Derivative Instruments (Tables)

12 Months Ended

Dec. 31, 2012

Derivative [Line Items]

Notional Amounts of Derivative Instruments

As of December 31, 2012, notional amounts by delivery year related to outstanding swap contracts, option contracts, physical forward contracts, FTRs and coal contracts that were accounted for as commodity derivative instruments were as follows (units in thousands):

	2013	2014	2015	Total
Alliant Energy
Electricity (MWhs)	4,130	2,670	876	7,676
FTRs (MWs)	28	—	—	28
Natural gas (dekatherms (Dths))	72,105	7,747	450	80,302
Coal (tons)	896	981	562	2,439
IPL
Electricity (MWhs)	2,209	549	—	2,758
FTRs (MWs)	15	—	—	15
Natural gas (Dths)	57,731	3,535	225	61,491
WPL
Electricity (MWhs)	1,921	2,121	876	4,918
FTRs (MWs)	13	—	—	13
Natural gas (Dths)	14,374	4,212	225	18,811
Coal (tons)	896	981	562	2,439

Fair Value of Financial Instruments

At December 31, the fair values of current derivative assets were included in “Prepayments and other,” non-current derivative assets were included in “Deferred charges and other,” current derivative liabilities were included in “Derivative liabilities” and non-current derivative liabilities were included in “Other long-term liabilities and deferred credits” on the Consolidated Balance Sheets as follows (in millions):

	Alliant Energy				IPL				WPL
Commodity contracts	2012		2011		2012		2011		2012		2011
Current derivative assets		$23.5		$12.7		$17.0		$9.2		$6.5		$3.5
Non-current derivative assets	2.7		3.0		0.5		1.4		2.2		1.6
Current derivative liabilities	31.1		55.9		14.1		24.5		17.0		31.4
Non-current derivative liabilities	9.3		22.1		2.0		9.1		7.3		13.0

Gains and Losses from Derivative Instruments Not Designated as Hedging Instruments

Changes in unrealized gains (losses) from derivative instruments not designated as hedging instruments were recorded with offsets to regulatory assets or regulatory liabilities on the Consolidated Balance Sheets as follows (in millions):

		Alliant Energy									IPL									WPL
		2012			2011			2010			2012			2011			2010			2012			2011			2010
Commodity contracts	Regulatory assets		($37.9	)		($79.6	)		($78.4	)		($16.8	)		($42.4	)		($47.8	)		($21.1	)		($37.2	)		($30.6	)
Commodity contracts	Regulatory liabilities	20.3			9.3			11.5			13.5			6.4			10.6			6.8			2.9			0.9
Foreign exchange contracts	Regulatory liabilities	—			—			3.8			—			—			3.8			—			—			—

IPL [Member]

Derivative [Line Items]

Notional Amounts of Derivative Instruments

As of December 31, 2012, notional amounts by delivery year related to outstanding swap contracts, option contracts, physical forward contracts, FTRs and coal contracts that were accounted for as commodity derivative instruments were as follows (units in thousands):

	2013	2014	2015	Total
Alliant Energy
Electricity (MWhs)	4,130	2,670	876	7,676
FTRs (MWs)	28	—	—	28
Natural gas (dekatherms (Dths))	72,105	7,747	450	80,302
Coal (tons)	896	981	562	2,439
IPL
Electricity (MWhs)	2,209	549	—	2,758
FTRs (MWs)	15	—	—	15
Natural gas (Dths)	57,731	3,535	225	61,491
WPL
Electricity (MWhs)	1,921	2,121	876	4,918
FTRs (MWs)	13	—	—	13
Natural gas (Dths)	14,374	4,212	225	18,811
Coal (tons)	896	981	562	2,439

Fair Value of Financial Instruments

At December 31, the fair values of current derivative assets were included in “Prepayments and other,” non-current derivative assets were included in “Deferred charges and other,” current derivative liabilities were included in “Derivative liabilities” and non-current derivative liabilities were included in “Other long-term liabilities and deferred credits” on the Consolidated Balance Sheets as follows (in millions):

	Alliant Energy				IPL				WPL
Commodity contracts	2012		2011		2012		2011		2012		2011
Current derivative assets		$23.5		$12.7		$17.0		$9.2		$6.5		$3.5
Non-current derivative assets	2.7		3.0		0.5		1.4		2.2		1.6
Current derivative liabilities	31.1		55.9		14.1		24.5		17.0		31.4
Non-current derivative liabilities	9.3		22.1		2.0		9.1		7.3		13.0

Gains and Losses from Derivative Instruments Not Designated as Hedging Instruments

Changes in unrealized gains (losses) from derivative instruments not designated as hedging instruments were recorded with offsets to regulatory assets or regulatory liabilities on the Consolidated Balance Sheets as follows (in millions):

		Alliant Energy									IPL									WPL
		2012			2011			2010			2012			2011			2010			2012			2011			2010
Commodity contracts	Regulatory assets		($37.9	)		($79.6	)		($78.4	)		($16.8	)		($42.4	)		($47.8	)		($21.1	)		($37.2	)		($30.6	)
Commodity contracts	Regulatory liabilities	20.3			9.3			11.5			13.5			6.4			10.6			6.8			2.9			0.9
Foreign exchange contracts	Regulatory liabilities	—			—			3.8			—			—			3.8			—			—			—

WPL [Member]

Derivative [Line Items]

Notional Amounts of Derivative Instruments

As of December 31, 2012, notional amounts by delivery year related to outstanding swap contracts, option contracts, physical forward contracts, FTRs and coal contracts that were accounted for as commodity derivative instruments were as follows (units in thousands):

	2013	2014	2015	Total
Alliant Energy
Electricity (MWhs)	4,130	2,670	876	7,676
FTRs (MWs)	28	—	—	28
Natural gas (dekatherms (Dths))	72,105	7,747	450	80,302
Coal (tons)	896	981	562	2,439
IPL
Electricity (MWhs)	2,209	549	—	2,758
FTRs (MWs)	15	—	—	15
Natural gas (Dths)	57,731	3,535	225	61,491
WPL
Electricity (MWhs)	1,921	2,121	876	4,918
FTRs (MWs)	13	—	—	13
Natural gas (Dths)	14,374	4,212	225	18,811
Coal (tons)	896	981	562	2,439

Fair Value of Financial Instruments

At December 31, the fair values of current derivative assets were included in “Prepayments and other,” non-current derivative assets were included in “Deferred charges and other,” current derivative liabilities were included in “Derivative liabilities” and non-current derivative liabilities were included in “Other long-term liabilities and deferred credits” on the Consolidated Balance Sheets as follows (in millions):

	Alliant Energy				IPL				WPL
Commodity contracts	2012		2011		2012		2011		2012		2011
Current derivative assets		$23.5		$12.7		$17.0		$9.2		$6.5		$3.5
Non-current derivative assets	2.7		3.0		0.5		1.4		2.2		1.6
Current derivative liabilities	31.1		55.9		14.1		24.5		17.0		31.4
Non-current derivative liabilities	9.3		22.1		2.0		9.1		7.3		13.0

Gains and Losses from Derivative Instruments Not Designated as Hedging Instruments

Changes in unrealized gains (losses) from derivative instruments not designated as hedging instruments were recorded with offsets to regulatory assets or regulatory liabilities on the Consolidated Balance Sheets as follows (in millions):

		Alliant Energy									IPL									WPL
		2012			2011			2010			2012			2011			2010			2012			2011			2010
Commodity contracts	Regulatory assets		($37.9	)		($79.6	)		($78.4	)		($16.8	)		($42.4	)		($47.8	)		($21.1	)		($37.2	)		($30.6	)
Commodity contracts	Regulatory liabilities	20.3			9.3			11.5			13.5			6.4			10.6			6.8			2.9			0.9
Foreign exchange contracts	Regulatory liabilities	—			—			3.8			—			—			3.8			—			—			—