Revenues - Summary of Revenues (Parenthetical) (Details) - USD ($)	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Disaggregation Of Revenue [Line Items]
Lease termination income	$ 2,985,000	$ 2,189,000	$ 17,010,000
1633 Broadway [Member]
Disaggregation Of Revenue [Line Items]
Lease termination income			$ 10,861