Name:	iiin_DefinedBenefitPlanEmploymentTerm
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The number of consecutive years used to determine a Participant's highest average annual base salary in a supplemental employee retirement plan.

No definition available.

Name:	iiin_DefinedBenefitPlanNumberOfYearsInAverageAnnualBaseSalary
Namespace Prefix:	iiin_
Data Type:	xbrli:durationItemType
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Defined benefit plan number of years preceding retirement for average annual base salary calculation

No definition available.

Name:	iiin_DefinedBenefitPlanNumberOfYearsPrecedingRetirementForAverageAnnualBaseSalaryCalculation
Namespace Prefix:	iiin_
Data Type:	xbrli:durationItemType
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The percentage of a Participant's highest average base salary that will be paid out to the Participant as supplemental retirement benefits if they meet the continuous service requirement.

No definition available.

Name:	iiin_DefinedBenefitPlanPercentOfHighestAverageSalaryBase
Namespace Prefix:	iiin_
Data Type:	num:percentItemType
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Period Type:	duration

The benefit will be reduced by a certain percentage for each month short of 30 years that the Participant was employed by the Company assuming the minimum continuous service and age requirements.

No definition available.

Name:	iiin_DefinedBenefitPlanReductionForEachMonth
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Data Type:	num:percentItemType
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Period Type:	instant

The minimum age that an employee may retire at to receive benefits.

No definition available.

Name:	iiin_DefinedBenefitPlanRetirementAge
Namespace Prefix:	iiin_
Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	duration

The maximum period of time that a Participant will be paid supplemental retirement benefits if they are eligible for full benefits.

No definition available.

Name:	iiin_SupplementalRetirementBenefitPeriod
Namespace Prefix:	iiin_
Data Type:	xbrli:durationItemType
Balance Type:	na
Period Type:	duration

Fair value of assets that have been segregated and restricted to provide pension or postretirement benefits. Assets include, but are not limited to, stocks, bonds, other investments, earnings from investments, and contributions by the employer and employees.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 715
-SubTopic 20
-Section 50
-Paragraph 1
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=82843861&loc=d3e1928-114920

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Name:	us-gaap_RetirementPlanTypeAxis=iiin_ReducedSERPMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

Name:	us-gaap_RetirementPlanTypeAxis=us-gaap_PensionPlansDefinedBenefitMember
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Data Type:	na
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