Consolidated Statements Of Changes In Shareholders' Equity - USD ($)	Total	Common Stock	Retained Earnings	Accumulated Other Comprehensive Income (Loss)
Beginning Balance (in shares) at Dec. 31, 2012		7,622,750
Beginning Balance at Dec. 31, 2012	$ 233,815,000	$ 49,667,000	$ 181,151,000	$ 2,997,000
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	22,783,000		22,783,000
Other comprehensive loss, net of tax	(15,344,000)			(15,344,000)
Stock-based compensation expense	596,000	$ 596,000
Exercise of stock options and issuance of restricted stock, net of repurchase for tax withholdings and tax benefit (in shares)		25,308
Exercise of stock options and issuance of restricted stock, net of repurchase for tax withholdings and tax benefit	300,000	$ 300,000
Common stock repurchased (in shares)		(68,145)
Common stock repurchased	(2,780,000)	$ (2,780,000)
Cash dividends declared ( $1.08, $1.11 and $1.20 per share in 2013, 2014, and 2015, respectively)	(8,274,000)		(8,274,000)
Equity issuance costs	0
Ending Balance (in shares) at Dec. 31, 2013		7,579,913
Ending Balance at Dec. 31, 2013	231,096,000	$ 47,783,000	195,660,000	(12,347,000)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	24,570,000		24,570,000
Other comprehensive loss, net of tax	3,922,000			3,922,000
Stock-based compensation expense	599,000	$ 599,000
Exercise of stock options and issuance of restricted stock, net of repurchase for tax withholdings and tax benefit (in shares)		27,664
Exercise of stock options and issuance of restricted stock, net of repurchase for tax withholdings and tax benefit	328,000	$ 328,000
Common stock repurchased (in shares)		(181,355)
Common stock repurchased	(7,155,000)	$ (7,155,000)
Cash dividends declared ( $1.08, $1.11 and $1.20 per share in 2013, 2014, and 2015, respectively)	(8,251,000)		(8,251,000)
Equity issuance costs	0
Ending Balance (in shares) at Dec. 31, 2014		7,426,222
Ending Balance at Dec. 31, 2014	245,109,000	$ 41,555,000	211,979,000	(8,425,000)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	20,952,000		20,952,000
Other comprehensive loss, net of tax	(3,797,000)			(3,797,000)
Stock-based compensation expense	836,000	$ 836,000
Exercise of stock options and issuance of restricted stock, net of repurchase for tax withholdings and tax benefit (in shares)		44,494
Exercise of stock options and issuance of restricted stock, net of repurchase for tax withholdings and tax benefit	753,000	$ 753,000
Cash dividends declared ( $1.08, $1.11 and $1.20 per share in 2013, 2014, and 2015, respectively)	(10,602,000)		(10,602,000)
Equity issuance costs	(612,000)	$ (612,000)
SBM acquisition common stock issuance (in shares)		2,749,762
SBM acquisition common stock issuance	108,561,000	$ 108,561,000
SBM acquisition non-qualified stock option awards	1,990,000	$ 1,990,000
Ending Balance (in shares) at Dec. 31, 2015		10,220,478.000
Ending Balance at Dec. 31, 2015	$ 363,190,000	$ 153,083,000	$ 222,329,000	$ (12,222,000)