Goodwill, Customer Relationships and Trademarks - Goodwill and Intangible Assets (Details) - USD ($) $ in Thousands	Mar. 31, 2018	Dec. 31, 2017
Goodwill and Intangible Assets Disclosure [Abstract]
Goodwill	$ 120,154	$ 120,154
Finite-Lived Intangible Assets [Line Items]
Total	64,239
Customer Relationships - Acquired & Non-Compete Agreements
Finite-Lived Intangible Assets [Line Items]
Cost	99,576	93,371
Accumulated amortization	(49,578)	(46,681)
Total	49,998	46,690
Customer Relationships - Others
Finite-Lived Intangible Assets [Line Items]
Cost	12,336	12,336
Accumulated amortization	(6,382)	(5,534)
Total	5,954	6,802
Trademarks
Finite-Lived Intangible Assets [Line Items]
Cost	9,770	9,770
Accumulated amortization	(1,483)	(1,212)
Total	$ 8,287	$ 8,558