Consolidated Statement of Comprehensive Income (Loss) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Statement of Comprehensive Income [Abstract]
Net income	$ 2,991	$ 2,842	$ 3,662
Other comprehensive income (loss):
Changes in net unrealized gains (losses) on investment securities having no credit losses recognized in the consolidated statement of income	2,249	(9,276)	(2,115)
Changes in net unrealized gains (losses) on investment securities having credit losses recognized in the consolidated statement of income	1	(4)	0
Net changes in benefit plan assets and obligations	106	(87)	455
Net changes in unrealized foreign currency translation	138	(273)	(11)
Other comprehensive income (loss) before income taxes	2,494	(9,640)	(1,671)
Income tax expense (benefit)	520	(2,002)	(362)
Other comprehensive income (loss), net of taxes	1,974	(7,638)	(1,309)
Comprehensive income (loss)	$ 4,965	$ (4,796)	$ 2,353