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, 2015	Jun. 30, 2014	Jun. 30, 2015	Jun. 30, 2014
Continuing Operations:
Income (loss) from continuing operations	$ 7,780	$ 68,078	$ (260,228)	$ 47,777
Plus: Gain on disposition of real estate	11,267	1,472	36,361	383
Plus: Income attributable to non-controlling interests	(449)	(347)	(1,322)	(501)
Less: Write-off of preferred share original issuance costs	0	(1,943)	0	(1,943)
Less: Preferred dividends	(5,594)	(6,259)	(11,188)	(12,867)
Less: Earnings attributable to unvested shares and operating partnership units	(420)	(464)	(868)	(777)
Income (loss) from continuing operations	12,584	60,537	(237,245)	32,072
Discontinued operations:
Income from discontinued operations	0	7,345	0	10,357
Plus: (Income) loss attributable to non-controlling interests	0	(531)	0	1,361
Net income (loss) attributable to common shareholders after allocation to participating securities	$ 12,584	$ 67,351	$ (237,245)	$ 43,790
Denominators – Number of Shares
Basic—Average shares outstanding	360,073	357,812	359,914	357,717
Effect of dilutive securities:
Senior convertible notes	3,631	0	0	0
Stock options	443	483	0	459
Diluted—Average shares outstanding	364,147	358,295	359,914	358,176
Basic Earnings Per Share:
Income (loss) from continuing operations attributable to common shareholders	$ 0.03	$ 0.17	$ (0.66)	$ 0.09
Income from discontinued operations attributable to common shareholders	0	0.02	0	0.03
Net income (loss) attributable to common shareholders	0.03	0.19	(0.66)	0.12
Diluted Earnings Per Share:
Income (loss) from continuing operations attributable to common shareholders	0.03	0.17	(0.66)	0.09
Income from discontinued operations attributable to common shareholders	0	0.02	0	0.03
Net income (loss) attributable to common shareholders	$ 0.03	$ 0.19	$ (0.66)	$ 0.12

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, 2015

Jun. 30, 2014

Jun. 30, 2015

Jun. 30, 2014

Continuing Operations:

Income (loss) from continuing operations

$ 7,780

$ 68,078

$ (260,228)

$ 47,777