Consolidated Balance Sheets - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017
Commercial real estate properties, at cost:
Land	$ 201,196	$ 201,196
Development costs	7,987	7,986
Building and improvements	2,675,303	2,458,473
Commercial real estate properties, at cost, gross	2,884,486	2,667,655
Less: accumulated depreciation	(747,304)	(656,900)
Commercial real estate properties, net	2,137,182	2,010,755
Cash and cash equivalents	204,981	464,344
Restricted cash	65,832	65,853
Short-term Investments	400,000	0
Tenant and other receivables, net of allowance of $488 and $1,422 in 2018 and 2017, respectively	29,437	28,329
Deferred rent receivables, net of allowance of $19 and $185 in 2018 and 2017, respectively	200,903	178,629
Prepaid expenses and other assets	64,345	61,028
Deferred costs, net	241,223	262,701
Acquired below market ground leases, net	360,398	368,229
Goodwill	491,479	491,479
Total assets	4,195,780	3,931,347
Liabilities:
Mortgage notes payable, net	608,567	717,164
Senior unsecured notes, net	1,046,219	707,895
Unsecured term loan facility, net	264,147	263,662
Unsecured revolving credit facility	0	0
Accounts payable and accrued expenses	130,676	110,849
Acquired below market leases, net	52,450	66,047
Deferred revenue and other liabilities	44,810	40,907
Tenants’ security deposits	57,802	47,086
Total liabilities	2,204,671	1,953,610
Commitments and contingencies
Capital:
Private perpetual preferred units, $16.62 per unit liquidation preference, 1,560,360 issued and outstanding in 2018 and 2017, respectively	8,004	8,004
Total capital	1,991,109	1,977,737
Total liabilities and capital	4,195,780	3,931,347
Series PR Operating Partnership Units
Capital:
ESRT partners' capital (3,033,261 and 3,004,095 general partner operating partnership units and 171,877,365 and 158,472,949 limited partner operating partnership units outstanding at December 31, 2018 and 2017, respectively)	1,238,482	1,168,282
Limited partner operating partnership units	725,108	778,279
Series ES Operating Partnership Units Limited Partners
Capital:
Limited partner operating partnership units	14,399	17,132
Series 60 Operating Partnership Units Limited Partners
Capital:
Limited partner operating partnership units	3,385	3,992
Series 250 Operating Partnership Units Limited Partners
Capital:
Limited partner operating partnership units	$ 1,731	$ 2,048