Debt (Tables)

3 Months Ended

Mar. 31, 2017

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
March 31, 2017	(Consolidated)	Company	IPL	WPL
Commercial paper outstanding	$302.8	$202.4	$9.2	$91.2
Commercial paper weighted average interest rates	1.1%	1.2%	1.2%	0.9%
Available credit facility capacity	$697.2	$97.6	$290.8	$308.8

	Alliant Energy		IPL		WPL
Three Months Ended March 31	2017	2016	2017	2016	2017	2016
Maximum amount outstanding (based on daily outstanding balances)	$325.5	$242.6	$9.2	$—	$113.6	$55.7
Average amount outstanding (based on daily outstanding balances)	$276.5	$199.0	$0.1	$—	$79.1	$25.8
Weighted average interest rates	0.9%	0.6%	1.1%	N/A	0.7%	0.4%

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
March 31, 2017	(Consolidated)	Company	IPL	WPL
Commercial paper outstanding	$302.8	$202.4	$9.2	$91.2
Commercial paper weighted average interest rates	1.1%	1.2%	1.2%	0.9%
Available credit facility capacity	$697.2	$97.6	$290.8	$308.8

	Alliant Energy		IPL		WPL
Three Months Ended March 31	2017	2016	2017	2016	2017	2016
Maximum amount outstanding (based on daily outstanding balances)	$325.5	$242.6	$9.2	$—	$113.6	$55.7
Average amount outstanding (based on daily outstanding balances)	$276.5	$199.0	$0.1	$—	$79.1	$25.8
Weighted average interest rates	0.9%	0.6%	1.1%	N/A	0.7%	0.4%

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
March 31, 2017	(Consolidated)	Company	IPL	WPL
Commercial paper outstanding	$302.8	$202.4	$9.2	$91.2
Commercial paper weighted average interest rates	1.1%	1.2%	1.2%	0.9%
Available credit facility capacity	$697.2	$97.6	$290.8	$308.8

	Alliant Energy		IPL		WPL
Three Months Ended March 31	2017	2016	2017	2016	2017	2016
Maximum amount outstanding (based on daily outstanding balances)	$325.5	$242.6	$9.2	$—	$113.6	$55.7
Average amount outstanding (based on daily outstanding balances)	$276.5	$199.0	$0.1	$—	$79.1	$25.8
Weighted average interest rates	0.9%	0.6%	1.1%	N/A	0.7%	0.4%