Debt (Tables)

9 Months Ended

Sep. 30, 2016

Debt Disclosure [Line Items]

Other Short-Term Borrowings

Information regarding commercial paper classified as short-term debt was as follows (dollars in millions):

	Alliant Energy	Parent
September 30, 2016	(Consolidated)	Company	IPL	WPL
Commercial paper:
Amount outstanding	$238.3	$226.5	$—	$11.8
Weighted average remaining maturity	4 days	4 days	N/A	3 days
Weighted average interest rates	0.6%	0.7%	N/A	0.4%
Available credit facility capacity	$761.7	$73.5	$300.0	$388.2

	Alliant Energy						IPL						WPL
Three Months Ended September 30	2016			2015			2016			2015			2016	2015
Maximum amount outstanding (based on daily outstanding balances)		$248.0			$181.2			$3.1			$18.4		$55.4	$—
Average amount outstanding (based on daily outstanding balances)		$220.1			$122.4			$0.1			$0.5		$36.4	$—
Weighted average interest rates	0.6		%	0.4		%	0.6		%	0.4		%	0.4%	N/A
Nine Months Ended September 30
Maximum amount outstanding (based on daily outstanding balances)		$248.0			$181.2			$3.1			$18.4		$62.9	$—
Average amount outstanding (based on daily outstanding balances)		$210.7			$114.5			$—			$0.2		$33.2	$—
Weighted average interest rates	0.6		%	0.4		%	0.6		%	0.4		%	0.4%	N/A

IPL [Member]

Debt Disclosure [Line Items]

Other Short-Term Borrowings

Information regarding commercial paper classified as short-term debt was as follows (dollars in millions):

	Alliant Energy	Parent
September 30, 2016	(Consolidated)	Company	IPL	WPL
Commercial paper:
Amount outstanding	$238.3	$226.5	$—	$11.8
Weighted average remaining maturity	4 days	4 days	N/A	3 days
Weighted average interest rates	0.6%	0.7%	N/A	0.4%
Available credit facility capacity	$761.7	$73.5	$300.0	$388.2

	Alliant Energy						IPL						WPL
Three Months Ended September 30	2016			2015			2016			2015			2016	2015
Maximum amount outstanding (based on daily outstanding balances)		$248.0			$181.2			$3.1			$18.4		$55.4	$—
Average amount outstanding (based on daily outstanding balances)		$220.1			$122.4			$0.1			$0.5		$36.4	$—
Weighted average interest rates	0.6		%	0.4		%	0.6		%	0.4		%	0.4%	N/A
Nine Months Ended September 30
Maximum amount outstanding (based on daily outstanding balances)		$248.0			$181.2			$3.1			$18.4		$62.9	$—
Average amount outstanding (based on daily outstanding balances)		$210.7			$114.5			$—			$0.2		$33.2	$—
Weighted average interest rates	0.6		%	0.4		%	0.6		%	0.4		%	0.4%	N/A

WPL [Member]

Debt Disclosure [Line Items]

Other Short-Term Borrowings

Information regarding commercial paper classified as short-term debt was as follows (dollars in millions):

	Alliant Energy	Parent
September 30, 2016	(Consolidated)	Company	IPL	WPL
Commercial paper:
Amount outstanding	$238.3	$226.5	$—	$11.8
Weighted average remaining maturity	4 days	4 days	N/A	3 days
Weighted average interest rates	0.6%	0.7%	N/A	0.4%
Available credit facility capacity	$761.7	$73.5	$300.0	$388.2

	Alliant Energy						IPL						WPL
Three Months Ended September 30	2016			2015			2016			2015			2016	2015
Maximum amount outstanding (based on daily outstanding balances)		$248.0			$181.2			$3.1			$18.4		$55.4	$—
Average amount outstanding (based on daily outstanding balances)		$220.1			$122.4			$0.1			$0.5		$36.4	$—
Weighted average interest rates	0.6		%	0.4		%	0.6		%	0.4		%	0.4%	N/A
Nine Months Ended September 30
Maximum amount outstanding (based on daily outstanding balances)		$248.0			$181.2			$3.1			$18.4		$62.9	$—
Average amount outstanding (based on daily outstanding balances)		$210.7			$114.5			$—			$0.2		$33.2	$—
Weighted average interest rates	0.6		%	0.4		%	0.6		%	0.4		%	0.4%	N/A