Loans - Purchased, Sold and Reclassified to Held-for-Sale (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Retained Loans Purchases Sales and Transfer Into Held For Sale By Portfolio Segment [Line Items]
Purchases	$ 4,897	$ 5,260	$ 5,564
Sales	26,725	14,468	15,107
Retained loans reclassified to held-for-sale	2,312	7,569	2,702
Consumer, excluding credit card
Retained Loans Purchases Sales and Transfer Into Held For Sale By Portfolio Segment [Line Items]
Purchases	2,543	3,461	4,116
Sales	9,984	3,405	6,368
Retained loans reclassified to held-for-sale	36	6,340	321
Excluded retained loans purchased from correspondents that were originated in accordance with the Firm's underwriting standards	18,600	23,500	30,400
Credit card
Retained Loans Purchases Sales and Transfer Into Held For Sale By Portfolio Segment [Line Items]
Purchases	0	0	0
Sales	0	0	0
Retained loans reclassified to held-for-sale	0	0	0
Wholesale
Retained Loans Purchases Sales and Transfer Into Held For Sale By Portfolio Segment [Line Items]
Purchases	2,354	1,799	1,448
Sales	16,741	11,063	8,739
Retained loans reclassified to held-for-sale	$ 2,276	$ 1,229	$ 2,381