Federal Income Tax Considerations (Schedule Of Reconciling Net Income Adjusted For Noncontrolling Interests To REIT Taxable Income) (Details) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Income Tax Note [Line Items]
Net income adjusted for noncontrolling interests	$ 146,640	$ 15,621	$ 46,206
Net loss of taxable REIT subsidiary included above	11,457	32,043	22,450
Net income from REIT operations	158,097	47,664	68,656
Book depreciation and amortization including discontinued operations	148,413	157,290	151,108
Tax depreciation and amortization	(92,797)	(100,633)	(95,848)
Book/tax difference on gains/losses from capital transactions	(55,242)	(13,398)	1,233
Deferred/prepaid/above and below market rents, net	(4,264)	(13,088)	(5,076)
Impairment loss from REIT operations including discontinued operations	11,396	58,353	28,376
Other book/tax differences, net	1,430	(3,652)	(22,785)
REIT taxable income	167,033	132,536	125,664
Dividends paid deduction	(173,202)	(165,721)	(125,664)
Dividends paid in excess of taxable income	$ (6,169)	$ (33,185)	$ 0