Employee Benefit Plans (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended
	Mar. 31, 2013	Mar. 31, 2012
Defined pension plan benefits [Member]
Components of net periodic benefit cost
Service cost – benefits earned during the year	$ 13	$ 12
Interest cost on projected benefit obligations	452	557
Expected return on plan assets	695	792
Amortization of prior service cost	0	0
Amortization of net loss	(215)	(522)
Net periodic benefit cost (income)	(15)	299
Other postretirement benefits [Member]
Components of net periodic benefit cost
Service cost – benefits earned during the year	42	39
Interest cost on projected benefit obligations	66	76
Expected return on plan assets	0	0
Amortization of prior service cost	40	40
Amortization of net loss	(3)	0
Net periodic benefit cost (income)	$ 151	$ 155