CyrusOne (CONE) 10-K 22 Feb 18 2017 FY Annual report Financial data

Document and Entity Information

Document and Entity Information - USD ($) $ in Billions	12 Months Ended
	Dec. 31, 2017	Feb. 13, 2018	Jun. 30, 2017
Document and Entity Information [Abstract]
Document Type	10-K
Amendment Flag	false
Document Period End Date	Dec. 31, 2017
Document Fiscal Year Focus	2,017
Document Fiscal Period Focus	FY
Trading Symbol	CONE
Entity Registrant Name	CyrusOne Inc.
Entity Central Index Key	1,553,023
Current Fiscal Year End Date	--12-31
Entity Well-known Seasoned Issuer	Yes
Entity Current Reporting Status	Yes
Entity Voluntary Filers	No
Entity Public Float			$ 5.1
Entity Filer Category	Large Accelerated Filer
Entity Common Stock, Shares Outstanding		96,125,762

Consolidated Balance Sheets

Consolidated Balance Sheets - USD ($) $ in Millions	Dec. 31, 2017	Dec. 31, 2016
Investment in real estate:
Land	$ 177.1	$ 142.7
Buildings and improvements	1,371.4	1,008.9
Equipment	1,813.9	1,042.9
Construction in progress	478.4	407.1
Subtotal	3,840.8	2,601.6
Accumulated depreciation	(782.4)	(578.5)
Net investment in real estate	3,058.4	2,023.1
Cash and cash equivalents	151.9	14.6
Rent and other receivables (net of allowance for doubtful accounts of $2.1 as of December 31, 2017 and December 31, 2016)	90.5	83.3
Goodwill	455.1	455.1
Intangible assets (net of accumulated amortization of $136.1 and $110.7 as of December 31, 2017 and December 31, 2016, respectively)	203	150.2
Other assets	353.2	126.1
Total assets	4,312.1	2,852.4
Liabilities and equity
Accounts payable and accrued expenses	255.2	227.1
Deferred revenue	111.6	76.7
Capital lease obligations	10.1	10.8
Long-term debt, net	2,089.4	1,240.1
Lease financing arrangements	131.9	135.7
Total liabilities	2,598.2	1,690.4
Commitment and contingencies
Equity
Preferred stock, $.01 par value, 100,000,000 authorized; no shares issued or outstanding	0	0
Common stock, $.01 par value, 500,000,000 shares authorized and 96,137,874 and 83,536,250 shares issued and outstanding at December 31, 2017 and December 31, 2016, respectively	1	0.8
Additional paid in capital	2,125.6	1,412.3
Accumulated deficit	(486.9)	(249.8)
Accumulated other comprehensive income (loss)	74.2	(1.3)
Total stockholders’ equity	1,713.9	1,162
Total liabilities and equity	$ 4,312.1	$ 2,852.4

Consolidated Balance Sheets (Pa

Consolidated Balance Sheets (Parenthetical) - USD ($) $ in Millions	Dec. 31, 2017	Dec. 31, 2016
Statement of Financial Position [Abstract]
Allowance for doubtful accounts receivable	$ 2.1	$ 2.1
Accumulated amortization of intangible assets	$ 136.1	$ 110.7
Preferred stock par value (in dollars per share)	$ 0.01	$ 0.01
Preferred stock authorized (in shares)	100,000,000	100,000,000
Preferred stock issued (in shares)	0	0
Preferred stock outstanding (in shares)	0	0
Common stock par value (in dollars per share)	$ 0.01	$ 0.01
Common stock shares authorized (in shares)	500,000,000	500,000,000
Common stock issued (in shares)	96,137,874	83,536,250
Common stock outstanding (in shares)	96,137,874	83,536,250

Consolidated Statements of Oper

Consolidated Statements of Operations - USD ($) shares in Millions, $ in Millions	3 Months Ended								12 Months Ended
	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Revenue:
Base revenue and other									$ 602.4	$ 476.7	$ 354.6
Metered power reimbursements									69.6	52.4	44.7
Revenue									672	529.1	399.3
Costs and expenses:
Property operating expenses									235.1	187.5	148.7
Sales and marketing									17	16.9	12.1
General and administrative									67	60.7	46.6
Depreciation and amortization									258.9	183.9	141.5
Transaction and acquisition integration costs									10.4	4.3	14.1
Asset impairments and loss on disposal									59.5	5.3	13.5
Costs and expenses									647.9	458.6	376.5
Operating income	$ 23.9	$ (36.3)	$ 16.7	$ 19.8	$ 12.7	$ 18.8	$ 21.1	$ 17.9	24.1	70.5	22.8
Interest expense									68.1	48.8	41.2
Loss on extinguishment of debt									36.5	0	0
Net (loss) income before income taxes									(80.5)	21.7	(18.4)
Income tax expense									(3)	(1.8)	(1.8)
Net (loss) income	2.8	(55.1)	(0.8)	(30.4)	0.8	4.4	9.1	5.6	(83.5)	19.9	(20.2)
Noncontrolling interest in net loss									0	0	(4.8)
Net (loss) income attributed to common stockholders	$ 2.8	$ (55.1)	$ (0.8)	$ (30.4)	$ 0.8	$ 4.4	$ 9.1	$ 5.6	$ (83.5)	$ 19.9	$ (15.4)
Basic weighted average common shares outstanding (in shares)									88.9	78.3	54.3
Diluted weighted average common shares outstanding (in shares)									88.9	79	54.3
(Loss) Income per share - basic and diluted (in dollars per share)	$ 0.03	$ (0.61)	$ (0.01)	$ (0.36)	$ 0.01	$ 0.05	$ 0.11	$ 0.07	$ (0.95)	$ 0.24	$ (0.30)

Consolidated Statements of Comp

Consolidated Statements of Comprehensive Income (Loss) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Statement of Comprehensive Income [Abstract]
Net (loss) income	$ (83.5)	$ 19.9	$ (20.2)
Other comprehensive (loss) income:
Foreign currency translation adjustments	(0.1)	(0.9)	(0.2)
Unrealized gain on equity investment	75.6	0	0
Comprehensive (loss) income	(8)	19	(20.4)
Comprehensive loss attributable to noncontrolling interests	0	0	(4.8)
Comprehensive (loss) income attributable to CyrusOne Inc.	$ (8)	$ 19	$ (15.6)

Consolidated Statements of Equi

Consolidated Statements of Equity - USD ($) shares in Millions, $ in Millions	Total	Common Stock	Accumulated Deficit	Paid-In Capital	Accumulated Other Comprehensive Income (Loss)	Total Shareholders' Equity/ Parent’s Net Investment	Non-Controlling Interest
Beginning Balance (in shares) at Dec. 31, 2014		38.7
Beginning Balance at Dec. 31, 2014	$ 717	$ 0.4	$ (55.9)	$ 516.5	$ (0.2)	$ 460.8	$ 256.2
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net (loss) income	(20.2)		(20.2)			(20.2)
Noncontrolling interest in net loss	(4.8)		4.8			4.8	(4.8)
Stock issuance costs	(0.8)			(0.8)		(0.8)
Foreign currency translation adjustments	(0.2)				(0.2)	(0.2)
Stock-based compensation (in shares)		0.3
Stock-based compensation	14.4			14.4		14.4
Tax payment upon exercise of equity awards	(0.8)			(0.8)		(0.8)
Issuance of common stock (in shares)		33.6
Issuance of common stock	799.5	$ 0.3		799.2		799.5
Redemption of noncontrolling interest	(596.4)			(412.3)		(412.3)	(184.1)
Conversion of operating partnership units to common stock	0			51		51	(51)
Unrealized gain on equity investment	0
Dividends declared	(90.9)		(74.6)			(74.6)	(16.3)
Ending Balance (in shares) at Dec. 31, 2015		72.6
Ending Balance at Dec. 31, 2015	821.6	$ 0.7	(145.9)	967.2	(0.4)	821.6	0
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net (loss) income	19.9		19.9			19.9
Noncontrolling interest in net loss	0
Stock issuance costs	(1.6)			(1.6)		(1.6)
Foreign currency translation adjustments	(0.9)				(0.9)	(0.9)
Stock-based compensation (in shares)		0.6
Stock-based compensation	12.3			12.3		12.3
Tax payment upon exercise of equity awards (in shares)		(0.5)
Tax payment upon exercise of equity awards	(14.2)			(14.2)		(14.2)
Issuance of common stock (in shares)		10.8
Issuance of common stock	448.7	$ 0.1		448.6		448.7
Unrealized gain on equity investment	0
Dividends declared	(123.8)		(123.8)			(123.8)	0
Ending Balance (in shares) at Dec. 31, 2016		83.5
Ending Balance at Dec. 31, 2016	1,162	$ 0.8	(249.8)	1,412.3	(1.3)	1,162	0
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net (loss) income	(83.5)		(83.5)			(83.5)
Noncontrolling interest in net loss	0
Stock issuance costs	(0.3)			(0.3)		(0.3)
Foreign currency translation adjustments	(0.1)				(0.1)	(0.1)
Stock-based compensation (in shares)		(0.1)
Stock-based compensation	14.7			14.7		14.7
Tax payment upon exercise of equity awards (in shares)		(0.1)
Tax payment upon exercise of equity awards	(6.9)			(6.9)		(6.9)
Issuance of common stock (in shares)		12.8
Issuance of common stock	706	$ 0.2		705.8		706
Unrealized gain on equity investment	75.6				75.6	75.6
Dividends declared	(153.6)		(153.6)			(153.6)
Ending Balance (in shares) at Dec. 31, 2017		96.1
Ending Balance at Dec. 31, 2017	$ 1,713.9	$ 1	$ (486.9)	$ 2,125.6	$ 74.2	$ 1,713.9	$ 0

Consolidated Statements of Equ7

Consolidated Statements of Equity (Parenthetical) - $ / shares	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Statement of Stockholders' Equity [Abstract]
Dividends declared per share (in dollars per share)	$ 1.68	$ 1.52	$ 1.26

Consolidated Statements of Cash

Consolidated Statements of Cash Flows - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Cash flows from operating activities:
Net (loss) income	$ (83.5)	$ 19.9	$ (20.2)
Adjustments to reconcile net (loss) income to net cash provided by operating activities:
Depreciation and amortization	258.9	183.9	141.5
Provision for bad debt	0.2	1.6	0
Asset impairments and loss on disposal	59.5	5.3	13.5
Loss on extinguishment of debt	36.5	0	0
Non-cash interest expense and change in interest accrual	16.5	4.8	3.4
Stock-based compensation expense	14.7	12.3	14.4
Change in operating assets and liabilities:
Rent receivables and other assets	(64.3)	(51.7)	(23.9)
Accounts payable and accrued expenses	17	7	7
Deferred revenues	34	(2.5)	5.4
Due to affiliates	0	0	(0.9)
Net cash provided by operating activities	289.5	180.6	140.2
Cash flows from investing activities:
Capital expenditures – asset acquisitions, net of cash acquired	(492.3)	(131.1)	(17.3)
Capital expenditures – other development	(914.5)	(600)	(217.2)
Business acquisition, net of cash acquired	0	0	(389.6)
Equity investment	(100)	0	0
Net cash used in investing activities	(1,506.8)	(731.1)	(624.1)
Cash flows from financing activities:
Issuance of common stock	706	448.7	799.5
Stock issuance costs	(0.3)	(1.6)	(0.8)
Acquisition of operating partnership units	0	0	(596.4)
Dividends paid	(145.7)	(114.3)	(80.8)
Borrowings from credit facility	1,390	710	260
Payments on credit facility	(1,275)	(460)	(10)
Payments on senior notes	(474.8)	0	0
Proceeds from issuance of senior notes	1,217.8	0	103.8
Debt issuance costs	(19)	(8.7)	(5.4)
Payments on capital leases and lease financing arrangements	(9.8)	(9.1)	(5.9)
Payment of note payable	0	(1.5)	0
Interest paid by lenders on issuance of the senior notes	2.7	0	0
Payment of debt extinguishment costs	(30.4)	0	0
Tax payment upon exercise of equity awards	(6.9)	(14.2)	(0.8)
Net cash provided by financing activities	1,354.6	549.3	463.2
Net increase (decrease) in cash, cash equivalents and restricted cash	137.3	(1.2)	(20.7)
Cash, cash equivalents and restricted cash at beginning of period	14.6	15.8	36.5
Cash, cash equivalents and restricted cash at end of period	151.9	14.6	15.8
Supplemental disclosures
Cash paid for interest	68.8	55	43.7
Cash paid for income taxes	2.2	1.2	3.4
Capitalized interest	17	10.6	6.1
Non-cash investing and financing activities:
Acquisition and development of properties in accounts payable and other liabilities	115.5	132.7	59.2
Dividends payable	$ 41.8	$ 33.9	$ 23.6

Description of Business

Description of Business	12 Months Ended
	Dec. 31, 2017
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Description of Business	Description of Business CyrusOne Inc., together with CyrusOne GP, a wholly owned subsidiary of CyrusOne Inc., through which CyrusOne Inc. wholly owns CyrusOne LP (the operating partnership) and the subsidiaries of the operating partnership (collectively, “CyrusOne”, “we”, “us”, “our”, and the “Company”) owns, operates and develops enterprise-class, carrier-neutral, multi-tenant and single-tenant data center properties. Our customers operate in a number of industries, including information technology, financial services, energy, oil and gas, mining, medical and consumer goods and services. We currently operate 45 data centers and 2 recovery centers located in the United States, United Kingdom and Singapore.

Formation and Recent Developmen

Formation and Recent Developments	12 Months Ended
	Dec. 31, 2017
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Formation and Recent Developments	Formation and Recent Developments Formation On January 24, 2013 , CyrusOne Inc. completed its initial public offering (the IPO) of common stock. During 2014, 2015 and 2016, the Company completed public offerings of 16.0 million , 27.3 million , and 10.3 million shares of its common stock and received $355.9 million , $799.3 million and $419.8 million net proceeds, respectively, from these public offerings. On December 14, 2015, CyrusOne Inc. completed a public secondary offering of 1.4 million 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, CBI owned 9.5% of the common stock of CyrusOne Inc. As of December 31, 2017 and 2016, CBI owned less than 5.0% of the common stock of CyrusOne Inc. As of December 31, 2017 , all of the 96.1 million outstanding operating partnership units of CyrusOne LP are owned, directly or indirectly, by CyrusOne Inc. Recent Developments On February 27, 2017, the Company effected a full physical early settlement of the previously announced forward sale agreements (the Forward Sale Agreements) entered into with Goldman, Sachs & Co. on August 10, 2016 relating to, in the aggregate, approximately 4.4 million shares of the Company’s common stock. Upon settlement, the Company issued and sold all such shares to Goldman, Sachs & Co., in its capacity as forward purchaser, in exchange for net proceeds of approximately $210.8 million , in accordance with the provisions of the Forward Sales Agreements. Such proceeds were used to finance, in part, the acquisition of the Sentinel Properties (as defined below). On February 28, 2017 , CyrusOne closed its acquisition of two data centers located in Somerset, New Jersey and Raleigh-Durham, North Carolina (the Sentinel Properties) from Sentinel Data Centers. The Company paid aggregate cash consideration of approximately $492.3 million in connection therewith, including transaction related costs of $1.5 million . The transaction was financed by the Company with proceeds from settlement of its forward equity sale described above and borrowings under its Revolving Credit Facility (as defined in Note 10). On March 17, 2017, CyrusOne LP and CyrusOne Finance Corp. completed their offering of $500.0 million aggregate principal amount of 5.000% senior notes due 2024 (the Original 2024 Notes) and $300.0 million aggregate principal amount of 5.375% senior notes due 2027 (the Original 2027 Notes) in a private offering. The Company received proceeds of $791.2 million , net of underwriting costs of $8.8 million . The Company used the net proceeds from the offering (i) to finance its repurchase and redemption of all of its outstanding 6.375% Senior Notes due 2022 (the 2022 Notes), of which $474.8 million in aggregate principal amount was outstanding, (ii) for the repayment of borrowings outstanding under the operating partnership’s Revolving Credit Facility and (iii) for the payment of related premiums, fees, discounts and expenses. On June 16, 2017, CyrusOne LP entered into an amendment to its senior Second Amended and Restated Credit Agreement (as defined in Note 10) that increased the total commitments thereunder by $450.0 million to $2.0 billion and provided additional flexibility to pursue various initiatives, including joint ventures and international expansion. The amendment increased the size of the term loan maturing in January 2022 from $300.0 million to $650.0 million and expanded the Revolving Credit Facility (as defined in Note 10) by $100.0 million to $1.1 billion . Proceeds from the $350.0 million term loan increase were used to pay down borrowings under the Revolving Credit Facility. The existing $250.0 million term loan maturing in September 2021 remained unchanged. The amendment refreshes the amount available under the accordion feature of the Second Amended and Restated Credit Agreement to enable CyrusOne LP to increase the total loan commitments under the Second Amended and Restated Credit Agreement to up to $2.3 billion from time to time. On October 18, 2017, CyrusOne announced the formation of a new strategic partnership with the execution of a commercial agreement with GDS Holdings Limited (GDS), a leading developer and operator of high-performance, large-scale data centers in China. Under this new partnership, CyrusOne and GDS will work together to market and cross-sell data center space and related services in both the United States and China. In addition, CyrusOne purchased newly issued unregistered ordinary shares equivalent to 8.0 million American depository shares (ADS) of GDS at a price per ordinary share equivalent to $12.45 per ADS, a 4% discount to the October 17, 2017 closing price, for a total investment of $100 million . Each ADS is equivalent to eight ordinary GDS shares. CyrusOne President and Chief Executive Officer Gary Wojtaszek will join the GDS Board of Directors. On November 3, 2017, CyrusOne LP and CyrusOne Finance Corp. completed their offering of $200.0 million aggregate principal amount of 5.000% senior notes due 2024 (the Additional 2024 Notes) and $200.0 million aggregate principal amount of 5.375% senior notes due 2027 (the Additional 2027 Notes) in a private offering. The Additional 2024 Notes have terms substantially identical to the Original 2024 Notes and the Additional 2027 Notes have terms substantially identical to the Original 2027 Notes. The Original 2024 Notes and the Additional 2024 Notes form a single class of securities, and the Original 2027 Notes and the Additional 2027 Notes form a single class of securities. The Company received proceeds of $416.1 million , net of underwriting costs of $4.4 million . The Original 2024 Notes and the Additional 2024 Notes are referred to as the 2024 Notes and the Original 2027 Notes and the Additional 2027 Notes are referred to as the 2027 Notes. During the third quarter of 2017, the Board authorized the Company to enter into sales agreements pursuant to which the Company may issue and sell from time to time shares of its common stock having an aggregate sales price of up to $500 million (the 2017 At The Market (ATM) Stock Offering Program). The 2017 ATM Stock Offering program replaces a prior ATM stock offering program. For the year ended December 31, 2017 , the Company sold approximately 8.4 million shares of its common stock under the ATM stock offering programs, generating net proceeds of approximately $493.7 million , net of sales commissions of $6.3 million . On December 21, 2017, CyrusOne announced the execution of a definitive agreement with Quantum Strategic Partners Ltd. (Quantum), a private investment fund managed by Soros Fund Management LLC and certain other sellers named therein, to purchase Zenium Data Centers (Zenium), a leading hyperscale data center provider in Europe with four properties in London and Frankfurt, the continent’s two largest data center markets. The purchase price is expected to be approximately $442.0 million , excluding transaction-related expenses. CyrusOne has also agreed to reimburse Zenium for capital expenditures between signing and closing. The transaction is expected to close in the first half of 2018, subject to the fulfillment of customary closing conditions including applicable regulatory approvals. In connection with the issuance of the 2024 Notes and the 2027 Notes, CyrusOne LP and CyrusOne Finance Corp. agreed to use commercially reasonable efforts to file and cause to become effective a registration statement to be used in connection with the exchange of 2024 Notes and 2027 Notes for freely tradeable notes with substantially identical terms in all material respects to the 2024 Notes and 2027 Notes, and to complete an exchange offer. In January 2018, upon completion of the exchange offer, all validly tendered 2024 Notes and 2027 Notes were exchanged for notes that are registered with the Securities and Exchange Commission (SEC) and are freely tradeable. Our total stock issuance for the year ended December 31, 2017 was $706.0 million which included $210.8 million under the forward sales agreements, $493.7 million under the ATM stock offering program and $1.5 million related to the employee stock purchase plans and stock options exercised.

Basis of Presentation

Basis of Presentation	12 Months Ended
	Dec. 31, 2017
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Basis of Presentation	Basis of Presentation The accompanying financial statements as of December 31, 2017 and December 31, 2016 , and for the years ended December 31, 2017 , December 31, 2016 and December 31, 2015 , are prepared on a consolidated basis. In addition, the accompanying financial statements have been prepared in accordance with accounting principles generally accepted in the United States of America (GAAP). All intercompany transactions and balances have been eliminated in consolidation. All prior year amounts have been presented to conform to current year's presentation. Base revenue and other, and metered power reimbursements for the years ended December 31, 2016 and 2015 have been presented separately to conform with the presentation for the year ended December 31, 2017. There is no change to total revenue as a result of this change in presentation. We adopted ASU No. 2016-18, Restricted Cash, during 2017 (See Note 5 for additional details). The statement of cash flows for prior periods has been presented to conform to the current year's presentation.

Significant Accounting Policies

Significant Accounting Policies	12 Months Ended
	Dec. 31, 2017
Accounting Policies [Abstract]
Significant Accounting Policies	Significant Accounting Policies Use of Estimates —Preparation of the consolidated financial statements in conformity with GAAP requires management to make estimates and assumptions that affect the amounts reported in the consolidated financial statements and accompanying notes. These estimates and assumptions are based on management’s knowledge of current events and actions that we may undertake in the future. Estimates are used in determining the fair value of leased real estate, including purchase price allocations for business combinations and asset acquisitions, the useful lives of real estate and other long-lived assets, future cash flows associated with goodwill and other long-lived asset impairment testing, deferred tax assets and liabilities, available-for-sale securities and loss contingencies. Actual results may differ from these estimates and assumptions. Investment in Real Estate —Investment in real estate consist of land, buildings, improvements and integral equipment utilized in our data center operations. Real estate acquired from third parties has been recorded at its acquisition cost. Additions and improvements which extend an asset’s useful life or increase its functionality are capitalized and depreciated over the asset’s remaining life. Maintenance and repairs are expensed as incurred. When we are involved in the construction of structural improvements to leased property, we are deemed the accounting owner of the leased real estate. In these instances, we bear substantially all the construction period risk, including managing or funding construction. As we have substantially all of the construction risks, we are deemed the “owner” of the asset under construction for accounting purposes during the construction period, and are therefore required to capitalize the construction costs on the accompanying consolidated balance sheets. At inception, the fair value of the building, excluding land, is recorded as an asset, and the construction and modification costs to the building that are not funded by us would be recorded as a liability. As construction progresses, the value of the asset and obligation increases by the fair value of the structural improvements. At completion of the construction, Sales-Leaseback Accounting under ASC 840-40-25 is also evaluated. Due to our continuing involvement with the lessor, Sales-Leaseback Accounting is precluded and the liability is not derecognized. When the asset is placed in service, depreciation commences, and the leased real estate is depreciated to the lesser of (i) its estimated fair value at the end of the term or (ii) the expected amount of the unamortized obligation at the end of the term. The associated obligation is presented as Lease financing arrangements in the accompanying consolidated balance sheets. When we are not deemed the accounting owner of leased real estate, we further evaluate the lease to determine whether the lease should be classified as a capital or operating lease. One of the following four characteristics must be present to classify a lease as a capital lease: (i) the lease transfers ownership of the property to the lessee by the end of the lease term, (ii) the lease contains a bargain purchase option, (iii) the lease term is equal to 75% or more of the estimated economic life of the leased property or (iv) the net present value of the lease payments is at least 90% of the fair value of the leased property. Construction in progress includes direct and indirect expenditures for the construction and expansion of our data centers and is stated at its acquisition cost. Independent contractors perform substantially all of the construction and expansion efforts of our data centers. Construction in progress includes costs incurred under construction contracts including project management services, engineering and schematic design services, design development, construction services and other construction-related fees and services. Interest, property taxes and certain labor costs are also capitalized during the construction of an asset. These costs are depreciated over the estimated useful life of the related assets. Capitalized interest in 2017 , 2016 , and 2015 was $17.0 million , $10.6 million , and $6.1 million , respectively. Depreciation is calculated using the straight-line method over the estimated useful life of the asset. Useful lives range from nine to thirty years for buildings, three to thirty years for building improvements, and two to twenty years for equipment. Leasehold improvements are amortized over the shorter of the asset’s useful life or the remaining lease term, including renewal options which are reasonably assured. Management reviews the carrying value of long-lived assets, including intangible assets with finite lives, when events or changes in circumstances indicate that the carrying amount of the assets may not be recoverable. Examples of such indicators may include a significant adverse change in the extent to which or manner in which the property is being used, an accumulation of costs significantly in excess of the amount originally expected for acquisition or development, or a history of operating or cash flow losses. When such indicators exist, we review an estimate of the undiscounted future cash flows expected to result from the use of an asset (or group of assets) and its eventual disposition and compare such amount to its carrying amount. We consider factors such as future operating income, leasing demand, competition and other factors. If our undiscounted net cash flows indicate that we are unable to recover the carrying value of the asset, an impairment loss is recognized. An impairment loss is measured as the amount by which the asset’s carrying value exceeds its estimated fair value. Business Combinations and Asset Acquisitions —The Company applies the purchase method for business combinations, where all tangible and identifiable intangible assets acquired and all liabilities assumed are recorded at fair value. Any excess purchase price is recorded as goodwill. Transaction costs associated with business combinations are expensed as incurred. Revenues and the results of operations of the acquired business are included in the accompanying consolidated financial statements commencing on the date of acquisition. The Company applies a screen test to determine when a set is not a business. When substantially all of the fair value of the gross assets acquired (or disposed of) is concentrated in a single identifiable asset or a group of similar identifiable assets, the set is not a business. Upon adoption of ASU 2017-01, Business Combinations, most acquisitions of investment properties will meet the definition of an asset. Purchase price paid for assets acquired is allocated between identified tangible and intangible assets acquired. Transaction costs associated with asset acquisitions are capitalized. Revenues and the results of operations of the acquired assets are included in the accompanying consolidated financial statements commencing on the date of the asset acquisition. The Company early adopted ASU 2017-01, Business Combinations, on January 1, 2017. Cash and Cash Equivalents —Cash and cash equivalents include all non-restricted cash held in financial institutions and other non-restricted highly liquid short-term investments with original maturities at acquisition of three months or less. Restricted Cash —Restricted cash includes cash equivalents held to collateralize standby letters of credit and/or deposited in escrow to fund construction or pending potential acquisition transactions. In addition, we may have other cash that is not immediately available for use in current operations. Goodwill —We evaluate goodwill for possible impairment at least annually or upon the occurrence of a triggering event. A triggering event is an event or circumstance that would more likely than not reduce the fair value of a reporting unit below its carrying amount, including sales of properties defined as businesses for which the relative size of the sold property is significant to the reporting unit, that could impact our goodwill impairment calculations. For our annual impairment evaluation, we have the option of performing a qualitative or quantitative goodwill impairment analysis. A qualitative analysis, Step zero, analyzes the macro-economic environment in which we operate for any significant changes such as deterioration in the market that the Company operates or overall financial performance such as declining cash flows. Also, entity specific changes are analyzed such as change in management, strategy or composition of reporting unit. A quantitative analysis, Step one, requires the Company to estimate the fair value of the reporting unit and compare the fair value to the carrying value to identify whether the value of the recorded goodwill is impaired. Changes in certain assumptions could have a significant impact on the impairment test for goodwill under Step one. The most critical assumptions are projected future growth rates, operating margins, capital expenditures, tax rates, terminal values and discount rates. These assumptions are subject to change as our long-term plans and strategies are updated each year. In January 2017, the FASB issued ASU 2017-04 in order to simplify the test for goodwill impairment by eliminating Step 2, which measures a goodwill impairment loss by comparing the implied fair value of a reporting unit's goodwill with the carrying amount of that goodwill. Under the amendments in this update, an entity should perform its annual goodwill impairment test by comparing the fair value of a reporting unit with its carrying amount and should recognize an impairment charge for the amount by which the carrying amount exceeds the reporting unit's fair value. However, the loss recognized should not exceed the total amount of goodwill allocated to that reporting unit. Early adoption is permitted. We adopted this standard on January 1, 2017. During the fourth quarter of 2017 and 2016, we applied Step zero and determined that it is more likely than not that the fair value of the reporting unit is more than the carrying amount and therefore determined that the two step method for goodwill impairment testing was not necessary. During the fourth quarter of 2015, we performed a detailed, quantitative assessment. Based on the Company's annual assessment of goodwill, no impairment has been recognized through December 31, 2017. Long-Lived and Intangible Assets —Intangible assets represent purchased assets that lack physical substance, but can be separately distinguished from goodwill because of contractual or other legal rights or because the asset is capable of being sold or exchanged, either on its own or in combination with a related contract, asset, or liability. Intangible assets with finite lives consist of trademarks, a trade name, customer relationships, and a favorable leasehold interest. Rent and Other Receivables —Receivables consist principally of trade receivables from customers and are generally unsecured and due within 30 to 120 days . Unbilled receivables arise from services rendered but not yet billed. Expected credit losses associated with trade receivables are recorded as an allowance for doubtful accounts. The allowance for doubtful accounts is estimated based upon historic patterns of credit losses for aged receivables as well as specific provisions for certain identifiable, potentially uncollectible balances. When internal collection efforts on accounts have been exhausted, the accounts are written-off and the associated allowance for doubtful accounts is reduced. At December 31, 2017 and 2016, there were no customers with receivables that made up 10% or more of the Company's Rent and other receivables balance. Deferred Leasing Costs —Deferred leasing costs are presented with Other assets in the accompanying consolidated balance sheets. Leasing commissions incurred at the commencement of a new lease are capitalized and amortized over the average term of the customer lease. Amortization of deferred leasing costs is presented with Depreciation and amortization in the accompanying consolidated statements of operations. If a lease terminates prior to the expiration of the lease, the remaining unamortized cost is written off to amortization expense. As of December 31, 2017 and 2016 , deferred leasing costs were $32.6 million and $23.3 million , respectively. Amortization expense was $7.6 million , $6.1 million and $5.2 million for the years ended December 31, 2017 , 2016 and 2015 , respectively. Deferred Financing Costs —Deferred financing costs include costs incurred in connection with issuance of debt, including our senior notes, term loans and revolving credit facilities. These costs are presented in the balance sheet as a direct reduction from the carrying amount of the debt liability. These financing costs are deferred and amortized to expense over the term of the instrument and are included as a component of Interest expense. Lease Financing Arrangements —Lease financing arrangements represent leases of real estate where we are involved in the construction of structural improvements to develop buildings into data centers. When we bear substantially all the construction period risk, such as managing or funding construction, we are deemed to be the accounting owner of the leased property and, at the lease inception date, we are required to record at fair value the property and associated liability on our consolidated balance sheets. These transactions generally do not qualify for sale-leaseback accounting due to our continued involvement in these data center operations. Revenue Recognition —Colocation rentals are generally billed monthly in advance, and some contracts have escalating payments over the term of the contract. If rents escalate without the lessee gaining access to or control over additional leased space or power, and the lessee takes possession of, or controls the physical use of the property (including all contractually committed power) at the beginning of the lease term, the rental payments by the lessee are recognized as revenue on a straight-line basis over the term of the lease. If rents escalate because the lessee gains access to and control over additional leased space or power, revenue is recognized in proportion to the additional space or power in the periods that the lessee has control over the use of the additional space or power. The excess of revenue recognized over amounts contractually due is recognized in Other assets in the accompanying consolidated balance sheets. As of December 31, 2017 and 2016 , straight-line rent receivable was $100.0 million and $67.6 million , respectively. Revenue is recognized for services or products that are deemed separate units of accounting. When a customer makes an advance payment or they are contractually obligated to pay any amounts in advance, which is not deemed a separate unit of accounting, Deferred revenue liability is recorded. This revenue is recognized ratably over the expected term of the lease, unless the pattern of service suggests otherwise. As of December 31, 2017 and 2016 , Deferred revenue was $111.6 million and $76.7 million , respectively. Some of our leases are structured on a full-service gross basis in which the customer pays a fixed amount for both colocation rent and power. Other leases provide that the customer will be billed for power based upon actual usage which is separately metered. Power is generally billed one month in arrears, and an estimate of this revenue is accrued in the month that the associated costs are incurred. In certain leases, we receive an administrative fee when we manage the meters for our customers. We generally are not entitled to reimbursements for real estate taxes, insurance or other operating expenses. Certain customer leases require specified levels of service or performance. If we fail to meet these service levels, our customers may be eligible to receive credits on their contractual billings. These credits are recognized against revenue when an event occurs that gives rise to such credits. Customer credits were immaterial for each of the years presented. A provision for doubtful accounts is recognized when the collection of contractual rent, straight-line rent or customer reimbursements are deemed to be uncollectible. Sales and Marketing Expense —Sales and marketing expense is comprised of compensation and benefits associated with Sales and marketing personnel as well as advertising and marketing costs. Costs related to advertising expense were $2.4 million , $4.1 million and $2.2 million for the years ended December 31, 2017 , 2016 and 2015 , respectively. Depreciation and Amortization Expense —Depreciation expense is recognized over the estimated useful lives of real estate applying the straight-line method. The useful life of leased real estate and leasehold improvements is the lesser of the economic useful life of the asset or the term of the lease, including optional renewal periods if renewal of the lease is reasonably assured. The residual value of leased real estate is estimated as the lesser of (i) the expected fair value of the asset at the end of the lease term or (ii) the expected amount of the unamortized liability at the end of the lease term. Estimated useful lives are periodically reviewed. Depreciation expense was $226.2 million , $157.7 million and $117.8 million for the years ended December 31, 2017 , 2016 and 2015 , respectively. Amortization expense is recognized over the estimated useful lives of finite-lived intangibles. Finite-lived intangibles include trademarks, customer relationships, favorable leasehold interests, in-place leases, trade names and deferred leasing costs. See Note 9, Goodwill, Intangible and Other Long-Lived Assets, for details. Transaction and Acquisition Integration Costs —Transaction costs represent incremental legal, accounting and professional fees incurred in connection with consummated business combinations; integration costs post an asset acquisition; and costs associated with diligence efforts on certain targeted and unrealized acquisitions. Integration costs represent incremental costs to integrate a consummated acquisition. These costs are expensed as incurred and do not include any recurring costs from our ongoing operations. Income Taxes —The income tax provision consists of an amount for taxes currently payable and an amount for tax consequences deferred to future periods. CyrusOne Inc. has elected to be taxed as a REIT under the Internal Revenue Code of 1986, as amended (the Code), commencing with our initial taxable year ending December 31, 2013. Provided we continue to meet the various qualification tests mandated under the Code, we are generally not subject to corporate level federal income tax on the earnings distributed currently to our stockholders. If we fail to qualify as a REIT in any taxable year, our taxable income will be subject to federal income tax at regular corporate rates and, for taxable years beginning prior to January 1, 2018, any applicable alternative minimum tax, and we may not be able to qualify as a REIT for four subsequent taxable years. While CyrusOne Inc. and the operating partnership do not pay federal income taxes, we are still subject to foreign, state and local income taxes in the locations in which we conduct business. Our taxable REIT subsidiaries (each a TRS) are also subject to federal and state income taxes to the extent they earn taxable income. Deferred income taxes are recognized in certain entities. Deferred income taxes are provided for temporary differences in the basis between financial statement and income tax assets and liabilities. Deferred income taxes are recalculated annually at rates then in effect. Valuation allowances are recorded to reduce deferred tax assets to amounts that are more likely than not to be realized. The ultimate realization of the deferred tax assets depends upon our ability to generate future taxable income during the periods in which basis differences and other deductions become deductible and prior to the expiration of the net operating loss carryforwards. The Company and its subsidiaries file income tax returns in the U.S. federal jurisdiction as well as various foreign, state and local jurisdictions. The Company's previous tax filings are subject to normal reviews by regulatory agencies until the related statute of limitations expires. With a few exceptions, the Company is no longer subject to U. S. federal, state or local examinations for years prior to 2012, and we have no liabilities for uncertain tax positions as of December 31, 2017 or 2016 . Foreign Currency Translation and Transactions —The financial position of foreign subsidiaries is translated at the exchange rates in effect at the end of the period, while revenues and expenses are translated at average rates of exchange during the period. Gains or losses from translation of foreign operations where the local currency is the functional currency are included as components of other comprehensive (loss) income. Gains or losses from foreign currency transactions are included in determining net (loss) income. Comprehensive (Loss) Income —Comprehensive (loss) income represents the change in net assets of a company from transactions and other events from nonowner sources. Comprehensive (loss) income comprises all components of net (loss) income and all components of other comprehensive (loss) income. (Loss)/Income Per Share —Basic EPS includes only the weighted average number of common shares outstanding during the period. Diluted EPS includes the weighted average number of common shares and the dilutive effect of stock options, restricted stock and share unit awards outstanding during the period, when such instruments are dilutive. All outstanding unvested share-based payment awards that contain rights to nonforfeitable dividends are treated as participating in undistributed earnings with common shareholders. Awards of this nature are considered participating securities and the two-class method of computing basic and diluted EPS is applied. Stock-Based Compensation —Our board of directors adopted the 2012 Long-Term Incentive Plan (LTIP), which was amended and restated by our stockholders on May 2, 2016. The LTIP is administered by the compensation committee of the board of directors. Awards issuable under the LTIP include common stock, restricted stock, restricted stock units, stock options and other incentive awards. See Note 17 for additional details relating to these awards. Share-based compensation expense is based on the estimated grant-date fair value. CyrusOne Inc. recognizes share-based compensation expense on a straight-line basis over the requisite service period for time-based awards and on a graded vesting basis for performance-based awards. We adopted ASU No. 2016-09, Improvements to Employee Share-Based Payment Accounting (Subtopic 718) in the fourth quarter of 2016 and elected to account for forfeitures as they occur. Prior to the adoption of this ASU, CyrusOne estimated forfeitures based on historical activity, expected employee turnover, and other qualitative factors which were adjusted for changes in estimates and award vesting. CyrusOne Inc. uses the Black-Scholes-Merton option pricing model to calculate the fair value of stock options. This option valuation model requires the use of subjective assumptions, including the estimated fair value of the underlying common stock, the expected stock price volatility, and the expected term of the option. The estimated fair value of the underlying common stock is based on third-party valuations. Our volatility estimates are based on a peer group of companies. We estimate the expected term of the awards to be the weighted average mid-point between the vesting date and the end of the contractual term. For interim and annual periods, we use our year-to-date actual results, financial forecasts, and other available information to estimate the probability of the award vesting based on the performance metrics. Fair Value Measurements —Fair value measurements are utilized in accounting for business combinations, testing of goodwill and other long-lived assets for impairment, recording unrealized gain/loss on available-for-sale securities and disclosures. Fair value of financial and non-financial assets and liabilities is defined as an exit price, representing the amount that would be received to sell an asset or paid to transfer a liability in an orderly transaction between market participants. The three-tier hierarchy for inputs used in measuring fair value, which prioritizes the inputs used in the methodologies of measuring fair value for asset and liabilities, is as follows: Level 1—Observable inputs for identical instruments such as quoted market prices; Level 2—Inputs include quoted prices for similar assets and liabilities in active markets, quoted prices for identical or similar assets or liabilities in markets that are not active, inputs other than quoted prices that are observable for the asset or liability (i.e., interest rates, yield curves, etc.), and inputs that are derived principally from or corroborated by observable market data by correlation or other means (market corroborated inputs); and Level 3—Unobservable inputs that reflect our determination of assumptions that market participants would use in pricing the asset or liability. These inputs are developed based on the best information available, including our own data. Business Segments —Business segments are components of an enterprise for which separate financial information is available and regularly viewed by the chief operating decision maker to assess performance and allocate resources. Our chief operating decision maker, the Company's Chief Executive Officer, reviews our financial information on an aggregate basis. Furthermore, our data centers have similar economic characteristics and customers across all geographic locations, and our service offerings have similar production processes, deliver services in a similar manner and use the same types of facilities and similar technologies. As a result, we have concluded that we have one reportable business segment. For the year ended December 31, 2017 , one customer, Microsoft Corporation, represented approximately 18% of our revenue.

