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ACCUMULATED OTHER COMPREHENSIVE INCOME (LOSS) ACCUMULATED OTHER COMPREHENSIVE INCOME (Details) - USD ($) $ in Thousands | 3 Months Ended | 6 Months Ended
--- | --- | ---
Jun. 30, 2018 | Jun. 30, 2017 | Jun. 30, 2018 | Jun. 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 |  |  | 14,255 |
Other Comprehensive (Income) Loss Before Reclassification, Pension and Postretirement Benefit Plan Obligations |  |  | (583) |
Other Comprehensive Income (Loss) Before Reclassification, Unrealized Gains (Losses) on Risk-Management Assets/Liabilities of Unconsolidated Affiliates |  |  | 3,816 |
Other comprehensive income (loss) before reclassifications |  |  | 17,488 |
Other Comprehensive Income (Loss) Reclassification Adjustment from AOCI for Unrealized Gains (Losses) on Risk-Management Assets/Liabilities, net of tax | $ 12,160 | $ 9,927 | 24,136 | $ 27,210
Other Comprehensive Income (Loss), Reclassification Adjustment from AOCI for Other Comprehensive Income Attributable to Unconsolidated Affiliates, Net of Tax |  |  | (15) |
Other Comprehensive Income (Loss), Reclassification Adjustment included in Net Income, Net of Tax | 15,326 | 5,466 | 30,554 | 13,187
Other Comprehensive Income (Loss), Derivatives Qualifying as Hedges, Net of Tax, Portion Attributable to Parent |  |  | 38,391 |
Other Comprehensive (Income) Loss, Pension and Postretirement Benefit Plans, after Reclassification Adjustment, after Tax | 3,235 | 2,040 | 5,850 | 4,081
Other comprehensive income (loss) on investment in unconsolidated affiliates |  |  | 3,801 |
Other Comprehensive Income (Loss), Net of Tax | (3,897) | 5,474 | 48,042 | 49,579
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 - June 30 | (61,459) |  | (61,459) |
Pension and Postretirement Benefit Plan Obligations - June 30 | (119,727) |  | (119,727) |
Unrealized gains (losses) on risk-management assets/liabilities of unconsolidated affiliates - June 30 | 2,597 |  | 2,597 |
Accumulated other comprehensive loss - June 30 | (178,589) |  | (178,589) |
Other Comprehensive Income (Loss), Reclassification Adjustment from AOCI on Risk Management Assets/Liabilities | 3,631 | 2,041 | 7,209 | 5,406
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 | 12,160 | 3,406 | 24,136 | 9,064
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 | (10,189) | (6,796) | (21,800) | (22,115)
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 | (5,602) | (5,172) | (9,545) | (10,501)
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 | (15,791) | (11,968) | (31,345) | (32,616)
Accumulated Net Gain (Loss) from Cash Flow Hedges Attributable to Parent [Member] | Tax Expense [Member] |  |  |  |
Other Comprehensive Income (Loss), Reclassification Adjustment from AOCI on Risk Management Assets/Liabilities | 3,631 | 2,041 | 7,209 | 5,406
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 | 12,160 | 9,927 | 24,136 | 27,210
Accumulated Net Gain (Loss) from Cash Flow Hedges Attributable to Parent [Member] | Net income attributable to noncontrolling interest [Member] |  |  |  |
Other Comprehensive Income (Loss), Derivatives Qualifying as Hedges, Net of Tax, Portion Attributable to Noncontrolling Interest | 0 | (6,521) | 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 | (3,217) | (2,038) | (6,433) | (4,076)
Pension and Postretirement Benefit Plans, Amortization of Gain (Loss) | (4,592) | (3,812) | (9,184) | (7,624)
Pension and Postretirement Benefit Plans, Amortization of Prior Service Cost (Credit) | 415 | 415 | 830 | 830
Other Comprehensive Income (Loss), Pension and Postretirement Benefit Plans, Gain (Loss), Reclassification Adjustment from AOCI, before Tax | (4,177) | (3,397) | (8,354) | (6,794)
Other Comprehensive Income (Loss), Pensions and Postretirement Benefit Plans, Gain (Loss), Reclassification Adjustment from AOCI, Tax | 960 | 1,359 | 1,921 | 2,718
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 | 51 | (22) | 15 | (47)
Other Comprehensive Income (Loss), Reclassification Adjustment from AOCI for Other Comprehensive Income Attributable to Unconsolidated Affiliates, Before Tax | 66 | (85) | 19 | (181)
Other Comprehensive Income (Loss), Reclassification Adjustment from AOCI for Other Comprehensive Income Attributable to Unconsolidated Affiliates, Tax | (15) | 13 | (4) | 28
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 | 51 | (72) | 15 | (153)
Other Comprehensive Income (Loss), Reclassification Adjustment from AOCI for Other Comprehensive Income Attributable to Unconsolidated Affiliates, Net of Tax, Portion Attributable to Noncontrolling Interests | $ 0 | $ (50) | 0 | (106)
AOCI Attributable to Parent [Member] |  |  |  |
Other Comprehensive Income (Loss), Net of Tax |  |  | $ 48,042 | $ 18,553

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