SEC Schedule, Article 12-28, Real Estate and Accumulated Depreciation (Details) - USD ($)		12 Months Ended
		Dec. 31, 2023		Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate and Accumulated Depreciation [Line Items]
Encumbrances	[1]	$ 4,166,379,000
Original Cost
Original Land		5,637,035,000
Original Building		15,478,086,000
Costs Capitalized Subsequent to Acquisition		6,306,350,000
Land and Improvements	[2]	5,953,798,000
Building and Improvements	[3]	20,223,332,000
Land held for development	[5]	697,061,000	[4]	$ 721,501,000
Development and Construction in Progress		547,280,000		406,574,000
Total		27,421,471,000		25,744,214,000	$ 24,108,220,000	$ 23,303,303,000
Accumulated Depreciation		6,841,404,000		6,260,992,000	5,848,183,000	5,501,637,000
Furniture, Fixtures and Equipment		53,716,000		50,310,000
Aggregate cost for tax purpose		25,200,000,000
Real Estate Aggregate Accumulated Depreciation For Tax Purposes		5,900,000,000
Debt Issuance Costs, Net		(33,600,000)
Right-of-use assets - finance leases		401,680,000	[6]	237,510,000
Operating Lease, Right-of-Use Asset	[6]	$ 324,298,000		167,351,000
Maximum [Member]
Original Cost
Real Estate and Accumulated Depreciation, Life Used for Depreciation		40 years
Furniture, fixtures, and equipment
Original Cost
Accumulated Depreciation Related to Furniture, Fixtures and Equipment		$ 40,324,000
Land and Land Improvements [Member]
Original Cost
Right-of-use assets - finance leases		378,276,000
Operating Lease, Right-of-Use Asset		324,298,000
Buildings and improvements
Original Cost
Right-of-use assets - finance leases		23,404,000
767Fifth Avenue (the General Motors Building) | Office and Life Sciences Building [Member]
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate and Accumulated Depreciation [Line Items]
Encumbrances		2,288,004,000
Original Cost
Original Land		1,796,252,000
Original Building		1,532,654,000
Costs Capitalized Subsequent to Acquisition		365,829,000
Land and Improvements		1,796,252,000
Building and Improvements		1,898,483,000
Total		3,694,735,000
Accumulated Depreciation		$ 507,660,000
Depreciable Lives (Years)	[7]	(1)
Prudential Center | Office and Life Sciences Building [Member]
Original Cost
Original Land		$ 92,077,000
Original Building		948,357,000
Costs Capitalized Subsequent to Acquisition		791,280,000
Land and Improvements		115,634,000
Building and Improvements		1,687,021,000
Development and Construction in Progress		29,059,000
Total		1,831,714,000
Accumulated Depreciation		$ 774,225,000
Depreciable Lives (Years)	[7]	(1)
Embarcadero Center | Office and Life Sciences Building [Member]
Original Cost
Original Land		$ 179,697,000
Original Building		847,410,000
Costs Capitalized Subsequent to Acquisition		524,483,000
Land and Improvements		195,986,000
Building and Improvements		1,355,604,000
Total		1,551,590,000
Accumulated Depreciation		$ 781,405,000
Depreciable Lives (Years)	[7]	(1)
399 Park Avenue | Office and Life Sciences Building [Member]
Original Cost
Original Land		$ 339,200,000
Original Building		700,358,000
Costs Capitalized Subsequent to Acquisition		408,846,000
Land and Improvements		354,107,000
Building and Improvements		1,094,297,000
Total		1,448,404,000
Accumulated Depreciation		$ 482,752,000
Depreciable Lives (Years)	[7]	(1)
601 Lexington Avenue | Office and Life Sciences Building [Member]
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate and Accumulated Depreciation [Line Items]
Encumbrances		$ 989,181,000
Original Cost
Original Land		241,600,000
Original Building		494,782,000
Costs Capitalized Subsequent to Acquisition		545,612,000
Land and Improvements		289,639,000
Building and Improvements		992,355,000
Total		1,281,994,000
Accumulated Depreciation		$ 372,795,000
Depreciable Lives (Years)	[7]	(1)
Salesforce Tower | Office and Life Sciences Building [Member]
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate and Accumulated Depreciation [Line Items]
Encumbrances		$ 0
Original Cost
Original Land		200,349,000
Original Building		946,205,000
Costs Capitalized Subsequent to Acquisition		7,623,000
Land and Improvements		200,349,000
Building and Improvements		953,828,000
Total		1,154,177,000
Accumulated Depreciation		$ 159,274,000
Depreciable Lives (Years)	[7]	(1)
200 Clarendon Street and Garage | Office and Life Sciences Building [Member]
Original Cost
Original Land		$ 219,543,000
Original Building		667,884,000
Costs Capitalized Subsequent to Acquisition		251,372,000
Land and Improvements		250,910,000
Building and Improvements		887,889,000
Total		1,138,799,000
Accumulated Depreciation		$ 338,529,000
Depreciable Lives (Years)	[7]	(1)
250 West 55th Street | Office and Life Sciences Building [Member]
Original Cost
Original Land		$ 285,263,000
Original Building		603,167,000
Costs Capitalized Subsequent to Acquisition		52,917,000
Land and Improvements		285,263,000
Building and Improvements		656,084,000
Total		941,347,000
Accumulated Depreciation		$ 198,081,000
Depreciable Lives (Years)	[7]	(1)
100 Federal Street | Office and Life Sciences Building [Member]
Original Cost
Original Land		$ 131,067,000
Original Building		435,954,000
Costs Capitalized Subsequent to Acquisition		127,199,000
Land and Improvements		131,067,000
Building and Improvements		563,153,000
Total		694,220,000
Accumulated Depreciation		$ 172,079,000
Depreciable Lives (Years)	[7]	(1)
Times Square Tower | Office and Life Sciences Building [Member]
Original Cost
Original Land		$ 165,413,000
Original Building		380,438,000
Costs Capitalized Subsequent to Acquisition		140,281,000
Land and Improvements		169,193,000
Building and Improvements		516,939,000
Total		686,132,000
Accumulated Depreciation		$ 256,942,000
Depreciable Lives (Years)	[7]	(1)
Madison Centre | Office and Life Sciences Building [Member]
Original Cost
Original Land		$ 104,641,000
Original Building		564,336,000
Costs Capitalized Subsequent to Acquisition		4,082,000
Land and Improvements		104,641,000
Building and Improvements		568,418,000
Total		673,059,000
Accumulated Depreciation		$ 35,516,000
Depreciable Lives (Years)	[7]	(1)
Carnegie Center | Office and Life Sciences Building [Member]
Original Cost
Original Land		$ 142,666,000
Original Building		316,856,000
Costs Capitalized Subsequent to Acquisition		177,545,000
Land and Improvements		94,243,000
Building and Improvements		484,024,000
Land held for development		58,800,000
Total		637,067,000
Accumulated Depreciation		$ 267,232,000
Depreciable Lives (Years)	[7]	(1)
Santa Monica Business Park [Member] | Office and Life Sciences Building [Member]
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate and Accumulated Depreciation [Line Items]
Encumbrances		$ 295,649,000
Original Cost
Original Land		46,360,000
Original Building		410,421,000
Costs Capitalized Subsequent to Acquisition		164,229,000
Land and Improvements		210,471,000
Building and Improvements		410,535,000
Land held for development		4,000
Total		621,010,000
Accumulated Depreciation		$ 865,000
Depreciable Lives (Years)	[7]	(1)
Reston Next | Office and Life Sciences Building [Member]
Original Cost
Original Land		$ 35,549,000
Original Building		525,277,000
Costs Capitalized Subsequent to Acquisition		0
Land and Improvements		2,901,000
Building and Improvements		557,925,000
Total		560,826,000
Accumulated Depreciation		$ 32,504,000
Depreciable Lives (Years)	[7]	(1)
125 Broadway | Office and Life Sciences Building [Member]
Original Cost
Original Land		$ 126,364,000
Original Building		433,662,000
Costs Capitalized Subsequent to Acquisition		4,000,000
Land and Improvements		126,364,000
Building and Improvements		437,662,000
Total		564,026,000
Accumulated Depreciation		$ 20,717,000
Depreciable Lives (Years)	[7]	(1)
Atlantic Wharf | Office and Life Sciences Building [Member]
Original Cost
Original Land		$ 63,988,000
Original Building		454,537,000
Costs Capitalized Subsequent to Acquisition		39,399,000
Land and Improvements		63,988,000
Building and Improvements		493,936,000
Total		557,924,000
Accumulated Depreciation		$ 180,686,000
Depreciable Lives (Years)	[7]	(1)
2100 Pennsylvania Avenue | Office and Life Sciences Building [Member]
Original Cost
Original Land		$ 185,203,000
Original Building		324,206,000
Costs Capitalized Subsequent to Acquisition		0
Land and Improvements		185,203,000
Building and Improvements		324,206,000
Total		509,409,000
Accumulated Depreciation		$ 20,768,000
Depreciable Lives (Years)	[7]	(1)
599 Lexington Avenue | Office and Life Sciences Building [Member]
Original Cost
Original Land		$ 81,040,000
Original Building		100,507,000
Costs Capitalized Subsequent to Acquisition		258,659,000
Land and Improvements		87,852,000
Building and Improvements		352,354,000
Total		440,206,000
Accumulated Depreciation		$ 197,429,000
Depreciable Lives (Years)	[7]	(1)
Fountain Square | Office and Life Sciences Building [Member]
Original Cost
Original Land		$ 56,853,000
Original Building		306,298,000
Costs Capitalized Subsequent to Acquisition		49,874,000
Land and Improvements		56,853,000
Building and Improvements		356,172,000
Total		413,025,000
Accumulated Depreciation		$ 111,481,000
Depreciable Lives (Years)	[7]	(1)
510 Madison Avenue | Office and Life Sciences Building [Member]
Original Cost
Original Land		$ 103,000,000
Original Building		253,665,000
Costs Capitalized Subsequent to Acquisition		33,100,000
Land and Improvements		103,000,000
Building and Improvements		286,765,000
Total		389,765,000
Accumulated Depreciation		$ 104,052,000
Depreciable Lives (Years)	[7]	(1)
