Earnings Per Share (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016
Basic Net Earnings Per Common Share [Abstract]
Earnings from continuing operations	$ 18,261	$ 19,862	$ 34,628	$ 32,518
Loss from discontinued operations	(497)	(618)	(1,130)	(1,070)
Net earnings available to common stockholders	$ 17,764	$ 19,244	$ 33,498	$ 31,448
Weighted average common shares outstanding (in shares)	22,820,079	22,705,310	22,833,263	22,673,811
Earnings from continuing operations per common share (in dollars per share)	$ 0.80	$ 0.87	$ 1.52	$ 1.43
Loss from discontinued operations per common share (in dollars per share)	(0.02)	(0.02)	(0.05)	(0.04)
Net earnings per common share - Basic (in dollars per share)	$ 0.78	$ 0.85	$ 1.47	$ 1.39
Diluted Net Earnings Per Common Share [Abstract]
Earnings from continuing operations	$ 18,261	$ 19,862	$ 34,628	$ 32,518
Loss from discontinued operations	(497)	(618)	(1,130)	(1,070)
Net earnings available to common stockholders	$ 17,764	$ 19,244	$ 33,498	$ 31,448
Weighted average common shares outstanding (in shares)	22,820,079	22,705,310	22,833,263	22,673,811
Plus incremental shares from assumed conversions [Abstract]
Dilutive effect of restricted stock and performance-based stock (in shares)	509,000	314,000	499,000	315,000
Weighted average common shares outstanding - Diluted (in shares)	23,329,082	23,018,730	23,332,480	22,988,502
Earnings from continuing operations per common share (in dollars per share)	$ 0.78	$ 0.86	$ 1.48	$ 1.41
Loss from discontinued operations per common share (in dollars per share)	(0.02)	(0.02)	(0.04)	(0.04)
Net earnings per common share - Diluted (in dollars per share)	$ 0.76	$ 0.84	$ 1.44	$ 1.37
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)	228,000	338,000	240,000	341,000