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Asset Retirement Obligations - Narrative (Details) - Arizona Public Service Company - USD ($) $ in Thousands | 3 Months Ended | 9 Months Ended
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Sep. 30, 2017 | Sep. 30, 2017
Asset Retirement Obligations |  |
Newly incurred liabilities |  | $ 22,211
Navajo Generating Station |  |
Asset Retirement Obligations |  |
Newly incurred liabilities | $ 22,000 |

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- Definition Amount of asset retirement obligations incurred during the period. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 410 -SubTopic 20 -Section 50 -Paragraph 1 -Subparagraph (c)(1) -URI http://asc.fasb.org/extlink&oid=6392692&loc=d3e7535-110849 + Details
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