Receivables (Tables)

12 Months Ended

Dec. 31, 2011

Receivables [Abstract]

Maximum And Average Outstanding Cash Proceeds

	2011		2010		2009
Maximum outstanding aggregate cash proceeds (based on daily outstanding balances)	$	160.0	$	160.0	$	170.0
Average outstanding aggregate cash proceeds (based on daily outstanding balances)		118.1		78.1		113.0
Costs incurred		1.5		1.4		2.1

Receivables Sold Under The Agreement

	2011		2010
Customer accounts receivable	$	122.4	$	133.0
Unbilled utility revenues		65.4		80.9
Other receivables		7.5		5.7
Receivables sold		195.3		219.6
Less: cash proceeds (a)		140.0		65.0
Deferred proceeds		55.3		154.6
Less: allowance for doubtful accounts		1.6		1.7
Fair value of deferred proceeds	$	53.7	$	152.9
Outstanding receivables past due	$	15.9	$	14.1

(a) Changes in cash proceeds are recorded in "Sales of accounts receivable" in operating activities in Alliant Energy's and IPL's Consolidated Statements of Cash Flows.

Additional Attributes Of Receivables Sold Under The Agreement

	2011		2010
Collections reinvested in receivables	$	1,795.7	$	1,354.2
Credit losses, net of recoveries		10.9		7.9

Advances For Customer Energy Efficiency Projects

	Alliant Energy				IPL				WPL
	2011		2010		2011		2010		2011		2010
Current portion	$	22.2	$	28.0	$	1.7	$	3.0	$	20.5	$	25.0
Non-current portion		28.2		48.3		1.7		4.6		26.5		43.7
	$	50.4	$	76.3	$	3.4	$	7.6	$	47.0	$	68.7