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Commitments and Contingencies - Additional Information (Detail) ft² in Thousands |  | 1 Months Ended | 9 Months Ended |  |  |
--- | --- | --- | --- | --- | --- | ---
Apr. 05, 2018 USD ($) | Oct. 31, 2021 USD ($) | Mar. 31, 2016 USD ($) | Feb. 28, 2014 fire | Sep. 30, 2020 USD ($) | Dec. 31, 2019 USD ($) | Jun. 30, 2014 ft² | Dec. 31, 2001 a
Loss Contingencies [Line Items] |  |  |  |  |  |  |  |
Mortgages payable, net of deferred debt issuance costs |  |  |  |  | $ 1,066,403,000 | $ 970,961,000 |  |
Real property transfer tax | $ 23,797,000 |  |  |  |  |  |  |
Additional real property transfer tax expense | 15,874,000 |  |  |  |  |  |  |
Real property transfer tax interest | $ 7,923,000 |  |  |  |  |  |  |
Standby letters of credit, outstanding |  |  |  |  | 1,030,000 |  |  |
Rego Park I | Sears |  |  |  |  |  |  |  |
Loss Contingencies [Line Items] |  |  |  |  |  |  |  |
Area of property (in sqft.) | ft² |  |  |  |  |  |  | 195 |
Number of fires | fire |  |  |  | 2 |  |  |  |
Rego Park I | Sears | Estimated Future Damages |  |  |  |  |  |  |  |
Loss Contingencies [Line Items] |  |  |  |  |  |  |  |
Loss contingency, damages sought, value |  |  | $ 650,000 |  |  |  |  |
Rego Park I | Sears | Minimum |  |  |  |  |  |  |  |
Loss Contingencies [Line Items] |  |  |  |  |  |  |  |
Loss contingency, damages sought, value |  |  |  |  | 4,000,000 |  |  |
Rego Park I | Sears | Minimum | Estimated Future Damages |  |  |  |  |  |  |  |
Loss Contingencies [Line Items] |  |  |  |  |  |  |  |
Loss contingency, damages sought, value |  |  |  |  | 25,000,000 |  |  |
Rego Park I | Sears | Maximum | Estimated Future Damages |  |  |  |  |  |  |  |
Loss Contingencies [Line Items] |  |  |  |  |  |  |  |
Reasonably possible losses |  |  |  |  | $ 650,000 |  |  |
Tenant Occupant | Paramus | IKEA |  |  |  |  |  |  |  |
Loss Contingencies [Line Items] |  |  |  |  |  |  |  |
Area of land (in acres) | a |  |  |  |  |  |  |  | 30.3
Fixed interest rate on the debt |  |  |  |  | 4.72% |  |  |
Debt instrument maturity date |  |  |  |  | Oct. 04, 2021 |  |  |
Triple-net rent, annual amount |  |  |  |  | $ 700,000 |  |  |
Mortgages payable, net of deferred debt issuance costs |  |  |  |  | 68,000,000 |  |  |
Forecast | Tenant Occupant | Paramus | IKEA |  |  |  |  |  |  |  |
Loss Contingencies [Line Items] |  |  |  |  |  |  |  |
Lease purchase option amount |  | $ 75,000,000 |  |  |  |  |  |
Purchase option not exercised amount included in triple net rent over remainder of lease |  | 68,000,000 |  |  |  |  |  |
Purchase option exercised, net cash proceeds from sale of land |  | 7,000,000 |  |  |  |  |  |
Purchase option exercised, gain on sale of land |  | $ 60,000,000 |  |  |  |  |  |
Lease term range as Lessor |  | 20 years |  |  |  |  |  |
Loan amortization period |  | 20 years |  |  |  |  |  |
All Risk Property and Rental Value |  |  |  |  |  |  |  |
Loss Contingencies [Line Items] |  |  |  |  |  |  |  |
Insurance maximum coverage per occurrence |  |  |  |  | 1,700,000,000 |  |  |
Terrorism Coverage Including NBCR |  |  |  |  |  |  |  |
Loss Contingencies [Line Items] |  |  |  |  |  |  |  |
Insurance maximum coverage per occurrence |  |  |  |  | 1,700,000,000 |  |  |
Insurance maximum coverage in aggregate |  |  |  |  | $ 1,700,000,000 |  |  |
NBCR |  |  |  |  |  |  |  |
Loss Contingencies [Line Items] |  |  |  |  |  |  |  |
Insurance coverage end date |  |  |  |  | Dec. 01, 2027 |  |  |
Federal government responsibility |  |  |  |  | 80.00% |  |  |
NBCR | FNSIC |  |  |  |  |  |  |  |
Loss Contingencies [Line Items] |  |  |  |  |  |  |  |
Insurance deductible |  |  |  |  | $ 268,000 |  |  |
Self insured responsibility |  |  |  |  | 20.00% |  |  |
General Liability |  |  |  |  |  |  |  |
Loss Contingencies [Line Items] |  |  |  |  |  |  |  |
Insurance maximum coverage per occurrence |  |  |  |  | $ 300,000,000 |  |  |
Insurance maximum coverage per property |  |  |  |  | 300,000,000 |  |  |
Disease Coverage |  |  |  |  |  |  |  |
Loss Contingencies [Line Items] |  |  |  |  |  |  |  |
Insurance maximum coverage per occurrence |  |  |  |  | $ 1,000,000 |  |  |

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