325 Main Street | Office and Life Sciences Building [Member]
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate and Accumulated Depreciation [Line Items]
Encumbrances	[8]	$ 0
Original Cost
Original Land		21,596,000
Original Building		312,492,000
Costs Capitalized Subsequent to Acquisition		30,933,000
Land and Improvements		21,596,000
Building and Improvements		343,425,000
Total		365,021,000
Accumulated Depreciation		$ 14,833,000
Depreciable Lives (Years)	[7]	(1)
680 Folsom Street | Office and Life Sciences Building [Member]
Original Cost
Original Land		$ 72,545,000
Original Building		219,766,000
Costs Capitalized Subsequent to Acquisition		8,026,000
Land and Improvements		72,545,000
Building and Improvements		227,792,000
Total		300,337,000
Accumulated Depreciation		$ 80,964,000
Depreciable Lives (Years)	[7]	(1)
145 Broadway | Office and Life Sciences Building [Member]
Original Cost
Original Land		$ 121,000
Original Building		273,013,000
Costs Capitalized Subsequent to Acquisition		26,359,000
Land and Improvements		23,367,000
Building and Improvements		276,126,000
Total		299,493,000
Accumulated Depreciation		$ 35,390,000
Depreciable Lives (Years)	[7]	(1)
2200 Pennsylvania Avenue | Office and Life Sciences Building [Member]
Original Cost
Original Land		$ 0
Original Building		183,541,000
Costs Capitalized Subsequent to Acquisition		114,090,000
Land and Improvements		102,979,000
Building and Improvements		194,652,000
Total		297,631,000
Accumulated Depreciation		$ 77,357,000
Depreciable Lives (Years)	[7]	(1)
South of Market and Democracy Tower | Office and Life Sciences Building [Member]
Original Cost
Original Land		$ 13,603,000
Original Building		237,479,000
Costs Capitalized Subsequent to Acquisition		30,952,000
Land and Improvements		13,687,000
Building and Improvements		268,347,000
Total		282,034,000
Accumulated Depreciation		$ 108,973,000
Depreciable Lives (Years)	[7]	(1)
Bay Colony Corporate Center | Office and Life Sciences Building [Member]
Original Cost
Original Land		$ 18,789,000
Original Building		148,451,000
Costs Capitalized Subsequent to Acquisition		96,639,000
Land and Improvements		18,789,000
Building and Improvements		240,416,000
Land held for development		4,674,000
Total		263,879,000
Accumulated Depreciation		$ 113,123,000
Depreciable Lives (Years)	[7]	(1)
535 Mission Street | Office and Life Sciences Building [Member]
Original Cost
Original Land		$ 40,933,000
Original Building		148,378,000
Costs Capitalized Subsequent to Acquisition		4,629,000
Land and Improvements		40,934,000
Building and Improvements		153,006,000
Total		193,940,000
Accumulated Depreciation		$ 46,615,000
Depreciable Lives (Years)	[7]	(1)
Mountain View Research Park | Office and Life Sciences Building [Member]
Original Cost
Original Land		$ 95,066,000
Original Building		68,373,000
Costs Capitalized Subsequent to Acquisition		21,069,000
Land and Improvements		95,066,000
Building and Improvements		89,442,000
Total		184,508,000
Accumulated Depreciation		$ 33,095,000
Depreciable Lives (Years)	[7]	(1)
Reservoir Place | Office and Life Sciences Building [Member]
Original Cost
Original Land		$ 18,605,000
Original Building		104,124,000
Costs Capitalized Subsequent to Acquisition		56,160,000
Land and Improvements		20,108,000
Building and Improvements		156,954,000
Land held for development		1,827,000
Total		178,889,000
Accumulated Depreciation		$ 90,808,000
Depreciable Lives (Years)	[7]	(1)
140 Kendrick Street | Office and Life Sciences Building [Member]
Original Cost
Original Land		$ 18,095,000
Original Building		66,905,000
Costs Capitalized Subsequent to Acquisition		71,861,000
Land and Improvements		19,092,000
Building and Improvements		137,769,000
Total		156,861,000
Accumulated Depreciation		$ 46,586,000
Depreciable Lives (Years)	[7]	(1)
1330 Connecticut Avenue | Office and Life Sciences Building [Member]
Original Cost
Original Land		$ 25,982,000
Original Building		82,311,000
Costs Capitalized Subsequent to Acquisition		39,924,000
Land and Improvements		27,135,000
Building and Improvements		121,082,000
Total		148,217,000
Accumulated Depreciation		$ 53,332,000
Depreciable Lives (Years)	[7]	(1)
880 Winter Street [Member] | Office and Life Sciences Building [Member]
Original Cost
Original Land		$ 15,597,000
Original Building		37,255,000
Costs Capitalized Subsequent to Acquisition		95,265,000
Land and Improvements		15,597,000
Building and Improvements		132,520,000
Total		148,117,000
Accumulated Depreciation		$ 10,056,000
Depreciable Lives (Years)	[7]	(1)
One Freedom Square | Office and Life Sciences Building [Member]
Original Cost
Original Land		$ 9,929,000
Original Building		84,504,000
Costs Capitalized Subsequent to Acquisition		48,985,000
Land and Improvements		11,293,000
Building and Improvements		132,125,000
Total		143,418,000
Accumulated Depreciation		$ 68,406,000
Depreciable Lives (Years)	[7]	(1)
Two Freedom Square | Office and Life Sciences Building [Member]
Original Cost
Original Land		$ 13,930,000
Original Building		77,739,000
Costs Capitalized Subsequent to Acquisition		45,068,000
Land and Improvements		15,420,000
Building and Improvements		121,317,000
Total		136,737,000
Accumulated Depreciation		$ 44,662,000
Depreciable Lives (Years)	[7]	(1)
Kingstowne Towne Center | Office and Life Sciences Building [Member]
Original Cost
Original Land		$ 18,021,000
Original Building		109,038,000
Costs Capitalized Subsequent to Acquisition		4,665,000
Land and Improvements		18,062,000
Building and Improvements		113,662,000
Total		131,724,000
Accumulated Depreciation		$ 54,480,000
Depreciable Lives (Years)	[7]	(1)
One and Two Reston Overlook | Office and Life Sciences Building [Member]
Original Cost
Original Land		$ 16,456,000
Original Building		66,192,000
Costs Capitalized Subsequent to Acquisition		45,224,000
Land and Improvements		16,179,000
Building and Improvements		111,693,000
Total		127,872,000
Accumulated Depreciation		$ 61,572,000
Depreciable Lives (Years)	[7]	(1)
Shady Grove Innovation District [Member] | Office and Life Sciences Building [Member]
Original Cost
Original Land		$ 52,030,000
Original Building		64,212,000
Costs Capitalized Subsequent to Acquisition		10,676,000
Land and Improvements		26,834,000
Building and Improvements		34,954,000
Land held for development		65,130,000
Total		126,918,000
Accumulated Depreciation		$ 4,701,000
Depreciable Lives (Years)	[7]	(1)
Weston Corporate Center | Office and Life Sciences Building [Member]
Original Cost
Original Land		$ 25,753,000
Original Building		92,312,000
Costs Capitalized Subsequent to Acquisition		1,038,000
Land and Improvements		25,854,000
Building and Improvements		93,249,000
Total		119,103,000
Accumulated Depreciation		$ 41,485,000
Depreciable Lives (Years)	[7]	(1)
355 Main Street | Office and Life Sciences Building [Member]
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate and Accumulated Depreciation [Line Items]
Encumbrances		$ 593,545,000
Original Cost
Original Land		18,863,000
Original Building		53,346,000
Costs Capitalized Subsequent to Acquisition		41,772,000
Land and Improvements		21,173,000
Building and Improvements		92,808,000
Total		113,981,000
Accumulated Depreciation		$ 36,957,000
Depreciable Lives (Years)	[7]	(1)
17Fifty Presidents Street | Office and Life Sciences Building [Member]
Original Cost
Original Land		$ 0
Original Building		113,362,000
Costs Capitalized Subsequent to Acquisition		162,000
Land and Improvements		0
Building and Improvements		113,524,000
Total		113,524,000
Accumulated Depreciation		$ 16,624,000
Depreciable Lives (Years)	[7]	(1)
200 West Street | Office and Life Sciences Building [Member]
Original Cost
Original Land		$ 16,148,000
Original Building		24,983,000
Costs Capitalized Subsequent to Acquisition		71,199,000
Land and Improvements		16,813,000
Building and Improvements		95,160,000
Land held for development		357,000
Total		112,330,000
Accumulated Depreciation		$ 28,192,000
Depreciable Lives (Years)	[7]	(1)
Discovery Square | Office and Life Sciences Building [Member]
Original Cost
Original Land		$ 11,198,000
Original Building		71,782,000
Costs Capitalized Subsequent to Acquisition		21,744,000
Land and Improvements		12,533,000
Building and Improvements		92,191,000
Total		104,724,000
Accumulated Depreciation		$ 57,015,000
Depreciable Lives (Years)	[7]	(1)
10 CityPoint | Office and Life Sciences Building [Member]
Original Cost
Original Land		$ 1,953,000
Original Building		85,752,000
Costs Capitalized Subsequent to Acquisition		7,571,000
Land and Improvements		2,288,000
Building and Improvements		92,988,000
Total		95,276,000
Accumulated Depreciation		$ 24,003,000
Depreciable Lives (Years)	[7]	(1)
90 Broadway | Office and Life Sciences Building [Member]
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate and Accumulated Depreciation [Line Items]
Encumbrances	[8]	$ 0
Original Cost
Original Land		19,104,000
Original Building		52,078,000
Costs Capitalized Subsequent to Acquisition		22,742,000
Land and Improvements		20,785,000
Building and Improvements		73,139,000
Total		93,924,000
Accumulated Depreciation		$ 31,538,000
Depreciable Lives (Years)	[7]	(1)
Waltham Weston Corporate Center | Office and Life Sciences Building [Member]
Original Cost
Original Land		$ 10,385,000
Original Building		60,694,000
Costs Capitalized Subsequent to Acquisition		20,705,000
Land and Improvements		11,097,000
Building and Improvements		80,687,000
Total		91,784,000
Accumulated Depreciation		$ 45,601,000
Depreciable Lives (Years)	[7]	(1)
153 & 211 Second Avenue [Member] | Office and Life Sciences Building [Member]
