Consolidated Statements of Changes in Shareholders' Equity (Unaudited) - USD ($) $ in Thousands	Capital Stock [Member]	Surplus [Member]	Undivided Profits [Member]	Accumulated Other Comprehensive (Loss) Income [Member]	Treasury Stock [Member]	Total
Balance at Dec. 31, 2014	$ 98,945	$ 172,353	$ 166,745	$ (4,509)	$ (40,090)	$ 393,444
Net income	0	0	21,442	0	0	21,442
Other comprehensive income (loss), net of tax	0	0	0	(1,418)	0	(1,418)
Cash dividend declared	0	0	(12,466)	0	0	(12,466)
Stock options exercised and related tax benefits	19	80	0	0	0	99
Purchase of treasury stock	0	0	0	0	(99)	(99)
Sale of treasury stock	0	(541)	0	0	1,902	1,361
Stock based compensation expense	0	96	0	0	0	96
Balance at Jun. 30, 2015	98,964	171,988	175,721	(5,927)	(38,287)	402,459
Balance at Mar. 31, 2015				(2,687)
Net income						10,727
Other comprehensive income (loss), net of tax						(3,240)
Balance at Jun. 30, 2015	98,964	171,988	175,721	(5,927)	(38,287)	402,459
Balance at Dec. 31, 2015	98,973	171,443	184,009	(4,781)	(36,334)	413,310
Net income	0	0	20,875	0	0	20,875
Other comprehensive income (loss), net of tax	0	0	0	7,176	0	7,176
Cash dividend declared	0	0	(12,528)	0	0	(12,528)
Stock options exercised and related tax benefits	98	404	0	0	0	502
Purchase of treasury stock	0	0	0	0	(489)	(489)
Sale of treasury stock	0	(785)	0	0	2,092	1,307
Stock based compensation expense	0	112	0	0	0	112
Balance at Jun. 30, 2016	99,071	171,174	192,356	2,395	(34,731)	430,265
Balance at Mar. 31, 2016				73
Net income						10,464
Other comprehensive income (loss), net of tax						2,322
Balance at Jun. 30, 2016	$ 99,071	$ 171,174	$ 192,356	$ 2,395	$ (34,731)	$ 430,265