Investment Securities - Summary (Details) - USD ($) $ in Millions	6 Months Ended	12 Months Ended
	Jun. 30, 2025	Dec. 31, 2024
Debt Securities, Available-for-Sale [Line Items]
Accrued interest available-for-sale debt securities	$ 4	$ 3
Debt securities
Cost	1,221
Estimated Fair Value	1,213	1,192
Equity securities
Cost	53	53
Gross Unrealized Gains	0	4
Gross Unrealized Losses	(8)	(9)
Estimated Fair Value	45	48
Total Cost	1,274	1,256
Total Gross Unrealized Gains	1	5
Total Gross Unrealized Losses	(17)	(21)
Total Estimated Fair Value	1,258	1,240
State and municipal obligations
Debt securities
Cost	56	57
Gross Unrealized Gains	1	1
Gross Unrealized Losses	(8)	(9)
Estimated Fair Value	49	49
U.S. Government agency obligations
Debt securities
Cost	4	4
Gross Unrealized Gains	0	0
Gross Unrealized Losses	0	0
Estimated Fair Value	4	4
U.S. Government treasury obligations
Debt securities
Cost	303	289
Gross Unrealized Gains	0	0
Gross Unrealized Losses	(1)	(2)
Estimated Fair Value	302	287
Mortgage-backed securities
Debt securities
Cost	10	11
Gross Unrealized Gains	0	0
Gross Unrealized Losses	0	(1)
Estimated Fair Value	10	10
Foreign government bonds and obligations
Debt securities
Cost	767	765
Gross Unrealized Gains	0	0
Gross Unrealized Losses	0	0
Estimated Fair Value	767	765
Other
Debt securities
Cost	81	77
Gross Unrealized Gains	0	0
Gross Unrealized Losses	0	0
Estimated Fair Value	$ 81	$ 77