Debt (Tables)

3 Months Ended

Mar. 31, 2018

Debt Disclosure [Line Items]

Other Short-Term Borrowings

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

March 31, 2018	Alliant Energy	IPL	WPL
Commercial paper outstanding	$336.4	$—	$30.6
Commercial paper weighted average interest rates	2.3%	N/A	1.8%
Available credit facility capacity (a)	$617.7	$204.1	$319.4

	Alliant Energy		IPL		WPL
Three Months Ended March 31	2018	2017	2018	2017	2018	2017
Maximum amount outstanding (based on daily outstanding balances)	$336.4	$325.5	$3.0	$9.2	$36.7	$113.6
Average amount outstanding (based on daily outstanding balances)	$310.1	$276.5	$—	$0.1	$11.5	$79.1
Weighted average interest rates	1.9%	0.9%	1.8%	1.1%	1.6%	0.7%

(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, 2018.

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):

March 31, 2018	Alliant Energy	IPL	WPL
Commercial paper outstanding	$336.4	$—	$30.6
Commercial paper weighted average interest rates	2.3%	N/A	1.8%
Available credit facility capacity (a)	$617.7	$204.1	$319.4

	Alliant Energy		IPL		WPL
Three Months Ended March 31	2018	2017	2018	2017	2018	2017
Maximum amount outstanding (based on daily outstanding balances)	$336.4	$325.5	$3.0	$9.2	$36.7	$113.6
Average amount outstanding (based on daily outstanding balances)	$310.1	$276.5	$—	$0.1	$11.5	$79.1
Weighted average interest rates	1.9%	0.9%	1.8%	1.1%	1.6%	0.7%

(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, 2018.

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):

March 31, 2018	Alliant Energy	IPL	WPL
Commercial paper outstanding	$336.4	$—	$30.6
Commercial paper weighted average interest rates	2.3%	N/A	1.8%
Available credit facility capacity (a)	$617.7	$204.1	$319.4

	Alliant Energy		IPL		WPL
Three Months Ended March 31	2018	2017	2018	2017	2018	2017
Maximum amount outstanding (based on daily outstanding balances)	$336.4	$325.5	$3.0	$9.2	$36.7	$113.6
Average amount outstanding (based on daily outstanding balances)	$310.1	$276.5	$—	$0.1	$11.5	$79.1
Weighted average interest rates	1.9%	0.9%	1.8%	1.1%	1.6%	0.7%

(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, 2018.