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, 2015		40,986
Beginning balance at Dec. 31, 2015	$ 211,656	$ 102	$ 511,750	$ (1,723)	$ (298,473)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Comprehensive loss	(6,883)			(6,678)	(205)
Issuance of common stock upon exercise of stock options (in shares)		1,013
Issuance of common stock upon exercise of stock options	3,671	$ 3	3,668
Issuance of common stock under employee stock purchase plan (in shares)		351
Issuance of common stock under employee stock purchase plan	2,779	$ 1	2,778
Issuance of common stock for vested restricted stock units (in shares)		226
Issuance of common stock for vested restricted stock units	0	$ 0	0
Tax withholding related to vesting of restricted stock units (in shares)		(50)
Tax withholding related to vesting of restricted stock units	(615)		(615)
Stock-based compensation costs	14,797		14,797
Ending Balance (in shares) at Dec. 31, 2016		42,526
Ending balance at Dec. 31, 2016	225,405	$ 106	532,378	(8,401)	(298,678)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Comprehensive loss	(44,534)			8,799	(53,333)
Issuance of common stock upon exercise of stock options (in shares)		665
Issuance of common stock upon exercise of stock options	2,483	$ 2	2,481
Issuance of common stock under employee stock purchase plan (in shares)		349
Issuance of common stock under employee stock purchase plan	2,393	$ 1	2,392
Issuance of common stock for vested restricted stock units (in shares)		806
Issuance of common stock for vested restricted stock units	0	$ 2	(2)
Tax withholding related to vesting of restricted stock units (in shares)		(127)
Tax withholding related to vesting of restricted stock units	(998)		(998)
Stock-based compensation costs	9,702		9,702
Ending Balance (in shares) at Dec. 31, 2017		44,219
Ending balance at Dec. 31, 2017	194,451	$ 111	545,953	398	(352,011)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Comprehensive loss	(51,161)			(7,524)	(43,637)
Issuance of common stock upon exercise of stock options (in shares)		779
Issuance of common stock upon exercise of stock options	3,422	$ 2	3,420
Issuance of common stock under employee stock purchase plan (in shares)		404
Issuance of common stock under employee stock purchase plan	2,191	$ 1	2,190
Issuance of common stock for vested restricted stock units (in shares)		1,124
Issuance of common stock for vested restricted stock units	0	$ 2	(2)
Tax withholding related to vesting of restricted stock units (in shares)		(148)
Tax withholding related to vesting of restricted stock units	(954)		(954)
Stock-based compensation costs	14,115		14,115
Ending Balance (in shares) at Dec. 31, 2018		46,378
Ending balance at Dec. 31, 2018	$ 160,240	$ 116	$ 564,722	$ (7,126)	$ (397,472)