for additional details).

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Commitment and contingencies variable interest entities (Details 4) (USD $)	Mar. 31, 2013
Dakota Prairie Refining, LLC [Member]
Variable Interest Entities [Line Items]
Percent of ownership	50.00%
Portion of capital commitment	$ 150,000,000
Partner portion of capital commitment	75,000,000
Term loan for project debt financing	75,000,000
Dakota Prairie Refining, LLC [Member] | Cash and Cash Equivalents [Member]
Variable Interest Entities [Line Items]
Limited liability entity, consolidated, carrying amount, assets	10,793,000
Dakota Prairie Refining, LLC [Member] | Total current assets [Member]
Variable Interest Entities [Line Items]
Limited liability entity, consolidated, carrying amount, assets	10,793,000
Dakota Prairie Refining, LLC [Member] | Net property, plant and equipment [Member]
Variable Interest Entities [Line Items]
Limited liability entity, consolidated, carrying amount, assets	27,356,000
Dakota Prairie Refining, LLC [Member] | Total assets [Member]
Variable Interest Entities [Line Items]
Limited liability entity, consolidated, carrying amount, assets	38,149,000
Dakota Prairie Refining, LLC [Member] | Accounts Payable [Member]
Variable Interest Entities [Line Items]
Limited liability entity, consolidated, carrying amount, liabilities	10,948,000
Dakota Prairie Refining, LLC [Member] | Total liabilities [Member]
Variable Interest Entities [Line Items]
Limited liability entity, consolidated, carrying amount, liabilities	$ 10,948,000
Fuel contract [Member]
Variable Interest Entities [Line Items]
Percent of ownership	25.00%

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Cash flow information

3 Months Ended

Mar. 31, 2013

Cash flow information [Abstract]

Cash flow information

Cash flow information

Cash expenditures for interest and income taxes were as follows:

	Three Months Ended
	March 31,
	2013			2012
	(In thousands)
Interest, net of amount capitalized	$	21,857		$	22,433
Income taxes paid (refunded), net	$	(7,246	)	$	285

Noncash investing transactions were as follows:

	March 31,
	2013		2012
	(In thousands)
Property, plant and equipment additions in accounts payable	$	92,236	$	51,739

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New accounting standards

3 Months Ended

Mar. 31, 2013

New accounting standards [Abstract]

New accounting standards

New accounting standards

Reporting of Amounts Reclassified Out of Accumulated Other Comprehensive Income In February 2013, the FASB issued guidance on the reporting of amounts reclassified out of accumulated other comprehensive income. This guidance requires an entity to report the effect of significant reclassifications out of accumulated other comprehensive income on the respective line items in net income if the amount being reclassified is required to be reclassified in its entirety to net income. Entities may present this information either on the face of the statement where net income is presented or in the notes. This guidance was effective for the Company on January 1, 2013, and is to be applied prospectively. The guidance required additional disclosures, however it did not impact the Company's results of operations, financial position or cash flows.

Disclosures about Offsetting Assets and Liabilities In December 2011, the FASB issued guidance on the disclosure requirements related to balance sheet offsetting. The new disclosure requirements relate to the nature of an entity's rights of offset and related arrangements associated with its financial instruments and derivative instruments. In January 2013, the FASB issued guidance clarifying the scope of the disclosures related to balance sheet offsetting. The amendments clarify that this guidance only applies to derivative instruments, repurchase agreements and securities lending transactions that are either offset or subject to an enforceable master netting arrangement. The guidance was effective for the Company on January 1, 2013, and must be applied retrospectively. The guidance required additional disclosures, however it did not impact the Company's results of operations, financial position or cash flows.

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Discontinued operations

3 Months Ended

Mar. 31, 2013

Discontinued Operations and Disposal Groups [Abstract]

Discontinued operations

Discontinued operations

In 2007, Centennial Resources sold CEM to Bicent. In connection with the sale, Centennial Resources had agreed to indemnify Bicent and its affiliates from certain third party claims arising out of or in connection with Centennial Resources' ownership or operation of CEM prior to the sale. In addition, Centennial had previously guaranteed CEM's obligations under a construction contract. The Company incurs legal expenses and has accrued liabilities related to this matter. These items are reflected as discontinued operations in the consolidated financial statements and accompanying notes. Discontinued operations are included in the Other category. For more information, see Note 18.

