Fair Value (Fair Value Of Assets And Liabilities Measured On Recurring Basis) (Details) (USD $) In Thousands, unless otherwise specified	Dec. 31, 2013		Dec. 31, 2012		Dec. 31, 2011	Dec. 31, 2010
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Asset	$ 89,132		$ 89,297
Money Market Funds, Amortized Cost	11,180	[1]	15,084
Money Market Funds, at Carrying Value	11,180
Securities available for sale:	69,361		59,321
Liability	89,675		143,766
Cash and cash equivalents	82,574		75,464		74,662	69,413
Fixed Income Securities [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Cash and cash equivalents	700		800
Fair Value, Measurements, Recurring [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Foreign currency derivatives	1		0
Interest rate swaps	33,543		7,265
Money Market Funds, at Carrying Value	11,180		15,084
Funds held in trust account of Spokane Energy	1,600		1,600
Total	127,991		96,467
Foreign currency derivative liabilities at fair value	0		27
Interest Rate Derivative Liabilities, at Fair Value			1,406
Total	29,231		57,259
Fair Value, Measurements, Recurring [Member] | Energy commodity derivatives [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Asset	3,876		5,232
Liability	12,796		33,275
Fair Value, Measurements, Recurring [Member] | Natural Gas Exchange Agreements [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Liability	1,219		2,379
Fair Value, Measurements, Recurring [Member] | Power Exchange Agreements [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Asset	0		0
Liability	14,441		18,692
Fair Value, Measurements, Recurring [Member] | Power Option Agreement [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Liability	775		1,480
Fair Value, Measurements, Recurring [Member] | U.S. Government Agency [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Securities available for sale:	61,078		48,496
Fair Value, Measurements, Recurring [Member] | Municipal [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Securities available for sale:	3,518		848
Fair Value, Measurements, Recurring [Member] | Corporate fixed income - financial [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Securities available for sale:	3,000		5,026
Fair Value, Measurements, Recurring [Member] | Corporate fixed income - industrial [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Securities available for sale:	765		3,936
Fair Value, Measurements, Recurring [Member] | Certificates of deposits [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Securities available for sale:	1,000		1,015
Fair Value, Measurements, Recurring [Member] | Fixed Income Securities [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Deferred compensation assets:	1,960	[2]	2,010	[2]
Fair Value, Measurements, Recurring [Member] | Equity Securities [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Deferred compensation assets:	6,470	[2]	5,955	[2]
Fair Value, Measurements, Recurring [Member] | Level 1 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Money Market Funds, at Carrying Value	11,180		15,084
Funds held in trust account of Spokane Energy	1,600		1,600
Total	21,210		24,649
Total	0		0
Fair Value, Measurements, Recurring [Member] | Level 1 [Member] | Fixed Income Securities [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Deferred compensation assets:	1,960	[2]	2,010	[2]
Fair Value, Measurements, Recurring [Member] | Level 1 [Member] | Equity Securities [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Deferred compensation assets:	6,470	[2]	5,955	[2]
Fair Value, Measurements, Recurring [Member] | Level 2 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Foreign currency derivatives	7		7
Interest rate swaps	33,543		7,265
Total	158,154		148,233
Foreign currency derivative liabilities at fair value	6		34
Interest Rate Derivative Liabilities, at Fair Value			1,406
Total	72,901		120,830
Fair Value, Measurements, Recurring [Member] | Level 2 [Member] | Energy commodity derivatives [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Asset	55,243		81,640
Liability	72,895		119,390
Fair Value, Measurements, Recurring [Member] | Level 2 [Member] | U.S. Government Agency [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Securities available for sale:	61,078		48,496
Fair Value, Measurements, Recurring [Member] | Level 2 [Member] | Municipal [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Securities available for sale:	3,518		848
Fair Value, Measurements, Recurring [Member] | Level 2 [Member] | Corporate fixed income - financial [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Securities available for sale:	3,000		5,026
Fair Value, Measurements, Recurring [Member] | Level 2 [Member] | Corporate fixed income - industrial [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Securities available for sale:	765		3,936
Fair Value, Measurements, Recurring [Member] | Level 2 [Member] | Certificates of deposits [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Securities available for sale:	1,000		1,015
Fair Value, Measurements, Recurring [Member] | Level 3 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total	339		385
Total	16,774		22,936
Fair Value, Measurements, Recurring [Member] | Level 3 [Member] | Natural Gas Exchange Agreements [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Liability	1,219		2,379
Fair Value, Measurements, Recurring [Member] | Level 3 [Member] | Power Exchange Agreements [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Asset	339		385
Liability	14,780		19,077
Fair Value, Measurements, Recurring [Member] | Level 3 [Member] | Power Option Agreement [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Liability	775		1,480
Fair Value, Measurements, Recurring [Member] | Counterparty Netting [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Foreign currency derivatives	(6)	[3]	(7)	[3]
Total	(51,712)	[3]	(76,800)	[3]
Foreign currency derivative liabilities at fair value	(6)		(7)
Total	(60,444)	[3]	(86,507)	[3]
Fair Value, Measurements, Recurring [Member] | Counterparty Netting [Member] | Energy commodity derivatives [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Asset	(51,367)	[3]	(76,408)	[3]
Liability	(60,099)	[3]	(86,115)	[3]
Fair Value, Measurements, Recurring [Member] | Counterparty Netting [Member] | Natural Gas Exchange Agreements [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Liability			0	[3]
Fair Value, Measurements, Recurring [Member] | Counterparty Netting [Member] | Power Exchange Agreements [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Asset	(339)		(385)	[3]
Liability	$ (339)		$ (385)	[3]

[1] Amortized cost represents the original purchase price of the investments, plus or minus any amortized purchase premiums or accreted purchase discounts.

[2] These assets are trading securities and are included in other property and investments-net on the Consolidated Balance Sheets.

[3] The Company is permitted to net derivative assets and derivative liabilities with the same counterparty when a legally enforceable master netting agreement exists. In addition, the Company nets derivative assets and derivative liabilities against any payables and receivables for cash collateral held or placed with these same counterparties.