Mortgages, Loans Payable And Other Obligations (Narrative) (Details)	12 Months Ended
	Dec. 31, 2018 USD ($) property item	Dec. 31, 2017 USD ($)	Dec. 31, 2016 USD ($)
Debt Instrument [Line Items]
Cash paid for interest	$ 97,744,000	$ 103,559,000	$ 122,414,000
Interest capitalized	27,047,000	20,240,000	19,316,000
Total indebtedness	2,792,651,000
Adjusted total indebtedness	$ 2,807,396,000	$ 2,826,110,000
Total indebtedness, weighted average interest rate	3.89%	3.93%
Projects Under Development And Developable Land [Member]
Debt Instrument [Line Items]
Number of projects with encumbered company mortgages | item	1
Carrying value of encumbered properties	$ 142,000,000
Other Property [Member]
Debt Instrument [Line Items]
Number of properties with encumbered company mortgages | property	16
Carrying value of encumbered properties	$ 2,100,000,000
Unconsolidated Joint Venture [Member]
Debt Instrument [Line Items]
Interest capitalized	816,000	$ 1,056,000	$ 5,055,000
Revolving Credit Facility Borrowing And Other Variable Rate Mortgage Debt [Member]
Debt Instrument [Line Items]
Total indebtedness	$ 314,177,000	$ 382,443,000
Total indebtedness, weighted average interest rate	4.90%	3.63%
Fixed Rate Debt And Other Obligations [Member]
Debt Instrument [Line Items]
Total indebtedness	$ 2,493,219,000	$ 2,443,667,000
Total indebtedness, weighted average interest rate	3.76%	3.98%