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Business segment data (Tables)

3 Months Ended

Mar. 31, 2013

Segment Reporting [Abstract]

Information on the Company's businesses

Information on the Company's businesses was as follows:

Three Months Ended March 31, 2013	External Operating Revenues		Inter- segment Operating Revenues			Earnings on Common Stock
	(In thousands)
Electric	$	64,654	$	—		$	9,825
Natural gas distribution	331,754		—			32,518
Pipeline and energy services	27,716		18,718			2,330
	424,124		18,718			44,673
Exploration and production	115,363		9,812			20,284
Construction materials and contracting	161,977		4,294			(20,582		)
Construction services	229,806		1,574			11,664
Other	334		1,818			305
	507,480		17,498			11,671
Intersegment eliminations	—		(36,216		)	—
Total	$	931,604	$	—		$	56,344

Three Months Ended March 31, 2012	External Operating Revenues		Inter- segment Operating Revenues			Earnings on Common Stock
	(In thousands)
Electric	$	57,963	$	—		$	7,559
Natural gas distribution	307,891		—			25,508
Pipeline and energy services	29,227		20,409			2,760
	395,081		20,409			35,827
Exploration and production	88,494		11,328			12,930
Construction materials and contracting	149,268		151			(24,932		)
Construction services	218,151		25			11,403
Other	1,813		327			391
	457,726		11,831			(208		)
Intersegment eliminations	—		(32,240		)	—
Total	$	852,807	$	—		$	35,619

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Fair value measurements (Details 2) (USD $) In Thousands, unless otherwise specified	Mar. 31, 2013		Dec. 31, 2012		Mar. 31, 2012
Concentration risks, percentage [Abstract]
Percentage investment in common stock of mid-cap companies	29.00%		28.00%		29.00%
Percentage investment in common stock of small-cap companies	28.00%		28.00%		29.00%
Percentage investment in common stock of large-cap companies	28.00%		29.00%		29.00%
Percentage in fixed-income and other investments	15.00%		15.00%		13.00%
Fair value, measurements, recurring [Member]
Fair value, assets and liabilities measured on recurring and nonrecurring basis [Line Items]
Assets, fair value disclosure	101,013		101,443		107,412
Liabilities, fair value disclosure	12,445		6,255		29,651
Fair value, measurements, recurring [Member] | Commodity derivative instruments, liabilities [Member]
Fair value, assets and liabilities measured on recurring and nonrecurring basis [Line Items]
Liabilities, fair value disclosure	7,987				26,330
Fair value, measurements, recurring [Member] | Interest rate swap [Member]
Fair value, assets and liabilities measured on recurring and nonrecurring basis [Line Items]
Liabilities, fair value disclosure	4,458		6,255		3,321
Fair value, measurements, recurring [Member] | Money market funds [Member]
Fair value, assets and liabilities measured on recurring and nonrecurring basis [Line Items]
Assets, fair value disclosure	31,281		24,240		9,942
Fair value, measurements, recurring [Member] | Insurance contract [Member]
Fair value, assets and liabilities measured on recurring and nonrecurring basis [Line Items]
Assets, fair value disclosure	53,334	[1]	48,898	[2]	48,704	[3]
Fair value, measurements, recurring [Member] | Auction rate securities [Member]
Fair value, assets and liabilities measured on recurring and nonrecurring basis [Line Items]
Assets, fair value disclosure					11,400
Fair value, measurements, recurring [Member] | Collateralized mortgage backed securities [Member]
Fair value, assets and liabilities measured on recurring and nonrecurring basis [Line Items]
Assets, fair value disclosure	8,879		8,195		8,070
Fair value, measurements, recurring [Member] | US Treasury securities [Member]
Fair value, assets and liabilities measured on recurring and nonrecurring basis [Line Items]
Assets, fair value disclosure	1,340		1,806		2,016
Fair value, measurements, recurring [Member] | Commodity derivative instruments , assets [Member]
Fair value, assets and liabilities measured on recurring and nonrecurring basis [Line Items]
Assets, fair value disclosure	6,179		18,304		27,280
Fair value, measurements, recurring [Member] | Fair value, inputs, level 1 [Member]
Fair value, assets and liabilities measured on recurring and nonrecurring basis [Line Items]
Assets, fair value disclosure	0		0		0
Liabilities, fair value disclosure	0		0		0
Fair value, measurements, recurring [Member] | Fair value, inputs, level 1 [Member] | Commodity derivative instruments, liabilities [Member]
Fair value, assets and liabilities measured on recurring and nonrecurring basis [Line Items]
Liabilities, fair value disclosure	0				0
Fair value, measurements, recurring [Member] | Fair value, inputs, level 1 [Member] | Interest rate swap [Member]
Fair value, assets and liabilities measured on recurring and nonrecurring basis [Line Items]
Liabilities, fair value disclosure	0		0		0
Fair value, measurements, recurring [Member] | Fair value, inputs, level 1 [Member] | Money market funds [Member]
Fair value, assets and liabilities measured on recurring and nonrecurring basis [Line Items]
Assets, fair value disclosure	0		0		0
Fair value, measurements, recurring [Member] | Fair value, inputs, level 1 [Member] | Insurance contract [Member]
Fair value, assets and liabilities measured on recurring and nonrecurring basis [Line Items]
Assets, fair value disclosure	0	[1]	0	[2]	0	[3]
Fair value, measurements, recurring [Member] | Fair value, inputs, level 1 [Member] | Auction rate securities [Member]
Fair value, assets and liabilities measured on recurring and nonrecurring basis [Line Items]
Assets, fair value disclosure					0
Fair value, measurements, recurring [Member] | Fair value, inputs, level 1 [Member] | Collateralized mortgage backed securities [Member]
Fair value, assets and liabilities measured on recurring and nonrecurring basis [Line Items]
Assets, fair value disclosure	0		0		0
Fair value, measurements, recurring [Member] | Fair value, inputs, level 1 [Member] | US Treasury securities [Member]
Fair value, assets and liabilities measured on recurring and nonrecurring basis [Line Items]
Assets, fair value disclosure	0		0		0
Fair value, measurements, recurring [Member] | Fair value, inputs, level 1 [Member] | Commodity derivative instruments , assets [Member]
Fair value, assets and liabilities measured on recurring and nonrecurring basis [Line Items]
Assets, fair value disclosure	0		0		0
Fair value, measurements, recurring [Member] | Fair value, inputs, level 2 [Member]
Fair value, assets and liabilities measured on recurring and nonrecurring basis [Line Items]
Assets, fair value disclosure	101,013		101,443		107,412
Liabilities, fair value disclosure	12,445		6,255		29,651
Fair value, measurements, recurring [Member] | Fair value, inputs, level 2 [Member] | Commodity derivative instruments, liabilities [Member]
Fair value, assets and liabilities measured on recurring and nonrecurring basis [Line Items]
Liabilities, fair value disclosure	7,987				26,330
Fair value, measurements, recurring [Member] | Fair value, inputs, level 2 [Member] | Interest rate swap [Member]
Fair value, assets and liabilities measured on recurring and nonrecurring basis [Line Items]
Liabilities, fair value disclosure	4,458		6,255		3,321
Fair value, measurements, recurring [Member] | Fair value, inputs, level 2 [Member] | Money market funds [Member]
Fair value, assets and liabilities measured on recurring and nonrecurring basis [Line Items]
Assets, fair value disclosure	31,281		24,240		9,942
Fair value, measurements, recurring [Member] | Fair value, inputs, level 2 [Member] | Insurance contract [Member]
Fair value, assets and liabilities measured on recurring and nonrecurring basis [Line Items]
Assets, fair value disclosure	53,334	[1]	48,898	[2]	48,704	[3]
Fair value, measurements, recurring [Member] | Fair value, inputs, level 2 [Member] | Auction rate securities [Member]
Fair value, assets and liabilities measured on recurring and nonrecurring basis [Line Items]
Assets, fair value disclosure					11,400
Fair value, measurements, recurring [Member] | Fair value, inputs, level 2 [Member] | Collateralized mortgage backed securities [Member]
Fair value, assets and liabilities measured on recurring and nonrecurring basis [Line Items]
Assets, fair value disclosure	8,879		8,195		8,070
Fair value, measurements, recurring [Member] | Fair value, inputs, level 2 [Member] | US Treasury securities [Member]
Fair value, assets and liabilities measured on recurring and nonrecurring basis [Line Items]
Assets, fair value disclosure	1,340		1,806		2,016
Fair value, measurements, recurring [Member] | Fair value, inputs, level 2 [Member] | Commodity derivative instruments , assets [Member]
Fair value, assets and liabilities measured on recurring and nonrecurring basis [Line Items]
Assets, fair value disclosure	6,179		18,304		27,280
Fair value, measurements, recurring [Member] | Fair value, inputs, level 3 [Member]
Fair value, assets and liabilities measured on recurring and nonrecurring basis [Line Items]
Assets, fair value disclosure	0		0		0
Liabilities, fair value disclosure	0		0		0
Fair value, measurements, recurring [Member] | Fair value, inputs, level 3 [Member] | Commodity derivative instruments, liabilities [Member]
Fair value, assets and liabilities measured on recurring and nonrecurring basis [Line Items]
Liabilities, fair value disclosure	0				0
Fair value, measurements, recurring [Member] | Fair value, inputs, level 3 [Member] | Interest rate swap [Member]
Fair value, assets and liabilities measured on recurring and nonrecurring basis [Line Items]
Liabilities, fair value disclosure	0		0		0
Fair value, measurements, recurring [Member] | Fair value, inputs, level 3 [Member] | Money market funds [Member]
Fair value, assets and liabilities measured on recurring and nonrecurring basis [Line Items]
Assets, fair value disclosure	0		0		0
Fair value, measurements, recurring [Member] | Fair value, inputs, level 3 [Member] | Insurance contract [Member]
Fair value, assets and liabilities measured on recurring and nonrecurring basis [Line Items]
Assets, fair value disclosure	0	[1]	0	[2]	0	[3]
Fair value, measurements, recurring [Member] | Fair value, inputs, level 3 [Member] | Auction rate securities [Member]
Fair value, assets and liabilities measured on recurring and nonrecurring basis [Line Items]
Assets, fair value disclosure					0
Fair value, measurements, recurring [Member] | Fair value, inputs, level 3 [Member] | Collateralized mortgage backed securities [Member]
Fair value, assets and liabilities measured on recurring and nonrecurring basis [Line Items]
Assets, fair value disclosure	0		0		0
Fair value, measurements, recurring [Member] | Fair value, inputs, level 3 [Member] | US Treasury securities [Member]
Fair value, assets and liabilities measured on recurring and nonrecurring basis [Line Items]
Assets, fair value disclosure	0		0		0
Fair value, measurements, recurring [Member] | Fair value, inputs, level 3 [Member] | Commodity derivative instruments , assets [Member]
Fair value, assets and liabilities measured on recurring and nonrecurring basis [Line Items]
Assets, fair value disclosure	0		0		0

