Retirement Plans (Details) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Assumptions (end of period):
Discount rate used in determining benefit obligation	3.89%	4.50%	5.25%
Rate of compensation increase	0.00%	0.00%	0.00%
Reconciliation of funded status (end of period):
Accumulated benefit obligation	$ (13,439)	$ (12,990)	$ (12,050)
Projected benefit obligation	(13,439)	(12,990)	(12,050)
Fair value of plan assets	9,754	9,019	9,217
Funded status	(3,685)	(3,971)	(2,833)
Net actuarial loss	(4,545)	(4,582)	(3,114)
Accumulated other comprehensive loss	(4,545)	(4,582)	(3,114)
Prepaid pension cost	860	611	281
Net amount recognized as of December 31	(3,685)	(3,971)	(2,833)
Changes in projected benefit obligation:
Benefit obligation as of beginning of period	12,990	12,050	11,301
Interest cost	564	609	651
Actuarial liability loss	700	1,160	925
Benefits paid	(815)	(829)	(827)
Benefit obligation as of end of period	13,439	12,990	12,050
Change in plan assets:
Fair value of plan assets as of beginning of period	9,019	9,217	8,673
Actual return on plan assets (net of expenses)	839	(4)	937
Employer contributions	711	635	434
Benefits paid	(815)	(829)	(827)
Fair value of plan assets as of end of period	9,754	9,019	9,217
Net periodic pension cost:
Service cost - benefits earned during the period	0	0	0
Interest cost on projected benefit obligation	564	609	651
Expected return on plan assets	(584)	(590)	(546)
Recognized actuarial loss	482	287	224
Net periodic pension cost	$ 462	$ 306	$ 329
Discount rate	4.50%	5.25%	6.00%
Expected return on plan assets	6.50%	6.50%	6.50%
Rate of compensation increase	0.00%	0.00%	0.00%