Pension Plans (Details) (USD $)	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Pension plans
Fair values of pension assets	$ 7,024,000	$ 6,347,000	$ 6,041,000
Liability for pension benefits	3,005,000	2,713,000
Increase in comprehensive earnings due to freeze of pension plans		589,000
Change in benefit obligation:
Benefit obligation at beginning of year	9,722,000	8,399,000
Service cost		153,000	296,000
Interest cost	454,000	491,000	454,000
Actuarial loss	735,000	1,399,000
Curtailment		(544,000)
Benefits paid	(188,000)	(176,000)
Other	13,000
Benefit obligation at end of year	10,736,000	9,722,000	8,399,000
Change in plan assets:
Fair value of plan assets at beginning of year	6,347,000	6,041,000
Actual gain (loss) on plan assets	714,000	(3,000)
Employer contribution	151,000	485,000
Benefits paid	(188,000)	(176,000)
Fair value of plan assets at end of year	7,024,000	6,347,000	6,041,000
Unfunded status	(3,712,000)	(3,375,000)
Amounts recognized in consolidated balance sheets
Accrued benefit cost	(707,000)	(662,000)
Liability for pension benefits	(3,005,000)	(2,713,000)
Total	(3,712,000)	(3,375,000)
Amounts recognized in accumulated other comprehensive loss that have not yet been recognized as components of net periodic benefit cost
Net actuarial loss	4,255,000	3,808,000
Total	4,255,000	3,808,000
Accumulated benefit obligation	10,736,000	9,722,000
Components of net periodic pension cost
Service cost		153,000	296,000
Interest cost	454,000	491,000	454,000
Expected return on plan assets	(508,000)	(526,000)	(463,000)
Curtailment loss		45,000
Recognized net actuarial loss	80,000	139,000	127,000
Net amortization		10,000	22,000
Net periodic pension cost	26,000	312,000	436,000
Amounts expected to recognized as components of net periodic benefit cost, which are included in accumulated other comprehensive loss
Actuarial loss	(94,000)
Net Periodic Pension Cost
Weighted-average discount rate (as a percent)	5.00%	6.10%	6.40%
Weighted-average rate of compensation increase (as a percent)		4.00%	4.00%
Expected long-term rate of return on plan assets (as a percent)	8.00%	8.50%	8.50%
Benefit Obligation
Weighted-average discount rate (as a percent)	4.40%	5.00%
Excess plan
Pension plans
Fair values of pension assets	680,000	525,000
Change in plan assets:
Fair value of plan assets at end of year	680,000	525,000
SERP
Pension plans
Liability for pension benefits	60,000
Amounts recognized in consolidated balance sheets
Liability for pension benefits	$ (60,000)