Income Taxes (Narrative) (Details) $ in Millions	3 Months Ended
Mar. 31, 2016 USD ($)
Income Taxes [Line Items]
Increase (decrease) non-current deferred tax liabilities	$ 43.4
IPL [Member]
Income Taxes [Line Items]
Increase (decrease) non-current deferred tax liabilities	30.9
WPL [Member]
Income Taxes [Line Items]
Increase (decrease) non-current deferred tax liabilities	$ 19.7

The increase (decrease) during the reporting period in the account that represents the temporary difference that results from Income or Loss that is recognized for accounting purposes but not for tax purposes and vice versa.

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

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Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration