VIE - Classifications of Consolidated VIEs Included in the Consolidated Balance Sheets (Details) - USD ($) $ in Millions	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2017
Assets
Other short-term investments	$ 3,357		$ 1,825
Automobile loans	10,403		8,976
ALLL	(1,115)	$ (1,115)	(1,103)	$ (1,077)	$ (1,138)	$ (1,196)
Other assets	8,221		7,372
Liabilities
Other liabilities	3,422		2,498
Long-term debt	15,784		14,426
Variable Interest Entity, Primary Beneficiary
Assets
Other short-term investments	80		40
ALLL	10		4
Other assets	11		5
Liabilities
Other liabilities	3		1
Long-term debt	1,646		606
Variable Interest Entity, Primary Beneficiary | Indirect secured consumer loans
Assets
Other short-term investments	80		40
Automobile loans	1,755		668
ALLL	(10)		(4)
Other assets	11		5
Total Assets	1,836		709
Liabilities
Other liabilities	3		1
Long-term debt	1,646		606
Total liabilities	$ 1,649		$ 607