Summary of Significant Accounting Policies - Additional Information (Details) - USD ($)	3 Months Ended		6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018	Jan. 01, 2019	Dec. 31, 2018
Provision for income tax	$ 246,000	$ 274,000	$ 484,000	$ 487,000
Percentage of rental income excluded from accounting standard adoption			94.00%
Percentage of total revenue subject to revenue recognition standard			6.00%
Right-of-use assets	431,753,000		$ 431,753,000		$ 434,201,000	$ 0
Lease liabilities	$ 281,620,000		281,620,000		$ 278,287,000	$ 0
Federal [Member]
Provision for income tax			$ 0