Formation	9 Months Ended
Sep. 30, 2014
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Formation	Formation Prior to November 20, 2012, CyrusOne was not an operative legal entity or a combination of legal entities. The data center assets and operations prior to such date were owned by Cincinnati Bell Inc. (“CBI”) and, unless the context otherwise requires, its consolidated subsidiaries, which assets and operations historically have been maintained in various legal entities, some of which had significant unrelated business activities. On November 20, 2012, the Operating Partnership received a contribution of interests in real estate properties and the assumption of debt and other specified liabilities from CBI in exchange for the issuance of 123,688,687 operating partnership units to CBI. On January 24, 2013, CyrusOne Inc. completed its initial public offering (“IPO”) of common stock, issuing approximately 19.0 million shares for $337.1 million, net of underwriters' discounts. At that time the Operating Partnership executed a 2.8 to 1.0 reverse unit split, resulting in CBI owning 44.1 million Operating Partnership units. In addition, CBI exchanged approximately 1.5 million of its Operating Partnership units for 1.5 million shares of CyrusOne Inc. common stock, and CBI was issued 0.4 million shares of CyrusOne Inc. common stock in repayment for transaction costs paid by CBI. CyrusOne Inc. also issued approximately 1.0 million shares of restricted stock to its directors and employees. In addition, on January 24, 2013, CyrusOne Inc., together with CyrusOne GP, purchased approximately 21.9 million, or 33.9% of the Operating Partnership’s units for $337.1 million and through CyrusOne GP assumed the controlling interest in the Operating Partnership. CBI retained a noncontrolling interest in the Operating Partnership of 66.1%. On June 25, 2014, CyrusOne Inc. completed a public offering of 15,985,000 shares of its common stock, including 2,085,000 shares of common stock issued upon the exercise in full by the underwriters of their option to purchase additional shares, at a price to the public of $23.25 per share, or $371.7 million. CyrusOne Inc. used the proceeds of $355.9 million, net of underwriting costs of $15.8 million, to acquire 15,985,000 common units of limited partnership interests in the Operating Partnership from a subsidiary of CBI. As of September 30, 2014, the total number of outstanding partnership units was 65.3 million and CBI holds a 40.8% noncontrolling interest in the Operating Partnership. CBI effectively owns approximately 43.7% of CyrusOne through its interest in outstanding shares of common stock of CyrusOne Inc. and its interest in the Operating Partnership units of CyrusOne LP.

Formation

Prior to November 20, 2012, CyrusOne was not an operative legal entity or a combination of legal entities. The data center assets and operations prior to such date were owned by Cincinnati Bell Inc. (“CBI”) and, unless the context otherwise requires, its consolidated subsidiaries, which assets and operations historically have been maintained in various legal entities, some of which had significant unrelated business activities. On November 20, 2012, the Operating Partnership received a contribution of interests in real estate properties and the assumption of debt and other specified liabilities from CBI in exchange for the issuance of 123,688,687 operating partnership units to CBI.

On January 24, 2013, CyrusOne Inc. completed its initial public offering (“IPO”) of common stock, issuing approximately 19.0 million shares for $337.1 million, net of underwriters' discounts. At that time the Operating Partnership executed a 2.8 to 1.0 reverse unit split, resulting in CBI owning 44.1 million Operating Partnership units. In addition, CBI exchanged approximately 1.5 million of its Operating Partnership units for 1.5 million shares of CyrusOne Inc. common stock, and CBI was issued 0.4 million shares of CyrusOne Inc. common stock in repayment for transaction costs paid by CBI. CyrusOne Inc. also issued approximately 1.0 million shares of restricted stock to its directors and employees. In addition, on January 24, 2013, CyrusOne Inc., together with CyrusOne GP, purchased approximately 21.9 million, or 33.9% of the Operating Partnership’s units for $337.1 million and through CyrusOne GP assumed the controlling interest in the Operating Partnership. CBI retained a noncontrolling interest in the Operating Partnership of 66.1%.

On June 25, 2014, CyrusOne Inc. completed a public offering of 15,985,000 shares of its common stock, including 2,085,000 shares of common stock issued upon the exercise in full by the underwriters of their option to purchase additional shares, at a price to the public of $23.25 per share, or $371.7 million. CyrusOne Inc. used the proceeds of $355.9 million, net of underwriting costs of $15.8 million, to acquire 15,985,000 common units of limited partnership interests in the Operating Partnership from a subsidiary of CBI.

As of September 30, 2014, the total number of outstanding partnership units was 65.3 million and CBI holds a 40.8% noncontrolling interest in the Operating Partnership. CBI effectively owns approximately 43.7% of CyrusOne through its interest in outstanding shares of common stock of CyrusOne Inc. and its interest in the Operating Partnership units of CyrusOne LP.