Consolidated Statement of Shareholders' Equity - USD ($) shares in Thousands, $ in Thousands	Total	Cumulative Effect, Period of Adoption, Adjustment [Member]	Common Stock [Member]	Additional Paid-in Capital [Member]	Retained Earnings [Member]	Retained Earnings [Member] Cumulative Effect, Period of Adoption, Adjustment [Member]	Treasury Stock [Member]	Accumulated Other Comprehensive Income (Loss) [Member]
Beginning Balance at Dec. 31, 2019	$ 158,088		$ 233	$ 216,454	$ 118,147		$ (171,889)	$ (4,857)
Beginning Balance, Shares at Dec. 31, 2019			23,275				4,631
Issuance of common stock under stock plans, including tax effects	2,800		$ 3	2,797
Issuance of common stock under stock plans, including tax effects, Shares			373
Stock-based compensation expense	10,877			10,877
Net income	9,990				9,990
Net change in interest rate swap, net of tax	(717)							(717)
Foreign currency translation	4,884							4,884
Ending Balance at Dec. 31, 2020	185,766		$ 236	230,128	127,981		$ (171,889)	(690)
Ending Balance (ASU No. 2016-13 [Member]) at Dec. 31, 2020		$ (156)				$ (156)
Ending Balance, Shares at Dec. 31, 2020			23,648				4,631
Issuance of common stock under stock plans, including tax effects	5,792		$ 5	5,787
Issuance of common stock under stock plans, including tax effects, Shares			437
Repurchases of common stock	(20,066)						$ (20,066)
Repurchase of common stock, Shares							396
Stock-based compensation expense	10,070			10,070
Net income	24,844				24,844
Net change in interest rate swap, net of tax								609
Net change in interest rate swap, net of tax | ASU No. 2016-13 [Member]		$ 609
Net change in marketable investments, net of tax	(25)							(25)
Foreign currency translation	(3,083)							(3,083)
Ending Balance at Dec. 31, 2021	203,907		$ 241	245,985	152,825		$ (191,955)	(3,189)
Ending Balance, Shares at Dec. 31, 2021			24,085				5,027
Issuance of common stock under stock plans, including tax effects	1,241		$ 3	1,238
Issuance of common stock under stock plans, including tax effects, Shares			282
Repurchases of common stock	(15,112)						$ (15,112)
Repurchase of common stock, Shares							278
Stock-based compensation expense	14,543			14,543
Net income	21,806				21,806
Net change in interest rate swap, net of tax	212							212
Net change in marketable investments, net of tax	(134)							(134)
Foreign currency translation	(4,807)							(4,807)
Ending Balance at Dec. 31, 2022	$ 221,656		$ 244	$ 261,766	$ 174,631		$ (207,067)	$ (7,918)
Ending Balance, Shares at Dec. 31, 2022			24,367				5,305