Consolidated Statements of Stockholders'/Members' Equity - USD ($) $ in Thousands	Total	Members' Equity	Notes Receivable Issued to Members	Common Stock Class A	Common Stock Class B	Common Stock Class C	Additional Paid In Capital	Retained Earnings	Accumulated Other Comprehensive Gain (Loss)	Non-controlling Interest
Balance at Dec. 31, 2014	$ 227,815	$ 245,981	$ (18,166)						$ 0	$ 0
Increase (Decrease) in Members' Equity
Net (loss) income	73,472	73,472
Distributions	(18,210)	(18,212)	2
Net settlement of recourse notes issued to Members	18,164		18,164
Taxes paid on behalf of employees for option exercises	(1,558)	(1,558)
Net settlement of outstanding vested options	(3,878)	(3,878)
Issuance of membership units for net settlement	3,878	3,878
Repurchase of Member options	(18,301)	(18,301)
Repurchase of units	(1,393)	(1,393)
Equity-based compensation expense	5,237	5,237
Issuance of membership units upon exercise of unit options	75	75
Foreign currency translation adjustments	(607)								(607)
Balance at Dec. 31, 2015	284,694	285,301	0						(607)	0
Increase (Decrease) in Members' Equity
Net (loss) income	31,368	31,368
Distributions	(28,110)	(28,110)
Taxes paid on behalf of employees for option exercises	(290)	(290)
Net settlement of outstanding vested options	(744)	(744)
Issuance of membership units for net settlement	744	744
Repurchase of member options and units	(15,148)	(15,148)
Equity-based compensation expense	4,969	4,969
Common units awarded	966	966
Foreign currency translation adjustments	(86)								(86)
Balance at Dec. 31, 2016	278,363	$ 279,056	$ 0						(693)	0
Increase (Decrease) in Members' Equity
Net (loss) income	(8,580)
Foreign currency translation adjustments	908
Balance (in shares) at Dec. 31, 2017				35,937,500	173,624,316	42,944,647
Balance at Dec. 31, 2017	$ 742,133			$ 36	$ 174	$ 43	$ 107,008	$ 1,602	$ 31	$ 633,239