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
Beginning Balance at Dec. 31, 2010	$ 205,995	$ 50,936	$ 150,730	$ 4,329
Beginning Balance (in shares) at Dec. 31, 2010		7,658,496
Net income	20,338		20,338
Other comprehensive income, net of tax:
Change in fair value of securities available for sale	7,256			7,256
Change in fair value of cash flow hedges	(6,363)			(6,363)
Change in net unrecognized losses on postretirement plans	42			42
Comprehensive income	21,273		20,338	935
Stock-based compensation expense	593	593
Exercise of stock options and issuance of restricted stock, net of repurchase for tax withholdings and tax benefit (in shares)		27,782
Exercise of stock options and issuance of restricted stock, net of repurchase for tax withholdings and tax benefit	118	118
Common stock repurchased (in shares)		(8,135)
Common stock repurchased	(272)	(272)
Cash dividends declared ($0.75 per share)	(5,768)		(5,768)
Ending Balance at Sep. 30, 2011	221,939	51,375	165,300	5,264
Ending Balance (in shares) at Sep. 30, 2011		7,678,143
Beginning Balance at Dec. 31, 2011	218,876	51,438	165,377	2,061
Beginning Balance (in shares) at Dec. 31, 2011		7,664,975
Net income	19,250		19,250
Other comprehensive income, net of tax:
Change in fair value of securities available for sale	5,183			5,183
Change in fair value of cash flow hedges	(645)			(645)
Change in net unrecognized losses on postretirement plans	80			80
Comprehensive income	23,868		19,250	4,618
Stock-based compensation expense	355	355
Exercise of stock options and issuance of restricted stock, net of repurchase for tax withholdings and tax benefit (in shares)		20,677
Exercise of stock options and issuance of restricted stock, net of repurchase for tax withholdings and tax benefit	(241)	(241)
Common stock repurchased (in shares)		(65,580)
Common stock repurchased	(2,097)	(2,097)
Cash dividends declared ($0.75 per share)	(5,783)		(5,783)
Ending Balance at Sep. 30, 2012	$ 234,978	$ 49,455	$ 178,844	$ 6,679
Ending Balance (in shares) at Sep. 30, 2012		7,620,072