Jointly-Owned Electric Utility Plant (Tables)

12 Months Ended

Dec. 31, 2016

Jointly Owned Electric Utility Plant [Line Items]

Components of Jointly-Owned Electric Utility Plants

Information relative to IPL’s and WPL’s ownership interest in these jointly-owned coal-fired EGUs at December 31, 2016 was as follows (dollars in millions):

					Accumulated		Construction
	Ownership		Electric		Provision for		Work in
	Interest %		Plant		Depreciation		Progress
IPL
Ottumwa Unit 1	48.0	%		$489.4		$137.3		$11.1
George Neal Unit 4	25.7	%	185.2		80.8		1.6
George Neal Unit 3	28.0	%	150.7		49.1		0.3
Louisa Unit 1	4.0	%	36.5		21.8		0.6
			861.8		289.0		13.6
WPL
Columbia Units 1-2	46.2	%	640.2		185.0		51.0
Edgewater Unit 4	68.2	%	99.4		58.4		0.2
			739.6		243.4		51.2
Alliant Energy				$1,601.4		$532.4		$64.8

IPL [Member]

Jointly Owned Electric Utility Plant [Line Items]

Components of Jointly-Owned Electric Utility Plants

Information relative to IPL’s and WPL’s ownership interest in these jointly-owned coal-fired EGUs at December 31, 2016 was as follows (dollars in millions):

					Accumulated		Construction
	Ownership		Electric		Provision for		Work in
	Interest %		Plant		Depreciation		Progress
IPL
Ottumwa Unit 1	48.0	%		$489.4		$137.3		$11.1
George Neal Unit 4	25.7	%	185.2		80.8		1.6
George Neal Unit 3	28.0	%	150.7		49.1		0.3
Louisa Unit 1	4.0	%	36.5		21.8		0.6
			861.8		289.0		13.6
WPL
Columbia Units 1-2	46.2	%	640.2		185.0		51.0
Edgewater Unit 4	68.2	%	99.4		58.4		0.2
			739.6		243.4		51.2
Alliant Energy				$1,601.4		$532.4		$64.8

WPL [Member]

Jointly Owned Electric Utility Plant [Line Items]

Components of Jointly-Owned Electric Utility Plants

Information relative to IPL’s and WPL’s ownership interest in these jointly-owned coal-fired EGUs at December 31, 2016 was as follows (dollars in millions):

					Accumulated		Construction
	Ownership		Electric		Provision for		Work in
	Interest %		Plant		Depreciation		Progress
IPL
Ottumwa Unit 1	48.0	%		$489.4		$137.3		$11.1
George Neal Unit 4	25.7	%	185.2		80.8		1.6
George Neal Unit 3	28.0	%	150.7		49.1		0.3
Louisa Unit 1	4.0	%	36.5		21.8		0.6
			861.8		289.0		13.6
WPL
Columbia Units 1-2	46.2	%	640.2		185.0		51.0
Edgewater Unit 4	68.2	%	99.4		58.4		0.2
			739.6		243.4		51.2
Alliant Energy				$1,601.4		$532.4		$64.8