Condenced 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
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Impact of adoption of new accounting standard ASU 2016-16	$ (1,824)				$ (1,824)
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)	(31,162)			(2,379)	(28,783)
Issuance of common stock upon exercise of stock options (in shares)		189
Issuance of common stock upon exercise of stock options	703		703
Issuance of common stock under employee stock purchase plan (in shares)		234
Issuance of common stock under employee stock purchase plan	1,242	$ 1	1,241
Issuance of common stock for vested restricted stock units (in shares)		312
Issuance of common stock for vested restricted stock units	0
Tax withholding related to vesting of restricted stock units (in shares)		(48)
Tax withholding related to vesting of restricted stock units	(276)		(276)
Stock-based compensation costs	6,324		6,324
Ending Balance (in shares) at Jun. 30, 2018		44,906
Ending balance at Jun. 30, 2018	169,458	$ 112	553,945	(1,981)	(382,618)
Beginning balance (in shares) at Mar. 31, 2018		44,314
Beginning balance at Mar. 31, 2018	183,720	$ 111	549,189	6,501	(372,081)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Comprehensive income (loss)	(19,019)			(8,482)	(10,537)
Issuance of common stock upon exercise of stock options (in shares)		149
Issuance of common stock upon exercise of stock options	561		561
Issuance of common stock under employee stock purchase plan (in shares)		234
Issuance of common stock under employee stock purchase plan	1,242	$ 1	1,241
Issuance of common stock for vested restricted stock units (in shares)		248
Issuance of common stock for vested restricted stock units	0
Tax withholding related to vesting of restricted stock units (in shares)		(39)
Tax withholding related to vesting of restricted stock units	(216)		(216)
Stock-based compensation costs	3,170		3,170
Ending Balance (in shares) at Jun. 30, 2018		44,906
Ending balance at Jun. 30, 2018	169,458	$ 112	553,945	(1,981)	(382,618)
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)	(20,270)			1,147	(21,417)
Issuance of common stock upon exercise of stock options (in shares)		166
Issuance of common stock upon exercise of stock options	572		572
Issuance of common stock under employee stock purchase plan (in shares)		254
Issuance of common stock under employee stock purchase plan	1,235	$ 1	1,234
Issuance of common stock for vested restricted stock units (in shares)		423
Issuance of common stock for vested restricted stock units	0	$ 1	(1)
Tax withholding related to vesting of restricted stock units (in shares)		(69)
Tax withholding related to vesting of restricted stock units	(327)		(327)
Stock-based compensation costs	6,534		6,534
Ending Balance (in shares) at Jun. 30, 2019		47,152
Ending balance at Jun. 30, 2019	147,984	$ 118	572,734	(5,979)	(418,889)
Beginning balance (in shares) at Mar. 31, 2019		46,455
Beginning balance at Mar. 31, 2019	152,558	$ 116	568,194	(4,189)	(411,563)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Comprehensive income (loss)	(9,116)			(1,790)	(7,326)
Issuance of common stock upon exercise of stock options (in shares)		118
Issuance of common stock upon exercise of stock options	406		406
Issuance of common stock under employee stock purchase plan (in shares)		254
Issuance of common stock under employee stock purchase plan	1,235	$ 1	1,234
Issuance of common stock for vested restricted stock units (in shares)		381
Issuance of common stock for vested restricted stock units	0	$ 1	(1)
Tax withholding related to vesting of restricted stock units (in shares)		(56)
Tax withholding related to vesting of restricted stock units	(245)		(245)
Stock-based compensation costs	3,146		3,146
Ending Balance (in shares) at Jun. 30, 2019		47,152
Ending balance at Jun. 30, 2019	$ 147,984	$ 118	$ 572,734	$ (5,979)	$ (418,889)