Debt (Tables)

9 Months Ended

Sep. 30, 2012

Debt Disclosure [Abstract]

Credit Facilities

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

	Alliant Energy	Parent
September 30, 2012	(Consolidated)	Company	IPL	WPL
Commercial paper:
Amount outstanding	$70.4	$70.4	$—	$—
Remaining maturity	1 day	1 day	N/A	N/A
Interest rates	0.4%	0.4%	N/A	N/A
Available credit facility capacity (a)	$879.6	$229.6	$250.0	$400.0

Other Short-Term Borrowings

	Alliant Energy						IPL						WPL
Three Months Ended September 30	2012			2011			2012			2011			2012			2011
Maximum amount outstanding (based on daily outstanding balances)		$185.3			$22.1			$19.5			$18.0			$35.6			$—
Average amount outstanding (based on daily outstanding balances)		$133.0			$2.6			$1.3			$1.7			$11.9			$—
Weighted average interest rates	0.4		%	0.4		%	0.4		%	0.3		%	0.3		%	N/A
Nine Months Ended September 30
Maximum amount outstanding (based on daily outstanding balances)		$185.3			$96.5			$35.4			$54.4			$35.6			$96.5
Average amount outstanding (based on daily outstanding balances)		$100.2			$28.7			$7.2			$7.1			$13.3			$23.0
Weighted average interest rates	0.4		%	0.3		%	0.4		%	0.3		%	0.3		%	0.3		%

(a) Alliant Energy’s and IPL’s available credit facility capacities reflect outstanding commercial paper classified as both short- and long-term debt at September 30, 2012. Refer to Note 7(b) for further discussion of $50 million of commercial paper outstanding at September 30, 2012 classified as long-term debt.