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
Balances, beginning value at Dec. 31, 2009	$ 46,249	$ 102,917	$ 253,167	$ (90,877)	$ (2,554)	$ 308,902
Comprehensive income:
Net income			29,051			29,051
Other comprehensive gain, net of deferred income taxes
Net unrealized gain (loss) on available-for-sale securities, net of taxes					7,329	7,329
Net unrealized loss on interest rate floors, net of taxes					(2,277)	(2,277)
Total comprehensive income						34,103
Cash dividends declared ($1.02 per share)			(15,952)			(15,952)
Issuance of stock awards, net		(38)		682		644
Exercise of stock options		(12)		58		46
Purchase of treasury shares				(12,902)		(12,902)
Balances, Ending Value at Sep. 30, 2010	46,249	102,867	266,266	(103,039)	2,498	314,841
Balances, beginning value at Dec. 31, 2010	46,249	103,057	270,905	(102,853)	(2,497)	314,861
Comprehensive income:
Net income			31,024			31,024
Other comprehensive gain, net of deferred income taxes
Net unrealized gain (loss) on available-for-sale securities, net of taxes					91	91
Net unrealized loss on interest rate floors, net of taxes					(295)	(295)
Total comprehensive income						30,820
Cash dividends declared ($1.02 per share)			(15,394)			(15,394)
Issuance of stock awards, net		83		784		867
Exercise of stock options		(20)		188		168
Purchase of treasury shares				(21,430)		(21,430)
Balances, Ending Value at Sep. 30, 2011	$ 46,249	$ 103,120	$ 286,535	$ (123,311)	$ (2,701)	$ 309,892