Other Comprehensive Income (Loss) and Accumulated Other Comprehensive Income (Loss) (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2024	Mar. 31, 2023
Accumulated other comprehensive income (loss) [Roll Forward]
Balance, beginning of period	$ 24,921
Other comprehensive income (loss), net of taxes	(660)	$ 1,059
Balance, end of period	25,022	23,052
Pre-tax components of other comprehensive income (loss) and the related income tax expense (benefit)
Other comprehensive income (loss), before income taxes	(822)	1,342
Income tax expense (benefit)	(162)	283
Other comprehensive income (loss), net of taxes	(660)	1,059
Accumulated Other Comprehensive Income (Loss) [Member]
Accumulated other comprehensive income (loss) [Roll Forward]
Balance, beginning of period	(4,471)	(6,445)
Other comprehensive income (loss) before reclassifications	(691)
Amounts reclassified from accumulated other comprehensive income (loss), net of tax	31
Other comprehensive income (loss), net of taxes	(660)	1,059
Balance, end of period	(5,131)	(5,386)
Pre-tax components of other comprehensive income (loss) and the related income tax expense (benefit)
Other comprehensive income (loss), before income taxes	(822)	1,342
Income tax expense (benefit)	(162)	283
Other comprehensive income (loss), net of taxes	(660)	1,059
Changes in Net Unrealized Gains (Losses) on Investment Securities Having No Credit Losses Recognized in the Consolidated Statement of Income [Member]
Accumulated other comprehensive income (loss) [Roll Forward]
Balance, beginning of period	(3,309)
Other comprehensive income (loss) before reclassifications	(626)
Amounts reclassified from accumulated other comprehensive income (loss), net of tax	32
Other comprehensive income (loss), net of taxes	(594)	1,030
Balance, end of period	(3,903)
Pre-tax components of other comprehensive income (loss) and the related income tax expense (benefit)
Other comprehensive income (loss), before income taxes	(752)	1,308
Income tax expense (benefit)	(158)	278
Other comprehensive income (loss), net of taxes	(594)	1,030
Changes in Net Unrealized Gains (Losses) on Investment Securities Having Credit Losses Recognized in the Consolidated Statement of Income [Member]
Accumulated other comprehensive income (loss) [Roll Forward]
Balance, beginning of period	180
Other comprehensive income (loss) before reclassifications	2
Amounts reclassified from accumulated other comprehensive income (loss), net of tax	0
Other comprehensive income (loss), net of taxes	2	0
Balance, end of period	182
Pre-tax components of other comprehensive income (loss) and the related income tax expense (benefit)
Other comprehensive income (loss), before income taxes	2	0
Income tax expense (benefit)	0	0
Other comprehensive income (loss), net of taxes	2	0
Net Benefit Plan Assets and Obligations Recognized in Shareholders' Equity [Member]
Accumulated other comprehensive income (loss) [Roll Forward]
Balance, beginning of period	(458)
Other comprehensive income (loss) before reclassifications	0
Amounts reclassified from accumulated other comprehensive income (loss), net of tax	(1)
Other comprehensive income (loss), net of taxes	(1)	(2)
Balance, end of period	(459)
Pre-tax components of other comprehensive income (loss) and the related income tax expense (benefit)
Other comprehensive income (loss), before income taxes	(1)	(3)
Income tax expense (benefit)	0	(1)
Other comprehensive income (loss), net of taxes	(1)	(2)
Net Unrealized Foreign Currency Translation [Member]
Accumulated other comprehensive income (loss) [Roll Forward]
Balance, beginning of period	(884)
Other comprehensive income (loss) before reclassifications	(67)
Amounts reclassified from accumulated other comprehensive income (loss), net of tax	0
Other comprehensive income (loss), net of taxes	(67)	31
Balance, end of period	(951)
Pre-tax components of other comprehensive income (loss) and the related income tax expense (benefit)
Other comprehensive income (loss), before income taxes	(71)	37
Income tax expense (benefit)	(4)	6
Other comprehensive income (loss), net of taxes	$ (67)	$ 31