Real Estate Investments - Summary of Land Parcels Sold (Details) $ in Thousands			1 Months Ended	3 Months Ended		9 Months Ended
	Mar. 15, 2019 USD ($) a parcel	Jan. 08, 2015 USD ($) a parcel	Jan. 31, 2019 USD ($) installment	Sep. 30, 2019 USD ($) a	Sep. 30, 2018 USD ($)	Sep. 30, 2019 USD ($) a parcel	Sep. 30, 2018 USD ($)
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Proceeds from the sale of properties						$ 41,546	$ 16,771
Gain (loss) on sale				$ 250	$ 0	$ 1,501	$ 2,859
Land
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Number of parcels of land | parcel						1
Area of land (in acres) | a				2.7		2.7
Sales price				$ 5,325		$ 5,325
Proceeds from the sale of properties						5,023
Gain (loss) on sale						1,501
Land | 9 Presidential Boulevard
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Number of parcels of land | parcel	1
Area of land (in acres) | a	2.7
Sales price	$ 5,325
Proceeds from the sale of properties	5,023
Gain (loss) on sale	$ 751
Land | Libertyview
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Number of parcels of land | parcel		0
Area of land (in acres) | a		0
Sales price		$ 0
Proceeds from the sale of properties		0				$ 800
Gain (loss) on sale		$ 750
Contingent consideration to received			$ 1,000
Number of installments | installment			12