Summary of Significant Accounting Policies (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2022	Mar. 31, 2021
Supplemental cash flow information - Noncash activities
Available-for-sale debt securities purchased from securitization of LHFS	$ 1,053	$ 0
Held-to-maturity debt securities purchased from securitization of LHFS	638	10,252
Transfers from loans to LHFS	2,827	6,249
Transfers from available-for-sale debt securities to held-to-maturity debt securities	$ 14,651	$ 16,617