Condensed Consolidated and Combined Statements of Cash Flow (USD $) In Millions, unless otherwise specified	1 Months Ended		8 Months Ended	9 Months Ended	8 Months Ended	9 Months Ended
	Jan. 23, 2013 Predecessor [Member]	Jan. 23, 2013 Predecessor [Member] CyrusOne LP [Member]	Sep. 30, 2013 Successor [Member]	Sep. 30, 2014 Successor [Member]	Sep. 30, 2013 Successor [Member] CyrusOne LP [Member]	Sep. 30, 2014 Successor [Member] CyrusOne LP [Member]
Cash flows from operating activities:
Net income (loss)	$ (20.2)	$ (20.2)	$ (11.8)	$ (2.7)	$ (11.8)	$ (2.7)
Adjustments to reconcile net loss to net cash provided by operating activities:
Depreciation and amortization	5.3	5.3	63.3	87.4	63.3	87.4
Noncash interest expense	0.1	0.1	1.2	2.7	1.2	2.7
Stock-based compensation expense	0.2	0.2	4.9	7.6	4.9	7.6
Provision for bad debt write off	0	0	0.3	0.9	0.3	0.9
Deferred income tax expense, including valuation allowance charge	0.3	0.3	0	0	0	0
Loss on extinguishment of debt	0	0	1.3	0	1.3	0
Rent receivables and other assets	(9.6)	(9.6)	(0.9)	(31.3)	(0.9)	(31.3)
Accounts payable and accrued expenses	20.5	20.5	(11.3)	14.1	(11.3)	14.1
Deferred revenues	3.2	3.2	(0.9)	10.2	(0.9)	10.2
Due to affiliates	1.5	1.5	16.7	(0.6)	16.7	(0.6)
Other	0.7	0.7	0	0	0	0
Net cash (used in) provided by operating activities	2.0	2.0	62.8	88.3	62.8	88.3
Cash flows from investing activities:
Capital expenditures – acquisitions of real estate	0	0	(33.3)	0	(33.3)	0
Capital expenditures – other development	(7.7)	(7.7)	(124.6)	(194.9)	(124.6)	(194.9)
Release of restricted cash	1.9	1.9	4.4		4.4	0
Net cash provided by (used in) investing activities	(5.8)	(5.8)	(153.5)	(194.9)	(153.5)	(194.9)
Cash flows from financing activities:
Issuance of common stock/partnership units	0	0	360.5	355.9	337.1	0
Stock issuance costs	0		0	(1.3)
IPO costs	0		(23.4)	0
Acquisition of operating partnership units	0		0	(355.9)
Dividends paid	0	0	(20.7)	(37.4)	(20.7)	(37.4)
Borrowings from revolving credit agreement	0	0	0	30.0	0	30.0
Payments on capital leases and other financing arrangements	(0.6)	(0.6)	(3.7)	(3.1)	(3.7)	(3.1)
Payments to buyout capital leases	0	0	(9.6)	0	(9.6)	0
Payments to buyout other financing arrangements	0	0	(10.2)	0	(10.2)	0
Distributions to CyrusOne Inc.		0			0	(1.3)
Contributions from parent, net	0.2	0.2	0	0	0	0
Debt issuance costs	0	0	(1.3)	0	(1.3)	0
Net cash (used in) provided by financing activities	(0.4)	(0.4)	291.6	(11.8)	291.6	(11.8)
Net increase (decrease) in cash and cash equivalents	(4.2)	(4.2)	200.9	(118.4)	200.9	(118.4)
Cash and cash equivalents at beginning of period	16.5	16.5	12.3	148.8	12.3	148.8
Cash and cash equivalents at end of period	12.3	12.3	213.2	30.4	213.2	30.4
Supplemental disclosures
Cash paid for interest, net of amount capitalized	0.3	0.3	21.8	22.4	21.8	22.4
Cash paid for income taxes		0		0.4	0
Capitalized interest	0	0	1.6	3.0	1.6	3.0
Acquisition of property in accounts payable and other liabilities	15.7	15.7	30.2	50.1	30.2	50.1
Assumed liabilities in buyout of other financing obligation lease	0	0	0.2	0	0.2	0
Contribution receivable from Parent related to transaction-related compensation	19.6	19.6	0	0	0	0
Dividends / Distributions payable	0	0	10.4	14.1	10.4	14.1
Deferred IPO costs	1.7		0	0
Deferred IPO costs reclassified to additional paid in capital	0	1.7	9.5	0	1.3	0
Distribution payable to CyrusOne Inc.		$ 0			$ 2.4	$ 0