Original Cost
Original Land		$ 33,233,000
Original Building		55,940,000
Costs Capitalized Subsequent to Acquisition		718,000
Land and Improvements		33,233,000
Building and Improvements		55,940,000
Land held for development		718,000
Total		89,891,000
Accumulated Depreciation		$ 6,186,000
Depreciable Lives (Years)	[7]	(1)
230 CityPoint | Office and Life Sciences Building [Member]
Original Cost
Original Land		$ 13,189,000
Original Building		49,823,000
Costs Capitalized Subsequent to Acquisition		24,297,000
Land and Improvements		13,807,000
Building and Improvements		73,502,000
Total		87,309,000
Accumulated Depreciation		$ 40,959,000
Depreciable Lives (Years)	[7]	(1)
20 Citypoint | Office and Life Sciences Building [Member]
Original Cost
Original Land		$ 4,887,000
Original Building		72,764,000
Costs Capitalized Subsequent to Acquisition		7,072,000
Land and Improvements		4,887,000
Building and Improvements		79,836,000
Total		84,723,000
Accumulated Depreciation		$ 13,031,000
Depreciable Lives (Years)	[7]	(1)
Sumner Square | Office and Life Sciences Building [Member]
Original Cost
Original Land		$ 624,000
Original Building		28,745,000
Costs Capitalized Subsequent to Acquisition		51,253,000
Land and Improvements		27,837,000
Building and Improvements		52,785,000
Total		80,622,000
Accumulated Depreciation		$ 32,911,000
Depreciable Lives (Years)	[7]	(1)
77 CityPoint | Office and Life Sciences Building [Member]
Original Cost
Original Land		$ 13,847,000
Original Building		60,383,000
Costs Capitalized Subsequent to Acquisition		1,506,000
Land and Improvements		14,023,000
Building and Improvements		61,713,000
Total		75,736,000
Accumulated Depreciation		$ 26,943,000
Depreciable Lives (Years)	[7]	(1)
2440 West El Camino Real | Office and Life Sciences Building [Member]
Original Cost
Original Land		$ 16,741,000
Original Building		51,285,000
Costs Capitalized Subsequent to Acquisition		6,565,000
Land and Improvements		16,741,000
Building and Improvements		57,850,000
Total		74,591,000
Accumulated Depreciation		$ 21,469,000
Depreciable Lives (Years)	[7]	(1)
Wisconsin Place | Office and Life Sciences Building [Member]
Original Cost
Original Land		$ 0
Original Building		53,349,000
Costs Capitalized Subsequent to Acquisition		13,834,000
Land and Improvements		0
Building and Improvements		67,183,000
Total		67,183,000
Accumulated Depreciation		$ 28,960,000
Depreciable Lives (Years)	[7]	(1)
Reston Corporate Center | Office and Life Sciences Building [Member]
Original Cost
Original Land		$ 9,135,000
Original Building		50,857,000
Costs Capitalized Subsequent to Acquisition		4,489,000
Land and Improvements		10,148,000
Building and Improvements		54,333,000
Total		64,481,000
Accumulated Depreciation		$ 34,194,000
Depreciable Lives (Years)	[7]	(1)
255 Main Street | Office and Life Sciences Building [Member]
Original Cost
Original Land		$ 134,000
Original Building		25,110,000
Costs Capitalized Subsequent to Acquisition		33,330,000
Land and Improvements		548,000
Building and Improvements		58,026,000
Total		58,574,000
Accumulated Depreciation		$ 43,927,000
Depreciable Lives (Years)	[7]	(1)
University Place | Office and Life Sciences Building [Member]
Original Cost
Original Land		$ 0
Original Building		37,091,000
Costs Capitalized Subsequent to Acquisition		15,768,000
Land and Improvements		4,807,000
Building and Improvements		48,052,000
Total		52,859,000
Accumulated Depreciation		$ 37,130,000
Depreciable Lives (Years)	[7]	(1)
890 Winter Street | Office and Life Sciences Building [Member]
Original Cost
Original Land		$ 13,913,000
Original Building		28,557,000
Costs Capitalized Subsequent to Acquisition		8,507,000
Land and Improvements		13,913,000
Building and Improvements		37,064,000
Total		50,977,000
Accumulated Depreciation		$ 7,296,000
Depreciable Lives (Years)	[7]	(1)
Capital Gallery | Office and Life Sciences Building [Member]
Original Cost
Original Land		$ 4,725,000
Original Building		29,565,000
Costs Capitalized Subsequent to Acquisition		10,361,000
Land and Improvements		8,662,000
Building and Improvements		35,989,000
Total		44,651,000
Accumulated Depreciation		$ 23,764,000
Depreciable Lives (Years)	[7]	(1)
North First Business Park | Office and Life Sciences Building [Member]
Original Cost
Original Land		$ 23,398,000
Original Building		13,069,000
Costs Capitalized Subsequent to Acquisition		5,258,000
Land and Improvements		23,378,000
Building and Improvements		18,347,000
Total		41,725,000
Accumulated Depreciation		$ 17,354,000
Depreciable Lives (Years)	[7]	(1)
150 Broadway | Office and Life Sciences Building [Member]
Original Cost
Original Land		$ 850,000
Original Building		25,042,000
Costs Capitalized Subsequent to Acquisition		15,749,000
Land and Improvements		1,323,000
Building and Improvements		40,318,000
Total		41,641,000
Accumulated Depreciation		$ 18,506,000
Depreciable Lives (Years)	[7]	(1)
105 Broadway | Office and Life Sciences Building [Member]
Original Cost
Original Land		$ 1,299,000
Original Building		12,943,000
Costs Capitalized Subsequent to Acquisition		12,723,000
Land and Improvements		2,395,000
Building and Improvements		24,570,000
Total		26,965,000
Accumulated Depreciation		$ 16,847,000
Depreciable Lives (Years)	[7]	(1)
Lexington Office Park | Office and Life Sciences Building [Member]
Original Cost
Original Land		$ 998,000
Original Building		1,426,000
Costs Capitalized Subsequent to Acquisition		19,924,000
Land and Improvements		1,263,000
Building and Improvements		19,470,000
Land held for development		1,615,000
Total		22,348,000
Accumulated Depreciation		$ 17,200,000
Depreciable Lives (Years)	[7]	(1)
The Point | Office and Life Sciences Building [Member]
Original Cost
Original Land		$ 6,395,000
Original Building		10,040,000
Costs Capitalized Subsequent to Acquisition		546,000
Land and Improvements		6,492,000
Building and Improvements		10,489,000
Total		16,981,000
Accumulated Depreciation		$ 2,638,000
Depreciable Lives (Years)	[7]	(1)
690 Folsom Street | Office and Life Sciences Building [Member]
Original Cost
Original Land		$ 3,219,000
Original Building		11,038,000
Costs Capitalized Subsequent to Acquisition		1,877,000
Land and Improvements		3,219,000
Building and Improvements		12,915,000
Total		16,134,000
Accumulated Depreciation		$ 4,280,000
Depreciable Lives (Years)	[7]	(1)
33 Hayden Avenue | Office and Life Sciences Building [Member]
Original Cost
Original Land		$ 266,000
Original Building		3,234,000
Costs Capitalized Subsequent to Acquisition		11,502,000
Land and Improvements		425,000
Building and Improvements		14,577,000
Total		15,002,000
Accumulated Depreciation		$ 9,090,000
Depreciable Lives (Years)	[7]	(1)
The Avant Retail | Office and Life Sciences Building [Member]
Original Cost
Original Land		$ 1,499,000
Original Building		6,647,000
Costs Capitalized Subsequent to Acquisition		2,577,000
Land and Improvements		1,499,000
Building and Improvements		9,224,000
Total		10,723,000
Accumulated Depreciation		$ 3,587,000
Depreciable Lives (Years)	[7]	(1)
92-100 Hayden Avenue | Office and Life Sciences Building [Member]
Original Cost
Original Land		$ 594,000
Original Building		6,748,000
Costs Capitalized Subsequent to Acquisition		1,922,000
Land and Improvements		778,000
Building and Improvements		8,486,000
Total		9,264,000
Accumulated Depreciation		$ 7,388,000
Depreciable Lives (Years)	[7]	(1)
32 Hartwell Avenue | Office and Life Sciences Building [Member]
Original Cost
Original Land		$ 168,000
Original Building		1,943,000
Costs Capitalized Subsequent to Acquisition		6,403,000
Land and Improvements		314,000
Building and Improvements		8,200,000
Total		8,514,000
Accumulated Depreciation		$ 2,931,000
Depreciable Lives (Years)	[7]	(1)
250 Binney Street | Office and Life Sciences Building [Member]
Original Cost
Original Land		$ 110,000
Original Building		4,483,000
Costs Capitalized Subsequent to Acquisition		3,593,000
Land and Improvements		273,000
Building and Improvements		7,913,000
Total		8,186,000
Accumulated Depreciation		$ 7,244,000
Depreciable Lives (Years)	[7]	(1)
453 Ravendale Drive | Office and Life Sciences Building [Member]
Original Cost
Original Land		$ 5,477,000
Original Building		1,090,000
Costs Capitalized Subsequent to Acquisition		1,286,000
Land and Improvements		5,477,000
Building and Improvements		2,376,000
Total		7,853,000
Accumulated Depreciation		$ 1,086,000
Depreciable Lives (Years)	[7]	(1)
17 Hartwell Avenue | Office and Life Sciences Building [Member]
Original Cost
Original Land		$ 26,000
Original Building		150,000
Costs Capitalized Subsequent to Acquisition		6,064,000
Land and Improvements		65,000
Building and Improvements		6,175,000
Total		6,240,000
Accumulated Depreciation		$ 3,755,000
Depreciable Lives (Years)	[7]	(1)
The Skylyne | Residential Building
Original Cost
Original Land		$ 28,962,000
Original Building		239,077,000
Costs Capitalized Subsequent to Acquisition		1,792,000
Land and Improvements		28,962,000
Building and Improvements		240,869,000
Total		269,831,000
Accumulated Depreciation		$ 20,181,000
Depreciable Lives (Years)	[7]	(1)
Signature at Reston | Residential Building
Original Cost
Original Land		$ 27,076,000
Original Building		190,580,000
Costs Capitalized Subsequent to Acquisition		3,817,000
Land and Improvements		27,076,000
Building and Improvements		194,397,000
Total		221,473,000
Accumulated Depreciation		$ 27,876,000
Depreciable Lives (Years)	[7]	(1)
Proto Kendall Square | Residential Building
Original Cost
Original Land		$ 9,243,000
