Loans - Purchased, Sold and Reclassified to Held-for-Sale (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Loans and Leases Receivable Disclosure [Line Items]
Purchases	$ 4,633	$ 2,573	$ 4,897
Sales	18,268	53,919	26,725
Retained loans reclassified to held-for-sale	4,451	11,559	2,312
Consumer, excluding credit card
Loans and Leases Receivable Disclosure [Line Items]
Purchases	3,474	1,282	2,543
Sales	352	30,474	9,984
Retained loans reclassified to held-for-sale	2,084	9,188	36
Excluded retained loans purchased from correspondents that were originated in accordance with the Firm's underwriting standards	15,300	16,600	18,600
Credit card
Loans and Leases Receivable Disclosure [Line Items]
Purchases	0	0	0
Sales	0	0	0
Retained loans reclassified to held-for-sale	787	0	0
Wholesale
Loans and Leases Receivable Disclosure [Line Items]
Purchases	1,159	1,291	2,354
Sales	17,916	23,445	16,741
Retained loans reclassified to held-for-sale	$ 1,580	$ 2,371	$ 2,276