| Document and Entity Information Document | Apr. 03, 2020 |
| Entity Information [Line Items] | |
| Document Type | 8-K |
| Document Period End Date | Apr. 3, 2020 |
| Entity Registrant Name | ALLIANT ENERGY CORP |
| Entity Central Index Key | 0000352541 |
| Amendment Flag | false |
| Entity Incorporation, State or Country Code | WI |
| Entity Address, Address Line One | 4902 N. Biltmore Lane |
| Entity Address, City or Town | Madison |
| Entity Address, State or Province | WI |
| Entity Address, Postal Zip Code | 53718 |
| City Area Code | 608 |
| Local Phone Number | 458-3311 |
| Entity File Number | 1-9894 |
| Entity Tax Identification Number | 39-1380265 |
| Written Communications | false |
| Soliciting Material | false |
| Pre-commencement Tender Offer | false |
| Pre-commencement Issuer Tender Offer | false |
| Title of 12(b) Security | Common Stock, $0.01 Par Value |
| Trading Symbol | LNT |
| Security Exchange Name | NASDAQ |
| Entity Emerging Growth Company | false |