Recently Issued Accounting Stan

Recently Issued Accounting Standards	12 Months Ended
	Dec. 31, 2017
Accounting Changes and Error Corrections [Abstract]
Recently Issued Accounting Standards	Recently Issued Accounting Standards Accounting Standards Update (ASU) No. 2014-09 (ASU 2014-09), Revenue from Contracts with Customers (Topic 606), as amended. On May 28, 2014, the Financial Accounting Standards Board (FASB) issued ASU 2014-09, which supersedes the revenue recognition requirements in Topic 605, "Revenue Recognition" and most industry-specific guidance. The core principle of ASU 2014-09 is that a company will recognize revenue when it transfers promised goods or services to customers in an amount that reflects the consideration to which the company expects to be entitled in exchange for those goods or services. On July 9, 2015, the FASB deferred the effective date of ASU 2014-09. The new revenue standard is effective for fiscal years, and interim periods within those years, beginning after December 15, 2017 (January 1, 2018 for CyrusOne) and allows either a full retrospective adoption to all periods presented or a modified retrospective adoption approach with the cumulative effect of initial application of the revised guidance recognized at the date of initial application. We are continuing to evaluate the impact of ASU 2014-09 on our consolidated financial statements. We have identified each of our revenue streams and developed views of how they will be impacted by this adoption. Our evaluation is that the timing of revenue recognition for our various revenue streams would not be materially impacted by the adoption of this standard. As we continue our assessment we are reviewing, in detail, selected revenue contracts to verify and support our initial conclusions. We will adopt the modified retrospective approach with any cumulative effect recognized in retained earnings on the date of adoption which is expected to be immaterial. We will be adopting this Standard with an effective date of January 1, 2018. ASU No. 2016-01 (ASU 2016-01), Financial Instruments - Overall (Topic 825-10) On January 5, 2016, the FASB issued ASU 2016-01. Equity investments (except those accounted for under the equity method of accounting or those that result in consolidation of the investee) are to be measured at fair value with changes in fair value recognized in net income. However, an entity may choose to measure equity investments that do not have readily determinable fair values at cost minus impairment, if any, plus or minus changes resulting from observable price changes in orderly transactions for the identical or a similar investment of the same issuer. Equity investments without readily determinable fair values are to be assessed for impairment using a quantitative approach. ASU 2016-01 should be applied by means of a cumulative-effect adjustment to the balance sheet as of the beginning of the fiscal year of adoption. The guidance is effective for annual periods beginning after December 15, 2017. The adoption of 2016-01 could have a material impact for our financial statements. In 2017 we recorded an increase to the value of our equity method investment due to an unrealized gain of $75.6 million which is recorded in Accumulated other comprehensive income (loss) in the consolidated balance sheets. ASU No. 2016-02 (ASU 2016-02), Leases (Topic 842) On February 25, 2016, the FASB issued ASU 2016-02. Lessees will need to recognize on their balance sheet a right-of-use asset and a lease liability for virtually all of their leases (other than leases that meet the definition of a short-term lease). The liability will be equal to the present value of lease payments. The asset will be based on the liability, adjusted for any initial direct costs of the lease, lease incentives or early lease payments, where applicable. For income statement purposes, the FASB retained a dual model, requiring leases to be classified as either operating or finance. Operating leases will result in straight-line expense (similar to current operating leases) while finance leases will result in a front-loaded expense pattern (similar to current capital leases). Classification will be based on criteria that are largely similar to those applied in current lease accounting. The standard is effective for CyrusOne beginning January 1, 2019. Early adoption is permitted. The new standard must be adopted using a modified retrospective transition, and provides for certain practical expedients. Transition will require application of the new guidance at the beginning of the earliest comparative period presented. We are beginning to evaluate the impact of ASU 2016-02 on our consolidated financial statements and plan to adopt the standard on January 1, 2019. ASU 2016-02 originally stated that companies would be required to bifurcate certain lease revenues between lease and non-lease components, however, the FASB issued an exposure draft in January 2018 (2018 Exposure Draft) which, if adopted as written, would allow lessors a practical expedient by class of underlying assets to account for lease and non-lease components as a single lease component if certain criteria are met. Additionally, only incremental direct leasing costs may be capitalized under this new guidance, which is consistent with the Company’s existing policies. ASU 2016-02 originally required a modified retrospective method of adoption, however, the 2018 Exposure Draft indicates that companies may be permitted to recognize a cumulative-effect adjustment to the opening balance of retained earnings in the period of adoption. The pronouncement allows some optional practical expedients. The Company expects to adopt this new guidance on January 1, 2019 and will continue to evaluate the impact of this guidance until it becomes effective. ASU No. 2016-13 (ASU 2016-13), Measurement of Credit Losses on Financial Instruments (Subtopic 326) In June 2016, the FASB issued guidance which requires a financial asset measured at amortized cost basis to be presented at the net amount expected to be collected. The amendments affect entities holding financial assets and net investment in leases that are not accounted for at fair value through net income. The amendments affect loans, debt securities, trade receivables, net investments in leases, off-balance-sheet credit exposures, reinsurance receivables, and any other financial assets not excluded from the scope that have the contractual right to receive cash. The guidance is effective for annual periods beginning after December 15, 2019. Early adoption is permitted. We are currently evaluating the full impact of the new standard. ASU No. 2016-18 (ASU 2016-18), Restricted Cash (Subtopic 230) In November 2016, the FASB issued guidance which addresses the diversity in the classification and presentation of changes in restricted cash on the statement of cash flows. The amendment requires that a statement of cash flows explain the change during the period in total cash, cash equivalents, and amounts generally described as restricted cash or restricted cash equivalents. The guidance is effective for annual periods beginning after December 15, 2017. Early adoption is permitted. We adopted ASU 2016-18 in the fourth quarter of 2017 with retrospective adoption to all periods presented. Accordingly, restricted cash balances are included along with cash and cash equivalents at the end of the period and beginning of the period in our consolidated statements of cash flows for all periods presented. Line items showing changes in restricted cash balances have been eliminated from our consolidated statements of cash flows. The following table provides a reconciliation of cash, cash equivalents and restricted cash reported within the statement of financial position that sum to the total of the same such amounts shown in our statements of cash flows for the years ended December 31, 2017, 2016, and 2015 (in millions): Year Ended December 31, 2017 2016 2015 Cash and cash equivalents $ 151.9 $ 14.6 $ 14.3 Restricted cash — — 1.5 Total cash, cash equivalents, and restricted cash shown in the statement of cash flows $ 151.9 $ 14.6 $ 15.8 The balance of total cash, cash equivalents and restricted cash as of January 1, 2015, was $36.5 million . ASU No. 2017-01 (ASU 2017-01), Business Combinations (Topic 805) In January 2017, the FASB issued guidance which clarifies the definition of a business with the objective of adding guidance to assist entities with evaluating whether transactions should be accounted for as acquisitions (or disposals) of assets or businesses. The definition of a business affects many areas of accounting including acquisitions, disposals, goodwill and consolidation. Under this new guidance, the Company expects most acquisitions of investment property will meet the definition of an asset and, thus, be accounted for as asset acquisitions. Consistent with existing guidance, transaction costs associated with asset acquisitions are capitalized while transaction costs associated with business combinations are expensed as incurred. The guidance is effective for annual periods beginning after December 15, 2017. Early adoption is permitted. We adopted this standard on January 1, 2017, and applied the new guidance for the acquisition of the Sentinel Properties. ASU No. 2017-04 (ASU 2017-04), Goodwill and Other (Topic 350) In January 2017, the FASB issued ASU 2017-04 in order to simplify the test for goodwill impairment by eliminating Step 2, which measures a goodwill impairment loss by comparing the implied fair value of a reporting unit's goodwill with the carrying amount of that goodwill. Under the amendments in this Update, an entity should perform its annual goodwill impairment test by comparing the fair value of a reporting unit with its carrying amount and should recognize an impairment charge for the amount by which the carrying amount exceeds the reporting unit's fair value. However, the loss recognized should not exceed the total amount of goodwill allocated to that reporting unit. The guidance is effective for CyrusOne beginning on January 1, 2020 and early adoption is permitted for interim or annual goodwill impairment tests performed on testing dates after January 1, 2017. We adopted this standard on January 1, 2017. The adoption of this standard did not have any impact on our consolidated financial statements. ASU No. 2017-05 (ASU 2017-05), Other Income—Gains and Losses from the Derecognition of Nonfinancial Assets (Subtopic 610-20)—Clarifying the Scope of Asset Derecognition Guidance and Accounting for Partial Sales of Nonfinancial Assets In February 2017, the FASB issued ASU 2017-05, Other Income – Gains and Losses from the Derecognition of Nonfinancial Assets (Topic 610-20), which requires that all entities account for the derecognition of a business in accordance with ASC 810, Consolidations, including instances in which the business is considered in substance real estate. The ASU is effective for annual periods, and interim periods therein, beginning after December 15, 2017. Early application is permitted. We are currently evaluating the full impact of the new standard.

Acquisitions and Purchase of Fi

Acquisitions and Purchase of Fixed Assets	12 Months Ended
	Dec. 31, 2017
Business Combinations [Abstract]
Acquisitions and Purchase of Fixed Assets	Acquisitions and Purchase of Fixed Assets Asset Acquisitions On February 28, 2017 , CyrusOne acquired two data centers located in Raleigh-Durham, North Carolina and Somerset, New Jersey from Sentinel Data Centers. This transaction provided enhanced geographic diversification, established a presence in the Southeast and expanded the Company's footprint in the Northeast. The two properties consist of more than 160,000 colocation square feet and approximately 21 megawatts of power capacity, with nearly 85% of the power capacity leased. The Company applied ASU No. 2017-01, Business Combinations, to this acquisition and determined that substantially all of the fair value of the gross assets was concentrated in a group of similar identifiable assets. The Company did not acquire an organized workforce or a contract that provided access to an organized workforce. As a result, the Company determined to account for the transaction as an acquisition of assets. The consolidated financial statements of CyrusOne Inc. include the operating results of the Sentinel Properties from February 28, 2017, the date of acquisition. The following table summarizes the estimated fair values of all assets acquired at the date of acquisition: IN MILLIONS Net investment in real estate $ 420.3 Cash and cash equivalents 3.2 Intangible assets: Above/Below market leases 2.3 In-place leases 75.8 Other assets 2.4 Payables (5.4 ) Deferred revenue (0.9 ) Capital lease obligation (2.2 ) Net assets acquired attributable to CyrusOne Inc. 495.5 Cash acquired (3.2 ) Net cash paid at acquisition $ 492.3 In December 2017, CyrusOne purchased a 44 acre site outside of Atlanta, Georgia. In July of 2017, CyrusOne purchased 66 acres of land in Allen, Texas with an option to purchase an additional 24 acres. In April of 2017, CyrusOne purchased 48 acres of land in Quincy, Washington. The Company purchased these parcels of land for future development for approximately $20.2 million in the aggregate. On March 31, 2016, CyrusOne LP purchased CME Group's Chicago-Aurora I data center in (the Aurora Properties) Aurora, Illinois for $131.1 million , including transaction related costs, in an all cash transaction. The purchase enhances the geographic diversification of CyrusOne, provides access to a high quality enterprise customer base and strengthens our product portfolio. The transaction adds to CyrusOne Inc.'s existing data center platform an approximately 428,000 square-foot facility data center serving the Chicago metropolitan region. In addition, CyrusOne acquired approximately 15 acres of land directly adjacent to the data center for future development. On April 1, 2016, the CME Group entered into a 15 -year lease for data center space at the Aurora facility. The agreement is expected to enhance the range of services available to the Company and CME Group's mutual customers through connectivity, hosting and data offerings. Other than the Aurora purchase, during the year ended December 31, 2016, the Company purchased four parcels of land for development for approximately $54.5 million . Business Combination On July 1, 2015, CyrusOne LP acquired 100% of Cervalis, a privately-held owner and operator of data centers for $398.4 million , excluding transaction-related expenses, in an all cash transaction. Cervalis has four data center facilities and two work recovery facilities serving the New York metropolitan area. CyrusOne LP financed the acquisition with proceeds of CyrusOne Inc.'s June 2015 common stock offering and CyrusOne LP and CyrusOne Finance Corp.'s July 2015 6.375% senior notes offering as well as drawing under CyrusOne Inc.'s Revolving Credit Facility. The acquisition of Cervalis enhances the geographic diversification of CyrusOne, provides access to a high quality enterprise customer base and strengthens our product portfolio. The goodwill recorded for this acquisition relates to the incremental value that Cervalis brings to the existing CyrusOne operations. The customer relationships intangible is expected to be amortized over fifteen years. This acquisition was accounted for as a business combination. For the year ended December 31, 2015, transaction and integration costs related to the Cervalis Acquisition were $12.9 million . The consolidated financial statements include the operating results of Cervalis from the date of acquisition. The following table summarizes the estimated fair values of all assets acquired and liabilities assumed at the date of acquisition: Cash $ 1.1 Rent and other receivables 10.5 Restricted cash 8.8 Net investment in real estate 197.8 Goodwill 178.9 Customer relationships 117.4 Trade name 2.3 Other long-term assets 5.6 Total assets acquired 522.4 Current liabilities 18.3 Capital lease obligations 1.7 Long-term debt 1.5 Lease financing arrangements 101.4 Total liabilities 122.9 Net assets acquired attributable to CyrusOne Inc. 399.5 Cash acquired (1.1 ) Net cash paid at acquisition $ 398.4 The acquisition of Cervalis in July 2015 resulted in an increase in revenue of $37.7 million for year ended December 31, 2015. The unaudited pro forma combined historical results of CyrusOne, as if Cervalis had been acquired and the financing transactions had been consummated as of January 1, 2015 are: IN MILLIONS For the year ended December 31, 2015 Revenue $ 438.6 Net loss (10.9 ) Loss per share - basic and diluted $ (0.16 ) These amounts have been calculated after applying CyrusOne's policies and adjusting the results to reflect changes to Depreciation and amortization to property and equipment, amongst others, and amortizing intangible assets had been recorded as of January 1, 2015. These pro forma combined results of operation are presented for informative purposes only and they do not purport to be indicative of the results of operation that actually would have resulted had the acquisition occurred on the date indicated, or that may result in the future.

Investment in Real Estate

Investment in Real Estate	12 Months Ended
	Dec. 31, 2017
Real Estate [Abstract]
Investment in Real Estate	Investment in Real Estate A schedule of our gross investment in real estate follows: IN MILLIONS As of December 31, 2017 2016 Land Building and Equipment Land Building and Equipment Dallas - Carrollton $ 16.1 $ 61.8 $ 210.7 $ 16.1 $ 57.6 $ 154.0 Houston - Houston West I 1.4 85.2 49.8 1.4 85.0 48.4 Cincinnati - 7th Street 0.9 110.6 33.1 0.9 110.6 21.0 Dallas - Lewisville — 76.7 37.4 — 76.7 33.7 Northern Virginia - Sterling II — 28.8 112.3 — 28.7 111.8 Somerset I 12.1 124.8 83.7 — — — Chicago - Aurora I 2.4 32.4 125.0 2.4 28.5 99.9 Totowa - Madison — 28.5 55.1 — 28.3 50.8 Cincinnati - North Cincinnati 4.0 77.4 9.9 4.0 77.3 9.0 San Antonio III — 40.3 96.8 — — — Houston - Houston West II 2.8 22.8 50.1 2.8 23.1 49.0 Wappingers Falls I — 11.3 18.0 — 11.3 17.1 San Antonio I 4.6 31.7 34.8 4.6 32.1 33.6 Phoenix - Chandler II — 16.2 38.9 — 16.1 38.8 Northern Virginia - Sterling I 7.0 20.0 59.4 7.0 19.7 47.2 Raleigh-Durham I 2.1 78.0 76.0 — — — Houston - Galleria — 68.6 17.6 — 68.6 16.6 Phoenix - Chandler I 14.8 58.2 65.9 14.8 56.8 56.5 Phoenix - Chandler III — 11.4 50.0 — 9.9 44.5 Northern Virginia - Sterling III — 22.2 61.3 — — — Austin II 2.0 23.4 7.0 2.0 23.4 6.6 San Antonio II 7.0 29.0 60.4 7.0 29.0 59.4 Florence 2.2 42.0 5.3 2.2 41.9 4.9 Phoenix - Chandler IV — 18.3 40.9 — — — Cincinnati - Hamilton — 50.2 6.0 — 50.2 5.0 London - Great Bridgewater — 28.4 1.1 — 25.9 0.9 Northern Virginia - Sterling IV 4.6 20.0 73.7 4.6 11.0 33.4 Cincinnati - Mason — 20.3 1.6 — 20.2 1.4 Dallas - Midway — 2.0 0.4 — 2.0 0.4 Phoenix - Chandler VI 10.5 15.7 49.2 10.5 — — Stamford - Riverbend — 2.9 6.9 — 4.3 14.5 Norwalk I — 13.5 9.4 — 19.0 26.6 Dallas - Marsh — 0.1 0.6 — 0.1 0.6 Chicago - Lombard 0.7 4.7 7.7 0.7 4.7 7.9 Stamford - Omega — 2.6 0.7 — 3.2 1.5 Totowa - Commerce — 4.1 1.6 — 4.1 1.4 Cincinnati - Blue Ash — 0.7 0.2 — 0.6 0.1 South Bend - Crescent — 1.7 0.1 — 1.7 0.2 Houston - Houston West III 18.4 17.9 30.7 18.4 9.4 13.5 Singapore - Inter Business Park — — — — 8.2 0.1 South Bend - Monroe — 2.5 0.3 — 2.5 0.3 Cincinnati - Goldcoast 0.2 4.0 0.1 0.2 4.0 0.1 Austin III 3.3 10.6 33.9 3.3 9.7 31.8 Northern Virginia - Sterling V 24.1 35.7 108.8 24.1 — — IN MILLIONS As of December 31, 2017 2016 Land Building and Equipment Land Building and Equipment Phoenix - Chandler V — 5.9 20.5 — — — San Antonio IV — — 17.9 — — — Austin I — — — — 3.5 0.2 Austin Land A 8.0 — 0.2 8.0 — 0.2 Chicago - Aurora II 2.6 8.3 42.9 2.6 — — Chicago - Aurora Land B 5.1 — — 5.1 — — Dallas - Allen 12.0 — — — — — Quincy Land A 3.1 — — — — — Atlanta I 5.1 — — — — — Total $ 177.1 $ 1,371.4 $ 1,813.9 $ 142.7 $ 1,008.9 $ 1,042.9 In addition, Construction in progress was $478.4 million and $407.1 million as of December 31, 2017 and December 31, 2016 , respectively, as we continue to build data center facilities. For the year ended December 31, 2017 , our capital expenditures were $1,406.8 million , as shown on the statement of cash flows. This included the purchase price of the Sentinel Properties on February 28, 2017 for $492.3 million and $914.5 million for other developments primarily in Northern Virginia, Phoenix, Dallas, Chicago, San Antonio and Cincinnati; and the purchase of parcels of land in Allen, Texas, Quincy, Washington and Atlanta, Georgia for future development. For the year ended December 31, 2016, our capital expenditures were $731.1 million , as shown on the statement of cash flows. This included the purchase of the Aurora Properties for $131.1 million , the purchase of four properties for development in Northern Virginia - Sterling, Chicago - Aurora and Phoenix - Chandler II for approximately $54.5 million and $545.5 million for other developments primarily in Northern Virginia - Sterling, Phoenix - Chandler II, San Antonio, Dallas - Carrollton and Houston - Houston West III. For the year ended December 31, 2017 , we recognized Asset impairments and loss on disposal of $59.5 million which includes the impairment loss of $54.4 million as mentioned below, and an impairment of $3.6 million related to our leased facility in Singapore, a loss on disposal of $1.1 million related to equipment at our Chicago - Aurora facility and $0.4 million related to other equipment. During the year ended December 31, 2017 , we incurred an impairment loss of $54.4 million for our Norwalk I, Stamford - Riverbend and Stamford - Omega facilities, which are in the Connecticut market and were acquired as part of the Cervalis acquisition in July 2015. These are leased facilities and Cervalis was deemed to be the accounting owner of the buildings, excluding land, due to their involvement in the construction of structural improvements to these facilities and continuing involvement once construction was completed. Upon acquisition of Cervalis, all assets acquired and liabilities assumed were recorded at their estimated fair values. For new leases, our sales cycle is typically up to two years, and our revenue and profit expectations were recently revised as compared to the assumptions contained at the time of the acquisition. Due to lack of demand we have experienced for data centers in the Connecticut market, we have revised our expectations for operations of these facilities through the end of their lease terms. The amount of impairment recognized was the excess of the carrying value over the fair value of the assets. Fair value was determined by the discounted cash flow method based on management's best estimates of a market participant using available and knowable information. For the year ended December 31, 2016, we recognized Asset impairment and loss on disposal of $5.3 million which related primarily to two properties, South Bend - Crescent, a leased facility, and Cincinnati - Goldcoast, an owned facility. For the year ended December 31, 2015, we recognized Asset impairment and loss on disposal of $13.5 million which related primarily to the exit of Austin I, which is a leased facility, and loss on disposal of certain other assets.

Notes Receivable

Notes Receivable	12 Months Ended
	Dec. 31, 2017
Receivables [Abstract]
Notes Receivable	Notes Receivable The carrying amount of notes receivable was $3.3 million and $6.6 million as of December 31, 2017 and 2016 , respectively, and consisted of the following: IN MILLIONS For the year ended December 31, 2017 2016 Note 1 $ 1.8 $ 2.2 Note 2 0.6 — Note 3 0.5 3.9 Note 4 0.4 0.5 Total $ 3.3 $ 6.6 Each of the above notes are from different customers. Note 1 matures in September 2021 , and the payments are approximately $50,000 per month. Note 2 matures in November 2019 , and the payments are approximately $26,000 per month. Note 3 matures in February 2018 , and the payments are approximately $300,000 per month. Note 4 matures in October 2020 , and the payments are approximately $12,000 per month. These notes are included in Rent and other receivables on the consolidated balance sheets.

Goodwill, Intangible and Other

Goodwill, Intangible and Other Long-Lived Assets	12 Months Ended
	Dec. 31, 2017
Goodwill and Intangible Assets Disclosure [Abstract]
Goodwill, Intangible and Other Long-Lived Assets	Goodwill, Intangible and Other Long-Lived Assets The carrying amount of Goodwill was $455.1 million as of December 31, 2017 and 2016 . See Note 6 for the increase in above/below market leases and in-place leases. Summarized below are the carrying values for the major classes of intangible assets: IN MILLIONS For the year ended December 31, 2017 2016 Weighted- Gross Carrying Amount Accumulated Amortization Total Gross Carrying Amount Accumulated Amortization Total Customer relationships 11 $ 247.1 $ (123.0 ) $ 124.1 $ 247.1 $ (106.3 ) $ 140.8 Trademark/tradename 6 9.7 (5.3 ) 4.4 9.7 (3.9 ) 5.8 Favorable leasehold interest 47 4.1 (0.5 ) 3.6 4.1 (0.5 ) 3.6 In place customer leases 8 75.9 (7.1 ) 68.8 — — — Above and below market leases 8 2.3 (0.2 ) 2.1 — — — Total $ 339.1 $ (136.1 ) $ 203.0 $ 260.9 $ (110.7 ) $ 150.2 There were no goodwill or intangible asset impairments for the years ended December 31, 2017 or 2016 . Amortization expense for acquired intangible assets was $25.1 million , $20.1 million and $18.5 million for the years ended December 31, 2017 , 2016 and 2015 , respectively. The following table presents estimated amortization expense for each of the next five years and thereafter, commencing January 1, 2018 : IN MILLIONS 2018 $ 24.7 2019 22.4 2020 21.3 2021 20.3 2022 19.7 Thereafter 94.6 Total $ 203.0

Long-Term Debt, Capital Lease O

Long-Term Debt, Capital Lease Obligations and Lease Financing Arrangements	12 Months Ended
	Dec. 31, 2017
Debt Disclosure [Abstract]
Long-Term Debt, Capital Lease Obligations and Lease Financing Arrangements	Long-Term Debt, Capital Lease Obligations and Lease Financing Arrangements Long-term debt, Capital lease obligations and Lease financing arrangements presented in the accompanying consolidated financial statements consist of the following: IN MILLIONS For the year ended December 31, 2017 2016 Credit facilities: Revolving Credit Facility $ — $ 235.0 2021 Term Loan 250.0 250.0 2022 Term Loan 650.0 300.0 2024 Notes, including bond premium 706.8 — 2027 Notes, including bond premium 510.5 — 2022 Notes, including bond premium — 477.3 Deferred financing costs (27.9 ) (22.2 ) Long-term debt, net 2,089.4 1,240.1 Capital lease obligations 10.1 10.8 Lease financing arrangements 131.9 135.7 Total $ 2,231.4 $ 1,386.6 Credit Facility —On October 9, 2014, CyrusOne LP entered into a credit agreement which provided for a $450.0 million senior unsecured revolving credit facility replacing the previous credit facility, and a $150.0 million senior unsecured term loan. On June 22, 2015, CyrusOne increased the revolving credit facility to $650.0 million and $300.0 million under the term loan. In addition, the credit agreement contained an accordion feature that allowed CyrusOne LP to increase the aggregate commitment by up to $250.0 million . On March 17, 2016, CyrusOne LP entered into a first amended and restated credit agreement (the First Amended and Restated Credit Agreement) which amended and restated in its entirety the then-existing credit agreement, as amended to such date. The First Amended and Restated Credit Agreement provided for an additional $250.0 million senior unsecured term loan facility (the 2021 Term Loan) in addition to the existing $300.0 million senior unsecured term loan facility (the 2022 Term Loan, and together with the 2021 Term Loan, the Term Loans) and the existing $650.0 million revolving credit facility (the Revolving Credit Facility). The First Amended and Restated Credit Agreement had an accordion feature under which CyrusOne LP was permitted to request an increase in the total commitments up to an amount not to exceed $250.0 million . Deferred financing costs of $2.1 million related to this amendment and restatement were recorded. On November 21, 2016, CyrusOne LP entered into a second amended and restated credit agreement which amended and restated in its entirety the First Amended and Restated Credit Agreement and, among other things, increased the available commitments under the Revolving Credit Facility to $1.0 billion . Deferred financing costs of $6.6 million related to this amendment and restatement were recorded. On June 16, 2017, CyrusOne LP entered into an amendment to its senior unsecured second amended and restated credit agreement (as amended, the Second Amended and Restated Credit Agreement) that increased the total commitments thereunder by $450.0 million to $2.0 billion and provided additional flexibility to pursue various initiatives, including joint ventures and international expansion. The amendment increased the size of the 2022 Term Loan maturing in January 2022 from $300.0 million to $650.0 million and expanded the Revolving Credit Facility by $100.0 million to $1.1 billion . Proceeds from the $350.0 million 2022 Term Loan increase were used to pay down borrowings under the Revolving Credit Facility. The existing $250.0 million 2021Term Loan maturing in September 2021 remained unchanged. In addition, the amendment refreshes the amount available under the accordion feature of the Second Amended and Restated Credit Agreement to enable CyrusOne LP to increase the total loan commitments under the Second Amended and Restated Credit Agreement to up to $2.3 billion from time to time. The Revolving Credit Facility is scheduled to mature in November 2020 and includes a one -year extension option, which if exercised by CyrusOne LP would extend the maturity date to November 2021, subject to certain conditions. The 2022 Term Loan of $650.0 million is scheduled to mature in January 2022. The 2021 Term Loan of $250.0 million is scheduled to mature in September 2021. The Revolving Credit Facility currently bears interest at a rate per annum equal to LIBOR plus 1.55% and the 2022 Term Loan and 2021 Term Loan currently bear interest at a rate per annum equal to LIBOR plus 1.50% . The margins are subject to adjustment. As of December 31, 2017 , the interest rate for the Term Loans was 2.99% . Deferred financing costs of $2.7 million related to the June 2017 amendment to the Second Amended and Restated Credit Agreement were recorded. Existing deferred financing costs of $0.3 million were recorded to Loss on extinguishment of debt due to the exit of certain lenders from the credit facility. We pay commitment fees for the unused amount of borrowings on the Revolving Credit Facility and letter of credit fees on any outstanding letters of credit. The commitment fees are up to 0.25% per annum of the actual daily amount by which the aggregate revolving commitments exceed the sum of outstanding revolving loans and letter of credit obligations. Commitment fees related to the Second Amended and Restated Credit Agreement were $1.9 million and $1.6 million for the years ended December 31, 2017 and 2016, respectively. As of December 31, 2017 , there were no outstanding borrowings under the Revolving Credit Facility and aggregate borrowings of $900.0 million on the Term Loans. In addition, the Second Amended and Restated Credit Agreement contains an accordion feature that allows CyrusOne LP to increase the aggregate commitment by up to $300.0 million . At December 31, 2017 , available capacity under the Revolving Credit Facility was $1,091.5 million , which included $1.1 billion under the Revolving Credit Facility less letters of credit of $8.5 million . Total liquidity at December 31, 2017 was $1,243.4 million , which included availability of $1,091.5 million under the Revolving Credit Facility and Cash and cash equivalents of $151.9 million . 5.000% Senior Notes due 2024 and 5.375% Senior Notes due 2027 —On March 17, 2017, CyrusOne LP and CyrusOne Finance Corp. (collectively, the Issuers) completed their offering of $500.0 million aggregate principal amount of the Original 2024 Notes and $300.0 million aggregate principal amount of the Original 2027 Notes in a private offering. The Company received proceeds of $791.2 million , net of underwriting costs of $8.8 million . In addition, the Company incurred approximately $2.1 million in other costs. Total deferred financing costs of $10.9 million related to the offering were recorded. On November 3, 2017, CyrusOne LP and CyrusOne Finance Corp. completed their offering of $200.0 million aggregate principal amount of the Additional 2024 Notes and $200.0 million aggregate principal amount of the Additional 2027 Notes in a private offering. The Additional 2024 Notes have terms substantially identical to the Original 2024 Notes and the Additional 2027 Notes have terms substantially identical to the Original 2027 Notes. The Original 2024 Notes and the Additional 2024 Notes form a single class of securities, and the Original 2027 Notes and the Additional 2027 Notes for a single class of securities. The Company received proceeds of $416.1 million , net of underwriting costs of $4.4 million . The proceeds included bond premium of $17.8 million and accrued interest of $2.7 million . In addition, the Company incurred approximately $1.0 million in other costs. The Issuers agreed to use commercially reasonable efforts to file an exchange offer registration statement with the SEC, to have the registration statement declared effective and to complete an exchange offer. On January 8, 2018, all validly tendered 2024 Notes and 2027 Notes were exchanged for notes registered with the SEC. The senior notes are senior unsecured obligations of the Issuers, which rank equally in right of payment with all existing and future unsecured senior indebtedness of the Issuers. The senior notes are effectively subordinated in right of payment to any secured indebtedness of the Issuers to the extent of the value of the assets securing such indebtedness. The senior notes are guaranteed on a joint and several basis by CyrusOne Inc., CyrusOne GP and all of CyrusOne LP’s existing domestic subsidiaries that guarantee the Second Amended and Restated Credit Agreement. Each of CyrusOne LP’s restricted subsidiaries (other than any designated excluded subsidiary or receivables entity) that guarantees any other indebtedness of CyrusOne LP or other indebtedness of the guarantors will be required to guarantee the senior notes in the future. Each such guarantee is a senior unsecured obligation of the applicable guarantor, ranking equally with all existing and future unsecured senior indebtedness of such guarantor and effectively subordinated to all existing and future secured indebtedness of such guarantor to the extent of the value of the assets securing that indebtedness. The senior notes are structurally subordinated to all liabilities (including trade payables) of each subsidiary of CyrusOne LP that does not guarantee the senior notes. The 2024 Notes and the 2027 Notes bear interest at a rate of 5.000% and 5.375% per annum, respectively. The interest on the senior notes is payable semi-annually on March 15 and September 15 of each year, to persons who are registered holders of the 2024 Notes and 2027 Notes on the immediately preceding March 1 and September 1, respectively. The 2024 Notes will mature on March 15, 2024. However, prior to March 15, 2020, the Issuers may, at their option, redeem some or all of the 2024 Notes at a redemption price equal to 100% of the principal amount of the 2024 Notes, together with accrued and unpaid interest and additional interest, if any, plus a “make-whole” premium. On or after March 15, 2020, the Issuers may, at their option, redeem some or all of the 2024 Notes at any time at declining redemption prices equal to (i) 102.500% beginning on March 15, 2020, (ii) 101.250% beginning on March 15, 2021 and (iii) 100.000% beginning on March 15, 2022 and thereafter, plus, in each case, accrued and unpaid interest and additional interest, if any, to the applicable redemption date. In addition, before March 15, 2020, and subject to certain conditions, the Issuers may, at their option, redeem up to 40% of the aggregate principal amount of 2024 Notes with the net proceeds of certain equity offerings at 105.000% of the principal amount thereof, plus accrued and unpaid interest and additional interest, if any, to the date of redemption; provided that (i) at least 55% of the aggregate principal amount of 2024 Notes remains outstanding and (ii) the redemption occurs within 90 days of the closing of any such equity offering. The 2027 Notes will mature on March 15, 2027. However, prior to March 15, 2022, the Issuers may, at their option, redeem some or all of the 2027 Notes at a redemption price equal to 100% of the principal amount of the 2027 Notes, together with accrued and unpaid interest and additional interest, if any, plus a “make-whole” premium. On or after March 15, 2022, the Issuers may, at their option, redeem some or all of the 2027 Notes at any time at declining redemption prices equal to (i) 102.688% beginning on March 15, 2022, (ii) 101.792% beginning on March 15, 2023, (iii) 100.896% beginning on March 15, 2024 and (iv) 100.000% beginning on March 15, 2025 and thereafter, plus, in each case, accrued and unpaid interest and additional interest, if any, to the applicable redemption date. In addition, before March 15, 2020, and subject to certain conditions, the Issuers may, at their option, redeem up to 40% of the aggregate principal amount of 2027 Notes with the net proceeds of certain equity offerings at 105.375% of the principal amount thereof, plus accrued and unpaid interest and additional interest, if any, to the date of redemption; provided that (i) at least 55% of the aggregate principal amount of 2027 Notes remains outstanding and (ii) the redemption occurs within 90 days of the closing of any such equity offering. 6.375% Senior Notes due 2022 —On November 20, 2012, CyrusOne LP and CyrusOne Finance Corp. issued $525.0 million of 6.375% senior notes due 2022 (the 2022 Notes). In March 2017, the Company repurchased all of its 2022 Notes with an aggregate face value of $474.8 million for total consideration of $515.1 million , including accrued and unpaid interest of $10.3 million . Deferred financing costs, bond premium and legal fees related to the 2022 Notes of $6.2 million were written off which resulted in a loss on extinguishment of debt of $36.2 million . Debt Covenants —The Second Amended and Restated Credit Agreement requires us to maintain certain financial covenants including the following, in each case on a consolidated basis: • A minimum fixed charge ratio; • Maximum total and secured leverage ratios; • A minimum consolidated tangible net worth ratio; • A maximum secured recourse indebtedness ratio; • A minimum unencumbered debt yield ratio; and • A maximum ratio of unsecured indebtedness to unencumbered asset value. Notwithstanding these limitations, we will be permitted, subject to the terms and conditions of the Second Amended and Restated Credit Agreement, to distribute to our stockholders cash dividends in an amount not to exceed 95% of our Funds From Operations (FFO), as defined in the Second Amended and Restated Credit Agreement for any period. Similarly, our indentures permit dividends and distributions necessary for us to maintain our status as a REIT. The Company’s most restrictive covenants are generally included in the Second Amended and Restated Credit Agreement. In order to continue to have access to amounts available to it under the Second Amended and Restated Credit Agreement, the Company must remain in compliance with all covenants. The indentures governing the senior notes contains affirmative and negative covenants customarily found in indebtedness of this type, including a number of covenants that, among other things, restrict, subject to certain exceptions, the Company’s ability to: incur secured or unsecured indebtedness; pay dividends or distributions on its equity interests, or redeem or repurchase equity interests of the Company; make certain investments or other restricted payments; enter into transactions with affiliates; enter into agreements limiting the ability of the operating partnership’s subsidiaries to pay dividends or make certain transfers and other payments to the operating partnership or to other subsidiaries; sell assets; and merge, consolidate or transfer all or substantially all of the operating partnership’s assets. Notwithstanding the foregoing, the covenants contained in the indentures do not restrict the Company’s ability to pay dividends or distributions to stockholders to the extent (i) no default or event of default exists or is continuing under the indentures and (ii) the Company believes in good faith that we qualify as a REIT under the Code and the payment of such dividend or distribution is necessary either to maintain its status as a REIT or to enable it to avoid payment of any tax that could be avoided by reason of such dividend or distribution. The Company and its subsidiaries are also required to maintain total unencumbered assets of at least 150% of their unsecured debt on a consolidated basis, provided that for the purposes of such calculation their Revolving Credit Facility shall be treated as unsecured indebtedness, in each case subject to certain qualifications set forth in the indenture. As of December 31, 2017 , we believe we were in compliance with all covenants. Notes Payable —The Company's note payable for approximately $1.5 million with a third-party for installation of electrical infrastructure at one of the Company's locations was repaid in July 2016. Deferred financing costs —Deferred financing costs are costs incurred in connection with obtaining long-term financing. Deferred financing costs were incurred in connection with the issuance of the Revolving Credit Facility, the 2022 Term Loan, the 2021 Term Loan, 2024 Notes and 2027 Notes. As of December 31, 2017 , and 2016 , deferred financing costs totaled $27.9 million and $22.2 million , respectively. Amortization of deferred financing costs, included in Interest expense in the consolidated statements of operations, totaled $4.7 million , $4.1 million , and $3.4 million for the years ended December 31, 2017 , 2016 and 2015 , respectively. Capital lease obligations —We use leasing as a source of financing for certain of our data center facilities and related equipment. We currently operate four data center facilities under leases recognized as capital leases. We have options to extend the initial lease term on all but one of these leases. Lease financing arrangements —Lease financing arrangements represent leases of real estate in which we are involved in the construction of structural improvements to develop buildings into data centers. When we bear substantially all the construction period risk, such as managing or funding construction, we are deemed to be the accounting owner of the leased property and, at the lease inception date, we are required to record at fair value the property and associated liability on our balance sheet. These transactions generally do not qualify for sale-leaseback accounting due to our continued involvement in these data center operations. Interest expense on Capital lease obligations and Lease financing arrangements was $9.0 million , $10.6 million and $7.8 million for the years ended December 31, 2017 , 2016 and 2015 , respectively. The following table summarizes aggregate maturities of total future value and present value of the minimum payments associated with our Lease financing arrangements for the five years subsequent to December 31, 2017 , and thereafter: IN MILLIONS Future Value of Payments Interest Present Value of Payments 2018 $ 14.9 $ 7.9 $ 7.0 2019 15.1 7.4 7.7 2020 27.8 6.8 21.0 2021 11.5 5.8 5.7 2022 11.8 5.5 6.3 Thereafter 100.6 16.4 84.2 Total lease financing arrangements $ 181.7 $ 49.8 $ 131.9 The following table summarizes aggregate maturities of the Revolving Credit Facility and Term Loans, 2024 Notes and 2027 Notes, and capital leases for the five years subsequent to December 31, 2017 , and thereafter: IN MILLIONS Revolving Credit Facility/Term Loans Senior Notes Capital Leases Total 2018 $ — $ — $ 2.0 $ 2.0 2019 — — 1.9 1.9 2020 — — 2.0 2.0 2021 250.0 — 2.0 252.0 2022 650.0 — 0.9 650.9 Thereafter — 1,200.0 1.3 1,201.3 Total debt $ 900.0 $ 1,200.0 $ 10.1 $ 2,110.1 The payment of interest on capital leases over the next five years and thereafter will be $0.8 million , $0.6 million , $0.5 million , $0.3 million , $0.1 million and $0.1 million , respectively.

Fair Value Measurements

Fair Value Measurements	12 Months Ended
	Dec. 31, 2017
Fair Value Disclosures [Abstract]
Fair Value Measurements	Fair Value Measurements The fair value of Cash and cash equivalents, Restricted cash, Rent and other receivables and Accounts payable and accrued expenses approximate their carrying value because of the short-term nature of these instruments. The carrying value and fair value of other financial instruments are as follows: IN MILLIONS For the year ended December 31, 2017 2016 Carrying Value Fair Value Carrying Value Fair Value 2024 Notes $ 706.8 $ 728.0 $ — $ — 2027 Notes 510.5 527.5 — — 2022 Notes — — 477.3 502.1 Revolving Credit Facility and Term Loans 900.0 900.0 785.0 785.0 Equity investment 100.0 175.6 — — The fair value of our 2024 Notes and 2027 Notes as of December 31, 2017 and our 2022 Notes as of December 31, 2016 were based on the quoted market price for these notes, which is considered Level 1 of the fair value hierarchy. The carrying value of the Revolving Credit Facility, the 2022 Term Loan and the 2021 Term Loan approximates estimated fair value as of December 31, 2017 and 2016 , due to the variability of interest rates and the stability of our credit ratings. Deferred financing costs of $27.9 million and $22.2 million for the years ended December 31, 2017 and 2016, respectively, are not included in the carrying value of these instruments as shown above. These fair value measurements are considered Level 3 of the fair value hierarchy. On October 18, 2017, CyrusOne announced the formation of a new strategic partnership with the execution of a commercial agreement with GDS, a leading developer and operator of high-performance, large-scale data centers in China. In addition, CyrusOne purchased newly issued unregistered ordinary shares equivalent to 8.0 million American depository shares (ADS) at a price per Class A ordinary share equivalent to $12.45 per ADS, a 4% discount to the October 17, 2017 closing price, for a total investment of $100 million . Each ADS is equivalent to eight ordinary shares. This investment is recorded in Other assets in the consolidated balance sheets. The fair value of the investment in GDS as of December 31, 2017 , was based on the quoted market price for the stock, adjusted for a discount related to the lock-up period, which is considered Level 2 of the fair value hierarchy. The estimated fair value of the equity investment in GDS as of December 31, 2017 is $175.6 million . The increase in the value of the equity investment is due to an unrealized gain of $75.6 million which is recorded in Accumulated other comprehensive income (loss) in the consolidated balance sheet as of December 31, 2017. The Company also uses fair value measurements in assessing and if required, recording an impairment loss for investments in real estate. During the year ended December 31, 2017 , we incurred an impairment loss of $54.4 million for our Norwalk I, Stamford - Riverbend and Stamford - Omega facilities. The amount of impairment recognized was the excess of the carrying value over the fair value of the assets. Fair value was determined by the discounted cash flow method based on management's best estimates of a market participant using available and knowable information. Unobservable inputs (Level 3) were a discount rate of 12% , a long-term growth rate of 3% , a market rent and expense growth rate of 2% and a capitalization rate of 9% . The fair value of the assets, at the time of impairment, was $31.7 million .

Noncontrolling Interest - Opera

Noncontrolling Interest - Operating Partnership	12 Months Ended
	Dec. 31, 2017
Noncontrolling Interest [Abstract]
Noncontrolling Interest - Operating Partnership	Noncontrolling Interest - Operating Partnership As of December 31, 2015 , Cincinnati Bell Inc. (CBI), owned approximately 9.5% of the Company’s common stock. As of December 31, 2017 and 2016, CBI owned less than 5.0% of the Company's common stock. Since December 31, 2015, CyrusOne Inc. has had no noncontrolling interests, and all of the operating partnership units of CyrusOne LP were owned, directly or indirectly, by the Company. The following table shows the distributions and net loss attributed to CBI for the year ended December 31, 2015: For the year ended December 31, 2015 (in millions, except unit amount) The Company CBI Operating partnership units 72.6 — Ownership % 100.0 % — % Portion of net loss $ (15.4 ) $ (4.8 ) Distributions $ (74.6 ) $ (16.3 )

Dividends

Dividends	12 Months Ended
	Dec. 31, 2017
Stockholders' Equity Note [Abstract]
Dividends	Dividends We have declared cash dividends on common shares and distributions on operating partnership units for the years ended December 31, 2017 and 2016 as presented in the table below: Record date Payment date Cash dividend per share or operating partnership unit March 25, 2016 April 15, 2016 $0.38 June 24, 2016 July 15, 2016 $0.38 September 30, 2016 October 14, 2016 $0.38 December 30, 2016 January 13, 2017 $0.38 March 31, 2017 April 14, 2017 $0.42 June 30, 2017 July 14, 2017 $0.42 September 29, 2017 October 13, 2017 $0.42 December 29, 2017 January 12, 2018 $0.42 As of December 31, 2017 and 2016 we had a dividend payable of $41.8 million and $33.9 million , respectively. On February 21, 2018 , we announced a regular cash dividend of $0.46 per common share payable to shareholders of record as of March 29, 2018 . The dividend will be paid on April 13, 2018 .

Customer Leases

Customer Leases	12 Months Ended
	Dec. 31, 2017
Leases [Abstract]
Customer Leases	Customer Leases Customer lease arrangements customarily contain provisions that allow either for renewal or continuation on a month-to-month arrangement. Certain leases contain early termination rights. At lease inception, early termination is generally not deemed reasonably assured due to the significant economic penalty incurred by the lessee to exercise its termination right and to relocate their equipment. The future minimum lease payments to be received under non-cancellable operating leases, excluding month-to-month arrangements and submetered power, for the next five years are shown below: IN MILLIONS 2018 $ 530.2 2019 414.1 2020 352.5 2021 289.2 2022 231.1

Employee Benefit Plans

Employee Benefit Plans	12 Months Ended
	Dec. 31, 2017
Retirement Benefits [Abstract]
Employee Benefit Plans	Employee Benefit Plans Currently, our employees participate in health care plans sponsored by CyrusOne, which provide medical, dental, vision and prescription benefits. We incurred $2.7 million , $4.4 million and $3.1 million of expenses related to these plans for the years ended December 31, 2017 , 2016 and 2015 , respectively. CyrusOne offers a retirement savings plan to its employees. CyrusOne's matching contribution to its retirement savings plan was $1.5 million , $1.5 million and $1.1 million for the years ended December 31, 2017 , 2016 and 2015 , respectively.

(Loss) Income per Share

(Loss) Income per Share	12 Months Ended
	Dec. 31, 2017
Earnings Per Share [Abstract]
(Loss) Income per Share	(Loss) Income per Share Basic (loss) income per share is calculated using the weighted average number of shares of common stock outstanding during the period. In addition, net (loss) income applicable to participating securities and the participating securities are both excluded from the computation of basic (loss) income per share. Diluted (loss) income per share is calculated using the weighted average number of shares and units of common outstanding during the period, including restricted stock outstanding and shares contingently issuable under the Forward Sales Agreement (as defined below). If there is net income during the period, the dilutive impact of common stock equivalents outstanding would also be reflected. On August 15, 2016, CyrusOne Inc. completed a public offering of 3.4 million shares of its common stock for $164.8 million , net of underwriting discounts of approximately $6.9 million . In connection with this offering, on August 10, 2016, CyrusOne Inc. entered into (a) a forward sale agreement with Goldman, Sachs & Co. with respect to 3.4 million shares of its common stock, and (b) an additional forward sale agreement with Goldman, Sachs & Co. with respect to approximately 1.0 million shares of its common stock in connection with the underwriters' exercise of their option to purchase these shares. This contract had no effect on our diluted share count at December 31, 2016. The following table reflects the computation of basic and diluted net (loss) income per share: IN MILLIONS, except per share amounts Year Ended Year Ended Period Ended For December 31, 2017 2016 2015 Basic Diluted Basic Diluted Basic Diluted Numerator: Net (loss) income $ (83.5 ) $ (83.5 ) $ 19.9 $ 19.9 $ (15.4 ) $ (15.4 ) Less: Restricted stock dividends (0.9 ) (0.9 ) (0.7 ) (0.7 ) (1.0 ) (1.0 ) Net (loss) income available to stockholders $ (84.4 ) $ (84.4 ) $ 19.2 $ 19.2 $ (16.4 ) $ (16.4 ) Denominator: Weighted average common outstanding-basic 88.9 88.9 78.3 78.3 54.3 54.3 Performance-based restricted stock and units (1)(2) — 0.7 — Weighted average shares outstanding-diluted 88.9 79.0 54.3 EPS: Net (loss) income per share-basic $ (0.95 ) $ 0.24 $ (0.30 ) Effect of dilutive shares: Net (loss) income per share-diluted $ (0.95 ) $ 0.24 $ (0.30 ) (1) We have excluded 0.4 million weighted average shares of restricted stock, and 0.1 million of weighted average stock options which are securities convertible into common stock from our diluted earnings per share as of December 31, 2017. These amounts were deemed anti-dilutive. (2) We have excluded 1.9 million weighted average shares of restricted stock, and 13.1 million of weighted average operating partnership units which are securities convertible into common stock from our diluted earnings per share as of December 31, 2015 . These amounts were deemed anti-dilutive.

Stock-Based Compensation Plans

Stock-Based Compensation Plans	12 Months Ended
	Dec. 31, 2017
Disclosure of Compensation Related Costs, Share-based Payments [Abstract]
Stock-Based Compensation Plans	Stock-Based Compensation Plans Stock-based compensation expense was as follows: For the periods ended December 31, 2017 2016 2015 Founders $ — $ 0.3 $ 5.2 2013 Grants — 0.1 1.2 2014 Grants 0.1 1.2 3.0 2015 Grants 1.8 3.5 5.0 2016 Grants 6.6 7.2 — 2017 Grants 6.2 — — Total $ 14.7 $ 12.3 $ 14.4 The board of directors of CyrusOne Inc. adopted the 2012 Long-Term Incentive Plan (LTIP) prior to the IPO, which was amended and restated on May 2, 2016. The LTIP is administered by the compensation committee of the board of directors. Awards issuable under the LTIP include common stock, restricted stock, restricted stock units, stock options and other incentive awards. CyrusOne Inc. has reserved a total of 8.9 million shares of CyrusOne Inc. common stock for issuance pursuant to the LTIP, which may be adjusted for changes in capitalization and certain corporate transactions. To the extent that an award, if forfeitable, expires, terminates or lapses, or an award is otherwise settled in cash without the delivery of shares of common stock to the participant, then any unpaid shares subject to the award will be available for future grant or issuance under the LTIP. The payment of dividend equivalents in cash in conjunction with any outstanding awards will not be counted against the shares available for issuance under the LTIP. The related stock compensation expense incurred by CyrusOne Inc. is allocated to the operating partnership. Shares available under the LTIP at December 31, 2017 , were approximately 5.5 million . Shares vest according to each agreement and as long as the employee remains employed with the Company. The Company has granted awards with time-based vesting, performance-based vesting and market-based vesting features. The performance-based vesting metrics granted have varied and are described in each of the grant years below. The market-based metric is total stockholder return (TSR), which is a non-GAAP measure and is the shareholder return compared to the MSCI US REIT Index (REIT Index) as defined in the award agreements. The TSR awards granted in 2013 had three-year cliff vesting. Subsequent to 2013, the market-based restricted stock/units vest annually based upon the achievement of certain criteria for each of the three -year measurement periods. The first two years are capped at 100% of the target. If at the end of the third year total performance over the three -year period exceeds the REIT Index by more than 2% , up to 200% of these awards may vest. The market-based awards will vest based on the below scales. The scales are linear between each point and awards are interpolated between the points. - If CyrusOne's TSR is less than the return of the Index = 0% - If CyrusOne's TSR is equal to or greater than the return of the Index = 100% ; up to 200% if CyrusOne's TSR exceeds the return of the Index by 2% - If CyrusOne's TSR exceeds the return of the Index, but is negative, any calculated vesting amount will be reduced by 50% The Company uses the Black-Scholes option-pricing model for time and performance-based options and a Monte Carlo simulation for market-based awards. The fair values of these awards use assumptions such as volatility, risk-free interest rate, and expected term of the awards. The holders of restricted stock have all the rights and privileges of shareholders including the right to vote. The holders of restricted stock units do not have all of the rights and privileges of shareholders and do not have the right to vote. These rights will be acquired upon the settlement of the restricted stock units and the issuance of shares. The time-based restricted stock units have the right to receive dividends that are payable within ten days following the date the dividends are payable to shareholders. Market-based restricted stock units accrue dividends which are paid upon the settlement of the units. Compensation expense is measured based on the estimated grant-date fair value. Expense for time-based grants is recognized under a straight-line method. For market-based grants, expense is recognized under a graded expense attribution method. For performance-based grants, expense is recognized under a graded expense attribution method if it is probable that the performance targets will be achieved. Any dividends declared with respect to the performance and market-based shares shall be accrued by the Company and distributed on the vesting date provided that the applicable performance goal has been attained. The compensation expense for the year ended December 31, 2016 includes $0.8 million due to the acceleration of equity awards of a senior executive who left the Company. The compensation expense for the year ended December 31, 2015 includes $2.4 million due to the acceleration of equity awards of two senior executives who left the Company. Founders Grants On January 24, 2013, the Company granted one million shares of time-based restricted stock, which had an aggregate value of $19.0 million on the grant date and vested on January 24, 2016 . 2013 Grants On April 17, 2013, the Company issued performance and market-based awards in the form of stock options and restricted stock. For these awards, vesting was tied 50% to the achievement of a non-GAAP performance measure (cumulative EBITDA targets, as defined in the agreement) using the scale, described below under 2014 Grants, over the 2013-2015 performance period, and 50% to a market-based performance measure. The portion of the awards tied to cumulative EBITDA vested annually over a three -year period based on the Company attaining predetermined cumulative EBITDA targets. The stock option awards have a contractual life of 10 years from the award date and were granted with an exercise price equal to $23.58 . Total awards granted in 2013 had a grant date fair value of $25.4 million . As of December 31, 2017 , there was no unearned compensation related to the awards granted in 2013 as all such awards are fully vested. 2014 Grants On February 7, 2014, the Company issued performance and market-based awards under the LTIP in the form of restricted stock. For these awards, vesting was tied 50% to the achievement of a non-GAAP performance measure (cumulative Adjusted EBITDA targets, as defined in the agreement) over the 2014-2016 performance period, and 50% to a market-based performance measure. The portion of the awards tied to cumulative Adjusted EBITDA vested annually over a three -year period based on the Company attaining predetermined cumulative Adjusted EBITDA targets and as long as the employee remained employed with the Company. The cumulative EBITDA targets are based on the below scales. The scales are linear between each point and awards are interpolated between the points. - Below 90% of performance target = 0% - At 90% of performance target = 50% - At 100% of performance target = 100% - At or above 115% of performance target = up to 200% In addition, during the year ended December 31, 2014, the Company also granted from time-to-time a total of 46,313 additional time-based restricted shares which had an aggregate value of $1.0 million on the grant date. These shares cliff vested either one year after the grant date or three years after the grant date. Total awards granted in 2014 had a grant date fair value of $12.9 million . As of December 31, 2017 , there was no unearned compensation related to the awards granted in 2014 as all such awards are fully vested. 2015 Grants On February 10, 2015, the Company issued awards under the LTIP in the form of options and restricted stock. The stock options are time-based and vest annually on a pro-rata basis over three years. Twenty percent of the restricted stock awards are subject to time-based vesting and eighty percent of the restricted stock awards are equally split between performance-based and market-based vesting. The performance-based metric is return on assets, which is a non-GAAP measure that is defined in the award agreement. The time-based restricted stock will vest pro-rata annually over three years . The performance and market-based restricted stock will vest annually based upon the achievement of certain criteria for each year of the three -year measurement periods. The first two years are capped at 100% of the target with a cumulative true-up to a maximum of 200% possible in year three. The performance-based awards will vest based on the same scales as the awards granted during 2014. In addition, during the year ended December 31, 2015, the Company also granted from time to time a total of 50,300 shares of time-based restricted stock and 67,012 shares of performance-based restricted stock for various new employee hires with vesting schedules ranging from annual to cliff vesting in three years. Total awards granted in 2015 had a grant date fair value of $13.8 million . For the year ended December 31, 2017 , the unearned compensation representing the unvested portion of the awards granted in 2015 totaled $0.3 million , with a weighted average vesting period of 0.2 years. 2016 Grants On February 1, 2016, the Company issued 641,097 shares of time, performance and market-based awards under the LTIP in the form of restricted stock. The grant date fair value of time and performance-based restricted shares was $36.99 . The grant date fair value of market-based restricted shares was $43.66 . The Company issued stock options on February 1, 2016. The stock option awards have a contractual life of 10 years from the award date and were granted with an exercise price equal to $36.99 . The Company issued 222,461 options with a grant date fair value of $6.99 . The performance-based metric is return on assets, which is a non-GAAP measure and is defined in the award agreement. The time-based restricted stock awards generally vest pro-rata annually over a three -year period. The performance and market-based restricted stock awards vest annually based upon the achievement of certain criteria for each of the three -year measurement periods. The first two years are capped at 100% of the target with a cumulative true-up to a maximum of 200% possible in year three. Certain employees were also awarded time-based restricted stock that cliff vest at the end of three years. The stock options are time-based and vest annually on a pro-rata basis over three years. The performance-based awards will vest based on the same scales as the awards granted during 2014. In addition, during the year ended December 31, 2016, for various new employee hires, the following grants were made: • 5,894 shares of time-based restricted stock which cliff vest in three years from the date of each grant. • 47,667 shares of time-based restricted stock which vest annually on a pro rata basis over a three -year period from the date of each grant. Total awards granted in 2016 had a grant date fair value of $22.6 million . As of December 31, 2017 , unearned compensation representing the unvested portion of the awards granted in 2016 totaled $7.1 million , with a weighted average vesting period of 1.1 years. 2017 Grants On February 13, 2017, the Company issued time and market-based awards under the LTIP in the form of restricted stock units and restricted stock. The Company granted 119,218 time-based restricted stock units that generally vest annually on a pro-rata basis over a three -year period and 18,179 shares of time-based restricted stock that generally vest over a one -year period with a grant date fair value of $48.13 , and 129,146 market-based restricted stock units, at target, with a grant date fair value of $63.23 . In addition, during the year ended December 31, 2017 the Company granted from time to time a total of 20,852 time-based restricted stock units that vest annually on a pro rata basis over a three -year period. Total awards granted in 2017 had a grant date fair value of $15.9 million . As of December 31, 2017 , unearned compensation representing the unvested portion of the awards granted in 2017 totaled $9.5 million , with a weighted average vesting period of 1.6 years. Restricted Stock and Stock Option Activity The following table summarizes the unvested restricted stock/unit activity and the weighted average fair value of these shares at the date of grant for the year ended December 31, 2017 : For the year ended December 31, 2017 Shares Weighted Average Grant Date Fair Value Non-vested at January 1 1,274,713 $ 28.95 Granted 287,395 55.46 Vested (446,623 ) 26.83 Forfeited (135,385 ) 21.92 Non-vested at December 31 980,100 $ 38.66 The non-vested shares/units at December 31, 2015 were 1,585,010 . The following table summarizes the stock option activity for the year ended December 31, 2017 : For the year ended December 31, 2017 Options Weighted Average Exercise Price Outstanding at January 1 434,268 $ 31.89 Granted — — Exercised (18,809 ) 36.79 Forfeited or expired — — Outstanding at December 31 415,459 31.67 Exercisable at December 31 235,395 29.45 Vested and expected to vest 415,459 $ 31.67 The outstanding options at December 31, 2015 were 334,402 . The aggregate intrinsic value of options outstanding and options exercisable is based on the Company's closing stock price on the last trading day of the fiscal year for in-the-money options. The aggregate intrinsic value represents the cumulative difference between the fair market value of the underlying common stock and the option exercise prices. The total intrinsic value of options exercised during 2017 was $0.5 million , 2016 was $1.3 million and 2015 was immaterial. The aggregate intrinsic value of options outstanding at December 31, 2017 was $11.6 million . The aggregate intrinsic value of options exercisable at December 31, 2017 was $7.1 million . Stock Option Assumptions The following table summarizes the stock option assumptions for the years ended December 31, 2017 , 2016 and 2015 : Options Outstanding Options Exercisable Assumption Range Exercise Prices Number of Shares Weighted Average Remaining Contractual Terms (Years) Number of Shares Weighted Average Remaining Contractual Terms (Years) Risk-Free Interest Rate Expected Annual Dividend Yield Expected Terms in Years Expected Volatility 2015 $23.58 142,556 7.3 43,460 7.3 0.92% 3.4% 6.0 35% $28.42 178,704 9.1 35,346 9.1 1.6% - 1.75% 4.4% 5.5-6.5 32.5% - 37.5% $30.74 12,719 9.6 — 0.0 1.6% - 1.75% 4.4% 5.5-6.5 32.5% - 37.5% 2016 $23.58 67,601 6.3 67,601 6.3 0.92% 3.4% 6.0 35% $28.42 143,358 8.1 47,786 8.1 1.6% - 1.75% 4.4% 5.5-6.5 32.5% - 37.5% $30.74 12,719 8.6 4,240 8.6 1.6% - 1.75% 4.4% 5.5-6.5 32.5% - 37.5% $36.99 210,590 9.1 18,530 9.1 1.47% - 1.64% 4.1% 5.5-6.5 27.5% - 35.0% 2017 $23.58 67,322 5.3 67,322 5.3 0.92% 3.4% 6.0 35% $28.42 143,358 7.1 95,572 7.1 1.6% - 1.75% 4.4% 5.5-6.5 32.5% - 37.5% $30.74 12,719 7.6 8,479 7.6 1.6% - 1.75% 4.4% 5.5-6.5 32.5% - 37.5% $36.99 192,060 8.1 64,022 8.1 1.47% - 1.64% 4.1% 5.5-6.5 27.5% - 35.0%

Related Party Transactions

Related Party Transactions	12 Months Ended
	Dec. 31, 2017
Related Party Transactions [Abstract]
Related Party Transactions	Related Party Transactions CBI Prior to November 20, 2012, CyrusOne Inc., CyrusOne GP, CyrusOne LP and its subsidiaries were operated by CBI. The consolidated financial statements reflect the following transactions with CBI and its affiliated entities, including Cincinnati Bell Telephone (CBT) and Cincinnati Bell Technology Solutions (CBTS). At December 31, 2015, CBI owned 9.5% of the outstanding common stock of CyrusOne Inc. and no operating partnership units, at which point it ceased to be a related party of CyrusOne Inc. As of December 31, 2017 and December 31, 2016 , CBI owned less than 5% of the outstanding common stock of CyrusOne Inc. Revenues —The Company records revenues from CBI under contractual service arrangements. These services include leasing of data center space, power and cooling in certain of our data center facilities, network interface services and office space. Operating Expenses —The Company records expenses from CBI incurred in relation to network support, services calls, monitoring and management, storage and backup, IT systems support, and connectivity services. The following related party transactions are based on agreements and arrangements that were in place during 2015. Revenues and expenses for the period presented were as follows: IN MILLIONS December 31, 2015 Revenue: Data center colocation agreement provided to CBT and CBTS $ 7.8 229 West 7th Street lease provided to CBT 1.9 Goldcoast Drive/Parkway (Mason) lease 0.3 Transition services provided to CBTS (network interfaces) 0.3 Data center leases provided to CBTS 12.0 Total revenue $ 22.3 Operating costs and expenses: Transition services agreement by CBTS $ 0.7 Charges for services provided by CBT (connectivity) 1.0 209 West 7th Street rent provided by CBT 0.2 Total operating costs and expenses $ 1.9 Other Related Party Transactions Our director, Lynn A. Wentworth, is a member of the board of directors of CBI, and serves as the chair of its audit and finance committee.

Income Taxes

Income Taxes	12 Months Ended
	Dec. 31, 2017
Income Tax Disclosure [Abstract]
Income Taxes	Income Taxes CyrusOne Inc. elected to be taxed as a REIT under the Code, commencing with our taxable year ended December 31, 2013. To remain qualified as a REIT, we are required to distribute at least 90% of our taxable income to our stockholders and meet various other requirements imposed by the Code relating to such matters as operating results, asset holdings, distribution levels and diversity of stock ownership. Provided we continue to qualify for taxation as a REIT, we are generally not subject to corporate level federal income tax on the earnings distributed currently to our stockholders. It is our policy and intent, subject to change, to distribute 100% of our taxable income and therefore no provision is required in the accompanying financial statements for federal income taxes with regards to activities of CyrusOne Inc. and its subsidiary pass-through entities. We have elected to designate two subsidiaries as taxable REIT subsidiaries (each a TRS). The activities of a TRS may include performing services for our tenants that would otherwise be considered impermissible for REITs. The income of a TRS is subject to federal and state taxes. While CyrusOne Inc. and the operating partnership do not pay federal income taxes, we are still subject to foreign, state, and local income taxes in the locations in which we conduct business. Income tax expense for the years ended December 31, 2017 , 2016 and 2015 was $3.0 million , $1.8 million and $1.8 million , respectively. For certain entities we calculate deferred tax assets and liabilities for temporary differences in the basis between financial statement and income tax assets and liabilities. Deferred income taxes are recalculated annually at rates then in effect. Valuation allowances are recorded to reduce deferred tax assets to amounts that are more likely than not to be realized. The ultimate realization of the deferred tax assets depends upon our ability to generate future taxable income during the periods in which basis differences and other deductions become deductible and prior to the expiration of the net operating loss carryforwards. Deferred tax assets (net of valuation allowance) and liabilities were accrued, as necessary, for the years ended December 31, 2017 and 2016 . Historically, we have recorded a full valuation allowance on our foreign net deferred tax assets related to our foreign generated net operating losses due to the uncertainty of their realization. In 2013 and 2014, management determined it was necessary to record a full valuation allowance on all of our domestic and foreign net deferred tax assets due to the uncertainty of their realization. Accordingly, at December 31, 2017 and at December 31, 2016 , the net domestic and foreign deferred tax assets were zero . The Company adopted ASU No. 2015-17, Income Taxes (Topic 740), in the fourth quarter of 2016 and applied it prospectively to all deferred tax assets and liabilities. The adoption had no effect on our consolidated financial statements. In 2017 and 2016 , we paid all our dividends in cash. The following table summarizes the taxability of our common stock dividends per share for the years ended December 31, 2017 and 2016 : For the year ended December 31, 2017 2016 Common Stock dividend per share: Ordinary income $ — $ 0.20 Return of capital 1.64 1.26 Total dividend $ 1.64 $ 1.46 Common stock dividends may be characterized for federal income tax purposes as "ordinary income", "qualified dividend income", "capital gains dividends", non-taxable return of capital, "qualified REIT dividends" (but only for taxable years beginning after December 31, 2017 and before January 1, 2026) or a combination of the foregoing. Common stock dividends that exceed our current and accumulated earnings and profits (calculated for tax purposes) constitute a return of capital rather than a dividend and generally reduce the stockholder's basis in the common stock. To the extent that a dividend exceeds both current and accumulated earnings and profits and the stockholder's basis in the common stock, it will generally be treated as gain from the sale or exchange of that stockholder's common stock. At the beginning of each year, we notify our stockholders of the taxability of the common stock dividends paid during the preceding year. Tax Cuts and Jobs Act of 2017 (the TCJA) The TCJA was signed into law on December 22, 2017. The TCJA significantly changed the U.S. federal income tax laws applicable to businesses and their owners, including REITs and their stockholders. Technical corrections or other amendments to the TCJA or administrative guidance interpreting the TCJA may be forthcoming at any time. We cannot predict with certainty the long-term effect of the TCJA or any future law changes on REITs or their stockholders. Below illustrates some of the key changes in the TCJA that may directly impact REITs and their stockholders with respect to an investment in REITs. The changes described below are effective for taxable years beginning after December 31, 2017, unless otherwise noted. Investors should consult with their tax advisors regarding the effect of the TCJA for their particular circumstances. Income Tax Rates. Under the TCJA, the corporate income tax rate is reduced from a maximum marginal rate of 35% to a flat rate of 21%. Our REIT is not subject to federal income taxes and we do not anticipate that our taxable REIT subsidiaries will materially benefit from this federal tax rate reduction, nor should there be a material impact on our deferred taxes as a result of the rate reduction. The rate of U.S. federal withholding tax on distributions made to non-U.S. shareholders by a REIT that are attributable to gains from the sale or exchange of U.S. real property interests will also be reduced from 35% to 21%. The TCJA also reduces the highest marginal income tax rate applicable to individuals from 39.6% to 37% (excluding the 3.8% Medicare tax on net investment income) for tax years beginning after December 31, 2017 and before January 1, 2026. Individuals will continue to pay a maximum 20% rate on long term capital gains and qualified dividend income. Generally, dividends payable by REITs do not constitute qualified dividend income. However, the TCJA also allows non-corporate U.S. shareholders to deduct 20% of “qualified REIT dividends” for tax years beginning after December 31, 2017 and before January 1, 2026. A “qualified REIT dividend” is any dividend from a REIT received during the taxable year that is not designated by the REIT as a capital gain dividend or as qualified dividend income. Limitation on Deductibility of Business Interest. Under the TCJA, in general, the deductibility of interest for a business, other than certain small businesses, is limited to 30% of the business’ adjusted taxable income (which, for purposes of the limitation on the deductibility of business interest, is defined as taxable income computed without regard to certain items of income or deduction, including the deductions for business interest and net operating losses). However, there is an exception to this limitation requirement for a “real property trade or business”, assuming a valid Internal Revenue Service election has been made. A “real property trade or business” is any property development, redevelopment, construction, reconstruction, acquisition, conversion, rental, operation, management, leasing, or brokerage trade or business. REITs are considered a real property trade or business and as such, may make an election to be exempt from the interest limitation requirements. If such election is made by a REIT, the REIT would be required to use a less favorable tax depreciation method to depreciate its real property used in a trade or business. We are currently evaluating the feasibility of making this election in 2018 and if made, we do not believe the required change to a less favorable depreciation method will have a material impact on our financials.

Commitments and Contingencies

Commitments and Contingencies	12 Months Ended
	Dec. 31, 2017
Commitments and Contingencies Disclosure [Abstract]
Commitments and Contingencies	Commitments and Contingencies Operating Leases We lease certain data center facilities and equipment from third parties. Operating lease expense was $8.2 million , $7.5 million and $7.4 million for the years ended December 31, 2017 , 2016 and 2015 , respectively. Certain of these leases provide for renewal options with fixed rent escalations beyond the initial lease term. At December 31, 2017 , future minimum lease payments required under operating leases having initial or remaining non-cancellable lease terms in excess of one year are as follows: IN MILLIONS 2018 $ 4.8 2019 2.3 2020 1.7 2021 0.6 2022 0.5 Thereafter 4.2 Total $ 14.1 Standby Letters of Credit As of December 31, 2017 , CyrusOne Inc. had outstanding letters of credit of $8.5 million as security for obligations under the terms of the lease agreements. Performance Guarantees Customer contracts generally require specified levels of performance related to uninterrupted service and cooling temperatures. If these performance standards are not met, we could be obligated to issue billing credits to the customer. Management assesses the probability that a performance standard will not be achieved. As of December 31, 2017 and 2016 , no accruals for performance guarantees were required. Indemnifications During the normal course of business, CyrusOne has made certain indemnities, commitments and guarantees under which it may be required to make payments in relation to certain transactions. These include (i) intellectual property indemnities to customers in connection with the use, sale, and/or license of products and services, (ii) indemnities to vendors and service providers pertaining to claims based on negligence or willful misconduct and (iii) indemnities involving the representations and warranties in certain contracts. In addition, CyrusOne has made contractual commitments to several employees providing for payments upon the occurrence of certain prescribed events. The majority of these indemnities, commitments and guarantees do not provide for any limitation on the maximum potential for future payments that we could be obligated to make. Purchase Commitments CyrusOne has non-cancellable purchase commitments for certain services and contracts related to construction of data center facilities and equipment. These agreements range from one to two years and provide for payments for early termination or require minimum payments for the remaining term. As of December 31, 2017 , the minimum commitments for these arrangements were approximately $69.8 million . Contingencies CyrusOne is involved in legal, tax and regulatory proceedings arising from the conduct of its business activities. Liabilities are established for loss contingencies when losses associated with such claims are deemed to be probable, and the loss can be reasonably estimated. Based on information currently available and consultation with legal counsel, we believe that the outcome of all claims will not, individually or in the aggregate, have a material effect on our financial statements.

Guarantors

Guarantors	12 Months Ended
	Dec. 31, 2017
Condensed Financial Information of Parent Company Only Disclosure [Abstract]
Guarantors	Guarantors CyrusOne LP and CyrusOne Finance Corp., as “LP Co-issuer” and “Finance Co-issuer,” respectively, had $706.8 million aggregate principal amount of their 2024 Notes and $510.5 million aggregate principal amount of their 2027 Notes outstanding at December 31, 2017 . As of December 31, 2017 , the 2024 Notes and 2027 Notes are fully and unconditionally and jointly and severally guaranteed on a senior unsecured basis by CyrusOne Inc. (Parent Guarantor), CyrusOne GP (General Partner), and CyrusOne LP’s wholly owned domestic subsidiaries, CyrusOne LLC, CyrusOne TRS Inc., CyrusOne Foreign Holdings LLC, Cervalis Holdings LLC, Cervalis LLC, CyrusOne-NJ LLC and CyrusOne-NC LLC (such subsidiaries, together, the Guarantor Subsidiaries). Non-Guarantor Subsidiaries consist of wholly owned subsidiaries organized outside of the United States, as well as CyrusOne Government Services LLC, a Delaware limited liability company, Warhol TRS LLC, a Delaware limited liability company (Warhol TRS), Warhol Partnership LLC, a Delaware limited liability company (Warhol Partnership), Warhol REIT LLC, a Delaware limited liability company (Warhol REIT and, together with Warhol TRS and Warhol Partnership, the Warhol Entities), and Cheetah Asia Holdings LLC, each of which is an indirect wholly owned subsidiary of CyrusOne LP, and the Finance Co-Issuer. None of the Non-Guarantor Subsidiaries guarantee the 2024 Notes and 2027 Notes. Subject to the provisions of the indentures governing the 2024 Notes and 2027 Notes, in certain circumstances, a Guarantor may be released from its guarantee obligation, including: • upon the sale or other disposition (including by way of consolidation or merger) of such Guarantor or of all of the capital stock of such Guarantor such that such Guarantor is no longer a restricted subsidiary under the indentures, • upon the sale or disposition of all or substantially all of the assets of the Guarantor, • upon the LP Co-issuer designating such Guarantor as an unrestricted subsidiary under the terms of the indentures, • if such Guarantor is no longer a guarantor or other obligor of any other indebtedness of the LP Co-issuer or the Parent Guarantor, • upon the LP Co-issuer designating such Guarantor as an excluded subsidiary under the terms of the indentures, and • upon the defeasance or discharge of the New Notes in accordance with the terms of the indentures. The entity structure of each Issuer and guarantor of the 2024 Notes and 2027 Notes is described below. CyrusOne Inc. – CyrusOne Inc. is the Parent Guarantor and became a separate registrant with the SEC upon completion of its IPO on January 24, 2013. CyrusOne GP – CyrusOne GP is the general partner and 1% owner of CyrusOne LP and has no other assets or operations. Issuers – The Issuers are CyrusOne LP and CyrusOne Finance Corp. CyrusOne Finance Corp., a wholly owned subsidiary of CyrusOne LP, was formed for the sole purpose of acting as co-issuer of senior notes and has no other assets or operations. CyrusOne LP, in addition to being the co-issuer of the 2024 Notes and 2027 Notes, is also the 100% owner, either directly or indirectly, of the Guarantor Subsidiaries and Non-Guarantor Subsidiaries. Guarantor Subsidiaries – The guarantors of the 2024 Notes and 2027 Notes include CyrusOne LLC, CyrusOne TRS Inc., CyrusOne Foreign Holdings LLC, Cervalis Holdings LLC, Cervalis LLC, CyrusOne-NJ LLC and CyrusOne-NC LLC, which agreed to provide unconditional guarantees of the Issuers’ obligations under the 2024 Notes and 2027 Notes. The guarantee of each Guarantor Subsidiary is (i) a senior unsecured obligation of such Guarantor Subsidiary, (ii) pari passu in right of payment with any existing and future unsecured senior indebtedness of such Guarantor Subsidiary, (iii) senior in right of payment to any future subordinated indebtedness of such Guarantor Subsidiary and (iv) effectively subordinated in right of payment to all existing and future secured indebtedness of such Guarantor Subsidiary, to the extent of the value of the collateral securing that indebtedness. CyrusOne LLC, together with CyrusOne Foreign Holdings LLC, directly or indirectly owns 100% of the Non-Guarantor Subsidiaries, except for the Warhol Entities, Cheetah Asia Holdings LLC and GDS Holdings Limited which are directly or indirectly owned by CyrusOne LP. Non-Guarantor Subsidiaries consist of wholly owned subsidiaries which conduct operations in the United Kingdom and Singapore, as well as CyrusOne Government Services LLC, a Delaware limited liability company, the Warhol Entities, Cheetah Asia Holdings LLC and GDS Holdings Limited, each of which is directly or indirectly owned by CyrusOne LP, and the Finance Co-Issuer. The Warhol Entities do not have any assets or operations other than the ownership by Warhol TRS of 0.2% of Warhol Partnership, the ownership by Warhol Partnership of 100% of Warhol REIT, and the ownership by Warhol REIT of 100% of CyrusOne Foreign Holdings LLC. The following schedules present the balance sheets as of December 31, 2017 and 2016 , and the statements of operations and comprehensive (loss) income for the years ended December 31, 2017 , 2016 and 2015 , and the statements of cash flows for the years ended December 31, 2017 , 2016 and 2015 for the Parent Guarantor, General Partner, LP Co-issuer, Finance Co-issuer, Guarantor Subsidiaries, and Non-Guarantor Subsidiaries. The consolidating statements of cash flows for the year ended December 31, 2017 includes the purchase of the Sentinel Properties on February 28, 2017. The consolidating statements of cash flows for the year ended December 31, 2016 includes the purchase of CME in March 2016. The condensed consolidating statements of cash flows for the year ended December 31, 2015, includes the acquisition of Cervalis in July 2015. The results for the CME and Sentinel Properties purchases are included in the Guarantor Subsidiaries financial statements subsequent to the respective acquisitions. The results for Cervalis are included in the Guarantor Subsidiaries financial statements subsequent to the acquisition. Consolidating Balance Sheets IN MILLIONS As of December 31, 2017 Parent General LP Finance Guarantor Subsidiaries Non- Eliminations/Consolidations Total Land $ — $ — $ — $ — $ 177.1 $ — $ — $ 177.1 Buildings and improvements — — — — 1,340.8 28.4 2.2 1,371.4 Equipment — — — — 1,803.9 1.1 8.9 1,813.9 Construction in progress — — — — 471.7 0.1 6.6 478.4 Subtotal — — — — 3,793.5 29.6 17.7 3,840.8 Accumulated depreciation — — — — (778.6 ) (3.8 ) — (782.4 ) Net investment in real estate — — — — 3,014.9 25.8 17.7 3,058.4 Cash and cash equivalents — — — — 151.2 0.7 — 151.9 Investment in subsidiaries 1,718.0 17.2 2,190.2 — — — (3,925.4 ) — Rent and other receivables, net — — — — 87.9 2.6 — 90.5 Intercompany receivable 20.0 — 1,656.4 — — — (1,676.4 ) — Goodwill — — — — 455.1 — — 455.1 Intangible assets, net — — — — 203.0 — — 203.0 Other assets — — 0.5 — 174.4 178.3 — 353.2 Total assets $ 1,738.0 $ 17.2 $ 3,847.1 $ — $ 4,086.5 $ 207.4 $ (5,584.1 ) $ 4,312.1 Accounts payable and accrued expenses $ 41.8 $ — $ 19.7 — $ 192.8 $ 0.9 $ — $ 255.2 Deferred revenue — — — — 110.8 0.8 — 111.6 Intercompany payable — — 20.0 — 1,656.4 — (1,676.4 ) — Capital lease obligations — — — — 5.4 4.7 — 10.1 Long-term debt, net — — 2,089.4 — — — — 2,089.4 Lease financing arrangements — — — — 104.6 27.3 — 131.9 Total liabilities 41.8 — 2,129.1 — 2,070.0 33.7 (1,676.4 ) 2,598.2 Total stockholders' equity 1,696.2 17.2 1,718.0 — 2,016.5 173.7 (3,907.7 ) 1,713.9 Total liabilities and equity $ 1,738.0 $ 17.2 $ 3,847.1 $ — $ 4,086.5 $ 207.4 $ (5,584.1 ) $ 4,312.1 IN MILLIONS As of December 31, 2016 Parent General LP Finance Guarantor Subsidiaries Non- Eliminations/Consolidations Total Land $ — $ — $ — $ — $ 142.7 $ — $ — $ 142.7 Buildings and improvements — — — — 973.6 34.1 1.2 1,008.9 Equipment — — — — 1,036.8 1.0 5.1 1,042.9 Construction in progress — — — — 406.4 — 0.7 407.1 Subtotal — — — — 2,559.5 35.1 7.0 2,601.6 Accumulated depreciation — — — — (571.3 ) (7.2 ) — (578.5 ) Net investment in real estate — — — — 1,988.2 27.9 7.0 2,023.1 Cash and cash equivalents — — — — 13.4 1.2 — 14.6 Investment in subsidiaries 1,170.3 11.7 1,376.1 — 2.0 — (2,560.1 ) — Rent and other receivables, net — — — — 81.8 1.5 — 83.3 Intercompany receivable 18.6 — 1,057.7 — — 0.5 (1,076.8 ) — Goodwill — — — — 455.1 — — 455.1 Intangible assets, net — — — — 150.2 — — 150.2 Other assets — — — — 123.4 2.7 — 126.1 Total assets $ 1,188.9 $ 11.7 $ 2,433.8 $ — $ 2,814.1 $ 33.8 $ (3,629.9 ) $ 2,852.4 Accounts payable and accrued expenses $ 33.9 $ — $ 4.8 — $ 187.7 $ 0.7 $ — $ 227.1 Deferred revenue — — — — 76.0 0.7 — 76.7 Intercompany payable — — 18.6 — 1,058.2 — (1,076.8 ) — Capital lease obligations — — — — 5.6 5.2 — 10.8 Long-term debt, net — — 1,240.1 — — — — 1,240.1 Lease financing arrangements — — — — 110.5 25.2 — 135.7 Total liabilities 33.9 — 1,263.5 — 1,438.0 31.8 (1,076.8 ) 1,690.4 Total stockholders' equity 1,155.0 11.7 1,170.3 — 1,376.1 2.0 (2,553.1 ) 1,162.0 Total liabilities and equity $ 1,188.9 $ 11.7 $ 2,433.8 $ — $ 2,814.1 $ 33.8 $ (3,629.9 ) $ 2,852.4 Consolidating Statements of Operations and Comprehensive Income (Loss) IN MILLIONS Year Ended December 31, 2017 Parent Guarantor General Partner LP Co-issuer Finance Co-issuer Guarantor Subsidiaries Non- Guarantors Eliminations/Consolidations Total Revenue: Base revenue and other $ — $ — $ — $ — $ 598.2 $ 4.2 $ — $ 602.4 Metered power reimbursements — — — — 68.2 1.4 — 69.6 Revenue — — — — 666.4 5.6 — 672.0 Costs and expenses: Property operating expenses — — — — 232.5 2.6 — 235.1 Sales and marketing — — — — 17.0 — — 17.0 General and administrative — — — — 66.8 0.2 — 67.0 Depreciation and amortization — — — — 257.8 1.1 — 258.9 Transaction and acquisition integration costs — — — — 10.4 — — 10.4 Asset impairments and loss on disposal — — — — 55.9 3.6 — 59.5 Total costs and expenses — — — — 640.4 7.5 — 647.9 Operating income — — — — 26.0 (1.9 ) — 24.1 Interest expense — — 76.2 — — 2.6 (10.7 ) 68.1 Loss on extinguishment of debt — — 36.5 — — — — 36.5 (Loss) income before income taxes — — (112.7 ) — 26.0 (4.5 ) 10.7 (80.5 ) Income tax expense — — — — (3.0 ) — — (3.0 ) Equity (loss) earnings related to investment in subsidiaries (18.7 ) (0.2 ) 94.0 — (4.6 ) — (70.5 ) — Net (loss) income (18.7 ) (0.2 ) (18.7 ) — 18.4 (4.5 ) (59.8 ) (83.5 ) Other comprehensive income — — — — — 75.5 — 75.5 Comprehensive (loss) income $ (18.7 ) $ (0.2 ) $ (18.7 ) $ — $ 18.4 $ 71.0 $ (59.8 ) $ (8.0 ) IN MILLIONS Year Ended December 31, 2016 Parent Guarantor General Partner LP Co-issuer Finance Co-issuer Guarantor Subsidiaries Non- Guarantors Eliminations/Consolidations Total Revenue: Base revenue and other $ — $ — $ — $ — $ 472.6 $ 4.1 $ — $ 476.7 Metered power reimbursements — — — — 51.1 1.3 — 52.4 Revenue — — — — 523.7 5.4 — 529.1 Costs and expenses: Property operating expenses — — — — 185.2 2.3 — 187.5 Sales and marketing — — — — 16.9 — — 16.9 General and administrative — — — — 60.5 0.2 — 60.7 Depreciation and amortization — — — — 185.3 (1.4 ) — 183.9 Transaction and acquisition integration costs — — — — 4.3 — — 4.3 Asset impairments and loss on disposal — — — — 5.3 — — 5.3 Total costs and expenses — — — — 457.5 1.1 — 458.6 Operating income — — — — 66.2 4.3 — 70.5 Interest expense — — 49.1 — — 2.8 (3.1 ) 48.8 Income (loss) before income taxes — — (49.1 ) — 66.2 1.5 3.1 21.7 Income tax expense — — — — (1.8 ) — — (1.8 ) Equity (loss) earnings related to investment in subsidiaries 15.9 0.2 65.0 — 0.6 — (81.7 ) — Net income (loss) 15.9 0.2 15.9 — 65.0 1.5 (78.6 ) 19.9 Other comprehensive loss — — — — — (0.9 ) — (0.9 ) Comprehensive income (loss) attributable to common stockholders $ 15.9 $ 0.2 $ 15.9 $ — $ 65.0 $ 0.6 $ (78.6 ) $ 19.0 IN MILLIONS Year Ended December 31, 2015 Parent (1) General LP Finance Guarantor Subsidiaries Non- Eliminations/Consolidations Total Revenue: Base revenue and other $ — $ — $ — $ — $ 350.3 $ 4.3 $ — $ 354.6 Metered power reimbursements — — — — 43.5 1.2 — 44.7 Revenue — — — — 393.8 5.5 — 399.3 Costs and expenses: Property operating expenses — — — — 146.0 2.7 — 148.7 Sales and marketing — — — — 12.0 0.1 — 12.1 General and administrative — — — — 46.6 — — 46.6 Depreciation and amortization — — — — 138.7 2.8 — 141.5 Transaction and acquisition integration costs — — — — 14.1 — — 14.1 Asset impairments and loss on disposal — — — — 13.5 — — 13.5 Total costs and expenses — — — — 370.9 5.6 — 376.5 Operating income (loss) — — — — 22.9 (0.1 ) — 22.8 Interest expense — — 39.7 — — 3.2 (1.7 ) 41.2 (Loss) income before income taxes — — (39.7 ) — 22.9 (3.3 ) 1.7 (18.4 ) Income tax expense — — — — (1.8 ) — — (1.8 ) Equity (loss) earnings related to investment in subsidiaries (17.1 ) (0.2 ) 17.8 — (3.3 ) — 2.8 — Net (loss) income (17.1 ) (0.2 ) (21.9 ) — 17.8 (3.3 ) 4.5 (20.2 ) Noncontrolling interest in net loss — — — — — — 4.8 4.8 Net (loss) income attributed to common stockholders (17.1 ) (0.2 ) (21.9 ) — 17.8 (3.3 ) 9.3 (15.4 ) Other comprehensive loss — — — — — (0.2 ) — (0.2 ) Comprehensive (loss) income attributable to common stockholders $ (17.1 ) $ (0.2 ) $ (21.9 ) $ — $ 17.8 $ (3.5 ) $ 9.3 $ (15.6 ) Consolidating Statements of Cash Flows IN MILLIONS Year Ended December 31, 2017 Parent General LP Finance Guarantor Subsidiaries Non- Eliminations/Consolidations Total Net cash (used in) provided by operating activities $ — $ — $ (60.3 ) $ — $ 339.7 $ (0.6 ) $ 10.7 $ 289.5 Cash flows from investing activities: Capital expenditures - asset acquisitions, net of cash acquired — — — — (492.3 ) — — (492.3 ) Capital expenditures - other development — — — — (903.8 ) — (10.7 ) (914.5 ) Equity investment — — — — — (100.0 ) — (100.0 ) Investment in subsidiaries (705.3 ) (7.1 ) (705.3 ) — (0.7 ) — 1,418.4 — Return of investment 145.7 — — — — — (145.7 ) — Intercompany borrowings 6.5 — (598.8 ) — — 0.5 591.8 — Net cash provided by (used in) investing activities (553.1 ) (7.1 ) (1,304.1 ) — (1,396.8 ) (99.5 ) 1,853.8 (1,506.8 ) Cash flows from financing activities: Issuance of common stock 706.0 — — — — — — 706.0 Stock issuance costs (0.3 ) — — — — — — (0.3 ) Dividends paid (145.7 ) — (145.7 ) — — — 145.7 (145.7 ) Intercompany borrowings — — (6.5 ) — 598.2 — (591.7 ) — Borrowings from credit facility — — 1,390.0 — — — — 1,390.0 Payments on credit facility — — (1,275.0 ) — — — — (1,275.0 ) Payments on senior notes — — (474.8 ) — — — — (474.8 ) Proceeds from issuance of debt — — 1,217.8 — — — — 1,217.8 Debt issuance costs — — (19.0 ) — — — — (19.0 ) Payments on capital leases and lease financing arrangements — — — — (8.6 ) (1.2 ) — (9.8 ) Interest paid by lenders on issuance of the senior notes — — 2.7 — — — — 2.7 Payment of debt extinguishment costs — — (30.4 ) — — — — (30.4 ) Tax payment upon exercise of equity awards (6.9 ) — — — — — — (6.9 ) Contributions/distributions from parent — 7.1 705.3 — 605.3 100.8 (1,418.5 ) — Net cash provided by (used in) financing activities 553.1 7.1 1,364.4 — 1,194.9 99.6 (1,864.5 ) 1,354.6 Net increase (decrease) in cash, cash equivalents and restricted cash — — — — 137.8 (0.5 ) — 137.3 Cash, cash equivalents and restricted cash at beginning of period — — — — 13.4 1.2 — 14.6 Cash, cash equivalents and restricted cash at end of period $ — $ — $ — $ — $ 151.2 $ 0.7 $ — $ 151.9 IN MILLIONS Year Ended December 31, 2016 Parent General LP Finance Guarantor Subsidiaries Non- Eliminations/Consolidations Total Net cash (used in) provided by operating activities $ — $ — $ (45.4 ) $ — $ 221.8 $ — $ 4.2 $ 180.6 Cash flows from investing activities: Capital expenditures - asset acquisitions, net of cash acquired — — — — (131.1 ) — — (131.1 ) Capital expenditures - other development — — — — (598.9 ) (1.1 ) — (600.0 ) Investment in subsidiaries (448.2 ) (4.5 ) (448.2 ) — — — 900.9 — Return of investment 112.3 — — — — — (112.3 ) — Intercompany borrowings 15.3 — (66.3 ) — — (0.5 ) 51.5 — Net cash provided by (used in) investing activities (320.6 ) (4.5 ) (514.5 ) — (730.0 ) (1.6 ) 840.1 (731.1 ) Cash flows from financing activities: Issuance of common stock 448.7 — — — — — — 448.7 Stock issuance costs (1.6 ) — — — — — — (1.6 ) Dividends paid (112.3 ) — (114.3 ) — — — 112.3 (114.3 ) Intercompany borrowings — — (15.3 ) — 71.0 — (55.7 ) — Borrowings from credit facility — — 710.0 — — — — 710.0 Payments on credit facility — — (460.0 ) — — — — (460.0 ) Payments on capital leases and lease financing arrangements — — — — (8.0 ) (1.1 ) — (9.1 ) Tax payment upon exercise of equity awards (14.2 ) — — — — — — (14.2 ) Contributions/distributions from parent — 4.5 448.2 — 448.2 — (900.9 ) — Payment of note payable — — — — (1.5 ) — — (1.5 ) Debt issuance costs — — (8.7 ) — — — — (8.7 ) Net cash provided by (used in) financing activities 320.6 4.5 559.9 — 509.7 (1.1 ) (844.3 ) 549.3 Net increase (decrease) in cash, cash equivalents and restricted cash — — — — 1.5 (2.7 ) — (1.2 ) Cash, cash equivalents and restricted cash at beginning of period — — — — 11.9 3.9 — 15.8 Cash, cash equivalents and restricted cash at end of period $ — $ — $ — $ — $ 13.4 $ 1.2 $ — $ 14.6 IN MILLIONS Year Ended December 31, 2015 Parent Guarantor General Partner LP Co-issuer Finance Co-issuer Guarantor Subsidiaries Non- Guarantors Eliminations/Consolidations Total Net cash (used in) provided by operating activities $ — $ — $ (19.6 ) $ — $ 156.2 $ 1.9 $ 1.7 $ 140.2 Cash flows from investing activities: Capital expenditures - purchase of fixed assets — — — — (17.3 ) — — (17.3 ) Capital expenditures - other development — — — — (216.7 ) (0.5 ) — (217.2 ) Business acquisition, net of cash acquired — — — — (389.6 ) — — (389.6 ) Investment in subsidiaries (203.1 ) (2.0 ) (203.1 ) — (0.4 ) — 408.6 — Return of investment 62.6 — 102.0 — (17.9 ) — (146.7 ) — Intercompany borrowings — — (348.4 ) — — — 348.4 — Net cash (used in) provided by investing activities (140.5 ) (2.0 ) (449.5 ) — (641.9 ) (0.5 ) 610.3 (624.1 ) Cash flows from financing activities: Issuance of common stock 799.5 — — — — — — 799.5 Stock issuance costs (0.8 ) — — — — — — (0.8 ) Acquisition of operating partnership units (596.4 ) — — — — — — (596.4 ) Dividends paid (61.0 ) — (80.8 ) — (80.8 ) — 141.8 (80.8 ) Intercompany borrowings — — — — 348.4 — (348.4 ) — Borrowings from credit facility — — 260.0 — — — — 260.0 Proceeds from issuance of debt — — 103.8 — — — — 103.8 Payments on credit facility — — (10.0 ) — — — — (10.0 ) Payments on capital leases and lease financing arrangements — — — — (5.0 ) (0.9 ) — (5.9 ) Tax payment upon exercise of equity awards (0.8 ) — — — — — — (0.8 ) Contributions/distributions from parent — 2.0 201.5 — 201.5 0.4 (405.4 ) — Debt issuance costs — — (5.4 ) — — — — (5.4 ) Net cash provided by (used in) financing activities 140.5 2.0 469.1 — 464.1 (0.5 ) (612.0 ) 463.2 Net (decrease) increase in cash, cash equivalents and restricted cash — — — — (21.6 ) 0.9 — (20.7 ) Cash, cash equivalents and restricted cash at beginning of period — — — — 33.5 3.0 — 36.5 Cash, cash equivalents and restricted cash at end of period $ — $ — $ — $ — $ 11.9 $ 3.9 $ — $ 15.8

