CONSOLIDATED BALANCE SHEETS (UNAUDITED) (USD $) In Thousands, unless otherwise specified	Mar. 31, 2015	Dec. 31, 2014
Current assets
Cash and cash equivalents	$ 990	$ 1,285
Accounts receivable, net	65,892	60,396
Accrued unbilled revenues	43,139	53,567
Inventories	14,855	24,685
Regulatory assets	12,800	20,036
Prepaid taxes	18,247	28,628
Deferred income taxes	16,472	8,201
Prepayments and other	5,912	6,918
Total current assets	178,307	203,716
Property, plant and equipment, net	1,715,967	1,674,281
Other assets
Regulatory assets	285,328	280,693
Other investments	3,908	3,818
Other	4,649	4,612
Total other assets	293,885	289,123
Total assets	2,188,159	2,167,120
Current liabilities
Current portion of long-term debt	1,224	1,235
Short-term debt	80,000	78,000
Notes payable to affiliates	500	500
Accounts payable	33,602	61,530
Accounts payable to affiliates	21,883	26,524
Dividends payable to parent	13,315	14,957
Regulatory liabilities	14,145	16,940
Environmental liabilities	26,125	29,116
Other	20,734	19,923
Total current liabilities	211,528	248,725
Deferred credits and other liabilities
Deferred income taxes	365,798	348,180
Deferred investment tax credits	8,956	9,089
Regulatory liabilities	135,800	132,674
Environmental liabilities	86,435	78,620
Customer advances	18,449	17,623
Pension and employee benefit obligations	46,352	51,313
Other	15,872	16,151
Total deferred credits and other liabilities	677,662	653,650
Commitments and contingencies
Capitalization
Long-term debt	567,099	567,056
Common stock — 1,000,000 shares authorized of $100 par value; 933,000 shares outstanding at March 31, 2015 and Dec. 31, 2014, respectively	93,300	93,300
Additional paid in capital	347,486	322,276
Retained earnings	291,350	282,398
Accumulated other comprehensive loss	(266)	(285)
Total common stockholder’s equity	731,870	697,689
Total liabilities and equity	$ 2,188,159	$ 2,167,120