Consolidated Statements of Changes in Shareholders' Equity (Unaudited) - USD ($) $ in Thousands	Capital Stock [Member]	Surplus [Member]	Undivided Profits [Member]	Accumulated Other Comprehensive Loss [Member]	Treasury Stock [Member]	Total
Balance at Dec. 31, 2013	$ 98,927	$ 173,144	$ 147,432	$ (13,803)	$ (43,887)	$ 361,813
Net income	0	0	33,533	0	0	33,533
Other comprehensive income (loss), net of tax	0	0	0	10,295	0	10,295
Cash dividend declared	0	0	(18,639)	0	0	(18,639)
Stock options exercised and related tax benefits	15	63	0	0	0	78
Sale of treasury stock	0	(869)	0	0	3,016	2,147
Stock based compensation expense	0	260	0	0	0	260
Balance at Sep. 30, 2014	98,942	172,598	162,326	(3,508)	(40,871)	389,487
Balance at Dec. 31, 2014	98,945	172,353	166,745	(4,509)	(40,090)	393,444
Net income	0	0	32,058	0	0	32,058
Other comprehensive income (loss), net of tax	0	0	0	3,335	0	3,335
Cash dividend declared	0	0	(18,710)	0	0	(18,710)
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	(789)	0	0	2,810	2,021
Stock based compensation expense	0	144	0	0	0	144
Balance at Sep. 30, 2015	$ 98,964	$ 171,788	$ 180,093	$ (1,174)	$ (37,379)	$ 412,292