Allowance for Credit Losses and Reserve for Unfunded Lending Commitments - Summary of Loss Sharing Arrangements (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2022	Mar. 31, 2021
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Amounts expected to become due from (to) partners which reduced (increased) provision for credit losses	$ 677	$ (823)
Loss sharing agreements
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Expected reimbursement from loss sharing partners, beginning balance	1,450	2,159
Amounts due from partners which reduced net charge-offs	(107)	(141)
Amounts expected to become due from (to) partners which reduced (increased) provision for credit losses	23	(13)
Expected reimbursement from loss sharing partners, ending balance	$ 1,366	$ 2,005