Commitments and Contingencies (Details) $ in Millions	12 Months Ended
	Dec. 31, 2015 USD ($) Years	Dec. 31, 2014 USD ($)	Dec. 31, 2013 USD ($)
Operating Leases, Rent Expense	$ 10.1	$ 7.4	$ 6.5
Asset Retirement Obligation [Abstract]
Balance, beginning of period	1.6	1.7
Asset Retirement Obligation, Reclassified from Discontinued Operations	10.9	0.0
Liabilities settled	(5.0)	(0.2)
Revisions to estimated cash flow	(2.9)	0.0
Accretion expense	0.2	0.1
Balance, end of period	4.8	1.6	1.7
Letters of Credit Outstanding, Amount	$ 6.3
Long-term Purchase Commitments, Range of Years, Minimum | Years	1
Long-Term Purchase Commitments, Range of Years, Maximum | Years	3
Long-term Purchase Commitment, Amount	$ 166.0	178.0
Transaction-related compensation	0.0	$ 0.0	(42.6)
Transaction-related compensation to CyrusOne employees			$ 20.0
Operating Leases, Future Minimum Payments Due, Fiscal Year Maturity [Abstract]
2016	3.9
2017	3.7
2018	2.6
2019	2.5
2020	2.3
Thereafter	22.0
Total	37.0
Retail Store [Member]
Operating Leases, Rent Expense	$ 0.8