Earnings Per Share (Computation 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, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Earnings Per Share [Abstract]
Net income	$ 103,858	$ 66,536	$ 279,906	$ 184,859
Preferred dividends	2,343	2,343	7,031	7,031
Net income available to common shareholders	$ 101,515	$ 64,193	$ 272,875	$ 177,828
Average shares used in basic computation	71,919	68,522	71,824	68,488
Dilutive effect of stock options and units	9,565	12,359	9,601	12,074
Average shares used in diluted computation	81,484	80,881	81,425	80,562
Basic	$ 1.41	$ 0.94	$ 3.80	$ 2.60
Diluted	$ 1.25	$ 0.79	$ 3.35	$ 2.21