Consolidated Balance Sheets (USD $) In Thousands	Jun. 30, 2011	Dec. 31, 2010	Jun. 30, 2010
Current assets:
Cash and cash equivalents	$ 3,700	$ 3,457	$ 7,142
Restricted cash	925	924	929
Accounts receivable	39,104	67,969	42,781
Accrued unbilled revenue	15,031	64,803	16,419
Allowance for uncollectible accounts	(2,824)	(2,950)	(2,577)
Regulatory assets	59,766	52,714	56,804
Derivative instruments	4,433	2,245	1,495
Inventory - Gas	61,318	70,672	68,735
Inventory - Materials and supplies	9,911	9,713	8,714
Gas Reserves	749	0	0
Income taxes receivable	26,285	41,066	0
Other current assets	9,496	19,652	9,823
Total current assets	227,894	330,265	210,265
Non-current assets:
Property, plant and equipment	2,612,147	2,576,402	2,482,826
Less: Accumulated depreciation	744,929	722,239	710,732
Total property, plant and equipment - net	1,867,218	1,854,163	1,772,094
Gas Reserves	15,403	0	0
Regulatory Assets	326,081	348,897	329,197
Derivative instruments	1,042	628	453
Other investments	68,576	69,094	68,393
Other non-current assets	15,780	13,569	15,159
Total non-current assets	2,294,100	2,286,351	2,185,296
Total assets	2,521,994	2,616,616	2,395,561
Capitalization:
Common stock - no par value; authorized 100,000 shares; issued and outstanding 26,673, 26,564 and 26,668 at March 31, 2011 and 2010, and December 31, 2010, respectively	344,451	342,978	339,394
Retained earnings	376,489	356,727	357,173
Accumulated other comprehensive income (loss)	(6,312)	(6,604)	(5,772)
Total common stock equity	714,628	693,101	690,795
Long-term debt	551,700	591,700	591,700
Total capitalization	1,266,328	1,284,801	1,282,495
Current liabilities:
Short-term debt	185,400	257,435	106,875
Current maturities of long-term debt	40,000	10,000	45,000
Accounts payable	54,148	93,243	81,675
Taxes accrued	6,805	10,579	13,008
Interest accrued	5,127	5,182	5,397
Regulatory liabilities	25,784	17,828	29,524
Derivative instruments	25,986	38,437	34,463
Other current liabilities	37,574	35,457	31,900
Total current liabilities	380,824	468,161	347,842
Deferred credits and other non-current liabilities:
Deferred tax liabilities	398,825	373,409	316,152
Regulatory Liabilities	265,703	258,031	251,585
Pension and other postretirement benefit liabilities	130,985	144,250	120,185
Derivative instruments	9,202	17,022	16,917
Other non-current liabilities	70,127	70,942	60,385
Total deferred credits and other non-current liabilities	874,842	863,654	765,224
Commitments and contingencies (see Note 14)	0	0	0
Total capitalization and liabilities	$ 2,521,994	$ 2,616,616	$ 2,395,561