Debt - Schedule of Debt (Details) - USD ($) $ in Millions	Mar. 31, 2017	Dec. 31, 2016
Short Term and Long Term Debt [Line Items]
Secured debt	$ 42,579	$ 39,270
Unsecured debt	37,370	34,606
Long-term Debt	79,949	73,876
Secured debt fair value	42,680	39,357
Unsecured debt fair value	38,390	35,220
Fair value of Secured and Unsecured debt	81,070	74,577
Level 2 [Member]
Short Term and Long Term Debt [Line Items]
Fair value of Secured and Unsecured debt	77,267	69,990
Level 3 [Member]
Short Term and Long Term Debt [Line Items]
Fair value of Secured and Unsecured debt	3,803	4,587
Revolving Credit Facility [Member]
Short Term and Long Term Debt [Line Items]
Secured debt	11,865	9,817
Unsecured debt	3,453	3,354
Secured debt fair value	11,866	9,812
Unsecured debt fair value	3,452	3,354
Securitization Notes Payable [Member] | Retail Finance Receivables [Member]
Short Term and Long Term Debt [Line Items]
Secured debt	30,714	29,453
Secured debt fair value	30,814	29,545
Senior Notes [Member]
Short Term and Long Term Debt [Line Items]
Unsecured debt	31,088	28,577
Unsecured debt fair value	32,103	29,182
Retail Customer Deposits [Member]
Short Term and Long Term Debt [Line Items]
Unsecured debt	1,913	1,895
Unsecured debt fair value	1,917	1,902
Other Unsecured Debt [Member]
Short Term and Long Term Debt [Line Items]
Unsecured debt	916	780
Unsecured debt fair value	$ 918	$ 782