Additional amount of operating lease liability.

No definition available.

Name:	emkr_AdditionalOperatingLeaseLiability
Namespace Prefix:	emkr_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Additional amount of lessee's right to use underlying asset under operating lease.

+ References

No definition available.

+ Details

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Namespace Prefix:	emkr_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

The cash inflow from proceeds from sale and leaseback transaction net of transaction commissions and expenses.

+ References

No definition available.

+ Details

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Namespace Prefix:	emkr_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

The amount of purchase price under sale and lease back transaction.

+ References

No definition available.

+ Details

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Namespace Prefix:	emkr_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

Amount of assets held-for-sale that are not part of a disposal group.

+ References

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-Publisher FASB
-Name Accounting Standards Codification
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-Subparagraph (b)(2)
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Period Type:	instant

- Definition

For an entity that discloses a concentration risk in relation to quantitative amount, which serves as the "benchmark" (or denominator) in the equation, this concept represents the concentration percentage derived from the division.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
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Balance Type:	na
Period Type:	duration

- Definition

The amount of expense recognized in the current period that reflects the allocation of the cost of tangible assets over the assets' useful lives. Includes production and non-production related depreciation.

+ References

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+ Details

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

- Definition

Amount of gain (loss) on sale or disposal of property, plant and equipment assets, including oil and gas property and timber property.

+ References

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

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

- Definition

Amount of gain (loss) on sale and leaseback transaction from transfer of asset accounted for as sale.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 842
-SubTopic 40
-Section 50
-Paragraph 2
-Subparagraph (b)
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Balance Type:	credit
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- Details

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Property, Plant and Equipment, net - Narrative (Details) - USD ($) $ in Thousands		12 Months Ended
	Feb. 10, 2020	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2019
Property, Plant and Equipment [Line Items]
Depreciation		$ 4,000	$ 5,500	$ 7,100
Gain (loss) on sale of equipment		(500)	2,300
Assets held for sale		$ 1,241	1,568
Sale leaseback, transaction price	$ 13,200
Proceeds from sale of leasebacks	$ 12,800
Sale and leaseback transaction, gain (loss), net			300
Additional operating lease right use of assets			10,800
Additional operating right use of liabilities			$ 10,800
United States \| Long-lived assets \| Geographic Concentration Risk
Property, Plant and Equipment [Line Items]
Concentration risk percentage		96.00%	97.00%