Commitments And Contingencies (Tables)

12 Months Ended

Dec. 31, 2017

Long-term Purchase Commitment [Line Items]

Other Purchase Obligations

At December 31, 2017, minimum future commitments related to these purchase obligations were as follows (in millions):

Alliant Energy	2018		2019		2020		2021		2022		Thereafter		Total
Purchased power (a)		$188		$159		$135		$149		$140		$461		$1,232
Natural gas	229		140		130		110		84		253		946
Coal (b)	107		59		21		5		—		—		192
Other (c)	21		6		6		3		2		2		40
		$545		$364		$292		$267		$226		$716		$2,410

IPL	2018		2019		2020		2021		2022		Thereafter		Total
Purchased power (a)		$130		$144		$135		$149		$140		$461		$1,159
Natural gas	126		58		44		32		22		102		384
Coal (b)	51		31		11		5		—		—		98
Other (c)	15		3		3		3		2		2		28
		$322		$236		$193		$189		$164		$565		$1,669

WPL	2018		2019		2020		2021		2022		Thereafter		Total
Purchased power (a)		$58		$15		$—		$—		$—		$—		$73
Natural gas	103		82		86		78		62		151		562
Coal (b)	56		28		10		—		—		—		94
Other (c)	5		1		—		—		—		—		6
		$222		$126		$96		$78		$62		$151		$735

(a) Includes payments required by PPAs for capacity rights and minimum quantities of MWhs required to be purchased.

(b) Corporate Services entered into system-wide coal contracts on behalf of IPL and WPL that include minimum future commitments. These commitments were assigned to IPL and WPL based on information available as of December 31, 2017 regarding expected future usage, which is subject to change.

(c) Includes individual commitments incurred during the normal course of business that exceeded $1 million at December 31, 2017.

Schedule of Environmental Liabilities

At December 31, 2017, estimated future costs expected to be incurred for the investigation, remediation and monitoring of the MGP sites, as well as environmental liabilities recorded on the balance sheets for these sites, which are not discounted, were as follows (in millions). At December 31, 2017, such amounts for WPL were not material.

	Alliant Energy				IPL
Range of estimated future costs		$11	-	$30		$9	-	$27
Current and non-current environmental liabilities	15				13

IPL [Member]

Long-term Purchase Commitment [Line Items]

Other Purchase Obligations

At December 31, 2017, minimum future commitments related to these purchase obligations were as follows (in millions):

Alliant Energy	2018		2019		2020		2021		2022		Thereafter		Total
Purchased power (a)		$188		$159		$135		$149		$140		$461		$1,232
Natural gas	229		140		130		110		84		253		946
Coal (b)	107		59		21		5		—		—		192
Other (c)	21		6		6		3		2		2		40
		$545		$364		$292		$267		$226		$716		$2,410

IPL	2018		2019		2020		2021		2022		Thereafter		Total
Purchased power (a)		$130		$144		$135		$149		$140		$461		$1,159
Natural gas	126		58		44		32		22		102		384
Coal (b)	51		31		11		5		—		—		98
Other (c)	15		3		3		3		2		2		28
		$322		$236		$193		$189		$164		$565		$1,669

WPL	2018		2019		2020		2021		2022		Thereafter		Total
Purchased power (a)		$58		$15		$—		$—		$—		$—		$73
Natural gas	103		82		86		78		62		151		562
Coal (b)	56		28		10		—		—		—		94
Other (c)	5		1		—		—		—		—		6
		$222		$126		$96		$78		$62		$151		$735

(a) Includes payments required by PPAs for capacity rights and minimum quantities of MWhs required to be purchased.

(b) Corporate Services entered into system-wide coal contracts on behalf of IPL and WPL that include minimum future commitments. These commitments were assigned to IPL and WPL based on information available as of December 31, 2017 regarding expected future usage, which is subject to change.

(c) Includes individual commitments incurred during the normal course of business that exceeded $1 million at December 31, 2017.

Schedule of Environmental Liabilities

At December 31, 2017, estimated future costs expected to be incurred for the investigation, remediation and monitoring of the MGP sites, as well as environmental liabilities recorded on the balance sheets for these sites, which are not discounted, were as follows (in millions). At December 31, 2017, such amounts for WPL were not material.

	Alliant Energy				IPL
Range of estimated future costs		$11	-	$30		$9	-	$27
Current and non-current environmental liabilities	15				13

WPL [Member]

Long-term Purchase Commitment [Line Items]

Other Purchase Obligations

At December 31, 2017, minimum future commitments related to these purchase obligations were as follows (in millions):

Alliant Energy	2018		2019		2020		2021		2022		Thereafter		Total
Purchased power (a)		$188		$159		$135		$149		$140		$461		$1,232
Natural gas	229		140		130		110		84		253		946
Coal (b)	107		59		21		5		—		—		192
Other (c)	21		6		6		3		2		2		40
		$545		$364		$292		$267		$226		$716		$2,410

IPL	2018		2019		2020		2021		2022		Thereafter		Total
Purchased power (a)		$130		$144		$135		$149		$140		$461		$1,159
Natural gas	126		58		44		32		22		102		384
Coal (b)	51		31		11		5		—		—		98
Other (c)	15		3		3		3		2		2		28
		$322		$236		$193		$189		$164		$565		$1,669

WPL	2018		2019		2020		2021		2022		Thereafter		Total
Purchased power (a)		$58		$15		$—		$—		$—		$—		$73
Natural gas	103		82		86		78		62		151		562
Coal (b)	56		28		10		—		—		—		94
Other (c)	5		1		—		—		—		—		6
		$222		$126		$96		$78		$62		$151		$735

(a) Includes payments required by PPAs for capacity rights and minimum quantities of MWhs required to be purchased.

(b) Corporate Services entered into system-wide coal contracts on behalf of IPL and WPL that include minimum future commitments. These commitments were assigned to IPL and WPL based on information available as of December 31, 2017 regarding expected future usage, which is subject to change.

(c) Includes individual commitments incurred during the normal course of business that exceeded $1 million at December 31, 2017.