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, 2015	Sep. 30, 2014	Sep. 30, 2015	Sep. 30, 2014
Earnings Per Share [Abstract]
Number of common share equivalent securities excluded from the diluted earnings per share calculation	1,800	1,900	2,600	2,000
Net income attributable to common shareholders	$ 37,044	$ 38,283	$ 188,722	$ 113,591
Amount allocated to participating securities	(259)	(317)	(1,562)	(970)
Net income attributable to common shareholders – basic	$ 36,785	$ 37,966	$ 187,160	$ 112,621
Earnings per common share – basic	$ 0.41	$ 0.43	$ 2.10	$ 1.28
Weighted average number of common shares outstanding – basic	89,164	88,146	89,102	87,882
Income allocated to common units	$ 292	$ 313	$ 0	$ 937
Net income attributable to common shareholders – diluted	$ 37,077	$ 38,279	$ 187,160	$ 113,558
Earnings per common share – diluted	$ 0.41	$ 0.43	$ 2.09	$ 1.28
Common share options and share awards granted	366	396	348	358
Common units	811	811	0	812
Weighted average number of common shares outstanding – diluted	90,341	89,353	89,450	89,052