Accumulated Other Comprehensive Income - Schedule of Changes in AOCI (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2023	Mar. 31, 2022
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning balance	$ 13,454
Other comprehensive income before reclassification, net of income taxes	654	$ (2,296)
Amounts reclassified from AOCI, net of income taxes	167	(47)
Total other comprehensive income (loss), net of tax	821	(2,343)
Ending balance	14,322
Accumulated Other Comprehensive Income (Loss)
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning balance	(6,295)	(586)
Total other comprehensive income (loss), net of tax	821	(2,343)
Ending balance	(5,474)	(2,929)
Unrealized gains (losses) on securities available for sale
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning balance	(4,895)	(403)
Other comprehensive income before reclassification, net of income taxes	575	(1,784)
Amounts reclassified from AOCI, net of income taxes	0	0
Total other comprehensive income (loss), net of tax	575	(1,784)
Ending balance	(4,320)	(2,187)
Unrealized gains (losses) on derivative financial instruments
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning balance	(1,124)	88
Other comprehensive income before reclassification, net of income taxes	80	(511)
Amounts reclassified from AOCI, net of income taxes	165	(50)
Total other comprehensive income (loss), net of tax	245	(561)
Ending balance	(879)	(473)
Net pension and postretirement benefit costs
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning balance	(276)	(271)
Other comprehensive income before reclassification, net of income taxes	(1)	(1)
Amounts reclassified from AOCI, net of income taxes	2	3
Total other comprehensive income (loss), net of tax	1	2
Ending balance	$ (275)	$ (269)