[1] The insurance contract invests approximately 29 percent in common stock of mid-cap companies, 28 percent in common stock of small-cap companies, 28 percent in common stock of large-cap companies and 15 percent in fixed-income and other investments.

[2] The insurance contract invests approximately 28 percent in common stock of mid-cap companies, 28 percent in common stock of small-cap companies, 29 percent in common stock of large-cap companies and 15 percent in fixed-income and other investments.

[3] The insurance contract invests approximately 29 percent in common stock of mid-cap companies, 29 percent in common stock of small-cap companies, 29 percent in common stock of large-cap companies and 13 percent in fixed-income and other investments.

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Income taxes

3 Months Ended

Mar. 31, 2013

Income Tax Disclosure [Abstract]

Income taxes

Income taxes

In connection with the income tax examination for the 2007 through 2009 tax years, the Company recorded income tax expense of $2.2 million for unrecognized tax positions in the first quarter of 2012.

In addition, the Company had a reduction of deferred income tax expense of $2.5 million in the first quarter of 2012, due to a deferred income tax rate reduction related to state income tax apportionment.

It is likely that substantially all of the unrecognized tax benefits of $14.9 million, as well as interest, at March 31, 2013, will be settled in the next 12 months due to the anticipated settlement of federal and state audits.

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Subsequent events

3 Months Ended

Mar. 31, 2013

Subsequent Events [Abstract]

Subsequent events

Subsequent event

In connection with the Company's variable interest in Dakota Prairie Refining, as discussed in Note 18, Centennial has agreed to guarantee repayment of the Dakota Prairie Refining term loan, which was entered into on April 22, 2013. The term loan maturity dates range from April 2018 to April 2023.

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Derivative instruments Subject to master netting agreements (Details 4) (USD $) In Thousands, unless otherwise specified	Mar. 31, 2013	Dec. 31, 2012	Mar. 31, 2012
Derivative instruments [Line Items]
Derivative asset, fair value, gross asset	$ 6,179	$ 18,304	$ 27,280
Derivative liability fair value gross liability	12,445	6,255	29,651
Commodity derivatives [Member]
Derivative instruments [Line Items]
Derivative asset, fair value, gross asset	6,179	18,304	27,280
Gross amount not offset	(3,578)	0	(15,805)
Derivative asset, fair value, net	2,601	18,304	11,475
Total assets [Member]
Derivative instruments [Line Items]
Derivative asset, fair value, gross asset	6,179	18,304	27,280
Gross amount not offset	(3,578)	0	(15,805)
Derivative asset, fair value, net	2,601	18,304	11,475
Commodity derivatives - liabilities [Member]
Derivative instruments [Line Items]
Derivative liability fair value gross liability	7,987		26,330
Gross amount not offset	(3,578)		(15,805)
Derivative liability, fair value, net	4,409		10,525
Interest rate derivatives - liabilities [Member]
Derivative instruments [Line Items]
Derivative liability fair value gross liability	4,458	6,255	3,321
Gross amount not offset	0	0	0
Derivative liability, fair value, net	4,458	6,255	3,321
Total liabilities [Member]
Derivative instruments [Line Items]
Derivative liability fair value gross liability	12,445	6,255	29,651
Gross amount not offset	(3,578)	0	(15,805)
Derivative liability, fair value, net	$ 8,867	$ 6,255	$ 13,846

