Derivative Instruments (Tables)

6 Months Ended

Jun. 30, 2018

Derivative Instruments [Line Items]

Notional Amounts Of Derivative Instruments

As of June 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	662	2018	22,949	2018-2019	168,608	2018-2026	8,230	2018-2020	4,788	2018-2019
IPL	—	—	12,403	2018-2019	76,982	2018-2026	3,654	2018-2020	—	—
WPL	662	2018	10,546	2018-2019	91,626	2018-2026	4,576	2018-2020	4,788	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
	June 30, 2018		December 31, 2017		June 30, 2018		December 31, 2017		June 30, 2018		December 31, 2017
Current derivative assets		$28.0		$21.1		$17.8		$15.8		$10.2		$5.3
Non-current derivative assets	3.6		4.0		1.2		1.3		2.4		2.7
Current derivative liabilities	11.1		18.7		3.5		5.0		7.6		13.7
Non-current derivative liabilities	31.6		23.0		19.5		14.4		12.1		8.6

IPL [Member]

Derivative Instruments [Line Items]

Notional Amounts Of Derivative Instruments

As of June 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	662	2018	22,949	2018-2019	168,608	2018-2026	8,230	2018-2020	4,788	2018-2019
IPL	—	—	12,403	2018-2019	76,982	2018-2026	3,654	2018-2020	—	—
WPL	662	2018	10,546	2018-2019	91,626	2018-2026	4,576	2018-2020	4,788	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
	June 30, 2018		December 31, 2017		June 30, 2018		December 31, 2017		June 30, 2018		December 31, 2017
Current derivative assets		$28.0		$21.1		$17.8		$15.8		$10.2		$5.3
Non-current derivative assets	3.6		4.0		1.2		1.3		2.4		2.7
Current derivative liabilities	11.1		18.7		3.5		5.0		7.6		13.7
Non-current derivative liabilities	31.6		23.0		19.5		14.4		12.1		8.6

WPL [Member]

Derivative Instruments [Line Items]

Notional Amounts Of Derivative Instruments

As of June 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	662	2018	22,949	2018-2019	168,608	2018-2026	8,230	2018-2020	4,788	2018-2019
IPL	—	—	12,403	2018-2019	76,982	2018-2026	3,654	2018-2020	—	—
WPL	662	2018	10,546	2018-2019	91,626	2018-2026	4,576	2018-2020	4,788	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
	June 30, 2018		December 31, 2017		June 30, 2018		December 31, 2017		June 30, 2018		December 31, 2017
Current derivative assets		$28.0		$21.1		$17.8		$15.8		$10.2		$5.3
Non-current derivative assets	3.6		4.0		1.2		1.3		2.4		2.7
Current derivative liabilities	11.1		18.7		3.5		5.0		7.6		13.7
Non-current derivative liabilities	31.6		23.0		19.5		14.4		12.1		8.6