Supplemental Disclosures of Cash Flow Information (Details) (USD $)	3 Months Ended
	Mar. 31, 2012	Mar. 31, 2011
Supplemental Disclosures of Cash Flow Information [Abstract]
Interest paid	$ 50,500,000	$ 44,900,000
Interest capitalized to properties under development	145,000	71,000
Income taxes paid	588,000	834,000
Non-cash investing and financing activities [Abstract]
Share-based compensation expense	3,000,000	2,200,000
Increase In Buildings And Improvements And Accounts Payable	2,800,000	951,000
Loans receivable to fund development of real estate	$ 421,000