Leasing - Schedule of Ally as the Lessor (Details) - USD ($) $ in Millions	Mar. 31, 2025	Dec. 31, 2024
Property, Plant, and Equipment, Lessor Asset under Operating Lease [Line Items]
Vehicles	$ 9,361	$ 9,519
Accumulated depreciation	(1,482)	(1,528)
Investment in operating leases, net	$ 7,879	7,991
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	$ 2,300	$ 1,900
Vehicles | 50% Of Contract Residual Value
Property, Plant, and Equipment, Lessor Asset under Operating Lease [Line Items]
Residual value guarantee, percentage	50.00%	50.00%