Revenue Revenue - Narrative (Details) - Operating Segments - Automotive - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2020	Mar. 31, 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	$ (885)	$ (481)
Extended service contracts
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Contract with Customer, Liability	4,100		$ 4,200
Contract with Customer, Liability, Revenue Recognized	330	305
Capitalized Contract Cost, Net	280		$ 270
Capitalized Contract Cost, Amortization	$ 20	$ 19