Income Taxes (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2017	Mar. 31, 2016	Dec. 31, 2016
Operating Loss Carryforwards [Line Items]
Effective tax rate on income from continuing operations (as a percent)	15.20%	23.30%
Quantifying misstatement in current year financial statements amount	$ (20)
Excess Tax Benefit from Share-based Compensation, Operating Activities	28
Valuation allowance	12		$ 11
Gross unrecognized tax benefit (expense)	126		115
Unrecognized tax benefits (net of federal tax benefits) that would impact the effective tax rate	50		46
Increase (reduction) in interest and penalties	(1)	$ 44
Accrued interest and penalties	9		$ 8
Minimum [Member]
Operating Loss Carryforwards [Line Items]
Decrease in gross unrecognized tax benefits due to resolution of IRS examination	20
Maximum [Member]
Operating Loss Carryforwards [Line Items]
Decrease in gross unrecognized tax benefits due to resolution of IRS examination	30
State and Local [Member]
Operating Loss Carryforwards [Line Items]
State net operating losses	$ 14