Postretirement Benefit Plans (Amounts recognized in balance sheet) (Details) - Korea Defined Benefit Plan - USD ($) $ in Thousands	8 Months Ended			12 Months Ended
	Dec. 31, 2017	Dec. 31, 2017	Dec. 31, 2017	Dec. 31, 2018
Defined Benefit Plan Disclosure [Line Items]
Net defined benefit plan liability	$ 3,942	$ 3,942	$ 3,942	$ 4,489
Accumulated other comprehensive loss consists of the following:
Actuarial loss before taxes	$ (174)	$ 174	$ (518)	$ 692