Investment Securities - Schedule of Amortized Cost and Fair Value by Contractual Maturity (Details) - USD ($) $ in Millions	Sep. 30, 2024	Dec. 31, 2023
Amortized Cost
Within 1 year	$ 0
After 1 year through 5 years	0
After 5 years through 10 years	0
After 10 years	0
Subtotal	0
Government agency issued MBS and CMO	1,282
Total	1,282
Fair Value
Within 1 year	0
After 1 year through 5 years	0
After 5 years through 10 years	0
After 10 years	0
Subtotal	0
Government agency issued MBS and CMO	1,144
Fair Value	1,144	$ 1,161
Amortized Cost
Within 1 year	41
After 1 year through 5 years	123
After 5 years through 10 years	378
After 10 years	1,307
Subtotal	1,849
Government agency issued MBS and CMO	7,284
Securities available for sale, amortized cost	9,133
Fair Value
Within 1 year	41
After 1 year through 5 years	117
After 5 years through 10 years	352
After 10 years	1,184
Subtotal	1,694
Government agency issued MBS and CMO	6,554
Securities available-for-sale	$ 8,248	$ 8,391