Commitments and Contingencies - Additional Information (Detail)	1 Months Ended			3 Months Ended				9 Months Ended		12 Months Ended
	Mar. 31, 2016 USD ($)	Jun. 30, 2014 USD ($)	Feb. 28, 2014 Fires	Mar. 31, 2018 USD ($)	Dec. 31, 2017 USD ($)	Sep. 30, 2017 USD ($) ft²	Sep. 30, 2016 USD ($)	Sep. 30, 2017 USD ($) ft²	Sep. 30, 2016 USD ($)	Dec. 31, 2021 USD ($)	Dec. 31, 2016 USD ($)	Dec. 31, 2001 a
Loss Contingencies [Line Items]
Insurance Maximum Coverage Per occurrence								$ 300,000,000
Insurance Maximum Coverage Per Property								300,000,000
Annual property rental						$ 37,970,000	$ 37,598,000	114,507,000	$ 113,129,000
Deferred leasing cost, net						44,951,000		44,951,000			$ 48,387,000
Depreciation and amortization						8,430,000	$ 8,045,000	24,613,000	$ 25,745,000
Mortgages payable, net of deferred debt issuance costs						1,240,069,000		1,240,069,000			$ 1,052,359,000
Standby letters of credit, outstanding						$ 1,474,000		$ 1,474,000
Rego Park I [Member] | Sears [Member]
Loss Contingencies [Line Items]
Area of property | ft²						195,000		195,000
Annual property rental								$ 10,337,000
Straight line rent receivable								4,160,000
Deferred leasing cost, net						$ 437,000		$ 437,000
Lease expiration date								2021-03
Number of fires | Fires			2
Rego Park I [Member] | Sears [Member] | Estimated Future Damages [Member]
Loss Contingencies [Line Items]
Loss contingency, damages sought, value	$ 650,000
Rego Park I [Member] | Sears [Member] | Minimum [Member]
Loss Contingencies [Line Items]
Loss contingency, damages sought, value		$ 4,000,000
Rego Park I [Member] | Sears [Member] | Minimum [Member] | Estimated Future Damages [Member]
Loss Contingencies [Line Items]
Loss contingency, damages sought, value		$ 25,000,000
Rego Park I [Member] | Sears [Member] | Maximum [Member] | Estimated Future Damages [Member]
Loss Contingencies [Line Items]
Reasonably possible losses						650,000		$ 650,000
Paramus [Member] | IKEA [Member] | Tenant Occupant [Member]
Loss Contingencies [Line Items]
Area of land | a												30.3
Mortgages payable, net of deferred debt issuance costs						$ 68,000,000		$ 68,000,000
Fixed interest rate on the debt						2.90%		2.90%
Debt instrument maturity date								Oct. 05, 2018
Triple-net rent, annual amount								$ 700,000
Paramus [Member] | Scenario, Forecast [Member] | IKEA [Member] | Tenant Occupant [Member]
Loss Contingencies [Line Items]
Lease purchase option amount										$ 75,000,000
Loan Amortization Period										20 years
Lease term range as Lessor										20 years
Purchase option not exercised amount included in triple net rent over remainder of lease										$ 68,000,000
Purchase option exercised, gain on sale of land										60,000,000
Purchase option exercised, net cash proceeds from sale of land										$ 7,000,000
The Kings Plaza Regional Shopping Center [Member]
Loss Contingencies [Line Items]
Loss contingency, damages sought, value								$ 22,490,000
731 Lexington Avenue [Member] | Le Cirque [Member]
Loss Contingencies [Line Items]
Area of property | ft²						13,000		13,000
Annual property rental								$ 1,200,000
Depreciation and amortization						$ 280,000
Order stipulation terms approval date								Sep. 19, 2017
Original lease expiration date								2021-05
Lease expiration date								Jan. 05, 2018
Lease arrangements, unamortized assets								$ 2,780,000
731 Lexington Avenue [Member] | Scenario, Forecast [Member] | Le Cirque [Member]
Loss Contingencies [Line Items]
Depreciation and amortization				$ 130,000	$ 2,370,000
All Risk Property and Rental Value [Member]
Loss Contingencies [Line Items]
Insurance Maximum Coverage Per occurrence								1,700,000,000
Terrorism Coverage Including NBCR [Member]
Loss Contingencies [Line Items]
Insurance Maximum Coverage Per occurrence								1,700,000,000
Insurance maximum coverage in aggregate								$ 1,700,000,000
NBCR [Member]
Loss Contingencies [Line Items]
Insurance coverage end date								2020-12
Self insured responsibility						17.00%		17.00%
Federal government responsibility						83.00%		83.00%
NBCR [Member] | FNSIC [Member]
Loss Contingencies [Line Items]
Insurance deductible								$ 293,000