Retirement Plans - Fair Value of Plan Assets by Investment Type (Details) - Pension plan - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	$ 8,920	$ 7,258	$ 7,819
Cash and Cash Equivalents | Level 1
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	48	95
Collective Funds | Level 2
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	$ 8,872	$ 7,163