CONSOLIDATED BALANCE SHEETS (UNAUDITED) (USD $) In Thousands, unless otherwise specified	Mar. 31, 2012	Dec. 31, 2011
Current assets
Cash and cash equivalents	$ 99,742	$ 60,684
Restricted cash	9,055	95,287
Accounts receivable, net	718,145	753,120
Accrued unbilled revenues	491,410	688,740
Inventories	474,359	618,232
Regulatory assets	333,053	402,235
Derivative instruments	61,971	64,340
Deferred income taxes	162,353	178,446
Prepayments and other	192,746	121,480
Total current assets	2,542,834	2,982,564
Property, plant and equipment, net	22,672,686	22,353,367
Other assets
Nuclear decommissioning fund and other investments	1,537,490	1,463,515
Regulatory assets	2,361,648	2,389,008
Derivative instruments	146,438	152,887
Other	192,157	155,926
Total other assets	4,237,733	4,161,336
Total assets	29,453,253	29,497,267
Current liabilities
Current portion of long-term debt	1,309,681	1,059,922
Short-term debt	339,000	219,000
Accounts payable	786,187	902,078
Regulatory liabilities	220,526	275,095
Taxes accrued	359,064	289,713
Accrued interest	161,930	177,111
Dividends payable	126,601	126,487
Derivative instruments	56,132	157,414
Other	348,921	381,819
Total current liabilities	3,708,042	3,588,639
Deferred credits and other liabilities
Deferred income taxes	4,212,924	4,020,377
Deferred investment tax credits	85,819	86,743
Regulatory liabilities	1,107,818	1,101,534
Asset retirement obligations	1,662,175	1,651,793
Derivative instruments	260,152	263,906
Customer advances	247,224	248,345
Pension and employee benefit obligations	813,792	1,001,906
Other	219,273	203,313
Total deferred credits and other liabilities	8,609,177	8,577,917
Commitments and contingencies
Capitalization
Long-term debt	8,598,363	8,848,513
Common stock - 1,000,000,000 shares authorized of $2.50 par value; 486,935,997 and 486,493,933 shares outstanding at March 31, 2012 and Dec. 31, 2011, respectively	1,217,339	1,216,234
Additional paid in capital	5,298,572	5,327,443
Retained earnings	2,089,275	2,032,556
Accumulated other comprehensive loss	(67,515)	(94,035)
Total common stockholders' equity	8,537,671	8,482,198
Total liabilities and equity	$ 29,453,253	$ 29,497,267