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Benefit Plans (Tables)
 6 Months Ended
Jun. 30, 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 and six months ended June 30 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
Three MonthsSix MonthsThree MonthsSix Months
Alliant Energy20232022202320222023202220232022
Service cost$1$2$2$4$—$1$1$2
Interest cost12923182243
Expected return on plan assets(13)(17)(26)(34)(1)(2)(2)(3)
Amortization of actuarial loss7814161—11
$7$2$13$4$2$1$4$3
Defined Benefit Pension PlansOPEB Plans
Three MonthsSix MonthsThree MonthsSix Months
IPL20232022202320222023202220232022
Service cost$1$1$2$3$—$1$—$1
Interest cost541081—21
Expected return on plan assets(6)(8)(13)(16)(1)(1)(2)(2)
Amortization of actuarial loss34671—1—
$3$1$5$2$1$—$1$—
Defined Benefit Pension PlansOPEB Plans
Three MonthsSix MonthsThree MonthsSix Months
WPL20232022202320222023202220232022
Service cost$1$1$1$2$—$—$—$—
Interest cost541081—21
Expected return on plan assets(6)(8)(11)(16)————
Amortization of actuarial loss4478—1—1
$4$1$7$2$1$1$2$2
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 and six months ended June 30 was as follows (in millions):
Alliant EnergyIPLWPL
Three MonthsSix Months Three MonthsSix Months Three MonthsSix Months
202320222023202220232022202320222023202220232022
Compensation expense$3$3$6$7$2$1$3$4$1$1$2$3
Income tax benefits1122——11——11
Schedule Of Equity-based Compensation Plans Activity
For the six months ended June 30, 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 shares106,927$55.68
Performance restricted stock units122,17852.77
Restricted stock units104,84952.81
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 and six months ended June 30 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
Three MonthsSix MonthsThree MonthsSix Months
Alliant Energy20232022202320222023202220232022
Service cost$1$2$2$4$—$1$1$2
Interest cost12923182243
Expected return on plan assets(13)(17)(26)(34)(1)(2)(2)(3)
Amortization of actuarial loss7814161—11
$7$2$13$4$2$1$4$3
Defined Benefit Pension PlansOPEB Plans
Three MonthsSix MonthsThree MonthsSix Months
IPL20232022202320222023202220232022
Service cost$1$1$2$3$—$1$—$1
Interest cost541081—21
Expected return on plan assets(6)(8)(13)(16)(1)(1)(2)(2)
Amortization of actuarial loss34671—1—
$3$1$5$2$1$—$1$—
Defined Benefit Pension PlansOPEB Plans
Three MonthsSix MonthsThree MonthsSix Months
WPL20232022202320222023202220232022
Service cost$1$1$1$2$—$—$—$—
Interest cost541081—21
Expected return on plan assets(6)(8)(11)(16)————
Amortization of actuarial loss4478—1—1
$4$1$7$2$1$1$2$2
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 and six months ended June 30 was as follows (in millions):
Alliant EnergyIPLWPL
Three MonthsSix Months Three MonthsSix Months Three MonthsSix Months
202320222023202220232022202320222023202220232022
Compensation expense$3$3$6$7$2$1$3$4$1$1$2$3
Income tax benefits1122——11——11
Schedule Of Equity-based Compensation Plans Activity
For the six months ended June 30, 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 shares106,927$55.68
Performance restricted stock units122,17852.77
Restricted stock units104,84952.81
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 and six months ended June 30 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
Three MonthsSix MonthsThree MonthsSix Months
Alliant Energy20232022202320222023202220232022
Service cost$1$2$2$4$—$1$1$2
Interest cost12923182243
Expected return on plan assets(13)(17)(26)(34)(1)(2)(2)(3)
Amortization of actuarial loss7814161—11
$7$2$13$4$2$1$4$3
Defined Benefit Pension PlansOPEB Plans
Three MonthsSix MonthsThree MonthsSix Months
IPL20232022202320222023202220232022
Service cost$1$1$2$3$—$1$—$1
Interest cost541081—21
Expected return on plan assets(6)(8)(13)(16)(1)(1)(2)(2)
Amortization of actuarial loss34671—1—
$3$1$5$2$1$—$1$—
Defined Benefit Pension PlansOPEB Plans
Three MonthsSix MonthsThree MonthsSix Months
WPL20232022202320222023202220232022
Service cost$1$1$1$2$—$—$—$—
Interest cost541081—21
Expected return on plan assets(6)(8)(11)(16)————
Amortization of actuarial loss4478—1—1
$4$1$7$2$1$1$2$2
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 and six months ended June 30 was as follows (in millions):
Alliant EnergyIPLWPL
Three MonthsSix Months Three MonthsSix Months Three MonthsSix Months
202320222023202220232022202320222023202220232022
Compensation expense$3$3$6$7$2$1$3$4$1$1$2$3
Income tax benefits1122——11——11
Schedule Of Equity-based Compensation Plans Activity
For the six months ended June 30, 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 shares106,927$55.68
Performance restricted stock units122,17852.77
Restricted stock units104,84952.81