Earnings Per Share (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2015	Jun. 30, 2014	Jun. 30, 2015	Jun. 30, 2014
Income from continuing operations	$ 298,504	$ 117,210	$ 488,573	$ 198,890
Allocation to Noncontrolling Interests - Operating Partnership, net	(11,350)	(4,422)	(18,403)	(7,475)
Net (income) attributable to Noncontrolling Interests – Partially Owned Properties	(844)	(588)	(1,487)	(1,092)
Preferred distributions	(833)	(1,036)	(1,724)	(2,072)
Premium on redemption of Preferred Shares	0	0	(2,789)	0
Income from continuing operations available to Common Shares, net of Noncontrolling Interests	285,477	111,164	464,170	188,251
Discontinued operations, net of Noncontrolling Interests	110	490	259	1,502
Numerator for net income per share - basic	285,587	111,654	464,429	189,753
Income from continuing operations available to Common Shares	296,827	115,586	482,573	195,726
Discontinued operations, net	114	510	269	1,562
Numerator for net income per share - diluted	$ 296,941	$ 116,096	$ 482,842	$ 197,288
Denominator for net income per share - basic	363,476	360,809	363,288	360,641
Effect of dilutive securities - OP Units	13,587	13,742	13,592	13,736
Effect of dilutive securities - Long-term compensation shares/units	3,428	2,567	3,466	2,403
Denominator for net income per share - diluted	380,491	377,118	380,346	376,780
Net income per share - basic	$ 0.79	$ 0.31	$ 1.28	$ 0.53
Net income per share - diluted	0.78	0.31	1.27	0.52
Income from continuing operations available to Common Shares	0.79	0.31	1.28	0.52
Net income per share - basic - Discontinued operations, net of Noncontrolling Interests	0.00	0.00	0.00	0.01
Income from continuing operations available to Common Shares	0.78	0.31	1.27	0.52
Net income per share - diluted - discontinued operations, net	$ 0.00	$ 0.00	$ 0.00	$ 0.00
OPERATING PARTNERSHIP
Income from continuing operations	$ 298,504	$ 117,210	$ 488,573	$ 198,890
Net (income) attributable to Noncontrolling Interests – Partially Owned Properties	(844)	(588)	(1,487)	(1,092)
Dividend preference units	(833)	(1,036)	(1,724)	(2,072)
Premium on redemption of Preferred Shares	0	0	(2,789)	0
Discontinued operations, net	$ 114	$ 510	$ 269	$ 1,562
Effect of dilutive securities - Long-term compensation shares/units	3,428	2,567	3,466	2,403
Net income per share - basic	$ 0.79	$ 0.31	$ 1.28	$ 0.53
Net income per share - diluted	0.78	0.31	1.27	0.52
Income from continuing operations available to Common Shares	0.79	0.31	1.28	0.52
Income from continuing operations available to Common Shares	$ 0.78	$ 0.31	$ 1.27	$ 0.52
Income from continuing operations available to Units	$ 296,827	$ 115,586	$ 482,573	$ 195,726
Numerator for net income per Unit - basic and diluted	$ 296,941	$ 116,096	$ 482,842	$ 197,288
Denominator for net income per Unit - basic	377,063	374,551	376,880	374,377
Weighted Average Number Of Limited Partnership And General Partnership Unit Outstanding Diluted	380,491	377,118	380,346	376,780
Net income per Unit - basic - Discontinued operations, net	$ 0.00	$ 0.00	$ 0.00	$ 0.01
Net income per Unit - diluted - Discontinued operations, net	$ 0.00	$ 0.00	$ 0.00	$ 0.00