- Schedule of Revenue Categories (Details) - USD ($) $ in Thousands	3 Months Ended
Mar. 31, 2019	Mar. 31, 2018
Revenue Information
Revenues (includes related party contra revenue of $163 and $0 for the three months ended March 31, 2019 and 2018, respectively)	$ 85,582	$ 81,061
Dealer revenue
Revenue Information
Revenues (includes related party contra revenue of $163 and $0 for the three months ended March 31, 2019 and 2018, respectively)	76,814	72,337
OEM incentives revenue
Revenue Information
Revenues (includes related party contra revenue of $163 and $0 for the three months ended March 31, 2019 and 2018, respectively)	4,201	4,421
Forecasts, consulting and other revenue
Revenue Information
Revenues (includes related party contra revenue of $163 and $0 for the three months ended March 31, 2019 and 2018, respectively)	$ 4,567	$ 4,303

Amount, excluding tax collected from customer, of revenue from satisfaction of performance obligation by transferring promised good or service to customer. Tax collected from customer is tax assessed by governmental authority that is both imposed on and concurrent with specific revenue-producing transaction, including, but not limited to, sales, use, value added and excise.

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 606
-SubTopic 10
-Section 50
-Paragraph 4
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=109196051&loc=SL49130543-203045

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 606
-SubTopic 10
-Section 50
-Paragraph 1
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=109196051&loc=SL49130539-203045

Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 606
-SubTopic 10
-Section 50
-Paragraph 5
-URI http://asc.fasb.org/extlink&oid=109196051&loc=SL49130545-203045

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Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration