Regulatory Matters (Tables)

6 Months Ended

Jun. 30, 2019

Regulatory Assets [Line Items]

Regulatory Assets

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

	Alliant Energy				IPL				WPL
	June 30, 2019		December 31, 2018		June 30, 2019		December 31, 2018		June 30, 2019		December 31, 2018
Tax-related		$815.5		$820.6		$780.2		$783.1		$35.3		$37.5
Pension and OPEB costs	522.9		542.3		264.7		274.0		258.2		268.3
Asset retirement obligations	111.0		110.8		76.2		76.3		34.8		34.5
IPL’s DAEC PPA amendment	107.1		—		107.1		—		—		—
EGUs retired early	102.8		111.6		51.7		55.4		51.1		56.2
Derivatives	30.6		28.0		13.4		15.1		17.2		12.9
Emission allowances	22.4		23.6		22.4		23.6		—		—
Other	94.6		100.4		48.8		51.5		45.8		48.9
		$1,806.9		$1,737.3		$1,364.5		$1,279.0		$442.4		$458.3

Regulatory Liabilities

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

	Alliant Energy				IPL				WPL
	June 30, 2019		December 31, 2018		June 30, 2019		December 31, 2018		June 30, 2019		December 31, 2018
Tax-related		$853.8		$890.6		$365.6		$390.1		$488.2		$500.5
Cost of removal obligations	399.2		401.2		269.5		273.3		129.7		127.9
Electric transmission cost recovery	101.5		104.0		52.7		47.7		48.8		56.3
WPL’s earnings sharing mechanism	25.2		25.4		—		—		25.2		25.4
Commodity cost recovery	22.7		16.8		11.9		11.9		10.8		4.9
Other	40.5		55.2		20.2		31.9		20.3		23.3
		$1,442.9		$1,493.2		$719.9		$754.9		$723.0		$738.3

IPL [Member]

Regulatory Assets [Line Items]

Regulatory Assets

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

	Alliant Energy				IPL				WPL
	June 30, 2019		December 31, 2018		June 30, 2019		December 31, 2018		June 30, 2019		December 31, 2018
Tax-related		$815.5		$820.6		$780.2		$783.1		$35.3		$37.5
Pension and OPEB costs	522.9		542.3		264.7		274.0		258.2		268.3
Asset retirement obligations	111.0		110.8		76.2		76.3		34.8		34.5
IPL’s DAEC PPA amendment	107.1		—		107.1		—		—		—
EGUs retired early	102.8		111.6		51.7		55.4		51.1		56.2
Derivatives	30.6		28.0		13.4		15.1		17.2		12.9
Emission allowances	22.4		23.6		22.4		23.6		—		—
Other	94.6		100.4		48.8		51.5		45.8		48.9
		$1,806.9		$1,737.3		$1,364.5		$1,279.0		$442.4		$458.3

Regulatory Liabilities

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

	Alliant Energy				IPL				WPL
	June 30, 2019		December 31, 2018		June 30, 2019		December 31, 2018		June 30, 2019		December 31, 2018
Tax-related		$853.8		$890.6		$365.6		$390.1		$488.2		$500.5
Cost of removal obligations	399.2		401.2		269.5		273.3		129.7		127.9
Electric transmission cost recovery	101.5		104.0		52.7		47.7		48.8		56.3
WPL’s earnings sharing mechanism	25.2		25.4		—		—		25.2		25.4
Commodity cost recovery	22.7		16.8		11.9		11.9		10.8		4.9
Other	40.5		55.2		20.2		31.9		20.3		23.3
		$1,442.9		$1,493.2		$719.9		$754.9		$723.0		$738.3

WPL [Member]

Regulatory Assets [Line Items]

Regulatory Assets

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

	Alliant Energy				IPL				WPL
	June 30, 2019		December 31, 2018		June 30, 2019		December 31, 2018		June 30, 2019		December 31, 2018
Tax-related		$815.5		$820.6		$780.2		$783.1		$35.3		$37.5
Pension and OPEB costs	522.9		542.3		264.7		274.0		258.2		268.3
Asset retirement obligations	111.0		110.8		76.2		76.3		34.8		34.5
IPL’s DAEC PPA amendment	107.1		—		107.1		—		—		—
EGUs retired early	102.8		111.6		51.7		55.4		51.1		56.2
Derivatives	30.6		28.0		13.4		15.1		17.2		12.9
Emission allowances	22.4		23.6		22.4		23.6		—		—
Other	94.6		100.4		48.8		51.5		45.8		48.9
		$1,806.9		$1,737.3		$1,364.5		$1,279.0		$442.4		$458.3

Regulatory Liabilities

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

	Alliant Energy				IPL				WPL
	June 30, 2019		December 31, 2018		June 30, 2019		December 31, 2018		June 30, 2019		December 31, 2018
Tax-related		$853.8		$890.6		$365.6		$390.1		$488.2		$500.5
Cost of removal obligations	399.2		401.2		269.5		273.3		129.7		127.9
Electric transmission cost recovery	101.5		104.0		52.7		47.7		48.8		56.3
WPL’s earnings sharing mechanism	25.2		25.4		—		—		25.2		25.4
Commodity cost recovery	22.7		16.8		11.9		11.9		10.8		4.9
Other	40.5		55.2		20.2		31.9		20.3		23.3
		$1,442.9		$1,493.2		$719.9		$754.9		$723.0		$738.3