Consolidated Balance Sheets (USD $) In Thousands, unless otherwise specified	Sep. 30, 2013	Dec. 31, 2012
ASSETS
Real estate, at cost	$ 16,674,568	$ 13,146,993
Construction in progress	1,502,017	1,036,780
Land held for future development	295,370	271,189
Less: accumulated depreciation	(3,013,549)	(2,876,983)
Total real estate	15,458,406	11,577,979
Cash and cash equivalents	1,641,275	1,041,978
Cash held in escrows	53,499	55,181
Investments in securities	15,377	12,172
Tenant and other receivables (net of allowance for doubtful accounts of $1,515 and $1,960, respectively)	55,393	69,555
Related party notes receivable	0	282,491
Interest receivable from related party notes receivable	0	104,816
Accrued rental income (net of allowance of $3,382 and $1,571, respectively)	641,041	598,199
Deferred charges, net	918,798	588,235
Prepaid expenses and other assets	238,688	90,610
Investments in unconsolidated joint ventures	129,038	659,916
Total assets	19,151,515	15,081,132
Liabilities:
Mortgage notes payable	4,468,069	3,102,485
Unsecured senior notes (net of discount of $14,576 and $9,472, respectively)	5,835,424	4,639,528
Unsecured exchangeable senior notes (net of discount of $555 and $1,653, respectively)	739,536	1,170,356
Unsecured line of credit	0	0
Mezzanine notes payable	311,340	0
Related party notes payable	180,000	0
Accounts payable and accrued expenses	215,778	199,102
Distributions payable	112,470	110,488
Accrued interest payable	181,310	72,461
Other liabilities	567,464	324,613
Total liabilities	12,611,391	9,619,033
Commitments and contingencies	0	0
Noncontrolling interests:
Redeemable interest in property partnerships	98,649	97,558
Redeemable partnership units-995,997 series two preferred units outstanding (1,307,083 common units at redemption value, if converted) at September 30, 2013 and December 31, 2012, respectively	139,727	138,302
Redeemable partnership units - 360,126 and 1,221,527 series four preferred units outstanding at redemption value at September 30, 2013 and December 31, 2012	18,006	61,076
Redeemable partnership units-15,738,523 and 16,053,497 common units and 1,460,200 and 1,303,296 long term incentive units outstanding at redemption value at September 30, 2013 and December 31, 2012, respectively	1,838,543	1,836,522
Capital:
5.25% Series B cumulative redeemable preferred units, liquidation preference of $2,500 per unit, 80,000 and no units issued and outstanding at September 30, 2013 and December 31,2012, respectively	193,623	0
Boston Properties Limited Partnership partners' capital-1,695,893 and 1,689,580 general partner units and 150,694,702 and 149,911,629 limited partner units outstanding at September 30, 2013 and December 31, 2012, respectively	3,769,947	3,330,605
Noncontrolling interests in property partnerships	481,629	(1,964)
Total capital	4,445,199	3,328,641
Total liabilities and capital	$ 19,151,515	$ 15,081,132