Goodwill and Intangible Assets, Net - Narrative (Details) - USD ($) $ in Thousands, shares in Millions		3 Months Ended
	Apr. 12, 2018	Mar. 31, 2019	Mar. 31, 2018	Dec. 31, 2018
Business Acquisition [Line Items]
Goodwill		$ 9,353		$ 9,353
Amortization expense		400	$ 0
Class A Common Units
Business Acquisition [Line Items]
Number of shares issued to former stockholders (in shares)	0.5
Car360
Business Acquisition [Line Items]
Payments to acquire business, net of cash acquired	$ 16,700
Cash acquired	400
Payments to acquire businesses, net	6,700
Fair value, equity interested issued	10,000
Acquired net working capital	200
Fair value, intangible assets	9,900
Deferred tax liability	2,500	2,500
Deferred tax liability, amortization expense		400	$ 0
Goodwill	$ 9,400	$ 9,353		$ 9,353
Weighted average amortization period, definite-lived intangible assets		5 years 9 months 18 days
Car360 | Minimum
Business Acquisition [Line Items]
Deferred tax liability, amortization period		5 years
Car360 | Maximum
Business Acquisition [Line Items]
Deferred tax liability, amortization period		7 years