Common Stock (Details) - USD ($) $ in Millions	3 Months Ended						9 Months Ended
	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Sep. 30, 2019	Sep. 30, 2018
Class of Stock [Line Items]
Treasury stock acquired (shares)	7,016,929			3,067,834			12,343,135	10,574,233
Value of treasury stock shares repurchased/withheld	$ 2,767	$ 861	$ 940	$ 933	$ 1,664	$ 617	$ 4,568	$ 3,214
Remaining authorized repurchase amount	$ 1,400						$ 1,400
Share buybacks
Class of Stock [Line Items]
Treasury stock acquired (shares)	6,894,762			3,046,346			11,757,758	10,349,639
Value of treasury stock shares repurchased/withheld	$ 2,748			$ 929			$ 4,455	$ 3,142
Income tax withholding
Class of Stock [Line Items]
Treasury stock acquired (shares)	46,691			12,703			324,731	209,394
Value of treasury stock shares repurchased/withheld	$ 19			$ 4			$ 113	$ 72
Exercise cost
Class of Stock [Line Items]
Treasury stock acquired (shares)	75,476			8,785			260,646	15,200