Statement of Stockholders' Equity - USD ($) $ in Thousands	Common Stock	Additional Paid-in Capital	Accumulated Other Comprehensive Loss	Accumulated Deficit	Total
Increase (Decrease) in Stockholders' Equity
Adoption of ASU 2016-09 (see Note 1) | Accounting Standard Update 2016 09		$ 401		$ (401)
Balance, restated	$ 466	553,290	$ (1,441)	(238,361)	$ 313,954
Balance (Scenario, Previously Reported) at Dec. 31, 2016	$ 466	552,889	(1,441)	(237,960)	313,954
Balance at Dec. 31, 2016					313,954
Balance (in shares) (Scenario, Previously Reported) at Dec. 31, 2016	46,567,978
Balance (in shares) at Dec. 31, 2016	46,567,978
Increase (Decrease) in Stockholders' Equity
Issuance of common stock upon exercise and vesting of stock awards	$ 2	1,678			1,680
Issuance of common stock upon exercise and vesting of stock awards (in shares)	252,278
Issuance of common stock under the employee stock purchase plan		442			442
Issuance of common stock under the employee stock purchase plan (in shares)	34,506
Comprehensive income (loss)			201	(21,519)	(21,318)
Stock-based compensation expense		6,607			6,607
Balance at Jun. 30, 2017	$ 468	$ 562,017	$ (1,240)	$ (259,880)	$ 301,365
Balance (in shares) at Jun. 30, 2017	46,854,762