Leasing (Ally as the Lessor) (Details) - USD ($) $ in Millions	Mar. 31, 2023	Dec. 31, 2022
Property, Plant, and Equipment, Lessor Asset under Operating Lease [Line Items]
Residual value guarantee, percentage	15.00%	15.00%
Vehicles	$ 12,148	$ 12,304
Accumulated depreciation	(1,912)	(1,860)
Investment in operating leases, net	$ 10,236	10,444
Minimum
Property, Plant, and Equipment, Lessor Asset under Operating Lease [Line Items]
Lessor, term of contract	24 months
Maximum
Property, Plant, and Equipment, Lessor Asset under Operating Lease [Line Items]
Lessor, term of contract	60 months
Vehicles
Property, Plant, and Equipment, Lessor Asset under Operating Lease [Line Items]
Residual value of leased asset	$ 43	$ 56