Goodwill, Customer Relationships and Trademarks - Goodwill and Intangible Assets (Details) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Goodwill and Intangible Assets Disclosure [Abstract]
Goodwill	$ 120,154	$ 79,147	$ 18,379	$ 0
Finite-Lived Intangible Assets [Line Items]
Total	62,050
Customer Relationships
Finite-Lived Intangible Assets [Line Items]
Cost	93,371	63,571
Accumulated amortization	(46,681)	(31,660)
Total	46,690	31,911
Customer Relationships— Other
Finite-Lived Intangible Assets [Line Items]
Cost	12,336	4,320
Accumulated amortization	(5,534)	(2,708)
Total	6,802	1,612	3,049	1,501
Trademarks
Finite-Lived Intangible Assets [Line Items]
Cost	9,770	6,770
Accumulated amortization	(1,212)	(431)
Total	$ 8,558	$ 6,339	$ 1,194	$ 0