Business Acquisitions (Schedule of Proforma Information) (Details) (USD $) In Thousands, except Per Share data, unless otherwise specified	3 Months Ended	6 Months Ended
Sep. 30, 2014	Sep. 30, 2013	Sep. 30, 2014	Sep. 30, 2013
ISSC Technologies Corporation [Member]
Business Acquisition [Line Items]
Net sales	$ 547,543	$ 512,150	$ 1,097,473	$ 993,191
Net income	95,261	92,527	178,729	161,602
Basic earnings per share	$ 0.47	$ 0.47	$ 0.89	$ 0.82
Diluted earnings per share	$ 0.42	$ 0.43	$ 0.79	$ 0.75
Supertex Inc.
Business Acquisition [Line Items]
Net sales	546,243	510,418	1,077,588	986,939
Net income	$ 98,391	$ 91,271	$ 203,896	$ 152,235
Basic earnings per share	$ 0.49	$ 0.46	$ 1.02	$ 0.77
Diluted earnings per share	$ 0.44	$ 0.42	$ 0.91	$ 0.71

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The pro forma basic net income per share for a period as if the business combination or combinations had been completed at the beginning of a period.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 805

-SubTopic 10

-Section 50

-Paragraph 2

-Subparagraph (h)(2)-(3)

-URI http://asc.fasb.org/extlink&oid=25497992&loc=d3e1392-128463

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The pro forma diluted net income per share for a period as if the business combination or combinations had been completed at the beginning of a period.

+ References

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The pro forma net Income or Loss for the period as if the business combination or combinations had been completed at the beginning of a period.

+ References

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The pro forma revenue for a period as if the business combination or combinations had been completed at the beginning of the period.

+ References

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