Asset purchase agreement closing date.

No definition available.

Name:	extr_AssetPurchaseAgreementClosingDate
Namespace Prefix:	extr_
Data Type:	xbrli:dateItemType
Balance Type:	na
Period Type:	duration

- Definition

Interest rate floor.

+ References

No definition available.

+ Details

Name:	extr_InterestRateFloor
Namespace Prefix:	extr_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

Line of credit additional incremental loan facility.

+ References

No definition available.

+ Details

Name:	extr_LineOfCreditAdditionalIncrementalLoanFacility
Namespace Prefix:	extr_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Line of credit facility maturity month and year.

+ References

No definition available.

+ Details

Name:	extr_LineOfCreditFacilityMaturityMonthAndYear
Namespace Prefix:	extr_
Data Type:	xbrli:gYearMonthItemType
Balance Type:	na
Period Type:	duration

- Definition

Line of credit facility termination month and year.

+ References

No definition available.

+ Details

Name:	extr_LineOfCreditFacilityTerminationMonthAndYear
Namespace Prefix:	extr_
Data Type:	xbrli:gYearMonthItemType
Balance Type:	na
Period Type:	duration

- Definition

Payments to deposits for acquisition.

+ References

No definition available.

+ Details

Name:	extr_PaymentsToDepositsForAcquisition
Namespace Prefix:	extr_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

Amount of consideration transferred, consisting of acquisition-date fair value of assets transferred by the acquirer, liabilities incurred by the acquirer, and equity interest issued by the acquirer.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 805
-SubTopic 30
-Section 30
-Paragraph 7
-URI http://asc.fasb.org/extlink&oid=6911251&loc=d3e6578-128477

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 805
-SubTopic 30
-Section 50
-Paragraph 1
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=35744584&loc=d3e6927-128479

Reference 3: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 805
-SubTopic 30
-Section 30
-Paragraph 8
-URI http://asc.fasb.org/extlink&oid=6911251&loc=d3e6613-128477

+ Details

Name:	us-gaap_BusinessCombinationConsiderationTransferred1
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

For transactions that are recognized separately from the acquisition of assets and assumptions of liabilities in the business combination, such as related to pre-existing relationships with the acquiree, this element represents the disclosure of the amount of acquisition related costs which have been expensed.

+ 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 (f)
-URI http://asc.fasb.org/extlink&oid=79982066&loc=d3e1392-128463

+ Details

Name:	us-gaap_BusinessCombinationSeparatelyRecognizedTransactionsAdditionalDisclosuresAcquisitionCostExpensed
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
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

Name:	us-gaap_DebtInstrumentBasisSpreadOnVariableRate1
Namespace Prefix:	us-gaap_
Data Type:	num:percentItemType
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

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02.19(b),22(b))
-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

+ Details

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

- Definition

The fee, expressed as a percentage of the line of credit facility, for available but unused credit capacity under the credit facility.

+ References

No definition available.

+ Details

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

- Definition

The cash inflow from bank borrowing during the year.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 230
-SubTopic 10
-Section 45
-Paragraph 14
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=98514028&loc=d3e3255-108585

+ Details

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

- Definition

Detail information of subsequent event by type. User is expected to use existing line items from elsewhere in the taxonomy as the primary line items for this disclosure, which is further associated with dimension and member elements pertaining to a subsequent event.

+ References

No definition available.

+ Details

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

- Details

Name:	us-gaap_CreditFacilityAxis=extr_CreditFacilityMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

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

- Details

Name:	us-gaap_IncomeStatementLocationAxis=extr_AcquisitionAndIntegrationCostsMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_SubsequentEventTypeAxis=us-gaap_SubsequentEventMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_DebtInstrumentAxis=extr_SecondAmendmentMember
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:

- Details

Name:	us-gaap_CreditFacilityAxis=extr_TermLoanFacilityMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_CreditFacilityAxis=us-gaap_RevolvingCreditFacilityMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_VariableRateAxis=us-gaap_LondonInterbankOfferedRateLIBORMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_VariableRateAxis=us-gaap_BaseRateMember
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_CreditFacilityAxis=extr_AmendedTermLoanMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

Subsequent Event - (Narratives) (Details) - USD ($)			3 Months Ended	12 Months Ended
Subsequent Event - (Narratives) (Details) - USD ($)	Jul. 14, 2017	Mar. 07, 2017	Mar. 31, 2017	Jun. 30, 2017	Oct. 28, 2016
Subsequent Event [Line Items]
Borrowings under Term Loan				$ 48,250,000
Credit Facility
Subsequent Event [Line Items]
Borrowing capacity from Credit Facility, as amended					$ 140,500,000
Avaya Networking
Subsequent Event [Line Items]
Business acquisition, purchase price		$ 100,000,000
Business acquisition, deposits amount			$ 10,200,000
Avaya Networking \| Acquisition and Integration Costs
Subsequent Event [Line Items]
Acquisition-related costs				$ 2,200,000
Subsequent Event \| Second Amendment \| Maximum
Subsequent Event [Line Items]
Additional incremental loan facility	$ 50,000,000
Subsequent Event \| Second Amendment \| Credit Facility
Subsequent Event [Line Items]
Borrowing capacity from Credit Facility, as amended	243,700,000
Subsequent Event \| Second Amendment \| Term Loan
Subsequent Event [Line Items]
Borrowing capacity from Credit Facility, as amended	$ 183,700,000
Extended maturity date	2022-07
Subsequent Event \| Second Amendment \| Revolving Loan Facility
Subsequent Event [Line Items]
Borrowing capacity from Credit Facility, as amended	$ 60,000,000
Termination date	2022-07
Subsequent Event \| Avaya Networking
Subsequent Event [Line Items]
Asset purchase agreement closing date	Jul. 14, 2017
Subsequent Event \| Avaya Networking \| Term Loan
Subsequent Event [Line Items]
Borrowings under Term Loan	$ 80,000,000
Interest rate, floor	0.00%
Subsequent Event \| Avaya Networking \| Term Loan \| London Interbank Offered Rate (LIBOR)
Subsequent Event [Line Items]
Interest rate, applicable margin	3.25%
Subsequent Event \| Avaya Networking \| Term Loan \| Adjusted Base Rate
Subsequent Event [Line Items]
Interest rate, applicable margin	1.25%
Subsequent Event \| Avaya Networking \| Revolving Loan Facility \| London Interbank Offered Rate (LIBOR)
Subsequent Event [Line Items]
Interest rate, applicable margin	3.25%
Subsequent Event \| Avaya Networking \| Revolving Loan Facility \| Adjusted Base Rate
Subsequent Event [Line Items]
Interest rate, applicable margin	1.25%
Subsequent Event \| Avaya Networking \| Revolving Loan Facility \| Maximum
Subsequent Event [Line Items]
Commitment fee	0.50%
Subsequent Event \| Avaya Networking \| Revolving Loan Facility \| Minimum
Subsequent Event [Line Items]
Commitment fee	0.375%
Subsequent Event \| Avaya Networking \| Amended Term Loan
Subsequent Event [Line Items]
Interest rate, floor	0.00%
Subsequent Event \| Avaya Networking \| Amended Term Loan \| London Interbank Offered Rate (LIBOR)
Subsequent Event [Line Items]
Interest rate, applicable margin	3.25%
Subsequent Event \| Avaya Networking \| Amended Term Loan \| Adjusted Base Rate
Subsequent Event [Line Items]
Interest rate, applicable margin	1.25%