REVENUE FROM CONTRACTS WITH CUSTOMERS REVENUE FROM CONTRACTS WITH CUSTOMERS - IMPACT OF ADOPTION (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Oct. 01, 2018	Sep. 30, 2018
Statement of Financial Position [Abstract]
Accounts and other receivables, net of allowance for doubtful accounts	$ 1,465		$ 1,657	$ 1,965
Other current assets	1,765		1,637	950
Other current liabilities	452		413	54
Retained earnings	8,673		13,273	$ 13,253
Income Statement [Abstract]
Contract drilling revenue	1,163
Contract drilling operating expense	1,316	$ 821
Loss before equity in loss of affiliates and income taxes	(4,599)	(1,384)
Loss before income taxes	(4,678)	(1,537)
Net loss	(4,573)	(1,034)
Less: Net earnings attributable to non-controlling interests	27	(17)
Net loss attributable to Barnwell Industries, Inc. stockholders	$ (4,600)	$ (1,017)
Basic and diluted net loss per common share attributable to Barnwell Industries, Inc. stockholders (in dollars per share)	$ (0.56)	$ (0.12)
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	$ 1,819		1,965
Other current assets	1,031		950
Other current liabilities	91		54
Retained earnings	8,654		13,253
Income Statement [Abstract]
Contract drilling revenue	741
Contract drilling operating expense	893
Loss before equity in loss of affiliates and income taxes	(4,598)
Loss before income taxes	(4,677)
Net loss	(4,572)
Less: Net earnings attributable to non-controlling interests	27
Net loss attributable to Barnwell Industries, Inc. stockholders	$ (4,599)
Basic and diluted net loss per common share attributable to Barnwell Industries, Inc. stockholders (in dollars per share)	$ (0.56)
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	$ (354)		(308)
Other current assets	734		687
Other current liabilities	361		359
Retained earnings	19		$ 20
Income Statement [Abstract]
Contract drilling revenue	422
Contract drilling operating expense	423
Loss before equity in loss of affiliates and income taxes	(1)
Loss before income taxes	(1)
Net loss	(1)
Less: Net earnings attributable to non-controlling interests	0
Net loss attributable to Barnwell Industries, Inc. stockholders	$ (1)
Basic and diluted net loss per common share attributable to Barnwell Industries, Inc. stockholders (in dollars per share)	$ 0.00