Quarterly Financial Data (Unaudited) (Schedule Of Quarterly Financial Information) (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Acquired Finite-Lived Intangible Assets [Line Items]
Revenues	$ 119,465	$ 121,362	$ 122,660	$ 123,138	$ 127,819	$ 128,790	$ 142,086	$ 132,452	$ 486,625	$ 531,147	$ 573,163
Net Income	77,292	108,509	85,520	51,254	63,229	53,274	79,871	148,969	322,575	345,343	350,715
Net income attributable to common shareholders	$ 75,218	$ 106,742	$ 83,809	$ 49,666	$ 59,507	$ 42,981	$ 78,289	$ 146,824	$ 315,435	$ 327,601	$ 335,274
Net income attributable to common shareholders - basic (in dollars per share)	$ 0.59	$ 0.83	$ 0.66	$ 0.39	$ 0.47	$ 0.34	$ 0.61	$ 1.15	$ 2.47	$ 2.57	$ 2.62
Net income attributable to common shareholders - diluted (in dollars per share)	$ 0.58	$ 0.82	$ 0.65	$ 0.39	$ 0.46	$ 0.34	$ 0.61	$ 1.13	$ 2.44	$ 2.55	$ 2.60
Revenues associated with dispositions	$ 1,300	$ 4,300	$ 8,800	$ 9,700	$ 4,100	$ 7,000	$ 8,300	$ 11,900
Revenue from acquisitions	3,000	1,600	500
Gain on sale of property	46,000	74,100	$ 52,700	$ 19,200	34,800	19,800	48,200	111,400	$ 189,914	$ 207,865	$ 218,611
Impairment loss	$ 3,100				7,700	2,400			74	10,120	15,257
Gain (loss) on debt extinguishment								3,800		400
Net income attributable to noncontrolling interests					$ 1,900	$ 8,600		$ 500	$ 7,140	$ 17,742	$ 15,441
Above-Market and Below-Market Leases [Member]
Acquired Finite-Lived Intangible Assets [Line Items]
Amortization/(accretion)							(10,000)
Terminated Tenant Leases [Member]
Acquired Finite-Lived Intangible Assets [Line Items]
Revenues		$ 1,100
Leases, Acquired-in-Place [Member]
Acquired Finite-Lived Intangible Assets [Line Items]
Amortization/(accretion)							$ 13,100