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Summary of Significant Accounting Policies Basis of Consolidation Policy Additional Information (Details)
 12 Months Ended
Dec. 31, 2014
Maximum [Member]  
Basis of Consolidation [Abstract]  
Ownership Interest To Use Equity Method 50.00%itri_OwnershipInterestToUseEquityMethod
/ us-gaap_RangeAxis
= us-gaap_MaximumMember
Ownership Interest To Use Cost Method 20.00%itri_OwnershipInterestToUseCostMethod
/ us-gaap_RangeAxis
= us-gaap_MaximumMember
Minimum [Member]  
Basis of Consolidation [Abstract]  
Ownership Interest to be Held for Consolidation 50.00%itri_OwnershipInterestToBeHeldForConsolidation
/ us-gaap_RangeAxis
= us-gaap_MinimumMember
Noncontrolling Interests [Abstract]  
Ownership Interest to be Held for Consolidation 50.00%itri_OwnershipInterestToBeHeldForConsolidation
/ us-gaap_RangeAxis
= us-gaap_MinimumMember