Retirement Plans - Net periodic pension cost (Details) (Pension Plans [Member], USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Pension Plans [Member]
Defined Benefit Plan Disclosure [Line Items]
Interest cost	$ 259	$ 287	$ 303
Expected return on assets	(333)	(236)	(235)
Amortization of net loss	111	101	64
Net periodic pension cost	$ 37	$ 152	$ 132