Supplemental Cash Flow Information (Summary Of Non-Cash Investing And Financing Activities) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Noncash or Part Noncash Acquisitions [Line Items]
Accrued property construction costs	$ 7,728	$ 5,738	$ 9,566
Increase in equity for the acquisition of noncontrolling interests in consolidated real estate joint ventures	0	2,139	0
Exchange of operating partnership units for common shares	0	0	111
Reduction of debt service guaranty liability	(2,980)	(2,710)	(2,270)
Increase (decrease) in equity associated with deferred compensation plan (see Note 1)	44,758
Increase (decrease) in equity associated with deferred compensation plan (see Note 1)		(44,758)	0
Property Acquisitions And Investments In Unconsolidated Real Estate Joint Ventures [Member]
Noncash or Part Noncash Acquisitions [Line Items]
Increase in property, net	0	10,573	0
Decrease in real estate joint ventures and partnerships - investments	0	(2,315)	0
Increase in debt, net	0	0	20,966
Consolidation of Joint Venture [Member]
Noncash or Part Noncash Acquisitions [Line Items]
Increase in property, net	0	58,665	0
Increase in debt, net	0	48,727	0
Increase in security deposits	$ 0	$ 169	$ 0