Business Acquisitions (Narrative) (Details) - USD ($) $ / shares in Units, $ in Thousands		2 Months Ended	6 Months Ended
	Aug. 03, 2015	Sep. 30, 2015	Sep. 30, 2015	Sep. 30, 2014	Jul. 17, 2014
Business Acquisition [Line Items]
Amount of cash paid, net of cash and short-term investments acquired			$ 343,928	$ 0
Micrel Incorporated [Member]
Business Acquisition [Line Items]
Tendered offer price per share	$ 14.00
Cash paid for shares	$ 430,000
Shares issued in Micrel acquisition	8,626,795
Non cash consideration of certain share-based payment awards	$ 4,100
Cash paid in a business combination for employee vested stock awards	13,100
Total consideration transferred	816,200
Net deferred tax liability for future amortization expense of acquired intangible assets	99,800
Net deferred tax assets acquired in a business combination	$ 11,000
Revenue of acquiree included in statement of income since the acquisition date		$ 21,500
Net income (loss) of acquiree included in statement of income since the acquisition date		$ (28,500)
ISSC Technologies Corporation [Member]
Business Acquisition [Line Items]
Ownership interest acquired in ISSC tender offer					83.50%