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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Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | instant

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- Details
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Balance Type: | na
Period Type: | duration

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- Definition Valuation Allowance, Deferred Tax Asset, Change in Amount, Current Year Operations + References No definition available. + Details
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Namespace Prefix: | xon_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | duration

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- Definition Valuation Allowance, Deferred Tax Asset, Change in Amount Mergers And Acquisitions, Net + References No definition available. + Details
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Namespace Prefix: | xon_
Data Type: | xbrli:monetaryItemType
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