Variable Interest Entities - Multi-seller Conduits (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019
Variable Interest Entity [Line Items]
Off-balance sheet lending-related financial commitments, contractual amount	$ 1,165,688	$ 1,108,399
Firm-administered multi-seller conduits
Variable Interest Entity [Line Items]
Commercial paper eliminated in consolidation	13,500	16,300
Commercial and other | Firm-administered multi-seller conduits
Variable Interest Entity [Line Items]
Off-balance sheet lending-related financial commitments, contractual amount	$ 12,200	$ 8,900
Maximum
Variable Interest Entity [Line Items]
Program-wide credit enhancement required amount	10.00%