Quarterly Financial Data (Unaudited) (Schedule Of Quarterly Financial Information) (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Acquired Finite-Lived Intangible Assets [Line Items]
Revenues	$ 127,819	$ 128,790	$ 142,086	$ 132,452	$ 139,367	$ 144,110	$ 146,023	$ 143,663	$ 531,147	$ 573,163	$ 549,555
Net Income	63,229	53,274	79,871	148,969	170,653	74,473	69,193	36,396	345,343	350,715	276,831
Net income attributable to common shareholders	$ 59,507	$ 42,981	$ 78,289	$ 146,824	$ 167,967	$ 72,629	$ 63,852	$ 30,826	$ 327,601	$ 335,274	$ 238,933
Net income attributable to common shareholders - basic (in dollars per share)	$ 0.47	$ 0.34	$ 0.61	$ 1.15	$ 1.31	$ 0.57	$ 0.50	$ 0.24	$ 2.57	$ 2.62	$ 1.90
Net income attributable to common shareholders - diluted (in dollars per share)	$ 0.46	$ 0.34	$ 0.61	$ 1.13	$ 1.30	$ 0.56	$ 0.49	$ 0.24	$ 2.55	$ 2.60	$ 1.87
Revenues associated with dispositions	$ 4,100	$ 7,000	$ 8,300	$ 11,900
Gain on sale of property	34,800	19,800	48,200	111,400	$ 136,300	$ 38,600	$ 34,200	$ 15,800	$ 207,865	$ 218,611	$ 100,714
Gain (loss) on debt extinguishment				3,800					400
Lease termination fee								3,100	90,554	109,310	98,855
Impairment loss	7,700	2,400						15,000	10,120	15,257	98
Net income attributable to noncontrolling interests	$ 1,900	$ 8,600		$ 500			$ 3,600	3,900	$ 17,742	$ 15,441	$ 37,898
Deferred income tax expense (benefit)					$ 1,500			$ (3,300)
Above-Market and Below-Market Leases [Member]
Acquired Finite-Lived Intangible Assets [Line Items]
Amortization/(accretion)			(10,000)
Leases, Acquired-in-Place [Member]
Acquired Finite-Lived Intangible Assets [Line Items]
Amortization/(accretion)			$ 13,100