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Asset Retirement Obligations
 12 Months Ended
Dec. 31, 2023
Schedule of Asset Retirement Obligations [Line Items]  
Asset Retirement Obligations (AROs) ASSET RETIREMENT OBLIGATIONS
Recognized AROs relate to legal obligations for the removal, closure, dismantlement and management of several assets including, but not limited to, wind farms, active ash landfills, ash ponds, solar generation, above ground storage tanks and batteries. Recognized AROs also include legal obligations for the management and final disposition of asbestos and polychlorinated biphenyls. AROs are recorded in “Other current liabilities” and “Other liabilities” on the balance sheets. Refer to Note 2 for information regarding regulatory assets related to AROs. A reconciliation of the changes in AROs associated with long-lived assets is as follows (in millions):
Alliant EnergyIPLWPL
202320222023202220232022
Balance, January 1$279 $294 $195 $213 $84 $81 
Revisions in estimated cash flows(6)19 (9)15 3 4 
Liabilities settled(51)(48)(44)(39)(7)(9)
Liabilities incurred16 6 1 — 15 6 
Accretion expense8 8 5 6 3 2 
Balance, December 31$246 $279 $148 $195 $98 $84 
IPL [Member]  
Schedule of Asset Retirement Obligations [Line Items]  
Asset Retirement Obligations (AROs) ASSET RETIREMENT OBLIGATIONS
Recognized AROs relate to legal obligations for the removal, closure, dismantlement and management of several assets including, but not limited to, wind farms, active ash landfills, ash ponds, solar generation, above ground storage tanks and batteries. Recognized AROs also include legal obligations for the management and final disposition of asbestos and polychlorinated biphenyls. AROs are recorded in “Other current liabilities” and “Other liabilities” on the balance sheets. Refer to Note 2 for information regarding regulatory assets related to AROs. A reconciliation of the changes in AROs associated with long-lived assets is as follows (in millions):
Alliant EnergyIPLWPL
202320222023202220232022
Balance, January 1$279 $294 $195 $213 $84 $81 
Revisions in estimated cash flows(6)19 (9)15 3 4 
Liabilities settled(51)(48)(44)(39)(7)(9)
Liabilities incurred16 6 1 — 15 6 
Accretion expense8 8 5 6 3 2 
Balance, December 31$246 $279 $148 $195 $98 $84 
WPL [Member]  
Schedule of Asset Retirement Obligations [Line Items]  
Asset Retirement Obligations (AROs) ASSET RETIREMENT OBLIGATIONS
Recognized AROs relate to legal obligations for the removal, closure, dismantlement and management of several assets including, but not limited to, wind farms, active ash landfills, ash ponds, solar generation, above ground storage tanks and batteries. Recognized AROs also include legal obligations for the management and final disposition of asbestos and polychlorinated biphenyls. AROs are recorded in “Other current liabilities” and “Other liabilities” on the balance sheets. Refer to Note 2 for information regarding regulatory assets related to AROs. A reconciliation of the changes in AROs associated with long-lived assets is as follows (in millions):
Alliant EnergyIPLWPL
202320222023202220232022
Balance, January 1$279 $294 $195 $213 $84 $81 
Revisions in estimated cash flows(6)19 (9)15 3 4 
Liabilities settled(51)(48)(44)(39)(7)(9)
Liabilities incurred16 6 1 — 15 6 
Accretion expense8 8 5 6 3 2 
Balance, December 31$246 $279 $148 $195 $98 $84