XML 88 R15.htm IDEA: XBRL DOCUMENT
v3.2.0.727

Asset Retirement Obligations | 6 Months Ended
--- | ---
Jun. 30, 2015
Asset Retirement Obligations [Line Items] |
Asset Retirement Obligations | ASSET RETIREMENT OBLIGATIONS A reconciliation of the changes in AROs associated with long-lived assets is as follows (in millions):
| Alliant Energy |  | IPL |  | WPL
| 2015 |  | 2014 |  | 2015 |  | 2014 |  | 2015 |  | 2014
Balance, January 1 |  | $114.0 |  |  |  | $109.7 |  |  |  | $51.8 |  |  |  | $47.9 |  |  |  | $52.4 |  |  |  | $52.4 |
Revisions in estimated cash flows (a) | 2.1 |  |  | — |  |  | 0.9 |  |  | — |  |  | 1.2 |  |  | — |
Liabilities settled | (6.4 | ) |  | (0.7 | ) |  | (2.4 | ) |  | (0.4 | ) |  | (4.0 | ) |  | (0.3 | )
Liabilities incurred (a) | 72.3 |  |  | 16.5 |  |  | 56.1 |  |  | 16.3 |  |  | 16.2 |  |  | 0.2 |
Accretion expense | 2.2 |  |  | 2.1 |  |  | 0.9 |  |  | 1.0 |  |  | 0.9 |  |  | 0.8 |
Balance, June 30 |  | $184.2 |  |  |  | $127.6 |  |  |  | $107.3 |  |  |  | $64.8 |  |  |  | $66.7 |  |  |  | $53.1 |
(a) | In April 2015, the EPA published the final CCR Rule, which regulates CCR as a non-hazardous waste and is 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 the second quarter of 2015, Alliant Energy, IPL and WPL recognized additional AROs of $74 million, $57 million and $17 million, respectively, as a result of the final CCR Rule. The 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 the second quarter of 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] |
Asset Retirement Obligations [Line Items] |
Asset Retirement Obligations | ASSET RETIREMENT OBLIGATIONS A reconciliation of the changes in AROs associated with long-lived assets is as follows (in millions):
| Alliant Energy |  | IPL |  | WPL
| 2015 |  | 2014 |  | 2015 |  | 2014 |  | 2015 |  | 2014
Balance, January 1 |  | $114.0 |  |  |  | $109.7 |  |  |  | $51.8 |  |  |  | $47.9 |  |  |  | $52.4 |  |  |  | $52.4 |
Revisions in estimated cash flows (a) | 2.1 |  |  | — |  |  | 0.9 |  |  | — |  |  | 1.2 |  |  | — |
Liabilities settled | (6.4 | ) |  | (0.7 | ) |  | (2.4 | ) |  | (0.4 | ) |  | (4.0 | ) |  | (0.3 | )
Liabilities incurred (a) | 72.3 |  |  | 16.5 |  |  | 56.1 |  |  | 16.3 |  |  | 16.2 |  |  | 0.2 |
Accretion expense | 2.2 |  |  | 2.1 |  |  | 0.9 |  |  | 1.0 |  |  | 0.9 |  |  | 0.8 |
Balance, June 30 |  | $184.2 |  |  |  | $127.6 |  |  |  | $107.3 |  |  |  | $64.8 |  |  |  | $66.7 |  |  |  | $53.1 |
(a) | In April 2015, the EPA published the final CCR Rule, which regulates CCR as a non-hazardous waste and is 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 the second quarter of 2015, Alliant Energy, IPL and WPL recognized additional AROs of $74 million, $57 million and $17 million, respectively, as a result of the final CCR Rule. The 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 the second quarter of 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] |
Asset Retirement Obligations [Line Items] |
Asset Retirement Obligations | ASSET RETIREMENT OBLIGATIONS A reconciliation of the changes in AROs associated with long-lived assets is as follows (in millions):
| Alliant Energy |  | IPL |  | WPL
| 2015 |  | 2014 |  | 2015 |  | 2014 |  | 2015 |  | 2014
Balance, January 1 |  | $114.0 |  |  |  | $109.7 |  |  |  | $51.8 |  |  |  | $47.9 |  |  |  | $52.4 |  |  |  | $52.4 |
Revisions in estimated cash flows (a) | 2.1 |  |  | — |  |  | 0.9 |  |  | — |  |  | 1.2 |  |  | — |
Liabilities settled | (6.4 | ) |  | (0.7 | ) |  | (2.4 | ) |  | (0.4 | ) |  | (4.0 | ) |  | (0.3 | )
Liabilities incurred (a) | 72.3 |  |  | 16.5 |  |  | 56.1 |  |  | 16.3 |  |  | 16.2 |  |  | 0.2 |
Accretion expense | 2.2 |  |  | 2.1 |  |  | 0.9 |  |  | 1.0 |  |  | 0.9 |  |  | 0.8 |
Balance, June 30 |  | $184.2 |  |  |  | $127.6 |  |  |  | $107.3 |  |  |  | $64.8 |  |  |  | $66.7 |  |  |  | $53.1 |
(a) | In April 2015, the EPA published the final CCR Rule, which regulates CCR as a non-hazardous waste and is 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 the second quarter of 2015, Alliant Energy, IPL and WPL recognized additional AROs of $74 million, $57 million and $17 million, respectively, as a result of the final CCR Rule. The 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 the second quarter of 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.

X
- Definition Asset Retirement Obligations [Line Items] + References No definition available. + Details
Name: | lnt_AssetRetirementObligationsLineItems
Namespace Prefix: | lnt_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration

X
- Definition The entire disclosure for an asset retirement obligation and the associated long-lived asset. An asset retirement obligation is a legal obligation associated with the disposal or retirement from service of a tangible long-lived asset that results from the acquisition, construction or development, or the normal operations of a long-lived asset, except for certain obligations of lessees. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 410 -SubTopic 20 -Section 50 -Paragraph 1 -URI http://asc.fasb.org/extlink&oid=6392692&loc=d3e7535-110849 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 410 -SubTopic 20 -Section 50 -Paragraph 2 -URI http://asc.fasb.org/extlink&oid=6392692&loc=d3e7569-110849 + Details
Name: | us-gaap_AssetRetirementObligationDisclosureTextBlock
Namespace Prefix: | us-gaap_
Data Type: | nonnum:textBlockItemType
Balance Type: | na
Period Type: | duration

X
- Details
Name: | dei_LegalEntityAxis=lnt_IplMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | dei_LegalEntityAxis=lnt_WplMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |