Subsequent Events Subsequent Events (Details)	12 Months Ended			0 Months Ended
	Mar. 31, 2014 USD ($)	Mar. 31, 2013 USD ($)	Mar. 31, 2012 USD ($)	Apr. 01, 2014 Subsequent Event Supertex Inc. USD ($)	May 22, 2014 Subsequent Event ISSC Technologies Corporation USD ($)	May 22, 2014 Subsequent Event ISSC Technologies Corporation TWD
Subsequent Event [Line Items]
Acquisition price per share				$ 33.00	$ 4.74	143.00
Cash and short term investments acquired				$ 155,800,000	$ 34,200,000	1,000,000,000
Amount of cash paid net of cash acquired	11,187,000	20,556,000	38,580,000	234,200,000
Assumed exchange rate					30.15
Total equity value					328,500,000	9,900,000,000
Total enterprise value					$ 294,300,000	8,900,000,000