Condensed Consolidated Statements of Income (Unaudited) - USD ($) shares in Thousands, $ in Thousands		3 Months Ended		9 Months Ended
		Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Revenues
Revenues		$ 283,080	$ 294,845	$ 880,561	$ 885,609
Operating expenses
Rent		2,702	2,764	8,262	8,312
Real estate taxes		37,862	38,363	115,570	115,379
Operating and maintenance		39,265	40,262	123,921	125,539
General and administrative		21,348	21,523	67,775	63,718
Provision for doubtful accounts		1,389	701	4,571	4,201
Impairment charges		3,336	2,944	33,855	34,280
Depreciation and amortization		74,972	88,443	236,114	275,787
Total operating expenses		180,874	195,000	590,068	627,216
Operating income		102,206	99,845	290,493	258,393
Other income/(expense)
Other income, net		5,219	1,101	14,675	3,813
Interest expense		(44,081)	(47,258)	(140,458)	(139,830)
Early extinguishment of debt charges		(12,762)	(1,753)	(12,762)	(1,753)
Income from continuing operations before income taxes, net, equity in income of joint ventures, net, gain on change in control of interests and equity in income from other real estate investments, net		50,582	51,935	151,948	120,623
Benefit for income taxes, net		315	697	983	2,224
Equity in income		16,500	9,100	52,486	37,044
Gain on change in control of interests					71,160
Income from continuing operations		72,475	81,683	230,055	293,003
Gain on sale of operating properties/change in control of interests		28,250	40,533	180,461	62,102
Net income		100,725	122,216	410,516	355,105
Net income attributable to noncontrolling interests		(567)	(1,186)	(882)	(13,926)
Net income attributable to the Company		100,158	121,030	409,634	341,179
Preferred stock redemption charges			(7,014)		(7,014)
Preferred dividends		(14,534)	(12,059)	(43,657)	(35,169)
Net income available to the Company's common shareholders		$ 85,624	$ 101,957	$ 365,977	$ 298,996
Net income available to the Company:
-Basic (in dollars per share)		$ 0.19	$ 0.24	$ 0.86	$ 0.70
-Diluted (in dollars per share)		$ 0.19	$ 0.24	$ 0.85	$ 0.70
Weighted average shares:
-Basic (in shares)		419,230	423,688	421,106	423,574
-Diluted (in shares)	[1]	419,764	424,311	422,443	424,193
Joint Ventures [Member]
Other income/(expense)
Equity in income		$ 16,533	$ 9,142	$ 52,486	$ 37,044
Other Real Estate Investments [Member]
Other income/(expense)
Equity in income		5,045	19,909	24,638	61,952
Revenues from Rental Properties [Member]
Revenues
Revenues		215,049	225,836	668,115	679,321
Reimbursement Income [Member]
Revenues
Revenues		58,007	59,490	182,929	178,590
Other Rental Property Income [Member]
Revenues
Revenues		5,643	5,593	16,755	15,242
Management and Other Fee Incomes [Member]
Revenues
Revenues		$ 4,381	$ 3,926	$ 12,762	$ 12,456

[1] The effect of the assumed conversion of certain convertible units had an anti-dilutive effect upon the calculation of Income from continuing operations per share. Accordingly, the impact of such conversions has not been included in the determination of diluted earnings per share calculations. Additionally, there were 1.3 million and 2.3 million stock options that were not dilutive as of September 30, 2018 and 2017, respectively.