Dispositions (Assets and liabilities related to dispositions) (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017	Dec. 31, 2017
Dispositions
Other assets	$ 275		$ 1,357
Other liabilities	1,176		$ 3,620
(Loss) income from discontinued operations:
Total revenues	354	$ 116,283
Total expenses	717	95,712
Income from discontinued operations before net gain on sale of real estate	(363)	20,571
JBG SMITH Properties spin-off transaction costs	0	(7,253)
Net gains on sale of real estate and other	0	2,354
Pretax (loss) income from discontinued operations	(363)	15,672
Income tax expense	0	(354)
(Loss) income from discontinued operations	(363)	15,318
Cash flows related to discontinued operations:
Cash flows from operating activities	(1,725)	41,306
Cash flows from investing activities	$ 0	$ (25,210)