Income Taxes (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2015	Jun. 30, 2014	Jun. 30, 2015	Jun. 30, 2014	Dec. 31, 2014
Income Taxes
Effective tax rate on income from continuing operations (as a percent)	22.60%	24.50%	22.60%	22.50%
Valuation allowance	$ 12		$ 12		$ 20
Gross unrecognized tax benefit (expense)	224		224		242
Unrecognized tax benefits (net of federal tax benefits) that would impact the effective tax rate	45		45		57
Significant change in unrecognized tax benefits is reasonably possible, estimated range of change, lower bound	170		170
Significant change in unrecognized tax benefits is reasonably possible, estimated range of change, upper bound	180		180
Increase (reduction) in interest and penalties	1	$ 4	2	$ 3
Accrued interest and penalties	50		50		$ 48
State and Local [Member]
Income Taxes
State net operating losses	17		17
State AMT credit carryforward	$ 1		$ 1