Goodwill and Intangible Assets - Additional Information (Detail) (USD $)	12 Months Ended
	Mar. 31, 2013	Mar. 31, 2012	Mar. 31, 2011
Acquired Finite-Lived Intangible Assets [Line Items]
Goodwill	$ 202,453,000	$ 170,384,000	$ 128,177,000
Intangible assets, net	63,827,000	54,685,000
Amortization expenses	2,877,000	2,131,000	1,907,000
Weighted average useful life in years of acquired intangible assets	10 years 1 month 6 days
Indefinite Lived Trade Name
Acquired Finite-Lived Intangible Assets [Line Items]
Indefinite lived intangible	18,600,000	18,600,000
Acquired Software And Core Technology
Acquired Finite-Lived Intangible Assets [Line Items]
Weighted average useful life in years of acquired intangible assets	6 years 8 months 12 days
Acquired Software And Core Technology | Included As Cost Of Product Revenue
Acquired Finite-Lived Intangible Assets [Line Items]
Amortization expenses	4,500,000	4,700,000	4,000,000
Other Acquired Intangible Assets | Included As Operating Expense
Acquired Finite-Lived Intangible Assets [Line Items]
Amortization expenses	3,100,000	2,200,000	1,900,000
Customer Relationships
Acquired Finite-Lived Intangible Assets [Line Items]
Weighted average useful life in years of acquired intangible assets	13 years 3 months 18 days
Unified Service Delivery
Acquired Finite-Lived Intangible Assets [Line Items]
Goodwill	199,500,000	170,400,000
Test Automation
Acquired Finite-Lived Intangible Assets [Line Items]
Goodwill	$ 3,000,000	$ 0