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				9 Months Ended
	Sep. 30, 2020	Jun. 30, 2020	Sep. 30, 2019	Jun. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Earnings Per Share [Abstract]
Net income (loss) attributable to common stockholders	$ 42,595		$ 42,758		$ 147,986	$ 118,417
BASIC:
Weighted average common shares outstanding	44,661,650		43,505,332		44,641,748	43,187,847
Net income per common share - basic	$ 0.95		$ 0.98		$ 3.31	$ 2.74
DILUTED:
Weighted average common shares outstanding	44,661,650		43,505,332		44,641,748	43,187,847
Stock options	753		79,933		1,766	73,924
Convertible subordinated debentures	0		275,824		0	232,943
Weighed average dilutive common shares outstanding	44,662,403		43,861,089		44,643,514	43,494,714
Net income per common share - diluted	$ 0.95		$ 0.97		$ 3.31	$ 2.72
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	410,012		7,858		427,180	11,200
Common Stock, Dividends, Per Share, Declared	$ 1.1025	$ 1.1025	$ 1.05	$ 1.05	$ 3.3075	$ 3.15