XML 61 R51.htm IDEA: XBRL DOCUMENT v3.8.0.1

Borrowed Funds (Maturity and weighted average interest rates of FHLB advances) (Details) - USD ($) $ in Thousands	Mar. 31, 2018	Dec. 31, 2017
Federal Home Loan Bank, Advances [Line Items]
FHLB advances, rate	1.94%	1.94%
FHLB advances	$ 260,000	$ 290,000
Fixed Rate Advances Due 2018 [Member]
Federal Home Loan Bank, Advances [Line Items]
FHLB advances, rate	1.57%	1.96%
FHLB fixed rate advances	$ 30,000	$ 70,000
Fixed Rate Advances Due 2019 [Member]
Federal Home Loan Bank, Advances [Line Items]
FHLB advances, rate	1.87%	1.87%
FHLB fixed rate advances	$ 85,000	$ 85,000
Fixed Rate Advances Due 2020 [Member]
Federal Home Loan Bank, Advances [Line Items]
FHLB advances, rate	1.80%	1.80%
FHLB fixed rate advances	$ 35,000	$ 35,000
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	$ 10,000	$ 10,000
FHLB advances, rate	2.15%	1.72%
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
Fixed Rate Advances Due 2023 [Member]
Federal Home Loan Bank, Advances [Line Items]
FHLB advances, rate	3.36%	3.90%
FHLB fixed rate advances	$ 20,000	$ 10,000
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

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_FederalHomeLoanBankAdvancesFixedRateDue2018Member
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

X

- Details

Name:	us-gaap_DebtInstrumentAxis=isba_FederalHomeLoanBankAdvancesFixedRateDue2019Member
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

X

- Details

Name:	us-gaap_DebtInstrumentAxis=isba_FederalHomeLoanBankAdvancesFixedRateDue2020Member
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

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_FederalHomeLoanBankAdvancesFixedRateDue2023Member
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: