CONDENSED CONSOLIDATED STATEMENTS OF STOCKHOLDERS' EQUITY - USD ($) $ in Thousands	Total	Common Stock	Additional Paid-in Capital	Retained Earnings	Treasury Stock	Accumulated Other Comprehensive Loss
Beginning balance at Dec. 31, 2018	$ 1,048,231	$ 702	$ 632,235	$ 863,768	$ (355,857)	$ (92,617)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	11,576			11,576
Other comprehensive income (loss)	(2,019)					(2,019)
Stock-based compensation	30,328		30,328
Shares issued and forfeited, net, under stock plans	9,260		(1,910)		11,170
Repurchase of common stock	(35,617)				(35,617)
Repurchase of stock-based compensation awards for tax withholdings	(2,822)				(2,822)
Ending balance at Sep. 30, 2019	1,058,937	702	660,653	875,344	(383,126)	(94,636)
Beginning balance at Jun. 30, 2019	1,052,577	702	650,797	843,530	(349,426)	(93,026)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	31,814			31,814
Other comprehensive income (loss)	(1,610)					(1,610)
Stock-based compensation	9,371		9,371
Shares issued and forfeited, net, under stock plans	1,784		485		1,299
Repurchase of common stock	(34,986)				(34,986)
Repurchase of stock-based compensation awards for tax withholdings	(13)				(13)
Ending balance at Sep. 30, 2019	1,058,937	702	660,653	875,344	(383,126)	(94,636)
Beginning balance at Dec. 31, 2019	1,129,968	702	667,658	930,830	(377,639)	(91,583)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	5,514			5,514
Other comprehensive income (loss)	(4,909)					(4,909)
Stock-based compensation	22,943		22,943
Shares issued and forfeited, net, under stock plans	9,359		(14,660)		24,019
Repurchase of common stock	(28,881)				(28,881)
Repurchase of stock-based compensation awards for tax withholdings	(11,150)				(11,150)
Ending balance at Sep. 30, 2020	1,122,844	702	675,941	936,344	(393,651)	(96,492)
Beginning balance at Jun. 30, 2020	1,090,737	702	667,554	920,478	(399,663)	(98,334)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	15,866			15,866
Other comprehensive income (loss)	1,842					1,842
Stock-based compensation	8,061		8,061
Shares issued and forfeited, net, under stock plans	6,364		326		6,038
Repurchase of stock-based compensation awards for tax withholdings	(26)				(26)
Ending balance at Sep. 30, 2020	$ 1,122,844	$ 702	$ 675,941	$ 936,344	$ (393,651)	$ (96,492)