Net Income Per Share (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended	6 Months Ended
Jun. 30, 2020	Mar. 31, 2020	Jun. 30, 2019	Mar. 31, 2019	Jun. 30, 2020	Jun. 30, 2019
Numerator:
Net income	$ 26,319	$ 18,694	$ 16,232	$ 13,266	$ 45,013	$ 29,498
Denominator:
Basic (shares)	39,161		39,198		39,137	39,143
Common stock options (shares)	1,382		1,890		1,410	1,950
Restricted stock units (shares)	376		442		381	477
Diluted (shares)	40,919		41,530		40,928	41,570
Basic (USD per share)	$ 0.67		$ 0.41		$ 1.15	$ 0.75
Diluted (USD per share)	$ 0.64		$ 0.39		$ 1.10	$ 0.71
Antidilutive Securities
Antidilutive securities (shares)	454		473		603	443
Stock Options
Antidilutive Securities
Antidilutive securities (shares)	452		419		585	381
Restricted Stock Units
Antidilutive Securities
Antidilutive securities (shares)	2		54		18	62

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The amount of net income (loss) for the period per each share of common stock or unit outstanding during the reporting period.

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The amount of net income (loss) for the period available to each share of common stock or common unit outstanding during the reporting period and to each share or unit that would have been outstanding assuming the issuance of common shares or units for all dilutive potential common shares or units outstanding during the reporting period.

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