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Benefit Plans (Tables)
 3 Months Ended
Mar. 31, 2023
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 Energy2023202220232022
Service cost$1$2$1$1
Interest cost11921
Expected return on plan assets(13)(17)(1)(1)
Amortization of actuarial loss78—1
$6$2$2$2
Defined Benefit Pension PlansOPEB Plans
IPL2023202220232022
Service cost$1$2$—$—
Interest cost5411
Expected return on plan assets(7)(8)(1)(1)
Amortization of actuarial loss33——
$2$1$—$—
Defined Benefit Pension PlansOPEB Plans
WPL2023202220232022
Service cost$—$1$—$—
Interest cost5411
Expected return on plan assets(5)(8)——
Amortization of actuarial loss34——
$3$1$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
202320222023202220232022
Compensation expense$3$4$2$2$1$2
Income tax benefits11—1——
Schedule Of Equity-based Compensation Plans Activity
For the three months ended March 31, 2023, performance shares, performance restricted stock units and restricted stock units were granted to key employees under existing 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 shares100,055$55.68
Performance restricted stock units114,32552.73
Restricted stock units99,94152.78
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 Energy2023202220232022
Service cost$1$2$1$1
Interest cost11921
Expected return on plan assets(13)(17)(1)(1)
Amortization of actuarial loss78—1
$6$2$2$2
Defined Benefit Pension PlansOPEB Plans
IPL2023202220232022
Service cost$1$2$—$—
Interest cost5411
Expected return on plan assets(7)(8)(1)(1)
Amortization of actuarial loss33——
$2$1$—$—
Defined Benefit Pension PlansOPEB Plans
WPL2023202220232022
Service cost$—$1$—$—
Interest cost5411
Expected return on plan assets(5)(8)——
Amortization of actuarial loss34——
$3$1$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
202320222023202220232022
Compensation expense$3$4$2$2$1$2
Income tax benefits11—1——
Schedule Of Equity-based Compensation Plans Activity
For the three months ended March 31, 2023, performance shares, performance restricted stock units and restricted stock units were granted to key employees under existing 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 shares100,055$55.68
Performance restricted stock units114,32552.73
Restricted stock units99,94152.78
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 Energy2023202220232022
Service cost$1$2$1$1
Interest cost11921
Expected return on plan assets(13)(17)(1)(1)
Amortization of actuarial loss78—1
$6$2$2$2
Defined Benefit Pension PlansOPEB Plans
IPL2023202220232022
Service cost$1$2$—$—
Interest cost5411
Expected return on plan assets(7)(8)(1)(1)
Amortization of actuarial loss33——
$2$1$—$—
Defined Benefit Pension PlansOPEB Plans
WPL2023202220232022
Service cost$—$1$—$—
Interest cost5411
Expected return on plan assets(5)(8)——
Amortization of actuarial loss34——
$3$1$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
202320222023202220232022
Compensation expense$3$4$2$2$1$2
Income tax benefits11—1——
Schedule Of Equity-based Compensation Plans Activity
For the three months ended March 31, 2023, performance shares, performance restricted stock units and restricted stock units were granted to key employees under existing 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 shares100,055$55.68
Performance restricted stock units114,32552.73
Restricted stock units99,94152.78