Document and Entity Information - shares	6 Months Ended
	Dec. 31, 2019	Feb. 06, 2020
Cover [Abstract]
Document Type	10-Q
Amendment Flag	false
Document Period End Date	Dec. 31, 2019
Document Fiscal Year Focus	2020
Document Fiscal Period Focus	Q2
Trading Symbol	IIVI
Entity Registrant Name	II-VI INCORPORATED
Entity Central Index Key	0000820318
Entity Current Reporting Status	Yes
Current Fiscal Year End Date	--06-30
Entity Filer Category	Large Accelerated Filer
Entity Small Business	false
Entity Emerging Growth Company	false
Entity Common Stock, Shares Outstanding		91,059,636
Entity Shell Company	false
Entity File Number	0-16195
Entity Tax Identification Number	25-1214948
Entity Address, Address Line One	375 Saxonburg Boulevard
Entity Address, City or Town	Saxonburg
Entity Address, State or Province	PA
Entity Address, Postal Zip Code	16056
City Area Code	724
Entity Interactive Data Current	Yes
Local Phone Number	352-4455
Title of 12(b) Security	Common Stock, no par value
Security Exchange Name	NASDAQ
Entity Incorporation, State or Country Code	PA
Document Quarterly Report	true
Document Transition Report	false