Quarterly Financial Information

Quarterly Financial Information (Unaudited)	12 Months Ended
	Dec. 31, 2017
Quarterly Financial Information Disclosure [Abstract]
Quarterly Financial Information (Unaudited)	Quarterly Financial Information (Unaudited) The table below reflects the unaudited selected quarterly information for the years ended December 31, 2017 and 2016 : IN MILLIONS, except per share amounts 2017 First Quarter Second Quarter Third Quarter Fourth Total Revenue $ 149.3 $ 166.9 $ 175.3 $ 180.5 $ 672.0 Operating income (loss) 19.8 16.7 (36.3 ) 23.9 24.1 Net (loss) income (30.4 ) (0.8 ) (55.1 ) 2.8 (83.5 ) Net (loss) income attributed to common shareholders (30.4 ) (0.8 ) (55.1 ) 2.8 (83.5 ) Basic and diluted (loss) income per share $ (0.36 ) $ (0.01 ) $ (0.61 ) $ 0.03 $ (0.95 ) IN MILLIONS, except per share amounts 2016 First Second Quarter Third Quarter Fourth Quarter Total Revenue $ 117.8 $ 130.1 $ 143.8 $ 137.4 $ 529.1 Operating income 17.9 21.1 18.8 12.7 70.5 Net income 5.6 9.1 4.4 0.8 19.9 Net income attributed to common stockholders 5.6 9.1 4.4 0.8 19.9 Basic and diluted income per share $ 0.07 $ 0.11 $ 0.05 $ 0.01 $ 0.24

Schedule II. Valuation and Qual

Schedule II. Valuation and Qualifying Accounts	12 Months Ended
	Dec. 31, 2017
Valuation and Qualifying Accounts [Abstract]
Schedule II. Valuation and Qualifying Accounts	Schedule II. Valuation and Qualifying Accounts Beginning Charge (Deductions)/ End (dollars in millions) of Period to Expenses Additions of Period Allowance for Doubtful Accounts 2017 $ 2.1 $ 0.2 $ (0.2 ) $ 2.1 2016 1.0 1.6 (0.5 ) 2.1 2015 1.0 — — 1.0 Deferred Tax Valuation Allowance 2017 $ 6.5 $ 0.7 $ — $ 7.2 2016 6.3 0.2 — 6.5 2015 5.7 0.6 — 6.3

Schedule III. Real Estate Prope

Schedule III. Real Estate Properties and Accumulated Depreciation	12 Months Ended
	Dec. 31, 2017
SEC Schedule III, Real Estate and Accumulated Depreciation Disclosure [Abstract]
Schedule III. Real Estate Properties and Accumulated Depreciation	Schedule III. Real Estate Properties and Accumulated Depreciation CyrusOne Inc. As of December 31, 2017 (dollars in millions) Initial Costs Cost Capitalized Subsequent to Acquisition Gross Carrying Amount Description Land Building and Improvements Equipment Land Building and Improvements Equipment Land Building and Improvements Equipment Accumulated Depreciation Acquisition Dallas - Carrollton $ 16.1 $ — $ — $ — $ 61.8 $ 210.7 $ 16.1 $ 61.8 $ 210.7 $ 76.7 2012 Houston - Houston West I 1.4 21.4 0.1 — 63.8 49.7 1.4 85.2 49.8 73.7 2010 Cincinnati - 7th Street 0.9 42.2 — — 68.4 33.1 0.9 110.6 33.1 86.5 1999 Dallas - Lewisville — 46.2 2.2 — 30.5 35.2 — 76.7 37.4 62.0 2010 Northern Virginia - Sterling II — — — — 28.8 112.3 — 28.8 112.3 16.4 2013 Somerset I 12.1 124.6 83.3 — 0.2 0.4 12.1 124.8 83.7 12.2 2017 Chicago - Aurora I 2.4 26.0 97.3 — 6.4 27.7 2.4 32.4 125.0 24.0 2016 Totowa - Madison — 28.3 45.6 — 0.2 9.5 — 28.5 55.1 20.4 2015 Cincinnati - North Cincinnati 4.0 12.3 — 65.1 9.9 4.0 77.4 9.9 37.0 2008 San Antonio III — — — — 40.3 96.8 — 40.3 96.8 9.0 2017 Houston - Houston West II 2.0 — — 0.8 22.8 50.1 2.8 22.8 50.1 28.0 2013 Wappingers Falls I — 9.9 13.3 — 1.4 4.7 — 11.3 18.0 9.5 2015 San Antonio I 4.6 3.0 — — 28.7 34.8 4.6 31.7 34.8 26.2 2011 Phoenix - Chandler II — — — — 16.2 38.9 — 16.2 38.9 15.6 2014 Northern Virginia - Sterling I 6.9 — — 0.1 20.0 59.4 7.0 20.0 59.4 18.1 2013 Raleigh-Durham I 2.1 73.5 71.3 — 4.5 4.7 2.1 78.0 76.0 9.8 2017 Houston - Galleria — 56.0 2.0 — 12.6 15.6 — 68.6 17.6 49.1 2010 Phoenix - Chandler I 14.8 — — — 58.2 65.9 14.8 58.2 65.9 36.5 2011 Phoenix - Chandler III — 0.9 2.5 — 10.5 47.5 — 11.4 50.0 6.4 2016 Northern Virginia - Sterling III — — — — 22.2 61.3 — 22.2 61.3 6.2 2017 Austin II 2.0 — — — 23.4 7.0 2.0 23.4 7.0 14.5 2011 San Antonio II 6.7 — — 0.3 29.0 60.4 7.0 29.0 60.4 10.4 2013 Florence 2.2 7.7 — — 34.3 5.3 2.2 42.0 5.3 28.5 2005 Phoenix - Chandler IV — — — — 18.3 40.9 — 18.3 40.9 2.2 2017 Cincinnati - Hamilton — 9.5 — — 40.7 6.0 — 50.2 6.0 36.2 2007 London - Great Bridgewater — 16.5 — — 11.9 1.1 — 28.4 1.1 3.8 2011 Northern Virginia - Sterling IV 4.6 9.6 0.1 — 10.4 73.6 4.6 20.0 73.7 5.6 2016 Cincinnati - Mason — — — — 20.3 1.6 — 20.3 1.6 13.8 2004 Dallas - Midway — 1.8 — — 0.2 0.4 — 2.0 0.4 2.3 2010 Phoenix - Chandler VI 10.5 — — — 15.7 49.2 10.5 15.7 49.2 1.3 2016 Stamford - Riverbend* — 4.3 13.2 — (1.4 ) (6.3 ) — 2.9 6.9 3.2 2015 Norwalk I* — 18.3 25.3 — (4.8 ) (15.9 ) — 13.5 9.4 2.9 2015 Dallas - Marsh — — — — 0.1 0.6 — 0.1 0.6 0.6 2010 Chicago - Lombard 0.7 3.2 — — 1.5 7.7 0.7 4.7 7.7 6.0 2008 Stamford - Omega* — 3.2 0.6 — (0.6 ) 0.1 — 2.6 0.7 0.5 2015 Totowa - Commerce — 4.1 0.8 — — 0.8 — 4.1 1.6 0.9 2015 Cincinnati - Blue Ash* — 2.6 — — (1.9 ) 0.2 — 0.7 0.2 0.4 2009 South Bend - Crescent — 1.1 — — 0.6 0.1 — 1.7 0.1 1.8 2008 Houston - Houston West III 18.3 — — 0.1 17.9 30.7 18.4 17.9 30.7 5.9 2013 Singapore - Inter Business Park* — 9.0 — — (9.0 ) — — — — — 2011 South Bend - Monroe — — — — 2.5 0.3 — 2.5 0.3 1.6 2007 Cincinnati - Goldcoast* 0.6 — — (0.4 ) 4.0 0.1 0.2 4.0 0.1 3.0 2007 Austin III 3.3 — — — 10.6 33.9 3.3 10.6 33.9 6.8 2015 Northern Virginia - Sterling V 24.1 — — — 35.7 108.8 24.1 35.7 108.8 4.1 2016 Phoenix - Chandler V — — — — 5.9 20.5 — 5.9 20.5 0.3 2017 San Antonio IV — — — — — 17.9 — — 17.9 0.9 2017 Austin Land A 7.9 — — 0.1 — 0.2 8.0 — 0.2 0.1 2013 Chicago - Aurora II 2.6 — — — 8.3 42.9 2.6 8.3 42.9 1.5 2016 Chicago - Aurora Land B 5.1 — — — — — 5.1 — — — 2016 Dallas - Allen 12.0 — — — — — 12.0 — — — 2017 (dollars in millions) Initial Costs Cost Capitalized Subsequent to Gross Carrying Amount Description Land Building and Equipment Land Building and Equipment Land Building and Equipment Accumulated Acquisition Quincy Land A 3.1 — — — — — 3.1 — — — 2017 Atlanta I 5.1 — — — — — 5.1 — — — 2017 $ 176.1 $ 535.2 $ 357.6 $ 1.0 $ 836.2 $ 1,456.3 $ 177.1 $ 1,371.4 $ 1,813.9 $ 782.4 The aggregate cost of the total properties for federal income tax purposes was $4,257.7 million at December 31, 2017 . In addition, Construction in progress was $478.4 million as we continue to build data center facilities. * Reductions in Cost Capitalized Subsequent to Acquisition due to impairment losses recorded for the respective facility. Historical Cost and Accumulated Depreciation and Amortization The following table reconciles the historical cost and accumulated depreciation for the years ended December 31, 2017 , 2016 and 2015 . Years Ended December 31, (amounts in millions) 2017 2016 2015 Property Balance—beginning of period $ 2,601.6 $ 1,827.6 $ 1,378.4 Disposals (3.4 ) (12.0 ) (7.0 ) Impairments (71.8 ) (4.9 ) (9.3 ) Additions (acquisitions and improvements) 1,314.4 790.9 465.5 Balance, end of period $ 3,840.8 $ 2,601.6 $ 1,827.6 Accumulated Depreciation Balance—beginning of period $ 578.5 $ 435.6 $ 327.0 Disposals (1.9 ) (7.9 ) (2.7 ) Impairments (14.1 ) — — Additions (depreciation and amortization expense) 219.9 150.8 111.3 Balance, end of period $ 782.4 $ 578.5 $ 435.6

Significant Accounting Polici33

Significant Accounting Policies (Policies)	12 Months Ended
	Dec. 31, 2017
Accounting Policies [Abstract]
Basis of Presentation	The accompanying financial statements as of December 31, 2017 and December 31, 2016 , and for the years ended December 31, 2017 , December 31, 2016 and December 31, 2015 , are prepared on a consolidated basis. In addition, the accompanying financial statements have been prepared in accordance with accounting principles generally accepted in the United States of America (GAAP). All intercompany transactions and balances have been eliminated in consolidation. All prior year amounts have been presented to conform to current year's presentation. Base revenue and other, and metered power reimbursements for the years ended December 31, 2016 and 2015 have been presented separately to conform with the presentation for the year ended December 31, 2017. There is no change to total revenue as a result of this change in presentation. We adopted ASU No. 2016-18, Restricted Cash, during 2017 (See Note 5 for additional details). The statement of cash flows for prior periods has been presented to conform to the current year's presentation.
Use of Estimates	Use of Estimates —Preparation of the consolidated financial statements in conformity with GAAP requires management to make estimates and assumptions that affect the amounts reported in the consolidated financial statements and accompanying notes. These estimates and assumptions are based on management’s knowledge of current events and actions that we may undertake in the future. Estimates are used in determining the fair value of leased real estate, including purchase price allocations for business combinations and asset acquisitions, the useful lives of real estate and other long-lived assets, future cash flows associated with goodwill and other long-lived asset impairment testing, deferred tax assets and liabilities, available-for-sale securities and loss contingencies. Actual results may differ from these estimates and assumptions.
Investments in Real Estate	Investment in Real Estate —Investment in real estate consist of land, buildings, improvements and integral equipment utilized in our data center operations. Real estate acquired from third parties has been recorded at its acquisition cost. Additions and improvements which extend an asset’s useful life or increase its functionality are capitalized and depreciated over the asset’s remaining life. Maintenance and repairs are expensed as incurred. When we are involved in the construction of structural improvements to leased property, we are deemed the accounting owner of the leased real estate. In these instances, we bear substantially all the construction period risk, including managing or funding construction. As we have substantially all of the construction risks, we are deemed the “owner” of the asset under construction for accounting purposes during the construction period, and are therefore required to capitalize the construction costs on the accompanying consolidated balance sheets. At inception, the fair value of the building, excluding land, is recorded as an asset, and the construction and modification costs to the building that are not funded by us would be recorded as a liability. As construction progresses, the value of the asset and obligation increases by the fair value of the structural improvements. At completion of the construction, Sales-Leaseback Accounting under ASC 840-40-25 is also evaluated. Due to our continuing involvement with the lessor, Sales-Leaseback Accounting is precluded and the liability is not derecognized. When the asset is placed in service, depreciation commences, and the leased real estate is depreciated to the lesser of (i) its estimated fair value at the end of the term or (ii) the expected amount of the unamortized obligation at the end of the term. The associated obligation is presented as Lease financing arrangements in the accompanying consolidated balance sheets. When we are not deemed the accounting owner of leased real estate, we further evaluate the lease to determine whether the lease should be classified as a capital or operating lease. One of the following four characteristics must be present to classify a lease as a capital lease: (i) the lease transfers ownership of the property to the lessee by the end of the lease term, (ii) the lease contains a bargain purchase option, (iii) the lease term is equal to 75% or more of the estimated economic life of the leased property or (iv) the net present value of the lease payments is at least 90% of the fair value of the leased property. Construction in progress includes direct and indirect expenditures for the construction and expansion of our data centers and is stated at its acquisition cost. Independent contractors perform substantially all of the construction and expansion efforts of our data centers. Construction in progress includes costs incurred under construction contracts including project management services, engineering and schematic design services, design development, construction services and other construction-related fees and services. Interest, property taxes and certain labor costs are also capitalized during the construction of an asset. These costs are depreciated over the estimated useful life of the related assets. Capitalized interest in 2017 , 2016 , and 2015 was $17.0 million , $10.6 million , and $6.1 million , respectively. Depreciation is calculated using the straight-line method over the estimated useful life of the asset. Useful lives range from nine to thirty years for buildings, three to thirty years for building improvements, and two to twenty years for equipment. Leasehold improvements are amortized over the shorter of the asset’s useful life or the remaining lease term, including renewal options which are reasonably assured. Management reviews the carrying value of long-lived assets, including intangible assets with finite lives, when events or changes in circumstances indicate that the carrying amount of the assets may not be recoverable. Examples of such indicators may include a significant adverse change in the extent to which or manner in which the property is being used, an accumulation of costs significantly in excess of the amount originally expected for acquisition or development, or a history of operating or cash flow losses. When such indicators exist, we review an estimate of the undiscounted future cash flows expected to result from the use of an asset (or group of assets) and its eventual disposition and compare such amount to its carrying amount. We consider factors such as future operating income, leasing demand, competition and other factors. If our undiscounted net cash flows indicate that we are unable to recover the carrying value of the asset, an impairment loss is recognized. An impairment loss is measured as the amount by which the asset’s carrying value exceeds its estimated fair value.
Business Combinations and Asset Acquisitions	Business Combinations and Asset Acquisitions —The Company applies the purchase method for business combinations, where all tangible and identifiable intangible assets acquired and all liabilities assumed are recorded at fair value. Any excess purchase price is recorded as goodwill. Transaction costs associated with business combinations are expensed as incurred. Revenues and the results of operations of the acquired business are included in the accompanying consolidated financial statements commencing on the date of acquisition. The Company applies a screen test to determine when a set is not a business. When substantially all of the fair value of the gross assets acquired (or disposed of) is concentrated in a single identifiable asset or a group of similar identifiable assets, the set is not a business. Upon adoption of ASU 2017-01, Business Combinations, most acquisitions of investment properties will meet the definition of an asset. Purchase price paid for assets acquired is allocated between identified tangible and intangible assets acquired. Transaction costs associated with asset acquisitions are capitalized. Revenues and the results of operations of the acquired assets are included in the accompanying consolidated financial statements commencing on the date of the asset acquisition. The Company early adopted ASU 2017-01, Business Combinations, on January 1, 2017.
Cash and Cash Equivalents	Cash and Cash Equivalents —Cash and cash equivalents include all non-restricted cash held in financial institutions and other non-restricted highly liquid short-term investments with original maturities at acquisition of three months or less.
Restricted Cash	Restricted Cash —Restricted cash includes cash equivalents held to collateralize standby letters of credit and/or deposited in escrow to fund construction or pending potential acquisition transactions. In addition, we may have other cash that is not immediately available for use in current operations.
Goodwill	Goodwill —We evaluate goodwill for possible impairment at least annually or upon the occurrence of a triggering event. A triggering event is an event or circumstance that would more likely than not reduce the fair value of a reporting unit below its carrying amount, including sales of properties defined as businesses for which the relative size of the sold property is significant to the reporting unit, that could impact our goodwill impairment calculations. For our annual impairment evaluation, we have the option of performing a qualitative or quantitative goodwill impairment analysis. A qualitative analysis, Step zero, analyzes the macro-economic environment in which we operate for any significant changes such as deterioration in the market that the Company operates or overall financial performance such as declining cash flows. Also, entity specific changes are analyzed such as change in management, strategy or composition of reporting unit. A quantitative analysis, Step one, requires the Company to estimate the fair value of the reporting unit and compare the fair value to the carrying value to identify whether the value of the recorded goodwill is impaired. Changes in certain assumptions could have a significant impact on the impairment test for goodwill under Step one. The most critical assumptions are projected future growth rates, operating margins, capital expenditures, tax rates, terminal values and discount rates. These assumptions are subject to change as our long-term plans and strategies are updated each year. In January 2017, the FASB issued ASU 2017-04 in order to simplify the test for goodwill impairment by eliminating Step 2, which measures a goodwill impairment loss by comparing the implied fair value of a reporting unit's goodwill with the carrying amount of that goodwill. Under the amendments in this update, an entity should perform its annual goodwill impairment test by comparing the fair value of a reporting unit with its carrying amount and should recognize an impairment charge for the amount by which the carrying amount exceeds the reporting unit's fair value. However, the loss recognized should not exceed the total amount of goodwill allocated to that reporting unit. Early adoption is permitted. We adopted this standard on January 1, 2017. During the fourth quarter of 2017 and 2016, we applied Step zero and determined that it is more likely than not that the fair value of the reporting unit is more than the carrying amount and therefore determined that the two step method for goodwill impairment testing was not necessary. During the fourth quarter of 2015, we performed a detailed, quantitative assessment. Based on the Company's annual assessment of goodwill, no impairment has been recognized through December 31, 2017.
Long-Lived and Intangible Assets	Long-Lived and Intangible Assets —Intangible assets represent purchased assets that lack physical substance, but can be separately distinguished from goodwill because of contractual or other legal rights or because the asset is capable of being sold or exchanged, either on its own or in combination with a related contract, asset, or liability. Intangible assets with finite lives consist of trademarks, a trade name, customer relationships, and a favorable leasehold interest.
Rent and Other Receivables	Rent and Other Receivables —Receivables consist principally of trade receivables from customers and are generally unsecured and due within 30 to 120 days . Unbilled receivables arise from services rendered but not yet billed. Expected credit losses associated with trade receivables are recorded as an allowance for doubtful accounts. The allowance for doubtful accounts is estimated based upon historic patterns of credit losses for aged receivables as well as specific provisions for certain identifiable, potentially uncollectible balances. When internal collection efforts on accounts have been exhausted, the accounts are written-off and the associated allowance for doubtful accounts is reduced.
Deferred Leasing and Financing Costs	Deferred Leasing Costs —Deferred leasing costs are presented with Other assets in the accompanying consolidated balance sheets. Leasing commissions incurred at the commencement of a new lease are capitalized and amortized over the average term of the customer lease. Amortization of deferred leasing costs is presented with Depreciation and amortization in the accompanying consolidated statements of operations. If a lease terminates prior to the expiration of the lease, the remaining unamortized cost is written off to amortization expense. As of December 31, 2017 and 2016 , deferred leasing costs were $32.6 million and $23.3 million , respectively. Amortization expense was $7.6 million , $6.1 million and $5.2 million for the years ended December 31, 2017 , 2016 and 2015 , respectively. Deferred Financing Costs —Deferred financing costs include costs incurred in connection with issuance of debt, including our senior notes, term loans and revolving credit facilities. These costs are presented in the balance sheet as a direct reduction from the carrying amount of the debt liability. These financing costs are deferred and amortized to expense over the term of the instrument and are included as a component of Interest expense.
Lease Financing Arrangements	Lease Financing Arrangements —Lease financing arrangements represent leases of real estate where we are involved in the construction of structural improvements to develop buildings into data centers. When we bear substantially all the construction period risk, such as managing or funding construction, we are deemed to be the accounting owner of the leased property and, at the lease inception date, we are required to record at fair value the property and associated liability on our consolidated balance sheets. These transactions generally do not qualify for sale-leaseback accounting due to our continued involvement in these data center operations.
Revenue Recognition	Revenue Recognition —Colocation rentals are generally billed monthly in advance, and some contracts have escalating payments over the term of the contract. If rents escalate without the lessee gaining access to or control over additional leased space or power, and the lessee takes possession of, or controls the physical use of the property (including all contractually committed power) at the beginning of the lease term, the rental payments by the lessee are recognized as revenue on a straight-line basis over the term of the lease. If rents escalate because the lessee gains access to and control over additional leased space or power, revenue is recognized in proportion to the additional space or power in the periods that the lessee has control over the use of the additional space or power. The excess of revenue recognized over amounts contractually due is recognized in Other assets in the accompanying consolidated balance sheets. As of December 31, 2017 and 2016 , straight-line rent receivable was $100.0 million and $67.6 million , respectively. Revenue is recognized for services or products that are deemed separate units of accounting. When a customer makes an advance payment or they are contractually obligated to pay any amounts in advance, which is not deemed a separate unit of accounting, Deferred revenue liability is recorded. This revenue is recognized ratably over the expected term of the lease, unless the pattern of service suggests otherwise. As of December 31, 2017 and 2016 , Deferred revenue was $111.6 million and $76.7 million , respectively. Some of our leases are structured on a full-service gross basis in which the customer pays a fixed amount for both colocation rent and power. Other leases provide that the customer will be billed for power based upon actual usage which is separately metered. Power is generally billed one month in arrears, and an estimate of this revenue is accrued in the month that the associated costs are incurred. In certain leases, we receive an administrative fee when we manage the meters for our customers. We generally are not entitled to reimbursements for real estate taxes, insurance or other operating expenses. Certain customer leases require specified levels of service or performance. If we fail to meet these service levels, our customers may be eligible to receive credits on their contractual billings. These credits are recognized against revenue when an event occurs that gives rise to such credits. Customer credits were immaterial for each of the years presented. A provision for doubtful accounts is recognized when the collection of contractual rent, straight-line rent or customer reimbursements are deemed to be uncollectible.
Sales and Marketing Expense	Sales and Marketing Expense —Sales and marketing expense is comprised of compensation and benefits associated with Sales and marketing personnel as well as advertising and marketing costs. Costs related to advertising expense were $2.4 million , $4.1 million and $2.2 million for the years ended December 31, 2017 , 2016 and 2015 , respectively.
Depreciation and Amortization Expense	Depreciation and Amortization Expense —Depreciation expense is recognized over the estimated useful lives of real estate applying the straight-line method. The useful life of leased real estate and leasehold improvements is the lesser of the economic useful life of the asset or the term of the lease, including optional renewal periods if renewal of the lease is reasonably assured. The residual value of leased real estate is estimated as the lesser of (i) the expected fair value of the asset at the end of the lease term or (ii) the expected amount of the unamortized liability at the end of the lease term. Estimated useful lives are periodically reviewed. Depreciation expense was $226.2 million , $157.7 million and $117.8 million for the years ended December 31, 2017 , 2016 and 2015 , respectively. Amortization expense is recognized over the estimated useful lives of finite-lived intangibles. Finite-lived intangibles include trademarks, customer relationships, favorable leasehold interests, in-place leases, trade names and deferred leasing costs.
Transaction and Acquisition Integration Costs	Transaction and Acquisition Integration Costs —Transaction costs represent incremental legal, accounting and professional fees incurred in connection with consummated business combinations; integration costs post an asset acquisition; and costs associated with diligence efforts on certain targeted and unrealized acquisitions. Integration costs represent incremental costs to integrate a consummated acquisition. These costs are expensed as incurred and do not include any recurring costs from our ongoing operations.
Income Taxes	Income Taxes —The income tax provision consists of an amount for taxes currently payable and an amount for tax consequences deferred to future periods. CyrusOne Inc. has elected to be taxed as a REIT under the Internal Revenue Code of 1986, as amended (the Code), commencing with our initial taxable year ending December 31, 2013. Provided we continue to meet the various qualification tests mandated under the Code, we are generally not subject to corporate level federal income tax on the earnings distributed currently to our stockholders. If we fail to qualify as a REIT in any taxable year, our taxable income will be subject to federal income tax at regular corporate rates and, for taxable years beginning prior to January 1, 2018, any applicable alternative minimum tax, and we may not be able to qualify as a REIT for four subsequent taxable years. While CyrusOne Inc. and the operating partnership do not pay federal income taxes, we are still subject to foreign, state and local income taxes in the locations in which we conduct business. Our taxable REIT subsidiaries (each a TRS) are also subject to federal and state income taxes to the extent they earn taxable income. Deferred income taxes are recognized in certain entities. Deferred income taxes are provided for temporary differences in the basis between financial statement and income tax assets and liabilities. Deferred income taxes are recalculated annually at rates then in effect. Valuation allowances are recorded to reduce deferred tax assets to amounts that are more likely than not to be realized. The ultimate realization of the deferred tax assets depends upon our ability to generate future taxable income during the periods in which basis differences and other deductions become deductible and prior to the expiration of the net operating loss carryforwards. The Company and its subsidiaries file income tax returns in the U.S. federal jurisdiction as well as various foreign, state and local jurisdictions. The Company's previous tax filings are subject to normal reviews by regulatory agencies until the related statute of limitations expires. With a few exceptions, the Company is no longer subject to U. S. federal, state or local examinations for years prior to 2012, and we have no liabilities for uncertain tax positions as of December 31, 2017 or 2016 .
Foreign Currency Translation and Transactions	Foreign Currency Translation and Transactions —The financial position of foreign subsidiaries is translated at the exchange rates in effect at the end of the period, while revenues and expenses are translated at average rates of exchange during the period. Gains or losses from translation of foreign operations where the local currency is the functional currency are included as components of other comprehensive (loss) income. Gains or losses from foreign currency transactions are included in determining net (loss) income.
Comprehensive (Loss) Income	Comprehensive (Loss) Income —Comprehensive (loss) income represents the change in net assets of a company from transactions and other events from nonowner sources. Comprehensive (loss) income comprises all components of net (loss) income and all components of other comprehensive (loss) income.
(Loss)/Income Per Share	(Loss)/Income Per Share —Basic EPS includes only the weighted average number of common shares outstanding during the period. Diluted EPS includes the weighted average number of common shares and the dilutive effect of stock options, restricted stock and share unit awards outstanding during the period, when such instruments are dilutive. All outstanding unvested share-based payment awards that contain rights to nonforfeitable dividends are treated as participating in undistributed earnings with common shareholders. Awards of this nature are considered participating securities and the two-class method of computing basic and diluted EPS is applied.
Stock-Based Compensation	Stock-Based Compensation —Our board of directors adopted the 2012 Long-Term Incentive Plan (LTIP), which was amended and restated by our stockholders on May 2, 2016. The LTIP is administered by the compensation committee of the board of directors. Awards issuable under the LTIP include common stock, restricted stock, restricted stock units, stock options and other incentive awards. See Note 17 for additional details relating to these awards. Share-based compensation expense is based on the estimated grant-date fair value. CyrusOne Inc. recognizes share-based compensation expense on a straight-line basis over the requisite service period for time-based awards and on a graded vesting basis for performance-based awards. We adopted ASU No. 2016-09, Improvements to Employee Share-Based Payment Accounting (Subtopic 718) in the fourth quarter of 2016 and elected to account for forfeitures as they occur. Prior to the adoption of this ASU, CyrusOne estimated forfeitures based on historical activity, expected employee turnover, and other qualitative factors which were adjusted for changes in estimates and award vesting. CyrusOne Inc. uses the Black-Scholes-Merton option pricing model to calculate the fair value of stock options. This option valuation model requires the use of subjective assumptions, including the estimated fair value of the underlying common stock, the expected stock price volatility, and the expected term of the option. The estimated fair value of the underlying common stock is based on third-party valuations. Our volatility estimates are based on a peer group of companies. We estimate the expected term of the awards to be the weighted average mid-point between the vesting date and the end of the contractual term. For interim and annual periods, we use our year-to-date actual results, financial forecasts, and other available information to estimate the probability of the award vesting based on the performance metrics.
Fair Value Measurements	Fair Value Measurements —Fair value measurements are utilized in accounting for business combinations, testing of goodwill and other long-lived assets for impairment, recording unrealized gain/loss on available-for-sale securities and disclosures. Fair value of financial and non-financial assets and liabilities is defined as an exit price, representing the amount that would be received to sell an asset or paid to transfer a liability in an orderly transaction between market participants. The three-tier hierarchy for inputs used in measuring fair value, which prioritizes the inputs used in the methodologies of measuring fair value for asset and liabilities, is as follows: Level 1—Observable inputs for identical instruments such as quoted market prices; Level 2—Inputs include quoted prices for similar assets and liabilities in active markets, quoted prices for identical or similar assets or liabilities in markets that are not active, inputs other than quoted prices that are observable for the asset or liability (i.e., interest rates, yield curves, etc.), and inputs that are derived principally from or corroborated by observable market data by correlation or other means (market corroborated inputs); and Level 3—Unobservable inputs that reflect our determination of assumptions that market participants would use in pricing the asset or liability. These inputs are developed based on the best information available, including our own data.
Business Segments	Business Segments —Business segments are components of an enterprise for which separate financial information is available and regularly viewed by the chief operating decision maker to assess performance and allocate resources. Our chief operating decision maker, the Company's Chief Executive Officer, reviews our financial information on an aggregate basis. Furthermore, our data centers have similar economic characteristics and customers across all geographic locations, and our service offerings have similar production processes, deliver services in a similar manner and use the same types of facilities and similar technologies. As a result, we have concluded that we have one reportable business segment. For the year ended December 31, 2017 , one customer, Microsoft Corporation, represented approximately 18% of our revenue.
Recently Issued Accounting Standards	Recently Issued Accounting Standards Accounting Standards Update (ASU) No. 2014-09 (ASU 2014-09), Revenue from Contracts with Customers (Topic 606), as amended. On May 28, 2014, the Financial Accounting Standards Board (FASB) issued ASU 2014-09, which supersedes the revenue recognition requirements in Topic 605, "Revenue Recognition" and most industry-specific guidance. The core principle of ASU 2014-09 is that a company will recognize revenue when it transfers promised goods or services to customers in an amount that reflects the consideration to which the company expects to be entitled in exchange for those goods or services. On July 9, 2015, the FASB deferred the effective date of ASU 2014-09. The new revenue standard is effective for fiscal years, and interim periods within those years, beginning after December 15, 2017 (January 1, 2018 for CyrusOne) and allows either a full retrospective adoption to all periods presented or a modified retrospective adoption approach with the cumulative effect of initial application of the revised guidance recognized at the date of initial application. We are continuing to evaluate the impact of ASU 2014-09 on our consolidated financial statements. We have identified each of our revenue streams and developed views of how they will be impacted by this adoption. Our evaluation is that the timing of revenue recognition for our various revenue streams would not be materially impacted by the adoption of this standard. As we continue our assessment we are reviewing, in detail, selected revenue contracts to verify and support our initial conclusions. We will adopt the modified retrospective approach with any cumulative effect recognized in retained earnings on the date of adoption which is expected to be immaterial. We will be adopting this Standard with an effective date of January 1, 2018. ASU No. 2016-01 (ASU 2016-01), Financial Instruments - Overall (Topic 825-10) On January 5, 2016, the FASB issued ASU 2016-01. Equity investments (except those accounted for under the equity method of accounting or those that result in consolidation of the investee) are to be measured at fair value with changes in fair value recognized in net income. However, an entity may choose to measure equity investments that do not have readily determinable fair values at cost minus impairment, if any, plus or minus changes resulting from observable price changes in orderly transactions for the identical or a similar investment of the same issuer. Equity investments without readily determinable fair values are to be assessed for impairment using a quantitative approach. ASU 2016-01 should be applied by means of a cumulative-effect adjustment to the balance sheet as of the beginning of the fiscal year of adoption. The guidance is effective for annual periods beginning after December 15, 2017. The adoption of 2016-01 could have a material impact for our financial statements. In 2017 we recorded an increase to the value of our equity method investment due to an unrealized gain of $75.6 million which is recorded in Accumulated other comprehensive income (loss) in the consolidated balance sheets. ASU No. 2016-02 (ASU 2016-02), Leases (Topic 842) On February 25, 2016, the FASB issued ASU 2016-02. Lessees will need to recognize on their balance sheet a right-of-use asset and a lease liability for virtually all of their leases (other than leases that meet the definition of a short-term lease). The liability will be equal to the present value of lease payments. The asset will be based on the liability, adjusted for any initial direct costs of the lease, lease incentives or early lease payments, where applicable. For income statement purposes, the FASB retained a dual model, requiring leases to be classified as either operating or finance. Operating leases will result in straight-line expense (similar to current operating leases) while finance leases will result in a front-loaded expense pattern (similar to current capital leases). Classification will be based on criteria that are largely similar to those applied in current lease accounting. The standard is effective for CyrusOne beginning January 1, 2019. Early adoption is permitted. The new standard must be adopted using a modified retrospective transition, and provides for certain practical expedients. Transition will require application of the new guidance at the beginning of the earliest comparative period presented. We are beginning to evaluate the impact of ASU 2016-02 on our consolidated financial statements and plan to adopt the standard on January 1, 2019. ASU 2016-02 originally stated that companies would be required to bifurcate certain lease revenues between lease and non-lease components, however, the FASB issued an exposure draft in January 2018 (2018 Exposure Draft) which, if adopted as written, would allow lessors a practical expedient by class of underlying assets to account for lease and non-lease components as a single lease component if certain criteria are met. Additionally, only incremental direct leasing costs may be capitalized under this new guidance, which is consistent with the Company’s existing policies. ASU 2016-02 originally required a modified retrospective method of adoption, however, the 2018 Exposure Draft indicates that companies may be permitted to recognize a cumulative-effect adjustment to the opening balance of retained earnings in the period of adoption. The pronouncement allows some optional practical expedients. The Company expects to adopt this new guidance on January 1, 2019 and will continue to evaluate the impact of this guidance until it becomes effective. ASU No. 2016-13 (ASU 2016-13), Measurement of Credit Losses on Financial Instruments (Subtopic 326) In June 2016, the FASB issued guidance which requires a financial asset measured at amortized cost basis to be presented at the net amount expected to be collected. The amendments affect entities holding financial assets and net investment in leases that are not accounted for at fair value through net income. The amendments affect loans, debt securities, trade receivables, net investments in leases, off-balance-sheet credit exposures, reinsurance receivables, and any other financial assets not excluded from the scope that have the contractual right to receive cash. The guidance is effective for annual periods beginning after December 15, 2019. Early adoption is permitted. We are currently evaluating the full impact of the new standard. ASU No. 2016-18 (ASU 2016-18), Restricted Cash (Subtopic 230) In November 2016, the FASB issued guidance which addresses the diversity in the classification and presentation of changes in restricted cash on the statement of cash flows. The amendment requires that a statement of cash flows explain the change during the period in total cash, cash equivalents, and amounts generally described as restricted cash or restricted cash equivalents. The guidance is effective for annual periods beginning after December 15, 2017. Early adoption is permitted. We adopted ASU 2016-18 in the fourth quarter of 2017 with retrospective adoption to all periods presented. Accordingly, restricted cash balances are included along with cash and cash equivalents at the end of the period and beginning of the period in our consolidated statements of cash flows for all periods presented. Line items showing changes in restricted cash balances have been eliminated from our consolidated statements of cash flows. The following table provides a reconciliation of cash, cash equivalents and restricted cash reported within the statement of financial position that sum to the total of the same such amounts shown in our statements of cash flows for the years ended December 31, 2017, 2016, and 2015 (in millions): Year Ended December 31, 2017 2016 2015 Cash and cash equivalents $ 151.9 $ 14.6 $ 14.3 Restricted cash — — 1.5 Total cash, cash equivalents, and restricted cash shown in the statement of cash flows $ 151.9 $ 14.6 $ 15.8 The balance of total cash, cash equivalents and restricted cash as of January 1, 2015, was $36.5 million . ASU No. 2017-01 (ASU 2017-01), Business Combinations (Topic 805) In January 2017, the FASB issued guidance which clarifies the definition of a business with the objective of adding guidance to assist entities with evaluating whether transactions should be accounted for as acquisitions (or disposals) of assets or businesses. The definition of a business affects many areas of accounting including acquisitions, disposals, goodwill and consolidation. Under this new guidance, the Company expects most acquisitions of investment property will meet the definition of an asset and, thus, be accounted for as asset acquisitions. Consistent with existing guidance, transaction costs associated with asset acquisitions are capitalized while transaction costs associated with business combinations are expensed as incurred. The guidance is effective for annual periods beginning after December 15, 2017. Early adoption is permitted. We adopted this standard on January 1, 2017, and applied the new guidance for the acquisition of the Sentinel Properties. ASU No. 2017-04 (ASU 2017-04), Goodwill and Other (Topic 350) In January 2017, the FASB issued ASU 2017-04 in order to simplify the test for goodwill impairment by eliminating Step 2, which measures a goodwill impairment loss by comparing the implied fair value of a reporting unit's goodwill with the carrying amount of that goodwill. Under the amendments in this Update, an entity should perform its annual goodwill impairment test by comparing the fair value of a reporting unit with its carrying amount and should recognize an impairment charge for the amount by which the carrying amount exceeds the reporting unit's fair value. However, the loss recognized should not exceed the total amount of goodwill allocated to that reporting unit. The guidance is effective for CyrusOne beginning on January 1, 2020 and early adoption is permitted for interim or annual goodwill impairment tests performed on testing dates after January 1, 2017. We adopted this standard on January 1, 2017. The adoption of this standard did not have any impact on our consolidated financial statements. ASU No. 2017-05 (ASU 2017-05), Other Income—Gains and Losses from the Derecognition of Nonfinancial Assets (Subtopic 610-20)—Clarifying the Scope of Asset Derecognition Guidance and Accounting for Partial Sales of Nonfinancial Assets In February 2017, the FASB issued ASU 2017-05, Other Income – Gains and Losses from the Derecognition of Nonfinancial Assets (Topic 610-20), which requires that all entities account for the derecognition of a business in accordance with ASC 810, Consolidations, including instances in which the business is considered in substance real estate. The ASU is effective for annual periods, and interim periods therein, beginning after December 15, 2017. Early application is permitted. We are currently evaluating the full impact of the new standard.

