Retirement Plans - Information About Plan Assets (Details) - Pension Plan - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
United States
Defined Benefit Plan Disclosure
Fair value of plan asset	$ 4,360	$ 12,468	$ 14,892
United States | Cash and cash equivalents
Defined Benefit Plan Disclosure
Fair value of plan asset	817	355
United States | Total fixed income
Defined Benefit Plan Disclosure
Fair value of plan asset	1,336	3,521
United States | Corporate bonds
Defined Benefit Plan Disclosure
Fair value of plan asset	1,336	3,521
United States | Total mutual funds and equities
Defined Benefit Plan Disclosure
Fair value of plan asset	2,207	8,592
United States | Mutual funds
Defined Benefit Plan Disclosure
Fair value of plan asset	694	1,881
United States | Equity securities
Defined Benefit Plan Disclosure
Fair value of plan asset	1,513	6,711
United Kingdom
Defined Benefit Plan Disclosure
Fair value of plan asset	7,290	6,347	$ 6,904
United Kingdom | Cash and cash equivalents
Defined Benefit Plan Disclosure
Fair value of plan asset	516	685
United Kingdom | Bonds
Defined Benefit Plan Disclosure
Fair value of plan asset	3,735	2,866
United Kingdom | Other
Defined Benefit Plan Disclosure
Fair value of plan asset	949	795
United Kingdom | Equity securities
Defined Benefit Plan Disclosure
Fair value of plan asset	$ 2,090	$ 2,001