Retirement Plans (Information About Plan Assets) (Details) - Pension Plan - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
UNITED STATES
Asset Category
Fair value of plan assets	$ 14,892	$ 14,180	$ 14,235
UNITED STATES | Cash and cash equivalents
Asset Category
Fair value of plan assets	284	660
UNITED STATES | Total fixed income funds
Asset Category
Fair value of plan assets	4,755	4,767
UNITED STATES | Corporate bonds
Asset Category
Fair value of plan assets	4,755	4,767
UNITED STATES | Total mutual funds and equities
Asset Category
Fair value of plan assets	9,853	8,753
UNITED STATES | Mutual funds
Asset Category
Fair value of plan assets	712	8,753
UNITED STATES | Exchange-Traded Funds (“ETF”)
Asset Category
Fair value of plan assets	9,141	0
Foreign Plan
Asset Category
Fair value of plan assets	6,904	5,826	$ 6,661
Foreign Plan | Cash and cash equivalents
Asset Category
Fair value of plan assets	695	707
Foreign Plan | Bonds
Asset Category
Fair value of plan assets	2,276	1,347
Foreign Plan | Other
Asset Category
Fair value of plan assets	1,226	1,155
Foreign Plan | Exchange-Traded Funds (“ETF”)
Asset Category
Fair value of plan assets	$ 2,707	$ 2,617