Recently Issued Accounting St34

Recently Issued Accounting Standards (Tables)	12 Months Ended
	Dec. 31, 2017
Accounting Changes and Error Corrections [Abstract]
Reconciliation of Cash, Cash Equivalents and Restricted Cash	The following table provides a reconciliation of cash, cash equivalents and restricted cash reported within the statement of financial position that sum to the total of the same such amounts shown in our statements of cash flows for the years ended December 31, 2017, 2016, and 2015 (in millions): Year Ended December 31, 2017 2016 2015 Cash and cash equivalents $ 151.9 $ 14.6 $ 14.3 Restricted cash — — 1.5 Total cash, cash equivalents, and restricted cash shown in the statement of cash flows $ 151.9 $ 14.6 $ 15.8

Acquisitions and Purchase of 35

Acquisitions and Purchase of Fixed Assets (Tables)	12 Months Ended
	Dec. 31, 2017
Business Combinations [Abstract]
Schedule of Assets Acquired and Liabilities Assumed	The following table summarizes the estimated fair values of all assets acquired at the date of acquisition: IN MILLIONS Net investment in real estate $ 420.3 Cash and cash equivalents 3.2 Intangible assets: Above/Below market leases 2.3 In-place leases 75.8 Other assets 2.4 Payables (5.4 ) Deferred revenue (0.9 ) Capital lease obligation (2.2 ) Net assets acquired attributable to CyrusOne Inc. 495.5 Cash acquired (3.2 ) Net cash paid at acquisition $ 492.3 The following table summarizes the estimated fair values of all assets acquired and liabilities assumed at the date of acquisition: Cash $ 1.1 Rent and other receivables 10.5 Restricted cash 8.8 Net investment in real estate 197.8 Goodwill 178.9 Customer relationships 117.4 Trade name 2.3 Other long-term assets 5.6 Total assets acquired 522.4 Current liabilities 18.3 Capital lease obligations 1.7 Long-term debt 1.5 Lease financing arrangements 101.4 Total liabilities 122.9 Net assets acquired attributable to CyrusOne Inc. 399.5 Cash acquired (1.1 ) Net cash paid at acquisition $ 398.4
Pro Forma	The unaudited pro forma combined historical results of CyrusOne, as if Cervalis had been acquired and the financing transactions had been consummated as of January 1, 2015 are: IN MILLIONS For the year ended December 31, 2015 Revenue $ 438.6 Net loss (10.9 ) Loss per share - basic and diluted $ (0.16 )

Investment in Real Estate (Tabl

Investment in Real Estate (Tables)	12 Months Ended
	Dec. 31, 2017
Real Estate [Abstract]
Schedule of Gross Investment in Real Estate	A schedule of our gross investment in real estate follows: IN MILLIONS As of December 31, 2017 2016 Land Building and Equipment Land Building and Equipment Dallas - Carrollton $ 16.1 $ 61.8 $ 210.7 $ 16.1 $ 57.6 $ 154.0 Houston - Houston West I 1.4 85.2 49.8 1.4 85.0 48.4 Cincinnati - 7th Street 0.9 110.6 33.1 0.9 110.6 21.0 Dallas - Lewisville — 76.7 37.4 — 76.7 33.7 Northern Virginia - Sterling II — 28.8 112.3 — 28.7 111.8 Somerset I 12.1 124.8 83.7 — — — Chicago - Aurora I 2.4 32.4 125.0 2.4 28.5 99.9 Totowa - Madison — 28.5 55.1 — 28.3 50.8 Cincinnati - North Cincinnati 4.0 77.4 9.9 4.0 77.3 9.0 San Antonio III — 40.3 96.8 — — — Houston - Houston West II 2.8 22.8 50.1 2.8 23.1 49.0 Wappingers Falls I — 11.3 18.0 — 11.3 17.1 San Antonio I 4.6 31.7 34.8 4.6 32.1 33.6 Phoenix - Chandler II — 16.2 38.9 — 16.1 38.8 Northern Virginia - Sterling I 7.0 20.0 59.4 7.0 19.7 47.2 Raleigh-Durham I 2.1 78.0 76.0 — — — Houston - Galleria — 68.6 17.6 — 68.6 16.6 Phoenix - Chandler I 14.8 58.2 65.9 14.8 56.8 56.5 Phoenix - Chandler III — 11.4 50.0 — 9.9 44.5 Northern Virginia - Sterling III — 22.2 61.3 — — — Austin II 2.0 23.4 7.0 2.0 23.4 6.6 San Antonio II 7.0 29.0 60.4 7.0 29.0 59.4 Florence 2.2 42.0 5.3 2.2 41.9 4.9 Phoenix - Chandler IV — 18.3 40.9 — — — Cincinnati - Hamilton — 50.2 6.0 — 50.2 5.0 London - Great Bridgewater — 28.4 1.1 — 25.9 0.9 Northern Virginia - Sterling IV 4.6 20.0 73.7 4.6 11.0 33.4 Cincinnati - Mason — 20.3 1.6 — 20.2 1.4 Dallas - Midway — 2.0 0.4 — 2.0 0.4 Phoenix - Chandler VI 10.5 15.7 49.2 10.5 — — Stamford - Riverbend — 2.9 6.9 — 4.3 14.5 Norwalk I — 13.5 9.4 — 19.0 26.6 Dallas - Marsh — 0.1 0.6 — 0.1 0.6 Chicago - Lombard 0.7 4.7 7.7 0.7 4.7 7.9 Stamford - Omega — 2.6 0.7 — 3.2 1.5 Totowa - Commerce — 4.1 1.6 — 4.1 1.4 Cincinnati - Blue Ash — 0.7 0.2 — 0.6 0.1 South Bend - Crescent — 1.7 0.1 — 1.7 0.2 Houston - Houston West III 18.4 17.9 30.7 18.4 9.4 13.5 Singapore - Inter Business Park — — — — 8.2 0.1 South Bend - Monroe — 2.5 0.3 — 2.5 0.3 Cincinnati - Goldcoast 0.2 4.0 0.1 0.2 4.0 0.1 Austin III 3.3 10.6 33.9 3.3 9.7 31.8 Northern Virginia - Sterling V 24.1 35.7 108.8 24.1 — — IN MILLIONS As of December 31, 2017 2016 Land Building and Equipment Land Building and Equipment Phoenix - Chandler V — 5.9 20.5 — — — San Antonio IV — — 17.9 — — — Austin I — — — — 3.5 0.2 Austin Land A 8.0 — 0.2 8.0 — 0.2 Chicago - Aurora II 2.6 8.3 42.9 2.6 — — Chicago - Aurora Land B 5.1 — — 5.1 — — Dallas - Allen 12.0 — — — — — Quincy Land A 3.1 — — — — — Atlanta I 5.1 — — — — — Total $ 177.1 $ 1,371.4 $ 1,813.9 $ 142.7 $ 1,008.9 $ 1,042.9

Notes Receivable (Tables)

Notes Receivable (Tables)	12 Months Ended
	Dec. 31, 2017
Receivables [Abstract]
Schedule of notes receivable	The carrying amount of notes receivable was $3.3 million and $6.6 million as of December 31, 2017 and 2016 , respectively, and consisted of the following: IN MILLIONS For the year ended December 31, 2017 2016 Note 1 $ 1.8 $ 2.2 Note 2 0.6 — Note 3 0.5 3.9 Note 4 0.4 0.5 Total $ 3.3 $ 6.6

Goodwill, Intangible and Othe38

Goodwill, Intangible and Other Long-Lived Assets (Tables)	12 Months Ended
	Dec. 31, 2017
Goodwill and Intangible Assets Disclosure [Abstract]
Schedule of Carrying Value of Major Classes of Intangible Assets	Summarized below are the carrying values for the major classes of intangible assets: IN MILLIONS For the year ended December 31, 2017 2016 Weighted- Gross Carrying Amount Accumulated Amortization Total Gross Carrying Amount Accumulated Amortization Total Customer relationships 11 $ 247.1 $ (123.0 ) $ 124.1 $ 247.1 $ (106.3 ) $ 140.8 Trademark/tradename 6 9.7 (5.3 ) 4.4 9.7 (3.9 ) 5.8 Favorable leasehold interest 47 4.1 (0.5 ) 3.6 4.1 (0.5 ) 3.6 In place customer leases 8 75.9 (7.1 ) 68.8 — — — Above and below market leases 8 2.3 (0.2 ) 2.1 — — — Total $ 339.1 $ (136.1 ) $ 203.0 $ 260.9 $ (110.7 ) $ 150.2
Schedule of Estimated Amortization Expense for Finite-Lived Intangible Assets	The following table presents estimated amortization expense for each of the next five years and thereafter, commencing January 1, 2018 : IN MILLIONS 2018 $ 24.7 2019 22.4 2020 21.3 2021 20.3 2022 19.7 Thereafter 94.6 Total $ 203.0

Long-Term Debt, Capital Lease39

Long-Term Debt, Capital Lease Obligations and Lease Financing Arrangements (Tables)	12 Months Ended
	Dec. 31, 2017
Debt Disclosure [Abstract]
Schedule of Long-term debt, Capital lease obligations and Lease financing arrangements	Long-term debt, Capital lease obligations and Lease financing arrangements presented in the accompanying consolidated financial statements consist of the following: IN MILLIONS For the year ended December 31, 2017 2016 Credit facilities: Revolving Credit Facility $ — $ 235.0 2021 Term Loan 250.0 250.0 2022 Term Loan 650.0 300.0 2024 Notes, including bond premium 706.8 — 2027 Notes, including bond premium 510.5 — 2022 Notes, including bond premium — 477.3 Deferred financing costs (27.9 ) (22.2 ) Long-term debt, net 2,089.4 1,240.1 Capital lease obligations 10.1 10.8 Lease financing arrangements 131.9 135.7 Total $ 2,231.4 $ 1,386.6
Annual minimum payments associated with lease financing arrangements	The following table summarizes aggregate maturities of total future value and present value of the minimum payments associated with our Lease financing arrangements for the five years subsequent to December 31, 2017 , and thereafter: IN MILLIONS Future Value of Payments Interest Present Value of Payments 2018 $ 14.9 $ 7.9 $ 7.0 2019 15.1 7.4 7.7 2020 27.8 6.8 21.0 2021 11.5 5.8 5.7 2022 11.8 5.5 6.3 Thereafter 100.6 16.4 84.2 Total lease financing arrangements $ 181.7 $ 49.8 $ 131.9
Schedule of annual principal maturities of revolving credit facility, 6.375% Senior notes and capital leases	The following table summarizes aggregate maturities of the Revolving Credit Facility and Term Loans, 2024 Notes and 2027 Notes, and capital leases for the five years subsequent to December 31, 2017 , and thereafter: IN MILLIONS Revolving Credit Facility/Term Loans Senior Notes Capital Leases Total 2018 $ — $ — $ 2.0 $ 2.0 2019 — — 1.9 1.9 2020 — — 2.0 2.0 2021 250.0 — 2.0 252.0 2022 650.0 — 0.9 650.9 Thereafter — 1,200.0 1.3 1,201.3 Total debt $ 900.0 $ 1,200.0 $ 10.1 $ 2,110.1

Fair Value Measurements (Tables

Fair Value Measurements (Tables)	12 Months Ended
	Dec. 31, 2017
Fair Value Disclosures [Abstract]
Carrying Value and Fair Value of Other Financial Instruments	The carrying value and fair value of other financial instruments are as follows: IN MILLIONS For the year ended December 31, 2017 2016 Carrying Value Fair Value Carrying Value Fair Value 2024 Notes $ 706.8 $ 728.0 $ — $ — 2027 Notes 510.5 527.5 — — 2022 Notes — — 477.3 502.1 Revolving Credit Facility and Term Loans 900.0 900.0 785.0 785.0 Equity investment 100.0 175.6 — —

Noncontrolling Interest - Ope41

Noncontrolling Interest - Operating Partnership (Tables)	12 Months Ended
	Dec. 31, 2017
Noncontrolling Interest [Abstract]
Schedule of Ownership Interests in Operating Partnership	The following table shows the distributions and net loss attributed to CBI for the year ended December 31, 2015: For the year ended December 31, 2015 (in millions, except unit amount) The Company CBI Operating partnership units 72.6 — Ownership % 100.0 % — % Portion of net loss $ (15.4 ) $ (4.8 ) Distributions $ (74.6 ) $ (16.3 )

Dividends (Tables)

Dividends (Tables)	12 Months Ended
	Dec. 31, 2017
Stockholders' Equity Note [Abstract]
Schedule of declared cash dividends on common shares and distributions on operating partnership units	We have declared cash dividends on common shares and distributions on operating partnership units for the years ended December 31, 2017 and 2016 as presented in the table below: Record date Payment date Cash dividend per share or operating partnership unit March 25, 2016 April 15, 2016 $0.38 June 24, 2016 July 15, 2016 $0.38 September 30, 2016 October 14, 2016 $0.38 December 30, 2016 January 13, 2017 $0.38 March 31, 2017 April 14, 2017 $0.42 June 30, 2017 July 14, 2017 $0.42 September 29, 2017 October 13, 2017 $0.42 December 29, 2017 January 12, 2018 $0.42 In 2017 and 2016 , we paid all our dividends in cash. The following table summarizes the taxability of our common stock dividends per share for the years ended December 31, 2017 and 2016 : For the year ended December 31, 2017 2016 Common Stock dividend per share: Ordinary income $ — $ 0.20 Return of capital 1.64 1.26 Total dividend $ 1.64 $ 1.46

Customer Leases (Tables)

Customer Leases (Tables)	12 Months Ended
	Dec. 31, 2017
Leases [Abstract]
Schedule of Future Minimum Rental Payments for Operating Leases	The future minimum lease payments to be received under non-cancellable operating leases, excluding month-to-month arrangements and submetered power, for the next five years are shown below: IN MILLIONS 2018 $ 530.2 2019 414.1 2020 352.5 2021 289.2 2022 231.1 At December 31, 2017 , future minimum lease payments required under operating leases having initial or remaining non-cancellable lease terms in excess of one year are as follows: IN MILLIONS 2018 $ 4.8 2019 2.3 2020 1.7 2021 0.6 2022 0.5 Thereafter 4.2 Total $ 14.1

(Loss) Income per Share (Tables

(Loss) Income per Share (Tables)	12 Months Ended
	Dec. 31, 2017
Earnings Per Share [Abstract]
Computation of Basic and Diluted Net (Loss) Income Per Share	The following table reflects the computation of basic and diluted net (loss) income per share: IN MILLIONS, except per share amounts Year Ended Year Ended Period Ended For December 31, 2017 2016 2015 Basic Diluted Basic Diluted Basic Diluted Numerator: Net (loss) income $ (83.5 ) $ (83.5 ) $ 19.9 $ 19.9 $ (15.4 ) $ (15.4 ) Less: Restricted stock dividends (0.9 ) (0.9 ) (0.7 ) (0.7 ) (1.0 ) (1.0 ) Net (loss) income available to stockholders $ (84.4 ) $ (84.4 ) $ 19.2 $ 19.2 $ (16.4 ) $ (16.4 ) Denominator: Weighted average common outstanding-basic 88.9 88.9 78.3 78.3 54.3 54.3 Performance-based restricted stock and units (1)(2) — 0.7 — Weighted average shares outstanding-diluted 88.9 79.0 54.3 EPS: Net (loss) income per share-basic $ (0.95 ) $ 0.24 $ (0.30 ) Effect of dilutive shares: Net (loss) income per share-diluted $ (0.95 ) $ 0.24 $ (0.30 ) (1) We have excluded 0.4 million weighted average shares of restricted stock, and 0.1 million of weighted average stock options which are securities convertible into common stock from our diluted earnings per share as of December 31, 2017. These amounts were deemed anti-dilutive. (2) We have excluded 1.9 million weighted average shares of restricted stock, and 13.1 million of weighted average operating partnership units which are securities convertible into common stock from our diluted earnings per share as of December 31, 2015 . These amounts were deemed anti-dilutive.

Stock-Based Compensation Plans

Stock-Based Compensation Plans (Tables)	12 Months Ended
	Dec. 31, 2017
Disclosure of Compensation Related Costs, Share-based Payments [Abstract]
Schedule of Compensation Expense	Stock-based compensation expense was as follows: For the periods ended December 31, 2017 2016 2015 Founders $ — $ 0.3 $ 5.2 2013 Grants — 0.1 1.2 2014 Grants 0.1 1.2 3.0 2015 Grants 1.8 3.5 5.0 2016 Grants 6.6 7.2 — 2017 Grants 6.2 — — Total $ 14.7 $ 12.3 $ 14.4
Schedule of Restricted Stock Awards Activity	The following table summarizes the unvested restricted stock/unit activity and the weighted average fair value of these shares at the date of grant for the year ended December 31, 2017 : For the year ended December 31, 2017 Shares Weighted Average Grant Date Fair Value Non-vested at January 1 1,274,713 $ 28.95 Granted 287,395 55.46 Vested (446,623 ) 26.83 Forfeited (135,385 ) 21.92 Non-vested at December 31 980,100 $ 38.66
Schedule of Unvested Stock Options	The following table summarizes the stock option activity for the year ended December 31, 2017 : For the year ended December 31, 2017 Options Weighted Average Exercise Price Outstanding at January 1 434,268 $ 31.89 Granted — — Exercised (18,809 ) 36.79 Forfeited or expired — — Outstanding at December 31 415,459 31.67 Exercisable at December 31 235,395 29.45 Vested and expected to vest 415,459 $ 31.67
Schedule of Option Valuation Assumptions	The following table summarizes the stock option assumptions for the years ended December 31, 2017 , 2016 and 2015 : Options Outstanding Options Exercisable Assumption Range Exercise Prices Number of Shares Weighted Average Remaining Contractual Terms (Years) Number of Shares Weighted Average Remaining Contractual Terms (Years) Risk-Free Interest Rate Expected Annual Dividend Yield Expected Terms in Years Expected Volatility 2015 $23.58 142,556 7.3 43,460 7.3 0.92% 3.4% 6.0 35% $28.42 178,704 9.1 35,346 9.1 1.6% - 1.75% 4.4% 5.5-6.5 32.5% - 37.5% $30.74 12,719 9.6 — 0.0 1.6% - 1.75% 4.4% 5.5-6.5 32.5% - 37.5% 2016 $23.58 67,601 6.3 67,601 6.3 0.92% 3.4% 6.0 35% $28.42 143,358 8.1 47,786 8.1 1.6% - 1.75% 4.4% 5.5-6.5 32.5% - 37.5% $30.74 12,719 8.6 4,240 8.6 1.6% - 1.75% 4.4% 5.5-6.5 32.5% - 37.5% $36.99 210,590 9.1 18,530 9.1 1.47% - 1.64% 4.1% 5.5-6.5 27.5% - 35.0% 2017 $23.58 67,322 5.3 67,322 5.3 0.92% 3.4% 6.0 35% $28.42 143,358 7.1 95,572 7.1 1.6% - 1.75% 4.4% 5.5-6.5 32.5% - 37.5% $30.74 12,719 7.6 8,479 7.6 1.6% - 1.75% 4.4% 5.5-6.5 32.5% - 37.5% $36.99 192,060 8.1 64,022 8.1 1.47% - 1.64% 4.1% 5.5-6.5 27.5% - 35.0%

Related Party Transactions (Tab

Related Party Transactions (Tables)	12 Months Ended
	Dec. 31, 2017
Related Party Transactions [Abstract]
Schedule of Related Party Transactions	The following related party transactions are based on agreements and arrangements that were in place during 2015. Revenues and expenses for the period presented were as follows: IN MILLIONS December 31, 2015 Revenue: Data center colocation agreement provided to CBT and CBTS $ 7.8 229 West 7th Street lease provided to CBT 1.9 Goldcoast Drive/Parkway (Mason) lease 0.3 Transition services provided to CBTS (network interfaces) 0.3 Data center leases provided to CBTS 12.0 Total revenue $ 22.3 Operating costs and expenses: Transition services agreement by CBTS $ 0.7 Charges for services provided by CBT (connectivity) 1.0 209 West 7th Street rent provided by CBT 0.2 Total operating costs and expenses $ 1.9

Income Taxes (Tables)

Income Taxes (Tables)	12 Months Ended
	Dec. 31, 2017
Income Tax Disclosure [Abstract]
Schedule of taxability of common stock dividends per share	We have declared cash dividends on common shares and distributions on operating partnership units for the years ended December 31, 2017 and 2016 as presented in the table below: Record date Payment date Cash dividend per share or operating partnership unit March 25, 2016 April 15, 2016 $0.38 June 24, 2016 July 15, 2016 $0.38 September 30, 2016 October 14, 2016 $0.38 December 30, 2016 January 13, 2017 $0.38 March 31, 2017 April 14, 2017 $0.42 June 30, 2017 July 14, 2017 $0.42 September 29, 2017 October 13, 2017 $0.42 December 29, 2017 January 12, 2018 $0.42 In 2017 and 2016 , we paid all our dividends in cash. The following table summarizes the taxability of our common stock dividends per share for the years ended December 31, 2017 and 2016 : For the year ended December 31, 2017 2016 Common Stock dividend per share: Ordinary income $ — $ 0.20 Return of capital 1.64 1.26 Total dividend $ 1.64 $ 1.46

Commitments and Contingencies (

Commitments and Contingencies (Tables)	12 Months Ended
	Dec. 31, 2017
Commitments and Contingencies Disclosure [Abstract]
Schedule of Future Minimum Rental Payments for Operating Leases	The future minimum lease payments to be received under non-cancellable operating leases, excluding month-to-month arrangements and submetered power, for the next five years are shown below: IN MILLIONS 2018 $ 530.2 2019 414.1 2020 352.5 2021 289.2 2022 231.1 At December 31, 2017 , future minimum lease payments required under operating leases having initial or remaining non-cancellable lease terms in excess of one year are as follows: IN MILLIONS 2018 $ 4.8 2019 2.3 2020 1.7 2021 0.6 2022 0.5 Thereafter 4.2 Total $ 14.1

Guarantors (Tables)

Guarantors (Tables)	12 Months Ended
	Dec. 31, 2017
Condensed Financial Information of Parent Company Only Disclosure [Abstract]
Consolidating Balance Sheet	Consolidating Balance Sheets IN MILLIONS As of December 31, 2017 Parent General LP Finance Guarantor Subsidiaries Non- Eliminations/Consolidations Total Land $ — $ — $ — $ — $ 177.1 $ — $ — $ 177.1 Buildings and improvements — — — — 1,340.8 28.4 2.2 1,371.4 Equipment — — — — 1,803.9 1.1 8.9 1,813.9 Construction in progress — — — — 471.7 0.1 6.6 478.4 Subtotal — — — — 3,793.5 29.6 17.7 3,840.8 Accumulated depreciation — — — — (778.6 ) (3.8 ) — (782.4 ) Net investment in real estate — — — — 3,014.9 25.8 17.7 3,058.4 Cash and cash equivalents — — — — 151.2 0.7 — 151.9 Investment in subsidiaries 1,718.0 17.2 2,190.2 — — — (3,925.4 ) — Rent and other receivables, net — — — — 87.9 2.6 — 90.5 Intercompany receivable 20.0 — 1,656.4 — — — (1,676.4 ) — Goodwill — — — — 455.1 — — 455.1 Intangible assets, net — — — — 203.0 — — 203.0 Other assets — — 0.5 — 174.4 178.3 — 353.2 Total assets $ 1,738.0 $ 17.2 $ 3,847.1 $ — $ 4,086.5 $ 207.4 $ (5,584.1 ) $ 4,312.1 Accounts payable and accrued expenses $ 41.8 $ — $ 19.7 — $ 192.8 $ 0.9 $ — $ 255.2 Deferred revenue — — — — 110.8 0.8 — 111.6 Intercompany payable — — 20.0 — 1,656.4 — (1,676.4 ) — Capital lease obligations — — — — 5.4 4.7 — 10.1 Long-term debt, net — — 2,089.4 — — — — 2,089.4 Lease financing arrangements — — — — 104.6 27.3 — 131.9 Total liabilities 41.8 — 2,129.1 — 2,070.0 33.7 (1,676.4 ) 2,598.2 Total stockholders' equity 1,696.2 17.2 1,718.0 — 2,016.5 173.7 (3,907.7 ) 1,713.9 Total liabilities and equity $ 1,738.0 $ 17.2 $ 3,847.1 $ — $ 4,086.5 $ 207.4 $ (5,584.1 ) $ 4,312.1 IN MILLIONS As of December 31, 2016 Parent General LP Finance Guarantor Subsidiaries Non- Eliminations/Consolidations Total Land $ — $ — $ — $ — $ 142.7 $ — $ — $ 142.7 Buildings and improvements — — — — 973.6 34.1 1.2 1,008.9 Equipment — — — — 1,036.8 1.0 5.1 1,042.9 Construction in progress — — — — 406.4 — 0.7 407.1 Subtotal — — — — 2,559.5 35.1 7.0 2,601.6 Accumulated depreciation — — — — (571.3 ) (7.2 ) — (578.5 ) Net investment in real estate — — — — 1,988.2 27.9 7.0 2,023.1 Cash and cash equivalents — — — — 13.4 1.2 — 14.6 Investment in subsidiaries 1,170.3 11.7 1,376.1 — 2.0 — (2,560.1 ) — Rent and other receivables, net — — — — 81.8 1.5 — 83.3 Intercompany receivable 18.6 — 1,057.7 — — 0.5 (1,076.8 ) — Goodwill — — — — 455.1 — — 455.1 Intangible assets, net — — — — 150.2 — — 150.2 Other assets — — — — 123.4 2.7 — 126.1 Total assets $ 1,188.9 $ 11.7 $ 2,433.8 $ — $ 2,814.1 $ 33.8 $ (3,629.9 ) $ 2,852.4 Accounts payable and accrued expenses $ 33.9 $ — $ 4.8 — $ 187.7 $ 0.7 $ — $ 227.1 Deferred revenue — — — — 76.0 0.7 — 76.7 Intercompany payable — — 18.6 — 1,058.2 — (1,076.8 ) — Capital lease obligations — — — — 5.6 5.2 — 10.8 Long-term debt, net — — 1,240.1 — — — — 1,240.1 Lease financing arrangements — — — — 110.5 25.2 — 135.7 Total liabilities 33.9 — 1,263.5 — 1,438.0 31.8 (1,076.8 ) 1,690.4 Total stockholders' equity 1,155.0 11.7 1,170.3 — 1,376.1 2.0 (2,553.1 ) 1,162.0 Total liabilities and equity $ 1,188.9 $ 11.7 $ 2,433.8 $ — $ 2,814.1 $ 33.8 $ (3,629.9 ) $ 2,852.4
Consolidating Statements of Operations and Comprehensive Income (Loss)	Consolidating Statements of Operations and Comprehensive Income (Loss) IN MILLIONS Year Ended December 31, 2017 Parent Guarantor General Partner LP Co-issuer Finance Co-issuer Guarantor Subsidiaries Non- Guarantors Eliminations/Consolidations Total Revenue: Base revenue and other $ — $ — $ — $ — $ 598.2 $ 4.2 $ — $ 602.4 Metered power reimbursements — — — — 68.2 1.4 — 69.6 Revenue — — — — 666.4 5.6 — 672.0 Costs and expenses: Property operating expenses — — — — 232.5 2.6 — 235.1 Sales and marketing — — — — 17.0 — — 17.0 General and administrative — — — — 66.8 0.2 — 67.0 Depreciation and amortization — — — — 257.8 1.1 — 258.9 Transaction and acquisition integration costs — — — — 10.4 — — 10.4 Asset impairments and loss on disposal — — — — 55.9 3.6 — 59.5 Total costs and expenses — — — — 640.4 7.5 — 647.9 Operating income — — — — 26.0 (1.9 ) — 24.1 Interest expense — — 76.2 — — 2.6 (10.7 ) 68.1 Loss on extinguishment of debt — — 36.5 — — — — 36.5 (Loss) income before income taxes — — (112.7 ) — 26.0 (4.5 ) 10.7 (80.5 ) Income tax expense — — — — (3.0 ) — — (3.0 ) Equity (loss) earnings related to investment in subsidiaries (18.7 ) (0.2 ) 94.0 — (4.6 ) — (70.5 ) — Net (loss) income (18.7 ) (0.2 ) (18.7 ) — 18.4 (4.5 ) (59.8 ) (83.5 ) Other comprehensive income — — — — — 75.5 — 75.5 Comprehensive (loss) income $ (18.7 ) $ (0.2 ) $ (18.7 ) $ — $ 18.4 $ 71.0 $ (59.8 ) $ (8.0 ) IN MILLIONS Year Ended December 31, 2016 Parent Guarantor General Partner LP Co-issuer Finance Co-issuer Guarantor Subsidiaries Non- Guarantors Eliminations/Consolidations Total Revenue: Base revenue and other $ — $ — $ — $ — $ 472.6 $ 4.1 $ — $ 476.7 Metered power reimbursements — — — — 51.1 1.3 — 52.4 Revenue — — — — 523.7 5.4 — 529.1 Costs and expenses: Property operating expenses — — — — 185.2 2.3 — 187.5 Sales and marketing — — — — 16.9 — — 16.9 General and administrative — — — — 60.5 0.2 — 60.7 Depreciation and amortization — — — — 185.3 (1.4 ) — 183.9 Transaction and acquisition integration costs — — — — 4.3 — — 4.3 Asset impairments and loss on disposal — — — — 5.3 — — 5.3 Total costs and expenses — — — — 457.5 1.1 — 458.6 Operating income — — — — 66.2 4.3 — 70.5 Interest expense — — 49.1 — — 2.8 (3.1 ) 48.8 Income (loss) before income taxes — — (49.1 ) — 66.2 1.5 3.1 21.7 Income tax expense — — — — (1.8 ) — — (1.8 ) Equity (loss) earnings related to investment in subsidiaries 15.9 0.2 65.0 — 0.6 — (81.7 ) — Net income (loss) 15.9 0.2 15.9 — 65.0 1.5 (78.6 ) 19.9 Other comprehensive loss — — — — — (0.9 ) — (0.9 ) Comprehensive income (loss) attributable to common stockholders $ 15.9 $ 0.2 $ 15.9 $ — $ 65.0 $ 0.6 $ (78.6 ) $ 19.0 IN MILLIONS Year Ended December 31, 2015 Parent (1) General LP Finance Guarantor Subsidiaries Non- Eliminations/Consolidations Total Revenue: Base revenue and other $ — $ — $ — $ — $ 350.3 $ 4.3 $ — $ 354.6 Metered power reimbursements — — — — 43.5 1.2 — 44.7 Revenue — — — — 393.8 5.5 — 399.3 Costs and expenses: Property operating expenses — — — — 146.0 2.7 — 148.7 Sales and marketing — — — — 12.0 0.1 — 12.1 General and administrative — — — — 46.6 — — 46.6 Depreciation and amortization — — — — 138.7 2.8 — 141.5 Transaction and acquisition integration costs — — — — 14.1 — — 14.1 Asset impairments and loss on disposal — — — — 13.5 — — 13.5 Total costs and expenses — — — — 370.9 5.6 — 376.5 Operating income (loss) — — — — 22.9 (0.1 ) — 22.8 Interest expense — — 39.7 — — 3.2 (1.7 ) 41.2 (Loss) income before income taxes — — (39.7 ) — 22.9 (3.3 ) 1.7 (18.4 ) Income tax expense — — — — (1.8 ) — — (1.8 ) Equity (loss) earnings related to investment in subsidiaries (17.1 ) (0.2 ) 17.8 — (3.3 ) — 2.8 — Net (loss) income (17.1 ) (0.2 ) (21.9 ) — 17.8 (3.3 ) 4.5 (20.2 ) Noncontrolling interest in net loss — — — — — — 4.8 4.8 Net (loss) income attributed to common stockholders (17.1 ) (0.2 ) (21.9 ) — 17.8 (3.3 ) 9.3 (15.4 ) Other comprehensive loss — — — — — (0.2 ) — (0.2 ) Comprehensive (loss) income attributable to common stockholders $ (17.1 ) $ (0.2 ) $ (21.9 ) $ — $ 17.8 $ (3.5 ) $ 9.3 $ (15.6 )
Consolidating Statements of Cash Flows	Consolidating Statements of Cash Flows IN MILLIONS Year Ended December 31, 2017 Parent General LP Finance Guarantor Subsidiaries Non- Eliminations/Consolidations Total Net cash (used in) provided by operating activities $ — $ — $ (60.3 ) $ — $ 339.7 $ (0.6 ) $ 10.7 $ 289.5 Cash flows from investing activities: Capital expenditures - asset acquisitions, net of cash acquired — — — — (492.3 ) — — (492.3 ) Capital expenditures - other development — — — — (903.8 ) — (10.7 ) (914.5 ) Equity investment — — — — — (100.0 ) — (100.0 ) Investment in subsidiaries (705.3 ) (7.1 ) (705.3 ) — (0.7 ) — 1,418.4 — Return of investment 145.7 — — — — — (145.7 ) — Intercompany borrowings 6.5 — (598.8 ) — — 0.5 591.8 — Net cash provided by (used in) investing activities (553.1 ) (7.1 ) (1,304.1 ) — (1,396.8 ) (99.5 ) 1,853.8 (1,506.8 ) Cash flows from financing activities: Issuance of common stock 706.0 — — — — — — 706.0 Stock issuance costs (0.3 ) — — — — — — (0.3 ) Dividends paid (145.7 ) — (145.7 ) — — — 145.7 (145.7 ) Intercompany borrowings — — (6.5 ) — 598.2 — (591.7 ) — Borrowings from credit facility — — 1,390.0 — — — — 1,390.0 Payments on credit facility — — (1,275.0 ) — — — — (1,275.0 ) Payments on senior notes — — (474.8 ) — — — — (474.8 ) Proceeds from issuance of debt — — 1,217.8 — — — — 1,217.8 Debt issuance costs — — (19.0 ) — — — — (19.0 ) Payments on capital leases and lease financing arrangements — — — — (8.6 ) (1.2 ) — (9.8 ) Interest paid by lenders on issuance of the senior notes — — 2.7 — — — — 2.7 Payment of debt extinguishment costs — — (30.4 ) — — — — (30.4 ) Tax payment upon exercise of equity awards (6.9 ) — — — — — — (6.9 ) Contributions/distributions from parent — 7.1 705.3 — 605.3 100.8 (1,418.5 ) — Net cash provided by (used in) financing activities 553.1 7.1 1,364.4 — 1,194.9 99.6 (1,864.5 ) 1,354.6 Net increase (decrease) in cash, cash equivalents and restricted cash — — — — 137.8 (0.5 ) — 137.3 Cash, cash equivalents and restricted cash at beginning of period — — — — 13.4 1.2 — 14.6 Cash, cash equivalents and restricted cash at end of period $ — $ — $ — $ — $ 151.2 $ 0.7 $ — $ 151.9 IN MILLIONS Year Ended December 31, 2016 Parent General LP Finance Guarantor Subsidiaries Non- Eliminations/Consolidations Total Net cash (used in) provided by operating activities $ — $ — $ (45.4 ) $ — $ 221.8 $ — $ 4.2 $ 180.6 Cash flows from investing activities: Capital expenditures - asset acquisitions, net of cash acquired — — — — (131.1 ) — — (131.1 ) Capital expenditures - other development — — — — (598.9 ) (1.1 ) — (600.0 ) Investment in subsidiaries (448.2 ) (4.5 ) (448.2 ) — — — 900.9 — Return of investment 112.3 — — — — — (112.3 ) — Intercompany borrowings 15.3 — (66.3 ) — — (0.5 ) 51.5 — Net cash provided by (used in) investing activities (320.6 ) (4.5 ) (514.5 ) — (730.0 ) (1.6 ) 840.1 (731.1 ) Cash flows from financing activities: Issuance of common stock 448.7 — — — — — — 448.7 Stock issuance costs (1.6 ) — — — — — — (1.6 ) Dividends paid (112.3 ) — (114.3 ) — — — 112.3 (114.3 ) Intercompany borrowings — — (15.3 ) — 71.0 — (55.7 ) — Borrowings from credit facility — — 710.0 — — — — 710.0 Payments on credit facility — — (460.0 ) — — — — (460.0 ) Payments on capital leases and lease financing arrangements — — — — (8.0 ) (1.1 ) — (9.1 ) Tax payment upon exercise of equity awards (14.2 ) — — — — — — (14.2 ) Contributions/distributions from parent — 4.5 448.2 — 448.2 — (900.9 ) — Payment of note payable — — — — (1.5 ) — — (1.5 ) Debt issuance costs — — (8.7 ) — — — — (8.7 ) Net cash provided by (used in) financing activities 320.6 4.5 559.9 — 509.7 (1.1 ) (844.3 ) 549.3 Net increase (decrease) in cash, cash equivalents and restricted cash — — — — 1.5 (2.7 ) — (1.2 ) Cash, cash equivalents and restricted cash at beginning of period — — — — 11.9 3.9 — 15.8 Cash, cash equivalents and restricted cash at end of period $ — $ — $ — $ — $ 13.4 $ 1.2 $ — $ 14.6 IN MILLIONS Year Ended December 31, 2015 Parent Guarantor General Partner LP Co-issuer Finance Co-issuer Guarantor Subsidiaries Non- Guarantors Eliminations/Consolidations Total Net cash (used in) provided by operating activities $ — $ — $ (19.6 ) $ — $ 156.2 $ 1.9 $ 1.7 $ 140.2 Cash flows from investing activities: Capital expenditures - purchase of fixed assets — — — — (17.3 ) — — (17.3 ) Capital expenditures - other development — — — — (216.7 ) (0.5 ) — (217.2 ) Business acquisition, net of cash acquired — — — — (389.6 ) — — (389.6 ) Investment in subsidiaries (203.1 ) (2.0 ) (203.1 ) — (0.4 ) — 408.6 — Return of investment 62.6 — 102.0 — (17.9 ) — (146.7 ) — Intercompany borrowings — — (348.4 ) — — — 348.4 — Net cash (used in) provided by investing activities (140.5 ) (2.0 ) (449.5 ) — (641.9 ) (0.5 ) 610.3 (624.1 ) Cash flows from financing activities: Issuance of common stock 799.5 — — — — — — 799.5 Stock issuance costs (0.8 ) — — — — — — (0.8 ) Acquisition of operating partnership units (596.4 ) — — — — — — (596.4 ) Dividends paid (61.0 ) — (80.8 ) — (80.8 ) — 141.8 (80.8 ) Intercompany borrowings — — — — 348.4 — (348.4 ) — Borrowings from credit facility — — 260.0 — — — — 260.0 Proceeds from issuance of debt — — 103.8 — — — — 103.8 Payments on credit facility — — (10.0 ) — — — — (10.0 ) Payments on capital leases and lease financing arrangements — — — — (5.0 ) (0.9 ) — (5.9 ) Tax payment upon exercise of equity awards (0.8 ) — — — — — — (0.8 ) Contributions/distributions from parent — 2.0 201.5 — 201.5 0.4 (405.4 ) — Debt issuance costs — — (5.4 ) — — — — (5.4 ) Net cash provided by (used in) financing activities 140.5 2.0 469.1 — 464.1 (0.5 ) (612.0 ) 463.2 Net (decrease) increase in cash, cash equivalents and restricted cash — — — — (21.6 ) 0.9 — (20.7 ) Cash, cash equivalents and restricted cash at beginning of period — — — — 33.5 3.0 — 36.5 Cash, cash equivalents and restricted cash at end of period $ — $ — $ — $ — $ 11.9 $ 3.9 $ — $ 15.8

