XML 128 R34.htm IDEA: XBRL DOCUMENT
v3.20.1

Nature of Operations and Summary of Significant Accounting Policies (Tables) | 12 Months Ended
--- | ---
Dec. 31, 2019
Accounting Policies [Abstract] |
Schedule of equity method and other investments | Equity securities without readily determinable fair values consist of the following holdings as of December 31:
| 2019 |  | 2018
FHLB Stock | $ | 15,050 |  |  | $ | 15,050 |
Investment in joint venture | 4,246 |  |  | 7,565 |
FRB Stock | 1,999 |  |  | 1,999 |
Other | 334 |  |  | 334 |
Total | $ | 21,629 |  |  | $ | 24,948 |

X
- Definition Schedule of Equity Method And Other Investments [Table Text Block] + References No definition available. + Details
Name: | isba_ScheduleofEquityMethodAndOtherInvestmentsTableTextBlock
Namespace Prefix: | isba_
Data Type: | nonnum:textBlockItemType
Balance Type: | na
Period Type: | duration

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