Accumulated Other Comprehensive Income - Schedule of Changes in AOCI (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2024	Jun. 30, 2023	Jun. 30, 2024	Jun. 30, 2023
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning balance	$ 14,547	$ 14,322	$ 14,637	$ 13,454
Other comprehensive income before reclassification, net of income taxes	8	(760)	(242)	(104)
Amounts reclassified from AOCI, net of income taxes	162	190	327	355
Total other comprehensive income (loss), net of tax	170	(570)	85	251
Ending balance	14,789	13,844	14,789	13,844
Accumulated Other Comprehensive Income (Loss)
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning balance	(5,314)	(5,474)	(5,229)	(6,295)
Total other comprehensive income (loss), net of tax	170	(570)	85	251
Ending balance	(5,144)	(6,044)	(5,144)	(6,044)
Unrealized gains (losses) on securities available for sale
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning balance	(4,341)	(4,320)	(4,190)	(4,895)
Other comprehensive income before reclassification, net of income taxes	51	(416)	(102)	159
Amounts reclassified from AOCI, net of income taxes	8	0	10	0
Total other comprehensive income (loss), net of tax	59	(416)	(92)	159
Ending balance	(4,282)	(4,736)	(4,282)	(4,736)
Unrealized gains (losses) on derivative financial instruments
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning balance	(698)	(879)	(763)	(1,124)
Other comprehensive income before reclassification, net of income taxes	(43)	(344)	(142)	(263)
Amounts reclassified from AOCI, net of income taxes	152	188	316	352
Total other comprehensive income (loss), net of tax	109	(156)	174	89
Ending balance	(589)	(1,035)	(589)	(1,035)
Net pension and postretirement benefit costs
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning balance	(275)	(275)	(276)	(276)
Other comprehensive income before reclassification, net of income taxes	0	0	2	0
Amounts reclassified from AOCI, net of income taxes	2	2	1	3
Total other comprehensive income (loss), net of tax	2	2	3	3
Ending balance	$ (273)	$ (273)	$ (273)	$ (273)