VIE - Classifications of Consolidated VIEs Included in the Consolidated Balance Sheets (Details) - USD ($) $ in Millions	Sep. 30, 2019	Jun. 30, 2019	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Dec. 31, 2017
Assets
Other short-term investments	$ 3,235		$ 1,825
Automobile loans	11,026		8,976
ALLL	(1,143)	$ (1,115)	(1,103)	$ (1,091)	$ (1,077)	$ (1,196)
Other assets	8,819		7,372
Liabilities
Other liabilities	2,425		2,498
Long-term debt	14,474		14,426
Variable Interest Entity, Primary Beneficiary
Assets
Other short-term investments	76		40
Automobile loans	1,543		668
ALLL	9		4
Other assets	11		5
Liabilities
Other liabilities	3		1
Long-term debt	1,438		606
Variable Interest Entity, Primary Beneficiary | Indirect secured consumer loans
Assets
Other short-term investments	76		40
Automobile loans	1,543		668
ALLL	(9)		(4)
Other assets	11		5
Total Assets	1,621		709
Liabilities
Other liabilities	3		1
Long-term debt	1,438		606
Total liabilities	$ 1,441		$ 607