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Receivables (Tables) | 12 Months Ended
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Dec. 31, 2017
Accounts, Notes, Loans and Financing 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
| 2017 |  | 2016 |  | 2017 |  | 2016 |  | 2017 |  | 2016
Customer |  | $103.3 |  |  |  | $111.7 |  |  |  | $— |  |  |  | $— |  |  |  | $97.7 |  |  |  | $104.4 |
Unbilled utility revenues | 85.1 |  |  | 90.2 |  |  | — |  |  | — |  |  | 85.1 |  |  | 90.2 |
Deferred proceeds | 222.1 |  |  | 211.1 |  |  | 222.1 |  |  | 211.1 |  |  | — |  |  | — |
Other | 84.3 |  |  | 89.0 |  |  | 44.1 |  |  | 30.7 |  |  | 40.1 |  |  | 38.8 |
Allowance for doubtful accounts | (12.0 | ) |  | (8.7 | ) |  | (1.3 | ) |  | (1.1 | ) |  | (10.7 | ) |  | (7.1 | )
|  | $482.8 |  |  |  | $493.3 |  |  |  | $264.9 |  |  |  | $240.7 |  |  |  | $212.2 |  |  |  | $226.3 |
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
| 2017 |  | 2016 |  | 2015 |  | 2017 |  | 2016 |  | 2015
Outstanding aggregate cash proceeds | $112.0 |  | $172.0 |  | $137.0 |  | $62.2 |  | $73.2 |  | $46.7
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):
| 2017 |  | 2016
Customer accounts receivable | $133.8 |  | $157.6
Unbilled utility revenues | 112.7 |  | 90.4
Other receivables | 0.3 |  | 0.1
Receivables sold to third party | 246.8 |  | 248.1
Less: cash proceeds (a) | 12.0 |  | 21.0
Deferred proceeds | 234.8 |  | 227.1
Less: allowance for doubtful accounts | 12.7 |  | 16.0
Fair value of deferred proceeds | $222.1 |  | $211.1
Outstanding receivables past due | $44.7 |  | $68.0
(a) | Changes in cash proceeds are presented in “Sales of accounts receivable” in operating activities in Alliant Energy’s and IPL’s cash flows statements.
Additional Attributes Of Receivables Sold Under The Agreement | Additional attributes of IPL’s receivables sold under the Receivables Agreement were as follows (in millions):
| 2017 |  | 2016 |  | 2015
Collections reinvested in receivables | $1,647.1 |  | $1,818.1 |  | $1,812.9
Write-offs, net of recoveries | 17.7 |  | 4.8 |  | 8.8
IPL [Member] |
Accounts, Notes, Loans and Financing 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
| 2017 |  | 2016 |  | 2017 |  | 2016 |  | 2017 |  | 2016
Customer |  | $103.3 |  |  |  | $111.7 |  |  |  | $— |  |  |  | $— |  |  |  | $97.7 |  |  |  | $104.4 |
Unbilled utility revenues | 85.1 |  |  | 90.2 |  |  | — |  |  | — |  |  | 85.1 |  |  | 90.2 |
Deferred proceeds | 222.1 |  |  | 211.1 |  |  | 222.1 |  |  | 211.1 |  |  | — |  |  | — |
Other | 84.3 |  |  | 89.0 |  |  | 44.1 |  |  | 30.7 |  |  | 40.1 |  |  | 38.8 |
Allowance for doubtful accounts | (12.0 | ) |  | (8.7 | ) |  | (1.3 | ) |  | (1.1 | ) |  | (10.7 | ) |  | (7.1 | )
|  | $482.8 |  |  |  | $493.3 |  |  |  | $264.9 |  |  |  | $240.7 |  |  |  | $212.2 |  |  |  | $226.3 |
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
| 2017 |  | 2016 |  | 2015 |  | 2017 |  | 2016 |  | 2015
Outstanding aggregate cash proceeds | $112.0 |  | $172.0 |  | $137.0 |  | $62.2 |  | $73.2 |  | $46.7
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):
| 2017 |  | 2016
Customer accounts receivable | $133.8 |  | $157.6
Unbilled utility revenues | 112.7 |  | 90.4
Other receivables | 0.3 |  | 0.1
Receivables sold to third party | 246.8 |  | 248.1
Less: cash proceeds (a) | 12.0 |  | 21.0
Deferred proceeds | 234.8 |  | 227.1
Less: allowance for doubtful accounts | 12.7 |  | 16.0
Fair value of deferred proceeds | $222.1 |  | $211.1
Outstanding receivables past due | $44.7 |  | $68.0
(a) | Changes in cash proceeds are presented in “Sales of accounts receivable” in operating activities in Alliant Energy’s and IPL’s cash flows statements.
Additional Attributes Of Receivables Sold Under The Agreement | Additional attributes of IPL’s receivables sold under the Receivables Agreement were as follows (in millions):
| 2017 |  | 2016 |  | 2015
Collections reinvested in receivables | $1,647.1 |  | $1,818.1 |  | $1,812.9
Write-offs, net of recoveries | 17.7 |  | 4.8 |  | 8.8
WPL [Member] |
Accounts, Notes, Loans and Financing 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
| 2017 |  | 2016 |  | 2017 |  | 2016 |  | 2017 |  | 2016
Customer |  | $103.3 |  |  |  | $111.7 |  |  |  | $— |  |  |  | $— |  |  |  | $97.7 |  |  |  | $104.4 |
Unbilled utility revenues | 85.1 |  |  | 90.2 |  |  | — |  |  | — |  |  | 85.1 |  |  | 90.2 |
Deferred proceeds | 222.1 |  |  | 211.1 |  |  | 222.1 |  |  | 211.1 |  |  | — |  |  | — |
Other | 84.3 |  |  | 89.0 |  |  | 44.1 |  |  | 30.7 |  |  | 40.1 |  |  | 38.8 |
Allowance for doubtful accounts | (12.0 | ) |  | (8.7 | ) |  | (1.3 | ) |  | (1.1 | ) |  | (10.7 | ) |  | (7.1 | )
|  | $482.8 |  |  |  | $493.3 |  |  |  | $264.9 |  |  |  | $240.7 |  |  |  | $212.2 |  |  |  | $226.3 |

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- Definition Tabular disclosure of the various types of trade accounts and notes receivable and for each the gross carrying value, allowance, and net carrying value as of the balance sheet date. Presentation is categorized by current, noncurrent and unclassified receivables. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 210 -SubTopic 10 -Section S99 -Paragraph 1 -Subparagraph (SX 210.5-02.3,4) -URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682 + Details
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