Consolidated Statements of Changes in Stockholders' Equity - USD ($) $ in Thousands	Total	Common Stock	Additional Paid-in Capital	Treasury Stock	Accumulated Other Comprehensive Loss	Accumulated Deficit
Beginning balance (in shares) at Dec. 31, 2018		143,444,178		0
Beginning balance at Dec. 31, 2018	$ 174,454	$ 14	$ 961,235	$ 0	$ (3,211)	$ (783,584)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Vesting of restricted shares (in shares)		116,526
Vesting of restricted shares	0
Exercise of stock options (in shares)		892
Exercise of stock options	5		5
Other comprehensive gain (loss)	(1,362)				(1,362)
Net loss	(3,488)					(3,488)
Stock-based compensation	9,016		9,016
Ending balance (in shares) at Mar. 31, 2019		143,561,596		0
Ending balance at Mar. 31, 2019	178,625	$ 14	970,256	$ 0	(4,573)	(787,072)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Vesting of restricted shares (in shares)		2,176,738
Vesting of restricted shares	0
Exercise of stock options (in shares)		2,918
Exercise of stock options	16		16
Other comprehensive gain (loss)	458				458
Net loss	(26,228)					(26,228)
Stock-based compensation	9,354		9,354
Ending balance (in shares) at Jun. 30, 2019		145,741,252		0
Ending balance at Jun. 30, 2019	162,225	$ 14	979,626	$ 0	(4,115)	(813,300)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Vesting of restricted shares (in shares)		398,293
Vesting of restricted shares	0	$ 1	(1)
Exercise of stock options (in shares)		1,331
Exercise of stock options	5		5
Other comprehensive gain (loss)	(761)				(761)
Net loss	7,816					7,816
Stock-based compensation	9,143		9,143
Ending balance (in shares) at Sep. 30, 2019		146,140,876		0
Ending balance at Sep. 30, 2019	178,428	$ 15	988,773	$ 0	(4,876)	(805,484)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Vesting of restricted shares (in shares)		117,340
Vesting of restricted shares	0
Exercise of stock options (in shares)		1,652
Exercise of stock options	6		6
Other comprehensive gain (loss)	788				788
Net loss	9,553					9,553
Stock-based compensation	8,179		8,179
Ending balance (in shares) at Dec. 31, 2019		146,259,868		0
Ending balance at Dec. 31, 2019	196,954	$ 15	996,958	$ 0	(4,088)	(795,931)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Vesting of restricted shares (in shares)		1,306,607
Vesting of restricted shares	0
Exercise of stock options (in shares)		3,597
Exercise of stock options	13		13
Other comprehensive gain (loss)	(185)				(185)
Net loss	(2,244)					(2,244)
Stock-based compensation	9,836		9,836
Repurchase of common stock (in shares)				(7,603,620)
Repurchase of common stock	(12,329)			$ (12,329)
Ending balance (in shares) at Mar. 31, 2020		147,570,072		(7,603,620)
Ending balance at Mar. 31, 2020	$ 192,045	$ 15	$ 1,006,807	$ (12,329)	$ (4,273)	$ (798,175)