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	28,753			28,753
Other comprehensive income (loss), net of tax	6,668				6,668
Cash dividends declared	(9,810)			(9,810)
Treasury stock issued for restricted awards	(160)			(1,824)		1,664
Recognition of restricted stock compensation expense	430		430
Balance at Jun. 30, 2014	597,187	77,993	78,570	485,277	(6,026)	(38,627)
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	31,023			31,023
Other comprehensive income (loss), net of tax	312				312
Cash dividends declared	(11,608)			(11,608)
Common stock issued in acquisition	142,469	12,333	130,136
Treasury stock issued for restricted awards	(111)			(2,419)		2,308
Recognition of restricted stock compensation expense	858		858
Tax benefit from stock-based compensation	29		29
Issuance costs	(132)		(132)
Balance at Jun. 30, 2015	$ 771,229	$ 90,326	$ 209,709	$ 521,056	$ (13,521)	$ (36,341)