Original Building		127,248,000
Costs Capitalized Subsequent to Acquisition		3,336,000
Land and Improvements		9,245,000
Building and Improvements		130,582,000
Total		139,827,000
Accumulated Depreciation		$ 17,820,000
Depreciable Lives (Years)	[7]	(1)
The Lofts at Atlantic Wharf | Residential Building
Original Cost
Original Land		$ 3,529,000
Original Building		54,891,000
Costs Capitalized Subsequent to Acquisition		2,509,000
Land and Improvements		3,529,000
Building and Improvements		57,400,000
Total		60,929,000
Accumulated Depreciation		$ 18,631,000
Depreciable Lives (Years)	[7]	(1)
Boston Cambridge Marriott | Hotel [Member]
Original Cost
Original Land		$ 478,000
Original Building		37,918,000
Costs Capitalized Subsequent to Acquisition		32,131,000
Land and Improvements		1,201,000
Building and Improvements		68,697,000
Land held for development		629,000
Total		70,527,000
Accumulated Depreciation		$ 53,282,000
Depreciable Lives (Years)	[7]	(1)
Kendall Center Green Garage | Garage
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate and Accumulated Depreciation [Line Items]
Encumbrances	[8]	$ 0
Original Cost
Original Land		0
Original Building		35,035,000
Costs Capitalized Subsequent to Acquisition		7,335,000
Land and Improvements		103,000
Building and Improvements		42,267,000
Total		42,370,000
Accumulated Depreciation		$ 18,414,000
Depreciable Lives (Years)	[7]	(1)
Kendall Center Yellow Garage | Garage
Original Cost
Original Land		$ 1,256,000
Original Building		15,697,000
Costs Capitalized Subsequent to Acquisition		1,743,000
Land and Improvements		1,434,000
Building and Improvements		17,262,000
Total		18,696,000
Accumulated Depreciation		$ 7,857,000
Depreciable Lives (Years)	[7]	(1)
290 Binney | Development
Original Cost
Original Land		$ 0
Original Building		0
Costs Capitalized Subsequent to Acquisition		243,099,000
Land and Improvements		1,054,000
Development and Construction in Progress		242,045,000
Total		$ 243,099,000
Depreciable Lives (Years)		N/A
180 CityPoint [Member] | Development
Original Cost
Original Land		$ 0
Original Building		0
Costs Capitalized Subsequent to Acquisition		214,754,000
Land and Improvements		10,908,000
Building and Improvements		108,970,000
Development and Construction in Progress		94,876,000
Total		214,754,000
Accumulated Depreciation		$ 541,000
Depreciable Lives (Years)		N/A
300 Binney Street | Development
Original Cost
Original Land		$ 18,080,000
Original Building		51,262,000
Costs Capitalized Subsequent to Acquisition		38,454,000
Land and Improvements		18,080,000
Building and Improvements		27,805,000
Development and Construction in Progress		61,911,000
Total		107,796,000
Accumulated Depreciation		$ 6,719,000
Depreciable Lives (Years)		N/A
103 CityPoint | Development
Original Cost
Original Land		$ 0
Original Building		0
Costs Capitalized Subsequent to Acquisition		88,190,000
Land and Improvements		4,672,000
Building and Improvements		3,025,000
Land held for development		8,672,000
Development and Construction in Progress		71,821,000
Total		88,190,000
Accumulated Depreciation		$ 18,000
Depreciable Lives (Years)		N/A
Reston Next Office Phase II | Development
Original Cost
Original Land		$ 0
Original Building		0
Costs Capitalized Subsequent to Acquisition		39,201,000
Development and Construction in Progress		39,201,000
Total		$ 39,201,000
Depreciable Lives (Years)		N/A
Reston Next Retail | Development
Original Cost
Original Land		$ 0
Original Building		0
Costs Capitalized Subsequent to Acquisition		8,367,000
Development and Construction in Progress		8,367,000
Total		$ 8,367,000
Depreciable Lives (Years)		N/A
343 Madison Avenue | Land
Original Cost
Original Land		$ 0
Original Building		0
Costs Capitalized Subsequent to Acquisition		206,052,000
Land and Improvements		158,885,000
Land held for development		47,167,000
Total		$ 206,052,000
Depreciable Lives (Years)		N/A
777 Harrison Street | Land
Original Cost
Original Land		$ 144,647,000
Original Building		0
Costs Capitalized Subsequent to Acquisition		28,334,000
Building and Improvements		47,000
Land held for development		172,934,000
Total		172,981,000
Accumulated Depreciation		$ 29,000
Depreciable Lives (Years)		N/A
Back Bay Station Master Plan | Land
Original Cost
Original Land		$ 0
Original Building		0
Costs Capitalized Subsequent to Acquisition		78,150,000
Land held for development		78,150,000
Total		$ 78,150,000
Depreciable Lives (Years)		N/A
3625 - 3635 Peterson Way | Land
Original Cost
Original Land		$ 63,206,000
Original Building		0
Costs Capitalized Subsequent to Acquisition		5,173,000
Land held for development		68,379,000
Total		$ 68,379,000
Depreciable Lives (Years)		N/A
Kendall Center Master Plan | Land
Original Cost
Original Land		$ 0
Original Building		0
Costs Capitalized Subsequent to Acquisition		48,857,000
Land held for development		48,857,000
Total		$ 48,857,000
Depreciable Lives (Years)		N/A
North First Master Plan | Land
Original Cost
Original Land		$ 35,004,000
Original Building		0
Costs Capitalized Subsequent to Acquisition		4,068,000
Land held for development		39,072,000
Total		$ 39,072,000
Depreciable Lives (Years)		N/A
Plaza at Almaden | Land
Original Cost
Original Land		$ 0
Original Building		0
Costs Capitalized Subsequent to Acquisition		38,163,000
Land held for development		38,163,000
Total		$ 38,163,000
Depreciable Lives (Years)		N/A
CityPoint South Master Plan | Land
Original Cost
Original Land		$ 0
Original Building		0
Costs Capitalized Subsequent to Acquisition		25,594,000
Land held for development		25,594,000
Total		$ 25,594,000
Depreciable Lives (Years)		N/A
Springfield Metro Center | Land
Original Cost
Original Land		$ 0
Original Building		0
Costs Capitalized Subsequent to Acquisition		19,896,000
Land held for development		19,896,000
Total		$ 19,896,000
Depreciable Lives (Years)		N/A
Reston Gateway Master Plan | Land
Original Cost
Original Land		$ 0
Original Building		0
Costs Capitalized Subsequent to Acquisition		13,908,000
Land held for development		13,908,000
Total		$ 13,908,000
Depreciable Lives (Years)		N/A
Weston Quarry | Land
Original Cost
Original Land		$ 0
Original Building		0
Costs Capitalized Subsequent to Acquisition		1,249,000
Land held for development		1,249,000
Total		$ 1,249,000
Depreciable Lives (Years)		N/A
Broad Run Business Park | Land
Original Cost
Original Land		$ 0
Original Building		0
Costs Capitalized Subsequent to Acquisition		1,186,000
Land held for development		1,186,000
Total		$ 1,186,000
Depreciable Lives (Years)		N/A
Reston Overlook Master Plan | Land
Original Cost
Original Land		$ 0
Original Building		0
Costs Capitalized Subsequent to Acquisition		80,000
Land held for development		80,000
Total		$ 80,000
Depreciable Lives (Years)		N/A
Boston Properties Limited Partnership
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate and Accumulated Depreciation [Line Items]
Encumbrances	[9]	$ 4,166,379,000
Original Cost
Original Land		5,637,035,000
Original Building		15,478,086,000
Costs Capitalized Subsequent to Acquisition		5,940,085,000
Land and Improvements	[10]	5,859,089,000
Building and Improvements	[11]	19,951,776,000
Land held for development	[5]	697,061,000	[12]	721,501,000
Development and Construction in Progress		547,280,000		406,574,000
Total		27,055,206,000		25,376,700,000	23,734,833,000	22,926,494,000
Accumulated Depreciation		6,718,037,000		6,143,384,000	$ 5,736,240,000	$ 5,396,111,000
Furniture, Fixtures and Equipment		53,716,000		50,310,000
Aggregate cost for tax purpose		28,200,000,000
Real Estate Aggregate Accumulated Depreciation For Tax Purposes		6,600,000,000
Debt Issuance Costs, Net		(33,600,000)
Right-of-use assets - finance leases		401,680,000	[6]	237,510,000
Operating Lease, Right-of-Use Asset	[6]	$ 324,298,000		$ 167,351,000
Boston Properties Limited Partnership | Maximum [Member]
Original Cost
Real Estate and Accumulated Depreciation, Life Used for Depreciation		40 years
Boston Properties Limited Partnership | Furniture, fixtures, and equipment
Original Cost
Accumulated Depreciation Related to Furniture, Fixtures and Equipment		$ 40,324,000
Boston Properties Limited Partnership | Land and Land Improvements [Member]
Original Cost
Right-of-use assets - finance leases		378,276,000
Operating Lease, Right-of-Use Asset		324,298,000
Boston Properties Limited Partnership | Buildings and improvements
Original Cost
Right-of-use assets - finance leases		23,404,000
Boston Properties Limited Partnership | 767Fifth Avenue (the General Motors Building) | Office and Life Sciences Building [Member]
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate and Accumulated Depreciation [Line Items]
Encumbrances		2,288,004,000
Original Cost
Original Land		1,796,252,000
Original Building		1,532,654,000
Costs Capitalized Subsequent to Acquisition		365,829,000
Land and Improvements		1,796,252,000
Building and Improvements		1,898,483,000
Total		3,694,735,000
Accumulated Depreciation		$ 507,660,000
Depreciable Lives (Years)	[13]	(1)
Boston Properties Limited Partnership | Prudential Center | Office and Life Sciences Building [Member]
Original Cost
Original Land		$ 92,077,000
Original Building		948,357,000
Costs Capitalized Subsequent to Acquisition		732,224,000
Land and Improvements		100,535,000
Building and Improvements		1,643,064,000
Development and Construction in Progress		29,059,000
Total		1,772,658,000
Accumulated Depreciation		$ 754,356,000
Depreciable Lives (Years)	[13]	(1)
Boston Properties Limited Partnership | Embarcadero Center | Office and Life Sciences Building [Member]
