Business Acquisitions (Schedule of Purchase Price Allocation) (Details) - USD ($) $ in Thousands	3 Months Ended
	Jun. 30, 2015	Sep. 30, 2015	Aug. 03, 2015	Mar. 31, 2015
Business Acquisition [Line Items]
Goodwill		$ 1,008,720		$ 571,271
Micrel Incorporated [Member]
Business Acquisition [Line Items]
Cash and cash equivalents			$ 99,196
Accounts receivable, net			12,296
Inventories			78,967
Prepaid expenses and other current assets			10,548
Property, plant and equipment, net			38,566
Goodwill			437,060
Purchased intangible assets			274,800
Other assets			4,268
Total assets acquired			955,701
Accounts payable			(11,068)
Other current liabilities			(30,241)
Long-term income tax payable			(9,239)
Deferred tax liability			(88,796)
Other long-term liabilities			(127)
Total liabilities assumed			(139,471)
Net assets acquired			$ 816,230
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