Derivative Instruments (Tables)

12 Months Ended

Dec. 31, 2018

Derivative [Line Items]

Notional Amounts of Derivative Instruments

As of December 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):

	FTRs		Natural Gas		Coal		Diesel Fuel
	MWhs	Years	Dths	Years	Tons	Years	Gallons	Years
Alliant Energy	10,399	2019	181,694	2019-2026	10,467	2019-2021	3,024	2019
IPL	5,954	2019	80,150	2019-2026	4,410	2019-2021	—
WPL	4,445	2019	101,544	2019-2026	6,057	2019-2021	3,024	2019

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
	2018		2017		2018		2017		2018		2017
Current derivative assets		$24.6		$21.1		$16.1		$15.8		$8.5		$5.3
Non-current derivative assets	3.7		4.0		1.6		1.3		2.1		2.7
Current derivative liabilities	5.6		18.7		3.1		5.0		2.5		13.7
Non-current derivative liabilities	17.7		23.0		8.1		14.4		9.6		8.6

IPL [Member]

Derivative [Line Items]

Notional Amounts of Derivative Instruments

As of December 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):

	FTRs		Natural Gas		Coal		Diesel Fuel
	MWhs	Years	Dths	Years	Tons	Years	Gallons	Years
Alliant Energy	10,399	2019	181,694	2019-2026	10,467	2019-2021	3,024	2019
IPL	5,954	2019	80,150	2019-2026	4,410	2019-2021	—
WPL	4,445	2019	101,544	2019-2026	6,057	2019-2021	3,024	2019

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
	2018		2017		2018		2017		2018		2017
Current derivative assets		$24.6		$21.1		$16.1		$15.8		$8.5		$5.3
Non-current derivative assets	3.7		4.0		1.6		1.3		2.1		2.7
Current derivative liabilities	5.6		18.7		3.1		5.0		2.5		13.7
Non-current derivative liabilities	17.7		23.0		8.1		14.4		9.6		8.6

WPL [Member]

Derivative [Line Items]

Notional Amounts of Derivative Instruments

As of December 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):

	FTRs		Natural Gas		Coal		Diesel Fuel
	MWhs	Years	Dths	Years	Tons	Years	Gallons	Years
Alliant Energy	10,399	2019	181,694	2019-2026	10,467	2019-2021	3,024	2019
IPL	5,954	2019	80,150	2019-2026	4,410	2019-2021	—
WPL	4,445	2019	101,544	2019-2026	6,057	2019-2021	3,024	2019

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
	2018		2017		2018		2017		2018		2017
Current derivative assets		$24.6		$21.1		$16.1		$15.8		$8.5		$5.3
Non-current derivative assets	3.7		4.0		1.6		1.3		2.1		2.7
Current derivative liabilities	5.6		18.7		3.1		5.0		2.5		13.7
Non-current derivative liabilities	17.7		23.0		8.1		14.4		9.6		8.6