Other Comprehensive Income (Loss) and Accumulated Other Comprehensive Income (Loss) (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2023	Sep. 30, 2022	Sep. 30, 2023	Sep. 30, 2022
Accumulated other comprehensive income (loss) [Roll Forward]
Balance, beginning of period			$ 21,560
Other comprehensive loss, net of taxes	$ (2,003)	$ (2,753)	(1,567)	$ (9,101)
Balance, end of period	19,978	19,906	19,978	19,906
Pre-tax components of other comprehensive income (loss) and the related income tax expense (benefit)
Other comprehensive income (loss), before taxes	(2,512)	(3,443)	(1,983)	(11,470)
Income tax expense (benefit)	(509)	(690)	(416)	(2,369)
Other comprehensive loss, net of taxes	(2,003)	(2,753)	(1,567)	(9,101)
Accumulated Other Comprehensive Income (Loss) [Member]
Accumulated other comprehensive income (loss) [Roll Forward]
Balance, beginning of period	(6,009)	(5,155)	(6,445)	1,193
Other comprehensive income (loss) before reclassifications	(2,028)		(1,613)
Amounts reclassified from accumulated other comprehensive income (loss), net of tax	25		46
Other comprehensive loss, net of taxes	(2,003)	(2,753)	(1,567)	(9,101)
Balance, end of period	(8,012)	(7,908)	(8,012)	(7,908)
Pre-tax components of other comprehensive income (loss) and the related income tax expense (benefit)
Other comprehensive income (loss), before taxes	(2,512)	(3,443)	(1,983)	(11,470)
Income tax expense (benefit)	(509)	(690)	(416)	(2,369)
Other comprehensive loss, net of taxes	(2,003)	(2,753)	(1,567)	(9,101)
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	(4,755)		(5,077)
Other comprehensive income (loss) before reclassifications	(1,918)		(1,622)
Amounts reclassified from accumulated other comprehensive income (loss), net of tax	28		54
Other comprehensive loss, net of taxes	(1,890)	(2,526)	(1,568)	(8,730)
Balance, end of period	(6,645)		(6,645)
Pre-tax components of other comprehensive income (loss) and the related income tax expense (benefit)
Other comprehensive income (loss), before taxes	(2,391)	(3,204)	(1,986)	(11,078)
Income tax expense (benefit)	(501)	(678)	(418)	(2,348)
Other comprehensive loss, net of taxes	(1,890)	(2,526)	(1,568)	(8,730)
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	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 loss, net of taxes	0	1	0	(2)
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	0	0	(3)
Income tax expense (benefit)	0	(1)	0	(1)
Other comprehensive loss, net of taxes	0	1	0	(2)
Net Benefit Plan Assets and Obligations Recognized in Shareholders' Equity [Member]
Accumulated other comprehensive income (loss) [Roll Forward]
Balance, beginning of period	(548)		(542)
Other comprehensive income (loss) before reclassifications	1		0
Amounts reclassified from accumulated other comprehensive income (loss), net of tax	(3)		(8)
Other comprehensive loss, net of taxes	(2)	9	(8)	27
Balance, end of period	(550)		(550)
Pre-tax components of other comprehensive income (loss) and the related income tax expense (benefit)
Other comprehensive income (loss), before taxes	(3)	12	(10)	34
Income tax expense (benefit)	(1)	3	(2)	7
Other comprehensive loss, net of taxes	(2)	9	(8)	27
Net Unrealized Foreign Currency Translation [Member]
Accumulated other comprehensive income (loss) [Roll Forward]
Balance, beginning of period	(885)		(1,005)
Other comprehensive income (loss) before reclassifications	(111)		9
Amounts reclassified from accumulated other comprehensive income (loss), net of tax	0		0
Other comprehensive loss, net of taxes	(111)	(237)	9	(396)
Balance, end of period	(996)		(996)
Pre-tax components of other comprehensive income (loss) and the related income tax expense (benefit)
Other comprehensive income (loss), before taxes	(118)	(251)	13	(423)
Income tax expense (benefit)	(7)	(14)	4	(27)
Other comprehensive loss, net of taxes	$ (111)	$ (237)	$ 9	$ (396)