Loans - Purchased, Sold and Reclassified to Held-for-Sale (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
Accounts, Notes, Loans and Financing Receivable [Line Items]
Purchases	$ 780	$ 2,169
Sales	14,103	4,170
Retained loans reclassified to held-for-sale	4,614	904
Consumer, excluding credit card
Accounts, Notes, Loans and Financing Receivable [Line Items]
Purchases	551	1,071
Sales	8,658	481
Retained loans reclassified to held-for-sale	4,113	36
Excluded retained loans purchased from correspondents that were originated in accordance with the Firm's underwriting standards	3,200	3,600
Credit card
Accounts, Notes, Loans and Financing Receivable [Line Items]
Purchases	0	0
Sales	0	0
Retained loans reclassified to held-for-sale	0	0
Wholesale
Accounts, Notes, Loans and Financing Receivable [Line Items]
Purchases	229	1,098
Sales	5,445	3,689
Retained loans reclassified to held-for-sale	$ 501	$ 868