Investment in CyrusOne - Schedule of Related Party Transactions (Details) - USD ($) $ / shares in Units, $ in Millions	11 Months Ended	12 Months Ended
	Dec. 31, 2013	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Operating costs and expenses:
Transaction-related compensation to CyrusOne employees				$ 20.0
Dividends received from CyrusOne		$ 22.2	$ 28.4	21.3
Balance Sheet Related Disclosures [Abstract]
Receivable from CyrusOne		2.2	7.7
CyrusOne [Member]
Revenue:
Services provided to CyrusOne	$ 2.1	1.3	1.7
Operating costs and expenses:
Transaction-related compensation to CyrusOne employees	20.0	0.0	0.0
Charges for services provided by CyrusOne	8.8	10.2	9.1
Administrative services provided to CyrusOne	(0.6)	(0.4)	(0.5)
Total operating costs and expenses	28.2	9.8	8.6
Income Tax Receivable from Related Party		0.0	1.7
Balance Sheet Related Disclosures [Abstract]
Accounts receivable		0.1	1.7
Dividends receivable	$ 7.1	2.1	6.0	$ 7.1
Receivable from CyrusOne		2.2	7.7
Payable to CyrusOne		$ 1.5	$ 0.4
CyrusOne [Member]
Operating costs and expenses:
Dividends Payable, Amount Per Share		$ 0.32