Income Taxes - Income Tax Reconciliation (Details) - USD ($) $ in Millions	3 Months Ended		12 Months Ended
	Dec. 31, 2018	Mar. 31, 2017	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Income Tax Disclosure [Abstract]
Federal statutory rate			21.00%	21.00%	35.00%
Provision at statutory rate			$ 463	$ 571	$ 797
Foreign income taxed at different rates			31	(16)	(217)
Other taxes on foreign operations			(155)	26	330
Stock-based compensation			3	(3)	(33)
State taxes, net of federal benefit			(20)	13	(13)
Research and other tax credits			(33)	(30)	(35)
Tax basis step-up resulting from realignment		$ 695	199	(9)	(695)
Impact of tax rate change			(19)	108	0
U.S. tax reform			0	(463)	3,142
Effective settlement of audits			(71)	0	0
Other			17	(7)	12
Income tax expense (benefit)	$ (445)		$ 415	$ 190	$ 3,288