v2.4.0.6

Common Equity (Narrative) (Details) (USD $) In Millions, except Share data, unless otherwise specified	12 Months Ended
	Dec. 31, 2012
Schedule of Common Equity [Line Items]
Shares available for issuance under the OIP, Shareowner Direct Plan and 401k Savings Plan	8,400,000
Ownership percentage	15.00%
Initial right entitlement, number of shares of common stock shareholders have the option to purchase (in shares)	0.5
Exercise price, rights (in dollars per share)	110
Percentage of exercise price upon change in beneficial ownership	200.00%
IPL [Member]
Schedule of Common Equity [Line Items]
Common equity ratio, computation of ratio average, number of months	13 months
Common equity ratio	42.00%
Retained earnings free of dividend restrictions	$ 387
WPL [Member]
Schedule of Common Equity [Line Items]
Common equity ratio, computation of ratio average, number of months	13 months
Common equity ratio	51.03%
Retained earnings free of dividend restrictions	$ 119
Minimum [Member]
Schedule of Common Equity [Line Items]
Ownership percentage	10.00%
Minimum [Member] | WPL [Member]
Schedule of Common Equity [Line Items]
Common equity ratio	25.00%

X

- Definition

The rights under the Company Shareowner Rights Agreement will only become exercisable if a person or group has acquired, or announced an intention to acquire, 15% or more of the Company's outstanding common stock.

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Class of Warrant or Right, Exercise Price of Warrant or Right, Percentage of Exercise Price Upon Change in Beneficial Ownership

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- Definition

Class of Warrant or Right, Initial Right Entitlement, Number of Shares of Common Stock Shareholders Have the Option to Purchase

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- Definition

Common Equity Ratio, Computation of Ratio Average, Number of Months

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- Definition

Regulatory restrictions imposed if the common equity ratio falls below a certain percentage of total capitalization.

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- Definition

Shares available for issuance under equity incentive plans, 401(k) savings plan and shareowner direct plan.

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- Definition

The exercise price of each class of warrants or rights outstanding.

+ References

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 235

-SubTopic 10

-Section S99

-Paragraph 1

-Subparagraph (SX 210.4-08.(i)(4))

-URI http://asc.fasb.org/extlink&oid=6881521&loc=d3e23780-122690



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-Publisher SEC

-Name Regulation S-X (SX)

-Number 210

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A segregation of retained earnings which is available for dividend distribution. Earnings not paid out as dividends but instead reinvested in the core business or used to pay off debt. Unappropriated profit is part of shareholder equity. Also called cumulative distributions or earned surplus or accumulated earnings or unappropriated profit.

+ References

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

-Publisher SEC

-Name Regulation S-X (SX)

-Number 210

-Section 03

-Paragraph 24

-Subparagraph a(4)

-Article 7



Reference 2: http://www.xbrl.org/2003/role/presentationRef

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-Name Regulation S-X (SX)

-Number 210

-Section 02

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Reference 3: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 210

-SubTopic 10

-Section S99

-Paragraph 1

-Subparagraph (SX 210.5-02.30(a)(3)(ii))

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-Publisher FASB

-Name Accounting Standards Codification

-Topic 944

-SubTopic 210

-Section S99

-Paragraph 1

-Subparagraph (SX 210.7-03.23(4))

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