| Document and Entity Information | Nov. 03, 2020 |
| Document and Entity Information [Abstract] | |
| Document Type | 8-K |
| Document Period End Date | Nov. 3, 2020 |
| Entity File Number | 001-37994 |
| Entity Registrant Name | JBG SMITH PROPERTIES |
| Entity Incorporation, State or Country Code | MD |
| Entity Tax Identification Number | 81-4307010 |
| Entity Address, Address Line One | 4747 Bethesda Avenue |
| Entity Address, Adress Line Two | Suite 200 |
| Entity Address, City or Town | Bethesda |
| Entity Address, State or Province | MD |
| Entity Address, Postal Zip Code | 20814 |
| City Area Code | 240 |
| Local Phone Number | 333-3600 |
| Written Communications | false |
| Soliciting Material | false |
| Pre-commencement Tender Offer | false |
| Pre-commencement Issuer Tender Offer | false |
| Title of 12(b) Security | Common Shares, par value $0.01 per share |
| Trading Symbol | JBGS |
| Security Exchange Name | NYSE |
| Entity Emerging Growth Company | false |
| Entity Central Index Key | 0001689796 |
| Amendment Flag | false |
