Goodwill & Intangible Assets (Narrative) (Details) (USD $)	12 Months Ended
	Mar. 31, 2012 Y	Mar. 31, 2011	Mar. 31, 2010
Acquired Finite-Lived Intangible Assets [Line Items]
Goodwill	$ 170,384,000	$ 128,177,000	$ 128,177,000
Weighted average useful life in years of acquired intangible assets	10.8
Acquired Software And Core Technology [Member]
Acquired Finite-Lived Intangible Assets [Line Items]
Amortization expenses included in cost of product	4,700,000	4,000,000	4,000,000
Weighted average useful life in years of acquired intangible assets	6.3
Other Acquired Intangible Assets [Member]
Acquired Finite-Lived Intangible Assets [Line Items]
Amortization expenses included in cost of product	2,200,000	1,900,000	2,100,000
Customer Relationships [Member]
Acquired Finite-Lived Intangible Assets [Line Items]
Weighted average useful life in years of acquired intangible assets	15.2
Indefinite Lived Trade Name [Member]
Acquired Finite-Lived Intangible Assets [Line Items]
Intangible assets, net	$ 18,600,000	$ 18,600,000