Debt (Tables)

3 Months Ended

Mar. 31, 2013

Debt Disclosure [Line Items]

Other Short-Term Borrowings

Information regarding commercial paper classified as short-term debt and back-stopped by Alliant Energy’s, IPL’s and WPL’s credit facilities was as follows (dollars in millions):

	Alliant Energy	Parent
March 31, 2013	(Consolidated)	Company	IPL	WPL
Commercial paper:
Amount outstanding	$243.4	$83.4	$—	$160.0
Weighted average remaining maturity	3 days	2 days	N/A	3 days
Weighted average interest rates	0.2%	0.3%	N/A	0.2%
Available credit facility capacity (a)	$721.6	$216.6	$265.0	$240.0

	Alliant Energy						IPL						WPL
Three Months Ended March 31	2013			2012			2013			2012			2013			2012
Maximum amount outstanding (based on daily outstanding balances)		$243.4			$102.8			$26.3			$35.4			$160.0			$32.7
Average amount outstanding (based on daily outstanding balances)		$170.8			$66.4			$4.8			$12.8			$72.9			$13.1
Weighted average interest rates	0.3		%	0.3		%	0.4		%	0.4		%	0.2		%	0.2		%

(a) Alliant Energy’s and IPL’s available credit facility capacities reflect outstanding commercial paper classified as both short- and long-term debt at March 31, 2013. Refer to Note 8(b) for further discussion of $35 million of commercial paper outstanding at March 31, 2013 classified as long-term debt on Alliant Energy’s and IPL’s Condensed Consolidated Balance Sheets.

IPL [Member]

Debt Disclosure [Line Items]

Other Short-Term Borrowings

Information regarding commercial paper classified as short-term debt and back-stopped by Alliant Energy’s, IPL’s and WPL’s credit facilities was as follows (dollars in millions):

	Alliant Energy	Parent
March 31, 2013	(Consolidated)	Company	IPL	WPL
Commercial paper:
Amount outstanding	$243.4	$83.4	$—	$160.0
Weighted average remaining maturity	3 days	2 days	N/A	3 days
Weighted average interest rates	0.2%	0.3%	N/A	0.2%
Available credit facility capacity (a)	$721.6	$216.6	$265.0	$240.0

	Alliant Energy						IPL						WPL
Three Months Ended March 31	2013			2012			2013			2012			2013			2012
Maximum amount outstanding (based on daily outstanding balances)		$243.4			$102.8			$26.3			$35.4			$160.0			$32.7
Average amount outstanding (based on daily outstanding balances)		$170.8			$66.4			$4.8			$12.8			$72.9			$13.1
Weighted average interest rates	0.3		%	0.3		%	0.4		%	0.4		%	0.2		%	0.2		%

(a) Alliant Energy’s and IPL’s available credit facility capacities reflect outstanding commercial paper classified as both short- and long-term debt at March 31, 2013. Refer to Note 8(b) for further discussion of $35 million of commercial paper outstanding at March 31, 2013 classified as long-term debt on Alliant Energy’s and IPL’s Condensed Consolidated Balance Sheets.

WPL [Member]

Debt Disclosure [Line Items]

Other Short-Term Borrowings

Information regarding commercial paper classified as short-term debt and back-stopped by Alliant Energy’s, IPL’s and WPL’s credit facilities was as follows (dollars in millions):

	Alliant Energy	Parent
March 31, 2013	(Consolidated)	Company	IPL	WPL
Commercial paper:
Amount outstanding	$243.4	$83.4	$—	$160.0
Weighted average remaining maturity	3 days	2 days	N/A	3 days
Weighted average interest rates	0.2%	0.3%	N/A	0.2%
Available credit facility capacity (a)	$721.6	$216.6	$265.0	$240.0

	Alliant Energy						IPL						WPL
Three Months Ended March 31	2013			2012			2013			2012			2013			2012
Maximum amount outstanding (based on daily outstanding balances)		$243.4			$102.8			$26.3			$35.4			$160.0			$32.7
Average amount outstanding (based on daily outstanding balances)		$170.8			$66.4			$4.8			$12.8			$72.9			$13.1
Weighted average interest rates	0.3		%	0.3		%	0.4		%	0.4		%	0.2		%	0.2		%

(a) Alliant Energy’s and IPL’s available credit facility capacities reflect outstanding commercial paper classified as both short- and long-term debt at March 31, 2013. Refer to Note 8(b) for further discussion of $35 million of commercial paper outstanding at March 31, 2013 classified as long-term debt on Alliant Energy’s and IPL’s Condensed Consolidated Balance Sheets.