Accounting Policies - Recently Adopted Accounting Pronouncements (Details) - USD ($) $ in Millions	Jun. 30, 2021	Mar. 31, 2021	Dec. 31, 2020	Jun. 30, 2020	Mar. 31, 2020	Dec. 31, 2019
Accounting Policies [Abstract]
Cumulative effect of new accounting principle in period of adoption, net of tax	$ 10,519		$ 10,098	$ 10,123
RETAINED EARNINGS
Accounting Policies [Abstract]
Cumulative effect of new accounting principle in period of adoption, net of tax	$ 469	$ 230	$ 48	$ 73	$ 68	$ 67
Cumulative Effect Of New Accounting Principle In Period Of Adoption, Tax						(1)
Cumulative Effect, Period of Adoption, Adjustment | RETAINED EARNINGS
Accounting Policies [Abstract]
Cumulative effect of new accounting principle in period of adoption, net of tax						$ 3