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, 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, Amount	(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
Beginning Balance at Dec. 31, 2020	1,342,429	$ 351		364,288	(15,455)	993,245
Beginning Balance, Shares at Dec. 31, 2020		35,103
Issuance of common stock under employee stock plans, net of shares withheld for payroll taxes, Value	(7,067)	$ 2		(7,069)
Issuance of common stock under employee stock plans, net of shares withheld for payroll taxes, Shares		217
Stock-based compensation expense	4,716			4,716
Foreign currency translation adjustments, net of tax	(80)				(80)
Net earnings	43,168					43,168
Ending Balance at Mar. 31, 2021	$ 1,383,166	$ 353		$ 361,935	$ (15,535)	$ 1,036,413
Ending Balance, Shares at Mar. 31, 2021		35,320