Stockholders' Equity - Components of Stockholders' Equity (Detail) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
Beginning Balance	$ 201,502	$ 173,409	$ 185,766	$ 158,088
Issuance of common stock under stock plans, including tax effects	2,023	$ 420	4,493	$ 638
Repurchases of common stock	$ (7,973)		(10,646)
Repurchases of common stock, Shares	(200,000)	0		0
Stock-based compensation expense	$ 2,462	$ 2,697	7,351	$ 7,964
Accounting Standards Update [Extensible List]				ASU No. 2016-13 [Member]
Net income	4,522	(3,760)	16,821	$ 7,564
Net change in interest rate swap, net of tax	128	205	457	(931)
Net change in marketable investments, net of tax	(4)		(4)
Foreign currency translation	(1,508)	2,577	(3,086)	1,542
Ending Balance	201,152	174,708	201,152	174,708
Cumulative Effect, Period of Adoption, Adjustment [Member]
Beginning Balance				(157)
Common Stock [Member]
Beginning Balance	$ 238	$ 234	$ 236	$ 233
Beginning Balance, Shares	23,780,000	23,401,000	23,648,000	23,275,000
Issuance of common stock under stock plans, including tax effects	$ 2		$ 4	$ 3
Issuance of common stock under,stock plans including tax effects, Shares	262,000	178,000	394,000	304,000
Ending Balance	$ 240	$ 236	$ 240	$ 236
Ending Balance, Shares	24,042,000	23,579,000	24,042,000	23,579,000
Additional Paid-in Capital [Member]
Beginning Balance	$ 237,485	$ 222,778	$ 230,128	$ 216,454
Issuance of common stock under stock plans, including tax effects	2,021	422	4,489	635
Stock-based compensation expense	2,462	2,697	7,351	7,964
Ending Balance	241,968	225,053	241,968	225,053
Retained Earnings [Member]
Beginning Balance	140,280	129,314	127,981	118,147
Net income	4,522	(3,760)	16,821	7,564
Ending Balance	144,802	125,554	144,802	125,554
Retained Earnings [Member] | Cumulative Effect, Period of Adoption, Adjustment [Member]
Beginning Balance				(157)
Treasury Stock [Member]
Beginning Balance	$ (174,562)	$ (171,889)	$ (171,889)	$ (171,889)
Beginning Balance, Shares	4,694,000	4,631,000	4,631,000	4,631,000
Repurchases of common stock	$ (7,973)		$ (10,646)
Repurchases of common stock, Shares	(170,000)		(233,000)
Ending Balance	$ (182,535)	$ (171,889)	$ (182,535)	$ (171,889)
Ending Balance, Shares	4,864,000	4,631,000	4,864,000	4,631,000
Accumulated Other Comprehensive Income (Loss) [Member]
Beginning Balance	$ (1,939)	$ (7,028)	$ (690)	$ (4,857)
Net change in interest rate swap, net of tax	128	205	457	(931)
Net change in marketable investments, net of tax	(4)		(4)
Foreign currency translation	(1,508)	2,577	(3,086)	1,542
Ending Balance	$ (3,323)	$ (4,246)	$ (3,323)	$ (4,246)