Stockholders' Equity - Components of Stockholders' Equity (Detail) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Beginning Balance	$ 149,686	$ 140,111	$ 151,600	$ 141,189
Issuance of common stock under stock plans, net	(793)	5,132	3,357	8,708
Cumulative effect adjustment due to adoption of new accounting pronouncements				3,804
Stock-based compensation expense	3,072	2,120	$ 8,605	6,190
Repurchases of common stock		(304)		$ (9,946)
Repurchase of common stock, Shares			0	200,000
Dividends paid on common shares		(3,642)		$ (10,839)
Net income (loss)	(2,699)	3,950	$ (14,460)	10,005
Net change in marketable investments, net of tax		65		12
Foreign currency translation	(1,614)	(602)	(1,450)	(2,293)
Ending Balance	147,652	146,830	147,652	146,830
Common Stock [Member]
Beginning Balance	$ 231	$ 226	$ 230	$ 224
Beginning Balance, Shares	23,089,000	22,564,000	22,951,000	22,432,000
Issuance of common stock under stock plans, net	$ 1	$ 3	$ 2	$ 5
Issuance of common stock under stock plans, net, Shares	158,000	329,000	296,000	461,000
Ending Balance	$ 232	$ 229	$ 232	$ 229
Ending Balance, Shares	23,247,000	22,893,000	23,247,000	22,893,000
Additional Paid-in Capital [Member]
Beginning Balance	$ 210,378	$ 189,554	$ 200,696	$ 181,910
Issuance of common stock under stock plans, net	(794)	5,129	3,355	8,703
Stock-based compensation expense	3,072	2,120	8,605	6,190
Ending Balance	212,656	196,803	212,656	196,803
Retained Earnings [Member]
Beginning Balance	115,956	125,698	127,717	123,010
Cumulative effect adjustment due to adoption of new accounting pronouncements				3,830
Dividends paid on common shares		(3,642)		(10,839)
Net income (loss)	(2,699)	3,950	(14,460)	10,005
Ending Balance	113,257	126,006	113,257	126,006
Treasury Stock [Member]
Beginning Balance	$ (171,889)	$ (171,585)	$ (171,889)	$ (161,943)
Beginning Balance, Shares	4,631,000	4,624,000	4,631,000	4,391,000
Repurchases of common stock		$ (304)		$ (9,946)
Repurchase of common stock, Shares		(7,000)		(240,000)
Ending Balance	$ (171,889)	$ (171,889)	$ (171,889)	$ (171,889)
Ending Balance, Shares	4,631,000	4,631,000	4,631,000	4,631,000
Accumulated Other Comprehensive Income (Loss) [Member]
Beginning Balance	$ (4,990)	$ (3,782)	$ (5,154)	$ (2,012)
Cumulative effect adjustment due to adoption of new accounting pronouncements				(26)
Net change in marketable investments, net of tax		65		12
Foreign currency translation	(1,614)	(602)	(1,450)	(2,293)
Ending Balance	$ (6,604)	$ (4,319)	$ (6,604)	$ (4,319)