Benefit Plans - Benefit Plans (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2025	Sep. 30, 2024	Sep. 30, 2025	Sep. 30, 2024
Pension Benefits [Member]
Benefit Plans [Abstract]
Service cost	$ 0	$ 0	$ 0	$ 0
Interest cost	297	289	890	867
Expected return on plan assets	(862)	(762)	(2,585)	(2,286)
Amortization of net gain	(241)	(19)	(723)	(57)
Amortization of prior service cost	0	0	0	0
Net periodic benefit	(806)	(492)	(2,418)	(1,476)
Other Postretirement Benefits [Member]
Benefit Plans [Abstract]
Service cost	4	5	13	14
Interest cost	87	72	260	216
Expected return on plan assets	(380)	(332)	(1,142)	(995)
Amortization of net gain	(276)	(184)	(828)	(551)
Amortization of prior service cost	2	4	9	10
Net periodic benefit	$ (563)	$ (435)	$ (1,688)	$ (1,306)

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.

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+ Details

TRUSTCO BANK CORP N Y 10-Q