Common Stock (Basic And Diluted Earnings Per Share) (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended		12 Months Ended
	Mar. 31, 2020	Mar. 31, 2019	Mar. 31, 2020	Mar. 31, 2019
Earnings Per Share [Abstract]
Basic number of common shares outstanding	40,653,326	40,582,936	40,623,151	40,543,986
Dilutive effect of unvested performance awards	0	80,817	68,810	117,242
Diluted number of common shares outstanding	40,653,326	40,663,753	40,691,961	40,661,228
Net income (loss)	$ (35,209)	$ 6,089	$ 81,739	$ 97,370
Income allocated to participating restricted stock	(43)	(47)	(250)	(340)
Net income (loss) available to common shareholders, basic	(35,252)	6,042	81,489	97,030
Income reallocated to participating restricted stock	(43)	(47)	(250)	(339)
Net income (loss) available to common shareholders, diluted	$ (35,252)	$ 6,042	$ 81,489	$ 97,031
Earnings Per Share, Basic, Distributed	$ 0.385	$ 0.36	$ 1.54	$ 1.44
Earnings (losses) Per Share, Basic, Undistributed	(1.255)	(0.21)	0.47	0.95
Basic net income (loss) per common share	(0.870)	0.15	2.01	2.39
Earnings Per Share, Diluted, Distributed	0.385	0.36	1.54	1.44
Earnings (losses) Per Share, Diluted, Undistributed	(1.255)	(0.21)	0.46	0.95
Diluted net income (loss) per common share	$ (0.870)	$ 0.15	$ 2.00	$ 2.39