Unaudited Consolidated Statements of Stockholders' Equity - USD ($) $ in Thousands	Total	Common Stock	Additional Paid-In Capital	Retained Earnings	Accumulated Other Comprehensive Loss	Treasury Stock
Beginning balance at Dec. 31, 2018	$ 1,439,768	$ 718	$ 1,097,758	$ 1,029,518	$ (71,397)	$ (616,829)
Increase (Decrease) in Stockholders' Equity
Net loss	(24,388)			(24,388)
Currency translation adjustments (excluding intercompany advances)	(393)				(393)
Currency translation adjustments on intercompany advances	530				530
Stock-based compensation expense:
Restricted stock	8,537	8	8,529
Stock options	53		53
Stock repurchases	(757)					(757)
Surrender of stock to settle taxes on restricted stock awards	(3,622)					(3,622)
Ending balance at Jun. 30, 2019	1,419,728	726	1,106,340	1,005,130	(71,260)	(621,208)
Beginning balance at Mar. 31, 2019	1,427,644	725	1,102,176	1,014,870	(68,931)	(621,196)
Increase (Decrease) in Stockholders' Equity
Net loss	(9,740)			(9,740)
Currency translation adjustments (excluding intercompany advances)	(2,946)				(2,946)
Currency translation adjustments on intercompany advances	617				617
Stock-based compensation expense:
Restricted stock	4,165	1	4,164
Stock options	0
Stock repurchases	0
Surrender of stock to settle taxes on restricted stock awards	(12)					(12)
Ending balance at Jun. 30, 2019	1,419,728	726	1,106,340	1,005,130	(71,260)	(621,208)
Beginning balance at Dec. 31, 2019	1,223,967	726	1,114,521	797,710	(67,746)	(621,244)
Increase (Decrease) in Stockholders' Equity
Net loss	(429,667)			(429,667)
Currency translation adjustments (excluding intercompany advances)	(6,873)				(6,873)
Currency translation adjustments on intercompany advances	(9,148)				(9,148)
Stock-based compensation expense:
Restricted stock	3,257	7	3,250
Surrender of stock to settle taxes on restricted stock awards	(2,667)					(2,667)
Ending balance at Jun. 30, 2020	778,869	733	1,117,771	368,043	(83,767)	(623,911)
Beginning balance at Mar. 31, 2020	802,632	732	1,115,677	392,669	(82,537)	(623,909)
Increase (Decrease) in Stockholders' Equity
Net loss	(24,626)			(24,626)
Currency translation adjustments (excluding intercompany advances)	(788)				(788)
Currency translation adjustments on intercompany advances	(442)				(442)
Stock-based compensation expense:
Restricted stock	2,095	1	2,094
Surrender of stock to settle taxes on restricted stock awards	(2)					(2)
Ending balance at Jun. 30, 2020	$ 778,869	$ 733	$ 1,117,771	$ 368,043	$ (83,767)	$ (623,911)