Original Cost
Original Land		$ 179,697,000
Original Building		847,410,000
Costs Capitalized Subsequent to Acquisition		462,102,000
Land and Improvements		180,419,000
Building and Improvements		1,308,790,000
Total		1,489,209,000
Accumulated Depreciation		$ 760,144,000
Depreciable Lives (Years)	[13]	(1)
Boston Properties Limited Partnership | 399 Park Avenue | Office and Life Sciences Building [Member]
Original Cost
Original Land		$ 339,200,000
Original Building		700,358,000
Costs Capitalized Subsequent to Acquisition		349,238,000
Land and Improvements		339,200,000
Building and Improvements		1,049,596,000
Total		1,388,796,000
Accumulated Depreciation		$ 462,543,000
Depreciable Lives (Years)	[13]	(1)
Boston Properties Limited Partnership | 601 Lexington Avenue | Office and Life Sciences Building [Member]
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate and Accumulated Depreciation [Line Items]
Encumbrances		$ 989,181,000
Original Cost
Original Land		241,600,000
Original Building		494,782,000
Costs Capitalized Subsequent to Acquisition		508,526,000
Land and Improvements		279,281,000
Building and Improvements		965,627,000
Total		1,244,908,000
Accumulated Depreciation		$ 360,656,000
Depreciable Lives (Years)	[13]	(1)
Boston Properties Limited Partnership | Salesforce Tower | Office and Life Sciences Building [Member]
Original Cost
Original Land		$ 200,349,000
Original Building		946,205,000
Costs Capitalized Subsequent to Acquisition		7,623,000
Land and Improvements		200,349,000
Building and Improvements		953,828,000
Total		1,154,177,000
Accumulated Depreciation		$ 159,274,000
Depreciable Lives (Years)	[13]	(1)
Boston Properties Limited Partnership | 200 Clarendon Street and Garage | Office and Life Sciences Building [Member]
Original Cost
Original Land		$ 219,543,000
Original Building		667,884,000
Costs Capitalized Subsequent to Acquisition		251,372,000
Land and Improvements		250,910,000
Building and Improvements		887,889,000
Total		1,138,799,000
Accumulated Depreciation		$ 338,529,000
Depreciable Lives (Years)	[13]	(1)
Boston Properties Limited Partnership | 250 West 55th Street | Office and Life Sciences Building [Member]
Original Cost
Original Land		$ 285,263,000
Original Building		603,167,000
Costs Capitalized Subsequent to Acquisition		52,917,000
Land and Improvements		285,263,000
Building and Improvements		656,084,000
Total		941,347,000
Accumulated Depreciation		$ 198,081,000
Depreciable Lives (Years)	[13]	(1)
Boston Properties Limited Partnership | 100 Federal Street | Office and Life Sciences Building [Member]
Original Cost
Original Land		$ 131,067,000
Original Building		435,954,000
Costs Capitalized Subsequent to Acquisition		127,199,000
Land and Improvements		131,067,000
Building and Improvements		563,153,000
Total		694,220,000
Accumulated Depreciation		$ 172,079,000
Depreciable Lives (Years)	[13]	(1)
Boston Properties Limited Partnership | Times Square Tower | Office and Life Sciences Building [Member]
Original Cost
Original Land		$ 165,413,000
Original Building		380,438,000
Costs Capitalized Subsequent to Acquisition		102,302,000
Land and Improvements		159,694,000
Building and Improvements		488,459,000
Total		648,153,000
Accumulated Depreciation		$ 244,067,000
Depreciable Lives (Years)	[13]	(1)
Boston Properties Limited Partnership | Madison Centre | Office and Life Sciences Building [Member]
Original Cost
Original Land		$ 104,641,000
Original Building		564,336,000
Costs Capitalized Subsequent to Acquisition		4,082,000
Land and Improvements		104,641,000
Building and Improvements		568,418,000
Total		673,059,000
Accumulated Depreciation		$ 35,516,000
Depreciable Lives (Years)	[13]	(1)
Boston Properties Limited Partnership | Carnegie Center | Office and Life Sciences Building [Member]
Original Cost
Original Land		$ 142,666,000
Original Building		316,856,000
Costs Capitalized Subsequent to Acquisition		162,582,000
Land and Improvements		90,501,000
Building and Improvements		472,803,000
Land held for development		58,800,000
Total		622,104,000
Accumulated Depreciation		$ 262,096,000
Depreciable Lives (Years)	[13]	(1)
Boston Properties Limited Partnership | Santa Monica Business Park [Member] | Office and Life Sciences Building [Member]
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate and Accumulated Depreciation [Line Items]
Encumbrances		$ 295,649,000
Original Cost
Original Land		46,360,000
Original Building		410,421,000
Costs Capitalized Subsequent to Acquisition		164,229,000
Land and Improvements		210,471,000
Building and Improvements		410,535,000
Land held for development		4,000
Total		621,010,000
Accumulated Depreciation		$ 865,000
Depreciable Lives (Years)	[13]	(1)
Boston Properties Limited Partnership | Reston Next | Office and Life Sciences Building [Member]
Original Cost
Original Land		$ 35,549,000
Original Building		525,277,000
Costs Capitalized Subsequent to Acquisition		0
Land and Improvements		2,901,000
Building and Improvements		557,925,000
Total		560,826,000
Accumulated Depreciation		$ 32,504,000
Depreciable Lives (Years)	[13]	(1)
Boston Properties Limited Partnership | 125 Broadway | Office and Life Sciences Building [Member]
Original Cost
Original Land		$ 126,364,000
Original Building		433,662,000
Costs Capitalized Subsequent to Acquisition		4,000,000
Land and Improvements		126,364,000
Building and Improvements		437,662,000
Total		564,026,000
Accumulated Depreciation		$ 20,717,000
Depreciable Lives (Years)	[13]	(1)
Boston Properties Limited Partnership | Atlantic Wharf | Office and Life Sciences Building [Member]
Original Cost
Original Land		$ 63,988,000
Original Building		454,537,000
Costs Capitalized Subsequent to Acquisition		39,399,000
Land and Improvements		63,988,000
Building and Improvements		493,936,000
Total		557,924,000
Accumulated Depreciation		$ 180,686,000
Depreciable Lives (Years)	[13]	(1)
Boston Properties Limited Partnership | 2100 Pennsylvania Avenue | Office and Life Sciences Building [Member]
Original Cost
Original Land		$ 185,203,000
Original Building		324,206,000
Costs Capitalized Subsequent to Acquisition		0
Land and Improvements		185,203,000
Building and Improvements		324,206,000
Total		509,409,000
Accumulated Depreciation		$ 20,768,000
Depreciable Lives (Years)	[13]	(1)
Boston Properties Limited Partnership | 599 Lexington Avenue | Office and Life Sciences Building [Member]
Original Cost
Original Land		$ 81,040,000
Original Building		100,507,000
Costs Capitalized Subsequent to Acquisition		231,417,000
Land and Improvements		81,040,000
Building and Improvements		331,924,000
Total		412,964,000
Accumulated Depreciation		$ 188,193,000
Depreciable Lives (Years)	[13]	(1)
Boston Properties Limited Partnership | Fountain Square | Office and Life Sciences Building [Member]
Original Cost
Original Land		$ 56,853,000
Original Building		306,298,000
Costs Capitalized Subsequent to Acquisition		49,874,000
Land and Improvements		56,853,000
Building and Improvements		356,172,000
Total		413,025,000
Accumulated Depreciation		$ 111,481,000
Depreciable Lives (Years)	[13]	(1)
Boston Properties Limited Partnership | 510 Madison Avenue | Office and Life Sciences Building [Member]
Original Cost
Original Land		$ 103,000,000
Original Building		253,665,000
Costs Capitalized Subsequent to Acquisition		33,100,000
Land and Improvements		103,000,000
Building and Improvements		286,765,000
Total		389,765,000
Accumulated Depreciation		$ 104,052,000
Depreciable Lives (Years)	[13]	(1)
Boston Properties Limited Partnership | 325 Main Street | Office and Life Sciences Building [Member]
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate and Accumulated Depreciation [Line Items]
Encumbrances	[14]	$ 0
Original Cost
Original Land		21,596,000
Original Building		312,492,000
Costs Capitalized Subsequent to Acquisition		30,740,000
Land and Improvements		21,403,000
Building and Improvements		343,425,000
Total		364,828,000
Accumulated Depreciation		$ 14,833,000
Depreciable Lives (Years)	[13]	(1)
Boston Properties Limited Partnership | 680 Folsom Street | Office and Life Sciences Building [Member]
Original Cost
Original Land		$ 72,545,000
Original Building		219,766,000
Costs Capitalized Subsequent to Acquisition		8,026,000
Land and Improvements		72,545,000
Building and Improvements		227,792,000
Total		300,337,000
Accumulated Depreciation		$ 80,964,000
Depreciable Lives (Years)	[13]	(1)
Boston Properties Limited Partnership | 145 Broadway | Office and Life Sciences Building [Member]
Original Cost
Original Land		$ 121,000
Original Building		273,013,000
Costs Capitalized Subsequent to Acquisition		26,156,000
Land and Improvements		23,164,000
Building and Improvements		276,126,000
Total		299,290,000
Accumulated Depreciation		$ 35,390,000
Depreciable Lives (Years)	[13]	(1)
Boston Properties Limited Partnership | 2200 Pennsylvania Avenue | Office and Life Sciences Building [Member]
Original Cost
Original Land		$ 0
Original Building		183,541,000
Costs Capitalized Subsequent to Acquisition		114,090,000
Land and Improvements		102,979,000
Building and Improvements		194,652,000
Total		297,631,000
Accumulated Depreciation		$ 77,357,000
Depreciable Lives (Years)	[13]	(1)
Boston Properties Limited Partnership | South of Market and Democracy Tower | Office and Life Sciences Building [Member]
Original Cost
Original Land		$ 13,603,000
Original Building		237,479,000
Costs Capitalized Subsequent to Acquisition		30,616,000
Land and Improvements		13,603,000
Building and Improvements		268,095,000
Total		281,698,000
Accumulated Depreciation		$ 108,875,000
Depreciable Lives (Years)	[13]	(1)
Boston Properties Limited Partnership | Bay Colony Corporate Center | Office and Life Sciences Building [Member]
Original Cost
Original Land		$ 18,789,000
Original Building		148,451,000
Costs Capitalized Subsequent to Acquisition		96,639,000
Land and Improvements		18,789,000
Building and Improvements		240,416,000
Land held for development		4,674,000
Total		263,879,000
Accumulated Depreciation		$ 113,123,000
Depreciable Lives (Years)	[13]	(1)
Boston Properties Limited Partnership | 535 Mission Street | Office and Life Sciences Building [Member]
Original Cost
Original Land		$ 40,933,000
Original Building		148,378,000
Costs Capitalized Subsequent to Acquisition		4,629,000
Land and Improvements		40,934,000
Building and Improvements		153,006,000
Total		193,940,000
Accumulated Depreciation		$ 46,615,000
Depreciable Lives (Years)	[13]	(1)
Boston Properties Limited Partnership | Mountain View Research Park | Office and Life Sciences Building [Member]
Original Cost
Original Land		$ 95,066,000
Original Building		68,373,000
Costs Capitalized Subsequent to Acquisition		21,069,000
Land and Improvements		95,066,000
Building and Improvements		89,442,000
Total		184,508,000
Accumulated Depreciation		$ 33,095,000
Depreciable Lives (Years)	[13]	(1)
Boston Properties Limited Partnership | Reservoir Place | Office and Life Sciences Building [Member]
Original Cost
Original Land		$ 18,605,000
Original Building		104,124,000
Costs Capitalized Subsequent to Acquisition		52,085,000
Land and Improvements		19,089,000
Building and Improvements		153,898,000
Land held for development		1,827,000
Total		174,814,000
Accumulated Depreciation		$ 89,426,000
Depreciable Lives (Years)	[13]	(1)
Boston Properties Limited Partnership | 140 Kendrick Street | Office and Life Sciences Building [Member]
Original Cost
Original Land		$ 18,095,000
Original Building		66,905,000
Costs Capitalized Subsequent to Acquisition		67,871,000
Land and Improvements		18,095,000
Building and Improvements		134,776,000
Total		152,871,000
Accumulated Depreciation		$ 45,233,000
Depreciable Lives (Years)	[13]	(1)
Boston Properties Limited Partnership | 1330 Connecticut Avenue | Office and Life Sciences Building [Member]
Original Cost
Original Land		$ 25,982,000
Original Building		82,311,000
Costs Capitalized Subsequent to Acquisition		35,311,000
Land and Improvements		25,982,000
Building and Improvements		117,622,000
Total		143,604,000
Accumulated Depreciation		$ 51,767,000
Depreciable Lives (Years)	[13]	(1)
Boston Properties Limited Partnership | 880 Winter Street [Member] | Office and Life Sciences Building [Member]
Original Cost
Original Land		$ 15,597,000
Original Building		37,255,000
Costs Capitalized Subsequent to Acquisition		95,265,000
Land and Improvements		15,597,000
Building and Improvements		132,520,000
Total		148,117,000
Accumulated Depreciation		$ 10,056,000
Depreciable Lives (Years)	[13]	(1)
Boston Properties Limited Partnership | One Freedom Square | Office and Life Sciences Building [Member]
Original Cost
Original Land		$ 9,929,000
Original Building		84,504,000
Costs Capitalized Subsequent to Acquisition		43,348,000
Land and Improvements		9,883,000
Building and Improvements		127,898,000
Total		137,781,000
Accumulated Depreciation		$ 66,495,000
Depreciable Lives (Years)	[13]	(1)
Boston Properties Limited Partnership | Two Freedom Square | Office and Life Sciences Building [Member]
Original Cost
Original Land		$ 13,930,000
Original Building		77,739,000
Costs Capitalized Subsequent to Acquisition		38,856,000
Land and Improvements		13,866,000
Building and Improvements		116,659,000
Total		130,525,000
Accumulated Depreciation		$ 42,556,000
Depreciable Lives (Years)	[13]	(1)
Boston Properties Limited Partnership | Kingstowne Towne Center | Office and Life Sciences Building [Member]
Original Cost
Original Land		$ 18,021,000
Original Building		109,038,000
Costs Capitalized Subsequent to Acquisition		4,501,000
Land and Improvements		18,021,000
Building and Improvements		113,539,000
Total		131,560,000
Accumulated Depreciation		$ 54,432,000
Depreciable Lives (Years)	[13]	(1)
Boston Properties Limited Partnership | One and Two Reston Overlook | Office and Life Sciences Building [Member]
Original Cost
Original Land		$ 16,456,000
Original Building		66,192,000
Costs Capitalized Subsequent to Acquisition		40,806,000
Land and Improvements		15,074,000
Building and Improvements		108,380,000
Total		123,454,000
Accumulated Depreciation		$ 60,074,000
Depreciable Lives (Years)	[13]	(1)
Boston Properties Limited Partnership | Shady Grove Innovation District [Member] | Office and Life Sciences Building [Member]
Original Cost
Original Land		$ 52,030,000
Original Building		64,212,000
Costs Capitalized Subsequent to Acquisition		10,676,000
Land and Improvements		26,834,000
Building and Improvements		34,954,000
Land held for development		65,130,000
Total		126,918,000
Accumulated Depreciation		$ 4,701,000
Depreciable Lives (Years)	[13]	(1)
Boston Properties Limited Partnership | Weston Corporate Center | Office and Life Sciences Building [Member]
Original Cost
Original Land		$ 25,753,000
Original Building		92,312,000
Costs Capitalized Subsequent to Acquisition		1,038,000
Land and Improvements		25,854,000
Building and Improvements		93,249,000
Total		119,103,000
Accumulated Depreciation		$ 41,485,000
Depreciable Lives (Years)	[13]	(1)
Boston Properties Limited Partnership | 355 Main Street | Office and Life Sciences Building [Member]
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate and Accumulated Depreciation [Line Items]
Encumbrances		$ 593,545,000
Original Cost
Original Land		18,863,000
Original Building		53,346,000
Costs Capitalized Subsequent to Acquisition		41,474,000
Land and Improvements		21,098,000
Building and Improvements		92,585,000
Total		113,683,000
Accumulated Depreciation		$ 36,858,000
Depreciable Lives (Years)	[13]	(1)
Boston Properties Limited Partnership | 17Fifty Presidents Street | Office and Life Sciences Building [Member]
Original Cost
Original Land		$ 0
Original Building		113,362,000
Costs Capitalized Subsequent to Acquisition		162,000
Land and Improvements		0
Building and Improvements		113,524,000
Total		113,524,000
Accumulated Depreciation		$ 16,624,000
Depreciable Lives (Years)	[13]	(1)
Boston Properties Limited Partnership | 200 West Street | Office and Life Sciences Building [Member]
Original Cost
Original Land		$ 16,148,000
Original Building		24,983,000
Costs Capitalized Subsequent to Acquisition		68,538,000
Land and Improvements		16,148,000
Building and Improvements		93,164,000
Land held for development		357,000
Total		109,669,000
Accumulated Depreciation		$ 27,290,000
Depreciable Lives (Years)	[13]	(1)
Boston Properties Limited Partnership | Discovery Square | Office and Life Sciences Building [Member]
Original Cost
Original Land		$ 11,198,000
Original Building		71,782,000
Costs Capitalized Subsequent to Acquisition		16,199,000
Land and Improvements		11,146,000
Building and Improvements		88,033,000
Total		99,179,000
Accumulated Depreciation		$ 55,135,000
Depreciable Lives (Years)	[13]	(1)
Boston Properties Limited Partnership | 10 CityPoint | Office and Life Sciences Building [Member]
Original Cost
Original Land		$ 1,953,000
Original Building		85,752,000
Costs Capitalized Subsequent to Acquisition		7,410,000
Land and Improvements		2,127,000
Building and Improvements		92,988,000
Total		95,115,000
Accumulated Depreciation		$ 24,003,000
Depreciable Lives (Years)	[13]	(1)
Boston Properties Limited Partnership | 90 Broadway | Office and Life Sciences Building [Member]
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate and Accumulated Depreciation [Line Items]
Encumbrances	[14]	$ 0
Original Cost
Original Land		19,104,000
Original Building		52,078,000
Costs Capitalized Subsequent to Acquisition		22,563,000
Land and Improvements		20,741,000
Building and Improvements		73,004,000
Total		93,745,000
Accumulated Depreciation		$ 31,484,000
Depreciable Lives (Years)	[13]	(1)
Boston Properties Limited Partnership | Waltham Weston Corporate Center | Office and Life Sciences Building [Member]
Original Cost
Original Land		$ 10,385,000
Original Building		60,694,000
Costs Capitalized Subsequent to Acquisition		17,718,000
Land and Improvements		10,350,000
Building and Improvements		78,447,000
Total		88,797,000
Accumulated Depreciation		$ 44,588,000
Depreciable Lives (Years)	[13]	(1)
Boston Properties Limited Partnership | 153 & 211 Second Avenue [Member] | Office and Life Sciences Building [Member]
Original Cost
Original Land		$ 33,233,000
Original Building		55,940,000
Costs Capitalized Subsequent to Acquisition		718,000
Land and Improvements		33,233,000
Building and Improvements		55,940,000
Land held for development		718,000
Total		89,891,000
Accumulated Depreciation		$ 6,186,000
Depreciable Lives (Years)	[13]	(1)
Boston Properties Limited Partnership | 230 CityPoint | Office and Life Sciences Building [Member]
Original Cost
Original Land		$ 13,189,000
Original Building		49,823,000
Costs Capitalized Subsequent to Acquisition		22,680,000
Land and Improvements		13,403,000
Building and Improvements		72,289,000
Total		85,692,000
Accumulated Depreciation		$ 40,413,000
Depreciable Lives (Years)	[13]	(1)
Boston Properties Limited Partnership | 20 Citypoint | Office and Life Sciences Building [Member]
Original Cost
Original Land		$ 4,887,000
Original Building		72,764,000
Costs Capitalized Subsequent to Acquisition		7,072,000
Land and Improvements		4,887,000
Building and Improvements		79,836,000
Total		84,723,000
Accumulated Depreciation		$ 13,031,000
Depreciable Lives (Years)	[13]	(1)
Boston Properties Limited Partnership | Sumner Square | Office and Life Sciences Building [Member]
Original Cost
Original Land		$ 624,000
Original Building		28,745,000
Costs Capitalized Subsequent to Acquisition		49,173,000
Land and Improvements		27,317,000
Building and Improvements		51,225,000
Total		78,542,000
Accumulated Depreciation		$ 32,209,000
Depreciable Lives (Years)	[13]	(1)
Boston Properties Limited Partnership | 77 CityPoint | Office and Life Sciences Building [Member]
Original Cost
Original Land		$ 13,847,000
Original Building		60,383,000
Costs Capitalized Subsequent to Acquisition		1,401,000
Land and Improvements		13,997,000
Building and Improvements		61,634,000
Total		75,631,000
Accumulated Depreciation		$ 26,911,000
Depreciable Lives (Years)	[13]	(1)
Boston Properties Limited Partnership | 2440 West El Camino Real | Office and Life Sciences Building [Member]
Original Cost
Original Land		$ 16,741,000
Original Building		51,285,000
Costs Capitalized Subsequent to Acquisition		6,565,000
Land and Improvements		16,741,000
Building and Improvements		57,850,000
Total		74,591,000
Accumulated Depreciation		$ 21,469,000
Depreciable Lives (Years)	[13]	(1)
Boston Properties Limited Partnership | Wisconsin Place | Office and Life Sciences Building [Member]
Original Cost
Original Land		$ 0
Original Building		53,349,000
Costs Capitalized Subsequent to Acquisition		13,834,000
Land and Improvements		0
Building and Improvements		67,183,000
Total		67,183,000
Accumulated Depreciation		$ 28,960,000
Depreciable Lives (Years)	[13]	(1)
Boston Properties Limited Partnership | Reston Corporate Center | Office and Life Sciences Building [Member]
Original Cost
Original Land		$ 9,135,000
Original Building		50,857,000
Costs Capitalized Subsequent to Acquisition		1,878,000
Land and Improvements		9,496,000
Building and Improvements		52,374,000
Total		61,870,000
Accumulated Depreciation		$ 33,309,000
Depreciable Lives (Years)	[13]	(1)
Boston Properties Limited Partnership | 255 Main Street | Office and Life Sciences Building [Member]
Original Cost
Original Land		$ 134,000
Original Building		25,110,000
Costs Capitalized Subsequent to Acquisition		31,674,000
Land and Improvements		134,000
Building and Improvements		56,784,000
Total		56,918,000
Accumulated Depreciation		$ 43,368,000
Depreciable Lives (Years)	[13]	(1)
Boston Properties Limited Partnership | University Place | Office and Life Sciences Building [Member]
Original Cost
Original Land		$ 0
Original Building		37,091,000
Costs Capitalized Subsequent to Acquisition		14,318,000
Land and Improvements		4,807,000
Building and Improvements		46,602,000
Total		51,409,000
Accumulated Depreciation		$ 36,037,000
Depreciable Lives (Years)	[13]	(1)
Boston Properties Limited Partnership | 890 Winter Street | Office and Life Sciences Building [Member]
Original Cost
Original Land		$ 13,913,000
Original Building		28,557,000
Costs Capitalized Subsequent to Acquisition		8,507,000
Land and Improvements		13,913,000
Building and Improvements		37,064,000
Total		50,977,000
Accumulated Depreciation		$ 7,296,000
Depreciable Lives (Years)	[13]	(1)
Boston Properties Limited Partnership | Capital Gallery | Office and Life Sciences Building [Member]
Original Cost
Original Land		$ 4,725,000
Original Building		29,565,000
Costs Capitalized Subsequent to Acquisition		5,698,000
Land and Improvements		6,128,000
Building and Improvements		33,860,000
Total		39,988,000
Accumulated Depreciation		$ 22,801,000
Depreciable Lives (Years)	[13]	(1)
Boston Properties Limited Partnership | North First Business Park | Office and Life Sciences Building [Member]
Original Cost
Original Land		$ 23,398,000
Original Building		13,069,000
Costs Capitalized Subsequent to Acquisition		5,235,000
Land and Improvements		23,372,000
Building and Improvements		18,330,000
Total		41,702,000
Accumulated Depreciation		$ 17,347,000
Depreciable Lives (Years)	[13]	(1)
Boston Properties Limited Partnership | 150 Broadway | Office and Life Sciences Building [Member]
Original Cost
Original Land		$ 850,000
Original Building		25,042,000
Costs Capitalized Subsequent to Acquisition		13,744,000
Land and Improvements		822,000
Building and Improvements		38,814,000
Total		39,636,000
Accumulated Depreciation		$ 17,823,000
Depreciable Lives (Years)	[13]	(1)
Boston Properties Limited Partnership | 105 Broadway | Office and Life Sciences Building [Member]
Original Cost
Original Land		$ 1,299,000
Original Building		12,943,000
Costs Capitalized Subsequent to Acquisition		10,617,000
Land and Improvements		1,868,000
Building and Improvements		22,991,000
Total		24,859,000
Accumulated Depreciation		$ 16,133,000
Depreciable Lives (Years)	[13]	(1)
Boston Properties Limited Partnership | Lexington Office Park | Office and Life Sciences Building [Member]
Original Cost
Original Land		$ 998,000
Original Building		1,426,000
Costs Capitalized Subsequent to Acquisition		19,160,000
Land and Improvements		1,072,000
Building and Improvements		18,897,000
Land held for development		1,615,000
Total		21,584,000
Accumulated Depreciation		$ 16,945,000
Depreciable Lives (Years)	[13]	(1)
Boston Properties Limited Partnership | The Point | Office and Life Sciences Building [Member]
Original Cost
Original Land		$ 6,395,000
Original Building		10,040,000
Costs Capitalized Subsequent to Acquisition		546,000
Land and Improvements		6,492,000
Building and Improvements		10,489,000
Total		16,981,000
Accumulated Depreciation		$ 2,638,000
Depreciable Lives (Years)	[13]	(1)
Boston Properties Limited Partnership | 690 Folsom Street | Office and Life Sciences Building [Member]
Original Cost
Original Land		$ 3,219,000
Original Building		11,038,000
Costs Capitalized Subsequent to Acquisition		1,877,000
Land and Improvements		3,219,000
Building and Improvements		12,915,000
Total		16,134,000
Accumulated Depreciation		$ 4,280,000
Depreciable Lives (Years)	[13]	(1)
Boston Properties Limited Partnership | 33 Hayden Avenue | Office and Life Sciences Building [Member]
Original Cost
Original Land		$ 266,000
Original Building		3,234,000
Costs Capitalized Subsequent to Acquisition		10,865,000
Land and Improvements		266,000
Building and Improvements		14,099,000
Total		14,365,000
Accumulated Depreciation		$ 8,873,000
Depreciable Lives (Years)	[13]	(1)
Boston Properties Limited Partnership | The Avant Retail | Office and Life Sciences Building [Member]
Original Cost
Original Land		$ 1,499,000
Original Building		6,647,000
Costs Capitalized Subsequent to Acquisition		2,577,000
Land and Improvements		1,499,000
Building and Improvements		9,224,000
Total		10,723,000
Accumulated Depreciation		$ 3,587,000
Depreciable Lives (Years)	[13]	(1)
Boston Properties Limited Partnership | 92-100 Hayden Avenue | Office and Life Sciences Building [Member]
Original Cost
Original Land		$ 594,000
Original Building		6,748,000
Costs Capitalized Subsequent to Acquisition		1,193,000
Land and Improvements		595,000
Building and Improvements		7,940,000
Total		8,535,000
Accumulated Depreciation		$ 7,140,000
Depreciable Lives (Years)	[13]	(1)
Boston Properties Limited Partnership | 32 Hartwell Avenue | Office and Life Sciences Building [Member]
Original Cost
Original Land		$ 168,000
Original Building		1,943,000
Costs Capitalized Subsequent to Acquisition		5,817,000
Land and Improvements		168,000
Building and Improvements		7,760,000
Total		7,928,000
Accumulated Depreciation		$ 2,731,000
Depreciable Lives (Years)	[13]	(1)
Boston Properties Limited Partnership | 250 Binney Street | Office and Life Sciences Building [Member]
Original Cost
Original Land		$ 110,000
Original Building		4,483,000
Costs Capitalized Subsequent to Acquisition		2,939,000
Land and Improvements		110,000
Building and Improvements		7,422,000
Total		7,532,000
Accumulated Depreciation		$ 7,026,000
Depreciable Lives (Years)	[13]	(1)
Boston Properties Limited Partnership | 453 Ravendale Drive | Office and Life Sciences Building [Member]
Original Cost
Original Land		$ 5,477,000
Original Building		1,090,000
Costs Capitalized Subsequent to Acquisition		1,286,000
Land and Improvements		5,477,000
Building and Improvements		2,376,000
Total		7,853,000
Accumulated Depreciation		$ 1,086,000
Depreciable Lives (Years)	[13]	(1)
Boston Properties Limited Partnership | 17 Hartwell Avenue | Office and Life Sciences Building [Member]
Original Cost
Original Land		$ 26,000
Original Building		150,000
Costs Capitalized Subsequent to Acquisition		5,907,000
Land and Improvements		26,000
Building and Improvements		6,057,000
Total		6,083,000
Accumulated Depreciation		$ 3,701,000
Depreciable Lives (Years)	[13]	(1)
Boston Properties Limited Partnership | The Skylyne | Residential Building
Original Cost
Original Land		$ 28,962,000
Original Building		239,077,000
Costs Capitalized Subsequent to Acquisition		1,792,000
Land and Improvements		28,962,000
Building and Improvements		240,869,000
Total		269,831,000
Accumulated Depreciation		$ 20,181,000
Depreciable Lives (Years)	[13]	(1)
Boston Properties Limited Partnership | Signature at Reston | Residential Building
Original Cost
Original Land		$ 27,076,000
Original Building		190,580,000
Costs Capitalized Subsequent to Acquisition		3,817,000
Land and Improvements		27,076,000
Building and Improvements		194,397,000
Total		221,473,000
Accumulated Depreciation		$ 27,876,000
Depreciable Lives (Years)	[13]	(1)
