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Defined Contribution Bonus and Profit Sharing Plans Narrative (Details) - Employer Match Percentage [Member] | 12 Months Ended
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Dec. 31, 2017
Deferred Compensation Arrangement with Individual, Excluding Share-based Payments and Postretirement Benefits [Line Items] |
Percentage of employer match into employee savings plan. | 75.00%
Employer Matching Contribution, Percent of Employees' Gross Pay | 6.00%

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- Definition Percentage of employer match into employee savings plan. + References No definition available. + Details
Name: | itri_PercentageOfEmployerMatchIntoEmployeeSavingsPlan
Namespace Prefix: | itri_
Data Type: | num:percentItemType
Balance Type: | na
Period Type: | duration

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- Definition Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table. + References No definition available. + Details
Name: | us-gaap_DeferredCompensationArrangementWithIndividualExcludingShareBasedPaymentsAndPostretirementBenefitsLineItems
Namespace Prefix: | us-gaap_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration

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- Definition Percentage of employees' gross pay for which the employer contributes a matching contribution to a defined contribution plan. + References No definition available. + Details
Name: | us-gaap_DefinedContributionPlanEmployerMatchingContributionPercent
Namespace Prefix: | us-gaap_
Data Type: | num:percentItemType
Balance Type: | na
Period Type: | duration

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- Details
Name: | itri_DefinedContributionByNatureAxis=itri_EmployerMatchPercentageMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |