Acquired finished goods and work in process amortization period

No definition available.

Name:	cohr_Acquiredfinishedgoodsandworkinprocessamortizationperiod
Namespace Prefix:	cohr_
Data Type:	xbrli:durationItemType
Balance Type:	na
Period Type:	duration

- Definition

Goodwill reallocated from AFS to remaining business during remeasurement period

+ References

No definition available.

+ Details

Name:	cohr_GoodwillreallocatedfromAFStoremainingbusinessduringremeasurementperiod
Namespace Prefix:	cohr_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

incremental cost of sales recorded from inventory fair value adjustment

+ References

No definition available.

+ Details

Name:	cohr_Incrementalcostofsalesrecordedfrominventoryfairvalueadjustment
Namespace Prefix:	cohr_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

payment due to cancellation of options held by Rofin employees

+ References

No definition available.

+ Details

Name:	cohr_PaymentduetocancellationofoptionsheldbyRofinemployees
Namespace Prefix:	cohr_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

Post merger stock compensation expense

+ References

No definition available.

+ Details

Name:	cohr_Postmergerstockcompensationexpense
Namespace Prefix:	cohr_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

Total estimated merger consideration for canceled of options held by Rofin employees

+ References

No definition available.

+ Details

Name:	cohr_TotalestimatedmergerconsiderationforcanceledofoptionsheldbyRofinemployees
Namespace Prefix:	cohr_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

Amount of addition (reduction) to the amount at which an asset could be incurred (settled) in a current transaction between willing parties.

+ References

No definition available.

+ Details

Name:	us-gaap_AssetsFairValueAdjustment
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
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_BusinessAcquisitionLineItems
Namespace Prefix:	us-gaap_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Definition

Price of a single share of a number of saleable stocks paid or offered to be paid in a business combination.

+ References

No definition available.

+ Details

Name:	us-gaap_BusinessAcquisitionSharePrice
Namespace Prefix:	us-gaap_
Data Type:	num:perShareItemType
Balance Type:	na
Period Type:	instant

- Definition

This element represents acquisition-related costs incurred to effect a business combination which costs have been expensed during the period. Such costs include finder's fees; advisory, legal, accounting, valuation, and other professional or consulting fees; general administrative costs, including the costs of maintaining an internal acquisitions department; and may include costs of registering and issuing debt and equity securities.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 805
-SubTopic 10
-Section 25
-Paragraph 23
-URI http://asc.fasb.org/extlink&oid=84229725&loc=d3e1043-128460

+ Details

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

- Definition

In a business combination achieved in stages, this element represents the amount of gain recognized by the entity as a result of remeasuring to fair value the equity interest in the acquiree it held before the business combination.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 805
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (g)(2)
-URI http://asc.fasb.org/extlink&oid=79982066&loc=d3e1392-128463

+ Details

Name:	us-gaap_BusinessCombinationStepAcquisitionEquityInterestInAcquireeRemeasurementGain
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

Useful life of finite-lived intangible assets, 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_FiniteLivedIntangibleAssetUsefulLife
Namespace Prefix:	us-gaap_
Data Type:	xbrli:durationItemType
Balance Type:	na
Period Type:	duration

- Definition

The consolidated profit or loss for the period, net of income taxes, including the portion attributable to the noncontrolling interest.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 810
-SubTopic 10
-Section 55
-Paragraph 4K
-URI http://asc.fasb.org/extlink&oid=84234705&loc=SL4591552-111686

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 810
-SubTopic 10
-Section 45
-Paragraph 19
-URI http://asc.fasb.org/extlink&oid=96868048&loc=SL4569616-111683

Reference 3: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 810
-SubTopic 10
-Section 50
-Paragraph 1A
-Subparagraph (c)(1)
-URI http://asc.fasb.org/extlink&oid=84161450&loc=SL4573702-111684

Reference 4: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 810
-SubTopic 10
-Section 55
-Paragraph 4J
-URI http://asc.fasb.org/extlink&oid=84234705&loc=SL4591551-111686

Reference 5: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 810
-SubTopic 10
-Section 50
-Paragraph 1A
-Subparagraph (a)(2)
-URI http://asc.fasb.org/extlink&oid=84161450&loc=SL4573702-111684

+ Details

Name:	us-gaap_ProfitLoss
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

Amount of revenue recognized from goods sold, services rendered, insurance premiums, or other activities that constitute an earning process. Includes, but is not limited to, investment and interest income before deduction of interest expense when recognized as a component of revenue, and sales and trading gain (loss).

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 225
-SubTopic 10
-Section S99
-Paragraph 2
-Subparagraph (SX 210.5-03.1)
-URI http://asc.fasb.org/extlink&oid=63488584&loc=d3e20235-122688

+ Details

Name:	us-gaap_Revenues
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Details

Name:	us-gaap_BusinessAcquisitionAxis=cohr_RofinSinarMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_FiniteLivedIntangibleAssetsByMajorClassAxis=us-gaap_InventoriesMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_FiniteLivedIntangibleAssetsByMajorClassAxis=us-gaap_PropertyPlantAndEquipmentMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_FiniteLivedIntangibleAssetsByMajorClassAxis=us-gaap_OrderOrProductionBacklogMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_FiniteLivedIntangibleAssetsByMajorClassAxis=us-gaap_TrademarksMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_FiniteLivedIntangibleAssetsByMajorClassAxis=us-gaap_PatentsMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_RangeAxis=us-gaap_MinimumMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_FiniteLivedIntangibleAssetsByMajorClassAxis=us-gaap_DevelopedTechnologyRightsMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_FiniteLivedIntangibleAssetsByMajorClassAxis=us-gaap_CustomerRelationshipsMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_RangeAxis=us-gaap_MaximumMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

Business Combinations - Rofin Acquisition Narrative (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended			9 Months Ended
	Jul. 01, 2017	Dec. 31, 2016	Jul. 02, 2016	Jul. 01, 2017	Jul. 02, 2016	Nov. 07, 2016
Business Acquisition [Line Items]
Acquisition price per share of Rofin						$ 32.50
Gain from business combination	$ 0		$ 0	$ (5,416)	$ 0
Rofin-Sinar
Business Acquisition [Line Items]
Acquired finished goods and work in process amortization period		6 months
payment due to cancellation of options held by Rofin employees		$ 15,290
Total estimated merger consideration for canceled of options held by Rofin employees		11,100
Post merger stock compensation expense				4,152
Gain from business combination		(5,400)
Business Combination, Acquisition Related Costs	400			17,600
Revenues	116,500			301,600
Net Income (Loss), Including Portion Attributable to Noncontrolling Interest	(6,500)			(36,400)
Goodwill reallocated from AFS to remaining business during remeasurement period	33,900
Inventory \| Rofin-Sinar
Business Acquisition [Line Items]
Assets, Fair Value Adjustment		26,800
incremental cost of sales recorded from inventory fair value adjustment	$ 4,400			$ 26,400
Property and equipment \| Rofin-Sinar
Business Acquisition [Line Items]
Assets, Fair Value Adjustment		$ 36,800
Backlog \| Rofin-Sinar
Business Acquisition [Line Items]
Finite-Lived Intangible Asset, Useful Life		6 months
Trademarks \| Rofin-Sinar
Business Acquisition [Line Items]
Finite-Lived Intangible Asset, Useful Life		3 years
Patents \| Rofin-Sinar
Business Acquisition [Line Items]
Finite-Lived Intangible Asset, Useful Life		5 years
Minimum \| Existing technology \| Rofin-Sinar
Business Acquisition [Line Items]
Finite-Lived Intangible Asset, Useful Life		3 years
Minimum \| Customer relationships \| Rofin-Sinar
Business Acquisition [Line Items]
Finite-Lived Intangible Asset, Useful Life		5 years
Maximum \| Existing technology \| Rofin-Sinar
Business Acquisition [Line Items]
Finite-Lived Intangible Asset, Useful Life		5 years
Maximum \| Customer relationships \| Rofin-Sinar
Business Acquisition [Line Items]
Finite-Lived Intangible Asset, Useful Life		10 years