Adjustments to additional paid in capital, debt issued, issuance costs.

No definition available.

Name:	iivi_AdjustmentsToAdditionalPaidInCapitalDebtIssuedIssuanceCosts
Namespace Prefix:	iivi_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

Debt instrument month and year of maturity.

+ References

No definition available.

+ Details

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Namespace Prefix:	iivi_
Data Type:	xbrli:gYearMonthItemType
Balance Type:	na
Period Type:	duration

- Definition

Debt instrument principal amount denomination for conversion into common stock.

+ References

No definition available.

+ Details

Name:	iivi_DebtInstrumentPrincipalAmountDenominationForConversionIntoCommonStock
Namespace Prefix:	iivi_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

Option to purchase additional debt instrument granted days.

+ References

No definition available.

+ Details

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Namespace Prefix:	iivi_
Data Type:	xbrli:durationItemType
Balance Type:	na
Period Type:	duration

- Definition

Percentage points added to the reference rate to compute the variable rate on the debt instrument.

+ References

No definition available.

+ Details

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Namespace Prefix:	us-gaap_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

The price per share of the conversion feature embedded in the debt instrument.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 470
-SubTopic 20
-Section 50
-Paragraph 5
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=109500613&loc=SL6031898-161870

+ Details

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Data Type:	num:perShareItemType
Balance Type:	na
Period Type:	instant

- Definition

Ratio applied to the conversion of debt instrument into equity with equity shares divided by debt principal amount.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
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-SubTopic 10
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-Paragraph 7
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-Paragraph 6
-Subparagraph (b)
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-Name Accounting Standards Codification
-Topic 210
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Balance Type:	na
Period Type:	duration

- Definition

The amount by which the convertible debt's if-converted value exceeds its principle amount at the balance sheet date, regardless of whether the instrument is currently convertible. This element applies to public companies only.

+ References

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-Name Accounting Standards Codification
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-SubTopic 20
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-Paragraph 5
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Balance Type:	credit
Period Type:	duration

- Definition

Remaining amortization period for discount on the liability component of convertible debt which may be settled in cash upon conversion, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

+ References

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-SubTopic 20
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Data Type:	xbrli:durationItemType
Balance Type:	na
Period Type:	duration

- Definition

Face (par) amount of debt instrument at time of issuance.

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-Name Accounting Standards Codification
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Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Effective interest rate for the funds borrowed under the debt agreement considering interest compounding and original issue discount or premium.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 470
-SubTopic 20
-Section 50
-Paragraph 6
-Subparagraph (a)
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-Paragraph 1
-Subparagraph (SX 210.5-02.22(a)(1))
-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

+ Details

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Namespace Prefix:	us-gaap_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	instant

- Definition

Contractual interest rate for funds borrowed, under the debt agreement.

+ References

+ Details

Name:	us-gaap_DebtInstrumentInterestRateStatedPercentage
Namespace Prefix:	us-gaap_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	instant

- Definition

Date when the debt instrument is scheduled to be fully repaid, in CCYY-MM-DD format.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02.22(a)(2))
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-Name Accounting Standards Codification
-Topic 820
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (bbb)(2)
-URI http://asc.fasb.org/extlink&oid=99377789&loc=d3e19207-110258

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Data Type:	xbrli:dateItemType
Balance Type:	na
Period Type:	duration

- Definition

Amount, after accumulated amortization, of debt discount.

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-Publisher FASB
-Name Accounting Standards Codification
-Topic 835
-SubTopic 30
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-Paragraph 1A
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-Topic 835
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Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

Weighted average interest rate of debt outstanding.

+ References

No definition available.

+ Details

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Namespace Prefix:	us-gaap_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	instant

- Definition

The total amount of the contingent obligation under letters of credit outstanding as of the reporting date.

+ References

No definition available.

