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Basis of Presentation and Summary of Significant Accounting Policies (Details) | 3 Months Ended
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Mar. 31, 2013
Minimum |
Revenue Recognition |
Duration of fabrication projects | 3 months
Maximum |
Revenue Recognition |
Duration of fabrication projects | 36 months

X
- Definition Duration of fabrication projects. + References No definition available. + Details
Name: | exh_DurationOfFabricationProjects
Namespace Prefix: | exh_
Data Type: | xbrli:durationItemType
Balance Type: | na
Period Type: | duration

X
- Details
Name: | exh_SummaryOfSignificantAccountingPoliciesLineItems
Namespace Prefix: | exh_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration