ACCUMULATED OTHER COMPREHENSIVE INCOME (LOSS) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Other Comprehensive (Income) Loss Before Reclassification, Retirement and Other Postretirement Benefit Plan Obligations	$ (19,490)	$ (8,116)
Other Comprehensive Income (Loss) Before Reclassification, Risk-Management Assets/Liabilities of Unconsolidated Affiliates	(7,275)	2,396
Other comprehensive income (loss) before reclassifications	(174,568)	(11,393)
Other Comprehensive Income (Loss), Risk-Management Assets/Liabilities, after Reclassification Adjustment, after Tax	(168,860)
Change in fair value of derivatives, net of tax	(147,803)	(5,673)	$ (21,408)
Other comprehensive Income (Loss) Reclassification Adjustment from AOCI for Risk-Management Assets/Liabilities, Net of Tax	(21,057)	36,870	63,687
Other Comprehensive Income (Loss), Reclassification Adjustment from AOCI for Other Comprehensive Income Attributable to Unconsolidated Affiliates, Net of Tax	(70)	(28)
Other comprehensive Income (Loss), Reclassification Adjustment included in Net Income, Net of Tax	(11,193)	49,785	53,867
Other Comprehensive Income (Loss), Risk-management Assets/Liabilities, after Reclassification, Adjustment, Net of Tax, Portion Attributable to Parent		31,197
Other Comprehensive (Income) Loss, Retirement and Other Postretirement Benefit Plans, after Reclassification Adjustment, after Tax	(9,696)	4,771	(4,175)
Other comprehensive income (loss) Risk-Management Assets/Liabilities of unconsolidated affiliates	(7,205)	2,424	(970)
Other Comprehensive Income (Loss), Net of Tax	(185,761)	38,392	37,134
Other Comprehensive Income (Loss), Net of Tax, Portion Attributable to Parent		38,392
Impact of Adoption of ASU 2018-02 on Unrealized Gains (Losses) on Risk Management Assets/Liabilities		(17,020)
Impact of Adoption of ASU 2018-02 on Retirement and Other Postretirement Benefit Plan Obligations		(20,340)
Impact of Adoption of ASU 2018-02 on Unrealized Gains (Losses) on Risk Management Assets/Liabilities of Unconsolidated Affiliates		(741)
Impact of Adoption of ASU 2018-02 on AOCI, Total		(38,101)
Risk management assets/liabilities - December 31	(233,520)	(64,660)	(81,915)
Retirement and Other Postretirement Benefit Plan Obligations - December 31	(131,481)	(121,785)	(105,411)
Risk-management assets/liabilities of unconsolidated affiliates - December 31	(8,999)	(1,794)	(1,204)
Accumulated other comprehensive loss - December 31	(374,000)	(188,239)	(188,530)
Beginning balance adjustments on Risk management assets/liabilities			3,078
Beginning balance adjustments on retirement and other postretirement benefit plan obligations			(805)
Beginning balance adjustments on risk-management asset/liabilities of unconsolidated affiliates			(2,273)
Beginning balance adjustments on accumulated other comprehensive loss			0
Reclassification Adjustment from AOCI on Risk Management Assets/Liabilities, Income Tax	(6,058)	11,013	26,899
Price Risk Cash Flow Hedge Unrealized Gain (Loss) to be Reclassified During Next 12 Months	28,900
Commodity Cash Flow Hedge Gain (Loss) To Be Reclassified After Next 12 Months Net	(800)
Interest Rate Cash Flow Hedge Gain (Loss) to be Reclassified During Next 12 Months, Net	(20,300)
Accumulated Net Gain (Loss) from Cash Flow Hedges Attributable to Parent [Member]
Other comprehensive Income (Loss) Reclassification Adjustment from AOCI for Risk-Management Assets/Liabilities, Net of Tax			45,541
Accumulated Net Gain (Loss) from Cash Flow Hedges Attributable to Parent [Member] | Sales [Member] | Commodity Contract [Member]
Derivative Instruments, Gain (Loss) Reclassified from Accumulated OCI into Income	50,345	(29,596)	(69,561)
Accumulated Net Gain (Loss) from Cash Flow Hedges Attributable to Parent [Member] | Interest Expense [Member] | Interest Rate Contracts
