Regulatory Matters (Tables)

9 Months Ended

Sep. 30, 2016

Regulatory Assets [Line Items]

Regulatory Assets

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

	Alliant Energy				IPL				WPL
	September 30, 2016		December 31, 2015		September 30, 2016		December 31, 2015		September 30, 2016		December 31, 2015
Tax-related		$1,033.5		$987.7		$1,000.7		$958.2		$32.8		$29.5
Pension and OPEB costs	551.0		579.5		284.7		298.1		266.3		281.4
AROs	103.9		92.4		61.5		50.8		42.4		41.6
WPL’s EGUs retired early	43.1		45.0		—		—		43.1		45.0
Derivatives	39.0		70.6		10.6		28.2		28.4		42.4
Emission allowances	26.3		26.9		26.3		26.9		—		—
Commodity cost recovery	10.1		35.9		0.4		2.8		9.7		33.1
Other	67.9		70.6		33.0		37.6		34.9		33.0
		$1,874.8		$1,908.6		$1,417.2		$1,402.6		$457.6		$506.0

Regulatory Liabilities

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

	Alliant Energy				IPL				WPL
	September 30, 2016		December 31, 2015		September 30, 2016		December 31, 2015		September 30, 2016		December 31, 2015
Cost of removal obligations		$410.6		$406.0		$267.2		$260.4		$143.4		$145.6
IPL’s tax benefit riders	103.1		159.2		103.1		159.2		—		—
Electric transmission cost recovery	54.5		43.5		25.0		21.9		29.5		21.6
Commodity cost recovery	39.1		37.6		15.1		23.5		24.0		14.1
Energy efficiency cost recovery	28.0		48.3		—		—		28.0		48.3
Other	40.5		43.1		21.0		24.2		19.5		18.9
		$675.8		$737.7		$431.4		$489.2		$244.4		$248.5

Tax Benefit Riders

For the nine months ended September 30, 2016, Alliant Energy’s and IPL’s “IPL’s tax benefit riders” regulatory liabilities decreased by $56 million as follows (in millions):

Electric tax benefit rider credits		$47
Gas tax benefit rider credits	9
		$56

Customer Billing Credits

For the three and nine months ended September 30, IPL recorded billing credits to reduce retail electric customers’ bills as follows (in millions):

	Three Months			Nine Months
	2016	2015		2016		2015
Billing credits to reduce retail electric customers’ bills	$3		$7		$7		$19

IPL [Member]

Regulatory Assets [Line Items]

Regulatory Assets

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

	Alliant Energy				IPL				WPL
	September 30, 2016		December 31, 2015		September 30, 2016		December 31, 2015		September 30, 2016		December 31, 2015
Tax-related		$1,033.5		$987.7		$1,000.7		$958.2		$32.8		$29.5
Pension and OPEB costs	551.0		579.5		284.7		298.1		266.3		281.4
AROs	103.9		92.4		61.5		50.8		42.4		41.6
WPL’s EGUs retired early	43.1		45.0		—		—		43.1		45.0
Derivatives	39.0		70.6		10.6		28.2		28.4		42.4
Emission allowances	26.3		26.9		26.3		26.9		—		—
Commodity cost recovery	10.1		35.9		0.4		2.8		9.7		33.1
Other	67.9		70.6		33.0		37.6		34.9		33.0
		$1,874.8		$1,908.6		$1,417.2		$1,402.6		$457.6		$506.0

Regulatory Liabilities

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

	Alliant Energy				IPL				WPL
	September 30, 2016		December 31, 2015		September 30, 2016		December 31, 2015		September 30, 2016		December 31, 2015
Cost of removal obligations		$410.6		$406.0		$267.2		$260.4		$143.4		$145.6
IPL’s tax benefit riders	103.1		159.2		103.1		159.2		—		—
Electric transmission cost recovery	54.5		43.5		25.0		21.9		29.5		21.6
Commodity cost recovery	39.1		37.6		15.1		23.5		24.0		14.1
Energy efficiency cost recovery	28.0		48.3		—		—		28.0		48.3
Other	40.5		43.1		21.0		24.2		19.5		18.9
		$675.8		$737.7		$431.4		$489.2		$244.4		$248.5

Tax Benefit Riders

For the nine months ended September 30, 2016, Alliant Energy’s and IPL’s “IPL’s tax benefit riders” regulatory liabilities decreased by $56 million as follows (in millions):

Electric tax benefit rider credits		$47
Gas tax benefit rider credits	9
		$56

Customer Billing Credits

For the three and nine months ended September 30, IPL recorded billing credits to reduce retail electric customers’ bills as follows (in millions):

	Three Months			Nine Months
	2016	2015		2016		2015
Billing credits to reduce retail electric customers’ bills	$3		$7		$7		$19

WPL [Member]

Regulatory Assets [Line Items]

Regulatory Assets

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

	Alliant Energy				IPL				WPL
	September 30, 2016		December 31, 2015		September 30, 2016		December 31, 2015		September 30, 2016		December 31, 2015
Tax-related		$1,033.5		$987.7		$1,000.7		$958.2		$32.8		$29.5
Pension and OPEB costs	551.0		579.5		284.7		298.1		266.3		281.4
AROs	103.9		92.4		61.5		50.8		42.4		41.6
WPL’s EGUs retired early	43.1		45.0		—		—		43.1		45.0
Derivatives	39.0		70.6		10.6		28.2		28.4		42.4
Emission allowances	26.3		26.9		26.3		26.9		—		—
Commodity cost recovery	10.1		35.9		0.4		2.8		9.7		33.1
Other	67.9		70.6		33.0		37.6		34.9		33.0
		$1,874.8		$1,908.6		$1,417.2		$1,402.6		$457.6		$506.0

Regulatory Liabilities

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

	Alliant Energy				IPL				WPL
	September 30, 2016		December 31, 2015		September 30, 2016		December 31, 2015		September 30, 2016		December 31, 2015
Cost of removal obligations		$410.6		$406.0		$267.2		$260.4		$143.4		$145.6
IPL’s tax benefit riders	103.1		159.2		103.1		159.2		—		—
Electric transmission cost recovery	54.5		43.5		25.0		21.9		29.5		21.6
Commodity cost recovery	39.1		37.6		15.1		23.5		24.0		14.1
Energy efficiency cost recovery	28.0		48.3		—		—		28.0		48.3
Other	40.5		43.1		21.0		24.2		19.5		18.9
		$675.8		$737.7		$431.4		$489.2		$244.4		$248.5