Number of shares of equity interests issued or issuable to acquire entity.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 805
-SubTopic 30
-Section 50
-Paragraph 1
-Subparagraph (b)(4)
-URI http://asc.fasb.org/extlink&oid=35744584&loc=d3e6927-128479

+ Details

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Namespace Prefix:	us-gaap_
Data Type:	xbrli:sharesItemType
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

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

- Definition

Percentage of voting equity interests acquired at the acquisition date in 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 (c)
-URI http://asc.fasb.org/extlink&oid=79982066&loc=d3e1392-128463

+ Details

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

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Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
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 period subsequent to the acquisition during which a portion of collaboration payments received from previously existing collaborations will be paid to former stockholders of the acquired entity.

+ References

No definition available.

+ Details

Name:	xon_BusinessCombinationPeriodSubsequenttoAcquisitionDuringWhichAPortionofCollaborationPaymentsReceivedWillBePaidtoFormerStockholdersofAcquiredEntity
Namespace Prefix:	xon_
Data Type:	xbrli:durationItemType
Balance Type:	na
Period Type:	duration

- Definition

Percent of collaboration payments received pursuant to a collaboration agreement for upfront fees, milestones and royalties which will be paid to another party.

+ References

No definition available.

+ Details

Name:	xon_CollaborationArrangementPercentOfCollaborationPayments
Namespace Prefix:	xon_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

- Details

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Name:	us-gaap_IncomeStatementLocationAxis=us-gaap_SellingGeneralAndAdministrativeExpensesMember
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Data Type:	na
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Period Type:

Mergers and Acquisitions - GenVec - Additional Information (Details) - GenVec, Inc. - USD ($) $ in Thousands	1 Months Ended	3 Months Ended	9 Months Ended
	Jun. 30, 2017	Sep. 30, 2017	Sep. 30, 2017
Business Acquisition [Line Items]
Percentage of outstanding common stock acquired	100.00%
Business combination, consideration paid, shares issued	684,240
Percent of collaboration payments	50.00%
Expected useful life of intangible asset	11 years
Period subsequent to acquisition during which a portion of collaboration payments received will be paid to former stockholders of acquired entity	3 years
Business combination, acquisition related costs			$ 519
Selling, general and administrative
Business Acquisition [Line Items]
Business combination, acquisition related costs		$ 9	$ 507