Business Combinations (Summary of Unaudited Pro Forma Financial Information) (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	12 Months Ended
Jun. 30, 2017	Jun. 30, 2016
Business Acquisition Pro Forma Information [Abstract]
Net revenues	$ 641,390	$ 628,079
Net income (loss)	$ 7,380	$ (62,281)
Net earnings (loss) per share - basic	$ 0.07	$ (0.60)
Net earnings (loss) per share - diluted	$ 0.07	$ (0.60)
Shares used in per share calculation - basic	108,273	103,074
Shares used in per share calculation - diluted	111,472	103,074

Business acquisition pro forma shares used in earnings per share calculation basic.

No definition available.

Name:	extr_BusinessAcquisitionProFormaSharesUsedInEarningsPerShareCalculationBasic
Namespace Prefix:	extr_
Data Type:	xbrli:sharesItemType
Balance Type:	na
Period Type:	duration

- Definition

Business acquisition pro forma shares used in earnings per share calculation diluted.

+ References

No definition available.

+ Details

Name:	extr_BusinessAcquisitionProFormaSharesUsedInEarningsPerShareCalculationDiluted
Namespace Prefix:	extr_
Data Type:	xbrli:sharesItemType
Balance Type:	na
Period Type:	duration

- Definition

The pro forma basic net income per share for a period as if the business combination or combinations had been completed at the beginning of a period.

+ 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 (h)(2)-(3)
-URI http://asc.fasb.org/extlink&oid=79982066&loc=d3e1392-128463

+ Details

Name:	us-gaap_BusinessAcquisitionProFormaEarningsPerShareBasic
Namespace Prefix:	us-gaap_
Data Type:	num:perShareItemType
Balance Type:	na
Period Type:	duration

- Definition

The pro forma diluted net income per share for a period as if the business combination or combinations had been completed at the beginning of a period.

+ References

+ Details

Name:	us-gaap_BusinessAcquisitionProFormaEarningsPerShareDiluted
Namespace Prefix:	us-gaap_
Data Type:	num:perShareItemType
Balance Type:	na
Period Type:	duration

- References

No definition available.

+ Details

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

- Definition

The pro forma net Income or Loss for the period as if the business combination or combinations had been completed at the beginning of a period.

+ References

+ Details

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

- Definition

The pro forma revenue for a period as if the business combination or combinations had been completed at the beginning of the period.

+ References

+ Details

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