Securities - Schedule of Securities by Maturity (Details) - USD ($) $ in Millions	Mar. 31, 2024	Dec. 31, 2023
Securities Available for Sale, Amortized Cost
Due in one year or less	$ 7,707
Due after one through five years	9,648
Due after five through ten years	18,828
Due after ten years	6,822
Total	43,005
Securities Available for Sale, Fair Value
Due in one year or less	7,539
Due after one through five years	8,923
Due after five through ten years	15,614
Due after ten years	5,222
Total	37,298	$ 37,185
Held-to-Maturity Securities, Amortized Cost
Due in one year or less	624
Due after one through five years	4,164
Due after five through ten years	2,382
Due after ten years	1,102
Total	8,272	8,575
Held-to-Maturity Securities, Fair Value
Due in one year or less	604
Due after one through five years	3,916
Due after five through ten years	2,145
Due after ten years	1,015
Total	$ 7,680	$ 8,056