Segment and Related Information - Narrative (Details)	12 Months Ended
	Dec. 31, 2021 segment	Dec. 31, 2021 subsidiary_Bank	Dec. 31, 2021 banking_Office	Dec. 31, 2021 subsidiaryTrust	Dec. 31, 2021 office	Dec. 31, 2020 banking_Office	Dec. 31, 2019 banking_Office
Segment Reporting Information [Line Items]
Number of reportable business segments	3			3
Number of subsidiary banks (banking office)		4				4	4
Ithaca, NY
Segment Reporting Information [Line Items]
Number of banking offices			13
Genesee Valley Region
Segment Reporting Information [Line Items]
Number of banking offices			16
Counties North of New York City
Segment Reporting Information [Line Items]
Number of banking offices			14
Southeastern Pennsylvania
Segment Reporting Information [Line Items]
Number of banking offices			20
Western New York
Segment Reporting Information [Line Items]
Nature of operations, number of offices | office					5