Consolidated Balance Sheets (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2012		Dec. 31, 2011
Property, Plant and Equipment:
Utility Plant, at original cost	$ 1,658,790		$ 1,515,274
Accumulated Depreciation	(373,199)		(357,245)
Nonutility Property and Equipment, at cost	328,638		221,051
Accumulated Depreciation	(36,208)		(26,687)
Property, Plant and Equipment - Net	1,578,021		1,352,393
Investments:
Available-for-Sale Securities	7,538		6,677
Restricted	17,903		18,658
Investment in Affiliates	75,825		31,815
Total Investments	101,266		57,150
Current Assets:
Cash and Cash Equivalents	4,638		7,538
Accounts Receivable	195,293		135,253
Unbilled Revenues	40,938		42,961
Provision for Uncollectibles	(5,924)		(5,337)
Notes Receivable - Affiliate	39,495		2,747
Natural Gas in Storage, average cost	55,517		68,823
Materials and Supplies, average cost	2,618		2,794
Deferred Income Taxes - Net	0		12,779
Prepaid Taxes	26,187		22,303
Derivatives - Energy Related Assets	24,242		37,461
Other Prepayments and Current Assets	11,833		13,287
Total Current Assets	394,837		340,609
Regulatory and Other Noncurrent Assets:
Regulatory Assets	352,656		315,221
Derivatives - Energy Related Assets	12,297		8,135
Unamortized Debt Issuance Costs	8,226		7,009
Notes Receivable - Affiliate	117,188		111,946
Contract Receivables	13,985		13,280
Other	52,964		41,767
Total Regulatory and Other Noncurrent Assets	557,316		497,358
Total Assets	2,631,440		2,247,510
Equity:
Balance at Beginning of Year	37,765		37,341
Common Stock Issued or Granted Under Stock Plans	1,802		424
Balance at End of Year	39,567		37,765
Premium on Common Stock	345,807		273,303
Treasury Stock (at par)	(182)		(193)
Accumulated Other Comprehensive Loss	(31,105)		(28,438)
Retained Earnings	382,127		341,677
Total Equity	736,214		624,114
Long-Term Debt	601,400	[1]	424,213	[1]
Total Capitalization	1,337,614		1,048,327
Current Liabilities:
Notes Payable	338,900		321,400
Current Portion of Long-Term Debt	25,000	[1]	2,187	[1]
Accounts Payable	193,331		153,666
Customer Deposits and Credit Balances	17,757		24,914
Environmental Remediation Costs	21,026		24,721
Taxes Accrued	2,156		3,168
Derivatives - Energy Related Liabilities	23,828		38,738
Deferred Income Taxes - Net	10,812		0
Deferred Contract Revenues	0		996
Interest Accrued	6,635		6,408
Pension Benefits	1,272		1,275
Other Current Liabilities	11,127		10,498
Total Current Liabilities	651,844		587,971
Deferred Credits and Other Noncurrent Liabilities:
Deferred Income Taxes - Net	289,489		295,434
Investment Tax Credits	618		905
Pension and Other Postretirement Benefits	105,168		109,021
Environmental Remediation Costs	91,072		69,439
Asset Retirement Obligations	39,385		29,430
Derivatives - Energy Related Liabilities	5,403		7,367
Derivatives - Other	13,462		14,046
Regulatory Liabilities	56,517		48,311
Finance Obligation	21,646		22,549
Other	19,222		14,710
Total Deferred Credits and Other Noncurrent Liabilities	641,982		611,212
Commitments and Contingencies (Note 15)
Total Capitalization and Liabilities	$ 2,631,440		$ 2,247,510

[1] Long-term debt maturities and sinking funds requirements for the succeeding five years are as follows (in thousands): 2013, $25,000; 2014, $21,000; 2015, $74,909; 2016, $27,909; 2017, $31,909.