Derivative Financial Instruments - Additional Information (Details) - USD ($)		3 Months Ended
	Oct. 12, 2018	Sep. 30, 2018	Jul. 27, 2018	Jul. 16, 2018	Apr. 23, 2018	Mar. 07, 2018	Dec. 31, 2017
Derivatives
Interest rate agreement, notional amount		$ 452,930,000					$ 401,079,000
Unrealized losses		130,000
Realized gain (loss) reclassified to earnings		(67,000)
Gain (loss) reclassified during next 12 months		(173,000)
Johns Hopkins Village
Derivatives
Effective interest rate			4.19%
Not designated as accounting hedges
Derivatives
Interest rate agreement, notional amount		400,000,000					401,079,000
Not designated as accounting hedges | Interest Rate Caps
Derivatives
Interest rate agreement, notional amount		300,000,000		$ 50,000,000		$ 50,000,000.0	345,000,000
Strike rate				2.50%		2.25%
Interest rate cap agreement, premium (less than)				$ 300,000		$ 300,000
Not designated as accounting hedges | Interest Rate Swaps
Derivatives
Interest rate agreement, notional amount		$ 100,000,000					$ 56,079,000
Not designated as accounting hedges | Interest Rate Swaps | Operating Partnership
Derivatives
Interest rate agreement, notional amount					$ 50,000,000.0
Fixed interest rate					2.783%
Line of credit | Subsequent Event | Secured Debt | Lightfoot Marketplace
Derivatives
Proceeds from lines of credit	$ 10,500,000