Allowance for Credit Losses and Reserve for Unfunded Lending Commitments - Additional Information (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Accounts, Notes, Loans and Financing Receivable [Line Items]
Allowance for credit loss	$ 11,430	$ 15,564
Uncollectible portion of billed finance charges and fees	629	1,100	$ 1,400
Allowance for credit losses
Accounts, Notes, Loans and Financing Receivable [Line Items]
Increase (Decrease) in Allowance for Credit Loss	(4,100)
Allowance for credit loss	$ 11,400	$ 15,564	$ 7,208	$ 7,220