Retirement Plans - Net Periodic Pension Cost (Details) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Pension plan
Cost components:
Service cost	$ (359)	$ (284)	$ (251)
Interest cost	(402)	(375)	(384)
Expected return on plan assets	542	454	446
Net amortization and deferral	253	190	220
Total net periodic pension cost	472	395	409
SERP
Cost components:
Service cost	(318)	(525)	172
Interest cost	(219)	(208)	215
Net amortization and deferral	229	287	(66)
Total net periodic pension cost	$ 766	$ 1,020	$ (453)