Allowance for Credit Losses and Reserve for Unfunded Lending Commitments - Summary of Loss Sharing Arrangements (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Provision (benefit) for credit losses	$ (1,944)	$ 10,264	$ 6,236
Loss sharing agreements
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Expected reimbursement from loss sharing partners, beginning balance	2,159	1,162	379
Amounts due from partners which reduced net charge-offs	(438)	(959)	(600)
Provision (benefit) for credit losses	(271)	952	1,383
Expected reimbursement from loss sharing partners, ending balance	$ 1,450	2,159	1,162
Loss sharing agreements | including CECL Impact Adoption
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Expected reimbursement from loss sharing partners, beginning balance		$ 2,166
Expected reimbursement from loss sharing partners, ending balance			$ 2,166