Consolidated Statements Of Changes In Shareholders' Equity (USD $) In Thousands, except Share data, unless otherwise specified	Total	Common Stock	Retained Earnings	Accumulated Other Comprehensive Income (Loss)
Beginning Balance at Dec. 31, 2009	$ 190,561	$ 50,062	$ 133,634	$ 6,865
Beginning Balance (in shares) at Dec. 31, 2009		7,644,837
Net Income	24,766		24,766
Other comprehensive income, net of tax:
Change in fair value of securities available for sale	(854)			(854)
Change in fair value of cash flow hedges	(1,448)			(1,448)
Change in net unrecognized losses on postretirement plans	(234)			(234)
Comprehensive Income	22,230			(2,536)
Stock-based compensation expense	809	809
Exercise of stock options and issuance of restricted stock, net of repurchase for tax withholdings and tax benefit (in shares)		16,251
Exercise of stock options and issuance of restricted stock, net of repurchase for tax withholdings and tax benefit	114	114
Common stock repurchased (in shares)		(2,592)
Common stock repurchased	(49)	(49)
Cash dividends declared ($0.75 per share)	(7,670)		(7,670)
Ending Balance at Dec. 31, 2010	205,995	50,936	150,730	4,329
Ending Balance (in shares) at Dec. 31, 2010		7,658,496
Net Income	26,177		26,177
Other comprehensive income, net of tax:
Change in fair value of securities available for sale	4,899			4,899
Change in fair value of cash flow hedges	(6,555)			(6,555)
Change in net unrecognized losses on postretirement plans	(612)			(612)
Comprehensive Income	23,909			(2,268)
Stock-based compensation expense	1,025	1,025
Exercise of stock options and issuance of restricted stock, net of repurchase for tax withholdings and tax benefit (in shares)		19,723
Exercise of stock options and issuance of restricted stock, net of repurchase for tax withholdings and tax benefit	(134)	(134)
Common stock repurchased (in shares)		(13,244)
Common stock repurchased	(389)	(389)
Cash dividends declared ($0.75 per share)	(11,530)		(11,530)
Ending Balance at Dec. 31, 2011	218,876	51,438	165,377	2,061
Ending Balance (in shares) at Dec. 31, 2011		7,664,975
Net Income	23,428		23,428
Other comprehensive income, net of tax:
Change in fair value of securities available for sale	1,815			1,815
Change in fair value of cash flow hedges	59			59
Change in net unrecognized losses on postretirement plans	(938)			(938)
Comprehensive Income	24,364			936
Stock-based compensation expense	538	538
Exercise of stock options and issuance of restricted stock, net of repurchase for tax withholdings and tax benefit (in shares)		23,355
Exercise of stock options and issuance of restricted stock, net of repurchase for tax withholdings and tax benefit	(212)	(212)
Common stock repurchased (in shares)		(65,580)
Common stock repurchased	(2,097)	(2,097)
Cash dividends declared ($0.75 per share)	(7,654)		(7,654)
Ending Balance at Dec. 31, 2012	$ 233,815	$ 49,667	$ 181,151	$ 2,997
Ending Balance (in shares) at Dec. 31, 2012		7,622,750