Asset Retirement Obligations (Tables)

3 Months Ended

Mar. 31, 2014

Schedule of Asset Retirement Obligations [Line Items]

Reconciliation Of Changes In Asset Retirement Obligations

A reconciliation of the changes in AROs associated with long-lived assets is as follows (in millions):

	Alliant Energy						IPL					WPL
	2014			2013			2014			2013		2014			2013
Balance, January 1		$109.7			$101.5			$47.9			$45.5		$52.4			$46.9
Liabilities settled	(0.5		)	(0.1		)	(0.3		)	—		(0.2		)	(0.1		)
Liabilities incurred (a)	16.5			—			16.3			—		0.2			—
Accretion expense	1.0			1.0			0.5			0.5		0.4			0.4
Balance, March 31		$126.7			$102.4			$64.4			$46.0		$52.8			$47.2

(a) In 2014, IPL recorded AROs of $12.0 million related to its Sutherland Generating Station.

IPL [Member]

Schedule of Asset Retirement Obligations [Line Items]

Reconciliation Of Changes In Asset Retirement Obligations

A reconciliation of the changes in AROs associated with long-lived assets is as follows (in millions):

	Alliant Energy						IPL					WPL
	2014			2013			2014			2013		2014			2013
Balance, January 1		$109.7			$101.5			$47.9			$45.5		$52.4			$46.9
Liabilities settled	(0.5		)	(0.1		)	(0.3		)	—		(0.2		)	(0.1		)
Liabilities incurred (a)	16.5			—			16.3			—		0.2			—
Accretion expense	1.0			1.0			0.5			0.5		0.4			0.4
Balance, March 31		$126.7			$102.4			$64.4			$46.0		$52.8			$47.2

(a) In 2014, IPL recorded AROs of $12.0 million related to its Sutherland Generating Station.

WPL [Member]

Schedule of Asset Retirement Obligations [Line Items]

Reconciliation Of Changes In Asset Retirement Obligations

A reconciliation of the changes in AROs associated with long-lived assets is as follows (in millions):

	Alliant Energy						IPL					WPL
	2014			2013			2014			2013		2014			2013
Balance, January 1		$109.7			$101.5			$47.9			$45.5		$52.4			$46.9
Liabilities settled	(0.5		)	(0.1		)	(0.3		)	—		(0.2		)	(0.1		)
Liabilities incurred (a)	16.5			—			16.3			—		0.2			—
Accretion expense	1.0			1.0			0.5			0.5		0.4			0.4
Balance, March 31		$126.7			$102.4			$64.4			$46.0		$52.8			$47.2

(a) In 2014, IPL recorded AROs of $12.0 million related to its Sutherland Generating Station.