Income Taxes Components of Income Tax Expense (Benefit) (Details) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Income Tax Disclosure [Abstract]
Current federal	$ 54	$ (112)	$ (151)
Current state	13	(3)	(10)
Total current income tax expense (benefit)	67	(115)	(161)
Deferred federal	204	283	338
Deferred state	29	33	40
Total deferred income tax expense	233	316	378
Investment tax credits	(3)	(4)	(4)
Total income tax expense	$ 297	$ 197	$ 213