Consolidated Balance Sheets - USD ($) $ in Thousands	Jun. 30, 2015	Dec. 31, 2014
ASSETS
Real estate, at cost	$ 17,786,089	$ 17,810,133
Construction in progress	880,996	736,311
Land held for future development	277,327	268,114
Less: accumulated depreciation	(3,678,591)	(3,476,321)
Total real estate	15,265,821	15,338,237
Cash and cash equivalents	1,342,751	1,763,079
Cash held in escrows	252,558	487,321
Investments in securities	20,953	19,459
Tenant and other receivables (net of allowance for doubtful accounts of $1,061 and $1,142, respectively)	55,183	46,595
Accrued rental income (net of allowance of $1,219 and $1,499, respectively)	730,797	691,999
Deferred charges, net	771,419	831,744
Prepaid expenses and other assets	117,993	164,432
Investments in unconsolidated joint ventures	209,974	193,394
Total assets	18,767,449	19,536,260
Liabilities:
Mortgage notes payable	4,269,808	4,309,484
Unsecured senior notes (net of discount of $11,497 and $12,296, respectively)	5,288,503	5,287,704
Unsecured line of credit	0	0
Mezzanine notes payable	309,148	309,796
Outside members' notes payable	180,000	180,000
Accounts payable and accrued expenses	231,900	243,263
Distributions payable	112,892	882,472
Accrued interest payable	178,548	163,532
Other liabilities	448,480	502,255
Total liabilities	11,019,279	11,878,506
Commitments and contingencies	0	0
Noncontrolling interests:
Redeemable interest in property partnership	106,233	104,692
Redeemable partnership units—0 and 12,667 series four preferred units outstanding at redemption value at June 30, 2015 and December 31, 2014, respectively	0	633
Redeemable partnership units—16,192,518 and 16,453,670 common units and 1,839,555 and 1,496,799 long term incentive units outstanding at redemption value at June 30, 2015 and December 31, 2014, respectively	2,182,602	2,310,046
Capital:
5.25% Series B cumulative redeemable preferred units, liquidation preference $2,500 per unit, 80,000 units issued and outstanding at June 30, 2015 and December 31, 2014	193,623	193,623
Boston Properties Limited Partnership partners’ capital—1,715,060 and 1,710,644 general partner units and 151,758,871 and 151,403,301 limited partner units outstanding at June 30, 2015 and December 31, 2014, respectively	3,675,231	3,446,293
Noncontrolling interests in property partnerships	1,590,481	1,602,467
Total capital	5,459,335	5,242,383
Total liabilities and capital	$ 18,767,449	$ 19,536,260