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RISK MANAGEMENT AND HEDGING ACTIVITIES USING DERIVATIVES - Part 2 (Details) $ in Millions	12 Months Ended
	Dec. 31, 2018 USD ($) MMcf MMBbls	Dec. 31, 2017 USD ($) MMcf MMBbls	Sep. 30, 2017 USD ($)
Derivative [Line Items]
Senior Notes, Noncurrent	$ 1,250.0		$ 1,200.0
Derivatives designated as hedging instruments | Futures and swaps | Natural gas (Bcf) | Fixed price | Purchased/Payor
Derivative [Line Items]
Notional amount | MMcf	0	0
Derivatives designated as hedging instruments | Futures and swaps | Natural gas (Bcf) | Fixed price | Sold/Receiver
Derivative [Line Items]
Notional amount | MMcf	(29,900)	(24,500)
Derivatives designated as hedging instruments | Futures and swaps | Natural gas (Bcf) | Basis | Purchased/Payor
Derivative [Line Items]
Notional amount | MMcf	0	0
Derivatives designated as hedging instruments | Futures and swaps | Natural gas (Bcf) | Basis | Sold/Receiver
Derivative [Line Items]
Notional amount | MMcf	(29,900)	(24,500)
Derivatives designated as hedging instruments | Futures, forwards and swaps | Crude oils and NGLs (MMBbl) | Fixed price | Purchased/Payor
Derivative [Line Items]
Notional amount | MMBbls	6.5	3.5
Derivatives designated as hedging instruments | Futures, forwards and swaps | Crude oils and NGLs (MMBbl) | Fixed price | Sold/Receiver
Derivative [Line Items]
Notional amount | MMBbls	(13.8)	(11.1)
Derivatives designated as hedging instruments | Interest Rate Contracts | Purchased/Payor
Derivative [Line Items]
Derivative, Notional Amount	$ 4,250.0	$ 1,750.0
Derivatives designated as hedging instruments | Interest Rate Contracts | Sold/Receiver
Derivative [Line Items]
Derivative, Notional Amount	$ 0.0	$ 0.0
Derivatives not designated as hedging instruments | Futures, forwards and swaps | Crude oils and NGLs (MMBbl) | Fixed price | Purchased/Payor
Derivative [Line Items]
Notional amount | MMBbls	0.0	0.8
Derivatives not designated as hedging instruments | Futures, forwards and swaps | Crude oils and NGLs (MMBbl) | Fixed price | Sold/Receiver
Derivative [Line Items]
Notional amount | MMBbls	0.0	(0.8)
LIBOR Based Interest Payments [Member] | Cash Flow Hedging [Member] | Forward contracts | Interest Rate Contracts
Derivative [Line Items]
Notional Amount Of Cash Flow Hedge Instruments Settled	$ 500.0
Derivative, Notional Amount	1,300.0	$ 500.0
Forecasted Debt Issuances [Member] | Cash Flow Hedging [Member] | Forward contracts | Interest Rate Contracts
Derivative [Line Items]
Notional Amount Of Cash Flow Hedge Instruments Settled	1,000.0
Derivative, Notional Amount	3,000.0	$ 1,300.0
Derivative, Notional Amount, New Contracts	$ 2,800.0

X

- Definition

Aggregate notional amount of derivative expressed in nonmonetary units. For example, the number of barrels specified in a fuel oil forward purchase contract.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher SEC
-Name Regulation S-X (SX)
-Number 210
-Article 12
-Section 13
-Sentence Column B

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Aggregate notional amount specified by the derivative(s). Expressed as an absolute value.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher SEC
-Name Regulation S-X (SX)
-Number 210
-Article 12
-Section 13
-Sentence Column B

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+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02.22)
-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

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