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, 2016	Sep. 30, 2015	Sep. 30, 2016	Sep. 30, 2015
Earnings Per Share [Abstract]
Number of common share equivalent securities excluded from the diluted earnings per share calculation	2,400	2,600	2,500	2,600
Income from continuing operations attributable to common shareholders	$ 290,898	$ 32,137	$ 396,088	$ 173,890
Amount allocated to participating securities	(1,625)	(259)	(6,142)	(1,562)
Income from continuing operations attributable to common shareholders, net of amount allocated to participating securities	289,273	31,878	389,946	172,328
Income (Loss) from Discontinued Operations, Net of Tax, Attributable to Parent	0	4,907	382,842	14,832
Net income attributable to common shareholders – basic	$ 289,273	$ 36,785	$ 772,788	$ 187,160
Earnings per common share from continuing operations	$ 3.23	$ 0.36	$ 4.35	$ 1.93
Earnings per common share from discontinued operations	0.00	0.05	4.28	0.17
Total earnings per common share – basic	$ 3.23	$ 0.41	$ 8.63	$ 2.10
Weighted average number of common shares outstanding – basic	89,669	89,164	89,524	89,102
Net income attributable to common shareholders – diluted	$ 289,273	$ 36,785	$ 772,788	$ 187,160
Earnings per common share from continuing operations	$ 3.21	$ 0.36	$ 4.34	$ 1.93
Earnings per common share from discontinued operations	0.00	0.05	4.26	0.16
Total earnings per common share – diluted	$ 3.21	$ 0.41	$ 8.60	$ 2.09
Common share options and share awards granted	343	366	334	348
Weighted average number of common shares outstanding – diluted	90,012	89,530	89,858	89,450