Goodwill and Intangible Assets - Intangible Assets (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended		12 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017	Dec. 31, 2017
Intangible assets
Gross Carrying Amount	$ 137,915		$ 137,915		$ 84,250
Accumulated Amortization	(43,826)		(43,826)		(39,450)
Amortization expense of intangible assets	2,700	$ 1,900	5,161	$ 3,611
Estimated future amortization expense for intangible assets
2018 (remaining six months)	6,280		6,280
2019	12,145		12,145
2020	9,394		9,394
2021	8,155		8,155
2022	6,989		6,989
Thereafter	51,126		51,126
Total	94,089		$ 94,089		$ 44,800
Tradename
Intangible assets
Weighted Average Life			9 years		9 years
Gross Carrying Amount	31,590		$ 31,590		$ 32,175
Accumulated Amortization	(23,451)		$ (23,451)		$ (22,238)
Customer relationships
Intangible assets
Weighted Average Life			16 years		16 years
Gross Carrying Amount	102,550		$ 102,550		$ 49,900
Accumulated Amortization	(19,239)		$ (19,239)		$ (16,338)
Non-compete agreements
Intangible assets
Weighted Average Life			5 years		5 years
Gross Carrying Amount	3,500		$ 3,500		$ 1,900
Accumulated Amortization	(1,037)		$ (1,037)		$ (820)
Other
Intangible assets
Weighted Average Life			3 years		3 years
Gross Carrying Amount	275		$ 275		$ 275
Accumulated Amortization	$ (99)		$ (99)		$ (54)