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v3.20.1

Operating Segments (Narrative) (Details) | Dec. 31, 2019 | Dec. 31, 2018 | Dec. 31, 2017
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Segment Reporting [Abstract] |  |  |
Percentage of reportable segments total assets and operating results, or more | 90.00% | 90.00% | 90.00%

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- Definition Percentage Of Reportable Segment, Assets And Operating Results + References No definition available. + Details
Name: | isba_PercentageOfReportableSegmentAssetsAndOperatingResults
Namespace Prefix: | isba_
Data Type: | num:percentItemType
Balance Type: | na
Period Type: | instant

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