Condensed Consolidated Balance Sheets - USD ($) $ in Thousands	Jun. 30, 2016	Dec. 31, 2015
Commercial real estate properties, at cost:
Land	$ 201,196	$ 201,196
Development costs	7,946	7,498
Building and improvements	2,147,050	2,067,636
Commercial real estate properties, at cost	2,356,192	2,276,330
Less: accumulated depreciation	(509,736)	(465,584)
Commercial real estate properties, net	1,846,456	1,810,746
Cash and cash equivalents	35,454	46,685
Restricted cash	59,141	65,880
Tenant and other receivables, net of allowance of $4,701 and $2,792 in 2016 and 2015, respectively	14,521	18,782
Deferred rent receivables, net of allowance of $481 and $245 in 2016 and 2015, respectively	133,955	122,048
Prepaid expenses and other assets	47,895	50,460
Deferred costs, net	292,777	310,679
Acquired below-market ground leases, net	379,976	383,891
Goodwill	491,479	491,479
Total assets	3,301,654	3,300,650
Liabilities:
Mortgage notes payable, net	767,717	747,661
Senior unsecured notes, net	588,703	587,018
Unsecured term loan facility, net	262,735	262,545
Unsecured revolving credit facility, net	40,000	35,192
Accounts payable and accrued expenses	143,296	111,099
Acquired below-market leases, net	91,850	104,171
Deferred revenue and other liabilities	23,019	31,388
Tenants’ security deposits	47,565	48,890
Total liabilities	1,964,885	1,927,964
Commitments and contingencies
Capital:
Private perpetual preferred units, $16.62 per unit liquidation preference, 1,560,360 issued and outstanding in 2016 and 2015	8,004	8,004
Total capital	1,336,769	1,372,686
Total liabilities and capital	3,301,654	3,300,650
Series PR operating partnership units
Capital:
ESRT partner's capital (2,694,887 and 2,675,740 general partner operating partnership units and 121,186,336 and 117,347,639 limited partner operating partnership units outstanding in 2016 and 2015, respectively)	521,596	524,729
Limited partner operating partnership units	786,003	809,901
Series ES operating partnership units
Capital:
Limited partner operating partnership units	15,685	22,074
Series 60 operating partnership units
Capital:
Limited partner operating partnership units	3,693	5,366
Series 250 operating partnership units
Capital:
Limited partner operating partnership units	$ 1,788	$ 2,612