Consolidated Balance Sheets (USD $) In Thousands, unless otherwise specified	Dec. 31, 2013	Dec. 31, 2012
Utility plant:
Land	$ 42,208	$ 42,023
Depreciable plant and equipment	2,043,414	1,903,365
Construction work in progress	109,474	132,362
Intangible assets	18,232	18,613
Total utility plant	2,213,328	2,096,363
Less accumulated depreciation and amortization	(697,497)	(639,307)
Net utility plant	1,515,831	1,457,056
Current assets:
Cash and cash equivalents	27,506	38,790
Receivables: net of allowance for doubtful accounts of $668 and $714 in 2013 and 2012, respectively
Customers	31,468	29,958
Regulatory balancing accounts	30,887	34,020
Other	18,700	11,943
Unbilled revenue	17,034	15,394
Materials and supplies at weighted average cost	5,571	5,874
Taxes, prepaid expenses, and other assets	8,324	10,585
Total current assets	139,490	146,564
Other assets:
Regulatory assets	251,681	344,419
Unamortized debt premium and expense	5,114	5,591
Goodwill	2,615	2,615
Other	45,124	39,679
Total other assets	304,534	392,304
Total assets	1,959,855	1,995,924
Capitalization:
Common stock, $0.01 par value; 68,000 shares authorized, 47,741 and 41,908, outstanding in 2013 and 2012, respectively	477	419
Additional paid-in capital	328,364	221,013
Retained earnings	269,915	252,280
Total common stockholders' equity	598,756	473,712
Long-term debt, less current maturities	426,142	434,467
Total capitalization	1,024,898	908,179
Current liabilities:
Current maturities of long-term debt	7,908	46,783
Short-term borrowings	46,815	89,475
Accounts payable	55,087	47,199
Regulatory balancing accounts	1,827	5,018
Accrued other taxes	3,575	3,379
Accrued interest	4,245	4,705
Other accrued liabilities	47,127	46,508
Total current liabilities	166,584	243,067
Unamortized investment tax credits	2,106	2,180
Deferred income taxes	183,245	158,846
Regulatory liabilities	34,251	35,720
Pension and postretirement benefits other than pension	145,451	244,901
Advances for construction	183,393	187,584
Contributions in aid of construction	167,723	158,574
Other long-term liabilities	52,204	56,873
Commitments and contingencies
Total capitalization and liabilities	$ 1,959,855	$ 1,995,924