v2.4.0.6

Common Equity (Tables)

12 Months Ended

Dec. 31, 2012

Schedule of Common Equity [Line Items]

Common Stock Activity

A summary of Alliant Energy’s common stock activity was as follows:

	2012			2011			2010
Shares outstanding, January 1	111,018,821			110,893,901			110,656,498
Equity-based compensation plans (Note 6(b))	20,195			164,400			260,316
Other (a)	(51,616	)		(39,480	)		(22,913	)
Shares outstanding, December 31	110,987,400			111,018,821			110,893,901

(a) Includes shares transferred from employees to Alliant Energy to satisfy tax withholding requirements in connection with the vesting of certain restricted stock under the equity-based compensation plans.

Schedule of Restricted Net Assets of Subsidiaries

As of December 31, the amount of net assets of IPL and WPL that were not available to be transferred to their parent company in the form of cash dividends without the consent of IPL’s and WPL’s regulatory authorities was as follows (in billions):

	2012				2011
IPL		$1.1				$1.0
WPL	1.5				1.3

Capital Transactions with Subsidiaries

IPL, WPL and Resources paid common stock dividends and repayments of capital to their parent company, Alliant Energy, as follows (in millions):

	IPL												WPL												Resources
	2012				2011				2010				2012				2011				2010				2012				2011				2010
Common stock dividends		$122.9				$73.4				$—				$112.0				$112.1				$109.5				$—				$—				$—
Repayments of capital	—				100.7				118.2				—				—				—				—				—				65.0
Total distributions from common equity		$122.9				$174.1				$118.2				$112.0				$112.1				$109.5				$—				$—				$65.0

Schedule of Capital Contributions

IPL, WPL, Resources and Corporate Services received capital contributions from their parent company, Alliant Energy, as follows (in millions):

	2012				2011				2010
IPL		$110.0				$54.0				$50.0
WPL	90.0				25.0				75.0
Resources	—				65.0				—
Corporate Services	30.0				—				—

IPL [Member]

Schedule of Common Equity [Line Items]

Schedule of Restricted Net Assets of Subsidiaries

As of December 31, the amount of net assets of IPL and WPL that were not available to be transferred to their parent company in the form of cash dividends without the consent of IPL’s and WPL’s regulatory authorities was as follows (in billions):

	2012				2011
IPL		$1.1				$1.0
WPL	1.5				1.3

Capital Transactions with Subsidiaries

IPL, WPL and Resources paid common stock dividends and repayments of capital to their parent company, Alliant Energy, as follows (in millions):

	IPL												WPL												Resources
	2012				2011				2010				2012				2011				2010				2012				2011				2010
Common stock dividends		$122.9				$73.4				$—				$112.0				$112.1				$109.5				$—				$—				$—
Repayments of capital	—				100.7				118.2				—				—				—				—				—				65.0
Total distributions from common equity		$122.9				$174.1				$118.2				$112.0				$112.1				$109.5				$—				$—				$65.0

Schedule of Capital Contributions

IPL, WPL, Resources and Corporate Services received capital contributions from their parent company, Alliant Energy, as follows (in millions):

	2012				2011				2010
IPL		$110.0				$54.0				$50.0
WPL	90.0				25.0				75.0
Resources	—				65.0				—
Corporate Services	30.0				—				—

WPL [Member]

Schedule of Common Equity [Line Items]

Schedule of Restricted Net Assets of Subsidiaries

As of December 31, the amount of net assets of IPL and WPL that were not available to be transferred to their parent company in the form of cash dividends without the consent of IPL’s and WPL’s regulatory authorities was as follows (in billions):

	2012				2011
IPL		$1.1				$1.0
WPL	1.5				1.3

Capital Transactions with Subsidiaries

IPL, WPL and Resources paid common stock dividends and repayments of capital to their parent company, Alliant Energy, as follows (in millions):

	IPL												WPL												Resources
	2012				2011				2010				2012				2011				2010				2012				2011				2010
Common stock dividends		$122.9				$73.4				$—				$112.0				$112.1				$109.5				$—				$—				$—
Repayments of capital	—				100.7				118.2				—				—				—				—				—				65.0
Total distributions from common equity		$122.9				$174.1				$118.2				$112.0				$112.1				$109.5				$—				$—				$65.0

Schedule of Capital Contributions

IPL, WPL, Resources and Corporate Services received capital contributions from their parent company, Alliant Energy, as follows (in millions):

	2012				2011				2010
IPL		$110.0				$54.0				$50.0
WPL	90.0				25.0				75.0
Resources	—				65.0				—
Corporate Services	30.0				—				—

X

- Definition

Schedule Of Capital Contributions [Table Text Block]

+ References

No definition available.

+ Details

Name:	lnt_ScheduleOfCapitalContributionsTableTextBlock
Namespace Prefix:	lnt_
Data Type:	nonnum:textBlockItemType
Balance Type:	na
Period Type:	duration

X

- Definition

Schedule of Capital Transactions with Subsidiaries [Table Text Block]

+ References

No definition available.

+ Details

Name:	lnt_ScheduleOfCapitalTransactionsWithSubsidiariesTableTextBlock
Namespace Prefix:	lnt_
Data Type:	nonnum:textBlockItemType
Balance Type:	na
Period Type:	duration

X

- Details

Name:	lnt_ScheduleOfCommonEquityLineItems
Namespace Prefix:	lnt_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

X

- Definition

Schedule Of Restricted Net Assets Of Subsidiaries [Table Text Block]

+ References

No definition available.

+ Details

Name:	lnt_ScheduleOfRestrictedNetAssetsOfSubsidiariesTableTextBlock
Namespace Prefix:	lnt_
Data Type:	nonnum:textBlockItemType
Balance Type:	na
Period Type:	duration

X

- Definition

Tabular disclosure of an entity's capital units or capital shares, including the value of capital units or capital shares, units authorized, units outstanding and other information necessary to a fair presentation.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 946

-SubTopic 210

-Section S99

-Paragraph 1

-Subparagraph (SX 210.6-04.16)

-URI http://asc.fasb.org/extlink&oid=6488278&loc=d3e603758-122996

+ Details

Name:	us-gaap_ScheduleOfCapitalUnitsTextBlock
Namespace Prefix:	us-gaap_
Data Type:	nonnum:textBlockItemType
Balance Type:	na
Period Type:	duration