Document And Entity Information - USD ($) $ in Billions	12 Months Ended
	Oct. 03, 2020	Nov. 16, 2020	Apr. 04, 2020
Entity Information [Line Items]
Document Type	10-K
Document Annual Report	true
Document Period End Date	Oct. 03, 2020
Document Transition Report	false
Entity File Number	001-14423
Entity Registrant Name	PLEXUS CORP.
Entity Incorporation, State or Country Code	WI
Entity Tax Identification Number	39-1344447
Entity Address, Address Line One	One Plexus Way
Entity Address, City or Town	Neenah
Entity Address, State or Province	WI
Entity Address, Postal Zip Code	54957
City Area Code	920
Local Phone Number	969-6000
Title of 12(b) Security	Common Stock, $0.01 par value
Trading Symbol	PLXS
Security Exchange Name	NASDAQ
Entity Well-Known Season Issuer	Yes
Entity Voluntary Filers	No
Entity Current Reporting Status	Yes
Entity Interactive Data Current	Yes
Entity Filer Category	Large Accelerated Filer
Entity Small Business	false
Entity Emerging Growth Company	false
ICFR Auditor Attestation Flag	true
Entity Shell Company	false
Entity Public Float			$ 1.4
Entity Common Stock, Shares Outstanding		28,823,390
Documents Incorporated by Reference [Text Block]	Parts of Registrant’s Proxy Statement for the 2021 Annual Meeting of Shareholders are incorporated by reference into Part III of this Report.
Entity Central Index Key	0000785786
Current Fiscal Year End Date	--10-03
Document Fiscal Year Focus	2020
Document Fiscal Period Focus	FY
Amendment Flag	false