+ Details

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Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

The carrying value as of the balance sheet date of the current and noncurrent portions of long-term obligations drawn from a line of credit, which is a bank's commitment to make loans up to a specific amount. Examples of items that might be included in the application of this element may consist of letters of credit, standby letters of credit, and revolving credit arrangements, under which borrowings can be made up to a maximum amount as of any point in time conditional on satisfaction of specified terms before, as of and after the date of drawdowns on the line. Includes short-term obligations that would normally be classified as current liabilities but for which (a) postbalance sheet date issuance of a long term obligation to refinance the short term obligation on a long term basis, or (b) the enterprise has entered into a financing agreement that clearly permits the enterprise to refinance the short-term obligation on a long term basis and the following conditions are met (1) the agreement does not expire within 1 year and is not cancelable by the lender except for violation of an objectively determinable provision, (2) no violation exists at the BS date, and (3) the lender has entered into the financing agreement is expected to be financially capable of honoring the agreement.

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-SubTopic 10
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-Paragraph 1
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-Section S99
-Paragraph 1
-Subparagraph (SX 210.7-03(16))
-URI http://asc.fasb.org/extlink&oid=6879938&loc=d3e572229-122910

+ Details

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Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Date the first payment under the line of credit must be paid, in CCYY-MM-DD format.

+ References

+ Details

Name:	us-gaap_LineOfCreditFacilityDateOfFirstRequiredPayment1
Namespace Prefix:	us-gaap_
Data Type:	xbrli:dateItemType
Balance Type:	na
Period Type:	duration

- Definition

Date the credit facility terminates, in CCYY-MM-DD format.

+ References

+ Details

Name:	us-gaap_LineOfCreditFacilityExpirationDate1
Namespace Prefix:	us-gaap_
Data Type:	xbrli:dateItemType
Balance Type:	na
Period Type:	duration

- Definition

Period remaining on line of credit facility before it terminates, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

+ References

No definition available.

+ Details

Name:	us-gaap_LineOfCreditFacilityExpirationPeriod
Namespace Prefix:	us-gaap_
Data Type:	xbrli:durationItemType
Balance Type:	na
Period Type:	duration

- Definition

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

+ References

No definition available.

+ Details

Name:	us-gaap_LineOfCreditFacilityLineItems
Namespace Prefix:	us-gaap_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Definition

Maximum borrowing capacity under the credit facility without consideration of any current restrictions on the amount that could be borrowed or the amounts currently outstanding under the facility.

+ References

+ Details

Name:	us-gaap_LineOfCreditFacilityMaximumBorrowingCapacity
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Amount of the required periodic payment applied to principal.

+ References

+ Details

Name:	us-gaap_LineOfCreditFacilityPeriodicPaymentPrincipal
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

Amount of borrowing capacity currently available under the credit facility (current borrowing capacity less the amount of borrowings outstanding).

+ References

+ Details

Name:	us-gaap_LineOfCreditFacilityRemainingBorrowingCapacity
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Amount of cash inflow from contractual arrangement with the lender, including but not limited to, letter of credit, standby letter of credit and revolving credit arrangements.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 230
-SubTopic 10
-Section 45
-Paragraph 14
-Subparagraph (b)
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-Section S99
-Paragraph 1
-Subparagraph (SX 210.4-08.(f))
-URI http://asc.fasb.org/extlink&oid=26873400&loc=d3e23780-122690

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Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

The net amount of stock issued during the period upon the conversion of convertible securities, net of adjustments (for example, to additional paid in capital) including the write-off of an equity component recognized to record the convertible debt instrument as two separate components - a debt component and an equity component. This item is meant to disclose the value of shares issued on conversion of convertible securities that were recorded as two separate (debt and equity) components.

+ References

No definition available.

