Regulatory Matters (Tables)

9 Months Ended

Sep. 30, 2020

Regulatory Assets [Line Items]

Regulatory Assets

Regulatory assets were comprised of the following items (in millions):

	Alliant Energy				IPL				WPL
	September 30, 2020		December 31, 2019		September 30, 2020		December 31, 2019		September 30, 2020		December 31, 2019
Tax-related		$877		$818		$829		$777		$48		$41
Pension and OPEB costs	492		524		247		263		245		261
Assets retired early	118		134		79		88		39		46
Asset retirement obligations	115		112		79		76		36		36
IPL’s DAEC PPA amendment	110		108		110		108		—		—
Derivatives	20		39		8		18		12		21
Emission allowances	19		21		19		21		—		—
Other	85		89		47		49		38		40
		$1,836		$1,845		$1,418		$1,400		$418		$445

Regulatory Liabilities

Regulatory liabilities were comprised of the following items (in millions):

	Alliant Energy				IPL				WPL
	September 30, 2020		December 31, 2019		September 30, 2020		December 31, 2019		September 30, 2020		December 31, 2019
Tax-related		$746		$836		$334		$351		$412		$485
Cost of removal obligations	371		388		241		257		130		131
Electric transmission cost recovery	62		88		30		51		32		37
Derivatives	40		20		27		17		13		3
WPL’s West Riverside liquidated damages	36		—		—		—		36		—
Commodity cost recovery	22		24		19		9		3		15
WPL’s earnings sharing mechanism	22		22		—		—		22		22
Other	52		46		40		30		12		16
		$1,351		$1,424		$691		$715		$660		$709

IPL [Member]

Regulatory Assets [Line Items]

Regulatory Assets

Regulatory assets were comprised of the following items (in millions):

	Alliant Energy				IPL				WPL
	September 30, 2020		December 31, 2019		September 30, 2020		December 31, 2019		September 30, 2020		December 31, 2019
Tax-related		$877		$818		$829		$777		$48		$41
Pension and OPEB costs	492		524		247		263		245		261
Assets retired early	118		134		79		88		39		46
Asset retirement obligations	115		112		79		76		36		36
IPL’s DAEC PPA amendment	110		108		110		108		—		—
Derivatives	20		39		8		18		12		21
Emission allowances	19		21		19		21		—		—
Other	85		89		47		49		38		40
		$1,836		$1,845		$1,418		$1,400		$418		$445

Regulatory Liabilities

Regulatory liabilities were comprised of the following items (in millions):

	Alliant Energy				IPL				WPL
	September 30, 2020		December 31, 2019		September 30, 2020		December 31, 2019		September 30, 2020		December 31, 2019
Tax-related		$746		$836		$334		$351		$412		$485
Cost of removal obligations	371		388		241		257		130		131
Electric transmission cost recovery	62		88		30		51		32		37
Derivatives	40		20		27		17		13		3
WPL’s West Riverside liquidated damages	36		—		—		—		36		—
Commodity cost recovery	22		24		19		9		3		15
WPL’s earnings sharing mechanism	22		22		—		—		22		22
Other	52		46		40		30		12		16
		$1,351		$1,424		$691		$715		$660		$709

WPL [Member]

Regulatory Assets [Line Items]

Regulatory Assets

Regulatory assets were comprised of the following items (in millions):

	Alliant Energy				IPL				WPL
	September 30, 2020		December 31, 2019		September 30, 2020		December 31, 2019		September 30, 2020		December 31, 2019
Tax-related		$877		$818		$829		$777		$48		$41
Pension and OPEB costs	492		524		247		263		245		261
Assets retired early	118		134		79		88		39		46
Asset retirement obligations	115		112		79		76		36		36
IPL’s DAEC PPA amendment	110		108		110		108		—		—
Derivatives	20		39		8		18		12		21
Emission allowances	19		21		19		21		—		—
Other	85		89		47		49		38		40
		$1,836		$1,845		$1,418		$1,400		$418		$445

Regulatory Liabilities

Regulatory liabilities were comprised of the following items (in millions):

	Alliant Energy				IPL				WPL
	September 30, 2020		December 31, 2019		September 30, 2020		December 31, 2019		September 30, 2020		December 31, 2019
Tax-related		$746		$836		$334		$351		$412		$485
Cost of removal obligations	371		388		241		257		130		131
Electric transmission cost recovery	62		88		30		51		32		37
Derivatives	40		20		27		17		13		3
WPL’s West Riverside liquidated damages	36		—		—		—		36		—
Commodity cost recovery	22		24		19		9		3		15
WPL’s earnings sharing mechanism	22		22		—		—		22		22
Other	52		46		40		30		12		16
		$1,351		$1,424		$691		$715		$660		$709