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Receivables (Tables) | 12 Months Ended
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Dec. 31, 2020
Accounts Receivable [Line Items] |
Accounts Receivable Details | Details for accounts receivable included on the balance sheets as of December 31 were as follows (in millions):
| Alliant Energy |  | IPL |  | WPL
| 2020 |  | 2019 |  | 2020 |  | 2019 |  | 2020 |  | 2019
Customer | $101 |  |  | $92 |  |  | $— |  |  | $— |  |  | $92 |  |  | $84 |
Unbilled utility revenues | 82 |  |  | 82 |  |  | — |  |  | — |  |  | 82 |  |  | 82 |
Deferred proceeds | 188 |  |  | 188 |  |  | 188 |  |  | 188 |  |  | — |  |  | — |
Other | 59 |  |  | 47 |  |  | 23 |  |  | 16 |  |  | 35 |  |  | 31 |
Allowance for expected credit losses | (18) |  |  | (7) |  |  | (1) |  |  | (1) |  |  | (17) |  |  | (6) |
| $412 |  |  | $402 |  |  | $210 |  |  | $203 |  |  | $192 |  |  | $191 |
Maximum And Average Outstanding Cash Proceeds | IPL’s maximum and average outstanding aggregate cash proceeds (based on daily outstanding balances) related to the sales of accounts receivable program were as follows (in millions):
| Maximum |  | Average
| 2020 |  | 2019 |  | 2018 |  | 2020 |  | 2019 |  | 2018
Outstanding aggregate cash proceeds | $96 |  | $108 |  | $116 |  | $9 |  | $36 |  | $53
Receivables Sold Under the Agreement | As of December 31, the attributes of IPL’s receivables sold under the Receivables Agreement were as follows (in millions):
| 2020 |  | 2019
Customer accounts receivable | $114 |  | $125
Unbilled utility revenues | 92 |  | 95
Other receivables | — |  | 1
Receivables sold to third party | 206 |  | 221
Less: cash proceeds | 1 |  | 27
Deferred proceeds | 205 |  | 194
Less: allowance for expected credit losses | 17 |  | 6
Fair value of deferred proceeds | $188 |  | $188
Outstanding receivables past due | $27 |  | $26
Additional Attributes Of Receivables Sold Under The Agreement | Additional attributes of IPL’s receivables sold under the Receivables Agreement were as follows (in millions):
| 2020 |  | 2019 |  | 2018
Collections | $2,025 |  | $2,193 |  | $2,077
Write-offs, net of recoveries | 7 |  | 19 |  | 21
IPL [Member] |
Accounts Receivable [Line Items] |
Accounts Receivable Details | Details for accounts receivable included on the balance sheets as of December 31 were as follows (in millions):
| Alliant Energy |  | IPL |  | WPL
| 2020 |  | 2019 |  | 2020 |  | 2019 |  | 2020 |  | 2019
Customer | $101 |  |  | $92 |  |  | $— |  |  | $— |  |  | $92 |  |  | $84 |
Unbilled utility revenues | 82 |  |  | 82 |  |  | — |  |  | — |  |  | 82 |  |  | 82 |
Deferred proceeds | 188 |  |  | 188 |  |  | 188 |  |  | 188 |  |  | — |  |  | — |
Other | 59 |  |  | 47 |  |  | 23 |  |  | 16 |  |  | 35 |  |  | 31 |
Allowance for expected credit losses | (18) |  |  | (7) |  |  | (1) |  |  | (1) |  |  | (17) |  |  | (6) |
| $412 |  |  | $402 |  |  | $210 |  |  | $203 |  |  | $192 |  |  | $191 |
Maximum And Average Outstanding Cash Proceeds | IPL’s maximum and average outstanding aggregate cash proceeds (based on daily outstanding balances) related to the sales of accounts receivable program were as follows (in millions):
| Maximum |  | Average
| 2020 |  | 2019 |  | 2018 |  | 2020 |  | 2019 |  | 2018
Outstanding aggregate cash proceeds | $96 |  | $108 |  | $116 |  | $9 |  | $36 |  | $53
Receivables Sold Under the Agreement | As of December 31, the attributes of IPL’s receivables sold under the Receivables Agreement were as follows (in millions):
| 2020 |  | 2019
Customer accounts receivable | $114 |  | $125
Unbilled utility revenues | 92 |  | 95
Other receivables | — |  | 1
Receivables sold to third party | 206 |  | 221
Less: cash proceeds | 1 |  | 27
Deferred proceeds | 205 |  | 194
Less: allowance for expected credit losses | 17 |  | 6
Fair value of deferred proceeds | $188 |  | $188
Outstanding receivables past due | $27 |  | $26
Additional Attributes Of Receivables Sold Under The Agreement | Additional attributes of IPL’s receivables sold under the Receivables Agreement were as follows (in millions):
| 2020 |  | 2019 |  | 2018
Collections | $2,025 |  | $2,193 |  | $2,077
Write-offs, net of recoveries | 7 |  | 19 |  | 21
WPL [Member] |
Accounts Receivable [Line Items] |
Accounts Receivable Details | Details for accounts receivable included on the balance sheets as of December 31 were as follows (in millions):
| Alliant Energy |  | IPL |  | WPL
| 2020 |  | 2019 |  | 2020 |  | 2019 |  | 2020 |  | 2019
Customer | $101 |  |  | $92 |  |  | $— |  |  | $— |  |  | $92 |  |  | $84 |
Unbilled utility revenues | 82 |  |  | 82 |  |  | — |  |  | — |  |  | 82 |  |  | 82 |
Deferred proceeds | 188 |  |  | 188 |  |  | 188 |  |  | 188 |  |  | — |  |  | — |
Other | 59 |  |  | 47 |  |  | 23 |  |  | 16 |  |  | 35 |  |  | 31 |
Allowance for expected credit losses | (18) |  |  | (7) |  |  | (1) |  |  | (1) |  |  | (17) |  |  | (6) |
| $412 |  |  | $402 |  |  | $210 |  |  | $203 |  |  | $192 |  |  | $191 |

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