Goodwill, Customer Relationships and Trademarks - Changes in Goodwill, Customer Relationships and Trademarks (Details) $ in Thousands	9 Months Ended
	Sep. 30, 2018 USD ($)
Goodwill [Roll Forward]
Balance at beginning of period	$ 120,154
Adjustments	189
Balance at end of period	120,343
Finite-lived Intangible Assets [Roll Forward]
Balance at end of period	54,354
Customer Relationships - Acquired & Non-Compete Agreements
Finite-lived Intangible Assets [Roll Forward]
Balance at beginning of period	46,690
Additions	6,205
Adjustments	(174)
Amortization	(11,990)
Balance at end of period	40,731
Customer Relationships - Others
Finite-lived Intangible Assets [Roll Forward]
Balance at beginning of period	6,802
Additions	1,744
Amortization	(2,670)
Balance at end of period	5,876
Trademarks
Finite-lived Intangible Assets [Roll Forward]
Balance at beginning of period	8,558
Amortization	(811)
Balance at end of period	$ 7,747