Defined Benefit Plans - Net Periodic Pension and Postretirement Benefit Costs (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended
	Mar. 31, 2013	Mar. 31, 2012
Pension Plans, Defined Benefit [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Service costs	$ 180	$ 150
Interest costs	410	400
Expected return on plan assets	(460)	(430)
Amortization of prior service cost	0	0
Amortization of net (gain)/loss	320	270
Net periodic benefit cost	450	390
Other Postretirement Benefit Plans, Defined Benefit [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Service costs	0	0
Interest costs	10	10
Expected return on plan assets	0	0
Amortization of prior service cost	0	(70)
Amortization of net (gain)/loss	(20)	(20)
Net periodic benefit cost	$ (10)	$ (80)