Cover Page - USD ($)	12 Months Ended
	Oct. 03, 2020	Nov. 25, 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	001-33962
Entity Registrant Name	COHERENT, INC.
Entity Incorporation, State or Country Code	DE
Entity Tax Identification Number	94-1622541
Entity Address, Address Line One	5100 Patrick Henry Drive
Entity Address, City or Town	Santa Clara
Entity Address, State or Province	CA
Entity Address, Postal Zip Code	95054
City Area Code	408
Local Phone Number	764-4000
Title of 12(b) Security	Common Stock, $0.01 par value
Trading Symbol	COHR
Entity Well-known Seasoned Issuer	Yes
Entity Voluntary Filers	No
Entity Current Reporting Status	Yes
Entity Interactive Data Current	Yes
Entity Filer Category	Large Accelerated Filer
Entity Emerging Growth Company	false
Entity Small Business	false
Entity Shell Company	false
Entity Common Stock, Shares Outstanding (shares)		24,439,150
Entity Public Float			$ 1,386,117,559
Entity Central Index Key	0000021510
Amendment Flag	false
Document Fiscal Year Focus	2020
Document Fiscal Period Focus	FY
Current Fiscal Year End Date	--10-03
ICFR Auditor Attestation Flag	true
The NASDAQ Stock Market LLC
Entity Information [Line Items]
Security Exchange Name	NASDAQ
NASDAQ/NGS (GLOBAL SELECT MARKET)
Entity Information [Line Items]
Security Exchange Name	NASDAQ