Business Combination (Purchase Price Allocation) (Details) (USD $) In Millions, unless otherwise specified				12 Months Ended
	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2012 Current [Member]	Dec. 31, 2012 Preliminary [Member]
Cash				$ 116.4	$ 116.4
Restricted Cash				18.5	18.5
Accounts receivable				277.6	277.6
Inventory				123.7	123.7
Other current assets				37.3	37.3
Property, plant and equipment				2,477.8	2,548.5
Intangible assets subject to amortization				147.2	166.3
Intangible assets - indefinite-lived				5.0	5.0
Regulatory assets				217.1	201.1
Other non-current assets				58.3	58.3
Current liabilities				(413.1)	(408.2)
Debt				(1,255.1)	(1,255.1)
Deferred taxes				(551.2)	(558.2)
Regulatory liabilities				(117.0)	(117.0)
Other non-current liabilities				(216.8)	(201.5)
Redeemable preferred stock				(18.4)	(18.4)
Net Identifiable Assets Acquired, Total				907.3	994.3
Goodwill	452.8	759.1	2,576.3	2,576.3	2,489.3
Net assets acquired				$ 3,483.6	$ 3,483.6