Cover Page - shares	9 Months Ended
	Sep. 30, 2019	Oct. 31, 2019
Cover page.
Document Transition Report	false
Document Type	10-Q
Document Quarterly Report	true
Document Period End Date	Sep. 30, 2019
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	4445 Willard Avenue
Entity Address, City or Town	Chevy Chase
Entity Address, State or Province	MD
Entity Address, Postal Zip Code	20815
City Area Code	240
Local Phone Number	333-3600
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
Title of 12(b) Security	Common Shares, par value $0.01 per share
Trading Symbol	JBGS
Security Exchange Name	NYSE
Entity Common Stock, Shares Outstanding		134,127,004
Entity Central Index Key	0001689796
Current Fiscal Year End Date	--12-31
Document Fiscal Year Focus	2019
Document Fiscal Period Focus	Q3
Amendment Flag	false
Entity Address, Address Line Two	Suite 400