Consolidated Statements Of Changes In Shareholders' Equity (USD $) In Thousands	Common Stock [Member]	Capital Surplus[Member]	Retained Earnings [Member]	Treasury Stock [Member]	Accumulated Other Comprehensive Income (Loss) [Member]	Total
Beginning balance at Dec. 31, 2010	$ 46,249	$ 103,057	$ 270,905	$ (102,853)	$ (2,497)	$ 314,861
Net income			31,024			31,024
Other comprehensive income					(204)	(204)
Cash dividends declared			(15,394)			(15,394)
Stock-based compensation expense, net		83		784		867
Exercise of stock options		(20)		188		168
Purchase of treasury shares				(21,430)		(21,430)
Ending balance at Sep. 30, 2011	46,249	103,120	286,535	(123,311)	(2,701)	309,892
Beginning balance at Dec. 31, 2011	46,249	103,335	291,050	(125,593)	(3,907)	311,134
Net income			28,049			28,049
Other comprehensive income					3,542	3,542
Acquisition of Virginia Savings Bancorp		276		7,447		7,723
Cash dividends declared			(15,532)			(15,532)
Stock-based compensation expense, net		(179)		1,049		870
Exercise of stock options		(121)		665		544
Purchase of treasury shares				(7,915)		(7,915)
Ending balance at Sep. 30, 2012	$ 46,249	$ 103,311	$ 303,567	$ (124,347)	$ (365)	$ 328,415