Retirement Plans - Fair Value of Plan Assets by Investment Type (Details) - Pension plan - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	$ 7,258	$ 7,819	$ 6,974
Cash and Cash Equivalents | Level 1
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	95	455
Collective Funds | Level 2
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	7,163	3,942
Treasury/Corporate Notes | Level 2
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0	1,583
Corporate Equities | Level 1
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	$ 0	$ 1,839