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Comprehensive income (loss) (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended
	Mar. 31, 2013	Mar. 31, 2012
Amount of gain (loss) recognized in accumulated other comprehensive loss (effective portion), net of tax	$ (5,849)	$ (3,770)
Amounts reclassified from accumulated other comprehensive gain (loss)	(2,772)	(2,329)
Net current-period other comprehensive loss	(8,621)	(6,099)
Other comprehensive income (loss) before reclassifications	(44)	(4)
Amounts reclassified from accumulated other comprehensive loss	35	30
Net current-period ither comprehensive loss	(9)	26
Amortization of postretirement liability losses included in net periodic benefit cost, net of tax	(648)	0
Net current-period other comprehensive loss	88	144
Balance at December 31, 2012	(48,721)
Other comprehensive income (loss) before reclassifications	(5,805)
Amounts reclassified from accumulated other comprehensive loss	(2,089)
Net current-period other comprehensive loss	(7,894)	(5,929)
Balance at March 31, 2013	(56,615)	(52,930)
Net unrealized gains loss on derivatives instruments qualifying as hedges [Member]
Balance at December 31, 2012	6,018
Amount of gain (loss) recognized in accumulated other comprehensive loss (effective portion), net of tax	(5,849)
Amounts reclassified from accumulated other comprehensive gain (loss)	(2,772)
Net current-period other comprehensive loss	(8,621)
Balance at March 31, 2013	(2,603)
Net unrealized gain (loss) on available for sale investments [Member]
Balance at December 31, 2012	119
Other comprehensive income (loss) before reclassifications	(44)
Amounts reclassified from accumulated other comprehensive loss	35
Net current-period ither comprehensive loss	(9)
Balance at March 31, 2013	110
Postretirement liability adjustment [Member]
Balance at December 31, 2012	(54,347)
Other comprehensive income (loss) before reclassifications	0
Amortization of postretirement liability losses included in net periodic benefit cost, net of tax	648
Net current-period other comprehensive loss	648
Balance at March 31, 2013	(53,699)
Foreign currency translation adjustment [Member]
Balance at December 31, 2012	(511)
Other comprehensive income (loss) before reclassifications	88
Amounts reclassified from accumulated other comprehensive loss	0
Net current-period other comprehensive loss	88
Balance at March 31, 2013	$ (423)

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Consolidated Balance Sheets (USD $) In Thousands, unless otherwise specified	Mar. 31, 2013		Dec. 31, 2012		Mar. 31, 2012
Current assets:
Cash and cash equivalents	$ 74,149		$ 49,042		$ 91,389
Receivables, net	635,564		678,123		539,589
Inventories	334,872		317,415		313,341
Deferred income taxes	29,885		22,846		42,239
Commodity derivative instruments	5,936		18,304		26,698
Prepayments and other current assets	68,828		42,351		64,897
Total current assets	1,149,234		1,128,081		1,078,153
Investments	106,846		103,243		113,799
Property, plant and equipment	8,303,065		8,107,751		7,798,770
Less accumulated depreciation, depletion and amortization	3,678,535		3,608,912		3,419,574
Net property, plant and equipment	4,624,530		4,498,839		4,379,196
Deferred charges and other assets:
Goodwill	636,039	[1]	636,039	[1]	635,389	[1]
Other intangible assets, net	16,318		17,129		19,991
Other	295,215		299,160		312,103
Total deferred charges and other assets	947,572		952,328		967,483
Total assets	6,828,182		6,682,491		6,538,631
Current liabilities:
Short-term borrowings	37,500		28,200		0
Long-term debt due within one year	171,094		134,108		202,215
Accounts payable	375,942		388,015		321,369
Taxes payable	55,748		46,475		51,019
Dividends payable	32,744		171		31,800
Accrued compensation	31,382		48,448		28,463
Commodity derivative instruments	7,379		0		20,183
Other accrued liabilities	205,394		204,698		255,172
Total current liabilities	917,183		850,115		910,221
Long-term debt	1,618,569		1,610,867		1,213,974
Deferred credits and other liabilities:
Deferred income taxes	802,805		755,102		798,669
Other liabilities	814,643		818,159		842,169
Total deferred credits and other liabilities	1,617,448		1,573,261		1,640,838
Equity:
Preferred stocks	15,000		15,000		15,000
Common stockholders' equity:
Shares issued - 189,369,450 at March 31, 2013 and 2012 and December 31, 2012	189,369		189,369		189,369
Other paid-in capital	1,038,970		1,039,080		1,035,800
Retained earnings	1,480,784		1,457,146		1,589,985
Accumulated other comprehensive loss	(56,615)		(48,721)		(52,930)
Treasury stock at cost - 538,921 shares	(3,626)		(3,626)		(3,626)
Total common stockholders' equity	2,648,882		2,633,248		2,758,598
Total stockholders' equity	2,663,882		2,648,248		2,773,598
Noncontrolling interest	11,100		0		0
Total equity	2,674,982		2,648,248		2,773,598
Total liabilities and equity	$ 6,828,182		$ 6,682,491		$ 6,538,631

