Benefit Plans (Tables)

6 Months Ended

Jun. 30, 2021

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 Plans				OPEB Plans
	Three Months		Six Months		Three Months		Six Months
Alliant Energy	2021	2020	2021	2020	2021	2020	2021	2020
Service cost	$3	$2	$6	$5	$1	$1	$2	$2
Interest cost	9	11	17	22	1	1	2	3
Expected return on plan assets	(17)	(17)	(34)	(35)	(1)	(1)	(2)	(3)
Amortization of actuarial loss	9	8	19	17	1	1	2	2
Settlement losses (a)	—	—	—	4	—	—	—	—
	$4	$4	$8	$13	$2	$2	$4	$4

	Defined Benefit Pension Plans				OPEB Plans
	Three Months		Six Months		Three Months		Six Months
IPL	2021	2020	2021	2020	2021	2020	2021	2020
Service cost	$2	$2	$4	$3	$1	$1	$1	$1
Interest cost	4	5	8	10	—	—	1	1
Expected return on plan assets	(8)	(8)	(16)	(16)	(1)	(1)	(2)	(2)
Amortization of actuarial loss	4	3	8	7	1	1	1	1
	$2	$2	$4	$4	$1	$1	$1	$1

	Defined Benefit Pension Plans				OPEB Plans
	Three Months		Six Months		Three Months		Six Months
WPL	2021	2020	2021	2020	2021	2020	2021	2020
Service cost	$1	$1	$2	$2	$—	$1	$—	$1
Interest cost	4	4	8	9	1	—	1	1
Expected return on plan assets	(7)	(7)	(15)	(15)	—	—	—	—
Amortization of actuarial loss	4	4	9	8	—	1	1	1
	$2	$2	$4	$4	$1	$2	$2	$3

(a)Settlement losses related to payments made to retired executives of Alliant Energy.

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 Energy				IPL				WPL
	Three Months		Six Months		Three Months		Six Months		Three Months		Six Months
	2021	2020	2021	2020	2021	2020	2021	2020	2021	2020	2021	2020
Compensation expense	$2	$2	$5	$5	$2	$2	$3	$3	$1	$1	$2	$2
Income tax benefits	1	1	2	2	1	1	1	1	1	1	1	1

Schedule Of Equity-based Compensation Plans Activity

For the six months ended June 30, 2021, performance shares, performance restricted stock units and restricted stock units were granted to key employees 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
	Grants	Grant Date Fair Value
Performance shares	72,774	$46.19
Performance restricted stock units	72,774	48.61
Restricted stock units	79,862	48.61

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 Plans				OPEB Plans
	Three Months		Six Months		Three Months		Six Months
Alliant Energy	2021	2020	2021	2020	2021	2020	2021	2020
Service cost	$3	$2	$6	$5	$1	$1	$2	$2
Interest cost	9	11	17	22	1	1	2	3
Expected return on plan assets	(17)	(17)	(34)	(35)	(1)	(1)	(2)	(3)
Amortization of actuarial loss	9	8	19	17	1	1	2	2
Settlement losses (a)	—	—	—	4	—	—	—	—
	$4	$4	$8	$13	$2	$2	$4	$4

	Defined Benefit Pension Plans				OPEB Plans
	Three Months		Six Months		Three Months		Six Months
IPL	2021	2020	2021	2020	2021	2020	2021	2020
Service cost	$2	$2	$4	$3	$1	$1	$1	$1
Interest cost	4	5	8	10	—	—	1	1
Expected return on plan assets	(8)	(8)	(16)	(16)	(1)	(1)	(2)	(2)
Amortization of actuarial loss	4	3	8	7	1	1	1	1
	$2	$2	$4	$4	$1	$1	$1	$1

	Defined Benefit Pension Plans				OPEB Plans
	Three Months		Six Months		Three Months		Six Months
WPL	2021	2020	2021	2020	2021	2020	2021	2020
Service cost	$1	$1	$2	$2	$—	$1	$—	$1
Interest cost	4	4	8	9	1	—	1	1
Expected return on plan assets	(7)	(7)	(15)	(15)	—	—	—	—
Amortization of actuarial loss	4	4	9	8	—	1	1	1
	$2	$2	$4	$4	$1	$2	$2	$3

(a)Settlement losses related to payments made to retired executives of Alliant Energy.

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 Energy				IPL				WPL
	Three Months		Six Months		Three Months		Six Months		Three Months		Six Months
	2021	2020	2021	2020	2021	2020	2021	2020	2021	2020	2021	2020
Compensation expense	$2	$2	$5	$5	$2	$2	$3	$3	$1	$1	$2	$2
Income tax benefits	1	1	2	2	1	1	1	1	1	1	1	1

Schedule Of Equity-based Compensation Plans Activity

For the six months ended June 30, 2021, performance shares, performance restricted stock units and restricted stock units were granted to key employees 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
	Grants	Grant Date Fair Value
Performance shares	72,774	$46.19
Performance restricted stock units	72,774	48.61
Restricted stock units	79,862	48.61

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 Plans				OPEB Plans
	Three Months		Six Months		Three Months		Six Months
Alliant Energy	2021	2020	2021	2020	2021	2020	2021	2020
Service cost	$3	$2	$6	$5	$1	$1	$2	$2
Interest cost	9	11	17	22	1	1	2	3
Expected return on plan assets	(17)	(17)	(34)	(35)	(1)	(1)	(2)	(3)
Amortization of actuarial loss	9	8	19	17	1	1	2	2
Settlement losses (a)	—	—	—	4	—	—	—	—
	$4	$4	$8	$13	$2	$2	$4	$4

	Defined Benefit Pension Plans				OPEB Plans
	Three Months		Six Months		Three Months		Six Months
IPL	2021	2020	2021	2020	2021	2020	2021	2020
Service cost	$2	$2	$4	$3	$1	$1	$1	$1
Interest cost	4	5	8	10	—	—	1	1
Expected return on plan assets	(8)	(8)	(16)	(16)	(1)	(1)	(2)	(2)
Amortization of actuarial loss	4	3	8	7	1	1	1	1
	$2	$2	$4	$4	$1	$1	$1	$1

	Defined Benefit Pension Plans				OPEB Plans
	Three Months		Six Months		Three Months		Six Months
WPL	2021	2020	2021	2020	2021	2020	2021	2020
Service cost	$1	$1	$2	$2	$—	$1	$—	$1
Interest cost	4	4	8	9	1	—	1	1
Expected return on plan assets	(7)	(7)	(15)	(15)	—	—	—	—
Amortization of actuarial loss	4	4	9	8	—	1	1	1
	$2	$2	$4	$4	$1	$2	$2	$3

(a)Settlement losses related to payments made to retired executives of Alliant Energy.

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 Energy				IPL				WPL
	Three Months		Six Months		Three Months		Six Months		Three Months		Six Months
	2021	2020	2021	2020	2021	2020	2021	2020	2021	2020	2021	2020
Compensation expense	$2	$2	$5	$5	$2	$2	$3	$3	$1	$1	$2	$2
Income tax benefits	1	1	2	2	1	1	1	1	1	1	1	1

Schedule Of Equity-based Compensation Plans Activity

For the six months ended June 30, 2021, performance shares, performance restricted stock units and restricted stock units were granted to key employees 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
	Grants	Grant Date Fair Value
Performance shares	72,774	$46.19
Performance restricted stock units	72,774	48.61
Restricted stock units	79,862	48.61