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
	Mar. 31, 2016	Mar. 31, 2015
Earnings Per Share [Abstract]
Income (loss) from continuing operations	$ 33,492	$ (268,008)
Plus: Gain on disposition of real estate	12,381	25,094
Plus: Income attributable to non-controlling interests	(300)	(873)
Less: Preferred dividends	(5,594)	(5,594)
Less: Earnings attributable to unvested shares and operating partnership units	(210)	(437)
Net income (loss) attributable to common shareholders after allocation to participating securities	$ 39,769	$ (249,818)
Denominators – Number of Shares
Basic—Average shares outstanding	364,691	359,818
Effect of dilutive securities:
Stock options	351	0
Diluted—Average shares outstanding	365,042	359,818
Earnings Per Share:
Basic	$ 0.11	$ (0.69)
Diluted	$ 0.11	$ (0.69)