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Commitments and Contingencies - Environmental Matters and Financial Assurances (Details) $ in Millions |  | 9 Months Ended
--- | --- | ---
May. 23, 2013 USD ($) | Sep. 30, 2015 USD ($) Letter_of_credit
Four Corners | New Mexico Tax Matter |  |
Environmental Matters |  |
Coal severance surtax, penalty, and interest | $ 30 |
Arizona Public Service Company | Letters of Credit Expiring in 2016 |  |
Financial Assurances |  |
Number of letters of credit expiring | Letter_of_credit |  | 2
Arizona Public Service Company | Letters of Credit Expiring in 2017 |  |
Financial Assurances |  |
Number of letters of credit expiring | Letter_of_credit |  | 1
Arizona Public Service Company | Letter of Credit |  |
Financial Assurances |  |
Outstanding letters of credit |  | $ 76
Arizona Public Service Company | Equity Lessors in Palo Verde sale leaseback transactions |  |
Financial Assurances |  |
Outstanding letters of credit |  | 5
Arizona Public Service Company | Natural gas tolling contract obligations |  |
Financial Assurances |  |
Outstanding letters of credit |  | $ 35
Arizona Public Service Company | Four Corners | New Mexico Tax Matter |  |
Environmental Matters |  |
Share of the assessment | $ 12 |
Regional Haze Rules | Arizona Public Service Company | Four Corners Units 4 and 5 |  |
Environmental Matters |  |
Percentage of share of cost of control |  | 63.00%
Expected environmental cost |  | $ 400
Regional Haze Rules | Arizona Public Service Company | Natural gas tolling contract obligations | Four Corners Units 4 and 5 |  |
Environmental Matters |  |
Additional percentage share of cost of control |  | 7.00%
Regional Haze Rules | Arizona Public Service Company | Four Corners | Four Corners Units 4 and 5 |  |
Environmental Matters |  |
Site contingency increase in loss exposure not accrued, best estimate |  | $ 45
Regional Haze Rules | Arizona Public Service Company | Navajo Plant |  |
Environmental Matters |  |
Expected environmental cost |  | 200
Regional Haze Rules | Arizona Public Service Company | Cholla |  |
Environmental Matters |  |
Expected environmental cost |  | 100
Mercury and air toxic standards (MATS) | Arizona Public Service Company | Navajo Plant |  |
Environmental Matters |  |
Expected environmental cost |  | 1
Mercury and air toxic standards (MATS) | Arizona Public Service Company | Cholla |  |
Environmental Matters |  |
Expected environmental cost |  | 11
Coal combustion waste | Arizona Public Service Company | Four Corners |  |
Environmental Matters |  |
Site contingency increase in loss exposure not accrued, best estimate |  | 15
Coal combustion waste | Arizona Public Service Company | Navajo Plant |  |
Environmental Matters |  |
Site contingency increase in loss exposure not accrued, best estimate |  | 1
Coal combustion waste | Arizona Public Service Company | Cholla |  |
Environmental Matters |  |
Site contingency increase in loss exposure not accrued, best estimate |  | $ 85

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