Income Taxes (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2012	Jun. 30, 2011	Jun. 30, 2012	Jun. 30, 2011	Dec. 31, 2011
Income Taxes
Effective tax rate on income from continuing operations (as a percent)	42.80%	29.00%	32.40%	26.50%
Decrease to net income resulting from out-of-period correction for tax-related item	$ 32		$ 32
Maximum period for recognizing capital losses			5 years
Valuation allowance	5		5		5
Capital loss carryforwards	35		35
State net operating losses	39		39
Gross unrecognized tax benefit (expense)	103		103		184
Unrecognized tax benefits (net of federal tax benefits) that would impact the effective tax rate	34		34		38
Interest and penalties recognized	1	49	(4)	65
Estimated decrease in amount of unrecognized tax benefits in next 12 months	78		78
Accrued interest and penalties	$ 33		$ 33		$ 37