CONSOLIDATED BALANCE SHEETS (UNAUDITED) (USD $) In Thousands, unless otherwise specified	Mar. 31, 2015	Dec. 31, 2014
Current assets
Cash and cash equivalents	$ 3,093	$ 7,635
Accounts receivable, net	315,467	322,885
Accounts receivable from affiliates	22,948	50,842
Investments in utility money pool arrangement	0	16,000
Accrued unbilled revenues	204,856	294,049
Inventories	195,341	238,979
Regulatory assets	97,865	120,120
Deferred income taxes	109,726	64,587
Derivative instruments	1,912	1,731
Prepaid taxes	0	90,365
Prepayments and other	25,134	23,979
Total current assets	976,342	1,231,172
Property, plant and equipment, net	11,695,876	11,626,956
Other assets
Regulatory assets	905,527	903,973
Derivative instruments	4,748	5,176
Other	48,248	48,506
Total other assets	958,523	957,655
Total assets	13,630,741	13,815,783
Current liabilities
Current portion of long-term debt	8,418	8,178
Short-term Debt	142,000	382,000
Accounts payable	302,446	425,133
Accounts payable to affiliates	33,472	46,736
Regulatory liabilities	185,198	134,459
Taxes accrued	226,087	159,470
Accrued interest	24,238	48,409
Dividends payable to parent	80,650	83,652
Derivative instruments	5,784	5,774
Other	71,783	72,002
Total current liabilities	1,080,076	1,365,813
Deferred credits and other liabilities
Deferred income taxes	2,522,038	2,437,641
Deferred investment tax credits	35,539	36,273
Regulatory liabilities	476,431	464,421
Asset retirement obligations	227,635	225,296
Derivative instruments	16,967	18,257
Customer advances	226,415	229,990
Pension and employee benefit obligations	181,434	202,031
Other	68,238	68,171
Total deferred credits and other liabilities	3,754,697	3,682,080
Commitments and contingencies
Capitalization
Long-term debt	3,880,066	3,882,051
Common stock — 100 shares authorized at $0.01 par value; 100 shares outstanding at March 31, 2015 and Dec. 31, 2014, respectively	0	0
Additional paid in capital	3,522,646	3,522,788
Retained earnings	1,417,244	1,386,929
Accumulated other comprehensive loss	(23,988)	(23,878)
Total common stockholder’s equity	4,915,902	4,885,839
Total liabilities and equity	$ 13,630,741	$ 13,815,783