Intangible Assets - Changes in Goodwill, Customer Relationships and Trademarks (Details) $ in Thousands	6 Months Ended
	Jun. 30, 2019 USD ($)
Goodwill [Roll Forward]
Balance at beginning of period	$ 120,343
Balance at end of period	120,343
Finite-lived Intangible Assets [Roll Forward]
Balance at end of period	45,674
Customer Relationships— Acquired & Non-Compete Agreements
Finite-lived Intangible Assets [Roll Forward]
Balance at beginning of period	36,194
Amortization	(7,282)
Balance at end of period	28,912
Customer Relationships— Other
Finite-lived Intangible Assets [Roll Forward]
Balance at beginning of period	6,865
Additions	6,913
Amortization	(3,413)
Balance at end of period	10,365
Trademarks
Finite-lived Intangible Assets [Roll Forward]
Balance at beginning of period	7,287
Amortization	(890)
Balance at end of period	$ 6,397