Investments in Partially Owned Entities - Partially Owned Property Balance Sheet Schedule (Details) $ in Thousands	Sep. 30, 2017 USD ($) Property ApartmentUnit	Dec. 31, 2016 USD ($)	Sep. 30, 2016 USD ($)	Dec. 31, 2015 USD ($)
Partially Owned Property Balance Sheet Schedule
Total properties | Property	305
Total apartment units | ApartmentUnit	78,302
ASSETS
Investment in real estate	$ 25,948,543	$ 25,386,425
Accumulated depreciation	(5,849,110)	(5,360,389)
Investment in real estate, net	20,099,433	20,026,036
Cash and cash equivalents	46,565	77,207	$ 517,586	$ 42,276
Investments in unconsolidated entities	59,029	60,141
Deposits – restricted	36,639	76,946
Other assets	445,195	398,883
Total assets	20,697,833	20,704,148
LIABILITIES AND EQUITY
Mortgage notes payable, net	3,619,180	4,119,181
Accounts payable and accrued expenses	167,984	147,482
Accrued interest payable	72,811	60,946
Other liabilities	332,650	350,466
Security deposits	65,230	62,624
Total liabilities	9,823,516	9,801,072
Partially Owned Properties	6,175	10,609
Total equity	10,493,776	10,460,984
Total liabilities and equity/capital	$ 20,697,833	$ 20,704,148
Unconsolidated Non-VIE
Partially Owned Property Balance Sheet Schedule
Total properties | Property	2
Total apartment units | ApartmentUnit	945
ASSETS
Investment in real estate	$ 236,630
Accumulated depreciation	(40,840)
Investment in real estate, net	195,790
Cash and cash equivalents	7,194
Investments in unconsolidated entities	0
Deposits – restricted	258
Other assets	450
Total assets	203,692
LIABILITIES AND EQUITY
Mortgage notes payable, net	145,424
Accounts payable and accrued expenses	2,644
Accrued interest payable	691
Other liabilities	308
Security deposits	488
Total liabilities	149,555
Partially Owned Properties	54,336
Company equity/General and Limited Partners' Capital	(199)
Total equity	54,137
Total liabilities and equity/capital	$ 203,692
Consolidated VIE
Partially Owned Property Balance Sheet Schedule
Total properties | Property	17
Total apartment units | ApartmentUnit	3,215
ASSETS
Investment in real estate	$ 648,839
Accumulated depreciation	(226,607)
Investment in real estate, net	422,232
Cash and cash equivalents	22,914
Investments in unconsolidated entities	45,035
Deposits – restricted	385
Other assets	26,246
Total assets	516,812
LIABILITIES AND EQUITY
Mortgage notes payable, net	302,037
Accounts payable and accrued expenses	2,975
Accrued interest payable	1,024
Other liabilities	453
Security deposits	2,037
Total liabilities	308,526
Partially Owned Properties	6,175
Company equity/General and Limited Partners' Capital	202,111
Total equity	208,286
Total liabilities and equity/capital	$ 516,812
Unconsolidated VIE
Partially Owned Property Balance Sheet Schedule
Total properties | Property	0
Total apartment units | ApartmentUnit	0
ASSETS
Investment in real estate	$ 172,995
Accumulated depreciation	(48,670)
Investment in real estate, net	124,325
Cash and cash equivalents	139
Investments in unconsolidated entities	0
Deposits – restricted	0
Other assets	105
Total assets	124,569
LIABILITIES AND EQUITY
Mortgage notes payable, net	0
Accounts payable and accrued expenses	150
Accrued interest payable	0
Other liabilities	27
Security deposits	0
Total liabilities	177
Partially Owned Properties	84,682
Company equity/General and Limited Partners' Capital	39,710
Total equity	124,392
Total liabilities and equity/capital	$ 124,569
Partially Owned Properties – Unconsolidated
Partially Owned Property Balance Sheet Schedule
Total properties | Property	2
Total apartment units | ApartmentUnit	945
ASSETS
Investment in real estate	$ 409,625
Accumulated depreciation	(89,510)
Investment in real estate, net	320,115
Cash and cash equivalents	7,333
Investments in unconsolidated entities	0
Deposits – restricted	258
Other assets	555
Total assets	328,261
LIABILITIES AND EQUITY
Mortgage notes payable, net	145,424
Accounts payable and accrued expenses	2,794
Accrued interest payable	691
Other liabilities	335
Security deposits	488
Total liabilities	149,732
Partially Owned Properties	139,018
Company equity/General and Limited Partners' Capital	39,511
Total equity	178,529
Total liabilities and equity/capital	$ 328,261