+ Details

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Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

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Balance Type:
Period Type:

- Details

Name:	us-gaap_CreditFacilityAxis=iivi_TermLoansMember
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Period Type:

- Details

Name:	us-gaap_CreditFacilityAxis=iivi_YenRevolvingCreditFacilityMember
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Balance Type:
Period Type:

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Balance Type:
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- Details

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- Details

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- Details

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Debt - Additional Information (Detail)			3 Months Ended	12 Months Ended
Debt - Additional Information (Detail)	Aug. 24, 2017 USD ($)	Jul. 28, 2016 USD ($)	Sep. 30, 2018 USD ($) $ / shares	Jun. 30, 2018 USD ($)	Sep. 30, 2018 JPY (¥)	Jun. 30, 2018 JPY (¥)	Sep. 30, 2017
Line Of Credit Facility [Line Items]
Available credit under lines of credit			$ 146,300,000	$ 246,400,000
Total outstanding letters of credit			$ 400,000	400,000
Weighted average interest rate of total borrowings			1.50%		1.50%		1.80%
Revolving Credit Facility
Line Of Credit Facility [Line Items]
Line of credit, maximum borrowing capacity		$ 325,000,000
Credit facility, term		5 years
Debt instrument maturity date		Jul. 27, 2021
Term Loans
Line Of Credit Facility [Line Items]
Line of credit, maximum borrowing capacity		$ 100,000,000
Term loan, quarterly principal Payment		$ 5,000,000
Term loan, maturity date		Jul. 27, 2021
Term loan, first quarterly principal payment commencement date		Oct. 01, 2016
Yen denominated line of credit
Line Of Credit Facility [Line Items]
Line of credit, maximum borrowing capacity			$ 4,400,000		¥ 500,000,000
Debt instrument, month and year of maturity			2020-08
Line of credit, outstanding \| ¥					¥ 300,000,000	¥ 300,000,000
Maximum \| Revolving Credit Facility
Line Of Credit Facility [Line Items]
Credit facility, optional additional borrowing amount		$ 100,000,000
Base Rate Option \| Minimum \| Revolving Credit Facility
Line Of Credit Facility [Line Items]
Debt instrument, rate added on variable rate		0.00%
Base Rate Option \| Maximum \| Revolving Credit Facility
Line Of Credit Facility [Line Items]
Debt instrument, rate added on variable rate		1.25%
Euro Rate Option \| Minimum \| Revolving Credit Facility
Line Of Credit Facility [Line Items]
Debt instrument, rate added on variable rate		1.00%
Euro Rate Option \| Maximum \| Revolving Credit Facility
Line Of Credit Facility [Line Items]
Debt instrument, rate added on variable rate		2.25%
London Interbank Offered Rate (LIBOR) \| Term Loans
Line Of Credit Facility [Line Items]
Debt instrument, rate added on variable rate			1.75%
London Interbank Offered Rate (LIBOR) \| Yen denominated line of credit
Line Of Credit Facility [Line Items]
Debt instrument, rate added on variable rate			1.75%
London Interbank Offered Rate (LIBOR) \| Minimum \| Yen denominated line of credit
Line Of Credit Facility [Line Items]
Debt instrument, rate added on variable rate			0.625%
London Interbank Offered Rate (LIBOR) \| Maximum \| Yen denominated line of credit
Line Of Credit Facility [Line Items]
Debt instrument, rate added on variable rate			1.75%
0.25% Convertible Senior Note Due 2022
Line Of Credit Facility [Line Items]
Debt instrument, interest rate			0.25%		0.25%
Equity portion of convertible debt			$ 56,400,000
Debt issuance costs			$ 1,700,000
Debt instrument conversion, shares issued per $1,000 principal amount			21.25
Debt instrument conversion, principal amount of each note converted			$ 1,000
Debt instrument conversion, conversion price per share \| $ / shares			$ 47.06
Debt instrument conversion, If-converted value of notes			$ 346,800,000	$ 318,500,000
Effective interest rate			4.50%		4.50%		4.50%
Unamortized discount			$ 46,600,000
Amortization period			4 years
Debt instrument maturity date			Sep. 01, 2022
0.25% Convertible Senior Note Due 2022 \| Initial Purchasers
Line Of Credit Facility [Line Items]
Aggregate principal amount	$ 300,000,000
Debt instrument, interest rate	0.25%
0.25% Convertible Senior Notes Over-Allotment Option \| Initial Purchasers
Line Of Credit Facility [Line Items]
Aggregate principal amount	$ 45,000,000
Number of days option granted to purchase additional principal amount of notes	30 days