Quarterly Financial Informati50

Quarterly Financial Information (Unaudited) (Tables)	12 Months Ended
	Dec. 31, 2017
Quarterly Financial Information Disclosure [Abstract]
Schedule of Unaudited Selected Quarterly Financial Information	The table below reflects the unaudited selected quarterly information for the years ended December 31, 2017 and 2016 : IN MILLIONS, except per share amounts 2017 First Quarter Second Quarter Third Quarter Fourth Total Revenue $ 149.3 $ 166.9 $ 175.3 $ 180.5 $ 672.0 Operating income (loss) 19.8 16.7 (36.3 ) 23.9 24.1 Net (loss) income (30.4 ) (0.8 ) (55.1 ) 2.8 (83.5 ) Net (loss) income attributed to common shareholders (30.4 ) (0.8 ) (55.1 ) 2.8 (83.5 ) Basic and diluted (loss) income per share $ (0.36 ) $ (0.01 ) $ (0.61 ) $ 0.03 $ (0.95 ) IN MILLIONS, except per share amounts 2016 First Second Quarter Third Quarter Fourth Quarter Total Revenue $ 117.8 $ 130.1 $ 143.8 $ 137.4 $ 529.1 Operating income 17.9 21.1 18.8 12.7 70.5 Net income 5.6 9.1 4.4 0.8 19.9 Net income attributed to common stockholders 5.6 9.1 4.4 0.8 19.9 Basic and diluted income per share $ 0.07 $ 0.11 $ 0.05 $ 0.01 $ 0.24

Description of Business - Narra

Description of Business - Narrative (Details)	12 Months Ended
	Dec. 31, 2017recovery_centerdata_center
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Number of data operating centers | data_center	45
Number of recovery centers | recovery_center	2

Formation and Recent Developm52

Formation and Recent Developments - Narrative (Details)	Nov. 03, 2017USD ($)	Oct. 18, 2017USD ($)$ / sharesshares	Mar. 17, 2017USD ($)	Feb. 28, 2017USD ($)data_center	Feb. 27, 2017USD ($)shares	Aug. 15, 2016USD ($)shares	Dec. 31, 2015shares	Dec. 14, 2015USD ($)shares	Sep. 30, 2017USD ($)	Jun. 30, 2018USD ($)	Dec. 31, 2017USD ($)shares	Dec. 31, 2016USD ($)shares	Dec. 31, 2015USD ($)shares	Dec. 31, 2014USD ($)shares	Mar. 31, 2018data_center	Jun. 16, 2017USD ($)	Nov. 21, 2016USD ($)	Mar. 17, 2016USD ($)	Jul. 01, 2015	Jun. 22, 2015USD ($)	Oct. 09, 2014USD ($)	Nov. 20, 2012
Business Formation [Line Items]
Proceeds from public stock offerings											$ 706,000,000	$ 448,700,000	$ 799,500,000
Discount rate		4.00%
American depository shares equivalent (in shares) | shares		8
Stock issuance costs											300,000	$ 1,600,000	$ 800,000
Revolving Credit Facility
Business Formation [Line Items]
Optional additional borrowing capacity																$ 100,000,000
Credit agreement amount											1,100,000,000					1,100,000,000	$ 1,000,000,000	$ 650,000,000		$ 650,000,000	$ 450,000,000
Second Amended and Restated Credit Agreement
Business Formation [Line Items]
Optional additional borrowing capacity																450,000,000
Credit agreement amount																2,000,000,000
Credit facility, available capacity under accordion feature											300,000,000					2,300,000,000
Senior Notes | 5.000% Senior Notes Due 2024 and 5.375% Senior Notes Due 2027 [Member]
Business Formation [Line Items]
Debt proceeds, net of underwriting costs	$ 416,100,000		$ 791,200,000
Debt underwriting costs	4,400,000		8,800,000
Senior Notes | 6.375% senior notes due 2022
Business Formation [Line Items]
Repurchased face amount											$ 474,800,000
Term Loan
Business Formation [Line Items]
Debt principal amount																					$ 150,000,000
Credit agreement amount																				$ 300,000,000
Term Loan | 2022 Term Loan
Business Formation [Line Items]
Optional additional borrowing capacity																350,000,000
Credit agreement amount																$ 650,000,000		300,000,000
Term Loan | 2021 Term Loan
Business Formation [Line Items]
Optional additional borrowing capacity																		$ 250,000,000
Sentinel Properties
Business Formation [Line Items]
Number of data center facilities acquired | data_center				2
Consideration for acquisition				$ 492,300,000
Transaction related costs				$ 1,500,000
The Company
Business Formation [Line Items]
Operating partnership units (in shares) | shares							72,600,000				96,100,000		72,600,000
Cincinnati Bell Inc.
Business Formation [Line Items]
Ownership %							9.50%				5.00%	5.00%	9.50%
CyrusOne LP and CyrusOne Finance Corp | Senior Notes | 5.000% Senior Notes Due 2024 and 5.375% Senior Notes Due 2027 [Member]
Business Formation [Line Items]
Debt underwriting costs			10,900,000
CyrusOne LP and CyrusOne Finance Corp | Senior Notes | 2024 Notes, including bond premium
Business Formation [Line Items]
Debt principal amount	$ 200,000,000		$ 500,000,000								$ 706,800,000
Stated interest rate	5.00%		5.00%
CyrusOne LP and CyrusOne Finance Corp | Senior Notes | 2027 Notes, including bond premium
Business Formation [Line Items]
Debt principal amount	$ 200,000,000		$ 300,000,000								$ 510,500,000
Stated interest rate	5.375%		5.375%
CyrusOne LP and CyrusOne Finance Corp | Senior Notes | 6.375% senior notes due 2022
Business Formation [Line Items]
Stated interest rate																			6.375%			6.375%
Public stock offering
Business Formation [Line Items]
Issuance of common stock (in shares) | shares						3,400,000	6,300,000	1,400,000			8,400,000	10,300,000	27,300,000	16,000,000
Proceeds from public stock offerings						$ 164,800,000		$ 0			$ 493,700,000	$ 419,800,000	$ 799,300,000	$ 355,900,000
Stock issuance costs						$ 6,900,000					6,300,000
Public stock offering | Goldman, Sachs & Co.
Business Formation [Line Items]
Issuance of common stock (in shares) | shares					4,400,000
Proceeds from public stock offerings					$ 210,800,000
Public stock offering, new program
Business Formation [Line Items]
Maximum proceeds from issuance of common stock									$ 500,000,000
Employee stock purchase plans
Business Formation [Line Items]
Proceeds from public stock offerings											$ 1,500,000
American depository shares
Business Formation [Line Items]
American depository share (in shares) | shares		8,000,000
Price per ordinary share (in dollars per shares) | $ / shares		$ 12.45
Total investment		$ 100,000,000
Forecast | Subsequent event | Zenium Data Centers
Business Formation [Line Items]
Consideration for acquisition										$ 442,000,000
Forecast | Data centers | Subsequent event | Zenium Data Centers
Business Formation [Line Items]
Number of data center facilities acquired | data_center															4

Significant Accounting Polici53

Significant Accounting Policies - Narrative (Details)	12 Months Ended
	Dec. 31, 2017USD ($)segment	Dec. 31, 2016USD ($)	Dec. 31, 2015USD ($)
Summary Of Significant Accounting Policies [Line Items]
Capitalized interest	$ 17,000,000	$ 10,600,000	$ 6,100,000
Goodwill impairments	0	0	0
Deferred leasing costs	32,600,000	23,300,000
Amortization expense	7,600,000	6,100,000	5,200,000
Straight-line rents receivable	100,000,000	67,600,000
Deferred revenue	111,600,000	76,700,000
Advertising expense	2,400,000	4,100,000	2,200,000
Depreciation expense	226,200,000	157,700,000	$ 117,800,000
Unrecognized tax benefits	$ 0	$ 0
Number of segments | segment	1
Minimum
Summary Of Significant Accounting Policies [Line Items]
Receivables due term	30 days
Maximum
Summary Of Significant Accounting Policies [Line Items]
Receivables due term	120 days
Buildings | Minimum
Summary Of Significant Accounting Policies [Line Items]
Useful life	9 years
Buildings | Maximum
Summary Of Significant Accounting Policies [Line Items]
Useful life	30 years
Building Improvements | Minimum
Summary Of Significant Accounting Policies [Line Items]
Useful life	3 years
Building Improvements | Maximum
Summary Of Significant Accounting Policies [Line Items]
Useful life	30 years
Equipment | Minimum
Summary Of Significant Accounting Policies [Line Items]
Useful life	2 years
Equipment | Maximum
Summary Of Significant Accounting Policies [Line Items]
Useful life	20 years
Microsoft Corporation | Revenue | Customer concentration risk
Summary Of Significant Accounting Policies [Line Items]
Concentration risk percentage	18.00%

Recently Issued Accounting St54

Recently Issued Accounting Standards - Narrative (Details) $ in Millions	12 Months Ended
	Dec. 31, 2017USD ($)
Accounting Changes and Error Corrections [Abstract]
Unrealized gain on equity investment	$ 75.6

Recently Issued Accounting St55

Recently Issued Accounting Standards - Reconciliation of Cash, Cash Equivalents and Restricted Cash (Details) - USD ($) $ in Millions	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Cash and cash equivalents	$ 151.9	$ 14.6
Total cash, cash equivalents, and restricted cash shown in the statement of cash flows	151.9	14.6	$ 15.8	$ 36.5	$ 36.5
ASU 2016-18
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Cash and cash equivalents	151.9	14.6	14.3
Restricted cash	0	0	1.5
Total cash, cash equivalents, and restricted cash shown in the statement of cash flows	$ 151.9	$ 14.6	$ 15.8	$ 36.5

Acquisitions and Purchase of 56

Acquisitions and Purchase of Fixed Assets - Narrative (Details) $ in Millions

Feb. 28, 2017USD ($)ft²data_centerMW

Apr. 01, 2016

Mar. 31, 2016USD ($)ft²

Jul. 01, 2015USD ($)data_centerwork_recovery

Dec. 31, 2015USD ($)

Dec. 31, 2017USD ($)a

Dec. 31, 2016USD ($)property

Dec. 31, 2015USD ($)

Jul. 31, 2017a

Apr. 30, 2017a

Mar. 31, 2016a

Nov. 20, 2012

Business Acquisition [Line Items]

Area of land (in acres) | a

44

66

48

Option to purchase additional land (in acres) | a

24

Transaction and acquisition integration costs

$ 10.4

$ 4.3

$ 14.1

Payment to acquire Chicago-Aurora I data center

$ 20.2

CME Group's data center

Business Acquisition [Line Items]

Area acquired (in sqft or acre)

428,000

15

Payment to acquire Chicago-Aurora I data center

$ 131.1

Lease term

15 years

Properties for development

Business Acquisition [Line Items]

Payment to acquire Chicago-Aurora I data center

$ 54.5

Number of properties purchased | property

4

CyrusOne LP and CyrusOne Finance Corp | 6.375% senior notes due 2022 | Senior Notes

Business Acquisition [Line Items]

Stated interest rate

6.375%

6.375%

Sentinel Properties

Business Acquisition [Line Items]

Number of data center facilities acquired | data_center

2

Consideration for acquisition

$ 492.3

Sentinel Properties | Data centers

Business Acquisition [Line Items]

Area acquired (in sqft or acre) | ft²

160,000

Amount of power capacity acquired | MW

21

Amount of leased power capacity

85.00%

Cervalis

Business Acquisition [Line Items]

Number of data center facilities acquired | data_center

4

Percent of company acquired

100.00%

Consideration for acquisition

$ 398.4

Number of work area recovery facilities acquired | work_recovery

2

Transaction and acquisition integration costs

$ 12.9

Revenue of acquiree since acquisition

$ 37.7

Cervalis | Customer relationships

Business Acquisition [Line Items]

Weighted-average useful life

15 years

Acquisitions and Purchase of 57

Acquisitions and Purchase of Fixed Assets - Schedule of estimated fair values of all assets acquired (Details) - USD ($) $ in Millions	Feb. 28, 2017	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Business Acquisition [Line Items]
Net cash paid at acquisition		$ 0	$ 0	$ 389.6
Sentinel Properties
Business Acquisition [Line Items]
Net investment in real estate	$ 420.3
Cash and cash equivalents	3.2
Other assets	2.4
Payables	(5.4)
Deferred revenue	(0.9)
Capital lease obligation	(2.2)
Net assets acquired attributable to CyrusOne Inc.	495.5
Cash acquired	(3.2)
Net cash paid at acquisition	492.3
Sentinel Properties | Above/Below market leases
Business Acquisition [Line Items]
Intangible assets:	2.3
Sentinel Properties | In-place leases
Business Acquisition [Line Items]
Intangible assets:	$ 75.8

Acquisitions and Purchase of 58

Acquisitions and Purchase of Fixed Assets - Assets Acquired and Liabilities Assumed (Details) - USD ($) $ in Millions	Jul. 01, 2015	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Business Acquisition [Line Items]
Goodwill		$ 455.1	$ 455.1
Net cash paid at acquisition		$ 0	$ 0	$ 389.6
Cervalis
Business Acquisition [Line Items]
Cash	$ 1.1
Rent and other receivables	10.5
Restricted cash	8.8
Net investment in real estate	197.8
Goodwill	178.9
Customer relationships	117.4
Trade name	2.3
Other long-term assets	5.6
Total assets acquired	522.4
Current liabilities	18.3
Capital lease obligations	1.7
Long-term debt	1.5
Lease financing arrangements	101.4
Total liabilities	122.9
Net assets acquired attributable to CyrusOne Inc.	399.5
Cash acquired	(1.1)
Net cash paid at acquisition	$ 398.4

Acquisitions and Purchase of 59

Acquisitions and Purchase of Fixed Assets - Pro Forma (Details) $ / shares in Units, $ in Millions	12 Months Ended
	Dec. 31, 2015USD ($)$ / shares
Business Combinations [Abstract]
Revenue	$ 438.6
Net loss	$ (10.9)
Loss per share - basic and diluted | $ / shares	$ (0.16)

Investment in Real Estate - Sch

Investment in Real Estate - Schedule of Gross Investment in Real Estate (Details) - USD ($) $ in Millions	Dec. 31, 2017	Dec. 31, 2016
Real Estate Properties [Line Items]
Land	$ 177.1	$ 142.7
Building and Improvements	1,371.4	1,008.9
Equipment	1,813.9	1,042.9
Dallas - Carrollton
Real Estate Properties [Line Items]
Land	16.1	16.1
Building and Improvements	61.8	57.6
Equipment	210.7	154
Houston - Houston West I
Real Estate Properties [Line Items]
Land	1.4	1.4
Building and Improvements	85.2	85
Equipment	49.8	48.4
Cincinnati - 7th Street
Real Estate Properties [Line Items]
Land	0.9	0.9
Building and Improvements	110.6	110.6
Equipment	33.1	21
Dallas - Lewisville
Real Estate Properties [Line Items]
Land	0	0
Building and Improvements	76.7	76.7
Equipment	37.4	33.7
Northern Virginia - Sterling II
Real Estate Properties [Line Items]
Land	0	0
Building and Improvements	28.8	28.7
Equipment	112.3	111.8
Somerset I
Real Estate Properties [Line Items]
Land	12.1	0
Building and Improvements	124.8	0
Equipment	83.7	0
Chicago - Aurora I
Real Estate Properties [Line Items]
Land	2.4	2.4
Building and Improvements	32.4	28.5
Equipment	125	99.9
Totowa - Madison
Real Estate Properties [Line Items]
Land	0	0
Building and Improvements	28.5	28.3
Equipment	55.1	50.8
Cincinnati - North Cincinnati
Real Estate Properties [Line Items]
Land	4	4
Building and Improvements	77.4	77.3
Equipment	9.9	9
San Antonio III
Real Estate Properties [Line Items]
Land	0	0
Building and Improvements	40.3	0
Equipment	96.8	0
Houston - Houston West II
Real Estate Properties [Line Items]
Land	2.8	2.8
Building and Improvements	22.8	23.1
Equipment	50.1	49
Wappingers Falls I
Real Estate Properties [Line Items]
Land	0	0
Building and Improvements	11.3	11.3
Equipment	18	17.1
San Antonio I
Real Estate Properties [Line Items]
Land	4.6	4.6
Building and Improvements	31.7	32.1
Equipment	34.8	33.6
Phoenix - Chandler II
Real Estate Properties [Line Items]
Land	0	0
Building and Improvements	16.2	16.1
Equipment	38.9	38.8
Northern Virginia - Sterling I
Real Estate Properties [Line Items]
Land	7	7
Building and Improvements	20	19.7
Equipment	59.4	47.2
Raleigh-Durham I
Real Estate Properties [Line Items]
Land	2.1	0
Building and Improvements	78	0
Equipment	76	0
Houston - Galleria
Real Estate Properties [Line Items]
Land	0	0
Building and Improvements	68.6	68.6
Equipment	17.6	16.6
Phoenix - Chandler I
Real Estate Properties [Line Items]
Land	14.8	14.8
Building and Improvements	58.2	56.8
Equipment	65.9	56.5
Phoenix - Chandler III
Real Estate Properties [Line Items]
Land	0	0
Building and Improvements	11.4	9.9
Equipment	50	44.5
Northern Virginia - Sterling III
Real Estate Properties [Line Items]
Land	0	0
Building and Improvements	22.2	0
Equipment	61.3	0
Austin II
Real Estate Properties [Line Items]
Land	2	2
Building and Improvements	23.4	23.4
Equipment	7	6.6
San Antonio II
Real Estate Properties [Line Items]
Land	7	7
Building and Improvements	29	29
Equipment	60.4	59.4
Florence
Real Estate Properties [Line Items]
Land	2.2	2.2
Building and Improvements	42	41.9
Equipment	5.3	4.9
Phoenix - Chandler IV
Real Estate Properties [Line Items]
Land	0	0
Building and Improvements	18.3	0
Equipment	40.9	0
Cincinnati - Hamilton
Real Estate Properties [Line Items]
Land	0	0
Building and Improvements	50.2	50.2
Equipment	6	5
London - Great Bridgewater
Real Estate Properties [Line Items]
Land	0	0
Building and Improvements	28.4	25.9
Equipment	1.1	0.9
Northern Virginia - Sterling IV
Real Estate Properties [Line Items]
Land	4.6	4.6
Building and Improvements	20	11
Equipment	73.7	33.4
Cincinnati - Mason
Real Estate Properties [Line Items]
Land	0	0
Building and Improvements	20.3	20.2
Equipment	1.6	1.4
Dallas - Midway
Real Estate Properties [Line Items]
Land	0	0
Building and Improvements	2	2
Equipment	0.4	0.4
Phoenix - Chandler VI
Real Estate Properties [Line Items]
Land	10.5	10.5
Building and Improvements	15.7	0
Equipment	49.2	0
Stamford - Riverbend
Real Estate Properties [Line Items]
Land	0	0
Building and Improvements	2.9	4.3
Equipment	6.9	14.5
Norwalk I
Real Estate Properties [Line Items]
Land	0	0
Building and Improvements	13.5	19
Equipment	9.4	26.6
Dallas - Marsh
Real Estate Properties [Line Items]
Land	0	0
Building and Improvements	0.1	0.1
Equipment	0.6	0.6
Chicago - Lombard
Real Estate Properties [Line Items]
Land	0.7	0.7
Building and Improvements	4.7	4.7
Equipment	7.7	7.9
Stamford - Omega
Real Estate Properties [Line Items]
Land	0	0
Building and Improvements	2.6	3.2
Equipment	0.7	1.5
Totowa - Commerce
Real Estate Properties [Line Items]
Land	0	0
Building and Improvements	4.1	4.1
Equipment	1.6	1.4
Cincinnati - Blue Ash
Real Estate Properties [Line Items]
Land	0	0
Building and Improvements	0.7	0.6
Equipment	0.2	0.1
South Bend - Crescent
Real Estate Properties [Line Items]
Land	0	0
Building and Improvements	1.7	1.7
Equipment	0.1	0.2
Houston - Houston West III
Real Estate Properties [Line Items]
Land	18.4	18.4
Building and Improvements	17.9	9.4
Equipment	30.7	13.5
Singapore - Inter Business Park
Real Estate Properties [Line Items]
Land	0	0
Building and Improvements	0	8.2
Equipment	0	0.1
South Bend - Monroe
Real Estate Properties [Line Items]
Land	0	0
Building and Improvements	2.5	2.5
Equipment	0.3	0.3
Cincinnati - Goldcoast
Real Estate Properties [Line Items]
Land	0.2	0.2
Building and Improvements	4	4
Equipment	0.1	0.1
Austin III
Real Estate Properties [Line Items]
Land	3.3	3.3
Building and Improvements	10.6	9.7
Equipment	33.9	31.8
Northern Virginia - Sterling V
Real Estate Properties [Line Items]
Land	24.1	24.1
Building and Improvements	35.7	0
Equipment	108.8	0
Phoenix - Chandler V
Real Estate Properties [Line Items]
Land	0	0
Building and Improvements	5.9	0
Equipment	20.5	0
San Antonio IV
Real Estate Properties [Line Items]
Land	0	0
Building and Improvements	0	0
Equipment	17.9	0
Austin I
Real Estate Properties [Line Items]
Land	0	0
Building and Improvements	0	3.5
Equipment	0	0.2
Austin Land A
Real Estate Properties [Line Items]
Land	8	8
Building and Improvements	0	0
Equipment	0.2	0.2
Chicago - Aurora II
Real Estate Properties [Line Items]
Land	2.6	2.6
Building and Improvements	8.3	0
Equipment	42.9	0
Chicago - Aurora Land B
Real Estate Properties [Line Items]
Land	5.1	5.1
Building and Improvements	0	0
Equipment	0	0
Dallas - Allen
Real Estate Properties [Line Items]
Land	12	0
Building and Improvements	0	0
Equipment	0	0
Quincy Land A
Real Estate Properties [Line Items]
Land	3.1	0
Building and Improvements	0	0
Equipment	0	0
Atlanta I
Real Estate Properties [Line Items]
Land	5.1	0
Building and Improvements	0	0
Equipment	$ 0	$ 0

Investment in Real Estate - Nar

Investment in Real Estate - Narrative (Details) $ in Millions	Feb. 28, 2017USD ($)	Dec. 31, 2017USD ($)	Dec. 31, 2016USD ($)property	Dec. 31, 2015USD ($)
Real Estate Properties [Line Items]
Cost of construction in progress		$ 478.4	$ 407.1
Capital expenditures		1,406.8	731.1
Capital expenditures – purchase of fixed assets		492.3	131.1	$ 17.3
Capital expenditures – other development		914.5	600	217.2
Asset impairments and loss on disposal		$ 59.5	$ 5.3	$ 13.5
Lease Sales Cycle		2 years
Number of Properties Impaired | property			2
Property for development, Northern Virginia, Phoenix, Dallas, Chicago, San Antonio and Cincinnati; Purchase of land parcels, Allen, Texas and Quincy, Washington
Real Estate Properties [Line Items]
Capital expenditures – purchase of fixed assets		$ 914.5
Aurora Properties
Real Estate Properties [Line Items]
Capital expenditures – other development			$ 131.1
Property for development, Northern Virginia - Sterling, Chicago - Aurora and Phoenix - Chandler II
Real Estate Properties [Line Items]
Capital expenditures – purchase of fixed assets			$ 54.5
Number of properties purchased | property			4
Property for development, Northern Virginia - Sterling, Phoenix - Chandler II, San Antonio, Dallas - Carrollton and Houston - Houston West III
Real Estate Properties [Line Items]
Capital expenditures – purchase of fixed assets			$ 545.5
Norwalk I, Stamford - Riverbend and Stamford - Omega Facilities
Real Estate Properties [Line Items]
Asset impairments and loss on disposal		54.4
Singapore Facility
Real Estate Properties [Line Items]
Asset impairments and loss on disposal		3.6
Chicago - Aurora Facility
Real Estate Properties [Line Items]
Loss on disposal		1.1
Other equipment
Real Estate Properties [Line Items]
Loss on disposal		$ 0.4
Sentinel Properties
Real Estate Properties [Line Items]
Consideration for acquisition	$ 492.3

Notes Receivable - Narrative (D

Notes Receivable - Narrative (Details) - USD ($)	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016
Accounts, Notes, Loans and Financing Receivable [Line Items]
Carrying amount notes receivable	$ 3,300,000	$ 6,600,000
Note 1
Accounts, Notes, Loans and Financing Receivable [Line Items]
Carrying amount notes receivable	1,800,000	2,200,000
Monthly payments	50,000
Note 2
Accounts, Notes, Loans and Financing Receivable [Line Items]
Carrying amount notes receivable	600,000	0
Monthly payments	26,000
Note 3
Accounts, Notes, Loans and Financing Receivable [Line Items]
Carrying amount notes receivable	500,000	3,900,000
Monthly payments	300,000
Note 4
Accounts, Notes, Loans and Financing Receivable [Line Items]
Carrying amount notes receivable	400,000	$ 500,000
Monthly payments	$ 12,000

Notes Receivable - Carrying amo

Notes Receivable - Carrying amounts (Details) - USD ($) $ in Millions	Dec. 31, 2017	Dec. 31, 2016
Accounts, Notes, Loans and Financing Receivable [Line Items]
Carrying amount notes receivable	$ 3.3	$ 6.6
Note 1
Accounts, Notes, Loans and Financing Receivable [Line Items]
Carrying amount notes receivable	1.8	2.2
Note 2
Accounts, Notes, Loans and Financing Receivable [Line Items]
Carrying amount notes receivable	0.6	0
Note 3
Accounts, Notes, Loans and Financing Receivable [Line Items]
Carrying amount notes receivable	0.5	3.9
Note 4
Accounts, Notes, Loans and Financing Receivable [Line Items]
Carrying amount notes receivable	$ 0.4	$ 0.5

Goodwill, Intangible and Othe64

Goodwill, Intangible and Other Long-Lived Assets - Narrative (Details) - USD ($)	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Goodwill and Intangible Assets Disclosure [Abstract]
Goodwill	$ 455,100,000	$ 455,100,000
Impairment of intangible assets	0	0
Impairment of goodwill	0	0	$ 0
Amortization expense for intangible assets	$ 25,100,000	$ 20,100,000	$ 18,500,000

Goodwill, Intangible and Othe65

Goodwill, Intangible and Other Long-Lived Assets - Carrying Value of Major Classes of Intangible Assets (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016
Finite-Lived Intangible Assets [Line Items]
Gross Carrying Amount	$ 339.1	$ 260.9
Accumulated Amortization	(136.1)	(110.7)
Total	$ 203	150.2
Customer relationships
Finite-Lived Intangible Assets [Line Items]
Weighted- Average Remaining Life (in years)	11 years
Gross Carrying Amount	$ 247.1	247.1
Accumulated Amortization	(123)	(106.3)
Total	$ 124.1	140.8
Trademark/tradename
Finite-Lived Intangible Assets [Line Items]
Weighted- Average Remaining Life (in years)	6 years
Gross Carrying Amount	$ 9.7	9.7
Accumulated Amortization	(5.3)	(3.9)
Total	$ 4.4	5.8
Favorable leasehold interest
Finite-Lived Intangible Assets [Line Items]
Weighted- Average Remaining Life (in years)	47 years
Gross Carrying Amount	$ 4.1	4.1
Accumulated Amortization	(0.5)	(0.5)
Total	$ 3.6	3.6
In place customer leases
Finite-Lived Intangible Assets [Line Items]
Weighted- Average Remaining Life (in years)	8 years
Gross Carrying Amount	$ 75.9	0
Accumulated Amortization	(7.1)	0
Total	$ 68.8	0
Above and below market leases
Finite-Lived Intangible Assets [Line Items]
Weighted- Average Remaining Life (in years)	8 years
Gross Carrying Amount	$ 2.3	0
Accumulated Amortization	(0.2)	0
Total	$ 2.1	$ 0

Goodwill, Intangible and Othe66

Goodwill, Intangible and Other Long-Lived Assets - Estimated Amortization Expense For Finite-Lived Intangible Assets (Details) - USD ($) $ in Millions	Dec. 31, 2017	Dec. 31, 2016
Goodwill and Intangible Assets Disclosure [Abstract]
2,018	$ 24.7
2,019	22.4
2,020	21.3
2,021	20.3
2,022	19.7
Thereafter	94.6
Total	$ 203	$ 150.2

Long-Term Debt, Capital Lease67

Long-Term Debt, Capital Lease Obligations and Lease Financing Arrangements - Long-Term Debt and Capital Lease Obligations (Details) - USD ($)	Dec. 31, 2017	Mar. 30, 2017	Dec. 31, 2016	Nov. 21, 2016
Debt Instrument [Line Items]
Long-term debt, net	$ 2,089,400,000		$ 1,240,100,000
Deferred financing costs	(27,900,000)		(22,200,000)
Capital lease obligations	10,100,000		10,800,000
Lease financing arrangements	131,900,000		135,700,000
Total	2,231,400,000		1,386,600,000
Term Loan
Debt Instrument [Line Items]
Credit facilities	900,000,000
Senior Notes | 2024 Notes, including bond premium
Debt Instrument [Line Items]
Long-term debt, net	706,800,000		0
Senior Notes | 2027 Notes, including bond premium
Debt Instrument [Line Items]
Long-term debt, net	510,500,000		0
Senior Notes | 2022 Notes, including bond premium
Debt Instrument [Line Items]
Long-term debt, net	0	$ 474,800,000	477,300,000
Revolving Credit Facility
Debt Instrument [Line Items]
Credit facilities	0		235,000,000
Deferred financing costs				$ (6,600,000)
Revolving Credit Facility | Term Loan | 2022 Term Loan
Debt Instrument [Line Items]
Credit facilities	650,000,000		300,000,000
Revolving Credit Facility | Term Loan | 2021 Term Loan
Debt Instrument [Line Items]
Credit facilities	$ 250,000,000		$ 250,000,000

Long-Term Debt, Capital Lease68

Long-Term Debt, Capital Lease Obligations and Lease Financing Arrangements - Narrative (Details)	Nov. 03, 2017USD ($)	Jun. 16, 2017USD ($)	Mar. 17, 2017USD ($)	Mar. 31, 2017USD ($)	Jul. 31, 2016USD ($)	Dec. 31, 2017USD ($)data_center	Dec. 31, 2016USD ($)	Dec. 31, 2015USD ($)	Mar. 30, 2017USD ($)	Nov. 21, 2016USD ($)	Mar. 17, 2016USD ($)	Jul. 01, 2015	Jun. 22, 2015USD ($)	Oct. 09, 2014USD ($)	Nov. 20, 2012USD ($)
Debt Instrument [Line Items]
Deferred financing costs						$ 27,900,000	$ 22,200,000
Letters of credit outstanding						8,500,000
Total liquidity						1,243,400,000
Cash and cash equivalents						151,900,000	14,600,000
Long-term debt, net						$ 2,089,400,000	1,240,100,000
Total unencumbered assets						150.00%
Repayment of note payable					$ 1,500,000	$ 0	1,500,000	$ 0
Amortization of deferred financing costs						$ 4,700,000	4,100,000	3,400,000
Number of data center facilities under capital lease | data_center						4
Interest expense on capital lease obligations and lease financing arrangements						$ 9,000,000	10,600,000	$ 7,800,000
Capital Leases, Future Minimum Payments Due, Fiscal Year Maturity [Abstract]
2,018						14,900,000
2,019						15,100,000
2,020						27,800,000
2,021						11,500,000
2,022						11,800,000
Thereafter						100,600,000
Interest on capital leases
Capital Leases, Future Minimum Payments Due, Fiscal Year Maturity [Abstract]
2,018						800,000
2,019						600,000
2,020						500,000
2,021						300,000
2,022						100,000
Thereafter						100,000
First Amended and Restated Credit Agreement
Debt Instrument [Line Items]
Deferred financing costs											$ 2,100,000
Second Amended and Restated Credit Agreement
Debt Instrument [Line Items]
Credit agreement amount		$ 2,000,000,000
Optional additional borrowing capacity		450,000,000
Deferred financing costs						2,700,000
Credit facility, available capacity under accordion feature		2,300,000,000				300,000,000
Write off of deferred financing costs						$ 300,000
Term Loan
Debt Instrument [Line Items]
Credit agreement amount													$ 300,000,000
Face amount of debt														$ 150,000,000
Remaining borrowing capacity													250,000,000
Effective interest rate						2.99%
Outstanding borrowings on revolving credit agreement						$ 900,000,000
Term Loan | LIBOR
Debt Instrument [Line Items]
Basis spread on variable rate						1.50%
Term Loan | 2021 Term Loan
Debt Instrument [Line Items]
Optional additional borrowing capacity											250,000,000
Term Loan | 2022 Term Loan
Debt Instrument [Line Items]
Credit agreement amount		650,000,000									300,000,000
Optional additional borrowing capacity		350,000,000
Senior Notes | 5.000% Senior Notes Due 2024 and 5.375% Senior Notes Due 2027 [Member]
Debt Instrument [Line Items]
Debt proceeds, net of underwriting costs	$ 416,100,000		$ 791,200,000
Debt underwriting costs	4,400,000		8,800,000
Other debt issuance costs	1,000,000		2,100,000
Bond premium included in proceeds	17,800,000
Accrued interest included in proceeds	2,700,000
Senior Notes | 5.000% Senior Notes Due 2024 and 5.375% Senior Notes Due 2027 [Member] | CyrusOne LP and CyrusOne Finance Corp
Debt Instrument [Line Items]
Debt underwriting costs			$ 10,900,000
Senior Notes | 5.000% senior notes due 2024
Debt Instrument [Line Items]
Long-term debt, net						$ 706,800,000	0
Senior Notes | 5.000% senior notes due 2024 | Redemption period one
Debt Instrument [Line Items]
Debt redemption percentage			100.00%
Senior Notes | 5.000% senior notes due 2024 | Redemption period two
Debt Instrument [Line Items]
Debt redemption percentage			102.50%
Senior Notes | 5.000% senior notes due 2024 | Redemption period three
Debt Instrument [Line Items]
Debt redemption percentage			101.25%
Senior Notes | 5.000% senior notes due 2024 | Redemption period five
Debt Instrument [Line Items]
Debt redemption percentage			100.00%
Senior Notes | 5.000% senior notes due 2024 | Redemption period six
Debt Instrument [Line Items]
Debt redemption percentage			40.00%
Debt redemption, percentage of certain equity offerings			105.00%
Debt redemption, percentage to remain outstanding			55.00%
Debt redemption, period after equity offering closing			90 days
Senior Notes | 5.000% senior notes due 2024 | CyrusOne LP and CyrusOne Finance Corp
Debt Instrument [Line Items]
Face amount of debt	$ 200,000,000		$ 500,000,000			706,800,000
Stated interest rate	5.00%		5.00%
Senior Notes | 5.375% senior notes due 2027
Debt Instrument [Line Items]
Long-term debt, net						510,500,000	0
Senior Notes | 5.375% senior notes due 2027 | Redemption period one
Debt Instrument [Line Items]
Debt redemption percentage			100.00%
Senior Notes | 5.375% senior notes due 2027 | Redemption period two
Debt Instrument [Line Items]
Debt redemption percentage			102.688%
Senior Notes | 5.375% senior notes due 2027 | Redemption period three
Debt Instrument [Line Items]
Debt redemption percentage			101.792%
Senior Notes | 5.375% senior notes due 2027 | Redemption period four
Debt Instrument [Line Items]
Debt redemption percentage			100.896%
Senior Notes | 5.375% senior notes due 2027 | Redemption period five
Debt Instrument [Line Items]
Debt redemption percentage			100.00%
Senior Notes | 5.375% senior notes due 2027 | Redemption period six
Debt Instrument [Line Items]
Debt redemption percentage			40.00%
Debt redemption, percentage of certain equity offerings			105.375%
Debt redemption, percentage to remain outstanding			55.00%
Debt redemption, period after equity offering closing			90 days
Senior Notes | 5.375% senior notes due 2027 | CyrusOne LP and CyrusOne Finance Corp
Debt Instrument [Line Items]
Face amount of debt	$ 200,000,000		$ 300,000,000			510,500,000
Stated interest rate	5.375%		5.375%
Senior Notes | 6.375% senior notes due 2022
Debt Instrument [Line Items]
Long-term debt, net						0	477,300,000		$ 474,800,000
Repurchase amount				$ 515,100,000
Repurchase amount, accrued and unpaid interest				10,300,000
Deferred financing costs, bond premium and legal fees written off				6,200,000
Loss on extinguishment of debt				$ 36,200,000
Senior Notes | 6.375% senior notes due 2022 | CyrusOne LP and CyrusOne Finance Corp
Debt Instrument [Line Items]
Stated interest rate												6.375%			6.375%
Long-term debt, net															$ 525,000,000
Revolving Credit Facility
Debt Instrument [Line Items]
Credit agreement amount		1,100,000,000				1,100,000,000				$ 1,000,000,000	$ 650,000,000		$ 650,000,000	$ 450,000,000
Remaining borrowing capacity						$ 1,091,500,000
Optional additional borrowing capacity		$ 100,000,000
Deferred financing costs										$ 6,600,000
Term of extension option		1 year
Commitment fee percent						0.25%
Outstanding borrowings on revolving credit agreement						$ 0	235,000,000
Maximum percentage of dividends allowed to be distributed						95.00%
Revolving Credit Facility | LIBOR
Debt Instrument [Line Items]
Basis spread on variable rate						1.55%
Revolving Credit Facility | Second Amended and Restated Credit Agreement
Debt Instrument [Line Items]
Commitment fee amount						$ 1,900,000	1,600,000
Revolving Credit Facility | Term Loan | 2021 Term Loan
Debt Instrument [Line Items]
Outstanding borrowings on revolving credit agreement						250,000,000	250,000,000
Revolving Credit Facility | Term Loan | 2022 Term Loan
Debt Instrument [Line Items]
Outstanding borrowings on revolving credit agreement						$ 650,000,000	$ 300,000,000

