Segment Reporting (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Reconciliation of NOI to net income
Net income	$ 192,407	$ 238,199	$ 588,540	$ 639,174
Indirect operating expenses, net of corporate income	18,855	15,752	55,850	48,472
Investments and investment management expense	1,726	1,501	4,898	4,277
Expensed transaction, development and other pursuit costs, net of recoveries	1,020	789	2,709	2,087
Interest expense, net	54,097	47,741	165,795	147,138
Loss on extinguishment of debt, net	1,678	0	2,717	24,162
General and administrative expense	13,905	11,655	42,013	38,808
Equity in income of unconsolidated real estate entities	(10,031)	(52,568)	(12,560)	(70,386)
Depreciation expense	156,538	144,990	472,282	427,050
Income tax expense	29	24	87	102
Casualty and impairment (gain) loss, net	(554)	0	(612)	11,688
Gain on sale of communities	(27,243)	(27,738)	(132,444)	(159,754)
(Gain) loss on other real estate transactions, net	(12)	120	(335)	(246)
Net operating income from real estate assets sold or held for sale	(2,545)	(10,340)	(15,913)	(35,162)
Net operating income	$ 399,870	370,125	$ 1,173,027	1,077,410
Avalon Maplewood [Member]
Business Interruption Loss [Line Items]
Gain on Business Interruption Insurance Recovery		$ 3,495		3,495
Reconciliation of NOI to net income
Casualty and impairment (gain) loss, net				$ 2,338