Consolidated Balance Sheets (USD $) In Thousands, unless otherwise specified	Dec. 31, 2011	Dec. 31, 2010
Utility plant:
Land	$ 37,703	$ 21,355
Depreciable plant and equipment	1,807,569	1,695,075
Construction work in progress	98,623	103,214
Intangible assets	16,486	24,122
Total utility plant	1,960,381	1,843,766
Less accumulated depreciation and amortization	(579,262)	(549,469)
Net utility plant	1,381,119	1,294,297
Current assets:
Cash and cash equivalents	27,203	42,277
Receivables: net of allowance for doubtful accounts of $669 and $804, respectively
Customers	28,418	25,813
Regulatory balancing accounts	21,680	14,784
Other	6,422	5,386
Unbilled revenue	15,068	13,925
Materials and supplies at weighted average cost	5,913	6,058
Prepaid income taxes		10,168
Taxes, prepaid expenses, and other assets	9,184	7,799
Total current assets	113,888	126,210
Other assets:
Regulatory assets	319,898	229,577
Unamortized debt premium and expense	6,071	6,489
Goodwill	2,615	2,615
Other	30,996	32,878
Total other assets	359,580	271,559
Total assets	1,854,587	1,692,066
Capitalization:
Common stock, $0.01 par value; 68,000 shares authorized, 41,817 and 41,667, outstanding in 2011 and 2010, respectively	418	416
Additional paid-in capital	219,572	217,309
Retained earnings	229,839	217,801
Total common stockholders' equity	449,829	435,526
Long-term debt, less current maturities	481,632	479,181
Total capitalization	931,461	914,707
Current liabilities:
Current maturities of long-term debt	6,533	2,380
Short-term borrowings	47,140	23,750
Accounts payable	48,923	39,505
Regulatory balancing accounts	2,655	3,025
Accrued other taxes	3,942	3,079
Accrued interest	4,756	4,651
Other accrued liabilities	37,926	30,958
Total current liabilities	151,875	107,348
Unamortized investment tax credits	2,254	2,244
Deferred income taxes	116,368	107,084
Regulatory liabilities	28,037	17,079
Pension and postretirement benefits other than pension	232,110	155,224
Advances for construction	187,278	186,899
Contributions in aid of construction	154,191	136,356
Other long-term liabilities	51,013	65,125
Commitments and contingencies
Total capitalization and liabilities	$ 1,854,587	$ 1,692,066