v3.25.3

Defined Pension Plans - Narrative (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended		12 Months Ended
	Sep. 30, 2025	Sep. 30, 2024	Sep. 30, 2025	Sep. 30, 2024	Dec. 31, 2024
Defined Benefit Plan Disclosure [Line Items]
Net periodic cost (benefit)	$ 0	$ 195	$ 0	$ 581
Proceeds from sales of investment securities available-for-sale	72,700	0	125,815	24,985
Available-for-sale securities, gross realized gains	351,000	0	351,000	0
Pension Plan
Defined Benefit Plan Disclosure [Line Items]
Net periodic cost (benefit)	0	195	0	581
Supplemental Employee Retirement Plan
Defined Benefit Plan Disclosure [Line Items]
Net periodic cost (benefit)	$ 113	$ 113	$ 338	$ 338	$ 450

Amount of realized gain on investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale).

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Topic 320
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+ References

No definition available.

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Amount of net periodic benefit cost (credit) for defined benefit plan.

+ References

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-Topic 715
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Amount of cash inflow from sale of investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale).

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Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Topic 320
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CASS INFORMATION SYSTEMS INC 10-Q