Earnings Per Share (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2016	Jun. 30, 2015	Jun. 30, 2016	Jun. 30, 2015
Basic Net Earnings Per Common Shares [Abstract]
Earnings from continuing operations	$ 19,862	$ 13,808	$ 32,518	$ 23,147
Loss from discontinued operation	(618)	(430)	(1,070)	(821)
Net earnings available to common stockholders	$ 19,244	$ 13,378	$ 31,448	$ 22,326
Weighted average common shares outstanding (in shares)	22,705,310	22,917,718	22,673,811	22,914,322
Earnings from continuing operations per common share (in dollars per share)	$ 0.87	$ 0.60	$ 1.43	$ 1.01
Loss from discontinued operations per common share (in dollars per share)	(0.02)	(0.02)	(0.04)	(0.04)
Net earnings per common share - Basic (in dollars per share)	$ 0.85	$ 0.58	$ 1.39	$ 0.97
Diluted Net Earnings Per Common Share [Abstract]
Earnings from continuing operations	$ 19,862	$ 13,808	$ 32,518	$ 23,147
Loss from discontinued operation	(618)	(430)	(1,070)	(821)
Net earnings available to common stockholders	$ 19,244	$ 13,378	$ 31,448	$ 22,326
Weighted average common shares outstanding (in shares)	22,705,310	22,917,718	22,673,811	22,914,322
Plus incremental shares from assumed conversions [Abstract]
Dilutive effect of restricted stock and performance-based stock (in shares)	314,000	343,000	315,000	342,000
Dilutive effect of stock options (in shares)	0	0	0	0
Weighted average common shares outstanding - Diluted (in shares)	23,018,730	23,261,094	22,988,502	23,256,255
Earnings from continuing operations per common share (in dollars per share)	$ 0.86	$ 0.59	$ 1.41	$ 1.00
Loss from discontinued operations per common share (in dollars per share)	(0.02)	(0.01)	(0.04)	(0.04)
Net earnings per common share - Diluted (in dollars per share)	$ 0.84	$ 0.58	$ 1.37	$ 0.96
Restricted and Performance Shares [Member]
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive securities excluded from computation of earnings per share (in shares)	338,000	331,000	341,000	347,000