Subsequent Events	12 Months Ended
Subsequent Events	Dec. 31, 2018
Subsequent Events [Abstract]
Subsequent Events	19. Subsequent Events On January 28, 2020, the Company entered into a joint venture with a third party to own, operate and develop properties at its Gateway Commons complex located in South San Francisco, California. The Company contributed its 601, 611 and 651 Gateway properties and development rights with an agreed upon value aggregating approximately $350.0 million for its 50% interest in the joint venture. 601, 611 and 651 Gateway consist of three Class A office properties aggregating approximately 768,000 net rentable square feet. The partner contributed three properties and development rights with an agreed upon value aggregating approximately $280.8 million at closing and will contribute cash totaling approximately $69.2 million in the future for its 50% ownership interest in the joint venture. On January 28, 2020, a joint venture in which the Company has a 55% interest commenced development of the first phase of its Platform 16 project located in San Jose, California. The first phase of the Platform 16 development project consists of an approximately 390,000 net rentable square foot Class A office building and a below-grade parking garage. On February 20, 2020, the joint venture acquired the land under the ground lease for a purchase price totaling approximately $134.8 million. The joint venture had previously made a deposit totaling $15.0 million, which deposit was credited against the purchase price. Platform 16 consists of a parcel of land totaling approximately 5.6 acres that will support the development of approximately 1.1 million square feet of commercial office space (See Notes 3 and 5). On January 28, 2020, the Company exercised its option to acquire real property at 425 Fourth Street located in San Francisco, California for a purchase price totaling approximately $134.1 million. 425 Fourth Street will support the development of approximately 804,000 square feet of primarily commercial office space. The Company expects to complete the acquisition during the second quarter of 2020. On January 31, 2020 and February 4, 2020, Boston Properties, Inc. issued an aggregate of 24,503 shares of restricted Common Stock and Boston Properties Limited Partnership issued an aggregate of 196,927 LTIP Units under the 2012 Plan to certain employees of Boston Properties, Inc. On February 4, 2020, Boston Properties, Inc.’s Compensation Committee approved the 2020 Multi-Year Long-Term Incentive Program (the “2020 MYLTIP”) awards under Boston Properties, Inc.’s 2012 Plan to certain officers and employees of Boston Properties, Inc. Earned awards will range from zero to a maximum of 203,278 LTIP Units depending on Boston Properties, Inc.’s TSR relative to the FTSE Nareit Office Index, adjusted to include Vornado Realty Trust, with a target of approximately 101,638 LTIP Units and linear interpolation between zero and maximum. Under ASC 718, the 2020 MYLTIP awards have an aggregate value of approximately $13.7 million. On February 6, 2020, the measurement period for the Company’s 2017 MYLTIP awards ended and, based on Boston Properties, Inc.’s relative TSR performance, the final awards were determined to be 83.8% of target or an aggregate of approximately $17.6 million (after giving effect to employee separations). As a result, an aggregate of 270,942 2017 MYLTIP Units that had been previously granted were automatically forfeited. On February 20, 2020, the Company completed the sale of its New Dominion Technology Park located in Herndon, Virginia for a gross sale price of $256.0 million. New Dominion Technology Park is comprised of two Class A office properties aggregating approximately 493,000 net rentable square feet (See Note 6).