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Changes in Accumulated Other Comprehensive Loss (Details) - USD ($) $ in Thousands | 3 Months Ended
--- | ---
Mar. 31, 2018 | Mar. 31, 2017
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward] |  |
Balance at beginning of period | $ 5,135,730 | $ 4,935,912
Reclassification of income tax effect related to tax reform | 0 |
Balance at end of period | 5,153,671 | 4,965,940
Pension and Other Postretirement Benefits |  |
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward] |  |
Balance at beginning of period | (42,440) | (39,070)
OCI (loss) before reclassifications | 0 | 0
Amounts reclassified from accumulated other comprehensive loss | 900 | 522
Reclassification of income tax effect related to tax reform | (7,954) |
Balance at end of period | (49,494) | (38,548)
Derivative Instruments |  |
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward] |  |
Balance at beginning of period | (2,562) | (4,752)
OCI (loss) before reclassifications | (96) | (770)
Amounts reclassified from accumulated other comprehensive loss | 409 | 1,207
Reclassification of income tax effect related to tax reform | (598) |
Balance at end of period | (2,847) | (4,315)
Total |  |
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward] |  |
Balance at beginning of period | (45,002) | (43,822)
OCI (loss) before reclassifications | (96) | (770)
Amounts reclassified from accumulated other comprehensive loss | 1,309 | 1,729
Reclassification of income tax effect related to tax reform | (8,552) |
Balance at end of period | (52,341) | (42,863)
Arizona Public Service Company |  |
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward] |  |
Balance at beginning of period | 5,385,869 | 5,037,970
Balance at end of period | 5,401,512 | 5,067,052
Arizona Public Service Company | Pension and Other Postretirement Benefits |  |
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward] |  |
Balance at beginning of period | (24,421) | (20,671)
OCI (loss) before reclassifications | 0 | 0
Amounts reclassified from accumulated other comprehensive loss | 857 | 611
Reclassification of income tax effect related to tax reform | (4,440) |
Balance at end of period | (28,004) | (20,060)
Arizona Public Service Company | Derivative Instruments |  |
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward] |  |
Balance at beginning of period | (2,562) | (4,752)
OCI (loss) before reclassifications | (96) | (770)
Amounts reclassified from accumulated other comprehensive loss | 409 | 1,207
Reclassification of income tax effect related to tax reform | (598) |
Balance at end of period | (2,847) | (4,315)
Arizona Public Service Company | Total |  |
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward] |  |
Balance at beginning of period | (26,983) | (25,423)
OCI (loss) before reclassifications | (96) | (770)
Amounts reclassified from accumulated other comprehensive loss | 1,266 | 1,818
Reclassification of income tax effect related to tax reform | (5,038) |
Balance at end of period | $ (30,851) | $ (24,375)

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