Document and Entity Information - USD ($) $ in Thousands	12 Months Ended
	Oct. 01, 2017	Nov. 09, 2017	Mar. 31, 2017
Document and Entity Information [Abstract]
Document Type	10-K
Amendment Flag	false
Document Period End Date	Oct. 01, 2017
Document Fiscal Year Focus	2017
Document Fiscal Period Focus	FY
Trading Symbol	MSCC
Entity Registrant Name	MICROSEMI CORP
Entity Central Index Key	0000310568
Current Fiscal Year End Date	--10-01
Entity Well-known Seasoned Issuer	Yes
Entity Current Reporting Status	Yes
Entity Voluntary Filers	No
Entity Filer Category	Large Accelerated Filer
Entity Common Stock, Shares Outstanding		117,594,115
Entity Public Float			$ 5,950,000