Related Party Arrangements - Additional Information (Detail) (USD $)	3 Months Ended		9 Months Ended			3 Months Ended	9 Months Ended	3 Months Ended	9 Months Ended		12 Months Ended
	Sep. 30, 2011	Sep. 30, 2010	Sep. 30, 2011	Sep. 30, 2010	Dec. 31, 2010	Sep. 30, 2011 Restricted Stock	Sep. 30, 2011 Restricted Stock	Sep. 30, 2011 Deferred Stock Awards	Sep. 30, 2011 Deferred Stock Awards	Sep. 30, 2011 Non Employee Director	Dec. 31, 2010 Non Employee Director
Related Party Transaction [Line Items]
Fees earned from asset management, property management, development and redevelopment of unconsolidated real estate entities	$ 2,433,000	$ 1,800,000	$ 7,085,000	$ 5,334,000
Amount of outstanding receivables associated with management role of unconsolidated real estate entities	5,260,000		5,260,000		4,135,000
Non-employee director compensation expense			7,614,000	7,709,000		195,000	195,000	569,000	569,000
Amount of deferred compensation										$ 579,000	$ 312,000