Condensed Consolidated Statements of Income (Unaudited) - USD ($) shares in Thousands, $ in Thousands		3 Months Ended		6 Months Ended
		Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
Revenues		$ 293,403	$ 297,176	$ 597,481	$ 590,764
Operating expenses
Rent		2,742	2,765	5,560	5,548
Real estate taxes		37,274	38,747	77,708	77,016
Operating and maintenance		41,325	42,703	84,656	85,277
General and administrative		24,029	19,965	46,427	42,195
Provision for doubtful accounts		1,051	2,096	3,182	3,500
Impairment charges		22,873	29,719	30,519	31,336
Depreciation and amortization		79,760	95,270	161,142	187,344
Total operating expenses		209,054	231,265	409,194	432,216
Operating income		84,349	65,911	188,287	158,548
Other income, net		3,277	1,439	9,456	2,712
Interest expense		(46,434)	(46,090)	(96,377)	(92,572)
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		41,192	21,260	101,366	68,688
Benefit for income taxes, net		720	1,034	668	1,527
Equity in income of joint ventures, net		19,000	13,200	35,953	27,902
Gain on change in control of interests			60,972		71,160
Income from continuing operations		70,569	134,791	157,580	211,320
Gain on sale of operating properties/change in control of interests		95,240	19,883	152,211	21,569
Net income		165,809	154,674	309,791	232,889
Net income attributable to noncontrolling interests		(423)	(11,258)	(315)	(12,740)
Net income attributable to the Company		165,386	143,416	309,476	220,149
Preferred dividends		(14,534)	(11,555)	(29,123)	(23,110)
Net income available to the Company's common shareholders		$ 150,852	$ 131,861	$ 280,353	$ 197,039
Net income available to the Company:
-Basic (in dollars per share)		$ 0.36	$ 0.31	$ 0.66	$ 0.46
-Diluted (in dollars per share)		$ 0.36	$ 0.31	$ 0.66	$ 0.46
Weighted average shares:
-Basic (in shares)		420,731	423,650	422,060	423,516
-Diluted (in shares)	[1]	421,928	424,944	423,236	424,084
Joint Ventures [Member]
Operating expenses
Equity in income of joint ventures, net		$ 19,040	$ 13,169	$ 35,953	$ 27,902
Other Real Estate Investments [Member]
Operating expenses
Equity in income of joint ventures, net		9,617	38,356	19,593	42,043
Revenues from Rental Properties [Member]
Revenues		222,651	225,774	453,066	453,485
Reimbursement Income [Member]
Revenues		61,206	60,971	124,922	119,100
Other Rental Property Income [Member]
Revenues		5,526	6,098	11,112	9,649
Management and Other Fee Incomes [Member]
Revenues		$ 4,020	$ 4,333	$ 8,381	$ 8,530

[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 3.2 million and 4.0 million stock options that were not dilutive as of June 30, 2018 and 2017, respectively, and 2.3 million shares of restricted stock that were not dilutive for the three months ended June 30, 2018.