Condensed Consolidated Balance Sheets (Parenthetical) (USD $)	Mar. 31, 2015	Dec. 31, 2014
Common stock, par value	$ 0.01	$ 0.01
Common stock, shares authorized (in shares)	240,000,000us-gaap_CommonStockSharesAuthorized	240,000,000us-gaap_CommonStockSharesAuthorized
Common stock, shares outstanding (in shares)	112,977,238us-gaap_CommonStockSharesOutstanding	110,935,680us-gaap_CommonStockSharesOutstanding
Shares in deferred compensation trust (in shares)	232,550lnt_CommonStockHeldInTrustShares	238,935lnt_CommonStockHeldInTrustShares
Shares in deferred compensation trust, weighted average cost per share (in dollars per share)	$ 38.27	$ 37.45
IPL [Member]
Common stock, par value	$ 2.50	$ 2.50
Common stock, shares authorized (in shares)	24,000,000	24,000,000
Common stock, shares outstanding (in shares)	13,370,788	13,370,788
WPL [Member]
Common stock, par value	$ 5.00	$ 5.00
Common stock, shares authorized (in shares)	18,000,000	18,000,000
Common stock, shares outstanding (in shares)	13,236,601	13,236,601

Total number of common stock shares held in trust.

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Weighted average value per share; generally not indicative of the fair market value per share.

+ References

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Face amount or stated value per share of common stock.

+ References

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 210

-SubTopic 10

-Section S99

-Paragraph 1

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The maximum number of common shares permitted to be issued by an entity's charter and bylaws.

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- Definition

Number of shares of common stock outstanding. Common stock represent the ownership interest in a corporation.

+ References

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

-Publisher SEC

-Name Regulation S-X (SX)

-Number 210

-Section 04

-Article 3

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

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-Name Accounting Standards Codification

-Topic 505

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