Intangible Assets, by Major Class (Details) (USD $)	3 Months Ended		6 Months Ended																	3 Months Ended		0 Months Ended			3 Months Ended		6 Months Ended		3 Months Ended		6 Months Ended
	Sep. 30, 2014	Sep. 30, 2013	Sep. 30, 2014	Sep. 30, 2013	Mar. 31, 2014	Sep. 30, 2014 Core/developed technology	Mar. 31, 2014 Core/developed technology	Sep. 30, 2014 Customer Relationships [Member]	Mar. 31, 2014 Customer Relationships [Member]	Sep. 30, 2014 Trademarks and trade names [Member]	Mar. 31, 2014 Trademarks and trade names [Member]	Sep. 30, 2014 Backlog [Member]	Mar. 31, 2014 Backlog [Member]	Sep. 30, 2014 In-process technology [Member]	Mar. 31, 2014 In-process technology [Member]	Sep. 30, 2014 Distribution rights [Member]	Mar. 31, 2014 Distribution rights [Member]	Sep. 30, 2014 Covenants not to compete [Member]	Mar. 31, 2014 Covenants not to compete [Member]	Sep. 30, 2014 Minimum [Member]	Sep. 30, 2014 Maximum [Member]	Apr. 01, 2014 Supertex Inc. [Member]	Apr. 01, 2014 Supertex Inc. [Member] Core/developed technology	Apr. 01, 2014 Supertex Inc. [Member] Backlog [Member]	Sep. 30, 2014 Cost of Sales [Member]	Sep. 30, 2013 Cost of Sales [Member]	Sep. 30, 2014 Cost of Sales [Member]	Sep. 30, 2013 Cost of Sales [Member]	Sep. 30, 2014 Operating Expense [Member]	Sep. 30, 2013 Operating Expense [Member]	Sep. 30, 2014 Operating Expense [Member]	Sep. 30, 2013 Operating Expense [Member]
Finite-Lived Intangible Assets, Net [Abstract]
Gross Amount	$ 946,930,000		$ 946,930,000		$ 709,190,000	$ 559,828,000	$ 402,669,000	$ 263,805,000	$ 195,800,000	$ 15,730,000	$ 15,730,000	$ 26,302,000	$ 24,610,000	$ 75,280,000	$ 64,396,000	$ 5,585,000	$ 5,585,000	$ 400,000	$ 400,000
Accumulated Amortization	(347,905,000)		(347,905,000)		(263,691,000)	(161,145,000)	(117,222,000)	(147,489,000)	(109,170,000)	(8,323,000)	(7,118,000)	(25,331,000)	(24,610,000)	0	0	(5,217,000)	(5,171,000)	(400,000)	(400,000)
Net Amount	599,025,000		599,025,000		445,499,000	398,683,000	285,447,000	116,316,000	86,630,000	7,407,000	8,612,000	971,000	0	75,280,000	64,396,000	368,000	414,000	0	0
In-process technology reaching technological feasibility and reclassified			24,400,000
Purchased Intangible Assets																						89,600,000	68,900,000	1,100,000
Useful Life																				1 year	15 years		10 years	1 year
Minimum expected useful life of finite lived intangible assets (in years)																				1 year	15 years		10 years	1 year
Amortization of Intangible Assets	46,500,000	25,100,000	84,200,000	54,000,000																					1,000,000	1,300,000	2,000,000	2,500,000	45,500,000	23,800,000	82,200,000	51,500,000
Impairment of Intangible Assets	150,000		556,000	350,000
Future Amortization Expense, Remainder of Fiscal Year	99,063,000		99,063,000
Future Amortization Expense, Year Two	150,298,000		150,298,000
Future Amortization Expense, Year Three	92,227,000		92,227,000
Future Amortization Expense, Year Four	73,926,000		73,926,000
Future Amortization Expense, Year Five	$ 65,650,000		$ 65,650,000