Consolidated Statements of Changes in Stockholders' Equity (USD $) In Thousands, unless otherwise specified	Total	Common stock	Additional paid-in capital	Retained earnings	Accumulated other comprehensive income (loss)
Balance at Dec. 31, 2010	$ 169,861	$ 6,679	$ 12,206	$ 147,837	$ 3,139
Balance (in shares) at Dec. 31, 2010		13,737
Increase (Decrease) in Stockholders' Equity
Net income	23,604			23,604
Other comprehensive income (loss), net of tax	2,323				2,323
Stock compensation expense	1,165		1,165
Stock issued for exercise of stock options and dividend reinvestment plan, net of withholdings to satisfy employee tax obligations upon vesting of stock awards	663	159	504
Stock issued for exercise of stock options and dividend reinvestment plan, net of withholdings to satisfy employee tax obligations upon vesting of stock awards (in shares)		48
Shares issued for non-vested restricted stock		140	866	(1,006)
Shares issued for non-vested restricted stock (in shares)		42
Cash dividends, $0.81, $0.77 and $0.72 per share for the year ended December 31, 2013, 2012 and 2011, respectively	(9,930)			(9,930)
Shares repurchased and cancelled		(25)	(142)	167
Shares repurchased and cancelled (in shares)		(8)
Balance at Dec. 31, 2011	187,686	6,953	14,599	160,672	5,462
Balance (in shares) at Dec. 31, 2011		13,819
Increase (Decrease) in Stockholders' Equity
Net income	25,801			25,801
Other comprehensive income (loss), net of tax	(41)				(41)
Stock compensation expense	1,481		1,481
Stock issued for exercise of stock options and dividend reinvestment plan, net of withholdings to satisfy employee tax obligations upon vesting of stock awards	1,397	233	1,166	(2)
Stock issued for exercise of stock options and dividend reinvestment plan, net of withholdings to satisfy employee tax obligations upon vesting of stock awards (in shares)		70
Shares issued for non-vested restricted stock		190	1,108	(1,298)
Shares issued for non-vested restricted stock (in shares)		57
Cash dividends, $0.81, $0.77 and $0.72 per share for the year ended December 31, 2013, 2012 and 2011, respectively	(10,691)			(10,691)
Shares repurchased and cancelled	(558)	(103)	(623)	168
Shares repurchased and cancelled (in shares)		(31)
Balance at Dec. 31, 2012	205,075	7,273	17,731	174,650	5,421
Balance (in shares) at Dec. 31, 2012		13,915
Increase (Decrease) in Stockholders' Equity
Net income	27,170			27,170
Other comprehensive income (loss), net of tax	(7,638)				(7,638)
Stock compensation expense	1,940		1,940
Stock issued for exercise of stock options and dividend reinvestment plan, net of withholdings to satisfy employee tax obligations upon vesting of stock awards	3,375	503	3,041	(169)
Stock issued for exercise of stock options and dividend reinvestment plan, net of withholdings to satisfy employee tax obligations upon vesting of stock awards (in shares)		151
Shares issued for non-vested restricted stock		184	1,083	(1,267)
Shares issued for non-vested restricted stock (in shares)		55
Stock issued for acquisition	12,198	1,769	10,429
Stock issued for acquisition (in shares)		531
Cash dividends, $0.81, $0.77 and $0.72 per share for the year ended December 31, 2013, 2012 and 2011, respectively	(11,670)			(11,670)
Shares repurchased and cancelled	(1,006)	(148)	(969)	111
Shares repurchased and cancelled (in shares)		(43)
Balance at Dec. 31, 2013	$ 229,444	$ 9,581	$ 33,255	$ 188,825	$ (2,217)
Balance (in shares) at Dec. 31, 2013		14,609