Goodwill, Finite-Lived, and Indefinite-Lived Intangibles ( Finite-Lived and Indefinite-Lived Intangible Assets) (Details) - USD ($) $ in Thousands	3 Months Ended			9 Months Ended
	Dec. 31, 2020	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019	Dec. 31, 2019
Finite-lived intangible assets:
Finite-lived intangible assets, gross		$ 133,683		$ 133,683		$ 121,575
Accumulated amortization		(80,819)		(80,819)		(74,620)
Finite-lived intangibles, net		52,864		52,864		46,955
Indefinite-lived intangibles:
Amortization of acquired intangible assets		2,400	$ 2,700	7,100	$ 7,900
Customer relationships
Finite-lived intangible assets:
Finite-lived intangible assets, gross		95,788		95,788		83,012
Developed technology
Finite-lived intangible assets:
Finite-lived intangible assets, gross		19,718		19,718		19,979
Dealer network
Finite-lived intangible assets:
Finite-lived intangible assets, gross		6,595		6,595		6,726
Airport contracts
Finite-lived intangible assets:
Finite-lived intangible assets, gross		4,486		$ 4,486		4,635
Indefinite-lived intangibles:
Finite-lived intangible asset, useful life				9 years
Trademarks
Finite-lived intangible assets:
Finite-lived intangible assets, gross		2,678		$ 2,678		2,689
Store networks
Finite-lived intangible assets:
Finite-lived intangible assets, gross		2,420		$ 2,420		2,500
Indefinite-lived intangibles:
Finite-lived intangible asset, useful life				5 years
Brand
Finite-lived intangible assets:
Finite-lived intangible assets, gross		889		$ 889		918
Indefinite-lived intangibles:
Finite-lived intangible asset, useful life				15 years
Non-compete agreements
Finite-lived intangible assets:
Finite-lived intangible assets, gross		757		$ 757		764
Indefinite-lived intangibles:
Finite-lived intangible asset, useful life				5 years
Database
Finite-lived intangible assets:
Finite-lived intangible assets, gross		212		$ 212		212
Indefinite-lived intangibles:
Finite-lived intangible asset, useful life				10 years
Backlog
Finite-lived intangible assets:
Finite-lived intangible assets, gross		140		$ 140		140
Customer relationships
Indefinite-lived intangibles:
Customer/territorial relationships		27,815		27,815		$ 42,055
Customer relationships | E-Z Data
Indefinite-lived intangibles:
Indefinite-lived intangible assets recognized				14,200
Reclassified intangible as finite-lived				$ 14,200
Finite-lived intangible asset, useful life				15 years
Amortization of acquired intangible assets		$ 237
Customer relationships | Forecast | E-Z Data
Indefinite-lived intangibles:
Amortization of acquired intangible assets	$ 237