XML 46 R33.htm IDEA: XBRL DOCUMENT
v3.3.1.900

Loans Held For Sale And Loan Servicing Rights (Tables) | 12 Months Ended
--- | ---
Dec. 31, 2015
Loans Held For Sale And Loan Servicing Rights [Abstract] |
Activity In Capitalized Mortgage Servicing Assets |
|  | 2015 |  |  | 2014 |  |  | 2013 |
Mortgage servicing assets, beginning of year | $ | 1,335 |  | $ | 1,479 |  | $ | 1,637 |
Originations |  | 166 |  |  | 172 |  |  | 277 |
Amortization |  | (276 | ) |  | (316 | ) |  | (435 | )
Mortgage servicing assets, end of year |  | 1,225 |  |  | 1,335 |  |  | 1,479 |
Valuation allowance |  | (1 | ) |  | (6 | ) |  | (3 | )
Mortgage servicing assets, net, end of year | $ | 1,224 |  | $ | 1,329 |  | $ | 1,476 |

X
- Definition Activity In Capitalized Mortgage Servicing Assets [Table Text Block] + References No definition available. + Details
Name: | fisi_ActivityInCapitalizedMortgageServicingAssetsTableTextBlock
Namespace Prefix: | fisi_
Data Type: | nonnum:textBlockItemType
Balance Type: | na
Period Type: | duration

X
- Definition Loans Held For Sale And Loan Servicing Rights [Abstract] + References No definition available. + Details
Name: | fisi_LoansHeldForSaleAndLoanServicingRightsAbstract
Namespace Prefix: | fisi_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration