Debt - Schedule of Debt (Details) - USD ($) $ in Millions	Jun. 30, 2017	Dec. 31, 2016
Short Term and Long Term Debt [Line Items]
Secured debt	$ 38,828	$ 35,087
Unsecured debt	39,651	29,476
Total secured and unsecured debt	78,479	64,563
Secured debt fair value	38,926	35,162
Unsecured debt fair value	40,645	30,045
Fair value of Secured and Unsecured debt	79,571	65,207
Level 2 [Member]
Short Term and Long Term Debt [Line Items]
Fair value of Secured and Unsecured debt	77,695	62,951
Level 3 [Member]
Short Term and Long Term Debt [Line Items]
Fair value of Secured and Unsecured debt	1,876	2,256
Revolving Credit Facility [Member]
Short Term and Long Term Debt [Line Items]
Secured debt	8,830	8,503
Unsecured debt	2,075	1,961
Secured debt fair value	8,844	8,498
Unsecured debt fair value	2,081	1,961
Securitization Notes Payable [Member] | Retail Finance Receivables [Member]
Short Term and Long Term Debt [Line Items]
Secured debt	29,998	26,584
Secured debt fair value	30,082	26,664
Senior Notes [Member]
Short Term and Long Term Debt [Line Items]
Unsecured debt	36,588	26,737
Unsecured debt fair value	37,574	27,304
Other Unsecured Debt [Member]
Short Term and Long Term Debt [Line Items]
Unsecured debt	988	778
Unsecured debt fair value	$ 990	$ 780