Other Comprehensive Income (Loss) and Accumulated Other Comprehensive Income (Loss) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2024	Dec. 31, 2023	Dec. 31, 2022
Accumulated other comprehensive income (loss) [Roll Forward]
Balance, beginning of year	$ 24,921	$ 21,560
Other comprehensive income (loss), net of taxes	(496)	1,974	$ (7,638)
Balance, end of year	27,864	24,921	21,560
Pre-tax components of other comprehensive income (loss) and the related income tax expense (benefit)
Other comprehensive income (loss), before income taxes	(575)	2,494	(9,640)
Income tax expense (benefit)	(79)	520	(2,002)
Other comprehensive income (loss), net of taxes	(496)	1,974	(7,638)
Accumulated Other Comprehensive Income (Loss) [Member]
Accumulated other comprehensive income (loss) [Roll Forward]
Balance, beginning of year	(4,471)	(6,445)	1,193
Other comprehensive income (loss) before reclassifications	(596)	1,908	(7,748)
Amounts reclassified from accumulated other comprehensive income (loss), net of tax	100	66	110
Other comprehensive income (loss), net of taxes	(496)	1,974	(7,638)
Balance, end of year	(4,967)	(4,471)	(6,445)
Pre-tax components of other comprehensive income (loss) and the related income tax expense (benefit)
Other comprehensive income (loss), before income taxes	(575)	2,494	(9,640)
Income tax expense (benefit)	(79)	520	(2,002)
Other comprehensive income (loss), net of taxes	(496)	1,974	(7,638)
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	(3,309)	(5,077)	2,233
Other comprehensive income (loss) before reclassifications	(619)	1,692	(7,387)
Amounts reclassified from accumulated other comprehensive income (loss), net of tax	104	76	77
Other comprehensive income (loss), net of taxes	(515)	1,768	(7,310)
Balance, end of year	(3,824)	(3,309)	(5,077)
Pre-tax components of other comprehensive income (loss) and the related income tax expense (benefit)
Other comprehensive income (loss), before income taxes	(644)	2,249	(9,276)
Income tax expense (benefit)	(129)	481	(1,966)
Other comprehensive income (loss), net of taxes	(515)	1,768	(7,310)
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	180	179	182
Other comprehensive income (loss) before reclassifications	4	1	(3)
Amounts reclassified from accumulated other comprehensive income (loss), net of tax	0	0	0
Other comprehensive income (loss), net of taxes	4	1	(3)
Balance, end of year	184	180	179
Pre-tax components of other comprehensive income (loss) and the related income tax expense (benefit)
Other comprehensive income (loss), before income taxes	5	1	(4)
Income tax expense (benefit)	1	0	(1)
Other comprehensive income (loss), net of taxes	4	1	(3)
Net Benefit Plan Assets and Obligations Recognized in Shareholders’ Equity [Member]
Accumulated other comprehensive income (loss) [Roll Forward]
Balance, beginning of year	(458)	(542)	(473)
Other comprehensive income (loss) before reclassifications	238	94	(102)
Amounts reclassified from accumulated other comprehensive income (loss), net of tax	(4)	(10)	33
Other comprehensive income (loss), net of taxes	234	84	(69)
Balance, end of year	(224)	(458)	(542)
Pre-tax components of other comprehensive income (loss) and the related income tax expense (benefit)
Other comprehensive income (loss), before income taxes	296	106	(87)
Income tax expense (benefit)	62	22	(18)
Other comprehensive income (loss), net of taxes	234	84	(69)
Net Unrealized Foreign Currency Translation [Member]
Accumulated other comprehensive income (loss) [Roll Forward]
Balance, beginning of year	(884)	(1,005)	(749)
Other comprehensive income (loss) before reclassifications	(219)	121	(256)
Amounts reclassified from accumulated other comprehensive income (loss), net of tax	0	0	0
Other comprehensive income (loss), net of taxes	(219)	121	(256)
Balance, end of year	(1,103)	(884)	(1,005)
Pre-tax components of other comprehensive income (loss) and the related income tax expense (benefit)
Other comprehensive income (loss), before income taxes	(232)	138	(273)
Income tax expense (benefit)	(13)	17	(17)
Other comprehensive income (loss), net of taxes	$ (219)	$ 121	$ (256)