RISK MANAGEMENT AND HEDGING ACTIVITIES USING DERIVATIVES Part 1 (Details) - USD ($)	Jun. 30, 2018	Dec. 31, 2017
Derivative, Fair Value [Line Items]
Assets	$ 53,717,000	$ 74,415,000
(Liabilities)	(67,467,000)	(58,749,000)
Derivative, Net Liability Position, Aggregate Fair Value	0
Derivatives designated as hedging instruments
Derivative, Fair Value [Line Items]
Assets	48,496,000	66,938,000
(Liabilities)	(62,286,000)	(51,438,000)
Derivatives not designated as hedging instruments
Derivative, Fair Value [Line Items]
Assets	5,221,000	7,477,000
(Liabilities)	(5,181,000)	(7,311,000)
Natural Gas Pipelines [Member]
Derivative, Fair Value [Line Items]
Derivative, Fair Value, Net	0	0
Other Current Assets [Member] \| Commodity contracts \| Financial contracts \| Derivatives designated as hedging instruments
Derivative, Fair Value [Line Items]
Assets	18,492,000	16,978,000
Other Current Assets [Member] \| Commodity contracts \| Financial contracts \| Derivatives not designated as hedging instruments
Derivative, Fair Value [Line Items]
Assets	5,221,000	7,477,000
Other Current Assets [Member] \| Commodity contracts \| Physical contracts \| Derivatives designated as hedging instruments
Derivative, Fair Value [Line Items]
Assets	0	0
Other Current Assets [Member] \| Interest-rate contracts \| Derivatives designated as hedging instruments
Derivative, Fair Value [Line Items]
Assets	0	1,330,000
Other Current Liabilities [Member] \| Commodity contracts \| Financial contracts \| Derivatives designated as hedging instruments
Derivative, Fair Value [Line Items]
(Liabilities)	(49,476,000)	(42,819,000)
Other Current Liabilities [Member] \| Commodity contracts \| Financial contracts \| Derivatives not designated as hedging instruments
Derivative, Fair Value [Line Items]
(Liabilities)	(5,181,000)	(7,311,000)
Other Current Liabilities [Member] \| Commodity contracts \| Physical contracts \| Derivatives designated as hedging instruments
Derivative, Fair Value [Line Items]
(Liabilities)	(1,854,000)	(4,781,000)
Other Current Liabilities [Member] \| Interest-rate contracts \| Derivatives designated as hedging instruments
Derivative, Fair Value [Line Items]
(Liabilities)	0	0
Other Assets [Member] \| Commodity contracts \| Financial contracts \| Derivatives designated as hedging instruments
Derivative, Fair Value [Line Items]
Assets	408,000	0
Other Assets [Member] \| Interest-rate contracts \| Derivatives designated as hedging instruments
Derivative, Fair Value [Line Items]
Assets	29,596,000	48,630,000
Other Liabilities [Member] \| Commodity contracts \| Financial contracts \| Derivatives designated as hedging instruments
Derivative, Fair Value [Line Items]
(Liabilities)	(5,666,000)	(3,838,000)
Other Liabilities [Member] \| Interest-rate contracts \| Derivatives designated as hedging instruments
Derivative, Fair Value [Line Items]
(Liabilities)	$ (5,290,000)	$ 0

Fair value, before effects of master netting arrangements, of a financial asset or other contract with one or more underlyings, notional amount or payment provision or both, and the contract can be net settled by means outside the contract or delivery of an asset. Includes assets elected not to be offset. Excludes assets not subject to a master netting arrangement.

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Fair value of the assets less the liabilities of a derivative or group of derivatives.

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The aggregate fair value amounts of derivative instruments that contain credit-risk-related contingent features that are in a net liability position at the end of the reporting period. For nonderivative instruments that are designated and qualify as hedging instruments, the fair value amounts are the carrying value of the nonderivative hedging instrument, including the adjustment for the foreign currency transaction gain (loss) on that instrument.

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