Long-Term Debt, Capital Lease69

Long-Term Debt, Capital Lease Obligations and Lease Financing Arrangements - Lease Financing Arrangements (Details) $ in Millions	Dec. 31, 2017USD ($)
Future Value of Payments
2,018	$ 14.9
2,019	15.1
2,020	27.8
2,021	11.5
2,022	11.8
Thereafter	100.6
Total lease financing arrangements	181.7
Interest
2,018	7.9
2,019	7.4
2,020	6.8
2,021	5.8
2,022	5.5
Thereafter	16.4
Total lease financing arrangements	49.8
2,018	7
2,019	7.7
2,020	21
2,021	5.7
2,022	6.3
Thereafter	84.2
Total lease financing arrangements	$ 131.9

Long-Term Debt, Capital Lease70

Long-Term Debt, Capital Lease Obligations and Lease Financing Arrangements - Maturities of Debt (Details) $ in Millions	Dec. 31, 2017USD ($)
Debt Instrument [Line Items]
2,018	$ 2
2,019	1.9
2,020	2
2,021	252
2,022	650.9
Thereafter	1,201.3
Total debt	2,110.1
Revolving Credit Facility/Term Loans
Debt Instrument [Line Items]
2,018	0
2,019	0
2,020	0
2,021	250
2,022	650
Thereafter	0
Total debt	900
Senior Notes
Debt Instrument [Line Items]
2,018	0
2,019	0
2,020	0
2,021	0
2,022	0
Thereafter	1,200
Total debt	1,200
Capital Leases
Debt Instrument [Line Items]
2,018	2
2,019	1.9
2,020	2
2,021	2
2,022	0.9
Thereafter	1.3
Total debt	$ 10.1

Fair Value Measurements - Carry

Fair Value Measurements - Carrying and Fair Value (Details) - USD ($)	Dec. 31, 2017	Mar. 30, 2017	Dec. 31, 2016
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Long-term debt, net	$ 2,089,400,000		$ 1,240,100,000
Carrying Value
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Equity investment	100,000,000		0
Fair Value
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Equity investment	175,600,000		0
Senior Notes | 2024 Notes, including bond premium
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Long-term debt, net	706,800,000		0
Senior Notes | 2027 Notes, including bond premium
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Long-term debt, net	510,500,000		0
Senior Notes | 2022 Notes, including bond premium
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Long-term debt, net	0	$ 474,800,000	477,300,000
Senior Notes | Carrying Value | 2024 Notes, including bond premium
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Long-term debt, net	706,800,000		0
Senior Notes | Carrying Value | 2027 Notes, including bond premium
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Long-term debt, net	510,500,000		0
Senior Notes | Carrying Value | 2022 Notes, including bond premium
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Long-term debt, net	0		477,300,000
Senior Notes | Fair Value | 2024 Notes, including bond premium
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Long-term debt, net	728,000,000		0
Senior Notes | Fair Value | 2027 Notes, including bond premium
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Long-term debt, net	527,500,000		0
Senior Notes | Fair Value | 2022 Notes, including bond premium
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Long-term debt, net	0		502,100,000
Revolving Credit Facility
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Credit facilities	0		235,000,000
Revolving Credit Facility | Carrying Value
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Credit facilities	900,000,000		785,000,000
Revolving Credit Facility | Fair Value
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Credit facilities	$ 900,000,000		$ 785,000,000

Fair Value Measurements - Narra

Fair Value Measurements - Narrative (Details) - USD ($) $ / shares in Units, $ in Millions	Oct. 18, 2017	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Deferred financing costs		$ 27.9	$ 22.2
Discount rate	4.00%
American depository shares equivalent (in shares)	8
Unrealized gain on equity investment		75.6
Impairment charges		59.5	5.3	$ 13.5
American depository shares
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
American depository share (in shares)	8,000,000
Price per ordinary share (in dollars per shares)	$ 12.45
Total investment	$ 100
Fair Value
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Equity investment		175.6	$ 0
Norwalk I, Stamford - Riverbend and Stamford - Omega Facilities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Impairment charges		54.4
Fair value of assets at time of impairment		$ 31.7
Level 3 | Norwalk I, Stamford - Riverbend and Stamford - Omega Facilities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Discount rate		12.00%
Long-term growth rate		3.00%
Market rent and expense growth rate		2.00%
Capitalization rate		9.00%

Noncontrolling Interest - Ope73

Noncontrolling Interest - Operating Partnership - Narrative (Details)	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Non-Controlling Interest
Noncontrolling Interest [Line Items]
Ownership %, 2017 and 2016 less than	0.00%		0.00%
Cincinnati Bell Inc.
Noncontrolling Interest [Line Items]
Ownership %, 2017 and 2016 less than	5.00%	5.00%	9.50%

Noncontrolling Interest - Ope74

Noncontrolling Interest - Operating Partnership - Schedule of Noncontrolling Interest (Details) - USD ($) shares in Millions, $ in Millions	3 Months Ended								12 Months Ended
	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Noncontrolling Interest [Line Items]
Portion of net loss	$ 2.8	$ (55.1)	$ (0.8)	$ (30.4)	$ 0.8	$ 4.4	$ 9.1	$ 5.6	$ (83.5)	$ 19.9	$ (15.4)
Portion of net loss									0	0	(4.8)
Distributions									$ (153.6)	(123.8)	$ (90.9)
The Company
Noncontrolling Interest [Line Items]
Operating partnership units (in shares)	96.1								96.1		72.6
Ownership %											100.00%
Portion of net loss											$ (15.4)
Portion of net loss											4.8
Distributions									$ (153.6)	(123.8)	$ (74.6)
CBI
Noncontrolling Interest [Line Items]
Operating partnership units (in shares)											0
Ownership %	0.00%								0.00%		0.00%
Portion of net loss											$ (4.8)
Distributions										$ 0	$ (16.3)

Dividends (Details)

Dividends (Details) - USD ($) $ / shares in Units, $ in Millions	Feb. 21, 2018	Jan. 12, 2018	Oct. 13, 2017	Jul. 14, 2017	Apr. 14, 2017	Jan. 13, 2017	Oct. 14, 2016	Jul. 15, 2016	Apr. 15, 2016	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Dividends Payable [Line Items]
Cash dividend per share or operating partnership unit (in dollars per share)			$ 0.42	$ 0.42	$ 0.42	$ 0.38	$ 0.38	$ 0.38	$ 0.38	$ 1.64	$ 1.46
Dividends payable										$ 41.8	$ 33.9
Dividends declared per share (in dollars per share)										$ 1.68	$ 1.52	$ 1.26
Subsequent event
Dividends Payable [Line Items]
Cash dividend per share or operating partnership unit (in dollars per share)		$ 0.42
Dividends declared per share (in dollars per share)	$ 0.46

Customer Leases (Details)

Customer Leases (Details) $ in Millions	Dec. 31, 2017USD ($)
Leases [Abstract]
2,018	$ 530.2
2,019	414.1
2,020	352.5
2,021	289.2
2,022	$ 231.1

Employee Benefit Plans (Details

Employee Benefit Plans (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Retirement Benefits [Abstract]
Health care plans expenses	$ 2.7	$ 4.4	$ 3.1
Retirement savings plan matching contributions	$ 1.5	$ 1.5	$ 1.1

(Loss) Income per Share - Narra

(Loss) Income per Share - Narrative (Details) - USD ($) shares in Millions	Aug. 15, 2016	Aug. 10, 2016	Dec. 31, 2015	Dec. 14, 2015	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Business Formation [Line Items]
Proceeds from public stock offerings					$ 706,000,000	$ 448,700,000	$ 799,500,000
Stock issuance costs					$ 300,000	$ 1,600,000	$ 800,000
Public stock offering
Business Formation [Line Items]
Issuance of common stock (in shares)	3.4		6.3	1.4	8.4	10.3	27.3	16
Proceeds from public stock offerings	$ 164,800,000			$ 0	$ 493,700,000	$ 419,800,000	$ 799,300,000	$ 355,900,000
Stock issuance costs	$ 6,900,000				$ 6,300,000
Stock issued upon underwriters exercising option to purchase additional shares
Business Formation [Line Items]
Issuance of common stock (in shares)		1

(Loss) Income per Share - Compu

(Loss) Income per Share - Computation of Basic and Diluted Net (Loss) Income Per Share (Details) - USD ($) $ / shares in Units, shares in Millions, $ in Millions	3 Months Ended								12 Months Ended
	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Numerator:
Net (loss) income attributed to common stockholders	$ 2.8	$ (55.1)	$ (0.8)	$ (30.4)	$ 0.8	$ 4.4	$ 9.1	$ 5.6	$ (83.5)	$ 19.9	$ (15.4)
Less: Restricted stock dividends, Basic									(0.9)	(0.7)	(1)
Less: Restricted stock dividends, Diluted									(0.9)	(0.7)	(1)
Net (loss) income available to stockholders, Basic									(84.4)	19.2	(16.4)
Net (loss) income available to stockholders, Diluted									$ (84.4)	$ 19.2	$ (16.4)
Denominator:
Weighted average common outstanding - basic (in shares)									88.9	78.3	54.3
Performance-based restricted stock and units (in shares)									0	0.7	0
Weighted average shares outstanding- diluted (in shares)									88.9	79	54.3
EPS:
Net (loss) income per share- basic (in dollars per share)									$ (0.95)	$ 0.24	$ (0.30)
Net (loss) income per share - diluted (in dollars per share)									$ (0.95)	$ 0.24	$ (0.30)
Restricted Stock
EPS:
Anti-dilutive securities excluded from diluted earnings per share (in shares)									0.4		1.9
Stock options
EPS:
Anti-dilutive securities excluded from diluted earnings per share (in shares)									0.1		13.1

Stock-Based Compensation Plan80

Stock-Based Compensation Plans - Allocated Share-based Compensation Expense (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]
Total compensation expense	$ 14.7	$ 12.3	$ 14.4
2013 Grants
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]
Total compensation expense	0	0.1	1.2
2014 Grants
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]
Total compensation expense	0.1	1.2	3
2015 Grants
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]
Total compensation expense	1.8	3.5	5
2016 Grants
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]
Total compensation expense	6.6	7.2	0
2017 Grants
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]
Total compensation expense	6.2	0	0
Founders
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]
Total compensation expense	$ 0	$ 0.3	$ 5.2

Stock-Based Compensation Plan81

Stock-Based Compensation Plans - Narrative (Details)	Feb. 13, 2017$ / sharesshares	Feb. 01, 2016$ / sharesshares	Feb. 10, 2015	Feb. 07, 2014	Apr. 17, 2013$ / shares	Jan. 24, 2013USD ($)shares	Dec. 31, 2017USD ($)$ / sharesshares	Dec. 31, 2016USD ($)shares	Dec. 31, 2015USD ($)executiveshares	Dec. 31, 2014USD ($)shares	Dec. 31, 2013USD ($)
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Grant date fair value (in dollars per share) | $ / shares							$ 0
Outstanding options (in shares) | shares							415,459	434,268	334,402
Intrinsic vale of options exercised | $							$ 500,000	$ 1,300,000
Intrinsic value of options outstanding | $							11,600,000
Intrinsic value of options exercisable | $							7,100,000
2013 Grants
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Total awards grant date fair value | $											$ 25,400,000
Unrecognized compensation expense, other than options | $							0
2014 Grants
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Total awards grant date fair value | $										$ 12,900,000
Unrecognized compensation expense, other than options | $							0
2015 Grants
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Total awards grant date fair value | $									$ 13,800,000
Unrecognized compensation expense, other than options | $							$ 300,000
Unrecognized compensation expense, period for recognition							2 months 6 days
2016 Grants
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Total awards grant date fair value | $								$ 22,600,000
Unrecognized compensation expense, other than options | $							$ 7,100,000
Unrecognized compensation expense, period for recognition							1 year 1 month 18 days
2017 Grants
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Cap on award vesting in first two years							100.00%
Total awards grant date fair value | $							$ 15,900,000
Unrecognized compensation expense, other than options | $							$ 9,500,000
Unrecognized compensation expense, period for recognition							1 year 7 months 18 days
Restricted stock
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Grants in period (in shares) | shares							287,395
Granted (in dollars per share) | $ / shares							$ 55.46
Non-vested balance (in shares) | shares							980,100	1,274,713	1,585,010
Restricted stock | 2014 Grants
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Award vesting period										3 years
Grants in period (in shares) | shares										46,313
Other than options grant date value | $										$ 1,000,000
Restricted stock | 2014 Grants | Cliff Vesting
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Award vesting period										1 year
Restricted stock | 2015 Grants
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Award vesting period			3 years
Award vesting rights percentage			20.00%
Grants in period (in shares) | shares									50,300
Restricted stock | 2016 Grants
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Award vesting period		3 years						3 years
Grants in period (in shares) | shares								47,667
Restricted stock | 2016 Grants | Cliff Vesting
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Award vesting period		3 years
Grants in period (in shares) | shares								5,894
Restricted stock | 2017 Grants
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Award vesting period	1 year
Grants in period (in shares) | shares	18,179
Time, performance, and market-based awards | 2016 Grants
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Grants in period (in shares) | shares		641,097
Performance and market-based awards | 2015 Grants
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Award vesting period			3 years
Cap on award vesting in first two years		100.00%
Award vesting rights percentage			80.00%
True-up cap on award vesting for year three			200.00%
Performance and market-based awards | 2016 Grants
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Award vesting period		3 years
Cap on award vesting in first two years		100.00%
True-up cap on award vesting for year three		200.00%
Performance awards | 2013 Grants
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Award vesting period					3 years
Award vesting rights percentage					50.00%
Performance awards | 2014 Grants
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Award vesting rights percentage				50.00%
Performance awards | 2014 Grants | Below 90% of EBITDA Target
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Award vesting rights percentage				0.00%
Performance awards | 2014 Grants | At 90% of EBITDA Target
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Award vesting rights percentage				50.00%
Performance awards | 2014 Grants | At 100% of EBITDA Target
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Award vesting rights percentage				100.00%
Performance awards | 2014 Grants | At or above 115% of EBITDA Target
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Award vesting rights percentage				200.00%
Performance awards | 2015 Grants
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Grants in period (in shares) | shares									67,012
Performance awards | 2015 Grants | Cliff Vesting
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Award vesting period									3 years
Time and performance based, restricted stock | 2016 Grants
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Granted (in dollars per share) | $ / shares		$ 36.99
Market-based restricted stock
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Award vesting period							3 years
Market-based restricted stock | If CyrusOne's total stockholder return is less than the return of the Index
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Award vesting rights percentage							0.00%
Market-based restricted stock | If CyrusOne's total stockholder return is equal to or greater than the return of the Index
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Award vesting rights percentage							100.00%
Market-based restricted stock | if CyrusOne's total stockholder return exceeds the return of the Index by 2%
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Award vesting rights percentage							200.00%
Market-based restricted stock | If CyrusOne's total stockholder return exceeds the return of the Index, but is negative
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Award vesting rights percentage							50.00%
Market-based restricted stock | 2013 Grants
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Award vesting rights percentage					50.00%
Market-based restricted stock | 2014 Grants
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Award vesting period				3 years
Award vesting rights percentage				50.00%
Market-based restricted stock | 2016 Grants
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Granted (in dollars per share) | $ / shares		$ 43.66
Market-based restricted stock | 2017 Grants
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Grants in period (in shares) | shares	129,146
Granted (in dollars per share) | $ / shares	$ 63.23
Time-based restricted stock units and restricted stock | 2017 Grants
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Granted (in dollars per share) | $ / shares	$ 48.13
Time-based restricted units
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Term of dividends payable							10 days
Time-based restricted units | 2016 Grants | Cliff Vesting
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Award vesting period								3 years
Time-based restricted units | 2017 Grants
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Award vesting period	3 years						3 years
Grants in period (in shares) | shares	119,218						20,852
Stock options | 2013 Grants
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Expiration period for award					10 years
Weighted average exercise price for options granted (in dollars per share) | $ / shares					$ 23.58
Stock options | 2015 Grants
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Award vesting period			3 years
Stock options | 2016 Grants
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Award vesting period		3 years
Grants in period (in shares) | shares		222,461
Expiration period for award		10 years
Weighted average exercise price for options granted (in dollars per share) | $ / shares		$ 36.99
Grant date fair value (in dollars per share) | $ / shares		$ 6.99
Senior executives
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Accelerated compensation cost | $								$ 800,000	$ 2,400,000
Number of individuals with accelerated vesting | executive									2
Founders | Restricted stock
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Grants in period (in shares) | shares						1,000,000
Other than options grant date value | $						$ 19,000,000
2012 LTIP Plan
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares authorized (in shares) | shares							8,900,000
Shares available for grant (in shares) | shares							5,500,000
Minimum | Market-based restricted stock
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Performance percentage exceeding REIT index causing awards to vest							2.00%
Maximum | Market-based restricted stock
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Performance percentage exceeding REIT index causing awards to vest							200.00%

Stock-Based Compensation Plan82

Stock-Based Compensation Plans - Other Than Options (Details) - Restricted Stock - $ / shares	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016
Shares
Non-vested beginning balance (in shares)	1,274,713	1,585,010
Granted (in shares)	287,395
Vested (in shares)	(446,623)
Forfeited (in shares)	(135,385)
Non-vested ending balance (in shares)	980,100	1,274,713
Weighted Average Grant Date Fair Value
Non-vested beginning balance (in dollars per share)	$ 28.95
Granted (in dollars per share)	55.46
Vested (in dollars per share)	26.83
Forfeited (in dollars per share)	21.92
Non-vested ending balance (in dollars per share)	$ 38.66	$ 28.95

Stock-Based Compensation Plan83

Stock-Based Compensation Plans - Options (Details)	12 Months Ended
	Dec. 31, 2017$ / sharesshares
Options
Beginning balance (in shares) | shares	434,268
Granted (in shares) | shares	0
Exercised (in shares) | shares	(18,809)
Forfeited or expired (in shares) | shares	0
Ending balance (in shares) | shares	415,459
Exercisable (in shares) | shares	235,395
Vested and expected to vest (in shares) | shares	415,459
Weighted Average Exercise Price
Beginning balance (in dollars per share) | $ / shares	$ 31.89
Granted (in dollars per share) | $ / shares	0
Exercised (in dollars per share) | $ / shares	36.79
Forfeited or expired (in dollars per share) | $ / shares	0
Ending balance (in dollars per share) | $ / shares	31.67
Exercisable (in dollars per share) | $ / shares	29.45
Vested and expected to vest (in dollars per share) | $ / shares	$ 31.67

Stock-Based Compensation Plan84

Stock-Based Compensation Plans - Option Valuation Assumptions (Details) - $ / shares	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of shares (in shares)	415,459	434,268	334,402
Exercisable (in shares)	235,395
$ 23.58
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Exercise price (in dollars per share)			$ 23.58
Number of shares (in shares)			142,556
Weighted average outstanding contractual term (in years)			7 years 3 months 18 days
Exercisable (in shares)			43,460
Weighted average exercisable contractual term (in years)			7 years 3 months 18 days
Risk-free rate			0.92%
Expected annual dividend			3.40%
Expected term (in years)			6 years
Expected volatility			35.00%
$ 28.42
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Exercise price (in dollars per share)			$ 28.42
Number of shares (in shares)			178,704
Weighted average outstanding contractual term (in years)			9 years 1 month 6 days
Exercisable (in shares)			35,346
Weighted average exercisable contractual term (in years)			9 years 1 month 6 days
Expected annual dividend			4.40%
$ 30.74
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Exercise price (in dollars per share)			$ 30.74
Number of shares (in shares)			12,719
Weighted average outstanding contractual term (in years)			9 years 7 months 6 days
Exercisable (in shares)			0
Weighted average exercisable contractual term (in years)			0 years
Expected annual dividend			4.40%
$ 23.58
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Exercise price (in dollars per share)		$ 23.58
Number of shares (in shares)		67,601
Weighted average outstanding contractual term (in years)		6 years 3 months 18 days
Exercisable (in shares)		67,601
Weighted average exercisable contractual term (in years)		6 years 3 months 18 days
Risk-free rate		0.92%
Expected annual dividend		3.40%
Expected term (in years)		6 years
Expected volatility		35.00%
$ 28.42
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Exercise price (in dollars per share)		$ 28.42
Number of shares (in shares)		143,358
Weighted average outstanding contractual term (in years)		8 years 1 month 6 days
Exercisable (in shares)		47,786
Weighted average exercisable contractual term (in years)		8 years 1 month 6 days
Expected annual dividend		4.40%
$ 30.74
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Exercise price (in dollars per share)		$ 30.74
Number of shares (in shares)		12,719
Weighted average outstanding contractual term (in years)		8 years 7 months 6 days
Exercisable (in shares)		4,240
Weighted average exercisable contractual term (in years)		8 years 7 months 6 days
Expected annual dividend		4.40%
$ 36.99
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Exercise price (in dollars per share)		$ 36.99
Number of shares (in shares)		210,590
Weighted average outstanding contractual term (in years)		9 years 1 month 6 days
Exercisable (in shares)		18,530
Weighted average exercisable contractual term (in years)		9 years 1 month 6 days
Expected annual dividend		4.10%
$ 23.58
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Exercise price (in dollars per share)	$ 23.58
Number of shares (in shares)	67,322
Weighted average outstanding contractual term (in years)	5 years 3 months 18 days
Exercisable (in shares)	67,322
Weighted average exercisable contractual term (in years)	5 years 3 months 18 days
Risk-free rate	0.92%
Expected annual dividend	3.40%
Expected term (in years)	6 years
Expected volatility	35.00%
$ 28.42
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Exercise price (in dollars per share)	$ 28.42
Number of shares (in shares)	143,358
Weighted average outstanding contractual term (in years)	7 years 1 month 6 days
Exercisable (in shares)	95,572
Weighted average exercisable contractual term (in years)	7 years 1 month 6 days
Expected annual dividend	4.40%
$ 30.74
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Exercise price (in dollars per share)	$ 30.74
Number of shares (in shares)	12,719
Weighted average outstanding contractual term (in years)	7 years 7 months 6 days
Exercisable (in shares)	8,479
Weighted average exercisable contractual term (in years)	7 years 7 months 6 days
Expected annual dividend	4.40%
$ 36.99
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Exercise price (in dollars per share)	$ 36.99
Number of shares (in shares)	192,060
Weighted average outstanding contractual term (in years)	8 years 1 month 6 days
Exercisable (in shares)	64,022
Weighted average exercisable contractual term (in years)	8 years 1 month 6 days
Expected annual dividend	4.10%
Minimum | $28.42
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Risk-free rate			1.60%
Expected term (in years)			5 years 6 months
Expected volatility			32.50%
Minimum | $30.74
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Risk-free rate			1.60%
Expected term (in years)			5 years 6 months
Expected volatility			32.50%
Minimum | $28.42
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Risk-free rate		1.60%
Expected term (in years)		5 years 6 months
Expected volatility		32.50%
Minimum | $30.74
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Risk-free rate		1.60%
Expected term (in years)		5 years 6 months
Expected volatility		32.50%
Minimum | $36.99
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Risk-free rate		1.47%
Expected term (in years)		5 years 6 months
Expected volatility		27.50%
Minimum | $28.42
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Risk-free rate	1.60%
Expected term (in years)	5 years 6 months
Expected volatility	32.50%
Minimum | $30.74
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Risk-free rate	1.60%
Expected term (in years)	5 years 6 months
Expected volatility	32.50%
Minimum | $36.99
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Risk-free rate	1.47%
Expected term (in years)	5 years 6 months
Expected volatility	27.50%
Maximum | $28.42
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Risk-free rate			1.75%
Expected term (in years)			6 years 6 months
Expected volatility			37.50%
Maximum | $30.74
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Risk-free rate			1.75%
Expected term (in years)			6 years 6 months
Expected volatility			37.50%
Maximum | $28.42
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Risk-free rate		1.75%
Expected term (in years)		6 years 6 months
Expected volatility		37.50%
Maximum | $30.74
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Risk-free rate		1.75%
Expected term (in years)		6 years 6 months
Expected volatility		37.50%
Maximum | $36.99
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Risk-free rate		1.64%
Expected term (in years)		6 years 6 months
Expected volatility		35.00%
Maximum | $28.42
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Risk-free rate	1.75%
Expected term (in years)	6 years 6 months
Expected volatility	37.50%
Maximum | $30.74
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Risk-free rate	1.75%
Expected term (in years)	6 years 6 months
Expected volatility	37.50%
Maximum | $36.99
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Risk-free rate	1.64%
Expected term (in years)	6 years 6 months
Expected volatility	35.00%

Related Party Transactions - Sc

Related Party Transactions - Schedule of Related Party Revenue and Expenses (Details) $ in Millions	12 Months Ended
	Dec. 31, 2015USD ($)
Revenue:
Total revenue	$ 22.3
Operating costs and expenses:
Total operating costs and expenses	1.9
Data center colocation agreement provided to CBT and CBTS
Revenue:
Total revenue	7.8
229 West 7th Street lease provided to CBT
Revenue:
Total revenue	1.9
Goldcoast Drive/Parkway (Mason) lease
Revenue:
Total revenue	0.3
Transition services provided to CBTS (network interfaces)
Revenue:
Total revenue	0.3
Data center leases provided to CBTS
Revenue:
Total revenue	12
Transition services agreement by CBTS
Operating costs and expenses:
Total operating costs and expenses	0.7
Charges for services provided by CBT (connectivity)
Operating costs and expenses:
Total operating costs and expenses	1
209 West 7th Street rent provided by CBT
Operating costs and expenses:
Total operating costs and expenses	$ 0.2

Related Party Transactions - Na

Related Party Transactions - Narrative (Details) - Cincinnati Bell Inc. - shares	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Related Party Transaction [Line Items]
Ownership %	5.00%	5.00%	9.50%
Operating partnership units owned (in shares)			0

Income Taxes - Narrative (Detai

Income Taxes - Narrative (Details)	12 Months Ended
	Dec. 31, 2017USD ($)Subsidiary	Dec. 31, 2016USD ($)	Dec. 31, 2015USD ($)
Income Taxes [Line Items]
Number of subsidiaries as taxable REIT | Subsidiary	2
Income tax expense	$ 3,000,000	$ 1,800,000	$ 1,800,000
Net deferred tax assets	$ 0	$ 0
Minimum
Income Taxes [Line Items]
Percentage of distributed taxable income to qualify as a REIT	90.00%
Maximum
Income Taxes [Line Items]
Percentage of distributed taxable income to qualify as a REIT	100.00%

Income Taxes - Dividends Paid (

Income Taxes - Dividends Paid (Details) - $ / shares	Oct. 13, 2017	Jul. 14, 2017	Apr. 14, 2017	Jan. 13, 2017	Oct. 14, 2016	Jul. 15, 2016	Apr. 15, 2016	Dec. 31, 2017	Dec. 31, 2016
Income Tax Disclosure [Abstract]
Ordinary income (in dollars per share)								$ 0	$ 0.2
Return of capital (in dollars per share)								1.64	1.26
Total dividend (in dollars per share)	$ 0.42	$ 0.42	$ 0.42	$ 0.38	$ 0.38	$ 0.38	$ 0.38	$ 1.64	$ 1.46

Commitments and Contingencies -

Commitments and Contingencies - Narrative (Details) - USD ($)	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Commitments and Contingencies Disclosure [Abstract]
Rent expense	$ 8,200,000	$ 7,500,000	$ 7,400,000
Letters of credit outstanding	8,500,000
Performance Guarantee
Loss Contingencies [Line Items]
Loss contingency accrual	0	$ 0
Services
Purchase Commitment, Excluding Long-term Commitment [Line Items]
Amount of minimum purchase commitment	$ 69,800,000
Services | Minimum
Purchase Commitment, Excluding Long-term Commitment [Line Items]
Term of purchase commitment	1 year
Services | Maximum
Purchase Commitment, Excluding Long-term Commitment [Line Items]
Term of purchase commitment	2 years

Commitments and Contingencies90

Commitments and Contingencies - Operating Leases (Details) $ in Millions	Dec. 31, 2017USD ($)
Commitments and Contingencies Disclosure [Abstract]
2,018	$ 4.8
2,019	2.3
2,020	1.7
2,021	0.6
2,022	0.5
Thereafter	4.2
Total	$ 14.1

Guarantors - Narrative (Details

Guarantors - Narrative (Details) - USD ($)	12 Months Ended
	Dec. 31, 2017	Nov. 03, 2017	Mar. 30, 2017	Mar. 17, 2017	Dec. 31, 2016	Jul. 01, 2015	Nov. 20, 2012
Condensed Financial Statements, Captions [Line Items]
Long-term debt, net	$ 2,089,400,000				$ 1,240,100,000
Non- Guarantors
Condensed Financial Statements, Captions [Line Items]
Long-term debt, net	$ 0				0
Parent company's ownership percentage	100.00%
CyrusOne GP
Condensed Financial Statements, Captions [Line Items]
Combined interest held on completion of transactions	1.00%
Ownership percentage of senior notes	100.00%
Senior Notes | 5.000% senior notes due 2024
Condensed Financial Statements, Captions [Line Items]
Long-term debt, net	$ 706,800,000				0
Senior Notes | 5.000% senior notes due 2024 | CyrusOne LP and CyrusOne Finance Corp
Condensed Financial Statements, Captions [Line Items]
Face amount of debt	706,800,000	$ 200,000,000		$ 500,000,000
Stated interest rate		5.00%		5.00%
Senior Notes | 5.375% senior notes due 2027
Condensed Financial Statements, Captions [Line Items]
Long-term debt, net	510,500,000				0
Senior Notes | 5.375% senior notes due 2027 | CyrusOne LP and CyrusOne Finance Corp
Condensed Financial Statements, Captions [Line Items]
Face amount of debt	510,500,000	$ 200,000,000		$ 300,000,000
Stated interest rate		5.375%		5.375%
Senior Notes | 6.375% senior notes due 2022
Condensed Financial Statements, Captions [Line Items]
Long-term debt, net	$ 0		$ 474,800,000		$ 477,300,000
Senior Notes | 6.375% senior notes due 2022 | CyrusOne LP and CyrusOne Finance Corp
Condensed Financial Statements, Captions [Line Items]
Long-term debt, net							$ 525,000,000
Stated interest rate						6.375%	6.375%
Warhol Entities | Warhol TRS
Condensed Financial Statements, Captions [Line Items]
Ownership percentage of LLCs	0.20%
Warhol Entities | Warhol Partnership
Condensed Financial Statements, Captions [Line Items]
Ownership percentage of LLCs	100.00%
Warhol Entities | Warhol REIT
Condensed Financial Statements, Captions [Line Items]
Ownership percentage of LLCs	100.00%

Guarantors - Consolidating Bala

Guarantors - Consolidating Balance Sheet (Details) - USD ($) $ in Millions	Dec. 31, 2017	Dec. 31, 2016
Condensed Consolidating Balance Sheets
Land	$ 177.1	$ 142.7
Buildings and improvements	1,371.4	1,008.9
Equipment	1,813.9	1,042.9
Construction in progress	478.4	407.1
Subtotal	3,840.8	2,601.6
Accumulated depreciation	(782.4)	(578.5)
Net investment in real estate	3,058.4	2,023.1
Cash and cash equivalents	151.9	14.6
Investment in subsidiaries	0	0
Rent and other receivables, net	90.5	83.3
Intercompany receivable	0	0
Goodwill	455.1	455.1
Intangible assets, net	203	150.2
Other assets	353.2	126.1
Total assets	4,312.1	2,852.4
Accounts payable and accrued expenses	255.2	227.1
Deferred revenue	111.6	76.7
Intercompany payable	0	0
Capital lease obligations	10.1	10.8
Long-term debt, net	2,089.4	1,240.1
Lease financing arrangements	131.9	135.7
Total liabilities	2,598.2	1,690.4
Total stockholders’ equity	1,713.9	1,162
Total liabilities and equity	4,312.1	2,852.4
Eliminations/Consolidations
Condensed Consolidating Balance Sheets
Land	0	0
Buildings and improvements	2.2	1.2
Equipment	8.9	5.1
Construction in progress	6.6	0.7
Subtotal	17.7	7
Accumulated depreciation	0	0
Net investment in real estate	17.7	7
Cash and cash equivalents	0	0
Investment in subsidiaries	(3,925.4)	(2,560.1)
Rent and other receivables, net	0	0
Intercompany receivable	(1,676.4)	(1,076.8)
Goodwill	0	0
Intangible assets, net	0	0
Other assets	0	0
Total assets	(5,584.1)	(3,629.9)
Accounts payable and accrued expenses	0	0
Deferred revenue	0	0
Intercompany payable	(1,676.4)	(1,076.8)
Capital lease obligations	0	0
Long-term debt, net	0	0
Lease financing arrangements	0	0
Total liabilities	(1,676.4)	(1,076.8)
Total stockholders’ equity	(3,907.7)	(2,553.1)
Total liabilities and equity	(5,584.1)	(3,629.9)
Parent Guarantor
Condensed Consolidating Balance Sheets
Land	0	0
Buildings and improvements	0	0
Equipment	0	0
Construction in progress	0	0
Subtotal	0	0
Accumulated depreciation	0	0
Net investment in real estate	0	0
Cash and cash equivalents	0	0
Investment in subsidiaries	1,718	1,170.3
Rent and other receivables, net	0	0
Intercompany receivable	20	18.6
Goodwill	0	0
Intangible assets, net	0	0
Other assets	0	0
Total assets	1,738	1,188.9
Accounts payable and accrued expenses	41.8	33.9
Deferred revenue	0	0
Intercompany payable	0	0
Capital lease obligations	0	0
Long-term debt, net	0	0
Lease financing arrangements	0	0
Total liabilities	41.8	33.9
Total stockholders’ equity	1,696.2	1,155
Total liabilities and equity	1,738	1,188.9
LP Co-issuer
Condensed Consolidating Balance Sheets
Land	0	0
Buildings and improvements	0	0
Equipment	0	0
Construction in progress	0	0
Subtotal	0	0
Accumulated depreciation	0	0
Net investment in real estate	0	0
Cash and cash equivalents	0	0
Investment in subsidiaries	2,190.2	1,376.1
Rent and other receivables, net	0	0
Intercompany receivable	1,656.4	1,057.7
Goodwill	0	0
Intangible assets, net	0	0
Other assets	0.5	0
Total assets	3,847.1	2,433.8
Accounts payable and accrued expenses	19.7	4.8
Deferred revenue	0	0
Intercompany payable	20	18.6
Capital lease obligations	0	0
Long-term debt, net	2,089.4	1,240.1
Lease financing arrangements	0	0
Total liabilities	2,129.1	1,263.5
Total stockholders’ equity	1,718	1,170.3
Total liabilities and equity	3,847.1	2,433.8
Finance Co-issuer
Condensed Consolidating Balance Sheets
Land	0	0
Buildings and improvements	0	0
Equipment	0	0
Construction in progress	0	0
Subtotal	0	0
Accumulated depreciation	0	0
Net investment in real estate	0	0
Cash and cash equivalents	0	0
Investment in subsidiaries	0	0
Rent and other receivables, net	0	0
Intercompany receivable	0	0
Goodwill	0	0
Intangible assets, net	0	0
Other assets	0	0
Total assets	0	0
Accounts payable and accrued expenses	0	0
Deferred revenue	0	0
Intercompany payable	0	0
Capital lease obligations	0	0
Long-term debt, net	0	0
Lease financing arrangements	0	0
Total liabilities	0	0
Total stockholders’ equity	0	0
Total liabilities and equity	0	0
Guarantor Subsidiaries
Condensed Consolidating Balance Sheets
Land	177.1	142.7
Buildings and improvements	1,340.8	973.6
Equipment	1,803.9	1,036.8
Construction in progress	471.7	406.4
Subtotal	3,793.5	2,559.5
Accumulated depreciation	(778.6)	(571.3)
Net investment in real estate	3,014.9	1,988.2
Cash and cash equivalents	151.2	13.4
Investment in subsidiaries	0	2
Rent and other receivables, net	87.9	81.8
Intercompany receivable	0	0
Goodwill	455.1	455.1
Intangible assets, net	203	150.2
Other assets	174.4	123.4
Total assets	4,086.5	2,814.1
Accounts payable and accrued expenses	192.8	187.7
Deferred revenue	110.8	76
Intercompany payable	1,656.4	1,058.2
Capital lease obligations	5.4	5.6
Long-term debt, net	0	0
Lease financing arrangements	104.6	110.5
Total liabilities	2,070	1,438
Total stockholders’ equity	2,016.5	1,376.1
Total liabilities and equity	4,086.5	2,814.1
Non- Guarantors
Condensed Consolidating Balance Sheets
Land	0	0
Buildings and improvements	28.4	34.1
Equipment	1.1	1
Construction in progress	0.1	0
Subtotal	29.6	35.1
Accumulated depreciation	(3.8)	(7.2)
Net investment in real estate	25.8	27.9
Cash and cash equivalents	0.7	1.2
Investment in subsidiaries	0	0
Rent and other receivables, net	2.6	1.5
Intercompany receivable	0	0.5
Goodwill	0	0
Intangible assets, net	0	0
Other assets	178.3	2.7
Total assets	207.4	33.8
Accounts payable and accrued expenses	0.9	0.7
Deferred revenue	0.8	0.7
Intercompany payable	0	0
Capital lease obligations	4.7	5.2
Long-term debt, net	0	0
Lease financing arrangements	27.3	25.2
Total liabilities	33.7	31.8
Total stockholders’ equity	173.7	2
Total liabilities and equity	207.4	33.8
General Partner
Condensed Consolidating Balance Sheets
Land	0	0
Buildings and improvements	0	0
Equipment	0	0
Construction in progress	0	0
Subtotal	0	0
Accumulated depreciation	0	0
Net investment in real estate	0	0
Cash and cash equivalents	0	0
Investment in subsidiaries	17.2	11.7
Rent and other receivables, net	0	0
Intercompany receivable	0	0
Goodwill	0	0
Intangible assets, net	0	0
Other assets	0	0
Total assets	17.2	11.7
Accounts payable and accrued expenses	0	0
Deferred revenue	0	0
Intercompany payable	0	0
Capital lease obligations	0	0
Long-term debt, net	0	0
Lease financing arrangements	0	0
Total liabilities	0	0
Total stockholders’ equity	17.2	11.7
Total liabilities and equity	$ 17.2	$ 11.7

