XML 104 R41.htm IDEA: XBRL DOCUMENT
v2.4.0.8

Regulatory Matters Regulatory Matters (Tax Benefit Riders) (Details) (USD $) In Millions, unless otherwise specified | 6 Months Ended
--- | ---
Jun. 30, 2014 | Jun. 30, 2013
Regulatory Liabilities [Line Items] |  |
Increase (decrease) in regulatory liabilities | $ 45.2 | $ (15.1)
Alliant Energy and IPL [Member] | Electric tax benefit rider [Member] |  |
Regulatory Liabilities [Line Items] |  |
Increase (decrease) in regulatory liabilities | (42.0) |
Alliant Energy and IPL [Member] | Gas tax benefit rider [Member] |  |
Regulatory Liabilities [Line Items] |  |
Increase (decrease) in regulatory liabilities | (6.0) |
Alliant Energy and IPL [Member] | Tax benefit riders [Member] |  |
Regulatory Liabilities [Line Items] |  |
Increase (decrease) in regulatory liabilities | $ (48.0) |

X
- Definition The increase (decrease) during the reporting period in regulated liabilities. Regulated liabilities are created when regulatory agency permits an entity to defer revenues to the balance sheet. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 230 -SubTopic 10 -Section 45 -Paragraph 28 -Subparagraph (a) -URI http://asc.fasb.org/extlink&oid=31042434&loc=d3e3602-108585 + Details
Name: | us-gaap_IncreaseDecreaseInRegulatoryLiabilities
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | duration

X
- Details
Name: | us-gaap_RegulatoryLiabilitiesLineItems
Namespace Prefix: | us-gaap_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration