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number of buildings

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Area of land held.

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Purchase price of expected asset acquisition prior to consideration being transferred.

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Percentage points added to the reference rate to compute the variable rate on the debt instrument.

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The percentage of ownership of common stock or equity participation in the investee accounted for under the equity method of accounting.

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The amount of interest income and other income recognized during the period. Included in this element is interest derived from investments in debt securities, cash and cash equivalents, and other investments which reflect the time value of money or transactions in which the payments are for the use or forbearance of money and other income from ancillary business-related activities (that is, excluding major activities considered part of the normal operations of the business).

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Net rentable area for properties owned.

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The number of units in a real estate property owned as of the balance sheet date.

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Amount of cash and cash equivalents restricted as to withdrawal or usage, classified as current. Cash includes, but is not limited to, currency on hand, demand deposits with banks or financial institutions, and other accounts with general characteristics of demand deposits. Cash equivalents include, but are not limited to, short-term, highly liquid investments that are both readily convertible to known amounts of cash and so near their maturity that they present insignificant risk of changes in value because of changes in interest rates.

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Carrying value as of the balance sheet date, including the current and noncurrent portions, of collateralized debt obligations (with maturities initially due after one year or beyond the operating cycle, if longer). Such obligations include mortgage loans, chattel loans, and any other borrowings secured by assets of the borrower.

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Subsequent Events (Details) $ in Thousands						3 Months Ended
Subsequent Events (Details) $ in Thousands	Apr. 28, 2022 ft²	Apr. 18, 2022 USD ($) ft²	Apr. 14, 2022 USD ($) ft²	Apr. 07, 2022 USD ($) a ft²	Apr. 19, 2021 USD ($) a ft²	Mar. 31, 2022 USD ($)	Mar. 31, 2021 USD ($)	Dec. 31, 2021 USD ($)	Dec. 31, 2020 USD ($)
Subsequent Event [Line Items]
Interest and Other Income						$ 1,228	$ 1,168
Secured Debt						3,268,745		$ 3,267,914
Cash held in escrows						$ 46,072	$ 251,814	$ 48,466	$ 50,587
11251 Roger Bacon Drive
Subsequent Event [Line Items]
Net Rentable Area (in sf) \| ft²					65,000
Area of Land \| a					2.6
Asset Acquisition, Price of Acquisition, Expected					$ 5,600
Subsequent Event [Member] \| 11251 Roger Bacon Drive
Subsequent Event [Line Items]
Interest and Other Income				$ 6,900
Net Rentable Area (in sf) \| ft²				65,000
Area of Land \| a				2.6
Subsequent Event [Member] \| Madison Centre
Subsequent Event [Line Items]
Net Rentable Area (in sf) \| ft²			760,000
Asset Acquisition, Price of Acquisition, Expected			$ 730,000
Number of floors			37
Cash held in escrows			$ 50,000
Subsequent Event [Member] \| Hub50House [Member]
Subsequent Event [Line Items]
Ownership Percentage		50.00%
Secured Debt		$ 176,500
Debt Instrument, Basis Spread on Variable Rate		2.00%
Debt Instrument, Maturity Date		Jun. 19, 2022
Subsequent Event [Member] \| Hub50House [Member] \| Residential Building
Subsequent Event [Line Items]
Net Rentable Area (in sf) \| ft²		320,000
Number of Units in Real Estate Property		440
Subsequent Event [Member] \| 290 Binney Street
Subsequent Event [Line Items]
Net Rentable Area (in sf) \| ft²	570,000
Subsequent Event [Member] \| Kendall Center future development \| Scenario, Plan
Subsequent Event [Line Items]
Net Rentable Area (in sf) \| ft²	1,100,000
Number of buildings	2
Subsequent Event [Member] \| Kendall Center future development \| Residential Building \| Scenario, Plan
Subsequent Event [Line Items]
Net Rentable Area (in sf) \| ft²	400,000