Derivative Instruments (Tables)

12 Months Ended

Dec. 31, 2016

Derivative [Line Items]

Notional Amounts of Derivative Instruments

As of December 31, 2016, gross notional amounts and settlement/delivery years related to outstanding swap contracts, option contracts, physical forward contracts, FTRs, coal contracts and diesel fuel contracts 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	2,628	2017-2018	8,970	2017	139,865	2017-2023	4,239	2017-2019	6,552	2017-2018
IPL	—	—	5,465	2017	56,265	2017-2021	1,955	2017-2019	—	—
WPL	2,628	2017-2018	3,505	2017	83,600	2017-2023	2,284	2017-2018	6,552	2017-2018

Fair Value of Financial Instruments

At December 31, 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
Commodity contracts	2016		2015		2016		2015		2016		2015
Current derivative assets		$29.4		$15.1		$19.1		$13.8		$10.3		$1.3
Non-current derivative assets	12.0		3.3		1.7		1.7		10.3		1.6
Current derivative liabilities	13.3		47.3		2.7		18.5		10.6		28.8
Non-current derivative liabilities	15.3		17.3		5.6		4.9		9.7		12.4

IPL [Member]

Derivative [Line Items]

Notional Amounts of Derivative Instruments

As of December 31, 2016, gross notional amounts and settlement/delivery years related to outstanding swap contracts, option contracts, physical forward contracts, FTRs, coal contracts and diesel fuel contracts 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	2,628	2017-2018	8,970	2017	139,865	2017-2023	4,239	2017-2019	6,552	2017-2018
IPL	—	—	5,465	2017	56,265	2017-2021	1,955	2017-2019	—	—
WPL	2,628	2017-2018	3,505	2017	83,600	2017-2023	2,284	2017-2018	6,552	2017-2018

Fair Value of Financial Instruments

At December 31, 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
Commodity contracts	2016		2015		2016		2015		2016		2015
Current derivative assets		$29.4		$15.1		$19.1		$13.8		$10.3		$1.3
Non-current derivative assets	12.0		3.3		1.7		1.7		10.3		1.6
Current derivative liabilities	13.3		47.3		2.7		18.5		10.6		28.8
Non-current derivative liabilities	15.3		17.3		5.6		4.9		9.7		12.4

WPL [Member]

Derivative [Line Items]

Notional Amounts of Derivative Instruments

As of December 31, 2016, gross notional amounts and settlement/delivery years related to outstanding swap contracts, option contracts, physical forward contracts, FTRs, coal contracts and diesel fuel contracts 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	2,628	2017-2018	8,970	2017	139,865	2017-2023	4,239	2017-2019	6,552	2017-2018
IPL	—	—	5,465	2017	56,265	2017-2021	1,955	2017-2019	—	—
WPL	2,628	2017-2018	3,505	2017	83,600	2017-2023	2,284	2017-2018	6,552	2017-2018

Fair Value of Financial Instruments

At December 31, 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
Commodity contracts	2016		2015		2016		2015		2016		2015
Current derivative assets		$29.4		$15.1		$19.1		$13.8		$10.3		$1.3
Non-current derivative assets	12.0		3.3		1.7		1.7		10.3		1.6
Current derivative liabilities	13.3		47.3		2.7		18.5		10.6		28.8
Non-current derivative liabilities	15.3		17.3		5.6		4.9		9.7		12.4