Investment Securities - Contractual Maturities (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2024	Dec. 31, 2023	Dec. 31, 2022
Total Estimated Fair Value
Due within 1 year	$ 953
Due after 1 year but within 5 years	166
Due after 5 years but within 10 years	33
Due after 10 years	40
Total	1,192	$ 2,120
Total Cost
Due within 1 year	955
Due after 1 year but within 5 years	166
Due after 5 years but within 10 years	32
Due after 10 years	50
Total	$ 1,203
Weighted average yields
Weighted average yields, due within 1 year	5.33%
Weighted average yields, due after 1 years but within 5 years	3.71%
Weighted average yields, due after 5 years but within 10 years	4.81%
Weighted average yield, due after 10 years	2.73%
Total	4.98%
U.S. statutory federal income tax rate	21.00%	21.00%	21.00%
State and municipal obligations
Total Estimated Fair Value
Due within 1 year	$ 0
Due after 1 year but within 5 years	0
Due after 5 years but within 10 years	23
Due after 10 years	26
Total	49	$ 55
Total Cost
Total	57	61
U.S. Government agency obligations
Total Estimated Fair Value
Due within 1 year	0
Due after 1 year but within 5 years	0
Due after 5 years but within 10 years	0
Due after 10 years	4
Total	4	4
Total Cost
Total	4	4
U.S. Government treasury obligations
Total Estimated Fair Value
Due within 1 year	189
Due after 1 year but within 5 years	98
Due after 5 years but within 10 years	0
Due after 10 years	0
Total	287	1,206
Total Cost
Total	289	1,217
Mortgage-backed securities
Total Estimated Fair Value
Due within 1 year	0
Due after 1 year but within 5 years	0
Due after 5 years but within 10 years	0
Due after 10 years	10
Total	10	11
Total Cost
Total	11	12
Foreign government bonds and obligations
Total Estimated Fair Value
Due within 1 year	764
Due after 1 year but within 5 years	1
Due after 5 years but within 10 years	0
Due after 10 years	0
Total	765	770
Total Cost
Total	765	770
Other
Total Estimated Fair Value
Due within 1 year	0
Due after 1 year but within 5 years	67
Due after 5 years but within 10 years	10
Due after 10 years	0
Total	77	74
Total Cost
Total	$ 77	$ 74