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
	Mar. 31, 2021	Dec. 31, 2020	Mar. 31, 2020	Dec. 31, 2019
Earnings Per Share [Abstract]
Net income (loss) attributable to common stockholders	$ 35,332		$ 61,023
BASIC:
Weighted average common shares outstanding	45,305,087		44,613,593
Net income per common share - basic	$ 0.78		$ 1.37
DILUTED:
Weighted average common shares outstanding	45,305,087		44,613,593
Stock options	10,873		4,546
Convertible subordinated debentures	41,813		0
Weighed average dilutive common shares outstanding	45,357,773		44,618,139
Net income per common share - diluted	$ 0.78		$ 1.37
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	216,762		305,862
Common Stock, Dividends, Per Share, Declared	$ 1.1025	$ 1.1025	$ 1.1025	$ 1.10