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ACCUMULATED OTHER COMPREHENSIVE INCOME (LOSS) ACCUMULATED OTHER COMPREHENSIVE INCOME (Details) - USD ($) $ in Thousands	3 Months Ended						9 Months Ended
	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Sep. 30, 2019	Sep. 30, 2018
Risk management assets/liabilities - January 1			$ (64,660)				$ (64,660)
Retirement and Other Postretirement Benefit Plan Obligations - January 1			(121,785)				(121,785)
Risk-management assets/liabilities of unconsolidated affiliates - January 1			(1,794)				(1,794)
Accumulated other comprehensive loss - January 1			(188,239)				(188,239)
Change in fair value of derivatives, net of tax	$ (73,822)			$ (3,526)			(199,795)	$ 10,729
Other Comprehensive (Income) Loss Before Reclassification, Retirement and Postretirement Benefit Plan Obligations							(63)
Other Comprehensive Income (Loss) Before Reclassification, Risk-Management Assets/Liabilities of Unconsolidated Affiliates							(10,567)
Other comprehensive income (loss) before reclassifications							(210,425)
Other comprehensive Income (Loss) Reclassification Adjustment from AOCI for Risk-Management Assets/Liabilities, Net of Tax	(8,952)			19,261			(29,748)	43,397
Other Comprehensive Income (Loss), Reclassification Adjustment from AOCI for Other Comprehensive Income Attributable to Unconsolidated Affiliates, Net of Tax							26
Other comprehensive Income (Loss), Reclassification Adjustment included in Net Income, Net of Tax	(6,462)			22,437			(22,440)	52,991
Other Comprehensive Income (Loss), Risk-Management Assets/Liabilities, after Reclassification Adjustment, after Tax							(229,543)
Other Comprehensive (Income) Loss, Retirement and Other Postretirement Benefit Plans, after Reclassification Adjustment, after Tax	2,465			3,236			7,271	9,086
Other Comprehensive Income (Loss), Risk-Management Assets/Liabilities of Unconsolidated Affiliates	(4,399)			1,480			(10,593)	5,281
Other Comprehensive Income (Loss), Net of Tax	(84,708)	$ (66,872)	(81,285)	20,451	$ (3,897)	$ 51,939	(232,865)	68,493
Risk management assets/liabilities - September 30	(294,203)						(294,203)
Retirement and Other Postretirement Benefit Plan Obligations - September 30	(114,514)						(114,514)
Risk-management assets/liabilities of unconsolidated affiliates - September 30	(12,387)						(12,387)
Accumulated other comprehensive loss - September 30	(421,104)						(421,104)
Reclassification Adjustment from AOCI on Risk Management Assets/Liabilities, Income Tax	(2,673)			5,752			(8,654)	12,962
Price Risk Cash Flow Hedge Unrealized Gain (Loss) to be Reclassified During Next 12 Months	27,900						27,900
Commodity Cash Flow Hedge Gain (Loss) To Be Reclassified After Next 12 Months Net	2,400						2,400
Interest Rate Cash Flow Hedge Gain (Loss) to be Reclassified During Next 12 Months, Net	(19,700)						(19,700)
Accumulated Net Gain (Loss) from Cash Flow Hedges [Member] \| Sales [Member] \| Commodity contracts
Derivative Instruments, Gain (Loss) Reclassified from Accumulated OCI into Income, Net	18,528			(20,630)			52,624	(42,430)
Accumulated Net Gain (Loss) from Cash Flow Hedges [Member] \| Interest Expense [Member] \| Interest Rate Contract [Member]
Derivative Instruments, Gain (Loss) Reclassified from Accumulated OCI into Income, Net	(6,903)			(4,383)			(14,222)	(13,929)
Accumulated Net Gain (Loss) from Cash Flow Hedges [Member] \| Total before tax [Member]
Derivative instruments, Gain (Loss) Reclassified from Accumulated OCI into Income	11,625			(25,013)			38,402	(56,359)
Accumulated Net Gain (Loss) from Cash Flow Hedges [Member] \| Tax Expense [Member]
Reclassification Adjustment from AOCI on Risk Management Assets/Liabilities, Income Tax	(2,673)			5,752			(8,654)	12,962
Accumulated Net Gain (Loss) from Cash Flow Hedges [Member] \| Net of tax [Member]
Other comprehensive Income (Loss) Reclassification Adjustment from AOCI for Risk-Management Assets/Liabilities, Net of Tax	(8,952)			19,261			(29,748)	43,397
Accumulated Retirement and Other Postretirement Benefit Plans Adjustment [Member]
Other Comprehensive (Income) Loss, Retirement and Other Postretirement Benefit Plans, Reclassification Adjustment from AOCI, After Tax	(2,444)			(3,216)			(7,334)	(9,649)
Retirement and Other Postretirement Benefit Plans, Amortization of Gain (Loss)	(3,232)			(4,592)			(9,696)	(13,776)
Retirement and Other Postretirement Benefit Plans, Amortization of Prior Service Credit	57			415			171	1,245
Reclassification Adjustment from AOCI, before Tax, Retirement and Other Postretirement Benefit Plans, Gain (Loss)	(3,175)			(4,177)			(9,525)	(12,531)
Reclassification Adjustment from AOCI, Tax, Retirement and Other Postretirement Benefit Plans, Gain (Loss)	731			961			2,191	2,882
Accumulated Other Comprehensive Income from Investments in Unconsolidated Affiliates [Member]
Reclassification Adjustment from AOCI, Before Tax, Portion Attributable to Unconsolidated Affiliates	(59)			52			34	71
Reclassification Adjustment from AOCI, Tax, Portion Attributable to Unconsolidated Affiliates	13			(12)			(8)	(16)
Accumulated Other Comprehensive Income from Investments in Unconsolidated Affiliates [Member] \| Net of tax [Member]
Other Comprehensive Income (Loss), Reclassification Adjustment from AOCI for Other Comprehensive Income Attributable to Unconsolidated Affiliates, Net of Tax	(46)			40			26	55
AOCI [Member]
Other Comprehensive Income (Loss), Net of Tax	(84,708)	$ (66,872)	$ (81,285)	20,451	$ (3,897)	$ 51,939	(232,865)
Cash Flow Hedging [Member]
Derivative Instruments, Gain (Loss) Reclassified from Accumulated OCI into Income, Net	11,625			(25,013)			38,402	(56,359)
Cash Flow Hedging [Member] \| Commodity contracts
Unrealized Gain Loss On Cash Flow Hedges Net Of Tax Accumulated Other Comprehensive Income Loss	30,258						30,258
Cash Flow Hedging [Member] \| Interest Rate Contract [Member]
Amount of accumulated other comprehensive income (loss) attributable primarily to settled interest-rate swaps.	(111,275)						(111,275)
Cash Flow Hedging [Member] \| Forward Contracts [Member]
Amount of accumulated other comprehensive income (loss) attributable primarily to forward starting interest-rate swaps.	$ (213,186)						$ (213,186)
Cash Flow Hedging [Member] \| Sales [Member] \| Commodity contracts
Derivative Instruments, Gain (Loss) Reclassified from Accumulated OCI into Income, Net				(20,630)				(42,430)
Cash Flow Hedging [Member] \| Interest Expense [Member] \| Interest Rate Contract [Member]
Derivative Instruments, Gain (Loss) Reclassified from Accumulated OCI into Income, Net				$ (4,383)				$ (13,929)