Investment in CyrusOne (Details) (USD $) In Millions, except Per Share data, unless otherwise specified	3 Months Ended		9 Months Ended				3 Months Ended	9 Months Ended
	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013	Sep. 30, 2012	Dec. 31, 2012	Dec. 31, 2011	Sep. 30, 2013 CyrusOne [Member]	Sep. 30, 2013 CyrusOne [Member]	Jan. 24, 2013 CyrusOne [Member]
Schedule of Equity Method Investments [Line Items]
Total ownership interests in CyrusOne, Percentage	69.00%		69.00%
Loss from CyrusOne	$ 1.5	$ 0	$ 8.1	$ 0
Equity Method Investments, Fair Value Disclosure	845.1		845.1		0
Dividends received from CyrusOne	7.2		14.2	0
Dividends Payable, Amount Per Share							$ 0.16	$ 0.16
Equity Method Investment, Summarized Financial Information, Assets [Abstract]
Cash	413.7	7.7	413.7	7.7	23.6	73.7			12.2
Receivables	153.4		153.4		199.0				41.5
Other current assets	3.6		3.6		11.6				13.4
Property, plant and equipment	892.5		892.5		1,587.4				736.2
Goodwill and intangibles									377.7
Other noncurrent assets	44.1		44.1		86.3				44.0
Total assets	2,551.7		2,551.7		2,872.4				1,225.0
Equity Method Investment, Summarized Financial Information, Liabilities [Abstract]
Current portion of long-term debt	508.9		508.9		13.4				6.3
Accounts payable	107.3		107.3		135.6				29.4
Unearned revenue and customer deposits	34.3		34.3		51.2				24.1
Other current liabilities	32.2		32.2		40.2				12.9
Long-term debt	2,108.2		2,108.2		2,676.0				550.3
Other noncurrent liabilities	70.9		70.9		176.5				92.3
Total liabilities	3,238.9		3,238.9		3,570.6				715.3
Equity Method Investment, Financial Statement, Reported Amounts [Abstract]
Net assets			509.7	0
Equity Method Investment, Summarized Financial Information, Income Statement [Abstract]
Revenue							67.5	176.1
Operating income	57.7	66.0	123.7	212.2			8.5	19.9
Net loss							$ (2.2)	$ (11.8)