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Receivables (Details of Accounts Receivable) (Details) - USD ($) $ in Millions | Dec. 31, 2020 | Dec. 31, 2019
--- | --- | ---
Accounts Receivable [Line Items] |  |
Customer | $ 101 | $ 92
Unbilled utility revenues | 82 | 82
Deferred proceeds | 188 | 188
Other | 59 | 47
Allowance for expected credit losses | (18) | (7)
Accounts receivable, less allowance for expected credit losses | 412 | 402
IPL [Member] |  |
Accounts Receivable [Line Items] |  |
Customer | 0 | 0
Unbilled utility revenues | 0 | 0
Deferred proceeds | 188 | 188
Other | 23 | 16
Allowance for expected credit losses | (1) | (1)
Accounts receivable, less allowance for expected credit losses | 210 | 203
WPL [Member] |  |
Accounts Receivable [Line Items] |  |
Customer | 92 | 84
Unbilled utility revenues | 82 | 82
Other | 35 | 31
Allowance for expected credit losses | (17) | (6)
Accounts receivable, less allowance for expected credit losses | $ 192 | $ 191

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