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, 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, 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	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, net of tax						2,322
Balance at Jun. 30, 2016	99,071	171,174	192,356	2,395	(34,731)	430,265
Balance at Dec. 31, 2016	99,214	171,425	201,517	(6,251)	(33,219)	432,686
Net income	0	0	23,187	0	0	23,187
Other comprehensive income, net of tax	0	0	0	2,658	0	2,658
Cash dividend declared	0	0	(12,592)	0	0	(12,592)
Stock options exercised	297	1,298	0	0	0	1,595
Purchase of treasury stock	0	0	0	0	(1,503)	(1,503)
Sale of treasury stock	0	(199)	0	0	1,455	1,256
Stock based compensation expense	0	79	0	0	0	79
Balance at Jun. 30, 2017	99,511	172,603	212,112	(3,593)	(33,267)	447,366
Balance at Mar. 31, 2017				(5,568)
Net income						12,240
Other comprehensive income, net of tax						1,975
Balance at Jun. 30, 2017	$ 99,511	$ 172,603	$ 212,112	$ (3,593)	$ (33,267)	$ 447,366