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Asset Retirement Obligations (Tables) | 12 Months Ended
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Dec. 31, 2016
Schedule of Asset Retirement Obligations [Line Items] |
Reconciliation Of Changes In Asset Retirement Obligations (AROs) | A reconciliation of the changes in AROs associated with long-lived assets is as follows (in millions):
| Alliant Energy |  | IPL |  | WPL
| 2016 |  | 2015 |  | 2016 |  | 2015 |  | 2016 |  | 2015
Balance, January 1 |  | $214.0 |  |  |  | $114.0 |  |  |  | $132.9 |  |  |  | $51.8 |  |  |  | $71.9 |  |  |  | $52.4 |
Revisions in estimated cash flows (a) | (13.3 | ) |  | 17.3 |  |  | (5.8 | ) |  | 15.1 |  |  | (7.5 | ) |  | 3.2 |
Liabilities settled | (14.0 | ) |  | (8.8 | ) |  | (6.8 | ) |  | (4.3 | ) |  | (7.2 | ) |  | (4.5 | )
Liabilities incurred (a) | 2.6 |  |  | 86.6 |  |  | 0.7 |  |  | 67.8 |  |  | 1.9 |  |  | 18.8 |
Accretion expense | 6.4 |  |  | 4.9 |  |  | 3.7 |  |  | 2.5 |  |  | 2.3 |  |  | 2.0 |
Balance, December 31 |  | $195.7 |  |  |  | $214.0 |  |  |  | $124.7 |  |  |  | $132.9 |  |  |  | $61.4 |  |  |  | $71.9 |
(a) | In April 2015, the EPA published the final CCR Rule, which regulates CCR as a non-hazardous waste and was effective October 2015. IPL and WPL have nine and three coal-fired EGUs, respectively, with coal ash ponds that are impacted by this rule. In addition, IPL and WPL have four and two active CCR landfills, respectively, that are impacted by this rule. In 2015, Alliant Energy, IPL and WPL recognized additional AROs of $87 million, $67 million and $20 million, respectively, as a result of the final CCR Rule. These increases in AROs resulted in corresponding increases in property, plant and equipment, net on the respective balance sheets. Actual costs resulting from the CCR Rule may be different than the amounts recorded in 2015 due to potential changes in compliance strategies that will be used, as well as other potential cost estimate changes. Expenditures incurred by IPL and WPL to comply with the CCR Rule are anticipated to be recovered in rates from their customers.
IPL [Member] |
Schedule of Asset Retirement Obligations [Line Items] |
Reconciliation Of Changes In Asset Retirement Obligations (AROs) | A reconciliation of the changes in AROs associated with long-lived assets is as follows (in millions):
| Alliant Energy |  | IPL |  | WPL
| 2016 |  | 2015 |  | 2016 |  | 2015 |  | 2016 |  | 2015
Balance, January 1 |  | $214.0 |  |  |  | $114.0 |  |  |  | $132.9 |  |  |  | $51.8 |  |  |  | $71.9 |  |  |  | $52.4 |
Revisions in estimated cash flows (a) | (13.3 | ) |  | 17.3 |  |  | (5.8 | ) |  | 15.1 |  |  | (7.5 | ) |  | 3.2 |
Liabilities settled | (14.0 | ) |  | (8.8 | ) |  | (6.8 | ) |  | (4.3 | ) |  | (7.2 | ) |  | (4.5 | )
Liabilities incurred (a) | 2.6 |  |  | 86.6 |  |  | 0.7 |  |  | 67.8 |  |  | 1.9 |  |  | 18.8 |
Accretion expense | 6.4 |  |  | 4.9 |  |  | 3.7 |  |  | 2.5 |  |  | 2.3 |  |  | 2.0 |
Balance, December 31 |  | $195.7 |  |  |  | $214.0 |  |  |  | $124.7 |  |  |  | $132.9 |  |  |  | $61.4 |  |  |  | $71.9 |
(a) | In April 2015, the EPA published the final CCR Rule, which regulates CCR as a non-hazardous waste and was effective October 2015. IPL and WPL have nine and three coal-fired EGUs, respectively, with coal ash ponds that are impacted by this rule. In addition, IPL and WPL have four and two active CCR landfills, respectively, that are impacted by this rule. In 2015, Alliant Energy, IPL and WPL recognized additional AROs of $87 million, $67 million and $20 million, respectively, as a result of the final CCR Rule. These increases in AROs resulted in corresponding increases in property, plant and equipment, net on the respective balance sheets. Actual costs resulting from the CCR Rule may be different than the amounts recorded in 2015 due to potential changes in compliance strategies that will be used, as well as other potential cost estimate changes. Expenditures incurred by IPL and WPL to comply with the CCR Rule are anticipated to be recovered in rates from their customers.
WPL [Member] |
Schedule of Asset Retirement Obligations [Line Items] |
Reconciliation Of Changes In Asset Retirement Obligations (AROs) | A reconciliation of the changes in AROs associated with long-lived assets is as follows (in millions):
| Alliant Energy |  | IPL |  | WPL
| 2016 |  | 2015 |  | 2016 |  | 2015 |  | 2016 |  | 2015
Balance, January 1 |  | $214.0 |  |  |  | $114.0 |  |  |  | $132.9 |  |  |  | $51.8 |  |  |  | $71.9 |  |  |  | $52.4 |
Revisions in estimated cash flows (a) | (13.3 | ) |  | 17.3 |  |  | (5.8 | ) |  | 15.1 |  |  | (7.5 | ) |  | 3.2 |
Liabilities settled | (14.0 | ) |  | (8.8 | ) |  | (6.8 | ) |  | (4.3 | ) |  | (7.2 | ) |  | (4.5 | )
Liabilities incurred (a) | 2.6 |  |  | 86.6 |  |  | 0.7 |  |  | 67.8 |  |  | 1.9 |  |  | 18.8 |
Accretion expense | 6.4 |  |  | 4.9 |  |  | 3.7 |  |  | 2.5 |  |  | 2.3 |  |  | 2.0 |
Balance, December 31 |  | $195.7 |  |  |  | $214.0 |  |  |  | $124.7 |  |  |  | $132.9 |  |  |  | $61.4 |  |  |  | $71.9 |
(a) | In April 2015, the EPA published the final CCR Rule, which regulates CCR as a non-hazardous waste and was effective October 2015. IPL and WPL have nine and three coal-fired EGUs, respectively, with coal ash ponds that are impacted by this rule. In addition, IPL and WPL have four and two active CCR landfills, respectively, that are impacted by this rule. In 2015, Alliant Energy, IPL and WPL recognized additional AROs of $87 million, $67 million and $20 million, respectively, as a result of the final CCR Rule. These increases in AROs resulted in corresponding increases in property, plant and equipment, net on the respective balance sheets. Actual costs resulting from the CCR Rule may be different than the amounts recorded in 2015 due to potential changes in compliance strategies that will be used, as well as other potential cost estimate changes. Expenditures incurred by IPL and WPL to comply with the CCR Rule are anticipated to be recovered in rates from their customers.

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- Definition Tabular disclosure of the changes in carrying amount of a liability for asset retirement obligations, for changes such as new obligations, changes in estimates of existing obligations, spending on existing obligations, property dispositions, and foreign currency translation. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 410 -SubTopic 30 -Section 50 -Paragraph 5 -URI http://asc.fasb.org/extlink&oid=6393242&loc=d3e13201-110859 + Details
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