REVENUE FROM CONTRACTS WITH CUSTOMERS REVENUE FROM CONTRACT WITH CUSTOMERS - IMPACT OF ADOPTION (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended		9 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018	Oct. 01, 2018	Sep. 30, 2018
Statement of Financial Position [Abstract]
Accounts and other receivables, net of allowance for doubtful accounts	$ 1,997		$ 1,997		$ 1,657	$ 1,965
Other current assets	2,138		2,138		1,637	950
Other current liabilities	1,687		1,687		413	54
Retained earnings	5,183		5,183		13,273	$ 13,253
Income Statement [Abstract]
Contracts drilling revenue	3,392	$ 3,122	8,917	$ 6,862
Loss before equity in loss of affiliates and income taxes	(1,230)	(393)	(7,808)	(837)
Loss before income taxes	(1,489)	(257)	(8,353)	(934)
Net loss	(1,398)	(94)	(8,122)	(465)
Less: Net (loss) earnings attributable to non-controlling interests	(33)	280	(32)	247
Net loss attributable to Barnwell Industries, Inc. stockholders	$ (1,365)	$ (374)	$ (8,090)	$ (712)
Basic and diluted net loss per common share attributable to Barnwell Industries, Inc. stockholders (in dollars per share)	$ (0.16)	$ (0.05)	$ (0.98)	$ (0.09)
Calculated under revenue guidance in effect before Topic 606 | Accounting Standards Update 2014-09
Statement of Financial Position [Abstract]
Accounts and other receivables, net of allowance for doubtful accounts	$ 2,450		$ 2,450		1,965
Other current assets	1,248		1,248		950
Other current liabilities	1,302		1,302		54
Retained earnings	5,131		5,131		13,253
Income Statement [Abstract]
Loss before equity in loss of affiliates and income taxes	(1,267)		(7,840)
Loss before income taxes	(1,526)		(8,385)
Net loss	(1,435)		(8,154)
Less: Net (loss) earnings attributable to non-controlling interests	(33)		(32)
Net loss attributable to Barnwell Industries, Inc. stockholders	$ (1,402)		$ (8,122)
Basic and diluted net loss per common share attributable to Barnwell Industries, Inc. stockholders (in dollars per share)	$ (0.17)		$ (0.98)
Difference between revenue guidance in effect before and after Topic 606 | Accounting Standards Update 2014-09
Statement of Financial Position [Abstract]
Accounts and other receivables, net of allowance for doubtful accounts	$ (453)		$ (453)		(308)
Other current assets	890		890		687
Other current liabilities	385		385		359
Retained earnings	52		52		$ 20
Income Statement [Abstract]
Loss before equity in loss of affiliates and income taxes	37		32
Loss before income taxes	37		32
Net loss	37		32
Less: Net (loss) earnings attributable to non-controlling interests	0		0
Net loss attributable to Barnwell Industries, Inc. stockholders	$ 37		$ 32
Basic and diluted net loss per common share attributable to Barnwell Industries, Inc. stockholders (in dollars per share)	$ 0.01		$ 0.00
Contract drilling
Income Statement [Abstract]
Contracts drilling revenue	$ 1,689	$ 1,193	$ 3,839	$ 3,051
Contract drilling operating expense	1,242	$ 1,074	3,789	$ 2,778
Contract drilling | Calculated under revenue guidance in effect before Topic 606 | Accounting Standards Update 2014-09
Income Statement [Abstract]
Contracts drilling revenue	1,783		3,201
Contract drilling operating expense	1,373		3,183
Contract drilling | Difference between revenue guidance in effect before and after Topic 606 | Accounting Standards Update 2014-09
Income Statement [Abstract]
Contracts drilling revenue	(94)		638
Contract drilling operating expense	$ (131)		$ 606