Segment and Related Information (Narrative) (Details)	6 Months Ended
	Jun. 30, 2017 office banking_office segment subsidiary_trust
Segment Reporting Information [Line Items]
Number of reportable segments | segment	3
Nature of operations, number of unconsolidated subsidiary trusts | subsidiary_trust	4
Tompkins Insurance Agencies Inc
Segment Reporting Information [Line Items]
Noncontrolling interest, ownership percentage by parent	100.00%
Ithaca, NY
Segment Reporting Information [Line Items]
Nature of operations, number of banking offices	14
Genesee Valley Region, New York State
Segment Reporting Information [Line Items]
Nature of operations, number of banking offices	17
Counties North of New York City
Segment Reporting Information [Line Items]
Nature of operations, number of banking offices	14
Southeastern Pennsylvania
Segment Reporting Information [Line Items]
Nature of operations, number of banking offices	21
Western New York
Segment Reporting Information [Line Items]
Number of offices | office	5
Tompkins County, New York
Segment Reporting Information [Line Items]
Number of offices | office	1
Montgomery County, Pennsylvania
Segment Reporting Information [Line Items]
Number of offices | office	1