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RECEIVABLES - Summary of Bad Debt Expense (Details) - SEC Schedule, 12-09, Allowance, Credit Loss - Customer Contracts - USD ($) $ in Millions | 3 Months Ended
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Mar. 31, 2019 | Mar. 31, 2018
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |
Impairment losses recognized on receivables | $ 4.0 | $ 4.0
Westar Energy |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |
Impairment losses recognized on receivables | (0.3) | 4.0
KCP&L |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |
Impairment losses recognized on receivables | $ 2.8 | $ 1.7

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- Definition Amount of increase in valuation and qualifying accounts and reserves from charge to cost and expense. + 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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