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Subsequent Events (Details) $ in Thousands					9 Months Ended
		Oct. 17, 2025 USD ($)	Oct. 16, 2025 USD ($)	Oct. 08, 2025 USD ($) ft²	Sep. 30, 2025 USD ($)	Sep. 30, 2024 USD ($)
Subsequent Event [Line Items]
Repayments of Secured Debt					$ 3,195	$ 3,461
BNY Tower Holdings LLC [Member]
Subsequent Event [Line Items]
Ownership Percentage	[1]				50.00%
3 Hudson Boulevard [Member]
Subsequent Event [Line Items]
Ownership Percentage					25.00%
Boston Properties Limited Partnership
Subsequent Event [Line Items]
Repayments of Secured Debt					$ 3,195	$ 3,461
Subsequent Event [Member] | Unconsolidated Properties | BNY Tower Holdings LLC [Member]
Subsequent Event [Line Items]
Ownership Percentage				50.00%
Subsequent Event [Member] | Unconsolidated Properties | 3 Hudson Boulevard [Member]
Subsequent Event [Line Items]
Ownership Percentage		25.00%
Subsequent Event [Member] | Plaza at Almaden
Subsequent Event [Line Items]
Proceeds from Sale, Real Estate, Held-for-Investment		$ 12,700
Contractual Sale Price		13,500
Subsequent Event [Member] | BNY Tower Holdings LLC [Member] | Unconsolidated Properties
Subsequent Event [Line Items]
Debt Instrument, Basis Spread on Variable Rate				2.50%
Net Rentable Area (in sf) | ft²				669,000
Debt Instrument, Maturity Date				Dec. 18, 2025
Repayments of Secured Debt				$ 198,400
Subsequent Event [Member] | 3 Hudson Boulevard [Member] | Unconsolidated Properties
Subsequent Event [Line Items]
Debt Instrument, Basis Spread on Variable Rate			3.61%
Debt Instrument, Increase, Accrued Interest			$ 51,400
Debt Instrument, Interest Rate, Increase (Decrease)			4.00%
Debt Instrument, Decrease, Forgiveness		5,800
Repayments of Secured Debt		$ 80,000
Subsequent Event [Member] | 3 Hudson Boulevard [Member] | Unconsolidated Properties | Senior Loans
Subsequent Event [Line Items]
Debt Instrument, Basis Spread on Variable Rate		5.25%
Debt Instrument, Maturity Date		Nov. 09, 2027
Debt		$ 108,000
Extension Option (in years)		1
Subsequent Event [Member] | 3 Hudson Boulevard [Member] | Unconsolidated Properties | Subordinated Debt
Subsequent Event [Line Items]
Debt Instrument, Basis Spread on Variable Rate		7.25%
Debt Instrument, Maturity Date		Nov. 09, 2027
Debt		$ 17,600
Extension Option (in years)		1
Subsequent Event [Member] | 3 Hudson Boulevard [Member] | Unconsolidated Properties | Subordinated Debt | Maximum [Member]
Subsequent Event [Line Items]
Debt		$ 50,000
[1] This investment includes net equity balances from the amenity joint venture.

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