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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, 2018 | Sep. 30, 2017 | Sep. 30, 2018 | Sep. 30, 2017
Unrealized gains (losses) on risk management assets/liabilities - January 1 |  |  | $ (81,915) |
Pension and Postretirement Benefit Plan Obligations - January 1 |  |  | (105,411) |
Unrealized gains (losses) on risk-management assets/liabilities of unconsolidated affiliates - January 1 |  |  | (1,204) |
Accumulated other comprehensive loss - January 1 |  |  | (188,530) |
Other Comprehensive Income (Loss) Before Reclassifications, Unrealized Gains (Losses) on Risk-Management Assets/Liabilities |  |  | 10,729 |
Other Comprehensive (Income) Loss Before Reclassification, Pension and Postretirement Benefit Plan Obligations |  |  | (563) |
Other Comprehensive Income (Loss) Before Reclassification, Unrealized Gains (Losses) on Risk-Management Assets/Liabilities of Unconsolidated Affiliates |  |  | 5,336 |
Other comprehensive income (loss) before reclassifications |  |  | 15,502 |
Other Comprehensive Income (Loss) Reclassification Adjustment from AOCI for Unrealized Gains (Losses) on Risk-Management Assets/Liabilities, Net of Tax | $ 19,261 | $ 13,062 | 43,397 | $ 40,272
Other Comprehensive Income (Loss), Reclassification Adjustment from AOCI for Other Comprehensive Income Attributable to Unconsolidated Affiliates, Net of Tax |  |  | (55) |
Other Comprehensive Income (Loss), Reclassification Adjustment included in Net Income, Net of Tax | 22,437 | 15,152 | 52,991 | 28,339
Other Comprehensive Income (Loss), Derivatives Qualifying as Hedges, Net of Tax, Portion Attributable to Parent |  |  | 54,126 |
Other Comprehensive (Income) Loss, Pension and Postretirement Benefit Plans, after Reclassification Adjustment, after Tax | 3,236 | 2,041 | 9,086 | 6,122
Other comprehensive income (loss) on investment in unconsolidated affiliates |  |  | 5,281 |
Other Comprehensive Income (Loss), Net of Tax | 20,451 | (5,686) | 68,493 | 43,893
Impact of Adoption of ASU 2018-02 On Unrealized Gains (Losses) on Risk Management Assets/Liabilities |  |  | (17,935) |
Impact of Adoption of ASU 2018-02 On Pension and Postretirement Benefit Plan Obligations |  |  | (20,166) |
Impact of Adoption of ASU 2018-02 On Unrealized Gains (Losses) on Risk Management Assets/Liabilities of Unconsolidated Affiliates |  |  | 0 |
Impact of Adoption of ASU 2018-02 on AOCI, Total |  |  | (38,101) |
Unrealized gains (losses) on risk management assets/liabilities - September 30 | (45,724) |  | (45,724) |
Pension and Postretirement Benefit Plan Obligations - September 30 | (116,491) |  | (116,491) |
Unrealized gains (losses) on risk-management assets/liabilities of unconsolidated affiliates - September 30 | 4,077 |  | 4,077 |
Accumulated other comprehensive loss - September 30 | (158,138) |  | (158,138) |
Reclassification Adjustment from AOCI on Risk Management Assets/Liabilities, Income Tax | 5,752 | 7,671 | 12,962 | 13,077
Accumulated Net Gain (Loss) from Cash Flow Hedges Attributable to Parent [Member] |  |  |  |
Other Comprehensive Income (Loss) Reclassification Adjustment from AOCI for Unrealized Gains (Losses) on Risk-Management Assets/Liabilities, Net of Tax | 19,261 | 13,062 | 43,397 | 22,126
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 | (20,630) | (15,913) | (42,430) | (38,028)
Accumulated Net Gain (Loss) from Cash Flow Hedges Attributable to Parent [Member] | Interest Expense [Member] | Interest Rate Contract [Member] |  |  |  |
Derivative Instruments, Gain (Loss) Reclassified from Accumulated OCI into Income | (4,383) | (4,820) | (13,929) | (15,321)
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 | (25,013) | (20,733) | (56,359) | (53,349)
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 | 5,752 | 7,671 | 12,962 | 13,077
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 Unrealized Gains (Losses) on Risk-Management Assets/Liabilities, Net of Tax | 19,261 | 13,062 | 43,397 | 40,272
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 | 0 | (18,146)
Accumulated Pension and Postretirement Benefit Plans Adjustment Attributable to Parent [Member] |  |  |  |
Other Comprehensive (Income) Loss, Pension and Postretirement Benefit Plans, Reclassification Adjustment from AOCI, After Tax | (3,216) | (2,038) | (9,649) | (6,114)
Pension and Postretirement Benefit Plans, Amortization of Gain (Loss) | (4,592) | (3,811) | (13,776) | (11,435)
Pension and Postretirement Benefit Plans, Amortization of Prior Service Cost (Credit) | 415 | 415 | 1,245 | 1,245
Reclassification Adjustment from AOCI, before Tax, Pension and Postretirement Benefit Plans, Gain (Loss) | (4,177) | (3,396) | (12,531) | (10,190)
Reclassification Adjustment from AOCI, Tax, Pensions and Postretirement Benefit Plans, Gain (Loss) | 961 | 1,358 | 2,882 | 4,076
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 | 40 | (52) | 55 | (99)
Reclassification Adjustment from AOCI, Before Tax, Portion Attributable to Unconsolidated Affiliates | 52 | (83) | 71 | (264)
Reclassification Adjustment from AOCI, Tax, Portion Attributable to Unconsolidated Affiliates | (12) | 31 | (16) | 59
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 | 40 | (52) | 55 | (205)
Reclassification Adjustment from AOCI, Net of Tax, Portion Attributable to Unconsolidated Affiliates | $ 0 | $ 0 | 0 | (106)
AOCI Attributable to Parent [Member] |  |  |  |
Other Comprehensive Income (Loss), Net of Tax |  |  | $ 68,493 | $ 12,867

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