Formation and Recent Developments	12 Months Ended
Dec. 31, 2015
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Formation and Recent Developments	Formation and Recent Developments Formation Prior to November 20, 2012, CyrusOne was not an operative legal entity or a combination of legal entities. The accompanying combined financial statements of CyrusOne for such periods represent the data center assets and operations owned by Cincinnati Bell Inc. (CBI) and, unless the context otherwise requires, its consolidated subsidiaries which historically have been maintained in various legal entities, some of which had significant unrelated business activities. The accompanying financial statements for such periods have been “carved out” of CBI’s consolidated financial statements and reflect significant assumptions and allocations. The combined financial statements do not fully reflect what the financial position, results of operations and cash flows would have been had these operations been a stand-alone company during the periods presented. As a result, historical financial information is not necessarily indicative of CyrusOne’s future results of operations, financial position and cash flows. 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 123.7 million operating partnership units to CBI. On January 24, 2013, CyrusOne Inc. completed its initial public offering (the IPO) of common stock, issuing approximately 19 million shares for $337.1 million, net of underwriting 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 1.1 million shares of restricted stock to its directors and employees. In addition, on January 24, 2013, CyrusOne Inc. purchased approximately 21.9 million, or 33.9% of the operating partnership’s units for $337.1 million and assumed the controlling interest in the operating partnership. CBI retained a noncontrolling interest in the operating partnership of 66.1%. Recent Developments On June 25, 2014, CyrusOne Inc. completed a public offering of 16 million shares of its common stock, including 2.1 million 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 discounts of $15.8 million, to acquire 16 million common units of limited partnership interests in the operating partnership from CBI. On April 7, 2015, CyrusOne Inc. completed a public offering of approximately 14.3 million shares of its common stock, including approximately 1.9 million 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 $31.12 per share, or $443.8 million. CyrusOne Inc. used the proceeds of $426.0 million, net of underwriting costs of $17.8 million, to acquire approximately 14.3 million common units of limited partnership interests in the operating partnership from CBI. On June 26, 2015, CyrusOne Inc. completed a public offering of approximately 13.0 million shares of its common stock, at a price to the public of $30.00 per share, or $373.3 million, net of underwriting costs of $16.6 million. On July 1, 2015, CyrusOne used the $170.3 million to acquire approximately 6.0 million common units of limited partnership interests in the operating partnership from a subsidiary of CBI. During 2015, the Company issued $0.2 million of common shares related to the employee stock purchase plan. In total, offerings of common stock in 2015 resulted in $799.5 million of cash flow from financing activities on the consolidated and combined statements of cash flows. On July 1, 2015, CyrusOne LP acquired Cervalis for approximately $398.4 million, excluding transaction related expenses.Cervalis operates four data center facilities and two work area recovery facilities serving the New York metropolitan area On December 14, 2015, CyrusOne Inc. completed a public secondary offering of 1,350,000 shares of common stock on behalf of CBI. The Company received no proceeds from the offering. On December 31, 2015, CyrusOne Inc. completed an issuance of approximately 6.3 million newly issued shares of common stock in exchange for an equal number of operating partnership units of CyrusOne LP, held by a subsidiary of CBI. As of December 31, 2015, CyrusOne Inc. owned 100% of the 72.6 million outstanding partnership units of CyrusOne LP. As of December 31, 2015, CBI owned approximately 9.5% of the outstanding shares of common stock of CyrusOne Inc.

Formation and Recent Developments

Formation

Prior to November 20, 2012, CyrusOne was not an operative legal entity or a combination of legal entities. The accompanying combined financial statements of CyrusOne for such periods represent the data center assets and operations owned by Cincinnati Bell Inc. (CBI) and, unless the context otherwise requires, its consolidated subsidiaries which historically have been maintained in various legal entities, some of which had significant unrelated business activities. The accompanying financial statements for such periods have been “carved out” of CBI’s consolidated financial statements and reflect significant assumptions and allocations. The combined financial statements do not fully reflect what the financial position, results of operations and cash flows would have been had these operations been a stand-alone company during the periods presented. As a result, historical financial information is not necessarily indicative of CyrusOne’s future results of operations, financial position and cash flows.

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 123.7 million operating partnership units to CBI.

On January 24, 2013, CyrusOne Inc. completed its initial public offering (the IPO) of common stock, issuing approximately 19 million shares for $337.1 million, net of underwriting 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 1.1 million shares of restricted stock to its directors and employees. In addition, on January 24, 2013, CyrusOne Inc. purchased approximately 21.9 million, or 33.9% of the operating partnership’s units for $337.1 million and assumed the controlling interest in the operating partnership. CBI retained a noncontrolling interest in the operating partnership of 66.1%.

Recent Developments

On June 25, 2014, CyrusOne Inc. completed a public offering of 16 million shares of its common stock, including 2.1 million 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 discounts of $15.8 million, to acquire 16 million common units of limited partnership interests in the operating partnership from CBI.

On April 7, 2015, CyrusOne Inc. completed a public offering of approximately 14.3 million shares of its common stock, including approximately 1.9 million 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 $31.12 per share, or $443.8 million. CyrusOne Inc. used the proceeds of $426.0 million, net of underwriting costs of $17.8 million, to acquire approximately 14.3 million common units of limited partnership interests in the operating partnership from CBI.

On June 26, 2015, CyrusOne Inc. completed a public offering of approximately 13.0 million shares of its common stock, at a price to the public of $30.00 per share, or $373.3 million, net of underwriting costs of $16.6 million. On July 1, 2015, CyrusOne used the $170.3 million to acquire approximately 6.0 million common units of limited partnership interests in the operating partnership from a subsidiary of CBI.

During 2015, the Company issued $0.2 million of common shares related to the employee stock purchase plan. In total, offerings of common stock in 2015 resulted in $799.5 million of cash flow from financing activities on the consolidated and combined statements of cash flows.

On July 1, 2015, CyrusOne LP acquired Cervalis for approximately $398.4 million, excluding transaction related expenses.Cervalis operates four data center facilities and two work area recovery facilities serving the New York metropolitan area

On December 14, 2015, CyrusOne Inc. completed a public secondary offering of 1,350,000 shares of common stock on behalf of CBI. The Company received no proceeds from the offering.

On December 31, 2015, CyrusOne Inc. completed an issuance of approximately 6.3 million newly issued shares of common stock in exchange for an equal number of operating partnership units of CyrusOne LP, held by a subsidiary of CBI. As of December 31, 2015, CyrusOne Inc. owned 100% of the 72.6 million outstanding partnership units of CyrusOne LP. As of December 31, 2015, CBI owned approximately 9.5% of the outstanding shares of common stock of CyrusOne Inc.