Derivative Financial Instruments - Additional Information (Details) - USD ($)			3 Months Ended
	Mar. 11, 2019	Oct. 12, 2018	Mar. 31, 2019	Mar. 31, 2018	Apr. 04, 2019	Dec. 31, 2018	Jul. 27, 2018	Apr. 23, 2018
Derivative [Line Items]
Notional Amount			$ 462,977,000			$ 513,208,000
Unrealized cash flow hedge losses			(1,003,000)	$ 0
Realized cash flow hedge losses reclassified to net income			72,000	$ 0
Gain (loss) reclassified during next 12 months			(400,000)
Johns Hopkins Village
Derivative [Line Items]
Effective interest rate							4.19%
Not designated as accounting hedges
Derivative [Line Items]
Notional Amount			400,000,000			450,000,000
Not designated as accounting hedges | Interest Rate Swaps
Derivative [Line Items]
Notional Amount			$ 100,000,000			$ 100,000,000
Not designated as accounting hedges | Interest Rate Swaps | Operating Partnership
Derivative [Line Items]
Notional Amount								$ 50,000,000.0
Fixed interest rate								2.78%
Line of credit | Secured Debt | Lightfoot Marketplace
Derivative [Line Items]
Proceeds from lines of credit	$ 7,400,000	$ 10,500,000
Initial Tranche | Line of credit | Secured Debt | Lightfoot Marketplace
Derivative [Line Items]
Effective interest rate		4.77%
Stabilization Of Property | Initial Tranche | Line of credit | Secured Debt | Lightfoot Marketplace
Derivative [Line Items]
Effective interest rate		4.62%
Maturity 2022 | Subsequent Event | LIBOR | Interest Rate Swaps
Derivative [Line Items]
Notional Amount					$ 50,000,000.0
Fixed interest rate					2.26%
Amortizing, Maturity 2023 | Subsequent Event | LIBOR | Interest Rate Swaps
Derivative [Line Items]
Notional Amount					$ 34,600,000.0
Fixed interest rate					2.25%