Retirement Plans - Fair Value of Plan Assets by Investment Type (Details) (Pension plan, USD $) In Thousands, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2011
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	$ 7,972	$ 8,633	$ 6,799
Cash and Cash Equivalents | Level 1
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	858	1,336
Collective Funds | Level 2
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	3,575	3,851
Treasury/Corporate Notes | Level 2
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	1,372	1,357
Corporate Equities | Level 1
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	$ 2,167	$ 2,089