Investment Securities (Details) - USD ($) $ in Millions	6 Months Ended	12 Months Ended
	Jun. 30, 2023	Dec. 31, 2022
Debt Securities, Available-for-Sale [Line Items]
Accrued interest available-for-sale debt securities	$ 5	$ 12
Debt securities
Cost	4,103
Estimated Fair Value	4,045
Equity securities
Cost	50	50
Gross Unrealized Gains	0	0
Gross Unrealized Losses	(8)	(9)
Estimated Fair Value	42	41
Total Cost	4,153	4,671
Total Gross Unrealized Gains	0	0
Total Gross Unrealized Losses	(66)	(93)
Total Estimated Fair Value	4,087	4,578
State and municipal obligations
Debt securities
Cost	63	64
Gross Unrealized Gains	0	0
Gross Unrealized Losses	(9)	(10)
Estimated Fair Value	54	54
U.S. Government agency obligations
Debt securities
Cost	4	5
Gross Unrealized Gains	0	0
Gross Unrealized Losses	0	0
Estimated Fair Value	4	5
U.S. Government treasury obligations
Debt securities
Cost	3,205	3,859
Gross Unrealized Gains	0	0
Gross Unrealized Losses	(48)	(73)
Estimated Fair Value	3,157	3,786
Mortgage-backed securities
Debt securities
Cost	13	13
Gross Unrealized Gains	0	0
Gross Unrealized Losses	(1)	0
Estimated Fair Value	12	13
Foreign government bonds and obligations
Debt securities
Cost	754	633
Gross Unrealized Gains	0	0
Gross Unrealized Losses	0	(1)
Estimated Fair Value	754	632
Other
Debt securities
Cost	64	47
Gross Unrealized Gains	0	0
Gross Unrealized Losses	0	0
Estimated Fair Value	$ 64	$ 47