Derivative Instruments (Tables)

9 Months Ended

Sep. 30, 2018

Derivative Instruments [Line Items]

Notional Amounts Of Derivative Instruments

As of September 30, 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	331	2018	16,553	2018-2019	179,275	2018-2026	11,922	2018-2021	3,906	2018-2019
IPL	—	—	9,220	2018-2019	83,485	2018-2026	4,849	2018-2021	—	—
WPL	331	2018	7,333	2018-2019	95,790	2018-2026	7,073	2018-2021	3,906	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
	September 30, 2018		December 31, 2017		September 30, 2018		December 31, 2017		September 30, 2018		December 31, 2017
Current derivative assets		$39.7		$21.1		$26.2		$15.8		$13.5		$5.3
Non-current derivative assets	8.3		4.0		2.9		1.3		5.4		2.7
Current derivative liabilities	7.2		18.7		3.2		5.0		4.0		13.7
Non-current derivative liabilities	14.8		23.0		6.5		14.4		8.3		8.6

IPL [Member]

Derivative Instruments [Line Items]

Notional Amounts Of Derivative Instruments

As of September 30, 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	331	2018	16,553	2018-2019	179,275	2018-2026	11,922	2018-2021	3,906	2018-2019
IPL	—	—	9,220	2018-2019	83,485	2018-2026	4,849	2018-2021	—	—
WPL	331	2018	7,333	2018-2019	95,790	2018-2026	7,073	2018-2021	3,906	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
	September 30, 2018		December 31, 2017		September 30, 2018		December 31, 2017		September 30, 2018		December 31, 2017
Current derivative assets		$39.7		$21.1		$26.2		$15.8		$13.5		$5.3
Non-current derivative assets	8.3		4.0		2.9		1.3		5.4		2.7
Current derivative liabilities	7.2		18.7		3.2		5.0		4.0		13.7
Non-current derivative liabilities	14.8		23.0		6.5		14.4		8.3		8.6

WPL [Member]

Derivative Instruments [Line Items]

Notional Amounts Of Derivative Instruments

As of September 30, 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	331	2018	16,553	2018-2019	179,275	2018-2026	11,922	2018-2021	3,906	2018-2019
IPL	—	—	9,220	2018-2019	83,485	2018-2026	4,849	2018-2021	—	—
WPL	331	2018	7,333	2018-2019	95,790	2018-2026	7,073	2018-2021	3,906	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
	September 30, 2018		December 31, 2017		September 30, 2018		December 31, 2017		September 30, 2018		December 31, 2017
Current derivative assets		$39.7		$21.1		$26.2		$15.8		$13.5		$5.3
Non-current derivative assets	8.3		4.0		2.9		1.3		5.4		2.7
Current derivative liabilities	7.2		18.7		3.2		5.0		4.0		13.7
Non-current derivative liabilities	14.8		23.0		6.5		14.4		8.3		8.6