Supplemental Compensation Plans (Details) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Salary Continuation Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Duration for benefit payment after retirement age	10 years
Retirement age	65 years
Reduced benefit age	55 years
Years of services for reduced benefit	10 years
Number of participants in SERP plan	3
Average years of salary used for benefit calculation	3 years
Average years of bonus used for benefit calculation	7 years
Target service years for executive	25 years
Target service years for CEO	20 years
Target benefit of average compensation (in hundredths)	50.00%
Reduction made for social security benefit (in hundredths)	50.00%
Expected age of social security benefit	65 years
Number of years average yields of treasury securities	3 years
Treasury securities duration	10 years
Period of monthly retirement benefit payment	120 months
Additional months for retirement payment for full year of service	6 years
Number of full service years used to calculate additional retirement payment	10 years
Maximum period for monthly retirement payment	180 months
Reduction in benefit for retirement prior to retirement age (in hundredths)	5.00%
Benefit reduction for retirement at age 55 (in hundredths)	50.00%
Early retirement age	55 years
Benefit payable for voluntary terminations prior to age 55 (in hundredths)	0.00%
Change in benefit obligation [Roll Forward]
Benefit obligation at beginning of year	$ 3,132	$ 2,723	$ 2,177
Service cost	146	132	111
Interest cost	124	138	122
Amendments	0	0	21
Plan loss (gain)	364	315	346
Benefits paid	(176)	(176)	(54)
Benefit obligation at end of year	3,590	3,132	2,723
Change in plan assets [Abstract]
Employer Contribution	176	176	54
Benefits paid	(176)	(176)	(54)
Fair value of plan assets at end of year	0	0	0
Reconciliation of funded status [Abstract]
Funded status	(3,590)	(3,132)	(2,723)
Unrecognized net plan loss	683	319	4
Unrecognized prior service cost	429	517	605
Net amount recognized	(2,478)	(2,296)	(2,114)
Amounts recognized in the consolidated balance sheet consist of [Abstract]
Accrued benefit liability	(3,590)	(3,132)	(2,723)
Accumulated other comprehensive income	1,112	836	609
Net amount recognized	(2,478)	(2,296)	(2,114)
Components of net periodic benefit cost [Abstract]
Service cost	146	132	111
Interest cost	124	138	122
Amortization of prior service cost	88	88	87
Net periodic benefit cost	358	358	320
Additional amounts recognized	0	0	(15)
Total benefit cost	358	358	305
Additional Information [Abstract]
Minimum benefit obligation at year end	3,590	3,132	2,723
(Decrease) increase in minimum liability included in other comprehensive loss	276	227	295
Assumptions used to determine benefit obligations [Abstract]
Discount rate used to determine net periodic benefit cost for years ended (in hundredths)	3.90%	5.00%	5.40%
Discount rate used to determine benefit obligations (in hundredths)	3.20%	3.90%	5.00%
Future salary increases (in hundredths)	4.00%	4.00%	4.00%
Expected future benefit payments [Abstract]
Benefit paid during fiscal year	176
2013	176
2014	188
2015	226
2016	281
2017	272
2018-2022	1,423
Directors' Retirement Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Duration for benefit payment after retirement age	10 years
Retirement age	65 years
Reduced benefit age	55 years
Years of services for reduced benefit	10 years
Change in benefit obligation [Roll Forward]
Benefit obligation at beginning of year	701	597	597
Service cost	24	23	35
Interest cost	27	30	33
Plan loss (gain)	(1)	66	(53)
Benefits paid	(8)	(15)	(15)
Benefit obligation at end of year	743	701	597
Change in plan assets [Abstract]
Employer Contribution	8	15	15
Benefits paid	(8)	(15)	(15)
Fair value of plan assets at end of year	0	0	0
Reconciliation of funded status [Abstract]
Funded status	(743)	(701)	(597)
Unrecognized net plan loss	(12)	(11)	(79)
Net amount recognized	(755)	(712)	(676)
Amounts recognized in the consolidated balance sheet consist of [Abstract]
Accrued benefit liability	(743)	(701)	(597)
Accumulated other comprehensive income	(12)	(11)	(79)
Net amount recognized	(755)	(712)	(676)
Components of net periodic benefit cost [Abstract]
Service cost	24	23	35
Interest cost	27	30	33
Recognized actuarial (gain)loss	0	(3)	0
Net periodic benefit cost	51	50	68
Additional amounts recognized	0	0	0
Total benefit cost	51	50	68
Additional Information [Abstract]
Minimum benefit obligation at year end	743	701	597
(Decrease) increase in minimum liability included in other comprehensive loss	(1)	68	(53)
Assumptions used to determine benefit obligations [Abstract]
Discount rate used to determine net periodic benefit cost for years ended (in hundredths)	3.80%	4.90%	5.30%
Discount rate used to determine benefit obligations (in hundredths)	3.20%	3.80%	4.90%
Expected future benefit payments [Abstract]
Benefit paid during fiscal year	8
2013	15
2014	15
2015	16
2016	30
2017	44
2018-2022	326
Directors' Retirement Plan [Member] | Minimum [Member]
Defined Benefit Plan Disclosure [Line Items]
Directors' retirement benefit per year of service	1
Directors' Retirement Plan [Member] | Maximum [Member]
Defined Benefit Plan Disclosure [Line Items]
Directors' retirement benefit per year of service	15
Executive Deferral Plan [Member]
Expected future benefit payments [Abstract]
Single-premium payment on insurance purchased	1,125
Cash surrender value of life insurance	2,164	2,097
Increase in accrued liabilities	45	56
Expenses	45	56	58
Director Deferral Plan [Member]
Expected future benefit payments [Abstract]
Cash surrender value of life insurance	116	112
Increase in accrued liabilities	1	1
Expenses	$ 1	$ 1	$ 1