Derivative Instruments (Tables)

3 Months Ended

Mar. 31, 2018

Derivative Instruments [Line Items]

Notional Amounts Of Derivative Instruments

As of March 31, 2018, gross notional amounts and settlement/delivery years related to outstanding swap contracts, option contracts, physical forward contracts and FTRs that were accounted for as commodity derivative instruments were as follows (units in thousands):

	Electricity		FTRs		Natural Gas		Coal		Diesel Fuel
	MWhs	Years	MWhs	Years	Dths	Years	Tons	Years	Gallons	Years
Alliant Energy	990	2018	3,370	2018	156,074	2018-2026	7,144	2018-2020	5,670	2018-2019
IPL	—	—	2,252	2018	65,541	2018-2026	2,975	2018-2020	—	—
WPL	990	2018	1,118	2018	90,533	2018-2026	4,169	2018-2020	5,670	2018-2019

Fair Value Of Financial Instruments

The fair values of current derivative assets are included in “Other current assets,” non-current derivative assets are included in “Deferred charges and other,” current derivative liabilities are included in “Other current liabilities” and non-current derivative liabilities are included in “Other liabilities” on the balance sheets as follows (in millions):

	Alliant Energy				IPL				WPL
	March 31, 2018		December 31, 2017		March 31, 2018		December 31, 2017		March 31, 2018		December 31, 2017
Current derivative assets		$10.8		$21.1		$7.0		$15.8		$3.8		$5.3
Non-current derivative assets	3.3		4.0		0.9		1.3		2.4		2.7
Current derivative liabilities	15.9		18.7		4.8		5.0		11.1		13.7
Non-current derivative liabilities	30.8		23.0		19.9		14.4		10.9		8.6

IPL [Member]

Derivative Instruments [Line Items]

Notional Amounts Of Derivative Instruments

As of March 31, 2018, gross notional amounts and settlement/delivery years related to outstanding swap contracts, option contracts, physical forward contracts and FTRs that were accounted for as commodity derivative instruments were as follows (units in thousands):

	Electricity		FTRs		Natural Gas		Coal		Diesel Fuel
	MWhs	Years	MWhs	Years	Dths	Years	Tons	Years	Gallons	Years
Alliant Energy	990	2018	3,370	2018	156,074	2018-2026	7,144	2018-2020	5,670	2018-2019
IPL	—	—	2,252	2018	65,541	2018-2026	2,975	2018-2020	—	—
WPL	990	2018	1,118	2018	90,533	2018-2026	4,169	2018-2020	5,670	2018-2019

Fair Value Of Financial Instruments

The fair values of current derivative assets are included in “Other current assets,” non-current derivative assets are included in “Deferred charges and other,” current derivative liabilities are included in “Other current liabilities” and non-current derivative liabilities are included in “Other liabilities” on the balance sheets as follows (in millions):

	Alliant Energy				IPL				WPL
	March 31, 2018		December 31, 2017		March 31, 2018		December 31, 2017		March 31, 2018		December 31, 2017
Current derivative assets		$10.8		$21.1		$7.0		$15.8		$3.8		$5.3
Non-current derivative assets	3.3		4.0		0.9		1.3		2.4		2.7
Current derivative liabilities	15.9		18.7		4.8		5.0		11.1		13.7
Non-current derivative liabilities	30.8		23.0		19.9		14.4		10.9		8.6

WPL [Member]

Derivative Instruments [Line Items]

Notional Amounts Of Derivative Instruments

As of March 31, 2018, gross notional amounts and settlement/delivery years related to outstanding swap contracts, option contracts, physical forward contracts and FTRs that were accounted for as commodity derivative instruments were as follows (units in thousands):

	Electricity		FTRs		Natural Gas		Coal		Diesel Fuel
	MWhs	Years	MWhs	Years	Dths	Years	Tons	Years	Gallons	Years
Alliant Energy	990	2018	3,370	2018	156,074	2018-2026	7,144	2018-2020	5,670	2018-2019
IPL	—	—	2,252	2018	65,541	2018-2026	2,975	2018-2020	—	—
WPL	990	2018	1,118	2018	90,533	2018-2026	4,169	2018-2020	5,670	2018-2019

Fair Value Of Financial Instruments

The fair values of current derivative assets are included in “Other current assets,” non-current derivative assets are included in “Deferred charges and other,” current derivative liabilities are included in “Other current liabilities” and non-current derivative liabilities are included in “Other liabilities” on the balance sheets as follows (in millions):

	Alliant Energy				IPL				WPL
	March 31, 2018		December 31, 2017		March 31, 2018		December 31, 2017		March 31, 2018		December 31, 2017
Current derivative assets		$10.8		$21.1		$7.0		$15.8		$3.8		$5.3
Non-current derivative assets	3.3		4.0		0.9		1.3		2.4		2.7
Current derivative liabilities	15.9		18.7		4.8		5.0		11.1		13.7
Non-current derivative liabilities	30.8		23.0		19.9		14.4		10.9		8.6