| Document and Entity Information Document | Sep. 19, 2019 |
| Entity Information [Line Items] | |
| Document Type | 8-K |
| Document Period End Date | Sep. 19, 2019 |
| 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 |
| IPL [Member] | |
| Entity Information [Line Items] | |
| Entity Registrant Name | INTERSTATE POWER & LIGHT CO |
| Entity Central Index Key | 0000052485 |
| Entity Incorporation, State or Country Code | IA |
| Entity Address, Address Line One | Alliant Energy Tower |
| Entity Address, City or Town | Cedar Rapids |
| Entity Address, State or Province | IA |
| Entity Address, Postal Zip Code | 52401 |
| City Area Code | 319 |
| Local Phone Number | 786-4411 |
| Entity File Number | 1-4117 |
| Entity Tax Identification Number | 42-0331370 |
| Title of 12(b) Security | 5.100% Series D Cumulative Perpetual Preferred Stock, $0.01 Par Value |
| Trading Symbol | IPLDP |
| Security Exchange Name | NASDAQ |
| Entity Emerging Growth Company | false |
