XML 70 R36.htm IDEA: XBRL DOCUMENT
v3.8.0.1

Common Equity (Tables) | 12 Months Ended
--- | ---
Dec. 31, 2017
Schedule of Common Equity [Line Items] |
Common Stock Activity | A summary of Alliant Energy’s common stock activity was as follows:
| 2017 |  | 2016 |  | 2015
Shares outstanding, January 1 | 227,673,654 |  |  | 226,918,432 |  |  | 221,871,360 |
At-the-market offering programs | 3,074,931 |  |  | — |  |  | 4,373,234 |
Shareowner Direct Plan issuances | 640,723 |  |  | 732,814 |  |  | 606,010 |
Equity-based compensation plans (Note 12(b)) | 5,185 |  |  | 22,408 |  |  | 112,756 |
Other | (45,847 | ) |  | — |  |  | (44,928 | )
Shares outstanding, December 31 | 231,348,646 |  |  | 227,673,654 |  |  | 226,918,432 |

X
- Definition [Line Items] for Schedule of Common Equity [Table] + References No definition available. + Details
Name: | lnt_ScheduleOfCommonEquityLineItems
Namespace Prefix: | lnt_
Data Type: | xbrli:stringItemType
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