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Regulatory Matters (Tables) | 3 Months Ended
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Mar. 31, 2014
Regulatory Assets [Line Items] |
Regulatory Assets | Regulatory assets were comprised of the following items (in millions):
| Alliant Energy |  | IPL |  | WPL
| March 31, 2014 |  | December 31, 2013 |  | March 31, 2014 |  | December 31, 2013 |  | March 31, 2014 |  | December 31, 2013
Tax-related |  | $834.0 |  |  |  | $829.7 |  |  |  | $808.3 |  |  |  | $798.6 |  |  |  | $25.7 |  |  |  | $31.1 |
Pension and OPEB costs | 351.8 |  |  | 355.3 |  |  | 172.6 |  |  | 174.2 |  |  | 179.2 |  |  | 181.1 |
AROs | 68.5 |  |  | 65.7 |  |  | 38.6 |  |  | 36.7 |  |  | 29.9 |  |  | 29.0 |
Environmental-related costs | 27.8 |  |  | 25.0 |  |  | 23.0 |  |  | 21.0 |  |  | 4.8 |  |  | 4.0 |
Emission allowances | 29.2 |  |  | 30.0 |  |  | 29.2 |  |  | 30.0 |  |  | — |  |  | — |
Derivatives | 9.1 |  |  | 21.1 |  |  | 2.5 |  |  | 5.9 |  |  | 6.6 |  |  | 15.2 |
Other | 96.9 |  |  | 86.4 |  |  | 43.8 |  |  | 47.1 |  |  | 53.1 |  |  | 39.3 |
|  | $1,417.3 |  |  |  | $1,413.2 |  |  |  | $1,118.0 |  |  |  | $1,113.5 |  |  |  | $299.3 |  |  |  | $299.7 |
Regulatory Liabilities | Regulatory liabilities were comprised of the following items (in millions):
| Alliant Energy |  | IPL |  | WPL
| March 31, 2014 |  | December 31, 2013 |  | March 31, 2014 |  | December 31, 2013 |  | March 31, 2014 |  | December 31, 2013
Cost of removal obligations |  | $420.0 |  |  |  | $418.9 |  |  |  | $279.3 |  |  |  | $277.7 |  |  |  | $140.7 |  |  |  | $141.2 |
IPL’s tax benefit riders | 239.8 |  |  | 265.4 |  |  | 239.8 |  |  | 265.4 |  |  | — |  |  | — |
Energy efficiency cost recovery | 64.1 |  |  | 52.7 |  |  | 14.9 |  |  | 9.3 |  |  | 49.2 |  |  | 43.4 |
Derivatives | 33.3 |  |  | 7.2 |  |  | 8.8 |  |  | 3.6 |  |  | 24.5 |  |  | 3.6 |
IPL’s electric transmission cost recovery | 21.2 |  |  | 14.6 |  |  | 21.2 |  |  | 14.6 |  |  | — |  |  | — |
IPL’s electric transmission assets sale | 18.8 |  |  | 21.6 |  |  | 18.8 |  |  | 21.6 |  |  | — |  |  | — |
Other | 39.2 |  |  | 41.1 |  |  | 21.2 |  |  | 22.7 |  |  | 18.0 |  |  | 18.4 |
|  | $836.4 |  |  |  | $821.5 |  |  |  | $604.0 |  |  |  | $614.9 |  |  |  | $232.4 |  |  |  | $206.6 |
Tax Benefit Riders | For the three months ended March 31, 2014, Alliant Energy and IPL utilized “IPL’s tax benefit riders” regulatory liabilities to credit IPL’s Iowa retail electric and gas customers’ bills as follows (in millions):
Electric tax benefit rider |  | $23 |
Gas tax benefit rider | 3 |
|  | $26 |
IPL [Member] |
Regulatory Assets [Line Items] |
Regulatory Assets | Regulatory assets were comprised of the following items (in millions):
| Alliant Energy |  | IPL |  | WPL
