Revenue Revenue - Narrative (Details) - Operating Segments - Automotive - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019	Dec. 31, 2019
Vehicles, parts, and accessories
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Revenue Performance Obligation Satisfied In Prior Period	$ 48	$ (350)
Extended service contracts
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Contract with Customer, Liability	4,000		$ 4,000		$ 4,200
Contract with Customer, Liability, Revenue Recognized	276	285	606	$ 590
Capitalized Contract Cost, Net	276		276		$ 270
Capitalized Contract Cost, Amortization	$ 19	$ 20	$ 39	$ 39