Investment Securities - Amortized Cost and Estimated Fair Value of Securities by Contractual Maturity (Details) - USD ($) $ in Millions	Mar. 31, 2022	Dec. 31, 2021
Investment Securities Available-for-Sale, Amortized Cost
Due in one year or less	$ 6
Due after one year through five years	9
Due after five years through 10 years	211
Due after 10 years	1,858
Amortized Cost	2,084	$ 1,788
Investment Securities Available-for-Sale, Fair Value
Due in one year or less	6
Due after one year through five years	9
Due after five years through 10 years	208
Due after 10 years	1,787
Fair Value	$ 2,010	1,804
Investment Securities Available-for-Sale, Weighted Average Yield
Due in one year or less (as a percent)	2.16%
Due after one year through five years (as a percent)	4.65%
Due after five years through 10 years (as a percent)	2.86%
Due after 10 years (as a percent)	2.27%
Investment Securities Held-to-maturity, Amortized cost
Due in one year or less	$ 5
Due after one year through five years	3
Due after five years through 10 years	3
Due after 10 years	179
Amortized Cost	190	205
Investment Securities Held-to-maturity, Fair Value
Due in one year or less	5
Due after one year through five years	3
Due after five years through 10 years	3
Due after 10 years	175
Fair Value	$ 186	$ 209
Investment Securities Held-to-maturity, Weighted Average Yield
Due in one year or less (as a percent)	2.21%
Due after one year through five years (as a percent)	2.86%
Due after five years through 10 years (as a percent)	2.01%
Due after 10 years (as a percent)	2.49%