Formation - Additional Information (Detail) (USD $) In Millions, except Share data, unless otherwise specified	0 Months Ended
	Jan. 25, 2013	Jan. 25, 2013 IPO [Member]	Jan. 25, 2013 CyrusOne L.P. [Member]	Nov. 20, 2012 CyrusOne L.P. [Member]	Mar. 31, 2014 CyrusOne L.P. [Member]	Jan. 23, 2013 CyrusOne Inc. and CyrusOne GP [Member]	Mar. 31, 2014 Cincinnati Bell Inc. [Member]	Jan. 23, 2013 Cincinnati Bell Inc. [Member]
Business Formation [Line Items]
Partnership units issued to CyrusOne Inc.				123,688,687
Common stock share issuance under initial public offering (in shares)	400,000	19,000,000
Amount received from initial public offering of common stock, net of underwriter's discount		$ 337.1
Reverse unit split executed			2.8
Operating partnership units owned			44,100,000
Partnership units exchanged	1,500,000
Proceeds from partnership units exchanged	1,500,000
Number of common shares issued to directors and employees	1,000,000
Total number of outstanding units					65,300,000
Shares purchased of Operating partnership's units						21,900,000
Combined interest held on completion of transactions						33.90%
Purchase of Operating partnership's units						$ 337.1
Remaining combined interest held								66.10%
Ownership percentage							65.30%