AFS and HTM Debt Securities, HTM Debt Securities Purchases and Transfers (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2022	Mar. 31, 2021
Debt Securities, Held-to-maturity Purchase or Transfer of Investment [Abstract]
Purchases of held-to-maturity debt securities	$ 2,989	$ 30,759
Transfers from available-for-sale debt securities to held-to-maturity debt securities	14,651	16,617
Securities of U.S. states and political subdivisions [Member]
Debt Securities, Held-to-maturity Purchase or Transfer of Investment [Abstract]
Purchases of held-to-maturity debt securities	834	1,910
Federal agency mortgage-backed securities [Member]
Debt Securities, Held-to-maturity Purchase or Transfer of Investment [Abstract]
Purchases of held-to-maturity debt securities	2,051	24,867
Transfers from available-for-sale debt securities to held-to-maturity debt securities	14,651	16,617
Non-agency mortgage-backed securities [Member]
Debt Securities, Held-to-maturity Purchase or Transfer of Investment [Abstract]
Purchases of held-to-maturity debt securities	104	29
Collateralized loan obligations [Member]
Debt Securities, Held-to-maturity Purchase or Transfer of Investment [Abstract]
Purchases of held-to-maturity debt securities	$ 0	$ 3,953