Variable Interest Entities - Multi-seller Conduits (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Variable Interest Entity [Line Items]
Off-balance sheet lending-related financial commitments, contractual amount	$ 1,039,258	$ 991,482	$ 975,152
Firm-administered multi-seller conduits
Variable Interest Entity [Line Items]
Commercial paper issued by consolidated Variable Interest Entities eliminated in Consolidation	20,100	20,400
Firm-administered multi-seller conduits | Commercial and other
Variable Interest Entity [Line Items]
Off-balance sheet lending-related financial commitments, contractual amount	$ 8,000	$ 8,800
Maximum
Variable Interest Entity [Line Items]
Program-wide credit enhancement required amount	10.00%