Description of Business and Summary of Significant Accounting Policies (Finite-lived Intangible Assets) (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018	Dec. 31, 2018
Finite-Lived and Indefinite-Lived Intangible Assets [Line items]
Finite-lived intangible assets, gross	$ 116,102		$ 116,102		$ 115,791
Finite-lived intangible assets, accumulated amortization	(69,646)		(69,646)		(64,343)
Finite-lived intangible assets, net	46,456		46,456		51,448
Amortization of Acquired Intangible Assets	2,200	$ 1,700	5,200	$ 3,600
Customer Relationships [Member]
Finite-Lived and Indefinite-Lived Intangible Assets [Line items]
Finite-lived intangible assets, gross	80,230		$ 80,230		80,070
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	19,215		$ 19,215		19,176
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	6,371		$ 6,371		6,315
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
Airport Contracts [Member]
Finite-Lived and Indefinite-Lived Intangible Assets [Line items]
Finite-lived intangible assets, gross	4,794		$ 4,794		4,752
Airport Contracts [Member] | Maximum [Member]
Finite-Lived and Indefinite-Lived Intangible Assets [Line items]
Finite-lived intangible asset, useful life			9 years
Store Networks [Member]
Finite-Lived and Indefinite-Lived Intangible Assets [Line items]
Finite-lived intangible assets, gross	828		$ 828		821
Store Networks [Member] | Maximum [Member]
Finite-Lived and Indefinite-Lived Intangible Assets [Line items]
Finite-lived intangible asset, useful life			5 years
Brand [Member]
Finite-Lived and Indefinite-Lived Intangible Assets [Line items]
Finite-lived intangible assets, gross	872		$ 872		864
Brand [Member] | Maximum [Member]
Finite-Lived and Indefinite-Lived Intangible Assets [Line items]
Finite-lived intangible asset, useful life			15 years
Trademarks [Member]
Finite-Lived and Indefinite-Lived Intangible Assets [Line items]
Finite-lived intangible assets, gross	2,676		$ 2,676		2,677
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