Stock Compensation - Effects on Cash Flows (Details) - USD ($) $ in Millions		12 Months Ended
		Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Share-based Payment Arrangement [Abstract]
Proceeds from common stock transactions	[1]	$ 539	$ 373	$ 483
Tax benefit realized from stock compensation		224	179	341
Reduction to deferred tax asset		(49)	(43)	(91)
Excess tax benefit for stock compensation		$ 175	$ 136	$ 250

[1] Net of taxes paid for employee shares withheld of $52 million, $60 million and $83 million in 2019, 2018 and 2017, respectively.