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v3.21.4

Summary of Significant Accounting Policies - Revenue Recognition (Details) | 12 Months Ended
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Sep. 30, 2021
Revenue Recognition. |
Percentage of revenue from products to customer | 100.00%

X
- Definition The percentage of revenue from products transferred to customers at a point in time. + References No definition available. + Details
Name: | issc_RevenuePerformanceObligationSatisfiedAtPointInTimePercentageOfRevenue
Namespace Prefix: | issc_
Data Type: | dtr-types:percentItemType
Balance Type: | na
Period Type: | duration

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- References No definition available. + Details
Name: | us-gaap_RevenueFromContractWithCustomerAbstract
Namespace Prefix: | us-gaap_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration