Earnings Per Share (Computation 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]
Net income	$ 88,761	$ 65,512
Preferred dividends	2,344	2,344
Net income available to common shareholders	$ 86,417	$ 63,168
Average shares used in basic computation	71,999	68,386
Dilutive effect of stock options and units	9,790	12,309
Average shares used in diluted computation	81,789	80,695
Basic	$ 1.20	$ 0.92
Diluted	$ 1.06	$ 0.78