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Asset Retirement Obligations
 12 Months Ended
Dec. 31, 2021
Schedule of Asset Retirement Obligations [Line Items]  
Asset Retirement Obligations (AROs) ASSET RETIREMENT OBLIGATIONS
Recognized AROs relate to legal obligations for the removal, closure or dismantlement of several assets including, but not limited to, wind farms, ash ponds, active ash landfills, coal yards, above ground storage tanks and solar generation. 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
202120202021202020212020
Balance, January 1$251 $196 $177 $134 $74 $62 
Revisions in estimated cash flows50 13 44 9 6 4 
Liabilities settled(17)(13)(13)(9)(4)(4)
Liabilities incurred3 48 — 38 3 10 
Accretion expense7 7 5 5 2 2 
Balance, December 31$294 $251 $213 $177 $81 $74 
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 or dismantlement of several assets including, but not limited to, wind farms, ash ponds, active ash landfills, coal yards, above ground storage tanks and solar generation. 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
202120202021202020212020
Balance, January 1$251 $196 $177 $134 $74 $62 
Revisions in estimated cash flows50 13 44 9 6 4 
Liabilities settled(17)(13)(13)(9)(4)(4)
Liabilities incurred3 48 — 38 3 10 
Accretion expense7 7 5 5 2 2 
Balance, December 31$294 $251 $213 $177 $81 $74 
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 or dismantlement of several assets including, but not limited to, wind farms, ash ponds, active ash landfills, coal yards, above ground storage tanks and solar generation. 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
202120202021202020212020
Balance, January 1$251 $196 $177 $134 $74 $62 
Revisions in estimated cash flows50 13 44 9 6 4 
Liabilities settled(17)(13)(13)(9)(4)(4)
Liabilities incurred3 48 — 38 3 10 
Accretion expense7 7 5 5 2 2 
Balance, December 31$294 $251 $213 $177 $81 $74