Investment Securities - Amortized Cost, Fair Value of MBS Issued by FNMA and FHLMC Exceeding 10% of Shareholders' Equity (Details) $ in Millions	Jun. 30, 2022 USD ($)
FNMA investments
Schedule of Debt Securities Exceeding Ten Percent of Stockholders Equity [Line Items]
Securities, amortized cost	$ 44,022
Securities, fair value	39,503
FHLMC investments
Schedule of Debt Securities Exceeding Ten Percent of Stockholders Equity [Line Items]
Securities, amortized cost	44,548
Securities, fair value	$ 39,828