Consolidated Statements of Stockholders' Equity - USD ($) shares in Thousands, $ in Thousands	Total	Common stock	Additional paid-in capital	Accumulated other comprehensive income (loss)	Accumulated deficit
Beginning balance (in shares) at Dec. 31, 2017		44,219
Beginning balance at Dec. 31, 2017	$ 194,451	$ 111	$ 545,953	$ 398	$ (352,011)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Comprehensive income (loss)	(12,143)			6,103	(18,246)
Issuance of common stock upon exercise of stock options (in shares)		40
Issuance of common stock upon exercise of stock options	142	$ 0	142
Issuance of common stock under employee stock purchase plan (in shares)		0
Issuance of common stock under employee stock purchase plan	0	$ 0	0
Issuance of common stock for vested restricted stock units (in shares)		64
Issuance of common stock for vested restricted stock units	0	$ 0	0
Tax withholding related to vesting of restricted stock units (in shares)		(9)
Tax withholding related to vesting of restricted stock units	(60)		(60)
Stock-based compensation costs	3,154		3,154
Ending Balance (in shares) at Mar. 31, 2018		44,314
Ending balance at Mar. 31, 2018	183,720	$ 111	549,189	6,501	(372,081)
Beginning balance (in shares) at Dec. 31, 2018		46,378
Beginning balance at Dec. 31, 2018	160,240	$ 116	564,722	(7,126)	(397,472)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Comprehensive income (loss)	(11,154)			2,937	(14,091)
Issuance of common stock upon exercise of stock options (in shares)		48
Issuance of common stock upon exercise of stock options	166		166
Issuance of common stock under employee stock purchase plan (in shares)		0
Issuance of common stock under employee stock purchase plan	0	$ 0	0
Issuance of common stock for vested restricted stock units (in shares)		42
Issuance of common stock for vested restricted stock units	0
Tax withholding related to vesting of restricted stock units (in shares)		(13)
Tax withholding related to vesting of restricted stock units	(82)		(82)
Stock-based compensation costs	3,388		3,388
Ending Balance (in shares) at Mar. 31, 2019		46,455
Ending balance at Mar. 31, 2019	$ 152,558	$ 116	$ 568,194	$ (4,189)	$ (411,563)