v3.19.3.a.u2
Cover Page - USD ($)
$ in Billions
12 Months Ended
Dec. 31, 2019
Feb. 14, 2020
Jun. 30, 2019
Cover page.      
Document Type 10-K    
Document Annual Report true    
Document Period End Date Dec. 31, 2019    
Document Transition Report false    
Entity File Number 001-35789    
Entity Registrant Name CyrusOne Inc.    
Entity Incorporation, State or Country Code MD    
Entity Tax Identification Number 46-0691837    
Entity Address, Address Line One 2850 N. Harwood Street    
Entity Address, Address Line Two Suite 2200    
Entity Address, City or Town Dallas    
Entity Address, State or Province TX    
Entity Address, Postal Zip Code 75201    
City Area Code 972    
Local Phone Number 350-0060    
Title of 12(b) Security Common Stock, $.01 par value    
Trading Symbol CONE    
Security Exchange Name NASDAQ    
Entity Well-known Seasoned Issuer Yes    
Entity Voluntary Filers No    
Entity Current Reporting Status Yes    
Entity Interactive Data Current Yes    
Entity Filer Category Large Accelerated Filer    
Entity Small Business false    
Entity Emerging Growth Company false    
Entity Shell Company false    
Entity Public Float     $ 6.5
Entity Common Stock, Shares Outstanding   114,848,445  
Entity Central Index Key 0001553023    
Current Fiscal Year End Date --12-31    
Document Fiscal Year Focus 2019    
Document Fiscal Period Focus FY    
Amendment Flag false