Debt - Short Term and Long Term Debt (Details) - USD ($) $ in Millions	Dec. 31, 2021	Dec. 31, 2020
Short Term and Long Term Debt [Line Items]
Secured debt	$ 39,338	$ 39,982
Secured Debt, Fair Value Disclosure	39,401	40,380
Unsecured debt	53,223	52,443
Unsecured Debt, Fair Value Disclosure	54,357	54,568
Total Debt	92,561	92,425
Total secured and unsecured debt, Fair Value	93,758	94,948
Level 2
Short Term and Long Term Debt [Line Items]
Total secured and unsecured debt, Fair Value	92,250	92,922
Level 3
Short Term and Long Term Debt [Line Items]
Total secured and unsecured debt, Fair Value	1,508	2,026
Revolving credit facilities
Short Term and Long Term Debt [Line Items]
Secured debt	3,497	3,733
Secured Debt, Fair Value Disclosure	3,495	3,735
Unsecured debt	1,229	1,535
Unsecured Debt, Fair Value Disclosure	1,211	1,531
Securitization notes payable
Short Term and Long Term Debt [Line Items]
Secured debt	35,841	36,249
Secured Debt, Fair Value Disclosure	35,906	36,645
Senior Notes
Short Term and Long Term Debt [Line Items]
Unsecured debt	45,386	46,798
Unsecured Debt, Fair Value Disclosure	46,539	48,922
Other unsecured debt
Short Term and Long Term Debt [Line Items]
Unsecured debt	6,608	4,110
Unsecured Debt, Fair Value Disclosure	$ 6,607	$ 4,115