| March 31, 2014 |  | December 31, 2013 |  | March 31, 2014 |  | December 31, 2013 |  | March 31, 2014 |  | December 31, 2013
Tax-related |  | $834.0 |  |  |  | $829.7 |  |  |  | $808.3 |  |  |  | $798.6 |  |  |  | $25.7 |  |  |  | $31.1 |
Pension and OPEB costs | 351.8 |  |  | 355.3 |  |  | 172.6 |  |  | 174.2 |  |  | 179.2 |  |  | 181.1 |
AROs | 68.5 |  |  | 65.7 |  |  | 38.6 |  |  | 36.7 |  |  | 29.9 |  |  | 29.0 |
Environmental-related costs | 27.8 |  |  | 25.0 |  |  | 23.0 |  |  | 21.0 |  |  | 4.8 |  |  | 4.0 |
Emission allowances | 29.2 |  |  | 30.0 |  |  | 29.2 |  |  | 30.0 |  |  | — |  |  | — |
Derivatives | 9.1 |  |  | 21.1 |  |  | 2.5 |  |  | 5.9 |  |  | 6.6 |  |  | 15.2 |
Other | 96.9 |  |  | 86.4 |  |  | 43.8 |  |  | 47.1 |  |  | 53.1 |  |  | 39.3 |
|  | $1,417.3 |  |  |  | $1,413.2 |  |  |  | $1,118.0 |  |  |  | $1,113.5 |  |  |  | $299.3 |  |  |  | $299.7 |
Regulatory Liabilities | Regulatory liabilities were comprised of the following items (in millions):
| Alliant Energy |  | IPL |  | WPL
| March 31, 2014 |  | December 31, 2013 |  | March 31, 2014 |  | December 31, 2013 |  | March 31, 2014 |  | December 31, 2013
Cost of removal obligations |  | $420.0 |  |  |  | $418.9 |  |  |  | $279.3 |  |  |  | $277.7 |  |  |  | $140.7 |  |  |  | $141.2 |
IPL’s tax benefit riders | 239.8 |  |  | 265.4 |  |  | 239.8 |  |  | 265.4 |  |  | — |  |  | — |
Energy efficiency cost recovery | 64.1 |  |  | 52.7 |  |  | 14.9 |  |  | 9.3 |  |  | 49.2 |  |  | 43.4 |
Derivatives | 33.3 |  |  | 7.2 |  |  | 8.8 |  |  | 3.6 |  |  | 24.5 |  |  | 3.6 |
IPL’s electric transmission cost recovery | 21.2 |  |  | 14.6 |  |  | 21.2 |  |  | 14.6 |  |  | — |  |  | — |
IPL’s electric transmission assets sale | 18.8 |  |  | 21.6 |  |  | 18.8 |  |  | 21.6 |  |  | — |  |  | — |
Other | 39.2 |  |  | 41.1 |  |  | 21.2 |  |  | 22.7 |  |  | 18.0 |  |  | 18.4 |
|  | $836.4 |  |  |  | $821.5 |  |  |  | $604.0 |  |  |  | $614.9 |  |  |  | $232.4 |  |  |  | $206.6 |
Tax Benefit Riders | For the three months ended March 31, 2014, Alliant Energy and IPL utilized “IPL’s tax benefit riders” regulatory liabilities to credit IPL’s Iowa retail electric and gas customers’ bills as follows (in millions):
Electric tax benefit rider |  | $23 |
Gas tax benefit rider | 3 |
|  | $26 |
WPL [Member] |
Regulatory Assets [Line Items] |
Regulatory Assets | Regulatory assets were comprised of the following items (in millions):
| Alliant Energy |  | IPL |  | WPL
| March 31, 2014 |  | December 31, 2013 |  | March 31, 2014 |  | December 31, 2013 |  | March 31, 2014 |  | December 31, 2013
Tax-related |  | $834.0 |  |  |  | $829.7 |  |  |  | $808.3 |  |  |  | $798.6 |  |  |  | $25.7 |  |  |  | $31.1 |
Pension and OPEB costs | 351.8 |  |  | 355.3 |  |  | 172.6 |  |  | 174.2 |  |  | 179.2 |  |  | 181.1 |
AROs | 68.5 |  |  | 65.7 |  |  | 38.6 |  |  | 36.7 |  |  | 29.9 |  |  | 29.0 |
