Investments in Partially Owned Entities - Partially Owned Property Balance Sheet Schedule (Details) $ in Thousands	Dec. 31, 2017 USD ($) Property ApartmentUnit	Dec. 31, 2016 USD ($)	Dec. 31, 2015 USD ($)
Partially Owned Property Balance Sheet Schedule
Total properties | Property	305
Apartment Units | ApartmentUnit	78,611
ASSETS
Investment in real estate	$ 26,026,896	$ 25,386,425
Accumulated depreciation	(6,040,378)	(5,360,389)
Investment in real estate, net	19,986,518	20,026,036
Cash and cash equivalents	50,647	77,207	$ 42,276
Investments in unconsolidated entities	58,254	60,141
Restricted deposits	50,115	141,881	$ 112,839
Other assets	425,065	398,883
Total assets	20,570,599	20,704,148
LIABILITIES AND EQUITY
Mortgage notes payable, net	3,618,722	4,119,181
Accounts payable and accrued expenses	114,766	147,482
Accrued interest payable	58,035	60,946
Other liabilities	341,852	350,466
Security deposits	65,009	62,624
Total liabilities	9,729,781	9,801,072
Partially Owned Properties	4,708	10,609
Total equity	10,473,863	10,460,984
Total liabilities and equity/capital	$ 20,570,599	$ 20,704,148
Unconsolidated Non-VIE
Partially Owned Property Balance Sheet Schedule
Total properties | Property	2
Apartment Units | ApartmentUnit	945
ASSETS
Investment in real estate	$ 236,749
Accumulated depreciation	(43,512)
Investment in real estate, net	193,237
Cash and cash equivalents	5,245
Investments in unconsolidated entities	0
Restricted deposits	258
Other assets	323
Total assets	199,063
LIABILITIES AND EQUITY
Mortgage notes payable, net	145,424
Accounts payable and accrued expenses	181
Accrued interest payable	691
Other liabilities	291
Security deposits	485
Total liabilities	147,072
Partially Owned Properties	52,850
Company equity/General and Limited Partners’ Capital	(859)
Total equity	51,991
Total liabilities and equity/capital	$ 199,063
Consolidated VIE
Partially Owned Property Balance Sheet Schedule
Total properties | Property	17
Apartment Units | ApartmentUnit	3,215
ASSETS
Investment in real estate	$ 649,777
Accumulated depreciation	(236,543)
Investment in real estate, net	413,234
Cash and cash equivalents	34,954
Investments in unconsolidated entities	44,451
Restricted deposits	393
Other assets	25,851
Total assets	518,883
LIABILITIES AND EQUITY
Mortgage notes payable, net	302,347
Accounts payable and accrued expenses	1,110
Accrued interest payable	1,037
Other liabilities	465
Security deposits	2,053
Total liabilities	307,012
Partially Owned Properties	4,708
Company equity/General and Limited Partners’ Capital	207,163
Total equity	211,871
Total liabilities and equity/capital	$ 518,883
Unconsolidated VIE
Partially Owned Property Balance Sheet Schedule
Total properties | Property	0
Apartment Units | ApartmentUnit	0
ASSETS
Investment in real estate	$ 172,995
Accumulated depreciation	(50,045)
Investment in real estate, net	122,950
Cash and cash equivalents	60
Investments in unconsolidated entities	0
Restricted deposits	0
Other assets	395
Total assets	123,405
LIABILITIES AND EQUITY
Mortgage notes payable, net	0
Accounts payable and accrued expenses	295
Accrued interest payable	0
Other liabilities	6
Security deposits	0
Total liabilities	301
Partially Owned Properties	84,302
Company equity/General and Limited Partners’ Capital	38,802
Total equity	123,104
Total liabilities and equity/capital	$ 123,405
Partially Owned Properties – Unconsolidated
Partially Owned Property Balance Sheet Schedule
Total properties | Property	2
Apartment Units | ApartmentUnit	945
ASSETS
Investment in real estate	$ 409,744
Accumulated depreciation	(93,557)
Investment in real estate, net	316,187
Cash and cash equivalents	5,305
Investments in unconsolidated entities	0
Restricted deposits	258
Other assets	718
Total assets	322,468
LIABILITIES AND EQUITY
Mortgage notes payable, net	145,424
Accounts payable and accrued expenses	476
Accrued interest payable	691
Other liabilities	297
Security deposits	485
Total liabilities	147,373
Partially Owned Properties	137,152
Company equity/General and Limited Partners’ Capital	37,943
Total equity	175,095
Total liabilities and equity/capital	$ 322,468