Retirement Plans - Net Periodic Pension Cost (Details) (USD $) In Thousands, unless otherwise specified	6 Months Ended
	Jun. 30, 2014	Jun. 30, 2013
Pension plan
Cost components:
Service cost-benefits earned during the period	$ (180)	$ (142)
Interest cost on projected benefit obligation	(202)	(188)
Expected return on plan assets	272	228
Net amortization and deferral	(533)	(96)
Total net periodic pension cost	(643)	(198)
SERP
Cost components:
Service cost-benefits earned during the period	(160)	(86)
Interest cost on projected benefit obligation	(110)	(108)
Net amortization and deferral	(114)	(144)
Total net periodic pension cost	$ (384)	$ (338)