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Benefit Plans (Tables)
 3 Months Ended
Mar. 31, 2024
Defined Benefit Plan Disclosure [Line Items]  
Net Periodic Benefit Costs The components of net periodic benefit costs for sponsored defined benefit pension and OPEB plans for the three months ended March 31 are included below (in millions). For IPL and WPL, amounts are for their plan participants covered under plans they sponsor, as well as amounts directly assigned to them related to certain participants in the Alliant Energy and Corporate Services sponsored plans.
Defined Benefit Pension PlansOPEB Plans
Alliant Energy2024202320242023
Service cost$1$1$—$1
Interest cost111122
Expected return on plan assets(13)(13)(1)(1)
Amortization of actuarial loss67——
$5$6$1$2
Defined Benefit Pension PlansOPEB Plans
IPL2024202320242023
Service cost$1$1$—$—
Interest cost5511
Expected return on plan assets(7)(7)(1)(1)
Amortization of actuarial loss23——
$1$2$—$—
Defined Benefit Pension PlansOPEB Plans
WPL2024202320242023
Interest cost$5$5$1$1
Expected return on plan assets(6)(5)——
Amortization of actuarial loss33——
$2$3$1$1
Recognized Compensation Expense And Income Tax Benefits A summary of compensation expense, including amounts allocated to IPL and WPL, and the related income tax benefits recognized for share-based compensation awards for the three months ended March 31 was as follows (in millions):
Alliant EnergyIPLWPL
202420232024202320242023
Compensation expense$4$3$2$2$2$1
Income tax benefits111———
Schedule Of Equity-based Compensation Plans Activity
For the three months ended March 31, 2024, performance shares and restricted stock units were granted to key employees under the equity-based compensation plans as follows. These shares and units will be paid out in shares of common stock, and are therefore accounted for as equity awards.
Weighted Average
GrantsGrant Date Fair Value
Performance shares (total shareowner return metric)123,098$46.04
Performance shares (net income and diversity metrics) (formerly granted as performance restricted stock units)140,68348.40
Restricted stock units120,55748.40
IPL [Member]  
Defined Benefit Plan Disclosure [Line Items]  
Net Periodic Benefit Costs The components of net periodic benefit costs for sponsored defined benefit pension and OPEB plans for the three months ended March 31 are included below (in millions). For IPL and WPL, amounts are for their plan participants covered under plans they sponsor, as well as amounts directly assigned to them related to certain participants in the Alliant Energy and Corporate Services sponsored plans.
Defined Benefit Pension PlansOPEB Plans
Alliant Energy2024202320242023
Service cost$1$1$—$1
Interest cost111122
Expected return on plan assets(13)(13)(1)(1)
Amortization of actuarial loss67——
$5$6$1$2
Defined Benefit Pension PlansOPEB Plans
IPL2024202320242023
Service cost$1$1$—$—
Interest cost5511
Expected return on plan assets(7)(7)(1)(1)
Amortization of actuarial loss23——
$1$2$—$—
Defined Benefit Pension PlansOPEB Plans
WPL2024202320242023
Interest cost$5$5$1$1
Expected return on plan assets(6)(5)——
Amortization of actuarial loss33——
$2$3$1$1
Recognized Compensation Expense And Income Tax Benefits A summary of compensation expense, including amounts allocated to IPL and WPL, and the related income tax benefits recognized for share-based compensation awards for the three months ended March 31 was as follows (in millions):
Alliant EnergyIPLWPL
202420232024202320242023
Compensation expense$4$3$2$2$2$1
Income tax benefits111———
Schedule Of Equity-based Compensation Plans Activity
For the three months ended March 31, 2024, performance shares and restricted stock units were granted to key employees under the equity-based compensation plans as follows. These shares and units will be paid out in shares of common stock, and are therefore accounted for as equity awards.
Weighted Average
GrantsGrant Date Fair Value
Performance shares (total shareowner return metric)123,098$46.04
Performance shares (net income and diversity metrics) (formerly granted as performance restricted stock units)140,68348.40
Restricted stock units120,55748.40
WPL [Member]  
Defined Benefit Plan Disclosure [Line Items]  
Net Periodic Benefit Costs The components of net periodic benefit costs for sponsored defined benefit pension and OPEB plans for the three months ended March 31 are included below (in millions). For IPL and WPL, amounts are for their plan participants covered under plans they sponsor, as well as amounts directly assigned to them related to certain participants in the Alliant Energy and Corporate Services sponsored plans.
Defined Benefit Pension PlansOPEB Plans
Alliant Energy2024202320242023
Service cost$1$1$—$1
Interest cost111122
Expected return on plan assets(13)(13)(1)(1)
Amortization of actuarial loss67——
$5$6$1$2
Defined Benefit Pension PlansOPEB Plans
IPL2024202320242023
Service cost$1$1$—$—
Interest cost5511
Expected return on plan assets(7)(7)(1)(1)
Amortization of actuarial loss23——
$1$2$—$—
Defined Benefit Pension PlansOPEB Plans
WPL2024202320242023
Interest cost$5$5$1$1
Expected return on plan assets(6)(5)——
Amortization of actuarial loss33——
$2$3$1$1
Recognized Compensation Expense And Income Tax Benefits A summary of compensation expense, including amounts allocated to IPL and WPL, and the related income tax benefits recognized for share-based compensation awards for the three months ended March 31 was as follows (in millions):
Alliant EnergyIPLWPL
202420232024202320242023
Compensation expense$4$3$2$2$2$1
Income tax benefits111———
Schedule Of Equity-based Compensation Plans Activity
For the three months ended March 31, 2024, performance shares and restricted stock units were granted to key employees under the equity-based compensation plans as follows. These shares and units will be paid out in shares of common stock, and are therefore accounted for as equity awards.
Weighted Average
GrantsGrant Date Fair Value
Performance shares (total shareowner return metric)123,098$46.04
Performance shares (net income and diversity metrics) (formerly granted as performance restricted stock units)140,68348.40
Restricted stock units120,55748.40