Investment Securities - Gross Unrealized Losses and Fair Value of Investment Securities (Details) $ in Millions	Jun. 30, 2024 USD ($)
Schedule Of Fair Value And Gross Unrealized Losses [Line Items]
Less Than 12 Months, Fair Value	$ 14,353
Less Than 12 Months, Unrealized Losses	(55)
12 Months or Greater, Fair Value	53,722
12 Months or Greater, Unrealized Losses	(7,097)
Total, Fair Value	68,075
Total, Unrealized Losses	(7,152)
U.S. Treasury and agencies
Schedule Of Fair Value And Gross Unrealized Losses [Line Items]
Less Than 12 Months, Fair Value	7,891
Less Than 12 Months, Unrealized Losses	(13)
12 Months or Greater, Fair Value	17,447
12 Months or Greater, Unrealized Losses	(2,192)
Total, Fair Value	25,338
Total, Unrealized Losses	(2,205)
Residential mortgage-backed securities
Schedule Of Fair Value And Gross Unrealized Losses [Line Items]
Less Than 12 Months, Fair Value	1,891
Less Than 12 Months, Unrealized Losses	(16)
12 Months or Greater, Fair Value	19,724
12 Months or Greater, Unrealized Losses	(2,348)
Total, Fair Value	21,615
Total, Unrealized Losses	(2,364)
Commercial mortgage-backed securities | Agency
Schedule Of Fair Value And Gross Unrealized Losses [Line Items]
Less Than 12 Months, Fair Value	0
Less Than 12 Months, Unrealized Losses	0
12 Months or Greater, Fair Value	7,274
12 Months or Greater, Unrealized Losses	(1,415)
Total, Fair Value	7,274
Total, Unrealized Losses	(1,415)
Commercial mortgage-backed securities | Non-agency
Schedule Of Fair Value And Gross Unrealized Losses [Line Items]
Less Than 12 Months, Fair Value	0
Less Than 12 Months, Unrealized Losses	0
12 Months or Greater, Fair Value	7
12 Months or Greater, Unrealized Losses	0
Total, Fair Value	7
Total, Unrealized Losses	0
Asset-backed securities
Schedule Of Fair Value And Gross Unrealized Losses [Line Items]
Less Than 12 Months, Fair Value	2,897
Less Than 12 Months, Unrealized Losses	(8)
12 Months or Greater, Fair Value	1,560
12 Months or Greater, Unrealized Losses	(18)
Total, Fair Value	4,457
Total, Unrealized Losses	(26)
Obligations of state and political subdivisions
Schedule Of Fair Value And Gross Unrealized Losses [Line Items]
Less Than 12 Months, Fair Value	1,540
Less Than 12 Months, Unrealized Losses	(18)
12 Months or Greater, Fair Value	7,706
12 Months or Greater, Unrealized Losses	(1,124)
Total, Fair Value	9,246
Total, Unrealized Losses	(1,142)
Other
Schedule Of Fair Value And Gross Unrealized Losses [Line Items]
Less Than 12 Months, Fair Value	134
Less Than 12 Months, Unrealized Losses	0
12 Months or Greater, Fair Value	4
12 Months or Greater, Unrealized Losses	0
Total, Fair Value	138
Total, Unrealized Losses	$ 0