[1] Balance is presented net of accumulated impairment of $12.3 million at the pipeline and energy services segment, which occurred in prior periods.

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Accounts receivable and allowance for doubtful accounts

3 Months Ended

Mar. 31, 2013

Accounts receivable and allowance for doubtful accounts [Abstract]

Accounts receivable and allowance for doubtful accounts

Accounts receivable and allowance for doubtful accounts

Accounts receivable consists primarily of trade receivables from the sale of goods and services which are recorded at the invoiced amount net of allowance for doubtful accounts, and costs and estimated earnings in excess of billings on uncompleted contracts. The total balance of receivables past due 90 days or more was $39.6 million, $34.6 million and $34.3 million as of March 31, 2013 and 2012, and December 31, 2012, respectively.

The allowance for doubtful accounts is determined through a review of past due balances and other specific account data. Account balances are written off when management determines the amounts to be uncollectible. The Company's allowance for doubtful accounts as of March 31, 2013 and 2012, and December 31, 2012, was $10.8 million, $12.2 million and $10.8 million, respectively.

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Enviromental matters (Details 2) (USD $)	3 Months Ended
	Mar. 31, 2013
Portland Harbor Site [Member]
Site Contingency [Line Items]
Environmental matters investigative costs	$ 70,000,000
Environmental litigation number 1 [Member]
Site Contingency [Line Items]
Site contingency, high estimate, loss exposure	11,000,000
Estimated proportional share of cleanup liability	50.00%
Accrual for environmental loss contingencies	1,300,000
Site contingency, low estimate, loss exposure	500,000
Environmental litigation number 2 [Member]
Site Contingency [Line Items]
Site contingency, high estimate, loss exposure	6,400,000
Environmental matters investigative costs	6,700,000
Accrual for environmental loss contingencies	6,400,000
Site contingency, low estimate, loss exposure	340,000
Environmental litigation number 3 [Member]
Site Contingency [Line Items]
Site contingency, loss exposure not accrued, best estimate	8,000,000
Environmental litigation number 4 [Member]
Site Contingency [Line Items]
Loss contingency, damages paid, value	$ 100,000

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Inventories and natural gas in storage (Tables)

3 Months Ended

Mar. 31, 2013

Inventories and natural gas in storage [Abstract]

Inventories

Inventories consisted of:

	March 31, 2013		March 31, 2012		December 31, 2012
	(In thousands)
Aggregates held for resale	$	98,120	$	85,958	$	87,715
Asphalt oil	94,332		82,949		67,480
Materials and supplies	75,868		68,369		69,390
Merchandise for resale	24,342		28,459		31,172
Natural gas in storage (current)	12,811		15,475		29,030
Other	29,399		32,131		32,628
Total	$	334,872	$	313,341	$	317,415

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Inventories and natural gas in storage (Details) (USD $)	Mar. 31, 2013	Dec. 31, 2012	Mar. 31, 2012
Inventories and natural gas in storage [Abstract]
Aggregates held for resale	$ 98,120,000	$ 87,715,000	$ 85,958,000
Asphalt oil	94,332,000	67,480,000	82,949,000
Materials and supplies	75,868,000	69,390,000	68,369,000
Merchandise for resale	24,342,000	31,172,000	28,459,000
Natural gas in storage (current)	12,811,000	29,030,000	15,475,000
Other	29,399,000	32,628,000	32,131,000
Total	334,872,000	317,415,000	313,341,000
Natural gas in storage noncurrent	$ 49,600,000	$ 49,700,000	$ 50,300,000

