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New Accounting Standards New Accounting Standards (Details) - USD ($) $ in Thousands | 3 Months Ended | 12 Months Ended
--- | --- | ---
Mar. 31, 2018 | Dec. 31, 2018
Error Corrections and Prior Period Adjustments Restatement [Line Items] |  |
Reclassification of income tax effect related to tax reform | $ 0 |
Accounting Standards Update 2017-07 |  |
Error Corrections and Prior Period Adjustments Restatement [Line Items] |  |
Net periodic benefit cost (credit) | (4,000) |
Accounting Standards Update 2017-07 | Scenario, Forecast |  |
Error Corrections and Prior Period Adjustments Restatement [Line Items] |  |
Net periodic benefit cost (credit) |  | $ (15,000)
Accounting Standards Update 2018-02 |  |
Error Corrections and Prior Period Adjustments Restatement [Line Items] |  |
Reclassification of income tax effect related to tax reform | 9,000 |
Accounting Standards Update 2018-02 | Arizona Public Service Company |  |
Error Corrections and Prior Period Adjustments Restatement [Line Items] |  |
Reclassification of income tax effect related to tax reform | $ 5,000 |

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- Definition Tax Cuts and Jobs Act of 2017, Reclassification from AOCI to Retained Earnings, Tax Effect + References No definition available. + Details
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- Definition Amount of net periodic benefit cost (credit) for defined benefit plan. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 715 -SubTopic 20 -Section 50 -Paragraph 1 -Subparagraph (h) -URI http://asc.fasb.org/extlink&oid=82843861&loc=d3e1928-114920 + Details
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