Common Stock (Basic And Diluted Earnings Per Share) (Details) (USD $) In Thousands, except Share data, unless otherwise specified	3 Months Ended		12 Months Ended
	Mar. 31, 2015	Mar. 31, 2014	Mar. 31, 2015	Mar. 31, 2014
Earnings Per Share [Abstract]
Basic number of common shares outstanding	40,243,199	40,149,083	40,214,198	40,132,106
Dilutive effect of unvested performance awards	23,475	0	26,595	12,053
Diluted number of common shares outstanding	40,266,674	40,149,083	40,240,793	40,144,159
Net income	$ 3,458	$ 4,615	$ 90,271	$ 85,564
Income allocated to participating restricted stock	(33)	(36)	(289)	(260)
Net income available to common shareholders, basic	3,425	4,579	89,982	85,304
Income reallocated to participating restricted stock	(33)	(36)	(289)	(260)
Net income available to common shareholders, diluted	$ 3,425	$ 4,579	$ 89,982	$ 85,304
Earnings Per Share, Basic, Distributed	$ 0.280	$ 0.265	$ 1.120	$ 1.060
Earnings Per Share, Basic, Undistributed	$ (0.190)	$ (0.155)	$ 1.120	$ 1.070
Basic net income per common share	$ 0.090	$ 0.110	$ 2.240	$ 2.130
Earnings Per Share, Diluted, Distributed	$ 0.280	$ 0.265	$ 1.120	$ 1.060
Earnings Per Sare, Diluted, Undistributed	$ (0.190)	$ (0.155)	$ 1.120	$ 1.060
Diluted net income per common share	$ 0.090	$ 0.110	$ 2.240	$ 2.120