Earnings Per Share - Computation of Company's Earnings Per Share (EPS) and Reconciliation of Net Income (Loss) from Continuing Operations and Number of Common Shares Used in Computations of "Basic" EPS and "Diluted" EPS (Detail) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2016	Jun. 30, 2015	Jun. 30, 2016	Jun. 30, 2015
Earnings Per Share [Abstract]
Income (loss) from continuing operations	$ 27,647	$ 7,780	$ 61,139	$ (260,228)
Plus: Gain on disposition of real estate	13,721	11,267	26,102	36,361
Plus: Income attributable to non-controlling interests	(310)	(449)	(610)	(1,322)
Less: Preferred dividends	(5,594)	(5,594)	(11,188)	(11,188)
Less: Earnings attributable to unvested shares and operating partnership units	(204)	(420)	(414)	(868)
Net income (loss) attributable to common shareholders after allocation to participating securities	$ 35,260	$ 12,584	$ 75,029	$ (237,245)
Denominators – Number of Shares
Basic—Average shares outstanding	364,976	360,073	364,834	359,914
Effect of dilutive securities:
Stock options	342	443	346	0
Senior convertible notes	0	3,631	0	0
Diluted—Average shares outstanding	365,318	364,147	365,180	359,914
Earnings Per Share:
Basic	$ 0.10	$ 0.03	$ 0.21	$ (0.66)
Diluted	$ 0.10	$ 0.03	$ 0.21	$ (0.66)