XML 59 R49.htm IDEA: XBRL DOCUMENT v3.21.1

Borrowed Funds (Maturity and weighted average interest rates of FHLB advances) (Details) - USD ($) $ in Thousands		Mar. 31, 2021	Dec. 31, 2020
Federal Home Loan Bank, Advances [Line Items]
FHLB advances, rate		1.68%	1.68%
FHLB advances		$ 90,000	$ 90,000
Fixed Rate Advances Due 2021 [Member]
Federal Home Loan Bank, Advances [Line Items]
FHLB advances, rate		1.91%	1.91%
FHLB fixed rate advances		$ 50,000	$ 50,000
Federal Home Loan Bank, Advances, Variable Rate Due 2021 [Member] [Member] [Member]
Federal Home Loan Bank, Advances [Line Items]
Federal Home Loan Bank, Advances, Floating Rate	[1]	$ 10,000	$ 10,000
FHLB advances, rate	[1]	0.50%	0.52%
Federal Home Loan Bank, Advances, Fixed Rate Due 2022 [Member]
Federal Home Loan Bank, Advances [Line Items]
FHLB advances, rate		1.97%	1.97%
FHLB fixed rate advances		$ 20,000	$ 20,000
Federal Home Loan Bank, Advances, Fixed Rate Due 2026 [Member]
Federal Home Loan Bank, Advances [Line Items]
FHLB advances, rate		1.17%	1.17%
FHLB fixed rate advances		$ 10,000	$ 10,000
[1] Hedged advance (see “Derivative Instruments” section below)

X

- Definition

Par amount of advances made and reported by Federal Home Loan Bank (FHLBank) with fixed interest rate.

+ References

No definition available.

+ Details

Name:	us-gaap_FederalHomeLoanBankAdvancesFixedRate
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

X

- Definition

Par amount of advances made and reported by Federal Home Loan Bank (FHLBank) with floating interest rate.

+ References

No definition available.

+ Details

Name:	us-gaap_FederalHomeLoanBankAdvancesFloatingRate
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

X

- Definition

Interest rate of advances made and reported by Federal Home Loan Bank (FHLBank).

+ References

No definition available.

+ Details

Name:	us-gaap_FederalHomeLoanBankAdvancesInterestRate
Namespace Prefix:	us-gaap_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	instant

X

- Definition

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

+ References

No definition available.

+ Details

Name:	us-gaap_FederalHomeLoanBankAdvancesLineItems
Namespace Prefix:	us-gaap_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

X

- Definition

Par amount of advances made and reported by Federal Home Loan Bank (FHLBank).

+ References

No definition available.

+ Details

Name:	us-gaap_FederalHomeLoanBankAdvancesParValue
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

X

- Details

Name:	us-gaap_DebtInstrumentAxis=isba_FederalHomeLoanBankAdvancesFixedRateDue2021Member
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

X

- Details

Name:	us-gaap_DebtInstrumentAxis=isba_FederalHomeLoanBankAdvancesVariableRateDue2021MemberMemberMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

X

- Details

Name:	us-gaap_DebtInstrumentAxis=isba_FederalHomeLoanBankAdvancesFixedRateDue2022Member
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

X

- Details

Name:	us-gaap_DebtInstrumentAxis=isba_FederalHomeLoanBankAdvancesFixedRateDue2026Member
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type: