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Changes in Accumulated Other Comprehensive Loss | 9 Months Ended
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Sep. 30, 2017
Accumulated Other Comprehensive Income (Loss) [Line Items] |
Changes in Accumulated Other Comprehensive Loss | Changes in Accumulated Other Comprehensive Loss The following table shows the changes in Pinnacle West's consolidated accumulated other comprehensive loss, including reclassification adjustments, net of tax, by component for the three and nine months ended September 30, 2017 and 2016 (dollars in thousands):
| Three Months Ended |  | Nine Months Ended
| September 30, |  | September 30,
| 2017 |  | 2016 |  | 2017 |  | 2016
Balance at beginning of period | $ | (43,626 | ) |  | $ | (43,719 | ) |  | $ | (43,822 | ) |  | $ | (44,748 | )
Derivative Instruments |  |  |  |  |  |  |
OCI (loss) before reclassifications | 9 |  |  | (29 | ) |  | (754 | ) |  | (595 | )
Amounts reclassified from accumulated other comprehensive loss (a) | 710 |  |  | 798 |  |  | 2,480 |  |  | 2,564 |
Net current period OCI (loss) | 719 |  |  | 769 |  |  | 1,726 |  |  | 1,969 |
Pension and Other Postretirement Benefits |  |  |  |  |  |  |
OCI (loss) before reclassifications | — |  |  | — |  |  | (2,157 | ) |  | (1,585 | )
Amounts reclassified from accumulated other comprehensive loss (b) | 790 |  |  | 804 |  |  | 2,136 |  |  | 2,218 |
Net current period OCI (loss) | 790 |  |  | 804 |  |  | (21 | ) |  | 633 |
Balance at end of period | $ | (42,117 | ) |  | $ | (42,146 | ) |  | $ | (42,117 | ) |  | $ | (42,146 | )
(a) | These amounts represent realized gains and losses and are included in the computation of fuel and purchased power costs and are subject to the PSA. See Note 6.
(b) | These amounts primarily represent amortization of actuarial loss, and are included in the computation of net periodic pension cost. See Note 4.
Arizona Public Service Company |
Accumulated Other Comprehensive Income (Loss) [Line Items] |
Changes in Accumulated Other Comprehensive Loss | The following table shows the changes in APS's consolidated accumulated other comprehensive loss, including reclassification adjustments, net of tax, by component for the three and nine months ended September 30, 2017 and 2016 (dollars in thousands):
| Three Months Ended |  | Nine Months Ended
| September 30, |  | September 30,
| 2017 |  | 2016 |  | 2017 |  | 2016
Balance at beginning of period | $ | (25,112 | ) |  | $ | (25,928 | ) |  | $ | (25,423 | ) |  | $ | (27,097 | )
Derivative Instruments |  |  |  |  |  |  |
OCI (loss) before reclassifications | 9 |  |  | (29 | ) |  | (754 | ) |  | (595 | )
Amounts reclassified from accumulated other comprehensive loss (a) | 710 |  |  | 798 |  |  | 2,480 |  |  | 2,564 |
Net current period OCI (loss) | 719 |  |  | 769 |  |  | 1,726 |  |  | 1,969 |
Pension and Other Postretirement Benefits |  |  |  |  |  |  |
OCI (loss) before reclassifications | — |  |  | — |  |  | (2,121 | ) |  | (1,521 | )
Amounts reclassified from accumulated other comprehensive loss (b) | 777 |  |  | 799 |  |  | 2,202 |  |  | 2,289 |
Net current period OCI (loss) | 777 |  |  | 799 |  |  | 81 |  |  | 768 |
Balance at end of period | $ | (23,616 | ) |  | $ | (24,360 | ) |  | $ | (23,616 | ) |  | $ | (24,360 | )
(a) | These amounts represent realized gains and losses and are included in the computation of fuel and purchased power costs and are subject to the PSA. See Note 6.
(b) | These amounts primarily represent amortization of actuarial loss and are included in the computation of net periodic pension cost. See Note 4.

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- Definition Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table. + References No definition available. + Details
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- Definition The entire disclosure for comprehensive income, which includes, but is not limited to, 1) the amount of income tax expense or benefit allocated to each component of other comprehensive income, including reclassification adjustments, 2) the reclassification adjustments for each classification of other comprehensive income and 3) the ending accumulated balances for each component of comprehensive income. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 220 -URI http://asc.fasb.org/topic&trid=2134417 + Details
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