Investment Securities (Details) - USD ($) $ in Millions	3 Months Ended	12 Months Ended
	Mar. 31, 2023	Dec. 31, 2022
Debt Securities, Available-for-sale [Line Items]
Accrued interest available-for-sale debt securities	$ 12	$ 12
Available-for-sale debt securities:
Cost	3,981
Estimated Fair Value	3,922
Equity securities
Cost	50	50
Gross Unrealized Gains	0	0
Gross Unrealized Losses	(8)	(9)
Estimated Fair Value	42	41
Total Cost	4,031	4,671
Total Gross Unrealized Gains	0	0
Total Gross Unrealized Losses	(67)	(93)
Total Estimated Fair Value	3,964	4,578
State and municipal obligations
Available-for-sale debt securities:
Cost	63	64
Gross Unrealized Gains	0	0
Gross Unrealized Losses	(8)	(10)
Estimated Fair Value	55	54
U.S. Government agency obligations
Available-for-sale 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
Available-for-sale debt securities:
Cost	3,180	3,859
Gross Unrealized Gains	0	0
Gross Unrealized Losses	(50)	(73)
Estimated Fair Value	3,130	3,786
Mortgage-backed securities
Available-for-sale debt securities:
Cost	13	13
Gross Unrealized Gains	0	0
Gross Unrealized Losses	0	0
Estimated Fair Value	13	13
Foreign government bonds and obligations
Available-for-sale debt securities:
Cost	669	633
Gross Unrealized Gains	0	0
Gross Unrealized Losses	(1)	(1)
Estimated Fair Value	668	632
Other
Available-for-sale debt securities:
Cost	52	47
Gross Unrealized Gains	0	0
Gross Unrealized Losses	0	0
Estimated Fair Value	$ 52	$ 47