Income Taxes (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended
	Mar. 31, 2014	Mar. 31, 2013	Dec. 31, 2013
Income Taxes
Effective tax rate on income from continuing operations (as a percent)	20.70%	25.00%
Benefits Tax Planning and Completion of Audits	$ 17
Valuation allowance	19		19
Gross unrecognized tax benefit (expense)	195		209
Unrecognized tax benefits (net of federal tax benefits) that would impact the effective tax rate	45		62
Estimated decrease in amount of unrecognized tax benefits in next 12 months	140
Significant Change in Unrecognized Tax Benefits is Reasonably Possible, Estimated Range of Change, Upper Bound	150
Increase (reduction) in interest and penalties	1	1
Accrued interest and penalties	42		42
State and Local
Income Taxes
State net operating losses	$ 29