Stock Repurchase Programs (Details) - USD ($)	1 Months Ended	3 Months Ended		6 Months Ended
	Mar. 31, 2018	Jun. 30, 2018	Mar. 31, 2018	Jun. 30, 2018	Jun. 30, 2017	Dec. 31, 2017	Apr. 30, 2017
Equity, Class of Treasury Stock [Line Items]
Repurchases of shares of common stock, Shares Repurchased (in shares)				29,700,000
Repurchases of shares of common stock, Cash Paid for Shares Repurchased				$ 2,325,000,000	$ 606,000,000
Remaining Amount Authorized		$ 2,674,000,000		$ 2,674,000,000		$ 4,999,000,000
Treasury stock, retired (in shares)				0
Stock Repurchase Program
Equity, Class of Treasury Stock [Line Items]
Stock repurchase program, maximum authorized amount							$ 5,000,000,000
Repurchases of shares of common stock, Shares Repurchased (in shares)			10,800,000
Repurchases of shares of common stock, Average Price per Share (in usd per share)			$ 76.82
Repurchases of shares of common stock, Cash Paid for Shares Repurchased			$ 825,000,000
Remaining Amount Authorized	$ 4,174,000,000		$ 4,174,000,000
Accelerated Share Repurchase Agreement
Equity, Class of Treasury Stock [Line Items]
Repurchases of shares of common stock, Shares Repurchased (in shares)	12,800,000	6,100,000	12,800,000
Repurchases of shares of common stock, Average Price per Share (in usd per share)		$ 81.33	$ 78.03
Repurchases of shares of common stock, Cash Paid for Shares Repurchased	$ 1,000,000,000	$ 500,000,000	$ 1,000,000,000
Remaining Amount Authorized	$ 3,174,000,000	$ 2,674,000,000	$ 3,174,000,000	$ 2,674,000,000
Treasury stock recorded for repurchases				$ 985,000,000