Business Acquisitions (Schedule of Preliminary Allocation of Purchase Price) (Details) (USD $) In Thousands, unless otherwise specified	Jun. 30, 2014	Mar. 31, 2014	Apr. 01, 2014 Supertex Inc.
Business Acquisition [Line Items]
Cash and cash equivalents			$ 14,790
Short-term investments			140,984
Accounts receivable, net			7,047
Inventories			27,630
Prepaid expenses			1,493
Deferred tax assets			3,997
Other current assets			16,113
Property, plant and equipment, net			15,679
Goodwill	409,885	276,097	133,713
Purchased intangible assets			89,600
Other assets			325
Total assets acquired			451,371
Accounts payable			(8,481)
Accrued liabilities			(19,345)
Long-term income tax payable			(3,796)
Deferred tax liability			(27,972)
Total liabilities assumed			(59,594)
Purchase price allocated			$ 391,777