Condensed Financial Statements of Parent Company, Condensed Statements of Income (Details) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Income
Interest on securities - taxable	$ 6,613	$ 6,745	$ 5,588
Interest on securities - nontaxable	6,463	6,532	6,504
Other income	472	449	354
Expenses
Income before income tax benefit and equity in undistributed net income of subsidiaries	22,992	22,885	19,792
Applicable income tax benefit	(5,245)	(5,247)	(4,223)
Net income	17,747	17,638	15,569
NBI [Member]
Income
Dividends from Subsidiaries	7,639	7,258	6,309
Interest on securities - taxable	5	17	23
Interest on securities - nontaxable	33	42	44
Other income	1,213	1,210	1,157
Total income	8,890	8,527	7,533
Expenses
Other expenses	1,791	1,794	1,756
Income before income tax benefit and equity in undistributed net income of subsidiaries	7,099	6,733	5,777
Applicable income tax benefit	136	148	152
Income before equity in undistributed net income of subsidiaries	7,235	6,881	5,929
Equity in undistributed net income of subsidiaries	10,512	10,757	9,640
Net income	$ 17,747	$ 17,638	$ 15,569