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Organization (Details) $ in Thousands, ft² in Millions |  |  | 9 Months Ended | 12 Months Ended |  |  |
--- | --- | --- | --- | --- | --- | --- | ---
Apr. 01, 2021 shares | Mar. 02, 2021 shares | Sep. 30, 2021 USD ($) ft² Real_Estate_Properties yr shares | Dec. 31, 2020 USD ($) shares | Mar. 31, 2021 USD ($) | Sep. 30, 2020 USD ($) | Dec. 31, 2019 USD ($)
Real Estate Properties [Line Items] |  |  |  |  |  |  |
Restriction on redemption of OP units from date of issuance (years) | yr |  |  | 1 |  |  |  |
One OP unit is equivalent to one share of Common Stock (in shares) | shares |  |  | 1 |  |  |  |
OP unit conversion rate (in shares) | shares |  |  | 1 |  |  |  |
Number Of series Of preferred units outstanding |  |  |  | 1 |  |  |
Cash held in escrows | $ |  |  | $ 79,193 | $ 50,587 |  | $ 50,006 | $ 46,936
Dividends and distributions payable | $ |  |  | $ 169,739 | $ 171,082 |  | $ 171,070 |
Boston Properties Limited Partnership |  |  |  |  |  |  |
Real Estate Properties [Line Items] |  |  |  |  |  |  |
General and limited partnership interest in the operating partnership (percent) |  |  | 89.90% | 90.00% |  |  |
Commercial Real Estate Properties [Member] |  |  |  |  |  |  |
Real Estate Properties [Line Items] |  |  |  |  |  |  |
Number of real estate properties | Real_Estate_Properties |  |  | 202 |  |  |  |
Net Rentable Area (in sf) | ft² |  |  | 52.5 |  |  |  |
Total Properties Under Construction [ Member] |  |  |  |  |  |  |
Real Estate Properties [Line Items] |  |  |  |  |  |  |
Number of real estate properties | Real_Estate_Properties |  |  | 9 |  |  |  |
Net Rentable Area (in sf) | ft² |  |  | 4.3 |  |  |  |
Total Office Properties [Member] |  |  |  |  |  |  |
Real Estate Properties [Line Items] |  |  |  |  |  |  |
Number of real estate properties | Real_Estate_Properties |  |  | 183 |  |  |  |
Office Properties Under Construction [Member] |  |  |  |  |  |  |
Real Estate Properties [Line Items] |  |  |  |  |  |  |
Number of real estate properties | Real_Estate_Properties |  |  | 9 |  |  |  |
Retail Properties [ Member] |  |  |  |  |  |  |
Real Estate Properties [Line Items] |  |  |  |  |  |  |
Number of real estate properties | Real_Estate_Properties |  |  | 12 |  |  |  |
Residential Properties [Member] |  |  |  |  |  |  |
Real Estate Properties [Line Items] |  |  |  |  |  |  |
Number of real estate properties | Real_Estate_Properties |  |  | 6 |  |  |  |
Hotel Property [ Member] |  |  |  |  |  |  |
Real Estate Properties [Line Items] |  |  |  |  |  |  |
Number of real estate properties | Real_Estate_Properties |  |  | 1 |  |  |  |
Series B Cumulative Redeemable Preferred Stock / Unit [Member] |  |  |  |  |  |  |
Real Estate Properties [Line Items] |  |  |  |  |  |  |
Preferred Stock, Dividend Rate, Percentage |  | 5.25% |  |  |  |  |
Preferred stock / units, shares / units outstanding (in shares / units) | shares |  | 80,000 |  | 80,000 |  |  |
Preferred Stock, Redemption Date | Apr. 01, 2021 |  |  |  |  |  |
OP Units for redemption (in shares) | shares | 80,000 |  |  |  |  |  |
Depositary shares of Series B Cumulative Redeemable Preferred [Member] |  |  |  |  |  |  |
Real Estate Properties [Line Items] |  |  |  |  |  |  |
Preferred stock / units, shares / units outstanding (in shares / units) | shares |  |  |  | 8,000,000 |  |  |
OP Units for redemption (in shares) | shares | 8,000,000 |  |  |  |  |  |
Series B Preferred Units [Member] |  |  |  |  |  |  |
Real Estate Properties [Line Items] |  |  |  |  |  |  |
Preferred stock / units, shares / units outstanding (in shares / units) | shares |  |  |  | 80,000 |  |  |
Cash held in escrows | $ |  |  |  |  | $ 201,300 |  |
Dividends and distributions payable | $ |  |  |  |  | $ 1,300 |  |

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