Fair Value of Financial Instruments - Reconciliation Level Three, Beneficial Interests in Securitizations (Details) - Variable Interest Entity, Not Primary Beneficiary - Level 3 - Fair Value, Measurements, Recurring - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Opening Balance	$ 239	$ 117	$ 131	$ 69
Transfers into Level 3	0	0	0	29
Received in securitization transactions	33	0	170	40
Cash receipts	(27)	(12)	(60)	(30)
Change in fair value	2	7	6	4
Ending Balance	$ 247	$ 112	$ 247	$ 112