Note 8 - Long-term Debt - Amortization of Financing Costs (Details) $ in Thousands	Oct. 03, 2020 USD ($)
2021, Amortization	$ 65
2022, Amortization	65
2023, Amortization	65
2024, Amortization	$ 41

The amount of amortization costs in the next 12 months.

No definition available.

Name:	iiin_AmortizationOfFinancingCostsNext12Months
Namespace Prefix:	iiin_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant