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		9 Months Ended
	Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2015	Sep. 30, 2014
Continuing Operations:
Income (loss) from continuing operations	$ 18,030	$ 6,650	$ (242,198)	$ 54,426
Plus: Gain on disposition of real estate	41,793	2,262	78,154	2,645
Plus: (Income) loss attributable to non-controlling interests	(268)	2,125	(1,590)	1,623
Less: Write-off of preferred share original issuance costs	0	0	0	(1,943)
Less: Preferred dividends	(5,594)	(5,594)	(16,781)	(18,460)
Less: Earnings attributable to unvested shares and operating partnership units	(221)	(463)	(1,075)	(1,238)
Income (loss) from continuing operations	53,740	4,980	(183,490)	37,053
Discontinued operations:
Income from discontinued operations	0	57,569	0	67,926
Plus: Loss attributable to non-controlling interests	0	0	0	1,362
Net income (loss) attributable to common shareholders after allocation to participating securities	$ 53,740	$ 62,549	$ (183,490)	$ 106,341
Denominators – Number of Shares
Basic—Average shares outstanding	361,107	358,025	360,341	357,824
Effect of dilutive securities:
Senior convertible notes	2,085	0	0	0
Stock options	379	487	0	468
Diluted—Average shares outstanding	363,571	358,512	360,341	358,292
Basic Earnings Per Share:
Income (loss) from continuing operations attributable to common shareholders	$ 0.15	$ 0.01	$ (0.51)	$ 0.10
Income from discontinued operations attributable to common shareholders	0	0.16	0	0.20
Net income (loss) attributable to common shareholders	0.15	0.17	(0.51)	0.30
Diluted Earnings Per Share:
Income (loss) from continuing operations attributable to common shareholders	0.15	0.01	(0.51)	0.10
Income from discontinued operations attributable to common shareholders	0	0.16	0	0.20
Net income (loss) attributable to common shareholders	$ 0.15	$ 0.17	$ (0.51)	$ 0.30