Boston Properties Limited Partnership | Proto Kendall Square | Residential Building
Original Cost
Original Land		$ 9,243,000
Original Building		127,248,000
Costs Capitalized Subsequent to Acquisition		3,336,000
Land and Improvements		9,245,000
Building and Improvements		130,582,000
Total		139,827,000
Accumulated Depreciation		$ 17,820,000
Depreciable Lives (Years)	[13]	(1)
Boston Properties Limited Partnership | The Lofts at Atlantic Wharf | Residential Building
Original Cost
Original Land		$ 3,529,000
Original Building		54,891,000
Costs Capitalized Subsequent to Acquisition		2,509,000
Land and Improvements		3,529,000
Building and Improvements		57,400,000
Total		60,929,000
Accumulated Depreciation		$ 18,631,000
Depreciable Lives (Years)	[13]	(1)
Boston Properties Limited Partnership | Boston Cambridge Marriott | Hotel [Member]
Original Cost
Original Land		$ 478,000
Original Building		37,918,000
Costs Capitalized Subsequent to Acquisition		29,240,000
Land and Improvements		478,000
Building and Improvements		66,529,000
Land held for development		629,000
Total		67,636,000
Accumulated Depreciation		$ 52,302,000
Depreciable Lives (Years)	[13]	(1)
Boston Properties Limited Partnership | Kendall Center Green Garage | Garage
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate and Accumulated Depreciation [Line Items]
Encumbrances	[14]	$ 0
Original Cost
Original Land		0
Original Building		35,035,000
Costs Capitalized Subsequent to Acquisition		6,921,000
Building and Improvements		41,956,000
Total		41,956,000
Accumulated Depreciation		$ 18,275,000
Depreciable Lives (Years)	[13]	(1)
Boston Properties Limited Partnership | Kendall Center Yellow Garage | Garage
Original Cost
Original Land		$ 1,256,000
Original Building		15,697,000
Costs Capitalized Subsequent to Acquisition		1,031,000
Land and Improvements		1,256,000
Building and Improvements		16,728,000
Total		17,984,000
Accumulated Depreciation		$ 7,619,000
Depreciable Lives (Years)	[13]	(1)
Boston Properties Limited Partnership | 290 Binney | Development
Original Cost
Original Land		$ 0
Original Building		0
Costs Capitalized Subsequent to Acquisition		242,683,000
Land and Improvements		638,000
Development and Construction in Progress		242,045,000
Total		242,683,000
Accumulated Depreciation		$ 0
Depreciable Lives (Years)		N/A
Boston Properties Limited Partnership | 180 CityPoint [Member] | Development
Original Cost
Original Land		$ 0
Original Building		0
Costs Capitalized Subsequent to Acquisition		214,754,000
Land and Improvements		10,908,000
Building and Improvements		108,970,000
Development and Construction in Progress		94,876,000
Total		214,754,000
Accumulated Depreciation		$ 541,000
Depreciable Lives (Years)		N/A
Boston Properties Limited Partnership | 300 Binney Street | Development
Original Cost
Original Land		$ 18,080,000
Original Building		51,262,000
Costs Capitalized Subsequent to Acquisition		38,454,000
Land and Improvements		18,080,000
Building and Improvements		27,805,000
Development and Construction in Progress		61,911,000
Total		107,796,000
Accumulated Depreciation		$ 6,719,000
Depreciable Lives (Years)		N/A
Boston Properties Limited Partnership | 103 CityPoint | Development
Original Cost
Original Land		$ 0
Original Building		0
Costs Capitalized Subsequent to Acquisition		88,188,000
Land and Improvements		4,670,000
Building and Improvements		3,025,000
Land held for development		8,672,000
Development and Construction in Progress		71,821,000
Total		88,188,000
Accumulated Depreciation		$ 18,000
Depreciable Lives (Years)		N/A
Boston Properties Limited Partnership | Reston Next Office Phase II | Development
Original Cost
Original Land		$ 0
Original Building		0
Costs Capitalized Subsequent to Acquisition		39,201,000
Development and Construction in Progress		39,201,000
Total		39,201,000
Accumulated Depreciation		$ 0
Depreciable Lives (Years)		N/A
Boston Properties Limited Partnership | Reston Next Retail | Development
Original Cost
Original Land		$ 0
Original Building		0
Costs Capitalized Subsequent to Acquisition		8,367,000
Development and Construction in Progress		8,367,000
Total		8,367,000
Accumulated Depreciation		$ 0
Depreciable Lives (Years)		N/A
Boston Properties Limited Partnership | 343 Madison Avenue | Land
Original Cost
Original Land		$ 0
Original Building		0
Costs Capitalized Subsequent to Acquisition		206,052,000
Land and Improvements		158,885,000
Land held for development		47,167,000
Total		206,052,000
Accumulated Depreciation		$ 0
Depreciable Lives (Years)		N/A
Boston Properties Limited Partnership | 777 Harrison Street | Land
Original Cost
Original Land		$ 144,647,000
Original Building		0
Costs Capitalized Subsequent to Acquisition		28,334,000
Building and Improvements		47,000
Land held for development		172,934,000
Total		172,981,000
Accumulated Depreciation		$ 29,000
Depreciable Lives (Years)		N/A
Boston Properties Limited Partnership | Back Bay Station Master Plan | Land
Original Cost
Original Land		$ 0
Original Building		0
Costs Capitalized Subsequent to Acquisition		78,150,000
Land held for development		78,150,000
Total		78,150,000
Accumulated Depreciation		$ 0
Depreciable Lives (Years)		N/A
Boston Properties Limited Partnership | 3625 - 3635 Peterson Way | Land
Original Cost
Original Land		$ 63,206,000
Original Building		0
Costs Capitalized Subsequent to Acquisition		5,173,000
Land held for development		68,379,000
Total		68,379,000
Accumulated Depreciation		$ 0
Depreciable Lives (Years)		N/A
Boston Properties Limited Partnership | Kendall Center Master Plan | Land
Original Cost
Original Land		$ 0
Original Building		0
Costs Capitalized Subsequent to Acquisition		48,857,000
Land held for development		48,857,000
Total		48,857,000
Accumulated Depreciation		$ 0
Depreciable Lives (Years)		N/A
Boston Properties Limited Partnership | North First Master Plan | Land
Original Cost
Original Land		$ 35,004,000
Original Building		0
Costs Capitalized Subsequent to Acquisition		4,068,000
Land held for development		39,072,000
Total		39,072,000
Accumulated Depreciation		$ 0
Depreciable Lives (Years)		N/A
Boston Properties Limited Partnership | Plaza at Almaden | Land
Original Cost
Original Land		$ 0
Original Building		0
Costs Capitalized Subsequent to Acquisition		38,163,000
Land held for development		38,163,000
Total		38,163,000
Accumulated Depreciation		$ 0
Depreciable Lives (Years)		N/A
Boston Properties Limited Partnership | CityPoint South Master Plan | Land
Original Cost
Original Land		$ 0
Original Building		0
Costs Capitalized Subsequent to Acquisition		25,594,000
Land held for development		25,594,000
Total		25,594,000
Accumulated Depreciation		$ 0
Depreciable Lives (Years)		N/A
Boston Properties Limited Partnership | Springfield Metro Center | Land
Original Cost
Original Land		$ 0
Original Building		0
Costs Capitalized Subsequent to Acquisition		19,896,000
Land held for development		19,896,000
Total		19,896,000
Accumulated Depreciation		$ 0
Depreciable Lives (Years)		N/A
Boston Properties Limited Partnership | Reston Gateway Master Plan | Land
Original Cost
Original Land		$ 0
Original Building		0
Costs Capitalized Subsequent to Acquisition		13,908,000
Land held for development		13,908,000
Total		13,908,000
Accumulated Depreciation		$ 0
Depreciable Lives (Years)		N/A
Boston Properties Limited Partnership | Weston Quarry | Land
Original Cost
Original Land		$ 0
Original Building		0
Costs Capitalized Subsequent to Acquisition		1,249,000
Land held for development		1,249,000
Total		1,249,000
Accumulated Depreciation		$ 0
Depreciable Lives (Years)		N/A
Boston Properties Limited Partnership | Broad Run Business Park | Land
Original Cost
Original Land		$ 0
Original Building		0
Costs Capitalized Subsequent to Acquisition		1,186,000
Land held for development		1,186,000
Total		1,186,000
Accumulated Depreciation		$ 0
Depreciable Lives (Years)		N/A
Boston Properties Limited Partnership | Reston Overlook Master Plan | Land
Original Cost
Original Land		$ 0
Original Building		0
Costs Capitalized Subsequent to Acquisition		80,000
Land held for development		80,000
Total		80,000
Accumulated Depreciation		$ 0
Depreciable Lives (Years)		N/A

[1] Includes unamortized deferred financing costs and fair value debt adjustment totaling approximately $(33.6) million.

[2] Includes Right of Use Assets - Finance Leases and Right of Use Assets - Operating Leases of approximately $378,276 and $324,298, respectively.

[3] Includes Right of Use Assets - Finance Leases of approximately $23,404.

[4] Includes pre-development costs.

[5] Includes pre-development costs.

[6] See Note 4.

[7] Depreciation of the buildings and improvements are calculated over lives ranging from the life of the lease to 40 years.

[8] This property is encumbered with the mortgage note shown at 355 Main Street. See Note 7 to the Consolidated Financial Statements.

[9] Includes unamortized deferred financing costs and fair value debt adjustment totaling approximately $(33.6) million.

[10] Includes Right of Use Assets - Finance Leases and Right of Use Assets - Operating Leases of approximately $378,276 and $324,298, respectively.

[11] Includes Right of Use Assets - Finance Leases of approximately $23,404.

[12] Includes pre-development costs.

[13] Depreciation of the buildings and improvements are calculated over lives ranging from the life of the lease to 40 years.

[14] This property is encumbered with the mortgage note shown at 355 Main Street. See Note 7 to the Consolidated Financial Statements.