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FAIR VALUE MEASUREMENTS (Details) (USD $) In Thousands, unless otherwise specified	Mar. 31, 2012	Dec. 31, 2011
Significant Other Observable Inputs (level 2) | Recurring basis
Summarizes the valuation of interest rate swaps and impaired assets
Interest rate swaps asset (liability)	$ (15,531)	$ (19,446)
Significant Unobservable Inputs (Level 3) | Nonrecurring basis
Summarizes the valuation of interest rate swaps and impaired assets
Impaired long-lived assets	$ 1,800

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- Definition

Interest rate swaps asset liability fair value disclosure.

+ References

No definition available.

+ Details

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- Definition

Long-lived asset impairment fair value disclosure.

+ References

No definition available.

+ Details

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Namespace Prefix:	exh_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

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- Details

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