Consolidated Statement of Comprehensive Income (Unaudited) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Statement of Comprehensive Income [Abstract]
Net income	$ 827	$ 396	$ 1,387	$ 1,749
Other comprehensive income:
Changes in net unrealized gains on investment securities having no credit losses recognized in the consolidated statement of income	217	605	2,001	3,129
Changes in net unrealized gains on investment securities having credit losses recognized in the consolidated statement of income	(7)	(3)	(10)	(2)
Net changes in benefit plan assets and obligations	20	14	64	40
Net changes in unrealized foreign currency translation	79	(75)	(137)	(20)
Other comprehensive income before income taxes	309	541	1,918	3,147
Income tax expense	53	122	420	663
Other comprehensive income, net of taxes	256	419	1,498	2,484
Comprehensive income	$ 1,083	$ 815	$ 2,885	$ 4,233