Postretirement Benefit Plans (Textual) (Details) - USD ($) $ in Thousands	8 Months Ended	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2018	Dec. 31, 2017
Defined Benefit Plan Disclosure [Line Items]
Employer contributions	$ 6	$ 7
Estimated future employer contributions in 2019		7
Domestic Plan
Defined Benefit Plan Disclosure [Line Items]
Matching contribution, contributory employee savings plan, amount		$ 400	$ 500
Korea Defined Benefit Plan
Defined Benefit Plan Disclosure [Line Items]
Service period (in years)		1 year
Postemployment Retirement Benefits | Domestic Plan
Defined Benefit Plan Disclosure [Line Items]
Company matching contribution percentage		50.00%