Earnings Per Share - Computation of Company's Earnings Per Share (EPS) and Reconciliation of Net (Loss) Income 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								12 Months Ended
	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Continuing Operations:
(Loss) income from continuing operations									$ (12,187)	$ (237,881)	$ 21,107
Plus: Gain on disposition of real estate									73,386	167,571	3,060
Plus: (Income) loss attributable to non-controlling interests									(1,187)	(1,858)	2,356
Less: Write-off of preferred share original issuance costs									0	0	(1,943)
Less: Preferred dividends									(22,375)	(22,375)	(24,054)
Less: Earnings attributable to unvested shares and OP Units									(786)	(1,286)	(1,684)
Income (loss) from continuing operations									36,851	(95,829)	(1,158)
Discontinued operations:
Income from discontinued operations									0	0	89,398
Plus: Loss attributable to non-controlling interests									0	0	1,361
Net income (loss) attributable to common shareholders after allocation to participating securities									$ 36,851	$ (95,829)	$ 89,601
Denominators – Number of Shares
Basic—Average shares outstanding	365,965	365,508	364,976	364,691	362,734	361,107	360,073	359,818	365,294	360,946	358,122
Effect of dilutive securities—Stock options									267	0	0
Diluted—Average shares outstanding	366,075	365,508	365,318	365,042	365,197	363,571	364,147	359,818	365,561	360,946	358,122
Basic Earnings Per Share:
Income (loss) from continuing operations attributable to common shareholders									$ 0.10	$ (0.27)	$ 0.00
Income from discontinued operations attributable to common shareholders									0	0	0.25
Net income (loss) attributable to common shareholders	$ 0.08	$ (0.18)	$ 0.10	$ 0.11	$ 0.24	$ 0.15	$ 0.03	$ (0.69)	0.10	(0.27)	0.25
Diluted Earnings Per Share:
Income (loss) from continuing operations attributable to common shareholders									0.10	(0.27)	0.00
Income from discontinued operations attributable to common shareholders									0	0	0.25
Net income (loss) attributable to common shareholders	$ 0.08	$ (0.18)	$ 0.10	$ 0.11	$ 0.24	$ 0.15	$ 0.03	$ (0.69)	$ 0.10	$ (0.27)	$ 0.25