CONSOLIDATED BALANCE SHEETS - USD ($) $ in Thousands		Dec. 31, 2015	Dec. 31, 2014
Current assets
Cash and cash equivalents		$ 84,940	$ 79,608
Accounts receivable, net		724,606	826,506
Accrued unbilled revenues		654,867	728,492
Inventories		608,584	597,183
Regulatory assets		344,630	444,058
Derivative instruments		33,842	85,723
Deferred income taxes		140,219	246,210
Prepaid Taxes		163,023	185,488
Prepayments and other		155,734	171,112
Total current assets		2,910,445	3,364,380
Property, plant and equipment, net		31,205,851	28,756,916
Other assets
Nuclear decommissioning fund and other investments		1,902,995	1,832,640
Regulatory assets		2,858,741	2,774,216
Derivative instruments		51,083	53,775
Other		124,420	175,957
Total other assets		4,937,239	4,836,588
Total assets		39,053,535	36,957,884
Current liabilities
Current portion of long-term debt		657,021	257,726
Short-term debt		846,000	1,019,500
Accounts payable		960,982	1,173,006
Regulatory liabilities	[1]	306,830	410,729
Taxes accrued		438,189	396,615
Accrued interest		166,829	158,536
Dividends payable		162,410	151,720
Derivative instruments		29,839	21,632
Other		490,197	475,119
Total current liabilities		4,058,297	4,064,583
Deferred credits and other liabilities
Deferred income taxes		6,293,661	5,852,988
Deferred investment tax credits		68,419	73,696
Regulatory liabilities		1,332,889	1,163,429
Asset retirement obligations		2,608,562	2,446,631
Derivative instruments		168,311	183,936
Customer advances		228,999	256,945
Pension and employee benefit obligations		941,002	936,907
Other		261,756	264,653
Total deferred credits and other liabilities		$ 11,903,599	$ 11,179,185
Commitments and contingencies
Capitalization
Long-term debt		$ 12,490,719	$ 11,499,634
Common stock — 1,000,000,000 shares authorized of $2.50 par value; 507,535,523 and 505,733,267 shares outstanding at Dec. 31, 2015 and 2014, respectively		1,268,839	1,264,333
Additional paid in capital		5,889,106	5,837,330
Retained earnings		3,552,728	3,220,958
Accumulated other comprehensive loss		(109,753)	(108,139)
Total common stockholders’ equity		10,600,920	10,214,482
Total liabilities and equity		$ 39,053,535	$ 36,957,884

[1] Revenue subject to refund of $75.0 million and $128.3 million for 2015 and 2014, respectively, is included in other current liabilities.