Derivative Instruments, Gain (Loss) Reclassified from Accumulated OCI into Income	(23,230)	(18,287)	(21,025)
Accumulated Net Gain (Loss) from Cash Flow Hedges Attributable to Parent [Member] | Total before tax [Member]
Derivative Instruments, Gain (Loss) Reclassified from Accumulated OCI into Income	27,115	(47,883)	(90,586)
Accumulated Net Gain (Loss) from Cash Flow Hedges Attributable to Parent [Member] | Tax Expense [Member]
Reclassification Adjustment from AOCI on Risk Management Assets/Liabilities, Income Tax	(6,058)	11,013	26,899
Accumulated Net Gain (Loss) from Cash Flow Hedges Attributable to Parent [Member] | Net of tax [Member]
Other comprehensive Income (Loss) Reclassification Adjustment from AOCI for Risk-Management Assets/Liabilities, Net of Tax	(21,057)	36,870	63,687
Accumulated Net Gain (Loss) from Cash Flow Hedges Attributable to Parent [Member] | Net income attributable to noncontrolling interest [Member]
Reclassification Adjustment from AOCI on Risk Management Assets/Liabilities Net of Tax, Portion Attributable to Noncontrolling Interest	0	0	(18,146)
Accumulated Retirement and Other Postretirement Benefit Plans Adjustment Attributable to Parent [Member]
Other Comprehensive (Income) Loss, Retirement and Other Postretirement Benefit Plans, Reclassification Adjustment from AOCI, After Tax	(9,794)	(12,887)	(8,162)
Retirement and Other Postretirement Benefit Plans, Amortization of Gain (Loss)	(12,946)	(18,398)	(15,265)
Retirement and Other Postretirement Benefit Plans, Amortization of Prior Service Credit	227	1,662	1,662
Reclassification Adjustment from AOCI, before Tax, Retirement and Other Postretirement Benefit Plans, Gain (Loss)	(12,719)	(16,736)	(13,603)
Reclassification Adjustment from AOCI, Tax, Retirement and Other Postretirement Benefit Plans, Gain (Loss)	2,925	3,849	5,441
Accumulated Other Comprehensive Income from Investments in Unconsolidated Affiliates Attributable to Parent [Member]
Other Comprehensive Income (Loss), Reclassification Adjustment from AOCI for Other Comprehensive Income Attributable to Unconsolidated Affiliates, Net of Tax	(70)	(28)	(164)
Reclassification Adjustment from AOCI, Before Tax, Portion Attributable to Unconsolidated Affiliates	(91)	(36)	(367)
Reclassification Adjustment from AOCI, Tax, Portion Attributable to Unconsolidated Affiliates	21	8	97
Accumulated Other Comprehensive Income from Investments in Unconsolidated Affiliates Attributable to Parent [Member] | Net of tax [Member]
Other Comprehensive Income (Loss), Reclassification Adjustment from AOCI for Other Comprehensive Income Attributable to Unconsolidated Affiliates, Net of Tax	(70)	(28)	(270)
Reclassification Adjustment from AOCI, Net of Tax, Portion Attributable to Noncontrolling Interests	0	0	(106)
AOCI Attributable to Parent [Member]
Other Comprehensive Income (Loss), Net of Tax	(185,761)	38,392	6,108
Cash Flow Hedging [Member]
Derivative Instruments, Gain (Loss) Reclassified from Accumulated OCI into Income	27,115	(47,883)	(90,586)
Cash Flow Hedging [Member] | Commodity Contract [Member]
Unrealized Gain Loss On Cash Flow Hedges Net Of Tax Accumulated Other Comprehensive Income Loss	28,119
Cash Flow Hedging [Member] | Interest Rate Contracts
Amount of accumulated other comprehensive income (loss) attributable primarily to settled interest-rate swaps.	(106,592)
Cash Flow Hedging [Member] | Forward Contracts [Member]
Amount of accumulated other comprehensive income (loss) attributable primarily to forward starting interest-rate swaps.	(155,047)
Cash Flow Hedging [Member] | Sales [Member] | Commodity Contract [Member]
Derivative Instruments, Gain (Loss) Reclassified from Accumulated OCI into Income	50,345	(29,596)	(69,561)
Cash Flow Hedging [Member] | Interest Expense [Member] | Interest Rate Contracts
Derivative Instruments, Gain (Loss) Reclassified from Accumulated OCI into Income	$ (23,230)	$ (18,287)	$ (21,025)