Regulatory Matters (Tables)

6 Months Ended

Jun. 30, 2020

Regulatory Assets [Line Items]

Regulatory Assets

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

	Alliant Energy				IPL				WPL
	June 30, 2020		December 31, 2019		June 30, 2020		December 31, 2019		June 30, 2020		December 31, 2019
Tax-related		$842.5		$817.6		$797.4		$776.8		$45.1		$40.8
Pension and OPEB costs	501.2		524.0		251.3		262.5		249.9		261.5
Assets retired early	122.9		134.0		81.8		87.9		41.1		46.1
Asset retirement obligations	114.0		111.8		78.2		76.2		35.8		35.6
IPL’s DAEC PPA amendment	109.4		108.2		109.4		108.2		—		—
Derivatives	47.0		39.5		20.5		18.3		26.5		21.2
Emission allowances	19.8		21.1		19.8		21.1		—		—
Other	86.2		88.5		46.5		48.3		39.7		40.2
		$1,843.0		$1,844.7		$1,404.9		$1,399.3		$438.1		$445.4

Regulatory Liabilities

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

	Alliant Energy				IPL				WPL
	June 30, 2020		December 31, 2019		June 30, 2020		December 31, 2019		June 30, 2020		December 31, 2019
Tax-related		$779.0		$835.6		$343.6		$350.9		$435.4		$484.7
Cost of removal obligations	385.8		387.7		256.4		257.0		129.4		130.7
Electric transmission cost recovery	66.3		88.6		30.7		51.3		35.6		37.3
Commodity cost recovery	30.1		24.2		14.0		8.8		16.1		15.4
Derivatives	28.8		19.9		26.3		17.4		2.5		2.5
WPL’s earnings sharing mechanism	20.4		21.9		—		—		20.4		21.9
Other	60.6		45.7		46.9		29.3		13.7		16.4
		$1,371.0		$1,423.6		$717.9		$714.7		$653.1		$708.9

IPL [Member]

Regulatory Assets [Line Items]

Regulatory Assets

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

	Alliant Energy				IPL				WPL
	June 30, 2020		December 31, 2019		June 30, 2020		December 31, 2019		June 30, 2020		December 31, 2019
Tax-related		$842.5		$817.6		$797.4		$776.8		$45.1		$40.8
Pension and OPEB costs	501.2		524.0		251.3		262.5		249.9		261.5
Assets retired early	122.9		134.0		81.8		87.9		41.1		46.1
Asset retirement obligations	114.0		111.8		78.2		76.2		35.8		35.6
IPL’s DAEC PPA amendment	109.4		108.2		109.4		108.2		—		—
Derivatives	47.0		39.5		20.5		18.3		26.5		21.2
Emission allowances	19.8		21.1		19.8		21.1		—		—
Other	86.2		88.5		46.5		48.3		39.7		40.2
		$1,843.0		$1,844.7		$1,404.9		$1,399.3		$438.1		$445.4

Regulatory Liabilities

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

	Alliant Energy				IPL				WPL
	June 30, 2020		December 31, 2019		June 30, 2020		December 31, 2019		June 30, 2020		December 31, 2019
Tax-related		$779.0		$835.6		$343.6		$350.9		$435.4		$484.7
Cost of removal obligations	385.8		387.7		256.4		257.0		129.4		130.7
Electric transmission cost recovery	66.3		88.6		30.7		51.3		35.6		37.3
Commodity cost recovery	30.1		24.2		14.0		8.8		16.1		15.4
Derivatives	28.8		19.9		26.3		17.4		2.5		2.5
WPL’s earnings sharing mechanism	20.4		21.9		—		—		20.4		21.9
Other	60.6		45.7		46.9		29.3		13.7		16.4
		$1,371.0		$1,423.6		$717.9		$714.7		$653.1		$708.9

WPL [Member]

Regulatory Assets [Line Items]

Regulatory Assets

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

	Alliant Energy				IPL				WPL
	June 30, 2020		December 31, 2019		June 30, 2020		December 31, 2019		June 30, 2020		December 31, 2019
Tax-related		$842.5		$817.6		$797.4		$776.8		$45.1		$40.8
Pension and OPEB costs	501.2		524.0		251.3		262.5		249.9		261.5
Assets retired early	122.9		134.0		81.8		87.9		41.1		46.1
Asset retirement obligations	114.0		111.8		78.2		76.2		35.8		35.6
IPL’s DAEC PPA amendment	109.4		108.2		109.4		108.2		—		—
Derivatives	47.0		39.5		20.5		18.3		26.5		21.2
Emission allowances	19.8		21.1		19.8		21.1		—		—
Other	86.2		88.5		46.5		48.3		39.7		40.2
		$1,843.0		$1,844.7		$1,404.9		$1,399.3		$438.1		$445.4

Regulatory Liabilities

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

	Alliant Energy				IPL				WPL
	June 30, 2020		December 31, 2019		June 30, 2020		December 31, 2019		June 30, 2020		December 31, 2019
Tax-related		$779.0		$835.6		$343.6		$350.9		$435.4		$484.7
Cost of removal obligations	385.8		387.7		256.4		257.0		129.4		130.7
Electric transmission cost recovery	66.3		88.6		30.7		51.3		35.6		37.3
Commodity cost recovery	30.1		24.2		14.0		8.8		16.1		15.4
Derivatives	28.8		19.9		26.3		17.4		2.5		2.5
WPL’s earnings sharing mechanism	20.4		21.9		—		—		20.4		21.9
Other	60.6		45.7		46.9		29.3		13.7		16.4
		$1,371.0		$1,423.6		$717.9		$714.7		$653.1		$708.9