Income Taxes - Reconciliation of Net Income (Loss) to Taxable Income (Detail) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Reconciliation Of Gaap Net Income Loss To Taxable Income Loss [Line Items]
Net income (loss) available to the Company	$ 83,939	$ 25,466	$ (6,960)
Add (subtract) net loss (income) of taxable REIT subsidiaries	(33,956)	(739)	11,145
Adjusted net income (loss) available to the Company	49,983	24,727	4,185
Book/tax depreciation difference	(2,555)	(3,863)	(1,693)
Book/tax difference on gains from real estate sales	1,718		(4,264)
Book/tax difference on stock-based compensation	(15,706)	(5,108)	(2,784)
Book/tax difference relating to real estate asset carrying values			(10,848)
Other book/tax differences, net	(1,090)	(3,761)	(1,707)
Taxable income of the Company before allocation of taxable capital gains	32,350	11,995	(17,111)
Income taxable as capital gains	(7,757)
Taxable ordinary income (loss) of the Company	$ 24,593	$ 11,995	$ (17,111)