REVENUE FROM CONTRACTS WITH CUSTOMERS REVENUE FROM CONTRACT WITH CUSTOMERS - IMPACT OF ADOPTION (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended		6 Months Ended
	Mar. 31, 2019	Mar. 31, 2018	Mar. 31, 2019	Mar. 31, 2018	Oct. 01, 2018	Sep. 30, 2018
Statement of Financial Position [Abstract]
Accounts and other receivables, net of allowance for doubtful accounts	$ 2,066		$ 2,066		$ 1,657	$ 1,965
Other current assets	2,198		2,198		1,637	950
Other current liabilities	1,913		1,913		413	54
Retained earnings	6,548		6,548		13,273	$ 13,253
Income Statement [Abstract]
Contracts drilling revenue	987		2,150
Contract drilling operating expense	1,231	$ 883	2,547	$ 1,704
Loss before equity in loss of affiliates and income taxes	(1,979)	940	(6,578)	(444)
Loss before income taxes	(2,186)	860	(6,864)	(677)
Net loss	(2,151)	663	(6,724)	(371)
Less: Net (loss) earnings attributable to non-controlling interests	(26)	(16)	1	(33)
Net loss attributable to Barnwell Industries, Inc. stockholders	$ (2,125)	$ 679	$ (6,725)	$ (338)
Basic and diluted net (loss) earnings per common share attributable to Barnwell Industries, Inc. stockholders	$ (0.26)	$ 0.08	$ (0.81)	$ (0.04)
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	$ 2,443		$ 2,443		1,965
Other current assets	1,352		1,352		950
Other current liabilities	1,459		1,459		54
Retained earnings	6,533		6,533		13,253
Income Statement [Abstract]
Contracts drilling revenue	677		1,418
Contract drilling operating expense	917		1,810
Loss before equity in loss of affiliates and income taxes	(1,975)		(6,573)
Loss before income taxes	(2,182)		(6,859)
Net loss	(2,147)		(6,719)
Less: Net (loss) earnings attributable to non-controlling interests	(26)		1
Net loss attributable to Barnwell Industries, Inc. stockholders	$ (2,121)		$ (6,720)
Basic and diluted net (loss) earnings per common share attributable to Barnwell Industries, Inc. stockholders	$ (0.26)		$ (0.81)
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	$ (377)		$ (377)		(308)
Other current assets	846		846		687
Other current liabilities	454		454		359
Retained earnings	15		15		$ 20
Income Statement [Abstract]
Contracts drilling revenue	310		732
Contract drilling operating expense	314		737
Loss before equity in loss of affiliates and income taxes	(4)		(5)
Loss before income taxes	(4)		(5)
Net loss	(4)		(5)
Less: Net (loss) earnings attributable to non-controlling interests	0		0
Net loss attributable to Barnwell Industries, Inc. stockholders	$ (4)		$ (5)
Basic and diluted net (loss) earnings per common share attributable to Barnwell Industries, Inc. stockholders	$ 0.00		$ 0.00