Employee Benefit Plans - Net Periodic Pension and Postretirement Benefit Costs (Details) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Pension Plans, Defined Benefit [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Service costs	$ 680	$ 600	$ 640
Interest costs	1,610	1,620	1,590
Expected return on plan assets	(1,810)	(1,720)	(1,600)
Amortization of prior service cost	0	0	0
Settlements and curtailments gain	0	190	0
Amortization of net (gain)/loss	1,280	1,070	720
Net periodic benefit cost (income)	1,760	1,760	1,350
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	40	50	50
Expected return on plan assets	0	0	0
Amortization of prior service cost	0	(200)	(270)
Settlements and curtailments gain	0	(1,490)	0
Amortization of net (gain)/loss	(80)	(80)	(90)
Net periodic benefit cost (income)	$ (40)	$ (1,720)	$ (310)