| Cover | May 06, 2020 | Feb. 18, 2020 |
| Cover [Abstract] | ||
| Document Type | 8-K | |
| Amendment Flag | false | |
| Document Period End Date | May 6, 2020 | |
| 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 |
