Debt (Tables)

3 Months Ended

Mar. 31, 2012

Debt [Abstract]

Credit Facilities

At March 31, 2012	Alliant Energy (Consolidated)			Parent Company			IPL		WPL
Commercial paper:
Amount outstanding	$	57.0		$	33.7		$		$	23.3
Remaining maturity		2 days			2 days			N/A		2 days
Weighted average interest rates		0.3	%		0.4	%		N/A		0.3	%
Available credit facility capacity (a)	$	918.0		$	266.3		$	275.0	$	376.7

Other Short-Term Borrowings

	Alliant Energy						IPL						WPL
For the quarter ended March 31	2012			2011			2012			2011			2012			2011
Maximum amount outstanding (based on daily outstanding balances)	$	102.8		$	96.5		$	35.4		$	12.1		$	32.7		$	96.5
Average amount outstanding (based on daily outstanding balances)	$	66.4		$	55.4		$	12.8		$	1.2		$	13.1		$	55.4
Weighted average interest rates		0.3	%		0.3	%		0.4	%		0.3	%		0.2	%		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 March 31, 2012. Refer to Note 7(b) for further discussion of $25 million of commercial paper outstanding at March 31, 2012 classified as long-term debt.