Investment Securities - Amortized Cost and Estimated Fair Value of Securities by Contractual Maturity (Details) - USD ($) $ in Millions	Dec. 31, 2021	Dec. 31, 2020
Amortized Cost
Due in one year or less	$ 6
Due after one year through five years	7
Due after five years through 10 years	224
Due after 10 years	1,551
Amortized Cost	1,788
Fair Value
Due in one year or less	6
Due after one year through five years	7
Due after five years through 10 years	231
Due after 10 years	1,560
Fair Value	$ 1,804	$ 1,944
Weighted-Average Yield
Due in one year or less	2.15%
Due after one year through five years	4.19%
Due after five years through 10 years	2.84%
Due after 10 years	2.24%
Amortized Cost
Due in one year or less	$ 6
Due after one year through five years	3
Due after five years through 10 years	3
Due after 10 years	193
Amortized Cost	205	377
Fair Value
Due in one year or less	6
Due after one year through five years	3
Due after five years through 10 years	3
Due after 10 years	197
Fair value	$ 209	$ 393
Weighted-Average Yield
Due in one year or less	2.29%
Due after one year through five years	2.86%
Due after five years through 10 years	2.07%
Due after 10 years	2.49%