Net Income (Loss) Per Share - Computation of Basic and Diluted Net Income (Loss) Per Share (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Numerator:
Net income (loss)	$ 7,104	$ (1,705)	$ 5,846	$ (3,021)
Less: preferred stock dividends	3	3	9	9
Net income (loss) attributable to common stockholders	$ 7,101	$ (1,708)	$ 5,837	$ (3,030)
Denominator:
Weighted-average shares outstanding - basic (in shares)	36,897	35,492	37,078	35,480
Add effect of dilutive securities:
Shares of common stock issuable upon conversion of preferred stock (in shares)	79	0	79	0
Weighted-average shares outstanding - diluted (in shares)	37,897	35,492	38,078	35,480
Basic net income (loss) per share (in dollars per share)	$ 0.19	$ (0.05)	$ 0.16	$ (0.09)
Diluted net income (loss) per share (in dollars per share)	$ 0.19	$ (0.05)	$ 0.15	$ (0.09)
Unvested restricted stock units
Add effect of dilutive securities:
Shares of common stock issuable to effect of share-based payment arrangements (in shares)	672	0	672	0
Stock options outstanding
Add effect of dilutive securities:
Shares of common stock issuable to effect of share-based payment arrangements (in shares)	0	0	0	0
Unvested restricted stock
Add effect of dilutive securities:
Shares of common stock issuable to effect of share-based payment arrangements (in shares)	249	0	249	0