Loss Per Common Share / Unit - Schedule of Earnings Per Share Basic and Diluted by Common Class (Detail) (USD $) In Thousands, except Per Share data, unless otherwise specified	3 Months Ended								12 Months Ended
	Dec. 31, 2012	Sep. 30, 2012	Jun. 30, 2012	Mar. 31, 2012	Dec. 31, 2011	Sep. 30, 2011	Jun. 30, 2011	Mar. 31, 2011	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Summary Of Computation Of Basic And Diluted Earnings Per Share [Line Items]
Net loss attributable to common stockholders	$ (228,713)	$ (46,526)	$ (8,119)	$ 202,412	$ (45,459)	$ 55,436	$ (151,471)	$ (46,616)	$ (80,946)	$ (188,110)	$ (1,295,920)
REIT [Member]
Summary Of Computation Of Basic And Diluted Earnings Per Share [Line Items]
Net loss attributable to common stockholders									(80,946)	(188,110)	(1,295,920)
Weighted average common partnership units outstanding - Basic and Diluted									459,895	370,534	219,515
Net loss per share attributable to common stockholders - Basic and Diluted									$ (0.18)	$ (0.51)	$ (5.90)
Operating Partnership [Member]
Summary Of Computation Of Basic And Diluted Earnings Per Share [Line Items]
Net loss attributable to common stockholders									$ (81,108)	$ (188,459)	$ (1,295,920)
Weighted average common partnership units outstanding - Basic and Diluted									461,848	371,730	219,515
Net loss per share attributable to common stockholders - Basic and Diluted									$ (0.18)	$ (0.51)	$ (5.90)