Derivative Financial Instruments - Floating-to-Fixed Interest Rate Swaps (Details) - USD ($) $ in Thousands	Dec. 31, 2020	Dec. 31, 2019
Derivative [Line Items]
Notional Amount	$ 874,606	$ 496,642
Interest rate swaps
Derivative [Line Items]
Notional Amount	340,231
Not Designated as Hedging Instrument
Derivative [Line Items]
Notional Amount	200,000	350,000
Not Designated as Hedging Instrument | Interest rate swaps
Derivative [Line Items]
Notional Amount	50,000	100,000
Not Designated as Hedging Instrument | Senior Unsecured Term Loan 2.78% | Interest rate swaps
Derivative [Line Items]
Notional Amount	$ 50,000
Fixed rate interest rate swap	2.78%
Effective interest rate	4.23%
Designated as Hedging Instrument | Interest rate swaps
Derivative [Line Items]
Notional Amount	$ 290,231	$ 146,642
Designated as Hedging Instrument | Johns Hopkins Village | Interest rate swaps
Derivative [Line Items]
Notional Amount	$ 50,859
Fixed rate interest rate swap	2.94%
Effective interest rate	4.19%
Designated as Hedging Instrument | Senior Unsecured Term Loan 3.02% | Interest rate swaps
Derivative [Line Items]
Notional Amount	$ 10,500
Fixed rate interest rate swap	3.02%
Effective interest rate	4.47%
Designated as Hedging Instrument | 249 Central Park Retail, Fountain Plaza Retail, And South Retail | Interest rate swaps
Derivative [Line Items]
Notional Amount	$ 33,872
Fixed rate interest rate swap	2.25%
Effective interest rate	3.85%
Designated as Hedging Instrument | Senior Unsecured Term Loan 2.26% | Interest rate swaps
Derivative [Line Items]
Notional Amount	$ 50,000
Fixed rate interest rate swap	2.26%
Effective interest rate	3.71%
Designated as Hedging Instrument | Thames Street Wharf | Interest rate swaps
Derivative [Line Items]
Notional Amount	$ 70,000
Fixed rate interest rate swap	0.51%
Effective interest rate	1.81%
Designated as Hedging Instrument | Senior Unsecured Term Loan 0.50%, Term Loan One [Member] | Interest rate swaps
Derivative [Line Items]
Notional Amount	$ 25,000
Fixed rate interest rate swap	0.50%
Effective interest rate	1.95%
Designated as Hedging Instrument | Senior Unsecured Term Loan 0.50%, Term Loan Two [Member] | Interest rate swaps
Derivative [Line Items]
Notional Amount	$ 25,000
Fixed rate interest rate swap	0.50%
Effective interest rate	1.95%
Designated as Hedging Instrument | Senior Unsecured Term Loan 0.55% [Member] | Interest rate swaps
Derivative [Line Items]
Notional Amount	$ 25,000
Fixed rate interest rate swap	0.55%
Effective interest rate	2.00%