Consolidated Statements of Changes in Stockholders' Equity - USD ($) $ in Thousands	Total	Common Stock Voting [Member]	Additional Paid-In Capital [Member]	Treasury Stock - Common Stock Voting [Member]	Retained Earnings [Member]	Accumulated Other Comprehensive Loss [Member]
Beginning Balance at Dec. 31, 2019	$ 770,091	$ 122	$ 342,541	$ (153,388)	$ 591,086	$ (10,270)
Net income	74,816				74,816
Cumulative translation adjustment and foreign currency exchange hedge, net of tax	(3,859)					(3,859)
Unrealized net loss on securities available-for-sale, net of tax	(491)					(491)
Stock-based compensation	6,677		6,677
Exercise of stock options	80		80
Withholding tax payments on restricted stock vesting and stock option exercises	(21,243)		(21,243)
Repurchases of common stock	(5,415)			(5,415)
Cash dividend on common stock	(22,773)				(22,773)
Ending Balance at Mar. 31, 2020	797,883	122	328,055	(158,803)	643,129	(14,620)
Beginning Balance at Dec. 31, 2020	955,061	123	329,742	(169,523)	799,369	(4,650)
Net income	80,457				80,457
Cumulative translation adjustment and foreign currency exchange hedge, net of tax	(1,932)					(1,932)
Stock-based compensation	7,424		7,424
Exercise of stock options	244		244
Withholding tax payments on restricted stock vesting and stock option exercises	(27,422)		(27,422)
Repurchases of common stock	(520)			(520)
Cash dividend on common stock	(25,079)				(25,079)
Ending Balance at Mar. 31, 2021	$ 988,233	$ 123	$ 309,988	$ (170,043)	$ 854,747	$ (6,582)