Real Estate Investments - Summary of Land Parcels Sold (Details) $ in Thousands			3 Months Ended		6 Months Ended
	Mar. 15, 2019 USD ($) a	Jan. 08, 2015 USD ($) a Parcel	Jun. 30, 2019 USD ($) a	Jun. 30, 2018 USD ($)	Jun. 30, 2019 USD ($) a Parcel	Jun. 30, 2018 USD ($)
Income Statement Balance Sheet And Additional Disclosures By Disposal Groups Including Discontinued Operations [Line Items]
Proceeds from the sale of properties					$ 5,523	$ 16,771
Gain on Sale			$ 250	$ 2,837	$ 1,251	$ 2,859
Land [Member]
Income Statement Balance Sheet And Additional Disclosures By Disposal Groups Including Discontinued Operations [Line Items]
Number of Parcels | Parcel					1
Acreage of Land | a			2.7		2.7
Sales Price			$ 5,325		$ 5,325
Proceeds from the sale of properties					5,023
Gain on Sale					$ 1,251
Land [Member] | 9 Presidential Boulevard [Member]
Income Statement Balance Sheet And Additional Disclosures By Disposal Groups Including Discontinued Operations [Line Items]
Number of Parcels | Parcel					1
Acreage of Land | a	2.7
Sales Price	$ 5,325
Proceeds from the sale of properties	5,023
Gain on Sale	$ 751
Land [Member] | Libertyview [Member]
Income Statement Balance Sheet And Additional Disclosures By Disposal Groups Including Discontinued Operations [Line Items]
Number of Parcels | Parcel		0
Acreage of Land | a		0
Sales Price		$ 0
Proceeds from the sale of properties		0			$ 500
Gain on Sale		$ 500