Defined Benefit Plans - Net Periodic Pension and Postretirement Benefit Costs (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2013	Jun. 30, 2012	Jun. 30, 2013	Jun. 30, 2012
Pension Plans, Defined Benefit [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Service costs	$ 170	$ 150	$ 350	$ 300
Interest costs	410	400	820	800
Expected return on plan assets	(460)	(420)	(920)	(850)
Amortization of prior service cost	10	10	10	10
Amortization of net (gain)/loss	320	260	640	530
Net periodic benefit cost	450	400	900	790
Other Postretirement Benefit Plans, Defined Benefit [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Service costs	0	0	0	0
Interest costs	10	10	20	20
Expected return on plan assets	0	0	0	0
Amortization of prior service cost	0	(60)	0	(130)
Amortization of net (gain)/loss	(20)	(20)	(40)	(40)
Net periodic benefit cost	$ (10)	$ (70)	$ (20)	$ (150)