Asset Retirement Obligations (AROs) (Reconciliation Of Changes In Asset Retirement Obligations) (Details) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2013		Dec. 31, 2012
Asset Retirement Obligation, Roll Forward Analysis [Roll Forward]
Balance, January 1	$ 101.5		$ 91.1
Revisions in estimated cash flows	5.6	[1]	(6.4)	[1]
Liabilities settled	(2.3)		(3.4)
Liabilities incurred	1.2	[2]	16.8	[2]
Accretion expense	3.7		3.4
Balance, December 31	109.7		101.5
IPL [Member]
Asset Retirement Obligation, Roll Forward Analysis [Roll Forward]
Balance, January 1	45.5		56.2
Revisions in estimated cash flows	0.1	[1]	(9.2)	[1]
Liabilities settled	(0.6)		(3.3)
Liabilities incurred	1.2	[2]	0	[2]
Accretion expense	1.7		1.8
Balance, December 31	47.9		45.5
WPL [Member]
Asset Retirement Obligation, Roll Forward Analysis [Roll Forward]
Balance, January 1	46.9		34.9
Revisions in estimated cash flows	5.5	[1]	2.8	[1]
Liabilities settled	(1.7)		(0.1)
Liabilities incurred	0	[2]	7.7	[2]
Accretion expense	1.7		1.6
Balance, December 31	52.4		46.9
Sixth Street [Member] | IPL [Member]
Asset Retirement Obligation, Roll Forward Analysis [Roll Forward]
Revisions in estimated cash flows			(8.2)
Franklin County Wind Project [Member] | Resources [Member]
Asset Retirement Obligation, Roll Forward Analysis [Roll Forward]
Liabilities incurred			9.1
Nelson Dewey [Member] | WPL [Member]
Asset Retirement Obligation, Roll Forward Analysis [Roll Forward]
Liabilities incurred			$ 7.6

[1] In 2012, IPL recorded revisions in estimated cash flows of ($8.2) million based on revised remediation timing and cost information for asbestos remediation at Sixth Street.

[2] In 2012, Resources recorded AROs of $9.1 million related to its Franklin County wind project and WPL recorded AROs of $7.6 million related to Nelson Dewey.