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Asset Retirement Obligations (Tables) | 12 Months Ended
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Dec. 31, 2014
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
| 2014 |  | 2013 |  | 2014 |  | 2013 |  | 2014 |  | 2013
Balance, January 1 |  | $109.7 |  |  |  | $101.5 |  |  |  | $47.9 |  |  |  | $45.5 |  |  |  | $52.4 |  |  |  | $46.9 |
Revisions in estimated cash flows | — |  |  | 5.6 |  |  | — |  |  | 0.1 |  |  | — |  |  | 5.5 |
Liabilities settled | (3.4 | ) |  | (2.3 | ) |  | (1.4 | ) |  | (0.6 | ) |  | (2.0 | ) |  | (1.7 | )
Liabilities incurred | 3.7 |  |  | 1.2 |  |  | 3.5 |  |  | 1.2 |  |  | 0.2 |  |  | — |
Accretion expense | 4.0 |  |  | 3.7 |  |  | 1.8 |  |  | 1.7 |  |  | 1.8 |  |  | 1.7 |
Balance, December 31 |  | $114.0 |  |  |  | $109.7 |  |  |  | $51.8 |  |  |  | $47.9 |  |  |  | $52.4 |  |  |  | $52.4 |
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
| 2014 |  | 2013 |  | 2014 |  | 2013 |  | 2014 |  | 2013
Balance, January 1 |  | $109.7 |  |  |  | $101.5 |  |  |  | $47.9 |  |  |  | $45.5 |  |  |  | $52.4 |  |  |  | $46.9 |
Revisions in estimated cash flows | — |  |  | 5.6 |  |  | — |  |  | 0.1 |  |  | — |  |  | 5.5 |
Liabilities settled | (3.4 | ) |  | (2.3 | ) |  | (1.4 | ) |  | (0.6 | ) |  | (2.0 | ) |  | (1.7 | )
Liabilities incurred | 3.7 |  |  | 1.2 |  |  | 3.5 |  |  | 1.2 |  |  | 0.2 |  |  | — |
Accretion expense | 4.0 |  |  | 3.7 |  |  | 1.8 |  |  | 1.7 |  |  | 1.8 |  |  | 1.7 |
Balance, December 31 |  | $114.0 |  |  |  | $109.7 |  |  |  | $51.8 |  |  |  | $47.9 |  |  |  | $52.4 |  |  |  | $52.4 |
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
| 2014 |  | 2013 |  | 2014 |  | 2013 |  | 2014 |  | 2013
Balance, January 1 |  | $109.7 |  |  |  | $101.5 |  |  |  | $47.9 |  |  |  | $45.5 |  |  |  | $52.4 |  |  |  | $46.9 |
Revisions in estimated cash flows | — |  |  | 5.6 |  |  | — |  |  | 0.1 |  |  | — |  |  | 5.5 |
Liabilities settled | (3.4 | ) |  | (2.3 | ) |  | (1.4 | ) |  | (0.6 | ) |  | (2.0 | ) |  | (1.7 | )
Liabilities incurred | 3.7 |  |  | 1.2 |  |  | 3.5 |  |  | 1.2 |  |  | 0.2 |  |  | — |
Accretion expense | 4.0 |  |  | 3.7 |  |  | 1.8 |  |  | 1.7 |  |  | 1.8 |  |  | 1.7 |
Balance, December 31 |  | $114.0 |  |  |  | $109.7 |  |  |  | $51.8 |  |  |  | $47.9 |  |  |  | $52.4 |  |  |  | $52.4 |

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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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