Other Comprehensive Income (Loss) and Accumulated Other Comprehensive Income (Loss) (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2023	Jun. 30, 2022	Jun. 30, 2023	Jun. 30, 2022
Accumulated other comprehensive income (loss) [Roll Forward]
Balance, beginning of period			$ 21,560
Other comprehensive income (loss), net of taxes	$ (623)	$ (2,553)	436	$ (6,348)
Balance, end of period	21,855	22,874	21,855	22,874
Pre-tax components of other comprehensive income (loss) and the related income tax expense (benefit)
Other comprehensive income (loss), before taxes	(813)	(3,210)	529	(8,027)
Income tax expense (benefit)	(190)	(657)	93	(1,679)
Other comprehensive income (loss), net of taxes	(623)	(2,553)	436	(6,348)
Accumulated Other Comprehensive Income (Loss) [Member]
Accumulated other comprehensive income (loss) [Roll Forward]
Balance, beginning of period	(5,386)	(2,602)	(6,445)	1,193
Other comprehensive income (loss) before reclassifications	(638)		415
Amounts reclassified from accumulated other comprehensive income (loss), net of tax	15		21
Other comprehensive income (loss), net of taxes	(623)	(2,553)	436	(6,348)
Balance, end of period	(6,009)	(5,155)	(6,009)	(5,155)
Pre-tax components of other comprehensive income (loss) and the related income tax expense (benefit)
Other comprehensive income (loss), before taxes	(813)	(3,210)	529	(8,027)
Income tax expense (benefit)	(190)	(657)	93	(1,679)
Other comprehensive income (loss), net of taxes	(623)	(2,553)	436	(6,348)
Changes in Net Unrealized Gains (Losses) on Investment Securities Having No Credit Losses Recognized in the Consolidated Statement of Income (Loss) [Member]
Accumulated other comprehensive income (loss) [Roll Forward]
Balance, beginning of period	(4,047)		(5,077)
Other comprehensive income (loss) before reclassifications	(725)		296
Amounts reclassified from accumulated other comprehensive income (loss), net of tax	17		26
Other comprehensive income (loss), net of taxes	(708)	(2,399)	322	(6,204)
Balance, end of period	(4,755)		(4,755)
Pre-tax components of other comprehensive income (loss) and the related income tax expense (benefit)
Other comprehensive income (loss), before taxes	(903)	(3,045)	405	(7,874)
Income tax expense (benefit)	(195)	(646)	83	(1,670)
Other comprehensive income (loss), net of taxes	(708)	(2,399)	322	(6,204)
Changes in Net Unrealized Gains (Losses) on Investment Securities Having Credit Losses Recognized in the Consolidated Statement of Income (Loss) [Member]
Accumulated other comprehensive income (loss) [Roll Forward]
Balance, beginning of period	179		179
Other comprehensive income (loss) before reclassifications	0		0
Amounts reclassified from accumulated other comprehensive income (loss), net of tax	0		0
Other comprehensive income (loss), net of taxes	0	(2)	0	(3)
Balance, end of period	179		179
Pre-tax components of other comprehensive income (loss) and the related income tax expense (benefit)
Other comprehensive income (loss), before taxes	0	(2)	0	(3)
Income tax expense (benefit)	0	0	0	0
Other comprehensive income (loss), net of taxes	0	(2)	0	(3)
Net Benefit Plan Assets and Obligations Recognized in Shareholders' Equity [Member]
Accumulated other comprehensive income (loss) [Roll Forward]
Balance, beginning of period	(544)		(542)
Other comprehensive income (loss) before reclassifications	(2)		(1)
Amounts reclassified from accumulated other comprehensive income (loss), net of tax	(2)		(5)
Other comprehensive income (loss), net of taxes	(4)	9	(6)	18
Balance, end of period	(548)		(548)
Pre-tax components of other comprehensive income (loss) and the related income tax expense (benefit)
Other comprehensive income (loss), before taxes	(4)	11	(7)	22
Income tax expense (benefit)	0	2	(1)	4
Other comprehensive income (loss), net of taxes	(4)	9	(6)	18
Net Unrealized Foreign Currency Translation [Member]
Accumulated other comprehensive income (loss) [Roll Forward]
Balance, beginning of period	(974)		(1,005)
Other comprehensive income (loss) before reclassifications	89		120
Amounts reclassified from accumulated other comprehensive income (loss), net of tax	0		0
Other comprehensive income (loss), net of taxes	89	(161)	120	(159)
Balance, end of period	(885)		(885)
Pre-tax components of other comprehensive income (loss) and the related income tax expense (benefit)
Other comprehensive income (loss), before taxes	94	(174)	131	(172)
Income tax expense (benefit)	5	(13)	11	(13)
Other comprehensive income (loss), net of taxes	$ 89	$ (161)	$ 120	$ (159)