v2.4.0.8

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

X

- 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

Name:	us-gaap_AvailableForSaleSecuritiesContinuousUnrealizedLossPositionLessThanTwelveMonthsFairValue
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

X

- Details

Name:	xon_AmortizedCostAndFairValueDebtSecuritiesAbstract
Namespace Prefix:	xon_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

X

- 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

Name:	xon_AvailableforsaleDebtSecuritiesGrossUnrealizedLossAccumulatedInInvestments
Namespace Prefix:	xon_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant