RETIREMENT PLANS (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Mar. 31, 2026	Mar. 31, 2025	Mar. 31, 2026	Mar. 31, 2025	Sep. 30, 2025
Pension Plan
Net periodic benefit cost:
Interest cost	$ 102	$ 97	$ 204	$ 195
Expected return on plan assets	(217)	(200)	(435)	(400)
Amortization of net actuarial gain	(13)	0	(25)	0
Net periodic benefit (income) cost	(128)	(103)	(256)	(205)
Other disclosures
Estimated future contributions	$ 0		$ 0
Number of Barnwell common stock held by the Pension Plan	676,296		676,296		666,077
SERP
Net periodic benefit cost:
Interest cost	$ 26	24	$ 52	47
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	52	$ 47
Other disclosures
Estimated future contributions	$ 261		$ 261