Consolidated Statements of Stockholders' Equity (unaudited) - USD ($) shares in Thousands, $ in Thousands	Total	Common Stock [Member]	Treasury Stock [Member]	Additional Paid-in Capital [Member]	Accumulated Other Comprehensive Loss [Member]	Retained Earnings [Member]
Beginning Balance at Dec. 31, 2018	$ 986,989	$ 355		$ 323,622	$ (41,653)	$ 704,665
Beginning Balance, Shares at Dec. 31, 2018		35,482
Issuance of common stock under employee stock plans, net of shares withheld for payroll taxes, Value	(6,128)	$ 3		(6,131)
Issuance of common stock under employee stock plans, net of shares withheld for payroll taxes, Shares		279
Stock-based compensation expense	4,115			4,115
Foreign currency translation adjustments, net of tax	1,915				1,915
Net earnings	39,327					39,327
Ending Balance at Mar. 31, 2019	1,026,218	$ 358		321,606	(39,738)	743,992
Ending Balance, Shares at Mar. 31, 2019		35,761
Beginning Balance at Dec. 31, 2019	1,160,318	$ 353		357,032	(38,164)	841,097
Beginning Balance, Shares at Dec. 31, 2019		35,263
Issuance of common stock under employee stock plans, net of shares withheld for payroll taxes, Value	(5,288)	$ 2		(5,289)		(1)
Issuance of common stock under employee stock plans, net of shares withheld for payroll taxes, Shares		(231)
Stock-based compensation expense	4,409			4,409
Repurchase of treasury stock	(25,000)		$ (25,000)
Repurchase of treasury stock, Shares			(445)
Retirement of treasury stock, Amount		$ (5)	$ 25,000	(4,504)		(20,491)
Retirement of treasury stock, Shares		(445)	445
Foreign currency translation adjustments, net of tax	(17,831)				(17,831)
Net earnings	33,961					33,961
Ending Balance at Mar. 31, 2020	$ 1,150,569	$ 350		$ 351,648	$ (55,995)	$ 854,566
Ending Balance, Shares at Mar. 31, 2020		35,049