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Accumulated Other Comprehensive Loss Accumulated Other Comprehensive Loss Reclassifications from AOCL (Details) - Accumulated Defined Benefit Plans Adjustment Attributable to Parent [Member] - Reclassification out of Accumulated Other Comprehensive Income [Member] - USD ($) $ in Thousands | 12 Months Ended
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Dec. 31, 2019 | Dec. 31, 2018 | Dec. 31, 2017
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items] |  |  |
Other Comprehensive (Income) Loss, Defined Benefit Plan, Prior Service Cost (Credit), Reclassification Adjustment from AOCI, before Tax | $ (794) | $ (904) | $ (4,381)
Other Comprehensive Income (Loss), Defined Benefit Plan, Gain (Loss), Reclassification Adjustment from AOCI, before Tax | 17,074 | (15,554) | 36,833
Other Comprehensive Income Loss Adjustment From AOCI Pension And Other Postretirement Benefit Plans For Net Prior Service Cost , Adjustment Due to Effects of Regulation | (19,309) | 18,947 | (33,255)
Other Comprehensive (Income) Loss, Defined Benefit Plan, Reclassification Adjustment from AOCI, before Tax | (3,029) | 2,489 | (803)
Other Comprehensive (Income) Loss, Defined Benefit Plan, Reclassification Adjustment from AOCI, Tax | 636 | (523) | 281
Other Comprehensive (Income) Loss, Defined Benefit Plan, Reclassification Adjustment from AOCI, after Tax | $ (2,393) | $ 1,966 | $ (522)

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