Business Acquisitions (Narrative) (Details) - USD ($) shares in Millions, $ in Millions			12 Months Ended
	Apr. 04, 2016	Aug. 03, 2015	Mar. 31, 2017	Mar. 31, 2016
Business Acquisition [Line Items]
Non-cash consideration, exchange of employee stock awards (amount)			$ 7.5	$ 4.1
Atmel Corporation
Business Acquisition [Line Items]
Cash paid for shares	$ 2,980.0
Shares issued in acquisition	10.1
Equity interest issued or issuable, value assigned	$ 486.1
Separately recognized transactions, expenses and losses recognized	14.9
Consideration transferred, share based payment awards	7.5
Total consideration transferred	3,470.0
Recognized identifiable assets acquired and liabilities assumed, liabilities	653.0
Payments to acquire businesses portion funded by foreign subsidiaries cash balances	2,040.0
Payments to acquire businesses portion funded by additional line of credit borrowings	$ 940.0
Useful life (in years)	9 years
Net deferred tax liability for future amortization expense of acquired intangible assets	$ 178.1
Long-term deferred tax assets	$ 46.7
Micrel Incorporated
Business Acquisition [Line Items]
Cash paid for shares		$ 430.0
Shares issued in acquisition		8.6
Non-cash consideration, exchange of employee stock awards (amount)		$ 4.1
Total consideration transferred		816.2
Recognized identifiable assets acquired and liabilities assumed, liabilities		138.4
Net deferred tax liability for future amortization expense of acquired intangible assets		99.7
Cash paid in a business combination for employee vested stock awards		13.1
Long-term deferred tax assets		$ 11.4