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, 2019	[1]	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
Earnings Per Share [Abstract]
Number of common share equivalent securities excluded from the diluted earnings per share calculation										1,100		2,100		1,500
Income (Loss) from Continuing Operations, Net of Tax, Attributable to Parent										$ 219,623		$ 156,128		$ 196,422
Amount allocated to participating securities										(539)		(1,107)		(660)
Net Income (Loss) Available to Common Stockholders, Basic										$ 219,084		$ 155,021		$ 195,762
Total earnings per common share - basic	$ 0.96		$ 0.44	$ 0.43	$ 0.40	$ 0.41	$ 0.41	$ 0.40	$ 0.41	$ 2.23	[2]	$ 1.63	[2]	$ 2.14
Weighted average number of common shares outstanding – basic										98,460		95,208		91,499
Income allocated to common units from continuing operations										$ 1,593		$ 0		$ 1,174
Net income attributable to common shareholders - diluted										$ 220,677		$ 155,021		$ 196,936
Total earnings per common share - diluted	$ 0.95		$ 0.44	$ 0.43	$ 0.40	$ 0.41	$ 0.40	$ 0.40	$ 0.41	$ 2.22	[2]	$ 1.63	[2]	$ 2.13
Common share options and share awards granted										119		158		211
Common units										805		0		805
Weighted average number of common shares outstanding - diluted										99,384		95,366		92,515

[1] Includes a $11,995 or $0.12 basic and diluted per share, impact related to the loss on early retirement of debt in October 2019. Also includes a $49,901 or $0.50 basic and $0.49 diluted per share, impact related to a gain on sale of two consolidated operating properties.

[2] 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.