Consolidated Statements of Changes in Shareholders' Equity - USD ($) $ in Thousands	Total	Common Stock [Member]	Additional Paid-in Capital [Member]	Retained Earnings [Member]	Accumulated Other Comprehensive (Loss)/Income [Member]	Treasury Stock [Member]
Balance at Dec. 31, 2013	$ 571,306	$ 77,993	$ 78,140	$ 468,158	$ (12,694)	$ (40,291)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	43,414			43,414
Other comprehensive income (loss), net of tax	5,522				5,522
Cash dividends declared	(14,858)			(14,858)
Treasury stock issued for restricted awards	(163)			(1,805)		1,642
Recognition of restricted stock compensation expense	676		676
Balance at Sep. 30, 2014	605,897	77,993	78,816	494,909	(7,172)	(38,649)
Balance at Dec. 31, 2014	608,389	77,993	78,818	504,060	(13,833)	(38,649)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	49,658			49,658
Other comprehensive income (loss), net of tax	4,097				4,097
Cash dividends declared	(17,886)			(17,886)
Common stock issued in acquisition	142,469	12,333	130,136
Treasury stock issued for restricted awards	(111)			(2,390)		2,279
Recognition of restricted stock compensation expense	1,266		1,266
Tax benefit from stock-based compensation	53		53
Common stock issuance costs	(132)		(132)
Balance at Sep. 30, 2015	$ 787,803	$ 90,326	$ 210,141	$ 533,442	$ (9,736)	$ (36,370)