v2.4.0.8

Activity of Valuation Allowance for Deferred Tax Assets (Detail) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011
Income Tax Disclosure [Abstract]
Valuation allowance at beginning of year	$ 82,125	$ 52,036
(Decrease) increase in valuation allowance as a result of Mergers and acquisitions, net		(4,563)
(Decrease) increase in valuation allowance as a result of current year operations	30,926	34,652
Valuation allowance at end of year	$ 113,051	$ 82,125

X

- Definition

Amount of deferred tax assets for which it is more likely than not that a tax benefit will not be realized.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 740

-SubTopic 10

-Section 50

-Paragraph 2

-Subparagraph (c)

-URI http://asc.fasb.org/extlink&oid=6907707&loc=d3e32537-109319

+ Details

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

X

- Details

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

X

- Definition

Valuation Allowance, Deferred Tax Asset, Change in Amount, Current Year Operations

+ References

No definition available.

+ Details

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

X

- Definition

Valuation Allowance, Deferred Tax Asset, Change in Amount Mergers And Acquisitions, Net

+ References

No definition available.

+ Details

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