Pension and Postretirement Benefits (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended
	Mar. 31, 2013	Mar. 31, 2012
Defined Benefit Plan Disclosure [Line Items]
Minimum years of service to participate in the health and life insurance benefits as of January 1, 1995	14 years
Contribution to defined benefit pension plan	$ 0	$ 2,600
Pension Benefit [Member]
Defined Benefit Plan Disclosure [Line Items]
Service cost	0	111
Interest cost	95	111
Expected return on plan assets	(214)	(198)
Amortization of transition obligation	0	0
Amortization of net losses	90	130
Net periodic plan cost	(29)	154
Postretirement Benefits [Member]
Defined Benefit Plan Disclosure [Line Items]
Service cost	0	0
Interest cost	4	4
Expected return on plan assets	0	0
Amortization of transition obligation	0	4
Amortization of net losses	5	0
Net periodic plan cost	$ 9	$ 8