Goodwill and Intangible Assets - Additional Information (Detail) (USD $) In Thousands, unless otherwise specified	3 Months Ended		6 Months Ended
	Sep. 30, 2012	Sep. 30, 2011	Sep. 30, 2012	Sep. 30, 2011	Jun. 30, 2012	Mar. 31, 2012
Acquired Finite-Lived Intangible Assets [Line Items]
Goodwill	$ 181,299		$ 181,299		$ 169,522	$ 170,384
Intangible assets, net	56,066		56,066			54,685
Amortization expenses included in cost of product	645	494	1,231	976
Weighted average useful life in years of acquired intangible assets			10 years 6 months
Acquired Software And Core Technology
Acquired Finite-Lived Intangible Assets [Line Items]
Amortization expenses included in cost of product	1,500	1,100	2,900	2,200
Weighted average useful life in years of acquired intangible assets			6 years 6 months
Other Acquired Intangible Assets
Acquired Finite-Lived Intangible Assets [Line Items]
Amortization expenses included in cost of product	$ 674	$ 521	$ 1,300	$ 976
Customer Relationships
Acquired Finite-Lived Intangible Assets [Line Items]
Weighted average useful life in years of acquired intangible assets			14 years 4 months 24 days