Defined Benefit Plans - Net Periodic Pension and Postretirement Benefit Costs (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended
	Mar. 31, 2014	Mar. 31, 2013
Pension Plans, Defined Benefit [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Service costs	$ 190	$ 180
Interest costs	440	410
Expected return on plan assets	(520)	(460)
Amortization of net (gain)/loss	280	320
Net periodic benefit cost	390	450
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 net (gain)/loss	(20)	(20)
Net periodic benefit cost	$ (10)	$ (10)