XML 59 R60.htm IDEA: XBRL DOCUMENT v3.20.1

Goodwill and Other Intangible Assets (Changes in Carrying Amount of Goodwill) (Details) $ in Thousands	Mar. 31, 2020 USD ($)
Goodwill [Line Items]
Goodwill, beginning balance	$ 66,062
Goodwill, ending balance	66,062
Banking [Member]
Goodwill [Line Items]
Goodwill, beginning balance	48,536
Goodwill, ending balance	48,536
Non-Banking [Member]
Goodwill [Line Items]
Goodwill, beginning balance	17,526
Goodwill, ending balance	$ 17,526

X

- Definition

Amount after accumulated impairment loss of an asset representing future economic benefits arising from other assets acquired in a business combination that are not individually identified and separately recognized.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 350
-SubTopic 20
-Section 45
-Paragraph 5
-URI http://asc.fasb.org/extlink&oid=77989000&loc=SL49117168-202975

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 350
-SubTopic 20
-Section 45
-Paragraph 1
-URI http://asc.fasb.org/extlink&oid=99380562&loc=d3e13770-109266

+ Details

Name:	us-gaap_Goodwill
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
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_GoodwillLineItems
Namespace Prefix:	us-gaap_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

X

- Details

Name:	us-gaap_StatementBusinessSegmentsAxis=fisi_BankingSegmentMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

X

- Details

Name:	us-gaap_StatementBusinessSegmentsAxis=fisi_NonBankingMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type: