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Receivables (Details of Accounts Receivable) (Details) - USD ($) $ in Millions | Sep. 30, 2020 | Dec. 31, 2019
--- | --- | ---
Receivables [Line Items] |  |
Customer | $ 95 | $ 92
Unbilled utility revenues | 62 | 82
Deferred proceeds | 201 | 188
Other | 54 | 47
Allowance for expected credit losses | (13) | (7)
Accounts receivable, less allowance for expected credit losses | 399 | 402
IPL [Member] |  |
Receivables [Line Items] |  |
Customer | 0 | 0
Unbilled utility revenues | 0 | 0
Deferred proceeds | 201 | 188
Other | 20 | 16
Allowance for expected credit losses | (2) | (1)
Accounts receivable, less allowance for expected credit losses | 219 | 203
WPL [Member] |  |
Receivables [Line Items] |  |
Customer | 86 | 84
Unbilled utility revenues | 62 | 82
Other | 33 | 31
Allowance for expected credit losses | (11) | (6)
Accounts receivable, less allowance for expected credit losses | $ 170 | $ 191

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