Segment Information - Schedule of Reconciliation of Net Income Attributable to Parent (Details) - USD ($)	3 Months Ended			9 Months Ended
	Sep. 30, 2018	Dec. 31, 2017	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Business Acquisition [Line Items]
Net income (loss) attributable to common shareholders	$ 22,830,000		$ (69,831,000)	$ 39,214,000	$ (57,851,000)
Depreciation and amortization	46,603,000		43,951,000	143,880,000	109,726,000
Corporate and other	12,415,000		10,593,000	37,759,000	35,536,000
Third-party real estate services	20,754,000		21,178,000	64,552,000	30,362,000
Share-based compensation related to Formation Transaction	8,387,000		14,445,000	26,912,000	14,445,000
Transaction and other costs	4,126,000		104,095,000	12,134,000	115,173,000
Interest expense	18,979,000		15,309,000	56,263,000	43,813,000
Loss on extinguishment of debt	79,000		689,000	4,536,000	689,000
Reduction of gain (gain) on bargain purchase	0	$ (3,400,000)	(27,771,000)	7,606,000	(27,771,000)
Income tax benefit	(841,000)		(1,034,000)	(1,436,000)	(317,000)
Net (income) loss attributable to redeemable noncontrolling interests	3,552,000		(8,160,000)	6,532,000	(2,481,000)
Third-party real estate services, including reimbursements	23,788,000		25,141,000	72,278,000	38,881,000
Other income	1,708,000		1,158,000	4,904,000	3,701,000
Income (loss) from unconsolidated real estate ventures, net	13,484,000		(1,679,000)	15,418,000	(1,365,000)
Interest and other income (loss), net	4,091,000		(379,000)	5,177,000	1,366,000
Gains (Losses) on Sales of Investment Real Estate	11,938,000		0	45,789,000	0
Net loss attributable to noncontrolling interests	0		0	(127,000)	0
Consolidated NOI	81,875,000		79,223,000	$ 254,259,000	218,741,000
JBG Companies [Member]
Business Acquisition [Line Items]
Transaction and other costs	$ 4,126,000		$ 104,095,000		$ 115,200,000