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Valuation and Qualifying Accounts And Reserves | 12 Months Ended
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Dec. 31, 2019
SEC Schedule, 12-09, Valuation and Qualifying Accounts Disclosure [Line Items] |
Valuation and Qualifying Accounts And Reserves | SCHEDULE II - VALUATION AND QUALIFYING ACCOUNTS AND RESERVES
|  |  |  | Additions |  |
| Balance, | Charged to | Charged to Other |  | Balance,
Description | January 1 | Expense | Accounts (a) | Deductions (b) | December 31
| (in millions)
Valuation and Qualifying Accounts Which are Deducted in the Balance Sheet from the Assets to Which They Apply:
| Accumulated Provision for Uncollectible Accounts: |  |  |  |
|  | Alliant Energy (c) |  |  |  |  |
|  |  | Year ended December 31, 2019 |  | $10.5 |  |  | $17.3 |  |  | $2.4 |  |  | $22.9 |  |  | $7.3 |
|  |  | Year ended December 31, 2018 | 12.0 |  | 21.2 |  | 1.0 |  | 23.7 |  | 10.5 |
|  |  | Year ended December 31, 2017 | 8.7 |  | 15.1 |  | 5.4 |  | 17.2 |  | 12.0 |
|  | IPL (c) |  |  |  |
|  |  | Year ended December 31, 2019 |  | $3.1 |  |  | $16.5 |  |  | $— |  |  | $18.4 |  |  | $1.2 |
|  |  | Year ended December 31, 2018 | 1.3 |  | 20.9 |  | — |  | 19.1 |  | 3.1 |
|  |  | Year ended December 31, 2017 | 1.1 |  | 14.9 |  | — |  | 14.7 |  | 1.3 |
|  | WPL |  |  |  |
|  |  | Year ended December 31, 2019 |  | $7.4 |  |  | $0.8 |  |  | $2.4 |  |  | $4.5 |  |  | $6.1 |
|  |  | Year ended December 31, 2018 | 10.7 |  | 0.3 |  | 1.0 |  | 4.6 |  | 7.4 |
|  |  | Year ended December 31, 2017 | 7.1 |  | 0.2 |  | 5.4 |  | 2.0 |  | 10.7 |
Note: The above provisions relate to various customer, notes and other receivable balances included in various line items on the respective balance sheets.
(a) | Accumulated provision for uncollectible accounts: In accordance with its regulatory treatment, certain amounts provided by WPL are recorded in regulatory assets. WPL expenses these amounts when an uncollectible account is written-off.
Accumulated provision for other reserves: In 2017, Alliant Energy recorded amounts to deferred tax liabilities related to the impacts of Federal Tax Reform.
(b) | Deductions are of the nature for which the reserves were created. In the case of the accumulated provision for uncollectible accounts, deductions from this reserve are reduced by recoveries of amounts previously written off.
(c) | Refer to Note 5(b) for discussion of IPL’s sales of accounts receivable program.
IPL [Member] |
SEC Schedule, 12-09, Valuation and Qualifying Accounts Disclosure [Line Items] |
Valuation and Qualifying Accounts And Reserves | SCHEDULE II - VALUATION AND QUALIFYING ACCOUNTS AND RESERVES
|  |  |  | Additions |  |
| Balance, | Charged to | Charged to Other |  | Balance,
Description | January 1 | Expense | Accounts (a) | Deductions (b) | December 31
| (in millions)
Valuation and Qualifying Accounts Which are Deducted in the Balance Sheet from the Assets to Which They Apply:
| Accumulated Provision for Uncollectible Accounts: |  |  |  |
|  | Alliant Energy (c) |  |  |  |  |
|  |  | Year ended December 31, 2019 |  | $10.5 |  |  | $17.3 |  |  | $2.4 |  |  | $22.9 |  |  | $7.3 |
|  |  | Year ended December 31, 2018 | 12.0 |  | 21.2 |  | 1.0 |  | 23.7 |  | 10.5 |
|  |  | Year ended December 31, 2017 | 8.7 |  | 15.1 |  | 5.4 |  | 17.2 |  | 12.0 |
|  | IPL (c) |  |  |  |
|  |  | Year ended December 31, 2019 |  | $3.1 |  |  | $16.5 |  |  | $— |  |  | $18.4 |  |  | $1.2 |
|  |  | Year ended December 31, 2018 | 1.3 |  | 20.9 |  | — |  | 19.1 |  | 3.1 |
|  |  | Year ended December 31, 2017 | 1.1 |  | 14.9 |  | — |  | 14.7 |  | 1.3 |
|  | WPL |  |  |  |
|  |  | Year ended December 31, 2019 |  | $7.4 |  |  | $0.8 |  |  | $2.4 |  |  | $4.5 |  |  | $6.1 |
|  |  | Year ended December 31, 2018 | 10.7 |  | 0.3 |  | 1.0 |  | 4.6 |  | 7.4 |
|  |  | Year ended December 31, 2017 | 7.1 |  | 0.2 |  | 5.4 |  | 2.0 |  | 10.7 |
Note: The above provisions relate to various customer, notes and other receivable balances included in various line items on the respective balance sheets.
