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Changes in Accumulated Other Comprehensive Loss (Details) - USD ($) $ in Thousands | 12 Months Ended
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Dec. 31, 2017 | Dec. 31, 2016
Changes in accumulated other comprehensive income (loss) by component |  |
Beginning balance | $ 4,935,912 | $ 4,719,457
Ending balance | 5,135,730 | 4,935,912
Pension and Other Postretirement Benefits |  |
Changes in accumulated other comprehensive income (loss) by component |  |
Beginning balance | (39,070) | (37,593)
OCI (loss) before reclassifications | (6,438) | (4,509)
Amounts reclassified from accumulated other comprehensive loss | 3,068 | 3,032
Ending balance | (42,440) | (39,070)
Derivative Instruments |  |
Changes in accumulated other comprehensive income (loss) by component |  |
Beginning balance | (4,752) | (7,155)
OCI (loss) before reclassifications | (35) | (538)
Amounts reclassified from accumulated other comprehensive loss | 2,225 | 2,941
Ending balance | (2,562) | (4,752)
Total |  |
Changes in accumulated other comprehensive income (loss) by component |  |
Beginning balance | (43,822) | (44,748)
OCI (loss) before reclassifications | (6,473) | (5,047)
Amounts reclassified from accumulated other comprehensive loss | 5,293 | 5,973
Ending balance | (45,002) | (43,822)
ARIZONA PUBLIC SERVICE COMPANY |  |
Changes in accumulated other comprehensive income (loss) by component |  |
Beginning balance | 5,037,970 | 4,814,794
Ending balance | 5,385,869 | 5,037,970
ARIZONA PUBLIC SERVICE COMPANY | Pension and Other Postretirement Benefits |  |
Changes in accumulated other comprehensive income (loss) by component |  |
Beginning balance | (20,671) | (19,942)
OCI (loss) before reclassifications | (6,884) | (3,821)
Amounts reclassified from accumulated other comprehensive loss | 3,134 | 3,092
Ending balance | (24,421) | (20,671)
ARIZONA PUBLIC SERVICE COMPANY | Derivative Instruments |  |
Changes in accumulated other comprehensive income (loss) by component |  |
Beginning balance | (4,752) | (7,155)
OCI (loss) before reclassifications | (35) | (538)
Amounts reclassified from accumulated other comprehensive loss | 2,225 | 2,941
Ending balance | (2,562) | (4,752)
ARIZONA PUBLIC SERVICE COMPANY | Total |  |
Changes in accumulated other comprehensive income (loss) by component |  |
Beginning balance | (25,423) | (27,097)
OCI (loss) before reclassifications | (6,919) | (4,359)
Amounts reclassified from accumulated other comprehensive loss | 5,359 | 6,033
Ending balance | $ (26,983) | $ (25,423)

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- Definition Amount after tax, before reclassification adjustments of other comprehensive income (loss). + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 220 -SubTopic 10 -Section 55 -Paragraph 15 -URI http://asc.fasb.org/extlink&oid=84158357&loc=d3e1436-108581 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 220 -SubTopic 10 -Section 45 -Paragraph 14A -URI http://asc.fasb.org/extlink&oid=84228862&loc=SL7669686-108580 + Details
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