Components of Net Deferred Taxes (Detail) (USD $) In Thousands, unless otherwise specified	Mar. 31, 2013	Mar. 31, 2012
Deferred tax assets
NOL carryforwards and tax credit carryforwards	$ 88,304	$ 84,831
Stock-based compensation	6,825	7,500
Capitalized research and development	5,366	8,040
Foreign NOL carryforwards	4,777	5,405
Nondeductible reserves and accruals	4,811	4,579
Amortizable intangibles other than goodwill	4,138	4,600
Deferred revenue	1,567	1,132
Depreciation	388	580
Change in unrealized losses on marketable securities	285	285
Other, net	1,488	1,327
Deferred Tax Assets, Gross, Total	117,949	118,279
Deferred tax liabilities
Indefinite lived intangibles	(5,554)	(4,799)
Deferred Tax Liabilities, Net	(5,554)	(4,799)
Net deferred tax asset	112,395	113,480
Valuation allowance	(117,949)	(118,279)
Net deferred tax liability	$ (5,554)	$ (4,799)