| Cover Page | Feb. 17, 2021 |
| Document Information [Line Items] | |
| Document Type | 8-K |
| Document Period End Date | Feb. 17, 2021 |
| Entity Registrant Name | CYRUSONE INC. |
| Entity Incorporation, State or Country Code | MD |
| Entity File Number | 001-35789 |
| 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 |
| Written Communications | false |
| Soliciting Material | false |
| Pre-commencement Tender Offer | false |
| Pre-commencement Issuer Tender Offer | false |
| Entity Emerging Growth Company | false |
| Entity Central Index Key | 0001553023 |
| Amendment Flag | false |
| Common Stock, $0.01 par value | |
| Document Information [Line Items] | |
| Title of 12(b) Security | Common Stock, $0.01 par value |
| Trading Symbol | CONE |
| Security Exchange Name | NASDAQ |
| 1.450% Senior Notes due 2027 | |
| Document Information [Line Items] | |
| Title of 12(b) Security | 1.450% Senior Notes due 2027 |
| Trading Symbol | CONE27 |
| Security Exchange Name | NASDAQ |
