Net Income Per Share - Narrative (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended						9 Months Ended
	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Sep. 30, 2019	Sep. 30, 2018
Earnings Per Share [Abstract]
Net income	$ 19,983	$ 15,976	$ 3,284	$ 13,628	$ 6,588	$ 2,720	$ 39,243	$ 22,936
Weighted-average shares outstanding — basic (in shares)	41,771			39,432			41,283	39,015
Effect of dilutive securities from stock award plans (in shares)	1,281			1,428			1,513	1,222
Weighted-average shares outstanding — diluted (in shares)	43,052			40,860			42,796	40,237
Net income per share - basic (in dollars per share)	$ 0.48			$ 0.35			$ 0.95	$ 0.59
Net income per share - diluted (in dollars per share)	$ 0.46			$ 0.33			$ 0.92	$ 0.57
Anti-dilutive weighted-average shares related to stock award plans (in shares)	1,060			673			832	1,176