Consolidated Balance Sheets (USD $) In Thousands, unless otherwise specified	Dec. 31, 2011	Dec. 31, 2010
Current assets:
Cash and cash equivalents	$ 5,833	$ 3,457
Restricted cash	0	924
Accounts receivable	77,449	67,969
Unbilled Receivables, Current	61,925	64,803
Allowance for uncollectible accounts	(2,895)	(2,950)
Regulatory assets	94,673	52,714
Derivative instruments	2,853	2,245
Inventory	74,363	80,385
Gas Reserves	4,463	0
Income taxes receivable	7,045	41,066
Other current assets	22,980	19,652
Total current assets	348,689	330,265
Non-current assets:
Property, plant and equipment	2,661,102	2,576,402
Less: Accumulated depreciation	767,226	722,239
Total property, plant and equipment - net	1,893,876	1,854,163
Gas Reserves	47,451	0
Regulatory Assets	371,392	348,897
Derivative instruments	0	628
Other investments	68,263	69,094
Restricted cash	4,000	0
Other non-current assets	12,903	13,569
Total non-current assets	2,397,885	2,286,351
Total assets	2,746,574	2,616,616
Capitalization:
Common stock - no par value; authorized 100,000 shares; issued and outstanding 26,756 and 26,668 at December 31, 2011 and 2010, respectively	348,383	342,978
Retained earnings	373,905	356,727
Accumulated other comprehensive income (loss)	(7,800)	(6,604)
Total common stock equity	714,488	693,101
Long-term debt	641,700	591,700
Total capitalization	1,356,188	1,284,801
Current liabilities:
Short-term debt	141,600	257,435
Current maturities of long-term debt	40,000	10,000
Accounts payable	86,300	93,243
Taxes accrued	10,747	10,579
Interest accrued	5,857	5,182
Regulatory liabilities	31,046	17,828
Derivative instruments	57,317	38,437
Other current liabilities	41,597	35,457
Total current liabilities	414,464	468,161
Deferred credits and other non-current liabilities:
Deferred tax liabilities	413,209	373,409
Regulatory Liabilities	278,382	258,031
Pension and other postretirement benefit liabilities	201,530	144,250
Derivative instruments	6,536	17,022
Other non-current liabilities	76,265	70,942
Total deferred credits and other non-current liabilities	975,922	863,654
Commitments and contingencies (see Note 15)	0	0
Total capitalization and liabilities	$ 2,746,574	$ 2,616,616