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		6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016
Numerator:
Net income (loss)	$ (9,341)	$ 2,676	$ (20,863)	$ 4,986
Denominator:
Basic	43,219	41,603	42,919	41,362
Dilutive effect of equity awards		2,717		2,680
Diluted	43,219	44,320	42,919	44,042
Basic net income (loss) per share	$ (0.22)	$ 0.06	$ (0.49)	$ 0.12
Diluted net income (loss) per share	$ (0.22)	$ 0.06	$ (0.49)	$ 0.11