Earnings and Dividends Per Share (Summary Of Calculation Of Basic And Diluted Earnings Per Share) (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended				6 Months Ended
	Jun. 30, 2020	Mar. 31, 2020	Jun. 30, 2019	Mar. 31, 2019	Jun. 30, 2020	Jun. 30, 2019
Earnings Per Share [Abstract]
Net income (loss) attributable to common stockholders	$ 44,368		$ 39,979		$ 105,392	$ 75,658
BASIC:
Weighted average common shares outstanding	44,650,002		43,232,384		44,631,797	43,029,104
Net income per common share - basic	$ 0.99		$ 0.92		$ 2.36	$ 1.76
DILUTED:
Weighted average common shares outstanding	44,650,002		43,232,384		44,631,797	43,029,104
Stock options	0		66,145		2,273	70,920
Convertible subordinated debentures	0		199,492		0	211,503
Weighed average dilutive common shares outstanding	44,650,002		43,498,021		44,634,070	43,311,527
Net income per common share - diluted	$ 0.99		$ 0.92		$ 2.36	$ 1.75
Incremental shares excluded since anti-dilutive:
Net share effect of stock options with an exercise price in excess of the average market price for our common shares	610,367		40,173		439,962	21,227
Common Stock, Dividends, Per Share, Declared	$ 1.1025	$ 1.1025	$ 1.05	$ 1.05	$ 2.205	$ 2.10