Retirement Plans (Details) (USD $)	3 Months Ended		9 Months Ended
	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013	Sep. 30, 2012
Components of net periodic pension expense
Interest cost	$ (250,000)	$ (258,000)	$ (750,000)	$ (774,000)
Expected return on plan assets	430,000	407,000	1,291,000	1,222,000
Recognized net actuarial loss	(301,000)	(267,000)	(903,000)	(801,000)
Net periodic pension expense (benefit)	(121,000)	(118,000)	(362,000)	(353,000)
Contributions to the pension plan	$ 300,000		$ 900,000
Employee hired on or after January 1, 2006 | Maximum
Retirement Plans
Requisite age of employees for receiving retirement benefits under the new benefit formula			45 years
Requisite service period for receiving retirement benefits under the new benefit formula			5 years
Non-contributory defined benefit pension plan | Employees hired on or before December 31, 2005 | Minimum
Retirement Plans
Requisite age of employees for receiving retirement benefits under the plan			21 years