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Fair value measurements

3 Months Ended

Mar. 31, 2013

Fair Value Disclosures [Abstract]

Fair value measurements

Fair value measurements

The Company measures its investments in certain fixed-income and equity securities at fair value with changes in fair value recognized in income. The Company anticipates using these investments, which consist of an insurance contract, to satisfy its obligations under its unfunded, nonqualified benefit plans for executive officers and certain key management employees, and invests in these fixed-income and equity securities for the purpose of earning investment returns and capital appreciation. These investments, which totaled $53.3 million, $48.7 million and $48.9 million, as of March 31, 2013 and 2012, and December 31, 2012, respectively, are classified as Investments on the Consolidated Balance Sheets. The net unrealized gains on these investments were $4.4 million and $5.0 million for the three months ended March 31, 2013 and 2012, respectively. The change in fair value, which is considered part of the cost of the plan, is classified in operation and maintenance expense on the Consolidated Statements of Income.

The Company did not elect the fair value option, which records gains and losses in income, for its remaining available-for-sale securities, which include auction rate securities, mortgage-backed securities and U.S. Treasury securities. These available-for-sale securities are recorded at fair value and are classified as Investments on the Consolidated Balance Sheets. The Company's auction rate securities approximated cost and, as a result, there were no accumulated unrealized gains or losses recorded in accumulated other comprehensive income (loss) on the Consolidated Balance Sheets related to these investments. In the second quarter of 2012, the Company sold its auction rate securities at cost and did not realize any gains or losses. Unrealized gains or losses on mortgage-backed securities and U.S. Treasury securities are recorded in accumulated other comprehensive income (loss). Details of available-for-sale securities were as follows:

March 31, 2013	Cost		Gross Unrealized Gains		Gross Unrealized Losses			Fair Value
	(In thousands)
Insurance contract	$	37,270	$	16,064	$	—		$	53,334
Mortgage-backed securities	8,749		133		(3		)	8,879
U.S. Treasury securities	1,301		39		—			1,340
Total	$	47,320	$	16,236	$	(3	)	$	63,553

March 31, 2012	Cost		Gross Unrealized Gains		Gross Unrealized Losses			Fair Value
	(In thousands)
Insurance contract	$	37,250	$	11,454	$	—		$	48,704
Auction rate securities	11,400		—		—			11,400
Mortgage-backed securities	7,952		119		(1		)	8,070
U.S. Treasury securities	1,968		49		(1		)	2,016
Total	$	58,570	$	11,622	$	(2	)	$	70,190

December 31, 2012	Cost		Gross Unrealized Gains		Gross Unrealized Losses			Fair Value
	(In thousands)
Insurance contract	$	37,250	$	11,648	$	—		$	48,898
Mortgage-backed securities	8,054		144		(3		)	8,195
U.S. Treasury securities	1,763		43		—			1,806
Total	$	47,067	$	11,835	$	(3	)	$	58,899

The fair value of the Company's money market funds approximates cost.

Fair value is defined as the price that would be received to sell an asset or paid to transfer a liability (an exit price) in an orderly transaction between market participants at the measurement date. The ASC establishes a hierarchy for grouping assets and liabilities, based on the significance of inputs.

The estimated fair values of the Company's assets and liabilities measured on a recurring basis are determined using the market approach.

The Company's Level 2 money market funds consist of investments in short-term unsecured promissory notes and the value is based on comparable market transactions taking into consideration the credit quality of the issuer. The estimated fair value of the Company's Level 2 mortgage-backed securities and U.S. Treasury securities are based on comparable market transactions, other observable inputs or other sources, including pricing from outside sources.

The estimated fair value of the Company's Level 2 insurance contract is based on contractual cash surrender values that are determined primarily by investments in managed separate accounts of the insurer. These amounts approximate fair value. The managed separate accounts are valued based on other observable inputs or corroborated market data.

The estimated fair value of the Company's Level 2 commodity derivative instruments is based upon futures prices, volatility and time to maturity, among other things. Counterparty statements are utilized to determine the value of the commodity derivative instruments and are reviewed and corroborated using various methodologies and significant observable inputs. The Company's and the counterparties' nonperformance risk is also evaluated.

