Asset Retirement Obligations (Tables)

12 Months Ended

Dec. 31, 2020

Schedule of Asset Retirement Obligations [Line Items]

Reconciliation Of Changes In Asset Retirement Obligations (AROs)

A reconciliation of the changes in AROs associated with long-lived assets is as follows (in millions):

	Alliant Energy		IPL		WPL
	2020	2019	2020	2019	2020	2019
Balance, January 1	$196	$177	$134	$118	$62	$59
Revisions in estimated cash flows	13	(6)	9	(7)	4	1
Liabilities settled	(13)	(8)	(9)	(8)	(4)	—
Liabilities incurred (a)	48	26	38	26	10	—
Accretion expense	7	7	5	5	2	2
Balance, December 31	$251	$196	$177	$134	$74	$62

(a)In 2020, IPL placed in service the Whispering Willow North, Golden Plains and Richland wind sites, and WPL placed in service the Kossuth wind site. As a result, Alliant Energy, IPL and WPL recognized additional AROs in 2020, which resulted in corresponding increases in property, plant and equipment, net on the respective balance sheets.

IPL [Member]

Schedule of Asset Retirement Obligations [Line Items]

Reconciliation Of Changes In Asset Retirement Obligations (AROs)

A reconciliation of the changes in AROs associated with long-lived assets is as follows (in millions):

	Alliant Energy		IPL		WPL
	2020	2019	2020	2019	2020	2019
Balance, January 1	$196	$177	$134	$118	$62	$59
Revisions in estimated cash flows	13	(6)	9	(7)	4	1
Liabilities settled	(13)	(8)	(9)	(8)	(4)	—
Liabilities incurred (a)	48	26	38	26	10	—
Accretion expense	7	7	5	5	2	2
Balance, December 31	$251	$196	$177	$134	$74	$62

(a)In 2020, IPL placed in service the Whispering Willow North, Golden Plains and Richland wind sites, and WPL placed in service the Kossuth wind site. As a result, Alliant Energy, IPL and WPL recognized additional AROs in 2020, which resulted in corresponding increases in property, plant and equipment, net on the respective balance sheets.

WPL [Member]

Schedule of Asset Retirement Obligations [Line Items]

Reconciliation Of Changes In Asset Retirement Obligations (AROs)

A reconciliation of the changes in AROs associated with long-lived assets is as follows (in millions):

	Alliant Energy		IPL		WPL
	2020	2019	2020	2019	2020	2019
Balance, January 1	$196	$177	$134	$118	$62	$59
Revisions in estimated cash flows	13	(6)	9	(7)	4	1
Liabilities settled	(13)	(8)	(9)	(8)	(4)	—
Liabilities incurred (a)	48	26	38	26	10	—
Accretion expense	7	7	5	5	2	2
Balance, December 31	$251	$196	$177	$134	$74	$62

(a)In 2020, IPL placed in service the Whispering Willow North, Golden Plains and Richland wind sites, and WPL placed in service the Kossuth wind site. As a result, Alliant Energy, IPL and WPL recognized additional AROs in 2020, which resulted in corresponding increases in property, plant and equipment, net on the respective balance sheets.