Investment Securities (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2022	Dec. 31, 2021
Available-for-sale debt securities:
Cost	$ 4,621
Estimated Fair Value	4,537	$ 2,512
Equity securities
Cost	50	66
Gross Unrealized Gains	0	17
Gross Unrealized Losses	(9)	(4)
Estimated Fair Value	41	79
Total Cost	4,671	2,548
Total Gross Unrealized Gains	0	48
Total Gross Unrealized Losses	(93)	(5)
Total Estimated Fair Value	4,578	2,591
State and municipal obligations
Available-for-sale debt securities:
Cost	64	106
Gross Unrealized Gains	0	5
Gross Unrealized Losses	(10)	0
Estimated Fair Value	54	111
U.S. Government agency obligations
Available-for-sale debt securities:
Cost	5	6
Gross Unrealized Gains	0	0
Gross Unrealized Losses	0	0
Estimated Fair Value	5	6
U.S. Government treasury obligations
Available-for-sale debt securities:
Cost	3,859	1,680
Gross Unrealized Gains	0	25
Gross Unrealized Losses	(73)	(1)
Estimated Fair Value	3,786	1,704
Mortgage-backed securities
Available-for-sale debt securities:
Cost	13	17
Gross Unrealized Gains	0	1
Gross Unrealized Losses	0	0
Estimated Fair Value	13	18
Foreign government bonds and obligations
Available-for-sale debt securities:
Cost	633	630
Gross Unrealized Gains	0	0
Gross Unrealized Losses	(1)	0
Estimated Fair Value	632	630
Other
Available-for-sale debt securities:
Cost	47	43
Gross Unrealized Gains	0	0
Gross Unrealized Losses	0	0
Estimated Fair Value	$ 47	$ 43