LEASES - Right of use assets and lease liabilities (Details) - USD ($) $ in Thousands	3 Months Ended
	Dec. 31, 2019	Jun. 30, 2019	Sep. 30, 2019	Dec. 31, 2018
Lessee, Lease, Description [Line Items]
Right of use assets - long-term	$ 1,722			$ 0
Lease liabilities - current	412
Lease liabilities - long-term	1,323
Total lease liabilities	$ 1,735
Operating lease, liability, current, statement of financial position [Extensible List]	us-gaap:AccruedLiabilitiesCurrent
Operating lease, liability, noncurrent, statement of financial position [Extensible List]	llex:DerivativeLiabilityAndOtherLiabilitiesNoncurrent
Drilling Rig Lease
Lessee, Lease, Description [Line Items]
Right of use assets - long-term			$ 10,800
Total lease liabilities			$ 10,800
Write off of operating lease liability	$ 10,400	$ 5,400
Write off of operating lease, right-of-use asset	$ 10,400	$ 5,400