Summary of Significant Accounting Policies Basis of Consolidation Policy Additional Information (Details)	12 Months Ended
Dec. 31, 2011
Maximum [Member]
Ownership Interest to be Held for Consolidation [Line Items]
Ownership Interest To Use Equity Method	50.00%
Ownership Interest To Use Cost Method	20.00%
Minimum [Member]
Ownership Interest to be Held for Consolidation [Line Items]
Ownership Interest to be Held for Consolidation	50.00%

Entities in which the company has less than 20% investment and where they do not excercise significant influence are accounted for under the cost method.

No definition available.

Name:	itri_OwnershipInterestToUseCostMethod
Namespace Prefix:	itri_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration