Benefit Plans (Fair Values Of Nonvested Performance Shares And Units) (Details)	12 Months Ended
Dec. 31, 2016 $ / shares shares
Performance Shares [Member]
Defined Benefit Plan Disclosure [Line Items]
Nonvested, December 31 (in shares/awards) \| shares	257,599
Performance Units [Member]
Defined Benefit Plan Disclosure [Line Items]
Nonvested, December 31 (in shares/awards) \| shares	93,320
2016 Grant [Member] \| Performance Shares [Member]
Defined Benefit Plan Disclosure [Line Items]
Nonvested, December 31 (in shares/awards) \| shares	67,355
Alliant Energy common stock closing price on December 30, 2016 (in dollars per share)	$ 37.89
Estimated payout percentage based on performance criteria	135.00%
Fair values of each nonvested award (in dollars per share)	$ 51.15
2016 Grant [Member] \| Performance Units [Member]
Defined Benefit Plan Disclosure [Line Items]
Nonvested, December 31 (in shares/awards) \| shares	22,657
Alliant Energy common stock closing price on December 30, 2016 (in dollars per share)	$ 37.89
Estimated payout percentage based on performance criteria	135.00%
Fair values of each nonvested award (in dollars per share)	$ 51.15
2015 Grant [Member] \| Performance Shares [Member]
Defined Benefit Plan Disclosure [Line Items]
Nonvested, December 31 (in shares/awards) \| shares	90,806
Alliant Energy common stock closing price on December 30, 2016 (in dollars per share)	$ 37.89
Estimated payout percentage based on performance criteria	155.00%
Fair values of each nonvested award (in dollars per share)	$ 58.73
2015 Grant [Member] \| Performance Units [Member]
Defined Benefit Plan Disclosure [Line Items]
Nonvested, December 31 (in shares/awards) \| shares	33,268
Alliant Energy common stock closing price on grant date (in dollars per share)	$ 32.55
Estimated payout percentage based on performance criteria	155.00%
Fair values of each nonvested award (in dollars per share)	$ 50.45
2014 Grant [Member] \| Performance Shares [Member]
Defined Benefit Plan Disclosure [Line Items]
Nonvested, December 31 (in shares/awards) \| shares	99,438
Alliant Energy common stock closing price on December 30, 2016 (in dollars per share)	$ 37.89
Estimated payout percentage based on performance criteria	148.00%
Fair values of each nonvested award (in dollars per share)	$ 56.08
2014 Grant [Member] \| Performance Units [Member]
Defined Benefit Plan Disclosure [Line Items]
Nonvested, December 31 (in shares/awards) \| shares	37,395
Alliant Energy common stock closing price on grant date (in dollars per share)	$ 26.89
Estimated payout percentage based on performance criteria	148.00%
Fair values of each nonvested award (in dollars per share)	$ 39.80

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- Definition

Employee Service Share Based Compensation Fair Values Of Each Nonvested Awards

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Estimated Payout Percentage

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- Definition

The number of non-vested equity-based payment instruments, excluding stock (or unit) options, that validly exist and are outstanding as of the balance sheet date.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 718
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (c)(2)(i)-(ii)
-URI http://asc.fasb.org/extlink&oid=6415400&loc=d3e5070-113901

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- Definition

Price of a single share of a number of saleable stocks of a company.

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