Income Taxes (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2016	Sep. 30, 2015	Sep. 30, 2016	Sep. 30, 2015	Dec. 31, 2015
Operating Loss Carryforwards [Line Items]
Effective tax rate on income from continuing operations (as a percent)	9.70%	24.10%	18.60%	23.00%
Valuation allowance	$ 11		$ 11		$ 11
Gross unrecognized tax benefit (expense)	115		115		161
Unrecognized tax benefits (net of federal tax benefits) that would impact the effective tax rate	47		47		57
Increase (reduction) in interest and penalties	0	$ 1	44	$ 3
Accrued interest and penalties	7		7		$ 51
Minimum [Member]
Operating Loss Carryforwards [Line Items]
Decrease in gross unrecognized tax benefits due to resolution of IRS examination	65		65
Maximum [Member]
Operating Loss Carryforwards [Line Items]
Decrease in gross unrecognized tax benefits due to resolution of IRS examination	75		75
State and Local [Member]
Operating Loss Carryforwards [Line Items]
State net operating losses	$ 14		$ 14