RETIREMENT PLANS (Details) - USD ($) $ in Thousands	3 Months Ended	9 Months Ended
Jun. 30, 2026	Jun. 30, 2025	Jun. 30, 2026	Jun. 30, 2025	Sep. 30, 2025
Pension Plan
Net periodic benefit cost:
Interest cost	$ 102	$ 98	$ 306	$ 293
Expected return on plan assets	(218)	(200)	(653)	(600)
Amortization of net actuarial gain	(12)	0	(37)	0
Net periodic benefit (income) cost	(128)	(102)	(384)	(307)
Other disclosures
Estimated future contributions	$ 0		$ 0
Number of Barnwell common stock held by the Pension Plan (in shares)	676,296		676,296		666,077
SERP
Net periodic benefit cost:
Interest cost	$ 26	24	$ 78	71
Expected return on plan assets	0	0	0	0
Amortization of net actuarial gain	0	0	0	0
Net periodic benefit (income) cost	26	$ 24	78	$ 71
Other disclosures
Estimated future contributions	$ 261		$ 261

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