Redeemable Noncontrolling Interests - Summary of the Activity of Redeemable Noncontrolling Interests (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018
Temporary Equity
Beginning Balance	$ 584,763	$ 605,504	$ 558,140	$ 609,129
Fair value of OP Unit redemptions	(316)	0	(57,318)	0
LTIP Units issued in lieu of cash bonuses (1)	818	0	3,954	0
Net income (loss) attributable to redeemable noncontrolling interests	(288)	3,574	3,099	2,980
Other comprehensive income	(1,503)	834	(2,886)	2,710
Temporary Equity, Contributions (Distributions)	(3,838)	(4,157)	(3,838)	(4,157)
Share-based compensation expense	15,343	14,136	31,616	27,078
Adjustment to redemption value	(20,751)	45,732	41,461	27,883
Ending Balance	574,228	665,623	574,228	665,623
JBG Smith, LP
Temporary Equity
Beginning Balance	578,781	600,094	552,159	603,717
Fair value of OP Unit redemptions	(316)	0	(57,318)	0
LTIP Units issued in lieu of cash bonuses (1)	818	0	3,954	0
Net income (loss) attributable to redeemable noncontrolling interests	(292)	3,577	3,094	2,985
Other comprehensive income	(1,503)	834	(2,886)	2,710
Temporary Equity, Contributions (Distributions)	(3,838)	(4,657)	(3,838)	(4,657)
Share-based compensation expense	15,343	14,136	31,616	27,078
Adjustment to redemption value	(20,751)	45,732	41,461	27,883
Ending Balance	568,242	659,716	568,242	659,716
Consolidated Real Estate Venture
Temporary Equity
Beginning Balance	5,982	5,410	5,981	5,412
Fair value of OP Unit redemptions	0	0	0	0
LTIP Units issued in lieu of cash bonuses (1)	0	0	0	0
Net income (loss) attributable to redeemable noncontrolling interests	4	(3)	5	(5)
Other comprehensive income	0	0	0	0
Temporary Equity, Contributions (Distributions)	0	500	0	500
Share-based compensation expense	0	0	0	0
Adjustment to redemption value	0	0	0	0
Ending Balance	$ 5,986	$ 5,907	$ 5,986	$ 5,907