Investments (Tables)

9 Months Ended

Sep. 30, 2017

Schedule of Investments [Line Items]

Unconsolidated Equity Investments

Equity (income) loss from unconsolidated investments accounted for under the equity method of accounting for the three and nine months ended September 30 was as follows (in millions):

	Alliant Energy												WPL
	Three Months						Nine Months						Three Months						Nine Months
	2017			2016			2017			2016			2017			2016			2017			2016
ATC Investment		($10.1	)		($9.1	)		($32.7	)		($28.6	)		$—			($9.1	)		$—			($28.6	)
Other	—			(0.1		)	(0.2		)	(0.2		)	(0.2		)	(0.2		)	(0.4		)	(0.4		)
		($10.1	)		($9.2	)		($32.9	)		($28.8	)		($0.2	)		($9.3	)		($0.4	)		($29.0	)

WPL [Member]

Schedule of Investments [Line Items]

Unconsolidated Equity Investments

Equity (income) loss from unconsolidated investments accounted for under the equity method of accounting for the three and nine months ended September 30 was as follows (in millions):

	Alliant Energy												WPL
	Three Months						Nine Months						Three Months						Nine Months
	2017			2016			2017			2016			2017			2016			2017			2016
ATC Investment		($10.1	)		($9.1	)		($32.7	)		($28.6	)		$—			($9.1	)		$—			($28.6	)
Other	—			(0.1		)	(0.2		)	(0.2		)	(0.2		)	(0.2		)	(0.4		)	(0.4		)
		($10.1	)		($9.2	)		($32.9	)		($28.8	)		($0.2	)		($9.3	)		($0.4	)		($29.0	)