Earnings Per Share (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended										12 Months Ended
	Dec. 31, 2015	[1]	Sep. 30, 2015	[2]	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Computation of basic and diluted earnings per share
Numerator for basic and diluted earnings per share - net income attributable to common stockholders	$ 132,929		$ 182,043		$ 312,573	$ 190,799	$ 188,639	$ 136,255	$ 71,829	$ 50,022	$ 818,344	$ 446,745	$ 78,714
Basic											348,240,000	306,272,000	276,929,000
Effect of dilutive securities:
Employee stock options											143,000	188,000	226,000
Non-vested restricted shares											535,000	500,000	457,000
Redeemable shares											310,000	0	0
Convertible senior unsecured notes											196,000	787,000	1,149,000
Dilutive potential common shares											1,184,000	1,475,000	1,832,000
Diluted											349,424,000	307,747,000	278,761,000
Basic earnings per share	$ 0.38		$ 0.52		$ 0.89	$ 0.57	$ 0.58	$ 0.44	$ 0.24	$ 0.17	$ 2.35	$ 1.46	$ 0.28
Diluted earnings per share	$ 0.37		$ 0.52		$ 0.89	$ 0.56	$ 0.57	$ 0.44	$ 0.24	$ 0.17	$ 2.34	$ 1.45	$ 0.28
Earnings Per Share (Textuals) [Abstract]
Securities Excluded From Computation Of Diluted Earnings Per Share											0	0	0

[1] The decrease in net income and amounts per share are primarily attributable to the other than temporary impairment charge of $35,648,000 recognized on the available-for-sale investment and increased transaction costs incurred due to fourth quarter acquisitions.

[2] The decrease in net income and amounts per share are primarily attributable to gains on sales of real estate of $190,111,000 for the second quarter as compared to gains of $2,046,000 for the third quarter.