Goodwill and Intangible Assets, Net (Schedule of Finite-Lived Intangible Assets by Major Category) (Details) - USD ($) $ in Thousands	Jun. 30, 2019	Dec. 31, 2018
Goodwill And Intangible Assets Disclosure [Abstract]
Customer lists and relationships	$ 108,110	$ 105,368
Non-compete agreements	23,035	22,923
Other	28,507	28,304
Intangible assets, at cost	159,652	156,595
Less: accumulated amortization	(145,523)	(142,429)
Intangible assets, net	$ 14,129	$ 14,166