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, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Earnings Per Share [Abstract]
Net income	$ 66,536	$ 17,814	$ 184,859	$ 54,640
Preferred dividends	2,343	1,563	7,031	1,563
Net income available to common shareholders	$ 64,193	$ 16,251	$ 177,828	$ 53,077
Average shares used in basic computation	68,522	66,482	68,488	66,950
Dilutive effect of stock options and units	12,359	11,062	12,074	9,662
Average shares used in diluted computation	80,881	77,544	80,562	76,612
Basic	$ 0.94	$ 0.24	$ 2.60	$ 0.79
Diluted	$ 0.79	$ 0.21	$ 2.21	$ 0.69