|
Summary Of Significant Accounting Policies (Regulatory Liabilities) (Details) (USD $)
In Millions, unless otherwise specified |
Dec. 31, 2012
|
Dec. 31, 2011
|
|---|---|---|
| Regulatory Liabilities [Line Items] | ||
| Regulatory liabilities | $ 916.1 | $ 910.1 |
|
IPL [Member]
|
||
| Regulatory Liabilities [Line Items] | ||
| Regulatory liabilities | 701.4 | 721.3 |
|
WPL [Member]
|
||
| Regulatory Liabilities [Line Items] | ||
| Regulatory liabilities | 214.7 | 188.8 |
|
Cost of removal obligations [Member]
|
||
| Regulatory Liabilities [Line Items] | ||
| Regulatory liabilities | 408.7 | 404.9 |
|
Cost of removal obligations [Member] | IPL [Member]
|
||
| Regulatory Liabilities [Line Items] | ||
| Regulatory liabilities | 268.0 | 261.9 |
|
Cost of removal obligations [Member] | WPL [Member]
|
||
| Regulatory Liabilities [Line Items] | ||
| Regulatory liabilities | 140.7 | 143.0 |
|
IPL's tax benefit rider [Member]
|
||
| Regulatory Liabilities [Line Items] | ||
| Regulatory liabilities | 355.8 | 349.6 |
|
IPL's tax benefit rider [Member] | IPL [Member]
|
||
| Regulatory Liabilities [Line Items] | ||
| Regulatory liabilities | 355.8 | 349.6 |
|
IPL's tax benefit rider [Member] | WPL [Member]
|
||
| Regulatory Liabilities [Line Items] | ||
| Regulatory liabilities | 0 | 0 |
|
Energy conservation cost recovery [Member]
|
||
| Regulatory Liabilities [Line Items] | ||
| Regulatory liabilities | 55.1 | 29.6 |
|
Energy conservation cost recovery [Member] | IPL [Member]
|
||
| Regulatory Liabilities [Line Items] | ||
| Regulatory liabilities | 10.0 | 4.7 |
|
Energy conservation cost recovery [Member] | WPL [Member]
|
||
| Regulatory Liabilities [Line Items] | ||
| Regulatory liabilities | 45.1 | 24.9 |
|
IPL's electric transmission assets sale [Member]
|
||
| Regulatory Liabilities [Line Items] | ||
| Regulatory liabilities | 32.5 | 45.1 |
|
IPL's electric transmission assets sale [Member] | IPL [Member]
|
||
| Regulatory Liabilities [Line Items] | ||
| Regulatory liabilities | 32.5 | 45.1 |
|
IPL's electric transmission assets sale [Member] | WPL [Member]
|
||
| Regulatory Liabilities [Line Items] | ||
| Regulatory liabilities | 0 | 0 |
|
Commodity cost recovery [Member]
|
||
| Regulatory Liabilities [Line Items] | ||
| Regulatory liabilities | 17.7 | 23.8 |
|
Commodity cost recovery [Member] | IPL [Member]
|
||
| Regulatory Liabilities [Line Items] | ||
| Regulatory liabilities | 5.2 | 23.2 |
|
Commodity cost recovery [Member] | WPL [Member]
|
||
| Regulatory Liabilities [Line Items] | ||
| Regulatory liabilities | 12.5 | 0.6 |
|
IPL's DAEC Sale [Member]
|
||
| Regulatory Liabilities [Line Items] | ||
| Regulatory liabilities | 9.5 | 14.6 |
|
IPL's DAEC Sale [Member] | IPL [Member]
|
||
| Regulatory Liabilities [Line Items] | ||
| Regulatory liabilities | 9.5 | 14.6 |
|
IPL's DAEC Sale [Member] | WPL [Member]
|
||
| Regulatory Liabilities [Line Items] | ||
| Regulatory liabilities | 0 | 0 |
|
Other [Member]
|
||
| Regulatory Liabilities [Line Items] | ||
| Regulatory liabilities | 36.8 | 42.5 |
|
Other [Member] | IPL [Member]
|
||
| Regulatory Liabilities [Line Items] | ||
| Regulatory liabilities | 20.4 | 22.2 |
|
Other [Member] | WPL [Member]
|
||
| Regulatory Liabilities [Line Items] | ||
| Regulatory liabilities | $ 16.4 | $ 20.3 |