Loans - Purchased, Sold and Reclassified to Held-for-Sale (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Accounts, Notes, Loans and Financing Receivable [Line Items]
Purchases	$ 712	$ 846	$ 2,085	$ 4,079
Sales	20,529	5,986	46,888	17,490
Retained loans reclassified to held-for-sale	4,248	666	10,734	1,962
Consumer, excluding credit card
Accounts, Notes, Loans and Financing Receivable [Line Items]
Purchases	259	561	1,044	2,164
Sales	14,970	1,789	30,484	4,661
Retained loans reclassified to held-for-sale	3,889	0	8,950	36
Excluded retained loans purchased from correspondents that were originated in accordance with the Firm's underwriting standards	4,700	5,600	12,200	14,500
Credit card
Accounts, Notes, Loans and Financing Receivable [Line Items]
Purchases	0	0	0	0
Sales	0	0	0	0
Retained loans reclassified to held-for-sale	0	0	0	0
Wholesale
Accounts, Notes, Loans and Financing Receivable [Line Items]
Purchases	453	285	1,041	1,915
Sales	5,559	4,197	16,404	12,829
Retained loans reclassified to held-for-sale	$ 359	$ 666	$ 1,784	$ 1,926