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		9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Jun. 30, 2021	Jun. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
Earnings Per Share [Abstract]
Net income (loss) attributable to common stockholders	$ 30,814	$ 42,595			$ 105,327	$ 147,986
BASIC:
Weighted average common shares outstanding	45,850,599	44,661,650			45,668,762	44,641,748
Net income per common share - basic	$ 0.67	$ 0.95			$ 2.31	$ 3.31
DILUTED:
Weighted average common shares outstanding	45,850,599	44,661,650			45,668,762	44,641,748
Stock options	825	753			6,391	1,766
Convertible subordinated debentures	0	0			13,938	0
Weighed average dilutive common shares outstanding	45,851,424	44,662,403			45,689,091	44,643,514
Net income per common share - diluted	$ 0.67	$ 0.95			$ 2.31	$ 3.31
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	505,459	410,012			308,313	427,180
Common Stock, Dividends, Per Share, Declared	$ 0.90	$ 1.1025	$ 2.0025	$ 2.2050	$ 2.9025	$ 3.3075