Tax Matters - Provision for Taxes on Income (Details) - USD ($) $ in Millions		12 Months Ended
		Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Current income taxes:
Federal		$ 371	$ (1,886)	$ 388
State and local		58	(187)	(49)
Deferred income taxes:
Federal		(1,061)	1,193	(1,641)
State and local		(115)	266	15
Total U.S. tax benefit		(747)	(613)	(1,287)
TCJA
Current income taxes	[1]	0	(135)	(3,035)
Deferred Income taxes	[1]	0	(187)	2,439
Total TCJA tax benefit	[1]	0	(323)	(596)
International
Current income taxes		1,517	2,418	2,195
Deferred income taxes		(292)	(863)	(579)
Total international tax provision		1,224	1,555	1,617
Provision/(benefit) for taxes on income		$ 477	$ 618	$ (266)

[1] The 2018 current tax benefit and deferred tax expense primarily relate to the utilization of tax credit carryforwards against the repatriation tax liability associated with the enactment of the TCJA. See discussion below.