Investment Securities - Gross Unrealized Losses Ratio to Fair Value (Details) $ in Millions	Sep. 30, 2025 USD ($) security	Dec. 31, 2024 USD ($) security
Number of Securities
Less than 12 months | security	0	0
12 months or more | security	10	45
Total | security	10	45
Estimated Fair Value
Less than 12 months	$ 0	$ 0
12 months or more	25	152
Total	25	152
Gross Unrealized Losses
Less than 12 months	0	0
12 months or more	(7)	(12)
Total	$ (7)	$ (12)
90–100%
Number of Securities
Less than 12 months | security	0	0
12 months or more | security	5	30
Total | security	5	30
Estimated Fair Value
Less than 12 months	$ 0	$ 0
12 months or more	7	129
Total	7	129
Gross Unrealized Losses
Less than 12 months	0	0
12 months or more	(1)	(3)
Total	$ (1)	$ (3)
Less than 90%
Number of Securities
Less than 12 months | security	0	0
12 months or more | security	5	15
Total | security	5	15
Estimated Fair Value
Less than 12 months	$ 0	$ 0
12 months or more	18	23
Total	18	23
Gross Unrealized Losses
Less than 12 months	0	0
12 months or more	(7)	(9)
Total	$ (7)	$ (9)