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SCHEDULE II - RESERVE FOR UNCOLLECTIBLES (Details) - Reserve for uncollectibles. - USD ($) $ in Thousands | 12 Months Ended
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Dec. 31, 2019 | Dec. 31, 2018 | Dec. 31, 2017
ARIZONA PUBLIC SERVICE COMPANY |  |  |
Changes in reserve for uncollectibles |  |  |
Balance at beginning of period | $ 4,069 | $ 2,513 | $ 3,037
Additions, Charged to cost and expenses | 11,819 | 10,870 | 6,836
Additions, Charged to other accounts | 0 | 0 | 0
Deductions | 7,717 | 9,314 | 7,360
Balance at end of period | 8,171 | 4,069 | 2,513
Pinnacle West |  |  |
Changes in reserve for uncollectibles |  |  |
Balance at beginning of period | 4,069 | 2,513 | 3,037
Additions, Charged to cost and expenses | 11,819 | 10,870 | 6,836
Additions, Charged to other accounts | 0 | 0 | 0
Deductions | 7,717 | 9,314 | 7,360
Balance at end of period | $ 8,171 | $ 4,069 | $ 2,513

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- Definition Amount of valuation and qualifying accounts and reserves. + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 235 -SubTopic 10 -Section S99 -Paragraph 4 -Subparagraph (SX 210.12-09) -URI http://asc.fasb.org/extlink&oid=26873400&loc=d3e24092-122690 + Details
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