Defined Benefit Pension Plans Schedule of Amounts Recognized in the Consolidated Balance Sheets (Details) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Defined Benefit Plan, Amounts for Asset (Liability) Recognized in Statement of Financial Position [Abstract]
Plan Assets in Other Long Term Assets	$ 991	$ 654
Current Portion of Pension Plan Liability in Wages and Benefits Payable	3,260	3,202
Long-term portion of pension plan liability	95,717	84,498
Net Pension Plan Benefit Liability	$ 97,986	$ 87,046