v2.4.0.8

Short-term and Long-term Investments - Additional Information (Detail) (USD $) In Thousands, unless otherwise specified | Sep. 30, 2013
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Amortized Cost And Fair Value Debt Securities [Abstract] |
Unrealized losses | $ 9
Fair value of investments with unrealized losses | $ 73,144

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- Definition This item represents the aggregate fair value of investments in debt and equity securities categorized neither as held-to-maturity nor trading securities that have been in a continuous unrealized loss position for less than twelve months. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 320 -SubTopic 10 -Section 50 -Paragraph 7 -URI http://asc.fasb.org/extlink&oid=27724398&loc=d3e27337-111563 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 320 -SubTopic 10 -Section 50 -Paragraph 6 -Subparagraph (a)(1) -URI http://asc.fasb.org/extlink&oid=27724398&loc=d3e27290-111563 + Details
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Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

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- Details
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Period Type: | duration

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- Definition Amount of accumulated pre-tax unrealized loss before deducting pre-tax unrealized gain on investments in available-for-sale debt securities impacting investments. + References No definition available. + Details
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Namespace Prefix: | xon_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | instant