Debt (Tables)

6 Months Ended

Jun. 30, 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	Parent
June 30, 2014	(Consolidated)	Company	IPL	WPL
Commercial paper:
Amount outstanding	$307.9	$149.9	$—	$158.0
Weighted average remaining maturity	1 day	1 day	N/A	1 day
Weighted average interest rates	0.2%	0.2%	N/A	0.1%
Available credit facility capacity	$692.1	$150.1	$300.0	$242.0

	Alliant Energy						IPL						WPL
Three Months Ended June 30	2014			2013			2014			2013			2014			2013
Maximum amount outstanding (based on daily outstanding balances)		$311.6			$223.1			$6.0			$6.0			$168.4			$159.4
Average amount outstanding (based on daily outstanding balances)		$262.7			$191.4			$0.1			$0.2			$141.8			$125.7
Weighted average interest rates	0.2		%	0.2		%	0.2		%	0.3		%	0.1		%	0.2		%
Six Months Ended June 30
Maximum amount outstanding (based on daily outstanding balances)		$316.2			$243.4			$10.0			$26.3			$204.7			$160.0
Average amount outstanding (based on daily outstanding balances)		$269.1			$181.2			$0.2			$2.5			$157.3			$99.4
Weighted average interest rates	0.2		%	0.3		%	0.2		%	0.4		%	0.1		%	0.2		%

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	Parent
June 30, 2014	(Consolidated)	Company	IPL	WPL
Commercial paper:
Amount outstanding	$307.9	$149.9	$—	$158.0
Weighted average remaining maturity	1 day	1 day	N/A	1 day
Weighted average interest rates	0.2%	0.2%	N/A	0.1%
Available credit facility capacity	$692.1	$150.1	$300.0	$242.0

	Alliant Energy						IPL						WPL
Three Months Ended June 30	2014			2013			2014			2013			2014			2013
Maximum amount outstanding (based on daily outstanding balances)		$311.6			$223.1			$6.0			$6.0			$168.4			$159.4
Average amount outstanding (based on daily outstanding balances)		$262.7			$191.4			$0.1			$0.2			$141.8			$125.7
Weighted average interest rates	0.2		%	0.2		%	0.2		%	0.3		%	0.1		%	0.2		%
Six Months Ended June 30
Maximum amount outstanding (based on daily outstanding balances)		$316.2			$243.4			$10.0			$26.3			$204.7			$160.0
Average amount outstanding (based on daily outstanding balances)		$269.1			$181.2			$0.2			$2.5			$157.3			$99.4
Weighted average interest rates	0.2		%	0.3		%	0.2		%	0.4		%	0.1		%	0.2		%

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	Parent
June 30, 2014	(Consolidated)	Company	IPL	WPL
Commercial paper:
Amount outstanding	$307.9	$149.9	$—	$158.0
Weighted average remaining maturity	1 day	1 day	N/A	1 day
Weighted average interest rates	0.2%	0.2%	N/A	0.1%
Available credit facility capacity	$692.1	$150.1	$300.0	$242.0

	Alliant Energy						IPL						WPL
Three Months Ended June 30	2014			2013			2014			2013			2014			2013
Maximum amount outstanding (based on daily outstanding balances)		$311.6			$223.1			$6.0			$6.0			$168.4			$159.4
Average amount outstanding (based on daily outstanding balances)		$262.7			$191.4			$0.1			$0.2			$141.8			$125.7
Weighted average interest rates	0.2		%	0.2		%	0.2		%	0.3		%	0.1		%	0.2		%
Six Months Ended June 30
Maximum amount outstanding (based on daily outstanding balances)		$316.2			$243.4			$10.0			$26.3			$204.7			$160.0
Average amount outstanding (based on daily outstanding balances)		$269.1			$181.2			$0.2			$2.5			$157.3			$99.4
Weighted average interest rates	0.2		%	0.3		%	0.2		%	0.4		%	0.1		%	0.2		%