Debt - Schedule of Debt (Details) - USD ($) $ in Millions	Sep. 30, 2019	Dec. 31, 2018
Short Term and Long Term Debt [Line Items]
Secured debt	$ 39,029	$ 42,835
Unsecured debt	50,099	48,153
Total secured and unsecured debt	89,128	90,988
Secured debt fair value	39,265	42,835
Unsecured debt fair value	50,954	47,556
Fair value of Secured and Unsecured debt	90,219	90,391
Level 2 [Member]
Short Term and Long Term Debt [Line Items]
Fair value of Secured and Unsecured debt	88,388	88,305
Level 3 [Member]
Short Term and Long Term Debt [Line Items]
Fair value of Secured and Unsecured debt	1,831	2,086
Revolving Credit Facility [Member]
Short Term and Long Term Debt [Line Items]
Secured debt	2,109	3,410
Unsecured debt	1,665	2,157
Secured debt fair value	2,115	3,413
Unsecured debt fair value	1,665	2,151
Securitization Notes Payable [Member]
Short Term and Long Term Debt [Line Items]
Secured debt	36,920	39,425
Secured debt fair value	37,150	39,422
Senior Notes [Member]
Short Term and Long Term Debt [Line Items]
Unsecured debt	45,117	42,611
Unsecured debt fair value	45,965	42,015
Other Unsecured Debt [Member]
Short Term and Long Term Debt [Line Items]
Unsecured debt	3,317	3,385
Unsecured debt fair value	$ 3,324	$ 3,390