Investment Securities - Narrative (Details) - USD ($) $ in Millions	1 Months Ended	12 Months Ended
	Jan. 31, 2022	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Debt Securities Exceeding Ten Percent of Stockholders Equity [Line Items]
Debt Securities, Available-for-sale, Allowance for Credit Loss		$ 0	$ 0
Transfer of HTM securities to AFS		0	$ 0	$ 18,022
Held to Maturity Discount Discount		1,200
Subsequent Event
Debt Securities Exceeding Ten Percent of Stockholders Equity [Line Items]
Debt Securities, Available for Sale Amortized Cost, after Allowance for Credit Loss, Transfer, Amount	$ 21,300
FNMA investments
Debt Securities Exceeding Ten Percent of Stockholders Equity [Line Items]
Securities, amortized cost		45,200
Securities, fair value		44,600
FHLMC investments
Debt Securities Exceeding Ten Percent of Stockholders Equity [Line Items]
Securities, amortized cost		46,600
Securities, fair value		$ 45,700