Intangible Assets, by Major Class (Details) (USD $)	12 Months Ended
	Mar. 31, 2015	Mar. 31, 2014	Mar. 31, 2013
Finite-Lived Intangible Assets [Line Items]
Gross Amount	$ 949,067,000	$ 709,190,000
Accumulated Amortization	(444,650,000)	(263,691,000)
Net Amount	504,417,000	445,499,000
In-process technology reaching technological feasibility and reclassified	26,000,000
Projected Amortization Expense
2016	144,229,000
2017	92,642,000
2018	69,428,000
2019	56,577,000
2020	40,718,000
Amortization of acquired intangible assets	181,000,000	99,400,000	115,800,000
Impairment of intangible assets	1,881,000	350,000	0
Cost of sales [Member]
Projected Amortization Expense
Amortization of acquired intangible assets	3,800,000	4,700,000	3,900,000
Operating Expense [Member]
Projected Amortization Expense
Amortization of acquired intangible assets	177,200,000	94,700,000	111,900,000
Minimum [Member]
Finite-Lived Intangible Assets [Line Items]
Finite-Lived Intangible Asset, Useful Life	1 year
Maximum [Member]
Finite-Lived Intangible Assets [Line Items]
Finite-Lived Intangible Asset, Useful Life	15 years
Developed Technology [Member]
Finite-Lived Intangible Assets [Line Items]
Gross Amount	569,942,000	402,669,000
Accumulated Amortization	(209,676,000)	(117,222,000)
Net Amount	360,266,000	285,447,000
Acquired Finite-lived Intangible Asset, Amount	144,700,000
Acquired Finite-lived Intangible Assets, Weighted Average Useful Life	9 years
Customer Relationships [Member]
Finite-Lived Intangible Assets [Line Items]
Gross Amount	263,969,000	195,800,000
Accumulated Amortization	(193,483,000)	(109,170,000)
Net Amount	70,486,000	86,630,000
Acquired Finite-lived Intangible Asset, Amount	68,800,000
Acquired Finite-lived Intangible Assets, Weighted Average Useful Life	2 years 6 months
Trademarks and trade names [Member]
Finite-Lived Intangible Assets [Line Items]
Gross Amount	15,730,000	15,730,000
Accumulated Amortization	(9,529,000)	(7,118,000)
Net Amount	6,201,000	8,612,000
Backlog [Member]
Finite-Lived Intangible Assets [Line Items]
Gross Amount	26,304,000	24,610,000
Accumulated Amortization	(26,304,000)	(24,610,000)
Net Amount	0	0
Acquired Finite-lived Intangible Asset, Amount	1,700,000
Acquired Finite-lived Intangible Assets, Weighted Average Useful Life	1 year
In-process technology [Member]
Finite-Lived Intangible Assets [Line Items]
Gross Amount	67,142,000	64,396,000
Accumulated Amortization	0	0
Net Amount	67,142,000	64,396,000
Acquired Finite-lived Intangible Asset, Amount	29,100,000
Distribution rights [Member]
Finite-Lived Intangible Assets [Line Items]
Gross Amount	5,580,000	5,585,000
Accumulated Amortization	(5,258,000)	(5,171,000)
Net Amount	322,000	414,000
Covenants not to compete [Member]
Finite-Lived Intangible Assets [Line Items]
Gross Amount	400,000	400,000
Accumulated Amortization	(400,000)	(400,000)
Net Amount	$ 0	$ 0