Stockholders' Equity - Components of Stockholders' Equity (Detail) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018
Beginning Balance	$ 143,814	$ 141,295	$ 151,600	$ 141,189
Issuance of common stock under stock plans, net	875	1,112	4,150	3,575
Cumulative effect adjustment due to adoption of new accounting pronouncements				3,803
Stock-based compensation expense	2,848	2,108	$ 5,533	4,071
Repurchases of common stock		$ (5,275)		$ (9,642)
Repurchase of common stock, Shares		100,000	0	200,000
Dividends paid on common shares		$ (3,585)		$ (7,196)
Net income (loss)	1,555	7,788	$ (11,761)	6,055
Net change in marketable investments, net of tax		62		(53)
Foreign currency translation	594	(3,394)	164	(1,691)
Ending Balance	149,686	140,111	149,686	140,111
Common Stock [Member]
Beginning Balance	$ 231	$ 225	$ 230	$ 224
Beginning Balance, Shares	23,050,000	22,514,000	22,951,000	22,432,000
Issuance of common stock under stock plans, net		$ 1	$ 1	$ 2
Issuance of common stock under stock plans, net, Shares	39,000	50,000	138,000	132,000
Ending Balance	$ 231	$ 226	$ 231	$ 226
Ending Balance, Shares	23,089,000	22,564,000	23,089,000	22,564,000
Additional Paid-in Capital [Member]
Beginning Balance	$ 206,655	$ 186,335	$ 200,696	$ 181,910
Issuance of common stock under stock plans, net	875	1,111	4,149	3,573
Stock-based compensation expense	2,848	2,108	5,533	4,071
Ending Balance	210,378	189,554	210,378	189,554
Retained Earnings [Member]
Beginning Balance	114,401	121,495	127,717	123,010
Cumulative effect adjustment due to adoption of new accounting pronouncements				3,829
Dividends paid on common shares		(3,585)		(7,196)
Net income (loss)	1,555	7,788	(11,761)	6,055
Ending Balance	115,956	125,698	115,956	125,698
Treasury Stock [Member]
Beginning Balance	$ (171,889)	$ (166,310)	$ (171,889)	$ (161,943)
Beginning Balance, Shares	4,631,000	4,497,000	4,631,000	4,391,000
Repurchases of common stock		$ (5,275)		$ (9,642)
Repurchase of common stock, Shares		(127,000)		(233,000)
Ending Balance	$ (171,889)	$ (171,585)	$ (171,889)	$ (171,585)
Ending Balance, Shares	4,631,000	4,624,000	4,631,000	4,624,000
Accumulated Other Comprehensive Income (Loss) [Member]
Beginning Balance	$ (5,584)	$ (450)	$ (5,154)	$ (2,012)
Cumulative effect adjustment due to adoption of new accounting pronouncements				(26)
Net change in marketable investments, net of tax		62		(53)
Foreign currency translation	594	(3,394)	164	(1,691)
Ending Balance	$ (4,990)	$ (3,782)	$ (4,990)	$ (3,782)