Document and Entity Information - shares	6 Months Ended
	Dec. 31, 2017	Feb. 02, 2018
Document And Entity Information [Abstract]
Document Type	10-Q
Amendment Flag	false
Document Period End Date	Dec. 31, 2017
Document Fiscal Year Focus	2018
Document Fiscal Period Focus	Q2
Trading Symbol	IIVI
Entity Registrant Name	II-VI INC
Entity Central Index Key	0000820318
Current Fiscal Year End Date	--06-30
Entity Filer Category	Large Accelerated Filer
Entity Common Stock, Shares Outstanding		62,486,560