Common Stock Weighted Average Price.

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- Definition

Employee and director payment per share

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- Definition

Value Of LTIP Units Issued.

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- Definition

Amount of expense for award under share-based payment arrangement. Excludes amount capitalized.

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- Definition

Total number of common shares of an entity that have been sold or granted to shareholders (includes common shares that were issued, repurchased and remain in the treasury). These shares represent capital invested by the firm's shareholders and owners, and may be all or only a portion of the number of shares authorized. Shares issued include shares outstanding and shares held in the treasury.

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- Definition

Aggregate par or stated value of issued nonredeemable common stock (or common stock redeemable solely at the option of the issuer). This item includes treasury stock repurchased by the entity. Note: elements for number of nonredeemable common shares, par value and other disclosure concepts are in another section within stockholders' equity.

+ References

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- Definition

Amount of cost not yet recognized for nonvested award under share-based payment arrangement.

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- Definition

Weighted-average period over which cost not yet recognized is expected to be recognized for award under share-based payment arrangement, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents reported fact of one year, five months, and thirteen days.

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- Definition

Period over which grantee's right to exercise award under share-based payment arrangement is no longer contingent on satisfaction of service or performance condition, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents reported fact of one year, five months, and thirteen days. Includes, but is not limited to, combination of market, performance or service condition.

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- Definition

Discount rate from fair value on offering date that participants pay for shares.

+ References

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- Definition

Per share or unit weighted-average intrinsic value of nonvested award under share-based payment arrangement. Excludes share and unit options.

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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.

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- Definition

The risk-free interest rate assumption that is used in valuing an option on its own shares.

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- Definition

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

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No definition available.

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- Definition

Number of shares authorized for issuance under share-based payment arrangement.

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- Definition

Amount by which the current fair value of the underlying stock exceeds the exercise price of options outstanding.

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- Definition

Number of options outstanding, including both vested and non-vested options.

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- Definition

Weighted average price at which grantees can acquire the shares reserved for issuance under the stock option plan.

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- Definition

Per share weighted-average price paid for shares purchased on open market for issuance under share-based payment arrangement.

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- Definition

Number of shares issued under share-based payment arrangement.

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Expected term of award under share-based payment arrangement, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents reported fact of one year, five months, and thirteen days.

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Stock Option and Incentive Plan Stock and Units (Narrative) (Details) - USD ($) $ / shares in Units, $ in Thousands		12 Months Ended
	Feb. 04, 2020	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares issued		155,797,725	154,869,198
Stock based compensation expense		$ 43,000	$ 39,800	$ 38,000
Common Stock, Value, Issued		1,557	$ 1,548
Intrinsic Value of stock options		$ 400
Vesting Period		4 years
Beginning outstanding, shares		351,561	395,353	540,441	540,441
Weighted Average Exercise Price		$ 96.97	$ 96.37	$ 96.35	$ 96.35
Restricted Stock [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares issued		29,630	26,503	20,320
LTIP Units [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Value Of LTIP Units Issued		$ 26,300	$ 22,100	$ 22,700
Expected life assumed to calculate per unit fair value per LTIP unit (in years)		5 years 8 months 12 days	5 years 8 months 12 days	5 years 8 months 12 days
Risk-free rate		1.47%	2.68%	2.63%
Expected price volatility		18.00%	27.00%	27.00%
Weighted average price (per unit)		$ 127.14	$ 121.50	$ 110.29
Employee Stock
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Common stock available for issuance		250,000
Number of shares issued		7,195	5,862	6,268
Employee discount		85.00%
Weighted Average Price of Shares Purchased		$ 90.53	$ 104.11	$ 107.20
stock option
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Intrinsic Value of stock options		$ 0	$ 0	$ 0
Boston Properties Limited Partnership \| LTIP Units [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of shares issued		207,181	181,919	205,838
Boston Properties Limited Partnership \| MYLTIP 2020 [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of shares issued		203,278
Boston Properties Limited Partnership \| MYLTIP 2019 [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of shares issued			220,734
Boston Properties Limited Partnership \| MYLTIP 2018
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of shares issued				342,659
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		$ 4,000	$ 3,500	$ 2,400
Common Stock Weighted Average Price (in dollars per share)		$ 133.81	$ 131.27	$ 119.27
MYLTIP 2020 [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Vesting Period	4 years
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		$ 25,400
Unvested MYLTIP Units [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Unrecognized compensation expenses		$ 10,300
Weighted-average period (years)		2 years 1 month 6 days