Per Share Data (Calculation Of Basic And Diluted Earnings Per Share) (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Earnings Per Share [Abstract]
Number of common share equivalent securities excluded from the diluted earnings per share calculation	1,400	1,600
Income from continuing operations attributable to common shareholders	$ 39,395	$ 34,861
Amount allocated to participating securities	(265)	(38)
Income from continuing operations attributable to common shareholders, net of amount allocated to participating securities	39,130	34,823
Net income attributable to common shareholders – basic	$ 39,130	$ 34,823
Total earnings per common share – basic	$ 0.41	$ 0.39
Income allocated to common units from continuing operations	$ 297	$ 273
Net income attributable to common shareholders – diluted	$ 39,427	$ 35,096
Total earnings per common share – diluted	$ 0.41	$ 0.39
Weighted average number of common shares outstanding – basic	95,067	89,925
Common share options and share awards granted	174	218
Common units	805	806
Weighted average number of common shares outstanding – diluted	96,046	90,949