Guarantors - Consolidating Stat

Guarantors - Consolidating Statements of Operations and Comprehensive Income (Loss) (Details) - USD ($) $ in Millions	3 Months Ended								12 Months Ended
	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Revenue:
Base revenue and other									$ 602.4	$ 476.7	$ 354.6
Metered power reimbursements									69.6	52.4	44.7
Revenue									672	529.1	399.3
Costs and expenses:
Property operating expenses									235.1	187.5	148.7
Sales and marketing									17	16.9	12.1
General and administrative									67	60.7	46.6
Depreciation and amortization									258.9	183.9	141.5
Transaction and acquisition integration costs									10.4	4.3	14.1
Asset impairments and loss on disposal									59.5	5.3	13.5
Costs and expenses									647.9	458.6	376.5
Operating income	$ 23.9	$ (36.3)	$ 16.7	$ 19.8	$ 12.7	$ 18.8	$ 21.1	$ 17.9	24.1	70.5	22.8
Interest expense									68.1	48.8	41.2
Loss on extinguishment of debt									36.5	0	0
Net (loss) income before income taxes									(80.5)	21.7	(18.4)
Income tax expense									(3)	(1.8)	(1.8)
Equity (loss) earnings related to investment in subsidiaries									0	0	0
Net (loss) income	2.8	(55.1)	(0.8)	(30.4)	0.8	4.4	9.1	5.6	(83.5)	19.9	(20.2)
Noncontrolling interest in net loss									0	0	4.8
Net (loss) income attributed to common stockholders	$ 2.8	$ (55.1)	$ (0.8)	$ (30.4)	$ 0.8	$ 4.4	$ 9.1	$ 5.6	(83.5)	19.9	(15.4)
Other comprehensive loss									75.5	(0.9)	(0.2)
Comprehensive (loss) income attributable to CyrusOne Inc.									(8)	19	(15.6)
Eliminations/Consolidations
Revenue:
Base revenue and other									0	0	0
Metered power reimbursements									0	0	0
Revenue									0	0	0
Costs and expenses:
Property operating expenses									0	0	0
Sales and marketing									0	0	0
General and administrative									0	0	0
Depreciation and amortization									0	0	0
Transaction and acquisition integration costs									0	0	0
Asset impairments and loss on disposal									0	0	0
Costs and expenses									0	0	0
Operating income									0	0	0
Interest expense									(10.7)	(3.1)	(1.7)
Loss on extinguishment of debt									0
Net (loss) income before income taxes									10.7	3.1	1.7
Income tax expense									0	0	0
Equity (loss) earnings related to investment in subsidiaries									(70.5)	(81.7)	2.8
Net (loss) income											4.5
Noncontrolling interest in net loss											4.8
Net (loss) income attributed to common stockholders									(59.8)	(78.6)	9.3
Other comprehensive loss									0	0	0
Comprehensive (loss) income attributable to CyrusOne Inc.									(59.8)	(78.6)	9.3
Parent Guarantor
Revenue:
Base revenue and other									0	0	0
Metered power reimbursements									0	0	0
Revenue									0	0	0
Costs and expenses:
Property operating expenses									0	0	0
Sales and marketing									0	0	0
General and administrative									0	0	0
Depreciation and amortization									0	0	0
Transaction and acquisition integration costs									0	0	0
Asset impairments and loss on disposal									0	0	0
Costs and expenses									0	0	0
Operating income									0	0	0
Interest expense									0	0	0
Loss on extinguishment of debt									0
Net (loss) income before income taxes									0	0	0
Income tax expense									0	0	0
Equity (loss) earnings related to investment in subsidiaries									(18.7)	15.9	(17.1)
Net (loss) income											(17.1)
Noncontrolling interest in net loss											0
Net (loss) income attributed to common stockholders									(18.7)	15.9	(17.1)
Other comprehensive loss									0	0	0
Comprehensive (loss) income attributable to CyrusOne Inc.									(18.7)	15.9	(17.1)
LP Co-issuer
Revenue:
Base revenue and other									0	0	0
Metered power reimbursements									0	0	0
Revenue									0	0	0
Costs and expenses:
Property operating expenses									0	0	0
Sales and marketing									0	0	0
General and administrative									0	0	0
Depreciation and amortization									0	0	0
Transaction and acquisition integration costs									0	0	0
Asset impairments and loss on disposal									0	0	0
Costs and expenses									0	0	0
Operating income									0	0	0
Interest expense									76.2	49.1	39.7
Loss on extinguishment of debt									36.5
Net (loss) income before income taxes									(112.7)	(49.1)	(39.7)
Income tax expense									0	0	0
Equity (loss) earnings related to investment in subsidiaries									94	65	17.8
Net (loss) income											(21.9)
Noncontrolling interest in net loss											0
Net (loss) income attributed to common stockholders									(18.7)	15.9	(21.9)
Other comprehensive loss									0	0	0
Comprehensive (loss) income attributable to CyrusOne Inc.									(18.7)	15.9	(21.9)
Finance Co-issuer
Revenue:
Base revenue and other									0	0	0
Metered power reimbursements									0	0	0
Revenue									0	0	0
Costs and expenses:
Property operating expenses									0	0	0
Sales and marketing									0	0	0
General and administrative									0	0	0
Depreciation and amortization									0	0	0
Transaction and acquisition integration costs									0	0	0
Asset impairments and loss on disposal									0	0	0
Costs and expenses									0	0	0
Operating income									0	0	0
Interest expense									0	0	0
Loss on extinguishment of debt									0
Net (loss) income before income taxes									0	0	0
Income tax expense									0	0	0
Equity (loss) earnings related to investment in subsidiaries									0	0	0
Net (loss) income											0
Noncontrolling interest in net loss											0
Net (loss) income attributed to common stockholders									0	0	0
Other comprehensive loss									0	0	0
Comprehensive (loss) income attributable to CyrusOne Inc.									0	0	0
Guarantor Subsidiaries
Revenue:
Base revenue and other									598.2	472.6	350.3
Metered power reimbursements									68.2	51.1	43.5
Revenue									666.4	523.7	393.8
Costs and expenses:
Property operating expenses									232.5	185.2	146
Sales and marketing									17	16.9	12
General and administrative									66.8	60.5	46.6
Depreciation and amortization									257.8	185.3	138.7
Transaction and acquisition integration costs									10.4	4.3	14.1
Asset impairments and loss on disposal									55.9	5.3	13.5
Costs and expenses									640.4	457.5	370.9
Operating income									26	66.2	22.9
Interest expense									0	0	0
Loss on extinguishment of debt									0
Net (loss) income before income taxes									26	66.2	22.9
Income tax expense									(3)	(1.8)	(1.8)
Equity (loss) earnings related to investment in subsidiaries									(4.6)	0.6	(3.3)
Net (loss) income											17.8
Noncontrolling interest in net loss											0
Net (loss) income attributed to common stockholders									18.4	65	17.8
Other comprehensive loss									0	0	0
Comprehensive (loss) income attributable to CyrusOne Inc.									18.4	65	17.8
Non- Guarantors
Revenue:
Base revenue and other									4.2	4.1	4.3
Metered power reimbursements									1.4	1.3	1.2
Revenue									5.6	5.4	5.5
Costs and expenses:
Property operating expenses									2.6	2.3	2.7
Sales and marketing									0	0	0.1
General and administrative									0.2	0.2	0
Depreciation and amortization									1.1	(1.4)	2.8
Transaction and acquisition integration costs									0	0	0
Asset impairments and loss on disposal									3.6	0	0
Costs and expenses									7.5	1.1	5.6
Operating income									(1.9)	4.3	(0.1)
Interest expense									2.6	2.8	3.2
Loss on extinguishment of debt									0
Net (loss) income before income taxes									(4.5)	1.5	(3.3)
Income tax expense									0	0	0
Equity (loss) earnings related to investment in subsidiaries									0	0	0
Net (loss) income											(3.3)
Noncontrolling interest in net loss											0
Net (loss) income attributed to common stockholders									(4.5)	1.5	(3.3)
Other comprehensive loss									75.5	(0.9)	(0.2)
Comprehensive (loss) income attributable to CyrusOne Inc.									71	0.6	(3.5)
General Partner
Revenue:
Base revenue and other									0	0	0
Metered power reimbursements									0	0	0
Revenue									0	0	0
Costs and expenses:
Property operating expenses									0	0	0
Sales and marketing									0	0	0
General and administrative									0	0	0
Depreciation and amortization									0	0	0
Transaction and acquisition integration costs									0	0	0
Asset impairments and loss on disposal									0	0	0
Costs and expenses									0	0	0
Operating income									0	0	0
Interest expense									0	0	0
Loss on extinguishment of debt									0
Net (loss) income before income taxes									0	0	0
Income tax expense									0	0	0
Equity (loss) earnings related to investment in subsidiaries									(0.2)	0.2	(0.2)
Net (loss) income											(0.2)
Noncontrolling interest in net loss											0
Net (loss) income attributed to common stockholders									(0.2)	0.2	(0.2)
Other comprehensive loss									0	0	0
Comprehensive (loss) income attributable to CyrusOne Inc.									$ (0.2)	$ 0.2	$ (0.2)

Guarantors - Consolidating St94

Guarantors - Consolidating Statements of Cash Flows (Details) - USD ($) $ in Millions	1 Months Ended	12 Months Ended
	Jul. 31, 2016	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Condensed Consolidating Statements of Cash Flows
Net cash (used in) provided by operating activities		$ 289.5	$ 180.6	$ 140.2
Cash flows from investing activities:
Capital expenditures – asset acquisitions, net of cash acquired		(492.3)	(131.1)	(17.3)
Capital expenditures – other development		(914.5)	(600)	(217.2)
Equity investment		(100)	0	0
Business acquisition, net of cash acquired		0	0	(389.6)
Investment in subsidiaries		0	0	0
Return of investment		0	0	0
Intercompany borrowings		0	0	0
Net cash used in investing activities		(1,506.8)	(731.1)	(624.1)
Cash flows from financing activities:
Issuance of common stock		706	448.7	799.5
Stock issuance costs		(0.3)	(1.6)	(0.8)
Acquisition of operating partnership units		0	0	(596.4)
Dividends paid		(145.7)	(114.3)	(80.8)
Intercompany borrowings		0	0	0
Borrowings from credit facility		1,390	710	260
Proceeds from issuance of debt		1,217.8	0	103.8
Payments on credit facility		(1,275)	(460)	(10)
Payments on senior notes		(474.8)	0	0
Payments on capital leases and lease financing arrangements		(9.8)	(9.1)	(5.9)
Payment of debt extinguishment costs		(30.4)	0	0
Tax payment upon exercise of equity awards		(6.9)	(14.2)	(0.8)
Contributions/distributions from parent		0	0	0
Payment of note payable	$ (1.5)	0	(1.5)	0
Debt issuance costs		(19)	(8.7)	(5.4)
Interest paid by lenders on issuance of the senior notes		2.7	0	0
Net cash provided by financing activities		1,354.6	549.3	463.2
Net increase (decrease) in cash, cash equivalents and restricted cash		137.3	(1.2)	(20.7)
Cash, cash equivalents and restricted cash at beginning of period		14.6	15.8	36.5	$ 36.5
Cash, cash equivalents and restricted cash at end of period		151.9	14.6	15.8	36.5
General Partner
Condensed Consolidating Statements of Cash Flows
Net cash (used in) provided by operating activities		0	0	0
Cash flows from investing activities:
Capital expenditures – asset acquisitions, net of cash acquired		0	0	0
Capital expenditures – other development		0	0	0
Equity investment		0
Business acquisition, net of cash acquired				0
Investment in subsidiaries		(7.1)	(4.5)	(2)
Return of investment		0	0	0
Intercompany borrowings		0	0	0
Net cash used in investing activities		(7.1)	(4.5)	(2)
Cash flows from financing activities:
Issuance of common stock		0	0	0
Stock issuance costs		0	0	0
Acquisition of operating partnership units				0
Dividends paid		0	0	0
Intercompany borrowings		0	0	0
Borrowings from credit facility		0	0	0
Proceeds from issuance of debt		0		0
Payments on credit facility		0	0	0
Payments on senior notes		0
Payments on capital leases and lease financing arrangements		0	0	0
Payment of debt extinguishment costs		0
Tax payment upon exercise of equity awards		0	0	0
Contributions/distributions from parent		7.1	4.5	2
Payment of note payable			0
Debt issuance costs		0	0	0
Interest paid by lenders on issuance of the senior notes		0
Net cash provided by financing activities		7.1	4.5	2
Net increase (decrease) in cash, cash equivalents and restricted cash		0	0	0
Cash, cash equivalents and restricted cash at beginning of period		0	0		0
Cash, cash equivalents and restricted cash at end of period		0	0	0
Parent Guarantor
Condensed Consolidating Statements of Cash Flows
Net cash (used in) provided by operating activities		0	0	0
Cash flows from investing activities:
Capital expenditures – asset acquisitions, net of cash acquired		0	0	0
Capital expenditures – other development		0	0	0
Equity investment		0
Business acquisition, net of cash acquired				0
Investment in subsidiaries		(705.3)	(448.2)	(203.1)
Return of investment		145.7	112.3	62.6
Intercompany borrowings		6.5	15.3	0
Net cash used in investing activities		(553.1)	(320.6)	(140.5)
Cash flows from financing activities:
Issuance of common stock		706	448.7	799.5
Stock issuance costs		(0.3)	(1.6)	(0.8)
Acquisition of operating partnership units				(596.4)
Dividends paid		(145.7)	(112.3)	(61)
Intercompany borrowings		0	0	0
Borrowings from credit facility		0	0	0
Proceeds from issuance of debt		0		0
Payments on credit facility		0	0	0
Payments on senior notes		0
Payments on capital leases and lease financing arrangements		0	0	0
Payment of debt extinguishment costs		0
Tax payment upon exercise of equity awards		(6.9)	(14.2)	(0.8)
Contributions/distributions from parent		0	0	0
Payment of note payable			0
Debt issuance costs		0	0	0
Interest paid by lenders on issuance of the senior notes		0
Net cash provided by financing activities		553.1	320.6	140.5
Net increase (decrease) in cash, cash equivalents and restricted cash		0	0	0
Cash, cash equivalents and restricted cash at beginning of period		0	0		0
Cash, cash equivalents and restricted cash at end of period		0	0	0
LP Co-issuer
Condensed Consolidating Statements of Cash Flows
Net cash (used in) provided by operating activities		(60.3)	(45.4)	(19.6)
Cash flows from investing activities:
Capital expenditures – asset acquisitions, net of cash acquired		0	0	0
Capital expenditures – other development		0	0	0
Equity investment		0
Business acquisition, net of cash acquired				0
Investment in subsidiaries		(705.3)	(448.2)	(203.1)
Return of investment		0	0	102
Intercompany borrowings		(598.8)	(66.3)	(348.4)
Net cash used in investing activities		(1,304.1)	(514.5)	(449.5)
Cash flows from financing activities:
Issuance of common stock		0	0	0
Stock issuance costs		0	0	0
Acquisition of operating partnership units				0
Dividends paid		(145.7)	(114.3)	(80.8)
Intercompany borrowings		(6.5)	(15.3)	0
Borrowings from credit facility		1,390	710	260
Proceeds from issuance of debt		1,217.8		103.8
Payments on credit facility		(1,275)	(460)	(10)
Payments on senior notes		(474.8)
Payments on capital leases and lease financing arrangements		0	0	0
Payment of debt extinguishment costs		(30.4)
Tax payment upon exercise of equity awards		0	0	0
Contributions/distributions from parent		705.3	448.2	201.5
Payment of note payable			0
Debt issuance costs		(19)	(8.7)	(5.4)
Interest paid by lenders on issuance of the senior notes		2.7
Net cash provided by financing activities		1,364.4	559.9	469.1
Net increase (decrease) in cash, cash equivalents and restricted cash		0	0	0
Cash, cash equivalents and restricted cash at beginning of period		0	0		0
Cash, cash equivalents and restricted cash at end of period		0	0	0
Finance Co-issuer
Condensed Consolidating Statements of Cash Flows
Net cash (used in) provided by operating activities		0	0	0
Cash flows from investing activities:
Capital expenditures – asset acquisitions, net of cash acquired		0	0	0
Capital expenditures – other development		0	0	0
Equity investment		0
Business acquisition, net of cash acquired				0
Investment in subsidiaries		0	0	0
Return of investment		0	0	0
Intercompany borrowings		0	0	0
Net cash used in investing activities		0	0	0
Cash flows from financing activities:
Issuance of common stock		0	0	0
Stock issuance costs		0	0	0
Acquisition of operating partnership units				0
Dividends paid		0	0	0
Intercompany borrowings		0	0	0
Borrowings from credit facility		0	0	0
Proceeds from issuance of debt		0		0
Payments on credit facility		0	0	0
Payments on senior notes		0
Payments on capital leases and lease financing arrangements		0	0	0
Payment of debt extinguishment costs		0
Tax payment upon exercise of equity awards		0	0	0
Contributions/distributions from parent		0	0	0
Payment of note payable			0
Debt issuance costs		0	0	0
Interest paid by lenders on issuance of the senior notes		0
Net cash provided by financing activities		0	0	0
Net increase (decrease) in cash, cash equivalents and restricted cash		0	0	0
Cash, cash equivalents and restricted cash at beginning of period		0	0		0
Cash, cash equivalents and restricted cash at end of period		0	0	0
Guarantor Subsidiaries
Condensed Consolidating Statements of Cash Flows
Net cash (used in) provided by operating activities		339.7	221.8	156.2
Cash flows from investing activities:
Capital expenditures – asset acquisitions, net of cash acquired		(492.3)	(131.1)	(17.3)
Capital expenditures – other development		(903.8)	(598.9)	(216.7)
Equity investment		0
Business acquisition, net of cash acquired				(389.6)
Investment in subsidiaries		(0.7)	0	(0.4)
Return of investment		0	0	(17.9)
Intercompany borrowings		0	0	0
Net cash used in investing activities		(1,396.8)	(730)	(641.9)
Cash flows from financing activities:
Issuance of common stock		0	0	0
Stock issuance costs		0	0	0
Acquisition of operating partnership units				0
Dividends paid		0	0	(80.8)
Intercompany borrowings		598.2	71	348.4
Borrowings from credit facility		0	0	0
Proceeds from issuance of debt		0		0
Payments on credit facility		0	0	0
Payments on senior notes		0
Payments on capital leases and lease financing arrangements		(8.6)	(8)	(5)
Payment of debt extinguishment costs		0
Tax payment upon exercise of equity awards		0	0	0
Contributions/distributions from parent		605.3	448.2	201.5
Payment of note payable			(1.5)
Debt issuance costs		0	0	0
Interest paid by lenders on issuance of the senior notes		0
Net cash provided by financing activities		1,194.9	509.7	464.1
Net increase (decrease) in cash, cash equivalents and restricted cash		137.8	1.5	(21.6)
Cash, cash equivalents and restricted cash at beginning of period		13.4	11.9		33.5
Cash, cash equivalents and restricted cash at end of period		151.2	13.4	11.9
Non- Guarantors
Condensed Consolidating Statements of Cash Flows
Net cash (used in) provided by operating activities		(0.6)	0	1.9
Cash flows from investing activities:
Capital expenditures – asset acquisitions, net of cash acquired		0	0	0
Capital expenditures – other development		0	(1.1)	(0.5)
Equity investment		(100)
Business acquisition, net of cash acquired				0
Investment in subsidiaries		0	0	0
Return of investment		0	0	0
Intercompany borrowings		0.5	(0.5)	0
Net cash used in investing activities		(99.5)	(1.6)	(0.5)
Cash flows from financing activities:
Issuance of common stock		0	0	0
Stock issuance costs		0	0	0
Acquisition of operating partnership units				0
Dividends paid		0	0	0
Intercompany borrowings		0	0	0
Borrowings from credit facility		0	0	0
Proceeds from issuance of debt		0		0
Payments on credit facility		0	0	0
Payments on senior notes		0
Payments on capital leases and lease financing arrangements		(1.2)	(1.1)	(0.9)
Payment of debt extinguishment costs		0
Tax payment upon exercise of equity awards		0	0	0
Contributions/distributions from parent		100.8	0	0.4
Payment of note payable			0
Debt issuance costs		0	0	0
Interest paid by lenders on issuance of the senior notes		0
Net cash provided by financing activities		99.6	(1.1)	(0.5)
Net increase (decrease) in cash, cash equivalents and restricted cash		(0.5)	(2.7)	0.9
Cash, cash equivalents and restricted cash at beginning of period		1.2	3.9		3
Cash, cash equivalents and restricted cash at end of period		0.7	1.2	3.9
Eliminations/Consolidations
Condensed Consolidating Statements of Cash Flows
Net cash (used in) provided by operating activities		10.7	4.2	1.7
Cash flows from investing activities:
Capital expenditures – asset acquisitions, net of cash acquired		0	0	0
Capital expenditures – other development		(10.7)	0	0
Equity investment		0
Business acquisition, net of cash acquired				0
Investment in subsidiaries		1,418.4	900.9	408.6
Return of investment		(145.7)	(112.3)	(146.7)
Intercompany borrowings		591.8	51.5	348.4
Net cash used in investing activities		1,853.8	840.1	610.3
Cash flows from financing activities:
Issuance of common stock		0	0	0
Stock issuance costs		0	0	0
Acquisition of operating partnership units				0
Dividends paid		145.7	112.3	141.8
Intercompany borrowings		(591.7)	(55.7)	(348.4)
Borrowings from credit facility		0	0	0
Proceeds from issuance of debt		0		0
Payments on credit facility		0	0	0
Payments on senior notes		0
Payments on capital leases and lease financing arrangements		0	0	0
Payment of debt extinguishment costs		0
Tax payment upon exercise of equity awards		0	0	0
Contributions/distributions from parent		(1,418.5)	(900.9)	(405.4)
Payment of note payable			0
Debt issuance costs		0	0	0
Interest paid by lenders on issuance of the senior notes		0
Net cash provided by financing activities		(1,864.5)	(844.3)	(612)
Net increase (decrease) in cash, cash equivalents and restricted cash		0	0	0
Cash, cash equivalents and restricted cash at beginning of period		0	0		$ 0
Cash, cash equivalents and restricted cash at end of period		$ 0	$ 0	$ 0

Quarterly Financial Informati95

Quarterly Financial Information (Unaudited) - Schedule of Quarterly Information (Details) - USD ($) $ / shares in Units, $ in Millions	3 Months Ended								12 Months Ended
	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Quarterly Financial Information Disclosure [Abstract]
Revenue	$ 180.5	$ 175.3	$ 166.9	$ 149.3	$ 137.4	$ 143.8	$ 130.1	$ 117.8	$ 672	$ 529.1
Operating income (loss)	23.9	(36.3)	16.7	19.8	12.7	18.8	21.1	17.9	24.1	70.5	$ 22.8
Net (loss) income	2.8	(55.1)	(0.8)	(30.4)	0.8	4.4	9.1	5.6	(83.5)	19.9	(20.2)
Net (loss) income attributed to common shareholders	$ 2.8	$ (55.1)	$ (0.8)	$ (30.4)	$ 0.8	$ 4.4	$ 9.1	$ 5.6	$ (83.5)	$ 19.9	$ (15.4)
Basic and diluted income (loss) per share (in dollars per share)	$ 0.03	$ (0.61)	$ (0.01)	$ (0.36)	$ 0.01	$ 0.05	$ 0.11	$ 0.07	$ (0.95)	$ 0.24	$ (0.30)

Schedule II. Valuation and Qu96

Schedule II. Valuation and Qualifying Accounts (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Allowance for Doubtful Accounts
Movement in Valuation Allowances and Reserves [Roll Forward]
Beginning of Period	$ 2.1	$ 1	$ 1
Charge to Expenses	0.2	1.6	0
(Deductions)/Additions	(0.2)	(0.5)	0
End of Period	2.1	2.1	1
Deferred Tax Valuation Allowance
Movement in Valuation Allowances and Reserves [Roll Forward]
Beginning of Period	6.5	6.3	5.7
Charge to Expenses	0.7	0.2	0.6
(Deductions)/Additions	0	0	0
End of Period	$ 7.2	$ 6.5	$ 6.3

Schedule III. Real Estate Pro97

Schedule III. Real Estate Properties and Accumulated Depreciation - Schedule of Real Estate Properties (Details) - USD ($) $ in Millions	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Initial Costs
Land	$ 176.1
Building and Improvements	535.2
Equipment	357.6
Cost Capitalized Subsequent to Acquisition
Land	1
Building and Improvements	836.2
Equipment	1,456.3
Gross Carrying Amount
Land	177.1	$ 142.7
Building and Improvements	1,371.4	1,008.9
Equipment	1,813.9	1,042.9
Accumulated Depreciation	782.4	578.5	$ 435.6	$ 327
Aggregate cost of the total properties for federal income tax purposes	4,257.7
Construction in progress	478.4	407.1
Dallas - Carrollton
Initial Costs
Land	16.1
Building and Improvements	0
Equipment	0
Cost Capitalized Subsequent to Acquisition
Land	0
Building and Improvements	61.8
Equipment	210.7
Gross Carrying Amount
Land	16.1	16.1
Building and Improvements	61.8	57.6
Equipment	210.7	154
Accumulated Depreciation	76.7
Houston - Houston West I
Initial Costs
Land	1.4
Building and Improvements	21.4
Equipment	0.1
Cost Capitalized Subsequent to Acquisition
Land	0
Building and Improvements	63.8
Equipment	49.7
Gross Carrying Amount
Land	1.4	1.4
Building and Improvements	85.2	85
Equipment	49.8	48.4
Accumulated Depreciation	73.7
Cincinnati - 7th Street
Initial Costs
Land	0.9
Building and Improvements	42.2
Equipment	0
Cost Capitalized Subsequent to Acquisition
Land	0
Building and Improvements	68.4
Equipment	33.1
Gross Carrying Amount
Land	0.9	0.9
Building and Improvements	110.6	110.6
Equipment	33.1	21
Accumulated Depreciation	86.5
Dallas - Lewisville
Initial Costs
Land	0
Building and Improvements	46.2
Equipment	2.2
Cost Capitalized Subsequent to Acquisition
Land	0
Building and Improvements	30.5
Equipment	35.2
Gross Carrying Amount
Land	0	0
Building and Improvements	76.7	76.7
Equipment	37.4	33.7
Accumulated Depreciation	62
Northern Virginia - Sterling II
Initial Costs
Land	0
Building and Improvements	0
Equipment	0
Cost Capitalized Subsequent to Acquisition
Land	0
Building and Improvements	28.8
Equipment	112.3
Gross Carrying Amount
Land	0	0
Building and Improvements	28.8	28.7
Equipment	112.3	111.8
Accumulated Depreciation	16.4
Somerset I
Initial Costs
Land	12.1
Building and Improvements	124.6
Equipment	83.3
Cost Capitalized Subsequent to Acquisition
Land	0
Building and Improvements	0.2
Equipment	0.4
Gross Carrying Amount
Land	12.1	0
Building and Improvements	124.8	0
Equipment	83.7	0
Accumulated Depreciation	12.2
Chicago - Aurora I
Initial Costs
Land	2.4
Building and Improvements	26
Equipment	97.3
Cost Capitalized Subsequent to Acquisition
Land	0
Building and Improvements	6.4
Equipment	27.7
Gross Carrying Amount
Land	2.4	2.4
Building and Improvements	32.4	28.5
Equipment	125	99.9
Accumulated Depreciation	24
Totowa - Madison
Initial Costs
Land	0
Building and Improvements	28.3
Equipment	45.6
Cost Capitalized Subsequent to Acquisition
Land	0
Building and Improvements	0.2
Equipment	9.5
Gross Carrying Amount
Land	0	0
Building and Improvements	28.5	28.3
Equipment	55.1	50.8
Accumulated Depreciation	20.4
Cincinnati - North Cincinnati
Initial Costs
Land	4
Building and Improvements	12.3
Equipment
Cost Capitalized Subsequent to Acquisition
Land	0
Building and Improvements	65.1
Equipment	9.9
Gross Carrying Amount
Land	4	4
Building and Improvements	77.4	77.3
Equipment	9.9	9
Accumulated Depreciation	37
San Antonio III
Initial Costs
Land	0
Building and Improvements	0
Equipment	0
Cost Capitalized Subsequent to Acquisition
Land	0
Building and Improvements	40.3
Equipment	96.8
Gross Carrying Amount
Land	0	0
Building and Improvements	40.3	0
Equipment	96.8	0
Accumulated Depreciation	9
Houston - Houston West II
Initial Costs
Land	2
Building and Improvements	0
Equipment	0
Cost Capitalized Subsequent to Acquisition
Land	0.8
Building and Improvements	22.8
Equipment	50.1
Gross Carrying Amount
Land	2.8	2.8
Building and Improvements	22.8	23.1
Equipment	50.1	49
Accumulated Depreciation	28
Wappingers Falls I
Initial Costs
Land	0
Building and Improvements	9.9
Equipment	13.3
Cost Capitalized Subsequent to Acquisition
Land	0
Building and Improvements	1.4
Equipment	4.7
Gross Carrying Amount
Land	0	0
Building and Improvements	11.3	11.3
Equipment	18	17.1
Accumulated Depreciation	9.5
San Antonio I
Initial Costs
Land	4.6
Building and Improvements	3
Equipment	0
Cost Capitalized Subsequent to Acquisition
Land	0
Building and Improvements	28.7
Equipment	34.8
Gross Carrying Amount
Land	4.6	4.6
Building and Improvements	31.7	32.1
Equipment	34.8	33.6
Accumulated Depreciation	26.2
Phoenix - Chandler II
Initial Costs
Land	0
Building and Improvements	0
Equipment	0
Cost Capitalized Subsequent to Acquisition
Land	0
Building and Improvements	16.2
Equipment	38.9
Gross Carrying Amount
Land	0	0
Building and Improvements	16.2	16.1
Equipment	38.9	38.8
Accumulated Depreciation	15.6
Northern Virginia - Sterling I
Initial Costs
Land	6.9
Building and Improvements	0
Equipment	0
Cost Capitalized Subsequent to Acquisition
Land	0.1
Building and Improvements	20
Equipment	59.4
Gross Carrying Amount
Land	7	7
Building and Improvements	20	19.7
Equipment	59.4	47.2
Accumulated Depreciation	18.1
Raleigh-Durham I
Initial Costs
Land	2.1
Building and Improvements	73.5
Equipment	71.3
Cost Capitalized Subsequent to Acquisition
Land	0
Building and Improvements	4.5
Equipment	4.7
Gross Carrying Amount
Land	2.1	0
Building and Improvements	78	0
Equipment	76	0
Accumulated Depreciation	9.8
Houston - Galleria
Initial Costs
Land	0
Building and Improvements	56
Equipment	2
Cost Capitalized Subsequent to Acquisition
Land	0
Building and Improvements	12.6
Equipment	15.6
Gross Carrying Amount
Land	0	0
Building and Improvements	68.6	68.6
Equipment	17.6	16.6
Accumulated Depreciation	49.1
Phoenix - Chandler I
Initial Costs
Land	14.8
Building and Improvements	0
Equipment	0
Cost Capitalized Subsequent to Acquisition
Land	0
Building and Improvements	58.2
Equipment	65.9
Gross Carrying Amount
Land	14.8	14.8
Building and Improvements	58.2	56.8
Equipment	65.9	56.5
Accumulated Depreciation	36.5
Phoenix - Chandler III
Initial Costs
Land	0
Building and Improvements	0.9
Equipment	2.5
Cost Capitalized Subsequent to Acquisition
Land	0
Building and Improvements	10.5
Equipment	47.5
Gross Carrying Amount
Land	0	0
Building and Improvements	11.4	9.9
Equipment	50	44.5
Accumulated Depreciation	6.4
Northern Virginia - Sterling III
Initial Costs
Land	0
Building and Improvements	0
Equipment	0
Cost Capitalized Subsequent to Acquisition
Land	0
Building and Improvements	22.2
Equipment	61.3
Gross Carrying Amount
Land	0	0
Building and Improvements	22.2	0
Equipment	61.3	0
Accumulated Depreciation	6.2
Austin II
Initial Costs
Land	2
Building and Improvements	0
Equipment	0
Cost Capitalized Subsequent to Acquisition
Land	0
Building and Improvements	23.4
Equipment	7
Gross Carrying Amount
Land	2	2
Building and Improvements	23.4	23.4
Equipment	7	6.6
Accumulated Depreciation	14.5
San Antonio II
Initial Costs
Land	6.7
Building and Improvements	0
Equipment	0
Cost Capitalized Subsequent to Acquisition
Land	0.3
Building and Improvements	29
Equipment	60.4
Gross Carrying Amount
Land	7	7
Building and Improvements	29	29
Equipment	60.4	59.4
Accumulated Depreciation	10.4
Florence
Initial Costs
Land	2.2
Building and Improvements	7.7
Equipment	0
Cost Capitalized Subsequent to Acquisition
Land	0
Building and Improvements	34.3
Equipment	5.3
Gross Carrying Amount
Land	2.2	2.2
Building and Improvements	42	41.9
Equipment	5.3	4.9
Accumulated Depreciation	28.5
Phoenix - Chandler IV
Initial Costs
Land	0
Building and Improvements	0
Equipment	0
Cost Capitalized Subsequent to Acquisition
Land	0
Building and Improvements	18.3
Equipment	40.9
Gross Carrying Amount
Land	0	0
Building and Improvements	18.3	0
Equipment	40.9	0
Accumulated Depreciation	2.2
Cincinnati - Hamilton
Initial Costs
Land	0
Building and Improvements	9.5
Equipment	0
Cost Capitalized Subsequent to Acquisition
Land	0
Building and Improvements	40.7
Equipment	6
Gross Carrying Amount
Land	0	0
Building and Improvements	50.2	50.2
Equipment	6	5
Accumulated Depreciation	36.2
London - Great Bridgewater
Initial Costs
Land	0
Building and Improvements	16.5
Equipment	0
Cost Capitalized Subsequent to Acquisition
Land	0
Building and Improvements	11.9
Equipment	1.1
Gross Carrying Amount
Land	0	0
Building and Improvements	28.4	25.9
Equipment	1.1	0.9
Accumulated Depreciation	3.8
Northern Virginia - Sterling IV
Initial Costs
Land	4.6
Building and Improvements	9.6
Equipment	0.1
Cost Capitalized Subsequent to Acquisition
Land	0
Building and Improvements	10.4
Equipment	73.6
Gross Carrying Amount
Land	4.6	4.6
Building and Improvements	20	11
Equipment	73.7	33.4
Accumulated Depreciation	5.6
Cincinnati - Mason
Initial Costs
Land	0
Building and Improvements	0
Equipment	0
Cost Capitalized Subsequent to Acquisition
Land	0
Building and Improvements	20.3
Equipment	1.6
Gross Carrying Amount
Land	0	0
Building and Improvements	20.3	20.2
Equipment	1.6	1.4
Accumulated Depreciation	13.8
Dallas - Midway
Initial Costs
Land	0
Building and Improvements	1.8
Equipment	0
Cost Capitalized Subsequent to Acquisition
Land	0
Building and Improvements	0.2
Equipment	0.4
Gross Carrying Amount
Land	0	0
Building and Improvements	2	2
Equipment	0.4	0.4
Accumulated Depreciation	2.3
Phoenix - Chandler VI
Initial Costs
Land	10.5
Building and Improvements	0
Equipment	0
Cost Capitalized Subsequent to Acquisition
Land	0
Building and Improvements	15.7
Equipment	49.2
Gross Carrying Amount
Land	10.5	10.5
Building and Improvements	15.7	0
Equipment	49.2	0
Accumulated Depreciation	1.3
Stamford - Riverbend
Initial Costs
Land	0
Building and Improvements	4.3
Equipment	13.2
Cost Capitalized Subsequent to Acquisition
Land	0
Building and Improvements	(1.4)
Equipment	(6.3)
Gross Carrying Amount
Land	0	0
Building and Improvements	2.9	4.3
Equipment	6.9	14.5
Accumulated Depreciation	3.2
Norwalk I
Initial Costs
Land	0
Building and Improvements	18.3
Equipment	25.3
Cost Capitalized Subsequent to Acquisition
Land	0
Building and Improvements	(4.8)
Equipment	(15.9)
Gross Carrying Amount
Land	0	0
Building and Improvements	13.5	19
Equipment	9.4	26.6
Accumulated Depreciation	2.9
Dallas - Marsh
Initial Costs
Land	0
Building and Improvements	0
Equipment	0
Cost Capitalized Subsequent to Acquisition
Land	0
Building and Improvements	0.1
Equipment	0.6
Gross Carrying Amount
Land	0	0
Building and Improvements	0.1	0.1
Equipment	0.6	0.6
Accumulated Depreciation	0.6
Chicago - Lombard
Initial Costs
Land	0.7
Building and Improvements	3.2
Equipment	0
Cost Capitalized Subsequent to Acquisition
Land	0
Building and Improvements	1.5
Equipment	7.7
Gross Carrying Amount
Land	0.7	0.7
Building and Improvements	4.7	4.7
Equipment	7.7	7.9
Accumulated Depreciation	6
Stamford - Omega
Initial Costs
Land	0
Building and Improvements	3.2
Equipment	0.6
Cost Capitalized Subsequent to Acquisition
Land	0
Building and Improvements	(0.6)
Equipment	0.1
Gross Carrying Amount
Land	0	0
Building and Improvements	2.6	3.2
Equipment	0.7	1.5
Accumulated Depreciation	0.5
Totowa - Commerce
Initial Costs
Land	0
Building and Improvements	4.1
Equipment	0.8
Cost Capitalized Subsequent to Acquisition
Land	0
Building and Improvements	0
Equipment	0.8
Gross Carrying Amount
Land	0	0
Building and Improvements	4.1	4.1
Equipment	1.6	1.4
Accumulated Depreciation	0.9
Cincinnati - Blue Ash
Initial Costs
Land	0
Building and Improvements	2.6
Equipment	0
Cost Capitalized Subsequent to Acquisition
Land	0
Building and Improvements	(1.9)
Equipment	0.2
Gross Carrying Amount
Land	0	0
Building and Improvements	0.7	0.6
Equipment	0.2	0.1
Accumulated Depreciation	0.4
South Bend - Crescent
Initial Costs
Land	0
Building and Improvements	1.1
Equipment	0
Cost Capitalized Subsequent to Acquisition
Land	0
Building and Improvements	0.6
Equipment	0.1
Gross Carrying Amount
Land	0	0
Building and Improvements	1.7	1.7
Equipment	0.1	0.2
Accumulated Depreciation	1.8
Houston - Houston West III
Initial Costs
Land	18.3
Building and Improvements	0
Equipment	0
Cost Capitalized Subsequent to Acquisition
Land	0.1
Building and Improvements	17.9
Equipment	30.7
Gross Carrying Amount
Land	18.4	18.4
Building and Improvements	17.9	9.4
Equipment	30.7	13.5
Accumulated Depreciation	5.9
Singapore - Inter Business Park
Initial Costs
Land	0
Building and Improvements	9
Equipment	0
Cost Capitalized Subsequent to Acquisition
Land	0
Building and Improvements	(9)
Equipment	0
Gross Carrying Amount
Land	0	0
Building and Improvements	0	8.2
Equipment	0	0.1
Accumulated Depreciation	0
South Bend - Monroe
Initial Costs
Land	0
Building and Improvements	0
Equipment	0
Cost Capitalized Subsequent to Acquisition
Land	0
Building and Improvements	2.5
Equipment	0.3
Gross Carrying Amount
Land	0	0
Building and Improvements	2.5	2.5
Equipment	0.3	0.3
Accumulated Depreciation	1.6
Cincinnati - Goldcoast
Initial Costs
Land	0.6
Building and Improvements	0
Equipment	0
Cost Capitalized Subsequent to Acquisition
Land	(0.4)
Building and Improvements	4
Equipment	0.1
Gross Carrying Amount
Land	0.2	0.2
Building and Improvements	4	4
Equipment	0.1	0.1
Accumulated Depreciation	3
Austin III
Initial Costs
Land	3.3
Building and Improvements	0
Equipment	0
Cost Capitalized Subsequent to Acquisition
Land	0
Building and Improvements	10.6
Equipment	33.9
Gross Carrying Amount
Land	3.3	3.3
Building and Improvements	10.6	9.7
Equipment	33.9	31.8
Accumulated Depreciation	6.8
Northern Virginia - Sterling V
Initial Costs
Land	24.1
Building and Improvements	0
Equipment	0
Cost Capitalized Subsequent to Acquisition
Land	0
Building and Improvements	35.7
Equipment	108.8
Gross Carrying Amount
Land	24.1	24.1
Building and Improvements	35.7	0
Equipment	108.8	0
Accumulated Depreciation	4.1
Phoenix - Chandler V
Initial Costs
Land	0
Building and Improvements	0
Equipment	0
Cost Capitalized Subsequent to Acquisition
Land	0
Building and Improvements	5.9
Equipment	20.5
Gross Carrying Amount
Land	0	0
Building and Improvements	5.9	0
Equipment	20.5	0
Accumulated Depreciation	0.3
San Antonio IV
Initial Costs
Land	0
Building and Improvements	0
Equipment	0
Cost Capitalized Subsequent to Acquisition
Land	0
Building and Improvements	0
Equipment	17.9
Gross Carrying Amount
Land	0	0
Building and Improvements	0	0
Equipment	17.9	0
Accumulated Depreciation	0.9
Austin Land A
Initial Costs
Land	7.9
Building and Improvements	0
Equipment	0
Cost Capitalized Subsequent to Acquisition
Land	0.1
Building and Improvements	0
Equipment	0.2
Gross Carrying Amount
Land	8	8
Building and Improvements	0	0
Equipment	0.2	0.2
Accumulated Depreciation	0.1
Chicago - Aurora II
Initial Costs
Land	2.6
Building and Improvements	0
Equipment	0
Cost Capitalized Subsequent to Acquisition
Land	0
Building and Improvements	8.3
Equipment	42.9
Gross Carrying Amount
Land	2.6	2.6
Building and Improvements	8.3	0
Equipment	42.9	0
Accumulated Depreciation	1.5
Chicago - Aurora Land B
Initial Costs
Land	5.1
Building and Improvements	0
Equipment	0
Cost Capitalized Subsequent to Acquisition
Land	0
Building and Improvements	0
Equipment	0
Gross Carrying Amount
Land	5.1	5.1
Building and Improvements	0	0
Equipment	0	0
Accumulated Depreciation	0
Dallas - Allen
Initial Costs
Land	12
Building and Improvements	0
Equipment	0
Cost Capitalized Subsequent to Acquisition
Land	0
Building and Improvements	0
Equipment	0
Gross Carrying Amount
Land	12	0
Building and Improvements	0	0
Equipment	0	0
Accumulated Depreciation	0
Quincy Land A
Initial Costs
Land	3.1
Building and Improvements	0
Equipment	0
Cost Capitalized Subsequent to Acquisition
Land	0
Building and Improvements	0
Equipment	0
Gross Carrying Amount
Land	3.1	0
Building and Improvements	0	0
Equipment	0	0
Accumulated Depreciation	0
Atlanta I
Initial Costs
Land	5.1
Building and Improvements	0
Equipment	0
Cost Capitalized Subsequent to Acquisition
Land	0
Building and Improvements	0
Equipment	0
Gross Carrying Amount
Land	5.1	0
Building and Improvements	0	0
Equipment	0	$ 0
Accumulated Depreciation	$ 0

Schedule III. Real Estate Pro98

Schedule III. Real Estate Properties and Accumulated Depreciation - Historical Cost and Accumulated Depreciation and Amortization (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Property
Balance—beginning of period	$ 2,601.6	$ 1,827.6	$ 1,378.4
Disposals	(3.4)	(12)	(7)
Impairments	(71.8)	(4.9)	(9.3)
Additions (acquisitions and improvements)	1,314.4	790.9	465.5
Balance, end of period	3,840.8	2,601.6	1,827.6
Accumulated Depreciation
Balance—beginning of period	578.5	435.6	327
Disposals	(1.9)	(7.9)	(2.7)
Impairments	(14.1)	0	0
Additions (depreciation and amortization expense)	219.9	150.8	111.3
Balance, end of period	$ 782.4	$ 578.5	$ 435.6