Treasury Stock (Details) - USD ($)	1 Months Ended				3 Months Ended
	Apr. 30, 2018	Feb. 28, 2018	Jan. 31, 2018	Nov. 30, 2017	Mar. 31, 2018	Mar. 31, 2017
Equity, Class of Treasury Stock [Line Items]
Stock repurchase program, authorized amount					$ 8,500,000,000
Available to repurchase common stock					679,000,000
Accelerated share repurchase program				$ 750,000,000
Amount expended on share repurchases in open market transactions					$ 0
Number of shares withheld to satisfy minimum tax withholding obligations					507,274	691,154
Payment for tax withholding related to vested stock units					$ 46,900,000	$ 57,000,000
Open Market Purchases [Member]
Equity, Class of Treasury Stock [Line Items]
Amount expended on share repurchases in open market transactions						$ 500,000,000
Number of shares repurchased						6,399,499
Average per share price on share repurchases in open market transactions (in dollars per share)						$ 78.13
ASR Counterparty [Member]
Equity, Class of Treasury Stock [Line Items]
Amount expended on share repurchases in open market transactions		$ 750,000,000		$ 750,000,000
Number of shares repurchased		6,500,000.0	1,400,000	7,100,000.0
Shares repurchased as percentage of shares pursuant to accelerated share repurchase agreement (percent)				80.00%
Subsequent Event [Member] | ASR Counterparty [Member]
Equity, Class of Treasury Stock [Line Items]
Number of shares repurchased	1,642,603