Real Estate Investments - Summary of Land Parcels Sold (Details) $ in Thousands			3 Months Ended
	Mar. 15, 2019 USD ($) a Parcel	Jan. 08, 2015 USD ($) a Parcel	Mar. 31, 2019 USD ($) a Parcel	Mar. 31, 2018 USD ($)
Income Statement Balance Sheet And Additional Disclosures By Disposal Groups Including Discontinued Operations [Line Items]
Proceeds from the sale of properties			$ 5,273	$ 14,921
Gain on Sale			$ 1,001	$ 22
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
Sales Price			$ 5,325
Proceeds from the sale of properties			5,273
Gain on Sale			1,001
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		250	$ 300
Gain on Sale		$ 250