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Net income (loss) per share attributable to common stockholders (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018	Jul. 31, 2019	Apr. 01, 2013
Numerator:
Net income (loss) attributable to common stockholders, basic and diluted	$ 216	$ 2,115	$ (4,937)	$ (1,114)
Denominator:
Weighted average common stock, basic (in shares)	44,041,000	41,961,000	43,786,000	41,645,000
Weighted average common stock, diluted (in shares)	44,378,000	45,219,000	43,786,000	41,645,000
Net income (loss) per share attributable to common stockholders:
Basic (in dollars per share)	$ 0.00	$ 0.05	$ (0.11)	$ (0.03)
Diluted (in dollars per share)	$ 0.00	$ 0.05	$ (0.11)	$ (0.03)
Stock repurchase program
Remaining approved amount for repurchases	$ 5,180		$ 5,180
RSUs
Net income (loss) per share attributable to common stockholders:
Shares of common stock excluded from the computation of diluted net income per share that were anti-dilutive	435,000	27,000
Stok options
Denominator:
Effect of dilutive	191,000	472,000	0	0
RSUs
Denominator:
Effect of dilutive	146,000	2,786,000	0	0
Maximum
Stock repurchase program
Amount of common stock approved by the entity for a stock repurchase program					$ 20,000	$ 10,000