Income Taxes - Provision for Income Taxes (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Current:
Federal	$ 1,747	$ 4,455	$ 2,384
State	176	190	179
Foreign	1,031	389	195
Total current tax expense	2,954	5,034	2,758
Deferred:
Federal	316	(296)	(414)
State	34	(33)	(18)
Foreign	(55)	(45)	(25)
Total deferred tax expense/(benefits)	295	(374)	(457)
Provision for income taxes	$ 3,249	$ 4,660	$ 2,301