Environmental-related costs | 27.8 |  |  | 25.0 |  |  | 23.0 |  |  | 21.0 |  |  | 4.8 |  |  | 4.0 |
Emission allowances | 29.2 |  |  | 30.0 |  |  | 29.2 |  |  | 30.0 |  |  | — |  |  | — |
Derivatives | 9.1 |  |  | 21.1 |  |  | 2.5 |  |  | 5.9 |  |  | 6.6 |  |  | 15.2 |
Other | 96.9 |  |  | 86.4 |  |  | 43.8 |  |  | 47.1 |  |  | 53.1 |  |  | 39.3 |
|  | $1,417.3 |  |  |  | $1,413.2 |  |  |  | $1,118.0 |  |  |  | $1,113.5 |  |  |  | $299.3 |  |  |  | $299.7 |
Regulatory Liabilities | Regulatory liabilities were comprised of the following items (in millions):
| Alliant Energy |  | IPL |  | WPL
| March 31, 2014 |  | December 31, 2013 |  | March 31, 2014 |  | December 31, 2013 |  | March 31, 2014 |  | December 31, 2013
Cost of removal obligations |  | $420.0 |  |  |  | $418.9 |  |  |  | $279.3 |  |  |  | $277.7 |  |  |  | $140.7 |  |  |  | $141.2 |
IPL’s tax benefit riders | 239.8 |  |  | 265.4 |  |  | 239.8 |  |  | 265.4 |  |  | — |  |  | — |
Energy efficiency cost recovery | 64.1 |  |  | 52.7 |  |  | 14.9 |  |  | 9.3 |  |  | 49.2 |  |  | 43.4 |
Derivatives | 33.3 |  |  | 7.2 |  |  | 8.8 |  |  | 3.6 |  |  | 24.5 |  |  | 3.6 |
IPL’s electric transmission cost recovery | 21.2 |  |  | 14.6 |  |  | 21.2 |  |  | 14.6 |  |  | — |  |  | — |
IPL’s electric transmission assets sale | 18.8 |  |  | 21.6 |  |  | 18.8 |  |  | 21.6 |  |  | — |  |  | — |
Other | 39.2 |  |  | 41.1 |  |  | 21.2 |  |  | 22.7 |  |  | 18.0 |  |  | 18.4 |
|  | $836.4 |  |  |  | $821.5 |  |  |  | $604.0 |  |  |  | $614.9 |  |  |  | $232.4 |  |  |  | $206.6 |

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- Definition Tabular disclosure of assets that are created when regulatory agencies permit public utilities to defer certain costs included in rate-setting to the balance sheet. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 980 -SubTopic 340 -Section 50 -Paragraph 1 -URI http://asc.fasb.org/extlink&oid=6499975&loc=d3e44250-110382 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 980 -SubTopic 715 -Section 50 -Paragraph 1 -URI http://asc.fasb.org/extlink&oid=6501251&loc=d3e52485-110419 Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 980 -SubTopic 340 -Section 50 -Paragraph 2 -URI http://asc.fasb.org/extlink&oid=6499975&loc=d3e44264-110382 + Details
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- Definition Tabular disclosure of regulatory liabilities. Detailed information about liabilities that result from rate actions of a regulator. Rate actions of a regulator can impose a liability on a regulated enterprise resulting in a regulatory liability. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 980 -SubTopic 405 -Section 25 -Paragraph 1 -URI http://asc.fasb.org/extlink&oid=6500807&loc=d3e48068-110394 + Details
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