Business Acquisitions (Schedule of Purchase Price Allocation) (Details) - USD ($) $ in Thousands	3 Months Ended
	Jun. 30, 2015	Mar. 31, 2015
Business Acquisition [Line Items]
Goodwill	$ 571,660	$ 571,271
ISSC Technologies Corporation [Member]
Business Acquisition [Line Items]
Cash and cash equivalents	15,120	15,120
Short-term investments	27,063	27,063
Accounts receivable, net	8,792	8,792
Inventories	16,542	16,542
Prepaid expenses and other current assets	2,501	2,501
Property, plant and equipment, net	2,637	2,637
Goodwill	154,788	154,399
Purchased intangible assets	147,800	147,800
Other assets	1,370	1,370
Total assets acquired	376,613	376,224
Accounts payable	(9,860)	(9,860)
Other current liabilities	(16,535)	(16,535)
Long-term income tax payable	(4,791)	(4,402)
Deferred tax liability	(25,126)	(25,126)
Other long-term liabilities	(245)	(245)
Total liabilities assumed	(56,557)	(56,168)
Net assets acquired	320,056	320,056
Less: noncontrolling interest	(52,467)	(52,467)
Net assets acquired	267,589	267,589
Business Combination, Provisional Information, Initial Accounting Incomplete, Adjustments [Abstract]
Goodwill	389
Total assets acquired	389
Long-term income tax payable	(389)
Total liabilities assumed	$ (389)
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		2,456
Other current assets		12,625
Property, plant and equipment, net		15,679
Goodwill		143,160
Purchased intangible assets		89,600
Other assets		325
Total assets acquired		455,789
Accounts payable		(8,481)
Other current liabilities		(19,224)
Long-term income tax payable		(3,796)
Deferred tax liability		(32,511)
Total liabilities assumed		(64,012)
Net assets acquired		$ 391,777