Accumulated Other Comprehensive (Loss) Income - Summary of Amounts Reclassified Out of Each Component of AOCI (Details) - USD ($) $ in Thousands		3 Months Ended
		Mar. 31, 2023	Mar. 31, 2022
Reclassification Adjustment Out Of Accumulated Other Comprehensive Income [Line Items]
Salaries and employee benefits		$ (4,183)	$ (4,049)
Provision for income taxes		(669)	(721)
Net (losses) income attributable to Pathfinder Bancorp Inc.		2,599	2,950
Reclassification out of Accumulated Other Comprehensive Income [Member] | Retirement Plans [Member]
Reclassification Adjustment Out Of Accumulated Other Comprehensive Income [Line Items]
Salaries and employee benefits	[1],[2]	(55)	1
Provision for income taxes	[1]	14	0
Net (losses) income attributable to Pathfinder Bancorp Inc.	[1]	(41)	(1)
Reclassification out of Accumulated Other Comprehensive Income [Member] | Available-for-sale securities
Reclassification Adjustment Out Of Accumulated Other Comprehensive Income [Line Items]
Net gains on sales and redemptions of investment securities	[1]	(1,933)	0
Provision for income taxes	[1]	505	0
Net (losses) income attributable to Pathfinder Bancorp Inc.	[1]	$ (1,428)	$ 0

[1] Amounts in parentheses indicates debits in net income.

[2] These items are included in net periodic pension cost.