DEBT - Permian Transmission Credit Facility (Narrative) (Details) - USD ($)		3 Months Ended
Mar. 08, 2021	Mar. 31, 2021
Line of Credit Facility [Line Items]
Proceeds from secured lines of credit	$ 175,000,000.0
Borrowing capacity		$ 155,500
Debt Default Long term Debt Amount		$ 0
LIBOR
Line of Credit Facility [Line Items]
Applicable margin		2.625%
Stated interest rate		2.50%
Debt instrument interest rate		0.70%
LIBOR \| From and Including the Closing Date to and Excluding the Fifth Anniversary of the Closing Date
Line of Credit Facility [Line Items]
Applicable margin		2.375%
Unused portion of the Permian Transmission Credit facility		$ 157,500
Alternate base rate
Line of Credit Facility [Line Items]
Applicable margin		1.625%
Alternate base rate \| From and Including the Closing Date to and Excluding the Fifth Anniversary of the Closing Date
Line of Credit Facility [Line Items]
Applicable margin		1.375%
Term Loan Credit Facility
Line of Credit Facility [Line Items]
Proceeds from secured lines of credit	160,000,000.0
Working Capital Credit Facility
Line of Credit Facility [Line Items]
Proceeds from secured lines of credit	$ 15,000,000.0

Amount of outstanding long-term debt or borrowing associated with any securities or credit agreement for which there has been a default in principal, interest, sinking fund, or redemption provisions, or any breach of covenant that existed at the end of the period and subsequently has not been cured.

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 235
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.4-08.(c))
-URI http://asc.fasb.org/extlink&oid=120395691&loc=d3e23780-122690

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- Definition

Percentage points added to the reference rate to compute the variable rate on the debt instrument.

+ References

No definition available.

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- Definition

Description of a fee associated with the debt instrument, including a commitment fee on unborrowed portions of a lender's total contractual commitment.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02.22(b))
-URI http://asc.fasb.org/extlink&oid=120391452&loc=d3e13212-122682

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Contractual interest rate for funds borrowed, under the debt agreement.

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Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02.22(a)(1))
-URI http://asc.fasb.org/extlink&oid=120391452&loc=d3e13212-122682

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Amount of unused borrowing capacity under the long-term financing arrangement that is available to the entity as of the balance sheet date.

+ References

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- Definition

Amount of current borrowing capacity under the credit facility considering any current restrictions on the amount that could be borrowed (for example, borrowings may be limited by the amount of current assets), but without considering any amounts currently outstanding under the facility.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02.19(b),22(b))
-URI http://asc.fasb.org/extlink&oid=120391452&loc=d3e13212-122682

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Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

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The cash inflow from a contractual arrangement with the lender, including letter of credit, standby letter of credit and revolving credit arrangements, under which borrowings can be made up to a specific amount at any point in time with either short term or long term maturity that is collateralized (backed by pledge, mortgage or other lien in the entity's assets).

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 230
-SubTopic 10
-Section 45
-Paragraph 14
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=121586364&loc=d3e3255-108585

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