XML 51 R31.htm IDEA: XBRL DOCUMENT v3.21.2
Asset Retirement Obligations (Tables)
 9 Months Ended
Sep. 30, 2021
Schedule of Asset Retirement Obligations [Line Items]  
Reconciliation of Changes in Asset Retirement Obligations
A reconciliation of the changes in asset retirement obligations associated with long-lived assets for the nine months ended September 30, 2021 is as follows (in millions):
Alliant EnergyIPL
Balance, January 1$251$177
Revisions in estimated cash flows 3732
Liabilities settled(10)(8)
Liabilities incurred1—
Accretion expense64
Balance, September 30
$285$205
IPL [Member]  
Schedule of Asset Retirement Obligations [Line Items]  
Reconciliation of Changes in Asset Retirement Obligations
A reconciliation of the changes in asset retirement obligations associated with long-lived assets for the nine months ended September 30, 2021 is as follows (in millions):
Alliant EnergyIPL
Balance, January 1$251$177
Revisions in estimated cash flows 3732
Liabilities settled(10)(8)
Liabilities incurred1—
Accretion expense64
Balance, September 30
$285$205