Revenue Revenue - Narrative (Details) - Operating Segments - Automotive - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 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	$ 168	$ (454)
Extended service contracts
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Contract with Customer, Liability	4,100		$ 4,100		$ 4,200
Contract with Customer, Liability, Revenue Recognized	295	274	901	$ 864
Capitalized Contract Cost, Net	278		278		$ 270
Capitalized Contract Cost, Amortization	$ 20	$ 17	$ 59	$ 56