Investment Securities - Gross Unrealized Losses and Fair Value of Investment Securities (Details) $ in Millions	Jun. 30, 2025 USD ($)
Schedule Of Fair Value And Gross Unrealized Losses [Line Items]
Less Than 12 Months, Fair Value	$ 19,746
Less Than 12 Months, Unrealized Losses	(172)
12 Months or Greater, Fair Value	50,165
12 Months or Greater, Unrealized Losses	(5,701)
Total, Fair Value	69,911
Total, Unrealized Losses	(5,873)
U.S. Treasury and agencies
Schedule Of Fair Value And Gross Unrealized Losses [Line Items]
Less Than 12 Months, Fair Value	5,810
Less Than 12 Months, Unrealized Losses	(12)
12 Months or Greater, Fair Value	21,142
12 Months or Greater, Unrealized Losses	(1,670)
Total, Fair Value	26,952
Total, Unrealized Losses	(1,682)
Residential mortgage-backed securities
Schedule Of Fair Value And Gross Unrealized Losses [Line Items]
Less Than 12 Months, Fair Value	11,136
Less Than 12 Months, Unrealized Losses	(127)
12 Months or Greater, Fair Value	13,786
12 Months or Greater, Unrealized Losses	(1,613)
Total, Fair Value	24,922
Total, Unrealized Losses	(1,740)
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	7,615
12 Months or Greater, Unrealized Losses	(1,018)
Total, Fair Value	7,615
Total, Unrealized Losses	(1,018)
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	1,607
Less Than 12 Months, Unrealized Losses	(2)
12 Months or Greater, Fair Value	0
12 Months or Greater, Unrealized Losses	0
Total, Fair Value	1,607
Total, Unrealized Losses	(2)
Obligations of state and political subdivisions
Schedule Of Fair Value And Gross Unrealized Losses [Line Items]
Less Than 12 Months, Fair Value	1,193
Less Than 12 Months, Unrealized Losses	(31)
12 Months or Greater, Fair Value	7,615
12 Months or Greater, Unrealized Losses	(1,400)
Total, Fair Value	8,808
Total, Unrealized Losses	$ (1,431)