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, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Continuing Operations:
Loss from continuing operations									$ (404,296)	$ (12,187)	$ (237,881)
Plus: Gain on disposition of real estate									161,164	73,386	167,571
Loss (income) attributable to non-controlling interests, net									1,447	(1,187)	(1,858)
Less: Preferred dividends									(28,759)	(22,375)	(22,375)
Less: Earnings attributable to unvested shares and OP Units									(989)	(786)	(1,286)
Net (loss) income attributable to common shareholders after allocation to participating securities									$ (271,433)	$ 36,851	$ (95,829)
Denominators – Number of Shares
Basic – Average shares outstanding	368,320	367,686	366,987	366,430	365,965	365,508	364,976	364,691	367,362	365,294	360,946
Effect of dilutive securities – Stock options									0	267	0
Diluted – Average shares outstanding	368,320	367,686	367,030	366,430	366,075	365,508	365,318	365,042	367,362	365,561	360,946
(Loss) Earnings Per Share:
Basic	$ (0.62)	$ (0.02)	$ 0.06	$ (0.16)	$ 0.08	$ (0.18)	$ 0.10	$ 0.11	$ (0.74)	$ 0.10	$ (0.27)
Diluted	$ (0.62)	$ (0.02)	$ 0.06	$ (0.16)	$ 0.08	$ (0.18)	$ 0.10	$ 0.11	$ (0.74)	$ 0.10	$ (0.27)