CONDENSED CONSOLIDATED STATEMENTS OF CHANGES IN SHAREHOLDERS' DEFICIT - USD ($) $ in Thousands	Common Stock	Additional Paid-in Capital	Accumulated Other Comprehensive Loss	Accumulated Deficit	Treasury Stock	Total
Balance at Dec. 31, 2017	$ 365	$ 333,738	$ (1,686)	$ (359,772)	$ (696)	$ (28,051)
Balance (in shares) at Dec. 31, 2017	36,372,000
Increase (Decrease) in Stockholders' Equity
Cumulative effect of a change in accounting | ASU 2014-09				(759)		(759)
Balance at Jan. 01, 2018	$ 365	333,738	(1,686)	(360,531)	(696)	(28,810)
Balance (in shares) at Jan. 01, 2018	36,372,000
Balance at Dec. 31, 2017	$ 365	333,738	(1,686)	(359,772)	(696)	(28,051)
Balance (in shares) at Dec. 31, 2017	36,372,000
Increase (Decrease) in Stockholders' Equity
Net income (loss)				(22,618)		(22,618)
Share-based compensation expense		2,585				2,585
Issuance of common stock upon vesting of restricted stock units	$ 4	(4)
Issuance of common stock upon vesting of restricted stock units (in shares)	372,000
Effect of shares withheld to cover taxes		(2,150)				(2,150)
Total other comprehensive (loss) income			(2,582)			(2,582)
Balance at Mar. 31, 2018	$ 369	334,169	(4,268)	(383,149)	(696)	(53,575)
Balance (in shares) at Mar. 31, 2018	36,744,000
Balance at Dec. 31, 2017	$ 365	333,738	(1,686)	(359,772)	(696)	(28,051)
Balance (in shares) at Dec. 31, 2017	36,372,000
Increase (Decrease) in Stockholders' Equity
Net income (loss)						(9,690)
Total other comprehensive (loss) income						(242)
Balance at Jun. 30, 2018	$ 370	337,175	(1,928)	(370,221)	(696)	(35,300)
Balance (in shares) at Jun. 30, 2018	36,850,000
Balance at Mar. 31, 2018	$ 369	334,169	(4,268)	(383,149)	(696)	(53,575)
Balance (in shares) at Mar. 31, 2018	36,744,000
Increase (Decrease) in Stockholders' Equity
Net income (loss)				12,928		12,928
Share-based compensation expense		3,320				3,320
Issuance of common stock upon vesting of restricted stock units	$ 1	(1)
Issuance of common stock upon vesting of restricted stock units (in shares)	106,000
Effect of shares withheld to cover taxes		(313)				(313)
Total other comprehensive (loss) income			2,340			2,340
Balance at Jun. 30, 2018	$ 370	337,175	(1,928)	(370,221)	(696)	(35,300)
Balance (in shares) at Jun. 30, 2018	36,850,000
Balance at Dec. 31, 2018	$ 371	343,955	(4,531)	(361,023)	(696)	$ (21,924)
Balance (in shares) at Dec. 31, 2018	36,921,000					36,921,174
Increase (Decrease) in Stockholders' Equity
Cumulative effect of a change in accounting | ASU 2016-02				1,561		$ 1,561
Balance at Jan. 01, 2019	$ 371	343,955	(4,531)	(359,462)	(696)	(20,363)
Balance (in shares) at Jan. 01, 2019	36,921,000
Balance at Dec. 31, 2018	$ 371	343,955	(4,531)	(361,023)	(696)	$ (21,924)
Balance (in shares) at Dec. 31, 2018	36,921,000					36,921,174
Increase (Decrease) in Stockholders' Equity
Net income (loss)				(6,951)		$ (6,951)
Share-based compensation expense		3,265				3,265
Issuance of common stock upon vesting of restricted stock units	$ 3	(3)
Issuance of common stock upon vesting of restricted stock units (in shares)	350,000
Effect of shares withheld to cover taxes		(3,626)				(3,626)
Total other comprehensive (loss) income			(2,930)			(2,930)
Balance at Mar. 31, 2019	$ 374	343,591	(7,461)	(366,413)	(696)	(30,605)
Balance (in shares) at Mar. 31, 2019	37,271,000
Balance at Dec. 31, 2018	$ 371	343,955	(4,531)	(361,023)	(696)	$ (21,924)
Balance (in shares) at Dec. 31, 2018	36,921,000					36,921,174
Increase (Decrease) in Stockholders' Equity
Net income (loss)						$ 3,084
Total other comprehensive (loss) income						(7,612)
Balance at Jun. 30, 2019	$ 375	347,012	(12,143)	(356,378)	(696)	$ (21,830)
Balance (in shares) at Jun. 30, 2019	37,335,000					37,335,266
Balance at Mar. 31, 2019	$ 374	343,591	(7,461)	(366,413)	(696)	$ (30,605)
Balance (in shares) at Mar. 31, 2019	37,271,000
Increase (Decrease) in Stockholders' Equity
Net income (loss)				10,035		10,035
Share-based compensation expense		3,450				3,450
Issuance of common stock upon vesting of restricted stock units	$ 1	(1)
Issuance of common stock upon vesting of restricted stock units (in shares)	64,000
Effect of shares withheld to cover taxes		(28)				(28)
Total other comprehensive (loss) income			(4,682)			(4,682)
Balance at Jun. 30, 2019	$ 375	$ 347,012	$ (12,143)	$ (356,378)	$ (696)	$ (21,830)
Balance (in shares) at Jun. 30, 2019	37,335,000					37,335,266