Intangible Assets, by Major Class (Details) (USD $)	3 Months Ended		9 Months Ended		0 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2014	Dec. 31, 2013	Apr. 01, 2014	Mar. 31, 2014
Finite-Lived Intangible Assets, Net [Abstract]
Gross Amount	$ 947,700,000		$ 947,700,000			$ 709,190,000
Accumulated Amortization	(396,490,000)		(396,490,000)			(263,691,000)
Net Amount	551,210,000		551,210,000			445,499,000
In-process technology reaching technological feasibility and reclassified			20,700,000
Amortization of Intangible Assets	48,600,000	23,000,000	132,800,000	77,000,000
Impairment of Intangible Assets	1,305,000		1,861,000	350,000
Future Amortization Expense, Remainder of Fiscal Year	48,377,000		48,377,000
Future Amortization Expense, Year Two	146,898,000		146,898,000
Future Amortization Expense, Year Three	91,833,000		91,833,000
Future Amortization Expense, Year Four	69,488,000		69,488,000
Future Amortization Expense, Year Five	62,732,000		62,732,000
Developed technology [Member]
Finite-Lived Intangible Assets, Net [Abstract]
Gross Amount	563,272,000		563,272,000			402,669,000
Accumulated Amortization	(185,391,000)		(185,391,000)			(117,222,000)
Net Amount	377,881,000		377,881,000			285,447,000
Customer-related [Member]
Finite-Lived Intangible Assets, Net [Abstract]
Gross Amount	263,969,000		263,969,000			195,800,000
Accumulated Amortization	(170,719,000)		(170,719,000)			(109,170,000)
Net Amount	93,250,000		93,250,000			86,630,000
Trademarks and trade names [Member]
Finite-Lived Intangible Assets, Net [Abstract]
Gross Amount	15,730,000		15,730,000			15,730,000
Accumulated Amortization	(8,926,000)		(8,926,000)			(7,118,000)
Net Amount	6,804,000		6,804,000			8,612,000
Backlog [Member]
Finite-Lived Intangible Assets, Net [Abstract]
Gross Amount	26,302,000		26,302,000			24,610,000
Accumulated Amortization	(25,818,000)		(25,818,000)			(24,610,000)
Net Amount	484,000		484,000			0
In-process technology [Member]
Finite-Lived Intangible Assets, Net [Abstract]
Gross Amount	72,442,000		72,442,000			64,396,000
Accumulated Amortization	0		0			0
Net Amount	72,442,000		72,442,000			64,396,000
Distribution rights [Member]
Finite-Lived Intangible Assets, Net [Abstract]
Gross Amount	5,585,000		5,585,000			5,585,000
Accumulated Amortization	(5,236,000)		(5,236,000)			(5,171,000)
Net Amount	349,000		349,000			414,000
Covenants not to compete [Member]
Finite-Lived Intangible Assets, Net [Abstract]
Gross Amount	400,000		400,000			400,000
Accumulated Amortization	(400,000)		(400,000)			(400,000)
Net Amount	0		0			0
Minimum [Member]
Finite-Lived Intangible Assets, Net [Abstract]
Useful Life			1 year
Minimum expected useful life of finite lived intangible assets (in years)			1 year
Maximum [Member]
Finite-Lived Intangible Assets, Net [Abstract]
Useful Life			15 years
Minimum expected useful life of finite lived intangible assets (in years)			15 years
Supertex Inc. [Member]
Finite-Lived Intangible Assets, Net [Abstract]
Purchased Intangible Assets					89,600,000
Supertex Inc. [Member] | Developed technology [Member]
Finite-Lived Intangible Assets, Net [Abstract]
Purchased Intangible Assets					68,900,000
Useful Life					10 years
Minimum expected useful life of finite lived intangible assets (in years)					10 years
Supertex Inc. [Member] | Backlog [Member]
Finite-Lived Intangible Assets, Net [Abstract]
Purchased Intangible Assets					1,100,000
Useful Life					1 year
Minimum expected useful life of finite lived intangible assets (in years)					1 year
Cost of Sales [Member]
Finite-Lived Intangible Assets, Net [Abstract]
Amortization of Intangible Assets	900,000	1,200,000	2,900,000	3,700,000
Operating Expense [Member]
Finite-Lived Intangible Assets, Net [Abstract]
Amortization of Intangible Assets	$ 47,700,000	$ 21,800,000	$ 129,900,000	$ 73,300,000