XML 59 R48.htm IDEA: XBRL DOCUMENT
v3.5.0.2

Loans (Information Related To Loans Modified In A TDR) (Details) $ in Thousands | 3 Months Ended | 6 Months Ended
--- | --- | ---
Jun. 30, 2016 USD ($) contract | Jun. 30, 2015 USD ($) contract | Jun. 30, 2016 USD ($) contract | Jun. 30, 2015 USD ($) contract
Financing Receivable, Modifications [Line Items] |  |  |  |
Number of Contracts | contract | 1 | 2 | 4 | 3
Pre-Modification Outstanding Recorded Investment | $ 214 | $ 1,342 | $ 1,076 | $ 2,024
Post-Modification Outstanding Recorded Investment | $ 214 | $ 1,342 | $ 1,076 | $ 1,672
Commercial Business [Member] |  |  |  |
Financing Receivable, Modifications [Line Items] |  |  |  |
Number of Contracts | contract | 1 | 2 | 3 | 2
Pre-Modification Outstanding Recorded Investment | $ 214 | $ 1,342 | $ 526 | $ 1,342
Post-Modification Outstanding Recorded Investment | $ 214 | $ 1,342 | $ 526 | $ 1,342
Commercial Mortgage [Member] |  |  |  |
Financing Receivable, Modifications [Line Items] |  |  |  |
Number of Contracts | contract |  |  | 1 | 1
Pre-Modification Outstanding Recorded Investment |  |  | $ 550 | $ 682
Post-Modification Outstanding Recorded Investment |  |  | $ 550 | $ 330

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_FinancingReceivableModificationsLineItems
Namespace Prefix: | us-gaap_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration

X
- Definition Number of financing receivables that have been modified by troubled debt restructurings. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 310 -SubTopic 10 -Section 50 -Paragraph 33 -URI http://asc.fasb.org/extlink&oid=49124121&loc=SL6953676-111524 + Details
Name: | us-gaap_FinancingReceivableModificationsNumberOfContracts2
Namespace Prefix: | us-gaap_
Data Type: | xbrli:integerItemType
Balance Type: | na
Period Type: | duration

X
- Definition Post-modification amount of investment in financing receivables modified by troubled debt restructurings. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 310 -SubTopic 10 -Section 50 -Paragraph 33 -URI http://asc.fasb.org/extlink&oid=49124121&loc=SL6953676-111524 + Details
Name: | us-gaap_FinancingReceivableModificationsPostModificationRecordedInvestment2
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | duration

X
- Definition Pre-modification amount of investment in financing receivables modified by troubled debt restructurings. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 310 -SubTopic 10 -Section 50 -Paragraph 33 -URI http://asc.fasb.org/extlink&oid=49124121&loc=SL6953676-111524 + Details
Name: | us-gaap_FinancingReceivableModificationsPreModificationRecordedInvestment2
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | duration

X
- Details
Name: | us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis=fisi_CommercialAndIndustrialMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis=us-gaap_CommercialRealEstateMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |