Fair Value Measurements - Fair Value of Financial Instruments Presented at Carrying Values (Details) - USD ($) $ in Thousands	Jun. 30, 2019	Dec. 31, 2018
Carrying Value
Debt Instrument [Line Items]
Mortgages payable	$ 200,489	$ 213,925
Term loans	352,000	352,000
Estimated Fair Value
Debt Instrument [Line Items]
Mortgages payable	203,312	212,572
Term loans	$ 351,993	$ 352,006