Summary of Significant Accounting Policies (Details) - Updated Guidance - USD ($) $ in Millions	Dec. 31, 2019	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2018
New Accounting Pronouncements
Accounting Standards Update [Extensible List]	Accounting Standards Update 2016-13 [Member]
Decrease in shareholders' equity	$ (25,943)	$ (28,887)	$ (29,201)
Retained earnings [Member]
New Accounting Pronouncements
Decrease in shareholders' equity	(36,977)	$ (41,555)	$ (38,771)	$ (35,204)
Cumulative Effect, Period of Adoption, Adjustment [Member] | Retained earnings [Member]
New Accounting Pronouncements
Decrease in shareholders' equity	$ 43