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Regulatory Matters (Tables) | 9 Months Ended
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Sep. 30, 2017
Regulated Operations [Abstract] |
Schedule of changes in the deferred fuel and purchased power regulatory asset | The following table shows the changes in the deferred fuel and purchased power regulatory asset (liability) for 2017 and 2016 (dollars in thousands):
| Nine Months Ended September 30,
| 2017 |  | 2016
Beginning balance | $ | 12,465 |  |  | $ | (9,688 | )
Deferred fuel and purchased power costs — current period | 43,348 |  |  | 46,185 |
Amounts refunded/(charged) to customers | 18,153 |  |  | (28,365 | )
Ending balance | $ | 73,966 |  |  | $ | 8,132 |
Schedule of regulatory assets | The detail of regulatory assets is as follows (dollars in thousands):
| Amortization Through |  | September 30, 2017 |  | December 31, 2016
|  | Current |  | Non-Current |  | Current |  | Non-Current
Pension | (a) |  | $ | — |  |  | $ | 686,511 |  |  | $ | — |  |  | $ | 711,059 |
Retired power plant costs | Various |  | 28,647 |  |  | 194,639 |  |  | 9,913 |  |  | 117,591 |
Income taxes — allowance for funds used during construction ("AFUDC") equity | 2047 |  | 6,202 |  |  | 170,622 |  |  | 6,305 |  |  | 152,118 |
Deferred fuel and purchased power — mark-to-market (Note 6) | 2020 |  | 45,463 |  |  | 33,115 |  |  | — |  |  | 42,963 |
Deferred fuel and purchased power (b) (d) | 2018 |  | 73,966 |  |  | — |  |  | 12,465 |  |  | — |
Four Corners cost deferral | 2024 |  | 8,077 |  |  | 50,324 |  |  | 6,689 |  |  | 56,894 |
Income taxes — investment tax credit basis adjustment | 2046 |  | 2,120 |  |  | 53,225 |  |  | 2,120 |  |  | 54,356 |
Lost fixed cost recovery (b) | 2018 |  | 67,500 |  |  | — |  |  | 61,307 |  |  | — |
Palo Verde VIEs (Note 5) | 2046 |  | — |  |  | 19,240 |  |  | — |  |  | 18,775 |
Deferred compensation | 2036 |  | — |  |  | 37,265 |  |  | — |  |  | 35,595 |
Deferred property taxes | 2027 |  | 8,569 |  |  | 77,408 |  |  | — |  |  | 73,200 |
Loss on reacquired debt | 2038 |  | 1,637 |  |  | 15,715 |  |  | 1,637 |  |  | 16,942 |
Tax expense of Medicare subsidy | 2024 |  | 1,503 |  |  | 9,074 |  |  | 1,513 |  |  | 10,589 |
Demand Side Management | 2018 |  | — |  |  | — |  |  | 3,744 |  |  | — |
AG-1 deferral | 2022 |  | 2,654 |  |  | 9,136 |  |  | — |  |  | 5,868 |
Mead-Phoenix transmission line CIAC | 2050 |  | 332 |  |  | 10,459 |  |  | 332 |  |  | 10,708 |
Transmission cost adjustor (b) | 2018 |  | 4,345 |  |  | — |  |  | — |  |  | 1,588 |
Coal reclamation | 2026 |  | 1,068 |  |  | 14,446 |  |  | 418 |  |  | 5,182 |
Other | Various |  | 6,234 |  |  | — |  |  | 432 |  |  | — |
Total regulatory assets (c) |  |  | $ | 258,317 |  |  | $ | 1,381,179 |  |  | $ | 106,875 |  |  | $ | 1,313,428 |
(a) | See Note 4 for further discussion.
(b) | See "Cost Recovery Mechanisms" discussion above.
(c) | There are no regulatory assets for which the ACC has allowed recovery of costs, but not allowed a return by exclusion from rate base. FERC rates are set using a formula rate as described in "Transmission Rates, Transmission Cost Adjustor and Other Transmission Matters."
(d) | Subject to a carrying charge.
Schedule of regulatory liabilities | The detail of regulatory liabilities is as follows (dollars in thousands):
| Amortization Through |  | September 30, 2017 |  | December 31, 2016
|  | Current |  | Non-Current |  | Current |  | Non-Current
Asset retirement obligations | 2057 |  | $ | — |  |  | $ | 313,189 |  |  | $ | — |  |  | $ | 279,976 |
Removal costs | (a) |  | 37,756 |  |  | 184,512 |  |  | 29,899 |  |  | 223,145 |
Other postretirement benefits | (b) |  | 32,725 |  |  | 99,626 |  |  | 32,662 |  |  | 123,913 |
Income taxes — deferred investment tax credit | 2046 |  | 4,315 |  |  | 106,557 |  |  | 4,368 |  |  | 108,827 |
Income taxes — change in rates | 2046 |  | 2,565 |  |  | 67,136 |  |  | 1,771 |  |  | 70,898 |
Spent nuclear fuel | 2027 |  | 6,562 |  |  | 64,504 |  |  | — |  |  | 71,726 |
Renewable energy standard (c) | 2018 |  | 17,915 |  |  | — |  |  | 26,809 |  |  | — |
Demand side management (c) | 2019 |  | 12,175 |  |  | 4,921 |  |  | — |  |  | 20,472 |
Sundance maintenance | 2030 |  | — |  |  | 16,494 |  |  | — |  |  | 15,287 |
Deferred gains on utility property | 2022 |  | 4,525 |  |  | 11,875 |  |  | 2,063 |  |  | 8,895 |
Four Corners coal reclamation | 2031 |  | 1,857 |  |  | 19,494 |  |  | — |  |  | 18,248 |
Other | Various |  | 276 |  |  | 3,407 |  |  | 2,327 |  |  | 7,529 |
Total regulatory liabilities |  |  | $ | 120,671 |  |  | $ | 891,715 |  |  | $ | 99,899 |  |  | $ | 948,916 |
(a) | In accordance with regulatory accounting guidance, APS accrues for removal costs for its regulated assets, even if there is no legal obligation for removal.
(b) | See Note 4 for further discussion.
(c) | See "Cost Recovery Mechanisms" discussion above.

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- Definition Tabular disclosure of assets that are created when regulatory agencies permit public utilities to defer certain costs included in rate-setting to the balance sheet. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 980 -SubTopic 340 -Section 50 -Paragraph 2 -URI http://asc.fasb.org/extlink&oid=6499975&loc=d3e44264-110382 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 980 -SubTopic 715 -Section 50 -Paragraph 1 -URI http://asc.fasb.org/extlink&oid=6501251&loc=d3e52485-110419 Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 980 -SubTopic 340 -Section 50 -Paragraph 1 -URI http://asc.fasb.org/extlink&oid=6499975&loc=d3e44250-110382 + Details
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- Definition Tabular disclosure of regulatory liabilities. Detailed information about liabilities that result from rate actions of a regulator. Rate actions of a regulator can impose a liability on a regulated enterprise resulting in a regulatory liability. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 980 -SubTopic 405 -Section 25 -Paragraph 1 -URI http://asc.fasb.org/extlink&oid=6500807&loc=d3e48068-110394 + Details
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