Investment Securities - Summary (Details) - USD ($) $ in Millions	9 Months Ended	12 Months Ended
	Sep. 30, 2026	Dec. 31, 2025
Debt Securities, Available-for-Sale [Line Items]
Accrued interest available-for-sale debt securities	$ 20	$ 3
Debt securities
Total	5,148
Estimated Fair Value	5,074
Equity securities
Cost	54	54
Gross Unrealized Gains	0	0
Gross Unrealized Losses	(11)	(8)
Estimated Fair Value	43	46
Total Cost	5,202	1,056
Total Gross Unrealized Gains	0	2
Total Gross Unrealized Losses	(85)	(16)
Total Estimated Fair Value	5,117	1,043
State and municipal obligations
Debt securities
Total	51	54
Gross Unrealized Gains	0	1
Gross Unrealized Losses	(9)	(7)
Estimated Fair Value	43	48
U.S. Government agency obligations
Debt securities
Total	3	3
Gross Unrealized Gains	0	0
Gross Unrealized Losses	0	0
Estimated Fair Value	3	3
U.S. Government treasury obligations
Debt securities
Total	4,067	138
Gross Unrealized Gains	0	1
Gross Unrealized Losses	(64)	0
Estimated Fair Value	4,003	138
Mortgage-backed securities
Debt securities
Total	9	10
Gross Unrealized Gains	0	0
Gross Unrealized Losses	(1)	0
Estimated Fair Value	8	9
Foreign government bonds and obligations
Debt securities
Total	938	717
Gross Unrealized Gains	0	0
Gross Unrealized Losses	0	0
Estimated Fair Value	938	717
Other
Debt securities
Total	80	81
Gross Unrealized Gains	0	0
Gross Unrealized Losses	0	0
Estimated Fair Value	$ 80	$ 81