Per Share Data (Calculation Of Basic And Diluted Earnings Per Share) (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Earnings Per Share [Abstract]
Number of common share equivalent securities excluded from the diluted earnings per share calculation	2,000	1,900	2,000	1,900
Income from continuing operations attributable to common shareholders	$ 34,957	$ 43,597	$ 94,718	$ 124,609
Amount allocated to participating securities	(74)	(89)	(204)	(284)
Net income attributable to common shareholders – basic	$ 34,883	$ 43,508	$ 94,514	$ 124,325
Total earnings per common share – basic	$ 0.35	$ 0.44	$ 0.95	$ 1.27
Net income attributable to common shareholders – diluted	$ 34,883	$ 43,508	$ 94,514	$ 124,325
Total earnings per common share – diluted	$ 0.35	$ 0.44	$ 0.95	$ 1.26
Weighted average number of common shares outstanding – basic	99,419	98,959	99,372	98,259
Common share options and share awards granted	36	107	42	116
Weighted average number of common shares outstanding – diluted	99,455	99,066	99,414	98,375