Leases - Summary of Future Lease Payments due from Company Under Ground, Office and Equipment Operating Leases (ASC 840) (Details) $ in Thousands	Dec. 31, 2018 USD ($)
Operating Leased Assets [Line Items]
2019	$ 1,385
2020	1,087
2021	1,011
2022	996
2023	682
Thereafter	1,093
Total	6,254
Office and Ground Leases to be Paid by the Company
Operating Leased Assets [Line Items]
2019	893
2020	759
2021	680
2022	669
2023	656
Thereafter	1,093
Total	4,750
Ground Leases to be Paid Directly by the Company's Tenants
Operating Leased Assets [Line Items]
2019	492
2020	328
2021	331
2022	327
2023	26
Total	$ 1,504