Document and Entity Information - USD ($)	12 Months Ended
	Jun. 30, 2017	Aug. 14, 2017	Dec. 30, 2016
Document And Entity Information [Abstract]
Document Type	10-K
Amendment Flag	false
Document Period End Date	Jun. 30, 2017
Document Fiscal Year Focus	2017
Document Fiscal Period Focus	FY
Trading Symbol	IIVI
Entity Registrant Name	II-VI INC
Entity Central Index Key	0000820318
Current Fiscal Year End Date	--06-30
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		63,279,520
Entity Public Float			$ 1,763,329,797