Condensed Consolidated Statements of Stockholders' Equity - USD ($) $ in Thousands	Common Stock	Treasury Stock	Additional Paid-In Capital	Accumulated Comprehensive Income / Loss	Accumulated Deficit	Noncontrolling Interest	Total
Beginning balance, shares at Dec. 31, 2017	50,639,926
Beginning balance, value at Dec. 31, 2017	$ 51	$ (34,640)	$ 648,996	$ (88)	$ (320,018)	$ 1,358	$ 295,659
Net loss					(60,465)		(60,465)
Cumulative effect of new accounting principle					2,506	308	2,814
Stock options exercised, shares	16,500
Stock options exercised, value			51				51
Compensation expense for share-based awards, net of forfeitures, shares	31,102
Compensation expense for share-based awards, net of forfeitures, value			1,225				1,225
Repurchase of restricted common stock, shares	(1,192,464)
Repurchase of restricted common stock, value	$ (2)	(4,632)	(7)				(4,641)
Net income attributable to noncontrolling interests in subsidiaries						(152)	(152)
Unrealized gain on foreign currency translation				(104)			(104)
Unrealized loss on short-term investments				(10)			(10)
Ending balance, shares at Jun. 30, 2018	49,495,064
Ending balance, value at Jun. 30, 2018	$ 49	(39,272)	650,265	(202)	(377,977)	1,513	234,376
Beginning balance, shares at Mar. 31, 2018	50,647,882
Beginning balance, value at Mar. 31, 2018	$ 51	(34,640)	649,724	(125)	(349,550)	1,593	267,053
Net loss					(28,427)		(28,427)
Stock options exercised, shares	6,500
Stock options exercised, value			20				20
Compensation expense for share-based awards, net of forfeitures, shares	31,102
Compensation expense for share-based awards, net of forfeitures, value			521				521
Repurchase of restricted common stock, shares	(1,190,420)
Repurchase of restricted common stock, value	$ (2)	(4,632)					(4,634)
Net income attributable to noncontrolling interests in subsidiaries						(79)	(79)
Unrealized gain on foreign currency translation				(87)			(87)
Unrealized loss on short-term investments				10			10
Ending balance, shares at Jun. 30, 2018	49,495,064
Ending balance, value at Jun. 30, 2018	$ 49	(39,272)	650,265	(202)	(377,977)	1,513	234,376
Beginning balance, shares at Dec. 31, 2018	49,639,319
Beginning balance, value at Dec. 31, 2018	$ 50	(39,272)	651,156	0	(422,541)	1,847	191,240
Net loss					(10,141)		(10,141)
Stock options exercised, shares	25,136
Stock options exercised, value			79				79
Compensation expense for share-based awards, net of forfeitures, shares	468,416
Compensation expense for share-based awards, net of forfeitures, value			453				453
Net income attributable to noncontrolling interests in subsidiaries						(14)	(14)
Ending balance, shares at Jun. 30, 2019	50,132,871
Ending balance, value at Jun. 30, 2019	$ 50	(39,272)	651,688	0	(432,682)	1,833	181,617
Beginning balance, shares at Mar. 31, 2019	49,656,067
Beginning balance, value at Mar. 31, 2019	$ 50	(39,272)	651,148	0	(426,925)	1,833	186,834
Net loss					(5,757)		(5,757)
Stock options exercised, shares	25,136
Stock options exercised, value			79				79
Compensation expense for share-based awards, net of forfeitures, shares	451,668
Compensation expense for share-based awards, net of forfeitures, value			461				461
Net income attributable to noncontrolling interests in subsidiaries							0
Ending balance, shares at Jun. 30, 2019	50,132,871
Ending balance, value at Jun. 30, 2019	$ 50	$ (39,272)	$ 651,688	$ 0	$ (432,682)	$ 1,833	$ 181,617