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v3.21.1

Stock Option and Incentive Plan Stock and Units (Narrative) (Details) - USD ($) $ / shares in Units, $ in Thousands |  |  | 3 Months Ended |
--- | --- | --- | --- | ---
Feb. 05, 2021 | Feb. 02, 2021 | Mar. 31, 2021 | Mar. 31, 2020 | Dec. 31, 2020
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |  |  |
Shares issued |  |  | 156,153,100 |  | 155,797,725
Stock based compensation expense |  |  | $ 19,800 | $ 17,200 |
Common Stock, Value, Issued |  |  | $ 1,561 |  | $ 1,557
Restricted Stock [Member] |  |  |  |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |  |  |
Shares issued |  |  | 34,644 |  |
LTIP Units [Member] |  |  |  |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |  |  |
Value Of LTIP Units Issued |  |  | $ 23,000 |  |
Expected life assumed to calculate per unit fair value per LTIP unit (in years) |  |  | 5 years 8 months 12 days |  |
Risk-free rate |  |  | 0.65% |  |
Expected price volatility |  |  | 30.00% |  |
Weighted average price (per unit) |  |  | $ 83.85 |  |
MYLTIP 2018 |  |  |  |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |  |  |
Final awards percentage of target | 29.20% |  |  |  |
Value of MYLTIP Awards | $ 4,600 |  |  |  |
Forfeitures, in units | 285,925 |  |  |  |
MYLTIP 2021 |  |  |  |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |  |  |
Vesting Period |  | 3 years |  |  |
Value of MYLTIP Awards |  | $ 15,300 |  |  |
Boston Properties Limited Partnership | LTIP Units [Member] |  |  |  |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |  |  |
LTIP units issued (in shares) |  |  | 273,930 |  |
Boston Properties Limited Partnership | MYLTIP 2021 | Maximum [Member] |  |  |  |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |  |  |
Common stock available for issuance |  | 352,021 |  |  |
Restricted Stock [Member] |  |  |  |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |  |  |
Employee and director payment per share (in dollars per share) |  |  | $ 0.01 |  |
Common Stock, Value, Issued |  |  | $ 3,200 |  |
Common Stock Weighted Average Price (in dollars per share) |  |  | $ 91.67 |  |
LTIP and MYLTIP Units [Member] |  |  |  |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |  |  |
Employee and director payment per share (in dollars per share) |  |  | $ 0.25 |  |
Ltips (including vested MYLTIPS) And Restricted Stock [Member] |  |  |  |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |  |  |
Unrecognized compensation expenses |  |  | $ 33,400 |  |
Unvested MYLTIP Units [Member] |  |  |  |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |  |  |
Unrecognized compensation expenses |  |  | $ 19,200 |  |
Weighted-average period (years) |  |  | 2 years 4 months 24 days |  |

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- Definition The estimated measure of the percentage by which a share price is expected to fluctuate during a period. Volatility also may be defined as a probability-weighted measure of the dispersion of returns about the mean. The volatility of a share price is the standard deviation of the continuously compounded rates of return on the share over a specified period. That is the same as the standard deviation of the differences in the natural logarithms of the stock prices plus dividends, if any, over the period. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 718 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (f)(2)(ii) -URI http://asc.fasb.org/extlink&oid=120381028&loc=d3e5070-113901 + Details
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