(a) | Accumulated provision for uncollectible accounts: In accordance with its regulatory treatment, certain amounts provided by WPL are recorded in regulatory assets. WPL expenses these amounts when an uncollectible account is written-off.
Accumulated provision for other reserves: In 2017, Alliant Energy recorded amounts to deferred tax liabilities related to the impacts of Federal Tax Reform.
(b) | Deductions are of the nature for which the reserves were created. In the case of the accumulated provision for uncollectible accounts, deductions from this reserve are reduced by recoveries of amounts previously written off.
(c) | Refer to Note 5(b) for discussion of IPL’s sales of accounts receivable program.
WPL [Member] |
SEC Schedule, 12-09, Valuation and Qualifying Accounts Disclosure [Line Items] |
Valuation and Qualifying Accounts And Reserves | SCHEDULE II - VALUATION AND QUALIFYING ACCOUNTS AND RESERVES
|  |  |  | Additions |  |
| Balance, | Charged to | Charged to Other |  | Balance,
Description | January 1 | Expense | Accounts (a) | Deductions (b) | December 31
| (in millions)
Valuation and Qualifying Accounts Which are Deducted in the Balance Sheet from the Assets to Which They Apply:
| Accumulated Provision for Uncollectible Accounts: |  |  |  |
|  | Alliant Energy (c) |  |  |  |  |
|  |  | Year ended December 31, 2019 |  | $10.5 |  |  | $17.3 |  |  | $2.4 |  |  | $22.9 |  |  | $7.3 |
|  |  | Year ended December 31, 2018 | 12.0 |  | 21.2 |  | 1.0 |  | 23.7 |  | 10.5 |
|  |  | Year ended December 31, 2017 | 8.7 |  | 15.1 |  | 5.4 |  | 17.2 |  | 12.0 |
|  | IPL (c) |  |  |  |
|  |  | Year ended December 31, 2019 |  | $3.1 |  |  | $16.5 |  |  | $— |  |  | $18.4 |  |  | $1.2 |
|  |  | Year ended December 31, 2018 | 1.3 |  | 20.9 |  | — |  | 19.1 |  | 3.1 |
|  |  | Year ended December 31, 2017 | 1.1 |  | 14.9 |  | — |  | 14.7 |  | 1.3 |
|  | WPL |  |  |  |
|  |  | Year ended December 31, 2019 |  | $7.4 |  |  | $0.8 |  |  | $2.4 |  |  | $4.5 |  |  | $6.1 |
|  |  | Year ended December 31, 2018 | 10.7 |  | 0.3 |  | 1.0 |  | 4.6 |  | 7.4 |
|  |  | Year ended December 31, 2017 | 7.1 |  | 0.2 |  | 5.4 |  | 2.0 |  | 10.7 |
Note: The above provisions relate to various customer, notes and other receivable balances included in various line items on the respective balance sheets.
(a) | Accumulated provision for uncollectible accounts: In accordance with its regulatory treatment, certain amounts provided by WPL are recorded in regulatory assets. WPL expenses these amounts when an uncollectible account is written-off.
Accumulated provision for other reserves: In 2017, Alliant Energy recorded amounts to deferred tax liabilities related to the impacts of Federal Tax Reform.
(b) | Deductions are of the nature for which the reserves were created. In the case of the accumulated provision for uncollectible accounts, deductions from this reserve are reduced by recoveries of amounts previously written off.
(c) | Refer to Note 5(b) for discussion of IPL’s sales of accounts receivable program.

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- Definition The entire disclosure for valuation and qualifying accounts and reserves. + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Publisher SEC -Name Regulation S-X (SX) -Number 210 -Section 12 -Subsection 09 Reference 2: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 235 -SubTopic 10 -Section S99 -Paragraph 4 -Subparagraph (SX 210.12-09) -URI http://asc.fasb.org/extlink&oid=26873400&loc=d3e24092-122690 + Details
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