Allowance for Credit Losses - Changes in Allowance for Credit Losses (Details) (USD $)	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Financing Receivable, Allowance for Credit Losses [Roll Forward]
Allowance for credit losses, beginning balance	$ 11,396,000	$ 11,014,000	$ 10,200,000
Provision charged to operations	700,000	1,050,000	3,800,000
Losses charged to allowance	(2,850,000)	(1,532,000)	(4,122,000)
Recoveries	887,000	864,000	1,136,000
Allowance for credit losses, ending balance	10,133,000	11,396,000	11,014,000
Ending balance: individually evaluated for impairment	510,000	4,368,000
Ending balance: collectively evaluated for impairment	9,623,000	7,028,000
Commercial
Financing Receivable, Allowance for Credit Losses [Roll Forward]
Allowance for credit losses, beginning balance	2,266,000	2,437,000
Provision charged to operations	18,000	(177,000)
Losses charged to allowance	(123,000)	(280,000)
Recoveries	515,000	286,000
Allowance for credit losses, ending balance	2,676,000	2,266,000
Ending balance: individually evaluated for impairment	40,000	231,000
Ending balance: collectively evaluated for impairment	2,636,000	2,035,000
Real Estate Portfolio Segment
Financing Receivable, Allowance for Credit Losses [Roll Forward]
Allowance for credit losses, beginning balance	7,155,000	5,836,000
Provision charged to operations	643,000	1,403,000
Losses charged to allowance	(1,966,000)	(312,000)
Recoveries	45,000	228,000
Allowance for credit losses, ending balance	5,877,000	7,155,000
Ending balance: individually evaluated for impairment	465,000	3,764,000
Ending balance: collectively evaluated for impairment	5,412,000	3,391,000
Consumer
Financing Receivable, Allowance for Credit Losses [Roll Forward]
Allowance for credit losses, beginning balance	1,836,000	2,503,000
Provision charged to operations	139,000	(77,000)
Losses charged to allowance	(761,000)	(940,000)
Recoveries	327,000	350,000
Allowance for credit losses, ending balance	1,541,000	1,836,000
Ending balance: individually evaluated for impairment	5,000	373,000
Ending balance: collectively evaluated for impairment	1,536,000	1,463,000
Unallocated
Financing Receivable, Allowance for Credit Losses [Roll Forward]
Allowance for credit losses, beginning balance	139,000	238,000
Provision charged to operations	(100,000)	(99,000)
Losses charged to allowance	0	0
Recoveries	0	0
Allowance for credit losses, ending balance	39,000	139,000
Ending balance: individually evaluated for impairment	0	0
Ending balance: collectively evaluated for impairment	$ 39,000	$ 139,000