LEASES, COMMITMENTS AND CONTINGENCIES - Narrative (Details)	1 Months Ended	3 Months Ended	9 Months Ended	12 Months Ended
	Mar. 31, 2019 USD ($) MMcf	Jun. 30, 2019 USD ($)	Sep. 30, 2019 USD ($) Agreement	Dec. 31, 2015 USD ($)
Loss Contingencies [Line Items]
Finance leases, term of contract			3 years
Lessee, operating lease, existence of residual value guarantee [true false]			false
Lessee, operating lease, residual value guarantee, Description			Our leases do not contain residual value guarantees.
Lessee, operating lease, assumptions and judgments, whether contract is or contains lease			Our significant assumptions or judgments include the determination of whether a contract contains a lease and the discount rate used in our lease liabilities.
Lessee, operating lease, assumptions and judgments, discount rate, description			The rate implicit in our lease contracts is not readily determinable. In determining the discount rate used in our lease liabilities, we analyzed certain factors in our incremental borrowing rate, including collateral assumptions and the term used. Our incremental borrowing rate on the Revolving Credit Facility was 5.03% at December 31, 2018, which reflects the fixed rate at which we could borrow a similar amount, for a similar term and with similar collateral as in the lease contracts at the commencement date.
Electric power | MMcf	60
Cost of project	$ 7,800,000
Up front payment included in property, plant and equipment	$ 3,000,000.0
Letter of credit initial term		1 year
Irrevocable letter of credit payable		$ 9,100,000
Letter of credit renew term		12 months
Transmission Line
Loss Contingencies [Line Items]
Additional cost to increase transmission line capacity		$ 4,300,000
Revolving credit facility
Loss Contingencies [Line Items]
Finance operating Lease obligations not exceed consolidated total assets			$ 50,000,000
Percentage of operating lease incremental borrowing rate			5.03%
Irrevocable letter of credit payable			$ 9,100,000
Office Space
Loss Contingencies [Line Items]
Lessee, operating lease, existence of option to extend [true false]			true
Lessee, operating lease, option to extend			We have options to extend the lease term of certain office space in Texas, Colorado and West Virginia. The beginning of the noncancelable lease period for these leases range from 2014 to 2018 and the lease period ends between 2020 and 2028. These lease agreements contain between one and three options to renew the lease for a period of between two and five years. As of September 30, 2019, the exercise of the renewal options for these leases are not reasonably certain and, as a result, the payments associated with these renewals are not included in the measurement of the lease liability and ROU asset.
Equipment
Loss Contingencies [Line Items]
Lessee, operating lease, option to extend			We also have options to extend the lease term of certain compression equipment used at the Summit Utica gathering system. The beginning of the noncancelable lease period for these leases is 2017 and the lease period ends in 2020. Upon expiration of the noncancelable lease period, we have the option to renew the leases on a month-to-month basis; we therefore have not included any amounts attributable to renewals in the measurement.
Minimum | Office Space
Loss Contingencies [Line Items]
Operating leases, term of contract			3 years
Operating lease, number of renewal terms | Agreement			1
Lease agreements renewal periods			2 years
Minimum | Equipment
Loss Contingencies [Line Items]
Operating leases, term of contract			3 years
Maximum | Meadowlark Midstream Gathering System | Principal Owner
Loss Contingencies [Line Items]
Coverage from pollution liability insurance policy			$ 25,000,000.0	$ 25,000,000.0
Coverage from property and business interruption insurance policy			$ 200,000,000.0
Maximum | Office Space
Loss Contingencies [Line Items]
Operating leases, term of contract			10 years
Operating lease, number of renewal terms | Agreement			3
Lease agreements renewal periods			5 years
Maximum | Equipment
Loss Contingencies [Line Items]
Operating leases, term of contract			4 years