| Cover | Feb. 22, 2021 |
| Cover [Abstract] | |
| Document Type | 8-K |
| Amendment Flag | false |
| Document Period End Date | Feb. 22, 2021 |
| Entity Registrant Name | EXTRA SPACE STORAGE INC. |
| Entity Central Index Key | 0001289490 |
| Entity Incorporation, State or Country Code | MD |
| Entity File Number | 001-32269 |
| Entity Tax Identification Number | 20-1076777 |
| Entity Address, Address Line One | 2795 East Cottonwood Parkway, Suite 300 |
| Entity Address, City or Town | Salt Lake City |
| Entity Address, State or Province | UT |
| Entity Address, Postal Zip Code | 84121 |
| City Area Code | 801 |
| Local Phone Number | 365-4600 |
| Written Communications | false |
| Soliciting Material | false |
| Pre-commencement Tender Offer | false |
| Pre-commencement Issuer Tender Offer | false |
| Entity Emerging Growth Company | false |
| Title of 12(b) Security | Common Stock, $0.01 par value |
| Trading Symbol | EXR |
| Security Exchange Name | NYSE |
