Investment in CyrusOne - Schedule of Related Party Transactions (Details) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Operating costs and expenses:
Transaction-related compensation to CyrusOne employees	$ 20.0
Balance Sheet Related Disclosures [Abstract]
Dividends receivable	7.1	0	0
Receivable from CyrusOne	9.2	0
Payable to CyrusOne	0.5	0
CyrusOne [Member]
Related Party Transaction [Line Items]
Income Tax Receivable from Related Party	1.5
Revenue:
Services provided to CyrusOne	2.1
Operating costs and expenses:
Transaction-related compensation to CyrusOne employees	20.0
Charges for services provided by CyrusOne	8.8
Administrative services provided to CyrusOne	(0.6)
Total operating costs and expenses	28.2
Balance Sheet Related Disclosures [Abstract]
Accounts receivable	2.1
Dividends receivable	7.1
Receivable from CyrusOne	9.2
Accounts payable	0.5
Payable to CyrusOne	$ 0.5