Per Share Data (Calculation Of Basic And Diluted Earnings Per Share) (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended										12 Months Ended
	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2017	[1]	Sep. 30, 2017	[2]	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2018		Dec. 31, 2017		Dec. 31, 2016
Earnings Per Share [Abstract]
Number of common share equivalent securities excluded from the diluted earnings per share calculation											2,100		1,500		2,400
Income from continuing operations attributable to common shareholders											$ 156,128		$ 196,422		$ 436,981
Amount allocated to participating securities											(1,107)		(660)		(6,304)
Income from continuing operations attributable to common shareholders, net of amount allocated to participating securities											155,021		195,762		430,677
Discontinued operations, including gain on sale, attributable to common shareholders											0		0		382,842
Net income attributable to common shareholders - basic											$ 155,021		$ 195,762		$ 813,519
Earnings per common share from continuing operations											$ 1.63		$ 2.14		$ 4.81
Earnings per common share from discontinued operations											0.00		0.00		4.27
Total earnings per common share - basic	$ 0.41	$ 0.41	$ 0.40	$ 0.41	$ 0.92		$ 0.38		$ 0.43	$ 0.39	$ 1.63	[3]	$ 2.14	[3]	$ 9.08
Weighted average number of common shares outstanding – basic											95,208		91,499		89,580
Income allocated to common units from continuing operations											$ 0		$ 1,174		$ 0
Income from continuing operations attributable to common shareholders, as adjusted											155,021		196,936		430,677
Net income attributable to common shareholders - diluted											$ 155,021		$ 196,936		$ 813,519
Earnings per common share from continuing operations											$ 1.63		$ 2.13		$ 4.79
Earnings per common share from discontinued operations											0.00		0.00		4.26
Total earnings per common share - diluted	$ 0.41	$ 0.40	$ 0.40	$ 0.41	$ 0.91		$ 0.38		$ 0.43	$ 0.39	$ 1.63	[3]	$ 2.13	[3]	$ 9.05
Common share options and share awards granted											158		211		323
Common units										0	0		805
Weighted average number of common shares outstanding - diluted											95,366		92,515		89,903

[1] Includes a $43,231, or $0.46 basic and $0.45 diluted per share, impact related to a gain on sale of one operating property.

[2] Includes a $4,987, or $0.05 basic and diluted per share, impact related to expenses due to Hurricanes Harvey and Irma.

[3] Net income per share is computed independently for each of the quarters presented. Therefore, the sum of quarterly net income per share amounts may not equal the total computed for the year.