Supplemental Cash Flow Information (Details) (USD $)	1 Months Ended	12 Months Ended
	Dec. 31, 2011 Parcels	Dec. 31, 2011 Land_Position	Dec. 31, 2011 Parcels	Dec. 31, 2010	Dec. 31, 2009	Dec. 31, 2008
Supplemental Cash Flow Information [Abstract]
Costs of share-based compensation awards			$ 8,900,000	$ 5,300,000	$ 5,800,000
Ownership interest received as part of a non-cash proceed from contribution			5,000,000	4,600,000	30,300,000
Debt and other liabilities in connection with acquisition and construction						61,700,000
Number of land parcels exchanged	3	3	3
Fair Value Of Land Parcels	10,900,000
Impairment of note receivable				$ 2,900,000