Other Comprehensive Income (Loss) and Accumulated Other Comprehensive Income (Loss) (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2022	Mar. 31, 2021
Accumulated other comprehensive income (loss) [Roll Forward]
Balance, beginning of period	$ 28,887
Other comprehensive loss, net of taxes	(3,795)	$ (1,211)
Balance, end of period	25,531	28,269
Pre-tax components of other comprehensive income (loss) and the related income tax expense (benefit)
Other comprehensive income (loss), before taxes	(4,817)	(1,545)
Income tax expense (benefit)	(1,022)	(334)
Other comprehensive loss, net of taxes	(3,795)	(1,211)
Accumulated Other Comprehensive Income (Loss) [Member]
Accumulated other comprehensive income (loss) [Roll Forward]
Balance, beginning of period	1,193	2,502
Other comprehensive income (loss) before reclassifications	(3,802)
Amounts reclassified from accumulated other comprehensive income, net of tax	7
Other comprehensive loss, net of taxes	(3,795)	(1,211)
Balance, end of period	(2,602)	1,291
Pre-tax components of other comprehensive income (loss) and the related income tax expense (benefit)
Other comprehensive income (loss), before taxes	(4,817)	(1,545)
Income tax expense (benefit)	(1,022)	(334)
Other comprehensive loss, net of taxes	(3,795)	(1,211)
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	2,233
Other comprehensive income (loss) before reclassifications	(3,804)
Amounts reclassified from accumulated other comprehensive income, net of tax	(1)
Other comprehensive loss, net of taxes	(3,805)	(1,257)
Balance, end of period	(1,572)
Pre-tax components of other comprehensive income (loss) and the related income tax expense (benefit)
Other comprehensive income (loss), before taxes	(4,829)	(1,596)
Income tax expense (benefit)	(1,024)	(339)
Other comprehensive loss, net of taxes	(3,805)	(1,257)
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	182
Other comprehensive income (loss) before reclassifications	(1)
Amounts reclassified from accumulated other comprehensive income, net of tax	0
Other comprehensive loss, net of taxes	(1)	0
Balance, end of period	181
Pre-tax components of other comprehensive income (loss) and the related income tax expense (benefit)
Other comprehensive income (loss), before taxes	(1)	0
Income tax expense (benefit)	0	0
Other comprehensive loss, net of taxes	(1)	0
Net Benefit Plan Assets and Obligations Recognized in Shareholders' Equity [Member]
Accumulated other comprehensive income (loss) [Roll Forward]
Balance, beginning of period	(473)
Other comprehensive income (loss) before reclassifications	1
Amounts reclassified from accumulated other comprehensive income, net of tax	8
Other comprehensive loss, net of taxes	9	20
Balance, end of period	(464)
Pre-tax components of other comprehensive income (loss) and the related income tax expense (benefit)
Other comprehensive income (loss), before taxes	11	25
Income tax expense (benefit)	2	5
Other comprehensive loss, net of taxes	9	20
Net Unrealized Foreign Currency Translation [Member]
Accumulated other comprehensive income (loss) [Roll Forward]
Balance, beginning of period	(749)
Other comprehensive income (loss) before reclassifications	2
Amounts reclassified from accumulated other comprehensive income, net of tax	0
Other comprehensive loss, net of taxes	2	26
Balance, end of period	(747)
Pre-tax components of other comprehensive income (loss) and the related income tax expense (benefit)
Other comprehensive income (loss), before taxes	2	26
Income tax expense (benefit)	0	0
Other comprehensive loss, net of taxes	$ 2	$ 26