Common Stock (Basic And Diluted Earnings Per Share) (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended		12 Months Ended
	Mar. 31, 2017	Mar. 31, 2016	Mar. 31, 2017	Mar. 31, 2016
Earnings Per Share [Abstract]
Basic number of common shares outstanding	40,387,235	40,325,324	40,366,024	40,295,316
Dilutive effect of unvested performance awards	0	0	69,665	36,824
Diluted number of common shares outstanding	40,387,235	40,325,324	40,435,689	40,332,140
Net income (loss)	$ (3,989)	$ (5,808)	$ 98,587	$ 72,652
Income allocated to participating restricted stock	(45)	(32)	(349)	(209)
Net income (loss) available to common shareholders, basic	(4,034)	(5,840)	98,238	72,443
Income reallocated to participating restricted stock	(45)	(32)	(349)	(209)
Net income (loss) available to common shareholders, diluted	$ (4,034)	$ (5,840)	$ 98,238	$ 72,443
Earnings Per Share, Basic, Distributed	$ 0.31	$ 0.295	$ 1.24	$ 1.18
Earnings (losses) Per Share, Basic, Undistributed	(0.41)	(0.435)	1.19	0.62
Basic net income (loss) per common share	(0.10)	(0.140)	2.43	1.80
Earnings Per Share, Diluted, Distributed	0.31	0.295	1.24	1.18
Earnings (losses) Per Share, Diluted, Undistributed	(0.41)	(0.435)	1.19	0.62
Diluted net income (loss) per common share	$ (0.10)	$ (0.140)	$ 2.43	$ 1.80