Basis of Presentation - Additional Information (Detail) $ in Thousands	3 Months Ended
	Mar. 31, 2019 USD ($) segment	Mar. 31, 2018 USD ($)	Dec. 31, 2018 USD ($)
Error Corrections and Prior Period Adjustments Restatement [Line Items]
Decrease to mortgages payable, net of deferred debt issuance costs	$ (967,112)		$ (965,826)
Number of reportable segments | segment	1
Previously Reported
Error Corrections and Prior Period Adjustments Restatement [Line Items]
Rego Park II Loan Participation			195,708
Restatement Adjustment
Error Corrections and Prior Period Adjustments Restatement [Line Items]
Property rentals		$ 38,241
Expense reimbursements		$ 19,639
Restatement to reclassify Rego Park II as a reduction to mortgage payable, net of deferred debt issuance costs | Restatement Adjustment
Error Corrections and Prior Period Adjustments Restatement [Line Items]
Decrease to mortgages payable, net of deferred debt issuance costs			$ 195,708