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Basis of Consolidation Policy Additional Information (Details)
 3 Months Ended
Mar. 31, 2015
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 Interest [Abstract]  
Ownership Interest to be Held for Consolidation - Noncontrolling Interests 50.00%itri_OwnershipInterestToBeHeldForConsolidation
/ us-gaap_RangeAxis
= us-gaap_MinimumMember