Net Income 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	$ 8,452	$ 4,996	$ 37,584	$ 13,317
Denominator:
Basic (shares)	37,703	35,477	37,162	35,074
Common stock options (shares)	2,199	3,103	2,161	3,089
Restricted stock units (shares)	397	132	278	42
Diluted (shares)	40,299	38,712	39,601	38,205
Basic (USD per share)	$ 0.22	$ 0.14	$ 1.01	$ 0.38
Diluted (USD per share)	$ 0.21	$ 0.13	$ 0.95	$ 0.35
Antidilutive Securities
Antidilutive securities (shares)	651	2,881	1,244	3,632
Stock Options
Antidilutive Securities
Antidilutive securities (shares)	651	2,881	1,244	3,594
Restricted Stock Units
Antidilutive Securities
Antidilutive securities (shares)	0	0	0	38