Accumulated Other Comprehensive Income - Schedule of Changes in AOCI (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2025	Sep. 30, 2024	Sep. 30, 2025	Sep. 30, 2024
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning balance	$ 19,484	$ 14,789	$ 18,176	$ 14,637
Other comprehensive income before reclassification, net of income taxes	276	1,007	1,104	765
Amounts reclassified from AOCI, net of income taxes	76	856	217	1,183
Total other comprehensive income (loss), net of tax	352	1,863	1,321	1,948
Ending balance	20,102	16,852	20,102	16,852
Accumulated Other Comprehensive Income (Loss)
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning balance	(2,501)	(5,144)	(3,470)	(5,229)
Ending balance	(2,149)	(3,281)	(2,149)	(3,281)
Unrealized gains (losses) on securities available for sale
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning balance	(2,158)	(4,282)	(2,734)	(4,190)
Other comprehensive income before reclassification, net of income taxes	301	951	877	850
Amounts reclassified from AOCI, net of income taxes	0	712	0	721
Total other comprehensive income (loss), net of tax	301	1,663	877	1,571
Ending balance	(1,857)	(2,619)	(1,857)	(2,619)
Unrealized gains (losses) on derivative financial instruments
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning balance	(108)	(589)	(434)	(763)
Other comprehensive income before reclassification, net of income taxes	(24)	57	161	(85)
Amounts reclassified from AOCI, net of income taxes	74	142	215	458
Total other comprehensive income (loss), net of tax	50	199	376	373
Ending balance	(58)	(390)	(58)	(390)
Net pension and postretirement benefit costs
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning balance	(235)	(273)	(302)	(276)
Other comprehensive income before reclassification, net of income taxes	(1)	(1)	66	0
Amounts reclassified from AOCI, net of income taxes	2	2	2	4
Total other comprehensive income (loss), net of tax	1	1	68	4
Ending balance	$ (234)	$ (272)	$ (234)	$ (272)