Consolidated Statements of Operations (Parenthetical) - USD ($) $ in Thousands	3 Months Ended	9 Months Ended
Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Related Party Transaction [Line Items]
Collaboration and licensing revenues	$ 28,155	$ 30,590	$ 89,384	$ 82,144
Related Parties, Aggregated
Related Party Transaction [Line Items]
Collaboration and licensing revenues	$ 24,492	$ 26,688	$ 77,937	$ 70,299

Revenue from contractual agreements with collaborators whereby the collaborators obtain exclusive access to the entity's proprietary technologies for use in the research, development and commercialization of products and/or treatments in a contractually specified field of use as well as revenue earned during the period relating to consideration received from another party for the right to use, but not own, certain of the entity's intangible assets. Includes revenue recognized from upfront payments received upon consummation of the agreement, reimbursements for costs incurred by the entity for research and development efforts, and milestone payments received upon achievement of specified development, regulatory and commercial activities as defined in the collaboration and licensing agreements.

No definition available.

Name:	xon_CollaborationAndLicensingRevenue
Namespace Prefix:	xon_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration