Debt (Tables)

12 Months Ended

Dec. 31, 2014

Debt Disclosure [Line Items]

Other Short-Term Borrowings

Information regarding commercial paper classified as short-term debt and back-stopped by the credit facilities was as follows (dollars in millions):

	Alliant Energy		IPL		WPL
	2014	2013	2014	2013	2014	2013
December 31
Commercial paper:
Amount outstanding	$141.3	$279.4	$—	$—	$—	$183.7
Weighted average interest rates	0.4%	0.2%	N/A	N/A	N/A	0.1%
Weighted average remaining maturity	4 days	4 days	N/A	N/A	N/A	6 days
Available credit facility capacity	$858.7	$720.6	$300.0	$300.0	$400.0	$216.3

	Alliant Energy		IPL		WPL
	2014	2013	2014	2013	2014	2013
For the year ended
Maximum amount outstanding (based on daily outstanding balances)	$353.8	$293.9	$38.0	$26.3	$204.7	$190.0
Average amount outstanding (based on daily outstanding balances)	$255.9	$210.5	$0.2	$1.3	$122.9	$123.5
Weighted average interest rates	0.2%	0.2%	0.2%	0.4%	0.1%	0.2%

Schedule of Debt-To-Capital Ratios

The required debt-to-capital ratios compared to the actual debt-to-capital ratios at December 31, 2014 were as follows:

	Alliant Energy	IPL	WPL
Requirement, not to exceed	65%	58%	58%
Actual	52%	47%	49%

Schedule of Long-term Debt

Long-term debt, net as of December 31 was as follows (dollars in millions):

	2014									2013
	Alliant Energy			IPL			WPL			Alliant Energy			IPL			WPL
Senior Debentures:
3.3%, due 2015		$150.0			$150.0			$—			$150.0			$150.0			$—
5.875%, due 2018	100.0			100.0			—			100.0			100.0			—
7.25%, due 2018	250.0			250.0			—			250.0			250.0			—
3.65%, due 2020	200.0			200.0			—			200.0			200.0			—
3.25%, due 2024 (a)	250.0			250.0			—			—			—			—
5.5%, due 2025	50.0			50.0			—			50.0			50.0			—
6.45%, due 2033	100.0			100.0			—			100.0			100.0			—
6.3%, due 2034	125.0			125.0			—			125.0			125.0			—
6.25%, due 2039	300.0			300.0			—			300.0			300.0			—
4.7%, due 2043	250.0			250.0			—			250.0			250.0			—
	1,775.0			1,775.0			—			1,525.0			1,525.0			—
Debentures:
5%, due 2019	250.0			—			250.0			250.0			—			250.0
4.6%, due 2020	150.0			—			150.0			150.0			—			150.0
2.25%, due 2022	250.0			—			250.0			250.0			—			250.0
6.25%, due 2034	100.0			—			100.0			100.0			—			100.0
6.375%, due 2037	300.0			—			300.0			300.0			—			300.0
7.6%, due 2038	250.0			—			250.0			250.0			—			250.0
4.1%, due 2044 (b)	250.0			—			250.0			—			—			—
	1,550.0			—			1,550.0			1,300.0			—			1,300.0
Pollution Control Revenue Bonds:
5%, due 2015 (c)	16.0			—			16.0			24.5			—			24.5
5.375%, due 2015	14.6			—			14.6			14.6			—			14.6
5% (d)	—			—			—			38.4			38.4			—
	30.6			—			30.6			77.5			38.4			39.1
Other:
Term loan credit agreement through 2016, 1% at December 31, 2014 (e)	250.0			—			—			—			—			—
Term loan credit agreement through 2016, 1% at December 31, 2014 (f)	60.0			—			—			—			—			—
3.45% senior notes, due 2022	75.0			—			—			75.0			—			—
5.06% senior secured notes, due 2015 to 2024	58.9			—			—			60.5			—			—
4% senior notes (e)	—			—			—			250.0			—			—
Term loan credit agreement, 1% at December 31, 2013 (f)	—			—			—			60.0			—			—
Other, 1% at December 31, 2014, due 2015 to 2025	3.3			—			—			0.4			—			—
	447.2			—			—			445.9			—			—
Subtotal	3,802.8			1,775.0			1,580.6			3,348.4			1,563.4			1,339.1
Current maturities	(183.0		)	(150.0		)	(30.6		)	(358.5		)	(38.4		)	(8.5		)
Unamortized debt (discount) and premium, net	(13.1		)	(6.3		)	(6.7		)	(12.1		)	(5.0		)	(7.0		)
Long-term debt, net		$3,606.7			$1,618.7			$1,543.3			$2,977.8			$1,520.0			$1,323.6

(a) In 2014, IPL issued $250.0 million of 3.25% senior debentures due 2024. The proceeds from the issuance were used by IPL to reduce cash proceeds received from its sales of accounts receivable program, reduce commercial paper classified as long-term debt by $60 millionand for general corporate purposes.

(b) In 2014, WPL issued $250.0 million of 4.1% debentures due 2044. The proceeds from the issuance were used by WPL to reduce commercial paper and for general corporate purposes.

(c) In 2014, WPL retired $8.5 million of its 5% pollution control revenue bonds.

(d) In 2014, IPL retired its $38.4 million, 5% pollution control revenue bonds.

(e) In 2014, Alliant Energy entered into a $250.0 million variable-rate term loan credit agreement and used the proceeds from borrowings under this agreement to retire its $250.0 million, 4% senior notes due 2014.

(f) In 2014, Franklin County Holdings LLC, Resources’ wholly-owned subsidiary, entered into a $60.0 million variable-rate term loan credit agreement and used the proceeds to retire its borrowings under a term loan credit agreement that matured in December 2014.

Schedule of Debt Maturities

At December 31, 2014, debt maturities for 2015 through 2019 were as follows (in millions):

	2015		2016		2017		2018		2019
IPL		$150		$—		$—		$350		$—
WPL	31		—		—		—		250
Resources	2		63		5		6		6
Alliant Energy parent company	—		250		—		—		—
Alliant Energy		$183		$313		$5		$356		$256

Unamortized Debt Issuance Costs

Unamortized debt issuance costs recorded in “Deferred charges and other” on the balance sheets at December 31 were as follows (in millions):

	Alliant Energy		IPL		WPL
	2014	2013	2014	2013	2014	2013
Unamortized debt issuance costs	$22.4	$19.9	$10.7	$9.7	$10.8	$9.0

IPL [Member]

Debt Disclosure [Line Items]

Other Short-Term Borrowings

Information regarding commercial paper classified as short-term debt and back-stopped by the credit facilities was as follows (dollars in millions):

	Alliant Energy		IPL		WPL
	2014	2013	2014	2013	2014	2013
December 31
Commercial paper:
Amount outstanding	$141.3	$279.4	$—	$—	$—	$183.7
Weighted average interest rates	0.4%	0.2%	N/A	N/A	N/A	0.1%
Weighted average remaining maturity	4 days	4 days	N/A	N/A	N/A	6 days
Available credit facility capacity	$858.7	$720.6	$300.0	$300.0	$400.0	$216.3

	Alliant Energy		IPL		WPL
	2014	2013	2014	2013	2014	2013
For the year ended
Maximum amount outstanding (based on daily outstanding balances)	$353.8	$293.9	$38.0	$26.3	$204.7	$190.0
Average amount outstanding (based on daily outstanding balances)	$255.9	$210.5	$0.2	$1.3	$122.9	$123.5
Weighted average interest rates	0.2%	0.2%	0.2%	0.4%	0.1%	0.2%

Schedule of Debt-To-Capital Ratios

The required debt-to-capital ratios compared to the actual debt-to-capital ratios at December 31, 2014 were as follows:

	Alliant Energy	IPL	WPL
Requirement, not to exceed	65%	58%	58%
Actual	52%	47%	49%

Schedule of Long-term Debt

Long-term debt, net as of December 31 was as follows (dollars in millions):

	2014									2013
	Alliant Energy			IPL			WPL			Alliant Energy			IPL			WPL
Senior Debentures:
3.3%, due 2015		$150.0			$150.0			$—			$150.0			$150.0			$—
5.875%, due 2018	100.0			100.0			—			100.0			100.0			—
7.25%, due 2018	250.0			250.0			—			250.0			250.0			—
3.65%, due 2020	200.0			200.0			—			200.0			200.0			—
3.25%, due 2024 (a)	250.0			250.0			—			—			—			—
5.5%, due 2025	50.0			50.0			—			50.0			50.0			—
6.45%, due 2033	100.0			100.0			—			100.0			100.0			—
6.3%, due 2034	125.0			125.0			—			125.0			125.0			—
6.25%, due 2039	300.0			300.0			—			300.0			300.0			—
4.7%, due 2043	250.0			250.0			—			250.0			250.0			—
	1,775.0			1,775.0			—			1,525.0			1,525.0			—
Debentures:
5%, due 2019	250.0			—			250.0			250.0			—			250.0
4.6%, due 2020	150.0			—			150.0			150.0			—			150.0
2.25%, due 2022	250.0			—			250.0			250.0			—			250.0
6.25%, due 2034	100.0			—			100.0			100.0			—			100.0
6.375%, due 2037	300.0			—			300.0			300.0			—			300.0
7.6%, due 2038	250.0			—			250.0			250.0			—			250.0
4.1%, due 2044 (b)	250.0			—			250.0			—			—			—
	1,550.0			—			1,550.0			1,300.0			—			1,300.0
Pollution Control Revenue Bonds:
5%, due 2015 (c)	16.0			—			16.0			24.5			—			24.5
5.375%, due 2015	14.6			—			14.6			14.6			—			14.6
5% (d)	—			—			—			38.4			38.4			—
	30.6			—			30.6			77.5			38.4			39.1
Other:
Term loan credit agreement through 2016, 1% at December 31, 2014 (e)	250.0			—			—			—			—			—
Term loan credit agreement through 2016, 1% at December 31, 2014 (f)	60.0			—			—			—			—			—
3.45% senior notes, due 2022	75.0			—			—			75.0			—			—
5.06% senior secured notes, due 2015 to 2024	58.9			—			—			60.5			—			—
4% senior notes (e)	—			—			—			250.0			—			—
Term loan credit agreement, 1% at December 31, 2013 (f)	—			—			—			60.0			—			—
Other, 1% at December 31, 2014, due 2015 to 2025	3.3			—			—			0.4			—			—
	447.2			—			—			445.9			—			—
Subtotal	3,802.8			1,775.0			1,580.6			3,348.4			1,563.4			1,339.1
Current maturities	(183.0		)	(150.0		)	(30.6		)	(358.5		)	(38.4		)	(8.5		)
Unamortized debt (discount) and premium, net	(13.1		)	(6.3		)	(6.7		)	(12.1		)	(5.0		)	(7.0		)
Long-term debt, net		$3,606.7			$1,618.7			$1,543.3			$2,977.8			$1,520.0			$1,323.6

(a) In 2014, IPL issued $250.0 million of 3.25% senior debentures due 2024. The proceeds from the issuance were used by IPL to reduce cash proceeds received from its sales of accounts receivable program, reduce commercial paper classified as long-term debt by $60 millionand for general corporate purposes.

(b) In 2014, WPL issued $250.0 million of 4.1% debentures due 2044. The proceeds from the issuance were used by WPL to reduce commercial paper and for general corporate purposes.

(c) In 2014, WPL retired $8.5 million of its 5% pollution control revenue bonds.

(d) In 2014, IPL retired its $38.4 million, 5% pollution control revenue bonds.

(e) In 2014, Alliant Energy entered into a $250.0 million variable-rate term loan credit agreement and used the proceeds from borrowings under this agreement to retire its $250.0 million, 4% senior notes due 2014.

(f) In 2014, Franklin County Holdings LLC, Resources’ wholly-owned subsidiary, entered into a $60.0 million variable-rate term loan credit agreement and used the proceeds to retire its borrowings under a term loan credit agreement that matured in December 2014.

Schedule of Debt Maturities

At December 31, 2014, debt maturities for 2015 through 2019 were as follows (in millions):

	2015		2016		2017		2018		2019
IPL		$150		$—		$—		$350		$—
WPL	31		—		—		—		250
Resources	2		63		5		6		6
Alliant Energy parent company	—		250		—		—		—
Alliant Energy		$183		$313		$5		$356		$256

Unamortized Debt Issuance Costs

Unamortized debt issuance costs recorded in “Deferred charges and other” on the balance sheets at December 31 were as follows (in millions):

	Alliant Energy		IPL		WPL
	2014	2013	2014	2013	2014	2013
Unamortized debt issuance costs	$22.4	$19.9	$10.7	$9.7	$10.8	$9.0

WPL [Member]

Debt Disclosure [Line Items]

Other Short-Term Borrowings

Information regarding commercial paper classified as short-term debt and back-stopped by the credit facilities was as follows (dollars in millions):

	Alliant Energy		IPL		WPL
	2014	2013	2014	2013	2014	2013
December 31
Commercial paper:
Amount outstanding	$141.3	$279.4	$—	$—	$—	$183.7
Weighted average interest rates	0.4%	0.2%	N/A	N/A	N/A	0.1%
Weighted average remaining maturity	4 days	4 days	N/A	N/A	N/A	6 days
Available credit facility capacity	$858.7	$720.6	$300.0	$300.0	$400.0	$216.3

	Alliant Energy		IPL		WPL
	2014	2013	2014	2013	2014	2013
For the year ended
Maximum amount outstanding (based on daily outstanding balances)	$353.8	$293.9	$38.0	$26.3	$204.7	$190.0
Average amount outstanding (based on daily outstanding balances)	$255.9	$210.5	$0.2	$1.3	$122.9	$123.5
Weighted average interest rates	0.2%	0.2%	0.2%	0.4%	0.1%	0.2%

Schedule of Debt-To-Capital Ratios

The required debt-to-capital ratios compared to the actual debt-to-capital ratios at December 31, 2014 were as follows:

	Alliant Energy	IPL	WPL
Requirement, not to exceed	65%	58%	58%
Actual	52%	47%	49%

Schedule of Long-term Debt

Long-term debt, net as of December 31 was as follows (dollars in millions):

	2014									2013
	Alliant Energy			IPL			WPL			Alliant Energy			IPL			WPL
Senior Debentures:
3.3%, due 2015		$150.0			$150.0			$—			$150.0			$150.0			$—
5.875%, due 2018	100.0			100.0			—			100.0			100.0			—
7.25%, due 2018	250.0			250.0			—			250.0			250.0			—
3.65%, due 2020	200.0			200.0			—			200.0			200.0			—
3.25%, due 2024 (a)	250.0			250.0			—			—			—			—
5.5%, due 2025	50.0			50.0			—			50.0			50.0			—
6.45%, due 2033	100.0			100.0			—			100.0			100.0			—
6.3%, due 2034	125.0			125.0			—			125.0			125.0			—
6.25%, due 2039	300.0			300.0			—			300.0			300.0			—
4.7%, due 2043	250.0			250.0			—			250.0			250.0			—
	1,775.0			1,775.0			—			1,525.0			1,525.0			—
Debentures:
5%, due 2019	250.0			—			250.0			250.0			—			250.0
4.6%, due 2020	150.0			—			150.0			150.0			—			150.0
2.25%, due 2022	250.0			—			250.0			250.0			—			250.0
6.25%, due 2034	100.0			—			100.0			100.0			—			100.0
6.375%, due 2037	300.0			—			300.0			300.0			—			300.0
7.6%, due 2038	250.0			—			250.0			250.0			—			250.0
4.1%, due 2044 (b)	250.0			—			250.0			—			—			—
	1,550.0			—			1,550.0			1,300.0			—			1,300.0
Pollution Control Revenue Bonds:
5%, due 2015 (c)	16.0			—			16.0			24.5			—			24.5
5.375%, due 2015	14.6			—			14.6			14.6			—			14.6
5% (d)	—			—			—			38.4			38.4			—
	30.6			—			30.6			77.5			38.4			39.1
Other:
Term loan credit agreement through 2016, 1% at December 31, 2014 (e)	250.0			—			—			—			—			—
Term loan credit agreement through 2016, 1% at December 31, 2014 (f)	60.0			—			—			—			—			—
3.45% senior notes, due 2022	75.0			—			—			75.0			—			—
5.06% senior secured notes, due 2015 to 2024	58.9			—			—			60.5			—			—
4% senior notes (e)	—			—			—			250.0			—			—
Term loan credit agreement, 1% at December 31, 2013 (f)	—			—			—			60.0			—			—
Other, 1% at December 31, 2014, due 2015 to 2025	3.3			—			—			0.4			—			—
	447.2			—			—			445.9			—			—
Subtotal	3,802.8			1,775.0			1,580.6			3,348.4			1,563.4			1,339.1
Current maturities	(183.0		)	(150.0		)	(30.6		)	(358.5		)	(38.4		)	(8.5		)
Unamortized debt (discount) and premium, net	(13.1		)	(6.3		)	(6.7		)	(12.1		)	(5.0		)	(7.0		)
Long-term debt, net		$3,606.7			$1,618.7			$1,543.3			$2,977.8			$1,520.0			$1,323.6

(a) In 2014, IPL issued $250.0 million of 3.25% senior debentures due 2024. The proceeds from the issuance were used by IPL to reduce cash proceeds received from its sales of accounts receivable program, reduce commercial paper classified as long-term debt by $60 millionand for general corporate purposes.

(b) In 2014, WPL issued $250.0 million of 4.1% debentures due 2044. The proceeds from the issuance were used by WPL to reduce commercial paper and for general corporate purposes.

(c) In 2014, WPL retired $8.5 million of its 5% pollution control revenue bonds.

(d) In 2014, IPL retired its $38.4 million, 5% pollution control revenue bonds.

(e) In 2014, Alliant Energy entered into a $250.0 million variable-rate term loan credit agreement and used the proceeds from borrowings under this agreement to retire its $250.0 million, 4% senior notes due 2014.

(f) In 2014, Franklin County Holdings LLC, Resources’ wholly-owned subsidiary, entered into a $60.0 million variable-rate term loan credit agreement and used the proceeds to retire its borrowings under a term loan credit agreement that matured in December 2014.

Schedule of Debt Maturities

At December 31, 2014, debt maturities for 2015 through 2019 were as follows (in millions):

	2015		2016		2017		2018		2019
IPL		$150		$—		$—		$350		$—
WPL	31		—		—		—		250
Resources	2		63		5		6		6
Alliant Energy parent company	—		250		—		—		—
Alliant Energy		$183		$313		$5		$356		$256

Unamortized Debt Issuance Costs

Unamortized debt issuance costs recorded in “Deferred charges and other” on the balance sheets at December 31 were as follows (in millions):

	Alliant Energy		IPL		WPL
	2014	2013	2014	2013	2014	2013
Unamortized debt issuance costs	$22.4	$19.9	$10.7	$9.7	$10.8	$9.0