REVENUE FROM CONTRACTS WITH CUSTOMERS REVENUE FROM CONTRACT WITH CUSTOMERS - IMPACT OF ADOPTION (Details) - USD ($) $ / shares in Units, $ in Thousands	12 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Oct. 01, 2018
Statement of Financial Position [Abstract]
Accounts and other receivables, net of allowance for doubtful accounts	$ 1,884	$ 1,965	$ 1,657
Other current assets	1,821	950	1,637
Other current liabilities	1,644	54	413
Retained earnings	859	13,253	13,273
Income Statement [Abstract]
Contracts drilling revenue	12,013	9,206
Loss before equity in loss of affiliates and income taxes	(12,372)	(2,242)
Loss before income taxes	(12,648)	(2,019)
Net loss	(12,417)	(1,418)
Less: Net (loss) earnings attributable to non-controlling interests	(3)	352
Net loss attributable to Barnwell Industries, Inc. stockholders	$ (12,414)	(1,770)
Basic and diluted net loss per common share attributable to Barnwell Industries, Inc. stockholders (in dollars per share)	$ (1.50)
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	$ 2,412		1,965
Other current assets	954		950
Other current liabilities	1,490		54
Retained earnings	674		13,253
Income Statement [Abstract]
Loss before equity in loss of affiliates and income taxes	(12,537)
Loss before income taxes	(12,813)
Net loss	(12,582)
Less: Net (loss) earnings attributable to non-controlling interests	(3)
Net loss attributable to Barnwell Industries, Inc. stockholders	$ (12,579)
Basic and diluted net loss per common share attributable to Barnwell Industries, Inc. stockholders (in dollars per share)	$ (1.52)
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	$ (528)		(308)
Other current assets	867		687
Other current liabilities	154		359
Retained earnings	185		$ 20
Income Statement [Abstract]
Loss before equity in loss of affiliates and income taxes	165
Loss before income taxes	165
Net loss	165
Less: Net (loss) earnings attributable to non-controlling interests	0
Net loss attributable to Barnwell Industries, Inc. stockholders	$ 165
Basic and diluted net loss per common share attributable to Barnwell Industries, Inc. stockholders (in dollars per share)	$ 0.02
Contract drilling
Income Statement [Abstract]
Contracts drilling revenue	$ 5,349	3,769
Contract drilling operating expense	4,973	$ 3,650
Contract drilling | Calculated under revenue guidance in effect before Topic 606 | Accounting Standards Update 2014-09
Income Statement [Abstract]
Contracts drilling revenue	4,711
Contract drilling operating expense	4,500
Contract drilling | Difference between revenue guidance in effect before and after Topic 606 | Accounting Standards Update 2014-09
Income Statement [Abstract]
Contracts drilling revenue	638
Contract drilling operating expense	$ 473