The estimated fair value of the Company's Level 2 interest rate derivative instruments is measured using quoted market prices or pricing models using prevailing market interest rates as of the measurement date. Counterparty statements are utilized to determine the value of the interest rate derivative instruments and are reviewed and corroborated using various methodologies and significant observable inputs. The Company's and the counterparties' nonperformance risk is also evaluated.

Though the Company believes the methods used to estimate fair value are consistent with those used by other market participants, the use of other methods or assumptions could result in a different estimate of fair value. For the three months ended March 31, 2013 and 2012, there were no transfers between Levels 1 and 2.

The Company's assets and liabilities measured at fair value on a recurring basis are as follows:

	Fair Value Measurements at March 31, 2013, Using
	Quoted Prices in Active Markets for Identical Assets (Level 1)		Significant Other Observable Inputs (Level 2)		Significant Unobservable Inputs (Level 3)		Balance at March 31, 2013
	(In thousands)
Assets:
Money market funds	$	—	$	31,281	$	—	$	31,281
Available-for-sale securities:
Insurance contract*	—		53,334		—		53,334
Mortgage-backed securities	—		8,879		—		8,879
U.S. Treasury securities	—		1,340		—		1,340
Commodity derivative instruments	—		6,179		—		6,179
Total assets measured at fair value	$	—	$	101,013	$	—	$	101,013
Liabilities:
Commodity derivative instruments	$	—	$	7,987	$	—	$	7,987
Interest rate derivative instruments	—		4,458		—		4,458
Total liabilities measured at fair value	$	—	$	12,445	$	—	$	12,445

*  The insurance contract invests approximately 29 percent in common stock of mid-cap companies, 28 percent in common stock of small-cap companies, 28 percent in common stock of large-cap companies and 15 percent in fixed-income and other investments.

	Fair Value Measurements at March 31, 2012, Using
	Quoted Prices in Active Markets for Identical Assets (Level 1)		Significant Other Observable Inputs (Level 2)		Significant Unobservable Inputs (Level 3)		Balance at March 31, 2012
	(In thousands)
Assets:
Money market funds	$	—	$	9,942	$	—	$	9,942
Available-for-sale securities:
Insurance contract*	—		48,704		—		48,704
Auction rate securities	—		11,400		—		11,400
Mortgage-backed securities	—		8,070		—		8,070
U.S. Treasury securities	—		2,016		—		2,016
Commodity derivative instruments	—		27,280		—		27,280
Total assets measured at fair value	$	—	$	107,412	$	—	$	107,412
Liabilities:
Commodity derivative instruments	$	—	$	26,330	$	—	$	26,330
Interest rate derivative instruments	—		3,321		—		3,321
Total liabilities measured at fair value	$	—	$	29,651	$	—	$	29,651

*  The insurance contract invests approximately 29 percent in common stock of mid-cap companies, 29 percent in common stock of small-cap companies, 29 percent in common stock of large-cap companies and 13 percent in fixed-income and other investments.

	Fair Value Measurements at December 31, 2012, Using
	Quoted Prices in Active Markets for Identical Assets (Level 1)		Significant Other Observable Inputs (Level 2)		Significant Unobservable Inputs  (Level 3)		Balance at December 31, 2012
	(In thousands)
Assets:
Money market funds	$	—	$	24,240	$	—	$	24,240
Available-for-sale securities:
Insurance contract*	—		48,898		—		48,898
Mortgage-backed securities	—		8,195		—		8,195
U.S. Treasury securities	—		1,806		—		1,806
Commodity derivative instruments	—		18,304		—		18,304
Total assets measured at fair value	$	—	$	101,443	$	—	$	101,443
Liabilities:
Interest rate derivative instruments	$	—	$	6,255	$	—	$	6,255
Total liabilities measured at fair value	$	—	$	6,255	$	—	$	6,255

* The insurance contract invests approximately 28 percent in common stock of mid-cap companies, 28 percent in common stock of small-cap companies, 29 percent in common stock of large-cap companies and 15 percent in fixed-income and other investments.

The Company's long-term debt is not measured at fair value on the Consolidated Balance Sheets and the fair value is being provided for disclosure purposes only. The fair value was based on discounted future cash flows using current market interest rates. The estimated fair value of the Company's Level 2 long-term debt was as follows:

	Carrying Amount		Fair Value
	(In thousands)
Long-term debt at March 31, 2013	$	1,789,663	$	1,925,859
Long-term debt at March 31, 2012	$	1,416,189	$	1,578,395
Long-term debt at December 31, 2012	$	1,744,975	$	1,888,135

The carrying amounts of the Company's remaining financial instruments included in current assets and current liabilities approximate their fair values.