- Schedule of Revenue Categories (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018
Revenue Information
Revenues (includes related party contra revenue of $345 and $0 for the three months ended June 30, 2019 and 2018, respectively, and $509 and $0 for the six months ended June 30 2019 and 2018, respectively)	$ 88,075	$ 87,850	$ 173,657	$ 168,911
Dealer revenue
Revenue Information
Revenues (includes related party contra revenue of $345 and $0 for the three months ended June 30, 2019 and 2018, respectively, and $509 and $0 for the six months ended June 30 2019 and 2018, respectively)	78,977	75,271	155,791	147,608
OEM incentives revenue
Revenue Information
Revenues (includes related party contra revenue of $345 and $0 for the three months ended June 30, 2019 and 2018, respectively, and $509 and $0 for the six months ended June 30 2019 and 2018, respectively)	4,143	7,927	8,344	12,348
Forecasts, consulting and other revenue
Revenue Information
Revenues (includes related party contra revenue of $345 and $0 for the three months ended June 30, 2019 and 2018, respectively, and $509 and $0 for the six months ended June 30 2019 and 2018, respectively)	$ 4,955	$ 4,652	$ 9,522	$ 8,955