Regulatory Matters (Tables)

9 Months Ended

Sep. 30, 2019

Regulatory Assets [Line Items]

Regulatory Assets

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

	Alliant Energy				IPL				WPL
	September 30, 2019		December 31, 2018		September 30, 2019		December 31, 2018		September 30, 2019		December 31, 2018
Tax-related		$825.2		$820.6		$787.2		$783.1		$38.0		$37.5
Pension and OPEB costs	513.1		542.3		260.0		274.0		253.1		268.3
Assets retired early	138.7		111.6		90.1		55.4		48.6		56.2
Asset retirement obligations	110.7		110.8		75.2		76.3		35.5		34.5
IPL’s DAEC PPA amendment	107.7		—		107.7		—		—		—
Derivatives	34.0		28.0		15.0		15.1		19.0		12.9
Emission allowances	21.7		23.6		21.7		23.6		—		—
Other	88.9		100.4		47.1		51.5		41.8		48.9
		$1,840.0		$1,737.3		$1,404.0		$1,279.0		$436.0		$458.3

Regulatory Liabilities

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

	Alliant Energy				IPL				WPL
	September 30, 2019		December 31, 2018		September 30, 2019		December 31, 2018		September 30, 2019		December 31, 2018
Tax-related		$851.4		$890.6		$365.0		$390.1		$486.4		$500.5
Cost of removal obligations	390.9		401.2		261.0		273.3		129.9		127.9
Electric transmission cost recovery	89.8		104.0		48.0		47.7		41.8		56.3
Commodity cost recovery	29.1		16.8		16.7		11.9		12.4		4.9
WPL’s earnings sharing mechanism	21.8		25.4		—		—		21.8		25.4
Derivatives	20.8		18.5		16.9		10.2		3.9		8.3
Other	47.2		36.7		26.0		21.7		21.2		15.0
		$1,451.0		$1,493.2		$733.6		$754.9		$717.4		$738.3

IPL [Member]

Regulatory Assets [Line Items]

Regulatory Assets

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

	Alliant Energy				IPL				WPL
	September 30, 2019		December 31, 2018		September 30, 2019		December 31, 2018		September 30, 2019		December 31, 2018
Tax-related		$825.2		$820.6		$787.2		$783.1		$38.0		$37.5
Pension and OPEB costs	513.1		542.3		260.0		274.0		253.1		268.3
Assets retired early	138.7		111.6		90.1		55.4		48.6		56.2
Asset retirement obligations	110.7		110.8		75.2		76.3		35.5		34.5
IPL’s DAEC PPA amendment	107.7		—		107.7		—		—		—
Derivatives	34.0		28.0		15.0		15.1		19.0		12.9
Emission allowances	21.7		23.6		21.7		23.6		—		—
Other	88.9		100.4		47.1		51.5		41.8		48.9
		$1,840.0		$1,737.3		$1,404.0		$1,279.0		$436.0		$458.3

Regulatory Liabilities

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

	Alliant Energy				IPL				WPL
	September 30, 2019		December 31, 2018		September 30, 2019		December 31, 2018		September 30, 2019		December 31, 2018
Tax-related		$851.4		$890.6		$365.0		$390.1		$486.4		$500.5
Cost of removal obligations	390.9		401.2		261.0		273.3		129.9		127.9
Electric transmission cost recovery	89.8		104.0		48.0		47.7		41.8		56.3
Commodity cost recovery	29.1		16.8		16.7		11.9		12.4		4.9
WPL’s earnings sharing mechanism	21.8		25.4		—		—		21.8		25.4
Derivatives	20.8		18.5		16.9		10.2		3.9		8.3
Other	47.2		36.7		26.0		21.7		21.2		15.0
		$1,451.0		$1,493.2		$733.6		$754.9		$717.4		$738.3

WPL [Member]

Regulatory Assets [Line Items]

Regulatory Assets

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

	Alliant Energy				IPL				WPL
	September 30, 2019		December 31, 2018		September 30, 2019		December 31, 2018		September 30, 2019		December 31, 2018
Tax-related		$825.2		$820.6		$787.2		$783.1		$38.0		$37.5
Pension and OPEB costs	513.1		542.3		260.0		274.0		253.1		268.3
Assets retired early	138.7		111.6		90.1		55.4		48.6		56.2
Asset retirement obligations	110.7		110.8		75.2		76.3		35.5		34.5
IPL’s DAEC PPA amendment	107.7		—		107.7		—		—		—
Derivatives	34.0		28.0		15.0		15.1		19.0		12.9
Emission allowances	21.7		23.6		21.7		23.6		—		—
Other	88.9		100.4		47.1		51.5		41.8		48.9
		$1,840.0		$1,737.3		$1,404.0		$1,279.0		$436.0		$458.3

Regulatory Liabilities

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

	Alliant Energy				IPL				WPL
	September 30, 2019		December 31, 2018		September 30, 2019		December 31, 2018		September 30, 2019		December 31, 2018
Tax-related		$851.4		$890.6		$365.0		$390.1		$486.4		$500.5
Cost of removal obligations	390.9		401.2		261.0		273.3		129.9		127.9
Electric transmission cost recovery	89.8		104.0		48.0		47.7		41.8		56.3
Commodity cost recovery	29.1		16.8		16.7		11.9		12.4		4.9
WPL’s earnings sharing mechanism	21.8		25.4		—		—		21.8		25.4
Derivatives	20.8		18.5		16.9		10.2		3.9		8.3
Other	47.2		36.7		26.0		21.7		21.2		15.0
		$1,451.0		$1,493.2		$733.6		$754.9		$717.4		$738.3