Retirement Plans (Information About Plan Assets) (Details) - Pension Plan - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
United States
Defined Benefit Plan Disclosure
Fair value of plan asset	$ 12,468	$ 14,892	$ 14,180
United States | Cash and cash equivalents
Defined Benefit Plan Disclosure
Fair value of plan asset	355	284
United States | Total fixed income
Defined Benefit Plan Disclosure
Fair value of plan asset	3,521	4,755
United States | Corporate bonds
Defined Benefit Plan Disclosure
Fair value of plan asset	3,521	4,755
United States | Total mutual funds and equities
Defined Benefit Plan Disclosure
Fair value of plan asset	8,592	9,853
United States | Mutual funds
Defined Benefit Plan Disclosure
Fair value of plan asset	1,881	712
United States | Equity securities
Defined Benefit Plan Disclosure
Fair value of plan asset	6,711	9,141
United Kingdom
Defined Benefit Plan Disclosure
Fair value of plan asset	6,347	6,904	$ 5,826
United Kingdom | Cash and cash equivalents
Defined Benefit Plan Disclosure
Fair value of plan asset	685	695
United Kingdom | Bonds
Defined Benefit Plan Disclosure
Fair value of plan asset	2,866	2,276
United Kingdom | Other
Defined Benefit Plan Disclosure
Fair value of plan asset	795	1,226
United Kingdom | Equity securities
Defined Benefit Plan Disclosure
Fair value of plan asset	$ 2,001	$ 2,707