Regulatory Matters (Tables)

3 Months Ended

Mar. 31, 2020

Regulatory Assets [Line Items]

Regulatory Assets

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

	Alliant Energy				IPL				WPL
	March 31, 2020		December 31, 2019		March 31, 2020		December 31, 2019		March 31, 2020		December 31, 2019
Tax-related		$831.2		$817.6		$788.3		$776.8		$42.9		$40.8
Pension and OPEB costs	510.5		524.0		255.7		262.5		254.8		261.5
Assets retired early	129.2		134.0		85.6		87.9		43.6		46.1
Asset retirement obligations	112.8		111.8		77.1		76.2		35.7		35.6
IPL’s DAEC PPA amendment	108.8		108.2		108.8		108.2		—		—
Derivatives	51.6		39.5		22.6		18.3		29.0		21.2
Emission allowances	20.5		21.1		20.5		21.1		—		—
Other	90.3		88.5		46.3		48.3		44.0		40.2
		$1,854.9		$1,844.7		$1,404.9		$1,399.3		$450.0		$445.4

Regulatory Liabilities

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

	Alliant Energy				IPL				WPL
	March 31, 2020		December 31, 2019		March 31, 2020		December 31, 2019		March 31, 2020		December 31, 2019
Tax-related		$799.4		$835.6		$345.0		$350.9		$454.4		$484.7
Cost of removal obligations	387.9		387.7		258.1		257.0		129.8		130.7
Electric transmission cost recovery	97.4		88.6		62.0		51.3		35.4		37.3
Commodity cost recovery	25.8		24.2		10.7		8.8		15.1		15.4
WPL’s earnings sharing mechanism	20.4		21.9		—		—		20.4		21.9
Derivatives	16.4		19.9		14.8		17.4		1.6		2.5
Other	46.6		45.7		30.2		29.3		16.4		16.4
		$1,393.9		$1,423.6		$720.8		$714.7		$673.1		$708.9

IPL [Member]

Regulatory Assets [Line Items]

Regulatory Assets

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

	Alliant Energy				IPL				WPL
	March 31, 2020		December 31, 2019		March 31, 2020		December 31, 2019		March 31, 2020		December 31, 2019
Tax-related		$831.2		$817.6		$788.3		$776.8		$42.9		$40.8
Pension and OPEB costs	510.5		524.0		255.7		262.5		254.8		261.5
Assets retired early	129.2		134.0		85.6		87.9		43.6		46.1
Asset retirement obligations	112.8		111.8		77.1		76.2		35.7		35.6
IPL’s DAEC PPA amendment	108.8		108.2		108.8		108.2		—		—
Derivatives	51.6		39.5		22.6		18.3		29.0		21.2
Emission allowances	20.5		21.1		20.5		21.1		—		—
Other	90.3		88.5		46.3		48.3		44.0		40.2
		$1,854.9		$1,844.7		$1,404.9		$1,399.3		$450.0		$445.4

Regulatory Liabilities

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

	Alliant Energy				IPL				WPL
	March 31, 2020		December 31, 2019		March 31, 2020		December 31, 2019		March 31, 2020		December 31, 2019
Tax-related		$799.4		$835.6		$345.0		$350.9		$454.4		$484.7
Cost of removal obligations	387.9		387.7		258.1		257.0		129.8		130.7
Electric transmission cost recovery	97.4		88.6		62.0		51.3		35.4		37.3
Commodity cost recovery	25.8		24.2		10.7		8.8		15.1		15.4
WPL’s earnings sharing mechanism	20.4		21.9		—		—		20.4		21.9
Derivatives	16.4		19.9		14.8		17.4		1.6		2.5
Other	46.6		45.7		30.2		29.3		16.4		16.4
		$1,393.9		$1,423.6		$720.8		$714.7		$673.1		$708.9

WPL [Member]

Regulatory Assets [Line Items]

Regulatory Assets

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

	Alliant Energy				IPL				WPL
	March 31, 2020		December 31, 2019		March 31, 2020		December 31, 2019		March 31, 2020		December 31, 2019
Tax-related		$831.2		$817.6		$788.3		$776.8		$42.9		$40.8
Pension and OPEB costs	510.5		524.0		255.7		262.5		254.8		261.5
Assets retired early	129.2		134.0		85.6		87.9		43.6		46.1
Asset retirement obligations	112.8		111.8		77.1		76.2		35.7		35.6
IPL’s DAEC PPA amendment	108.8		108.2		108.8		108.2		—		—
Derivatives	51.6		39.5		22.6		18.3		29.0		21.2
Emission allowances	20.5		21.1		20.5		21.1		—		—
Other	90.3		88.5		46.3		48.3		44.0		40.2
		$1,854.9		$1,844.7		$1,404.9		$1,399.3		$450.0		$445.4

Regulatory Liabilities

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

	Alliant Energy				IPL				WPL
	March 31, 2020		December 31, 2019		March 31, 2020		December 31, 2019		March 31, 2020		December 31, 2019
Tax-related		$799.4		$835.6		$345.0		$350.9		$454.4		$484.7
Cost of removal obligations	387.9		387.7		258.1		257.0		129.8		130.7
Electric transmission cost recovery	97.4		88.6		62.0		51.3		35.4		37.3
Commodity cost recovery	25.8		24.2		10.7		8.8		15.1		15.4
WPL’s earnings sharing mechanism	20.4		21.9		—		—		20.4		21.9
Derivatives	16.4		19.9		14.8		17.4		1.6		2.5
Other	46.6		45.7		30.2		29.3		16.4		16.4
		$1,393.9		$1,423.6		$720.8		$714.7		$673.1		$708.9