Other Comprehensive Income (Loss) and Accumulated Other Comprehensive Income (Loss) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Accumulated other comprehensive income (loss) [Roll Forward]
Balance, beginning of year	$ 21,560	$ 28,887
Other comprehensive income (loss), net of taxes	1,974	(7,638)	$ (1,309)
Balance, end of year	24,921	21,560	28,887
Pre-tax components of other comprehensive income (loss) and the related income tax expense (benefit)
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)
Accumulated Other Comprehensive Income (Loss) [Member]
Accumulated other comprehensive income (loss) [Roll Forward]
Balance, beginning of year	(6,445)	1,193	2,502
Other comprehensive income (loss) before reclassifications	1,908	(7,748)	(1,337)
Amounts reclassified from accumulated other comprehensive income (loss), net of tax	66	110	28
Other comprehensive income (loss), net of taxes	1,974	(7,638)	(1,309)
Balance, end of year	(4,471)	(6,445)	1,193
Pre-tax components of other comprehensive income (loss) and the related income tax expense (benefit)
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)
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 year	(5,077)	2,233	3,892
Other comprehensive income (loss) before reclassifications	1,692	(7,387)	(1,606)
Amounts reclassified from accumulated other comprehensive income (loss), net of tax	76	77	(53)
Other comprehensive income (loss), net of taxes	1,768	(7,310)	(1,659)
Balance, end of year	(3,309)	(5,077)	2,233
Pre-tax components of other comprehensive income (loss) and the related income tax expense (benefit)
Other comprehensive income (loss), before income taxes	2,249	(9,276)	(2,115)
Income tax expense (benefit)	481	(1,966)	(456)
Other comprehensive income (loss), net of taxes	1,768	(7,310)	(1,659)
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 year	179	182	182
Other comprehensive income (loss) before reclassifications	1	(3)	0
Amounts reclassified from accumulated other comprehensive income (loss), net of tax	0	0	0
Other comprehensive income (loss), net of taxes	1	(3)	0
Balance, end of year	180	179	182
Pre-tax components of other comprehensive income (loss) and the related income tax expense (benefit)
Other comprehensive income (loss), before income taxes	1	(4)	0
Income tax expense (benefit)	0	(1)	0
Other comprehensive income (loss), net of taxes	1	(3)	0
Net Benefit Plan Assets and Obligations Recognized in Shareholders’ Equity [Member]
Accumulated other comprehensive income (loss) [Roll Forward]
Balance, beginning of year	(542)	(473)	(832)
Other comprehensive income (loss) before reclassifications	94	(102)	278
Amounts reclassified from accumulated other comprehensive income (loss), net of tax	(10)	33	81
Other comprehensive income (loss), net of taxes	84	(69)	359
Balance, end of year	(458)	(542)	(473)
Pre-tax components of other comprehensive income (loss) and the related income tax expense (benefit)
Other comprehensive income (loss), before income taxes	106	(87)	455
Income tax expense (benefit)	22	(18)	96
Other comprehensive income (loss), net of taxes	84	(69)	359
Net Unrealized Foreign Currency Translation [Member]
Accumulated other comprehensive income (loss) [Roll Forward]
Balance, beginning of year	(1,005)	(749)	(740)
Other comprehensive income (loss) before reclassifications	121	(256)	(9)
Amounts reclassified from accumulated other comprehensive income (loss), net of tax	0	0	0
Other comprehensive income (loss), net of taxes	121	(256)	(9)
Balance, end of year	(884)	(1,005)	(749)
Pre-tax components of other comprehensive income (loss) and the related income tax expense (benefit)
Other comprehensive income (loss), before income taxes	138	(273)	(11)
Income tax expense (benefit)	17	(17)	(2)
Other comprehensive income (loss), net of taxes	$ 121	$ (256)	$ (9)