XML 55 R30.htm IDEA: XBRL DOCUMENT
v2.4.0.8

Asset Retirement Obligations (Tables) | 3 Months Ended
--- | ---
Mar. 31, 2014
Schedule of Asset Retirement Obligations [Line Items] |
Reconciliation Of Changes In Asset Retirement Obligations | A reconciliation of the changes in AROs associated with long-lived assets is as follows (in millions):
| Alliant Energy |  | IPL |  | WPL
| 2014 |  | 2013 |  | 2014 |  | 2013 |  | 2014 |  | 2013
Balance, January 1 |  | $109.7 |  |  |  | $101.5 |  |  |  | $47.9 |  |  |  | $45.5 |  |  |  | $52.4 |  |  |  | $46.9 |
Liabilities settled | (0.5 | ) |  | (0.1 | ) |  | (0.3 | ) |  | — |  |  | (0.2 | ) |  | (0.1 | )
Liabilities incurred (a) | 16.5 |  |  | — |  |  | 16.3 |  |  | — |  |  | 0.2 |  |  | — |
Accretion expense | 1.0 |  |  | 1.0 |  |  | 0.5 |  |  | 0.5 |  |  | 0.4 |  |  | 0.4 |
Balance, March 31 |  | $126.7 |  |  |  | $102.4 |  |  |  | $64.4 |  |  |  | $46.0 |  |  |  | $52.8 |  |  |  | $47.2 |
(a) | In 2014, IPL recorded AROs of $12.0 million related to its Sutherland Generating Station.
IPL [Member] |
Schedule of Asset Retirement Obligations [Line Items] |
Reconciliation Of Changes In Asset Retirement Obligations | A reconciliation of the changes in AROs associated with long-lived assets is as follows (in millions):
| Alliant Energy |  | IPL |  | WPL
| 2014 |  | 2013 |  | 2014 |  | 2013 |  | 2014 |  | 2013
Balance, January 1 |  | $109.7 |  |  |  | $101.5 |  |  |  | $47.9 |  |  |  | $45.5 |  |  |  | $52.4 |  |  |  | $46.9 |
Liabilities settled | (0.5 | ) |  | (0.1 | ) |  | (0.3 | ) |  | — |  |  | (0.2 | ) |  | (0.1 | )
Liabilities incurred (a) | 16.5 |  |  | — |  |  | 16.3 |  |  | — |  |  | 0.2 |  |  | — |
Accretion expense | 1.0 |  |  | 1.0 |  |  | 0.5 |  |  | 0.5 |  |  | 0.4 |  |  | 0.4 |
Balance, March 31 |  | $126.7 |  |  |  | $102.4 |  |  |  | $64.4 |  |  |  | $46.0 |  |  |  | $52.8 |  |  |  | $47.2 |
(a) | In 2014, IPL recorded AROs of $12.0 million related to its Sutherland Generating Station.
WPL [Member] |
Schedule of Asset Retirement Obligations [Line Items] |
Reconciliation Of Changes In Asset Retirement Obligations | A reconciliation of the changes in AROs associated with long-lived assets is as follows (in millions):
| Alliant Energy |  | IPL |  | WPL
| 2014 |  | 2013 |  | 2014 |  | 2013 |  | 2014 |  | 2013
Balance, January 1 |  | $109.7 |  |  |  | $101.5 |  |  |  | $47.9 |  |  |  | $45.5 |  |  |  | $52.4 |  |  |  | $46.9 |
Liabilities settled | (0.5 | ) |  | (0.1 | ) |  | (0.3 | ) |  | — |  |  | (0.2 | ) |  | (0.1 | )
Liabilities incurred (a) | 16.5 |  |  | — |  |  | 16.3 |  |  | — |  |  | 0.2 |  |  | — |
Accretion expense | 1.0 |  |  | 1.0 |  |  | 0.5 |  |  | 0.5 |  |  | 0.4 |  |  | 0.4 |
Balance, March 31 |  | $126.7 |  |  |  | $102.4 |  |  |  | $64.4 |  |  |  | $46.0 |  |  |  | $52.8 |  |  |  | $47.2 |
(a) | In 2014, IPL recorded AROs of $12.0 million related to its Sutherland Generating Station.

X
- Details
Name: | lnt_ScheduleOfAssetRetirementObligationsLineItems
Namespace Prefix: | lnt_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration

X
- 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
Name: | us-gaap_ScheduleOfChangeInAssetRetirementObligationTableTextBlock
Namespace Prefix: | us-gaap_
Data Type: | nonnum:textBlockItemType
Balance Type: | na
Period Type: | duration