Earnings Per Share (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2015	Jun. 30, 2014	Jun. 30, 2015	Jun. 30, 2014
Basic Net Earnings Per Common Shares [Abstract]
Earnings from continuing operations	$ 13,808	$ 11,169	$ 23,147	$ 23,576
Loss from discontinued operation	(430)	(529)	(821)	(1,211)
Net earnings available to common stockholders	$ 13,378	$ 10,640	$ 22,326	$ 22,365
Weighted average common shares outstanding (in shares)	22,917,718	22,874,002	22,914,322	22,910,419
Earnings from continuing operations per common share (in dollars per share)	$ 0.60	$ 0.49	$ 1.01	$ 1.03
Loss from discontinued operations per common share (in dollars per share)	(0.02)	(0.02)	(0.04)	(0.05)
Net earnings per common share - Basic (in dollars per share)	$ 0.58	$ 0.47	$ 0.97	$ 0.98
Diluted Net Earnings Per Common Share [Abstract]
Earnings from continuing operations	$ 13,808	$ 11,169	$ 23,147	$ 23,576
Loss from discontinued operation	(430)	(529)	(821)	(1,211)
Net earnings available to common stockholders	$ 13,378	$ 10,640	$ 22,326	$ 22,365
Plus incremental shares from assumed conversions [Abstract]
Dilutive effect of restricted stock and performance-based stock (in shares)	343,000	318,000	342,000	303,000
Dilutive effect of stock options (in shares)	0	5,000	0	6,000
Weighted average common shares outstanding - Diluted (in shares)	23,261,094	23,196,713	23,256,255	23,219,055
Earnings from continuing operations per common share (in dollars per share)	$ 0.59	$ 0.48	$ 1.00	$ 1.02
Loss from discontinued operations per common share (in dollars per share)	(0.01)	(0.02)	(0.04)	(0.06)
Net earnings per common share - Diluted (in dollars per share)	$ 0.58	$ 0.46	$ 0.96	$ 0.96
Stock Options [Member]
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive securities excluded from computation of earnings per share (in shares)	0	5,000	0	4,000
Restricted and Performance-based shares [Member]
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive securities excluded from computation of earnings per share (in shares)	331,000	295,000	347,000	300,000