Operating Segments (Narrative) (Details)	Dec. 31, 2020	Dec. 31, 2019
Segment Reporting [Abstract]
Percentage of reportable segments total assets and operating results, or more	90.00%	90.00%

Percentage Of Reportable Segment, Assets And Operating Results

No definition available.

Name:	isba_PercentageOfReportableSegmentAssetsAndOperatingResults
Namespace Prefix:	isba_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	instant