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Receivables (Details of Accounts Receivable) (Details) - USD ($) $ in Millions | Dec. 31, 2019 | Dec. 31, 2018
--- | --- | ---
Accounts Receivable [Line Items] |  |
Customer | $ 91.6 | $ 91.0
Unbilled utility revenues | 82.1 | 74.2
Deferred proceeds | 187.7 | 119.4
Other | 48.0 | 76.3
Allowance for doubtful accounts | (7.3) | (10.5)
Accounts receivable, less allowance for doubtful accounts | 402.1 | 350.4
IPL [Member] |  |
Accounts Receivable [Line Items] |  |
Customer | 0.0 | 0.0
Unbilled utility revenues | 0.0 | 0.0
Deferred proceeds | 187.7 | 119.4
Other | 16.3 | 37.2
Allowance for doubtful accounts | (1.2) | (3.1)
Accounts receivable, less allowance for doubtful accounts | 202.8 | 153.5
WPL [Member] |  |
Accounts Receivable [Line Items] |  |
Customer | 83.5 | 84.8
Unbilled utility revenues | 82.1 | 74.2
Other | 31.4 | 38.5
Allowance for doubtful accounts | (6.1) | (7.4)
Accounts receivable, less allowance for doubtful accounts | $ 190.9 | $ 190.1

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