Employee Benefit Plans - Net Periodic Pension and Postretirement Benefit Costs (Details) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Pension Plans, Defined Benefit [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Service costs	$ 600	$ 640	$ 600
Interest costs	1,620	1,590	1,570
Expected return on plan assets	(1,720)	(1,600)	(1,570)
Amortization of prior service cost	0	0	0
Settlements and curtailments gain	190	0	0
Amortization of net (gain)/loss	1,070	720	440
Net periodic benefit cost (income)	1,760	1,350	1,040
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
Interest costs	50	50	70
Expected return on plan assets	0	0	0
Amortization of prior service cost	(200)	(270)	(270)
Settlements and curtailments gain	(1,490)	0	0
Amortization of net (gain)/loss	(80)	(90)	(50)
Net periodic benefit cost (income)	$ (1,720)	$ (310)	$ (250)