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Regulatory Matters - Schedule of Regulatory Assets (Details) - USD ($) $ in Thousands | Mar. 31, 2018 | Dec. 31, 2017
--- | --- | ---
Detail of regulatory assets |  |
Regulatory assets, current | $ 253,075 | $ 248,088
Regulatory assets, non-current | 1,200,260 | 1,202,302
Pension |  |
Detail of regulatory assets |  |
Regulatory assets, current | 0 | 0
Regulatory assets, non-current | 569,784 | 576,188
Retired power plant costs |  |
Detail of regulatory assets |  |
Regulatory assets, current | 26,668 | 27,402
Regulatory assets, non-current | 180,298 | 188,843
Income taxes — allowance for funds used during construction (AFUDC) equity |  |
Detail of regulatory assets |  |
Regulatory assets, current | 3,818 | 3,828
Regulatory assets, non-current | 143,619 | 142,852
Deferred fuel and purchased power — mark-to-market (Note 7) |  |
Detail of regulatory assets |  |
Regulatory assets, current | 62,069 | 52,100
Regulatory assets, non-current | 45,788 | 34,845
Deferred fuel and purchased power (b) (d) |  |
Detail of regulatory assets |  |
Regulatory assets, current | 74,585 | 75,637
Regulatory assets, non-current | 0 | 0
Four Corners cost deferral |  |
Detail of regulatory assets |  |
Regulatory assets, current | 8,077 | 8,077
Regulatory assets, non-current | 46,285 | 48,305
Income taxes — investment tax credit basis adjustment |  |
Detail of regulatory assets |  |
Regulatory assets, current | 1,066 | 1,066
Regulatory assets, non-current | 26,198 | 26,218
Lost fixed cost recovery (b) |  |
Detail of regulatory assets |  |
Regulatory assets, current | 54,384 | 59,844
Regulatory assets, non-current | 0 | 0
Palo Verde VIEs (Note 6) |  |
Detail of regulatory assets |  |
Regulatory assets, current | 0 | 0
Regulatory assets, non-current | 19,550 | 19,395
Deferred compensation |  |
Detail of regulatory assets |  |
Regulatory assets, current | 0 | 0
Regulatory assets, non-current | 37,650 | 36,413
Deferred property taxes |  |
Detail of regulatory assets |  |
Regulatory assets, current | 8,569 | 8,569
Regulatory assets, non-current | 73,244 | 74,926
Loss on reacquired debt |  |
Detail of regulatory assets |  |
Regulatory assets, current | 1,637 | 1,637
Regulatory assets, non-current | 14,896 | 15,305
Tax expense of Medicare subsidy |  |
Detail of regulatory assets |  |
Regulatory assets, current | 1,235 | 1,236
Regulatory assets, non-current | 7,387 | 7,415
Transmission cost adjustor |  |
Detail of regulatory assets |  |
Regulatory assets, current | 6,867 | 1,220
Regulatory assets, non-current | 0 | 0
AG-1 deferral |  |
Detail of regulatory assets |  |
Regulatory assets, current | 2,654 | 2,654
Regulatory assets, non-current | 7,809 | 8,472
Mead-Phoenix transmission line CIAC |  |
Detail of regulatory assets |  |
Regulatory assets, current | 332 | 332
Regulatory assets, non-current | 10,293 | 10,376
Coal reclamation |  |
Detail of regulatory assets |  |
Regulatory assets, current | 1,068 | 1,068
Regulatory assets, non-current | 12,468 | 12,396
Other |  |
Detail of regulatory assets |  |
Regulatory assets, current | 46 | 3,418
Regulatory assets, non-current | $ 4,991 | $ 353

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