Description of Business and Summary of Significant Accounting Policies (Finite-lived Intangible Assets) (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017	Dec. 31, 2017
Finite-Lived and Indefinite-Lived Intangible Assets [Line items]
Finite-lived intangible assets, gross	$ 99,059		$ 99,059		$ 103,196
Finite-lived intangible assets, accumulated amortization	(62,111)		(62,111)		(57,485)
Finite-lived intangible assets, net	36,948		36,948		45,711
Amortization of Acquired Intangible Assets	1,600	$ 1,800	5,200	$ 5,400
Customer Relationships [Member]
Finite-Lived and Indefinite-Lived Intangible Assets [Line items]
Finite-lived intangible assets, gross	72,665		$ 72,665		73,725
Customer Relationships [Member] | Minimum [Member]
Finite-Lived and Indefinite-Lived Intangible Assets [Line items]
Finite-lived intangible asset, useful life			7 years
Customer Relationships [Member] | Maximum [Member]
Finite-Lived and Indefinite-Lived Intangible Assets [Line items]
Finite-lived intangible asset, useful life			20 years
Developed technology [Member]
Finite-Lived and Indefinite-Lived Intangible Assets [Line items]
Finite-lived intangible assets, gross	16,613		$ 16,613		15,076
Developed technology [Member] | Minimum [Member]
Finite-Lived and Indefinite-Lived Intangible Assets [Line items]
Finite-lived intangible asset, useful life			3 years
Developed technology [Member] | Maximum [Member]
Finite-Lived and Indefinite-Lived Intangible Assets [Line items]
Finite-lived intangible asset, useful life			12 years
Dealer Networks [Member]
Finite-Lived and Indefinite-Lived Intangible Assets [Line items]
Finite-lived intangible assets, gross	5,496		$ 5,496		10,581
Dealer Networks [Member] | Minimum [Member]
Finite-Lived and Indefinite-Lived Intangible Assets [Line items]
Finite-lived intangible asset, useful life			15 years
Dealer Networks [Member] | Maximum [Member]
Finite-Lived and Indefinite-Lived Intangible Assets [Line items]
Finite-lived intangible asset, useful life			20 years
Trademarks [Member]
Finite-Lived and Indefinite-Lived Intangible Assets [Line items]
Finite-lived intangible assets, gross	3,169		$ 3,169		2,698
Trademarks [Member] | Minimum [Member]
Finite-Lived and Indefinite-Lived Intangible Assets [Line items]
Finite-lived intangible asset, useful life			3 years
Trademarks [Member] | Maximum [Member]
Finite-Lived and Indefinite-Lived Intangible Assets [Line items]
Finite-lived intangible asset, useful life			15 years
Backlog [Member] | Maximum [Member]
Finite-Lived and Indefinite-Lived Intangible Assets [Line items]
Finite-lived intangible asset, useful life			1 year 2 months
Non-compete agreements [Member]
Finite-Lived and Indefinite-Lived Intangible Assets [Line items]
Finite-lived intangible assets, gross	764		$ 764		764
Non-compete agreements [Member] | Maximum [Member]
Finite-Lived and Indefinite-Lived Intangible Assets [Line items]
Finite-lived intangible asset, useful life			5 years
Backlog [Member]
Finite-Lived and Indefinite-Lived Intangible Assets [Line items]
Finite-lived intangible assets, gross	140		$ 140		140
Database [Member]
Finite-Lived and Indefinite-Lived Intangible Assets [Line items]
Finite-lived intangible assets, gross	212		$ 212		212
Database [Member] | Maximum [Member]
Finite-Lived and Indefinite-Lived Intangible Assets [Line items]
Finite-lived intangible asset, useful life			10 years
Customer Relationships [Member]
Finite-Lived and Indefinite-Lived Intangible Assets [Line items]
Indefinite-lived intangible assets	$ 42,055		$ 42,055		$ 42,055