Non-pension Post-retirement Benefits (Amounts Recognized in Balance Sheet) (Details) - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017
Defined Benefit Plan Disclosure [Line Items]
Non-pension post-retirement benefits (current portion)	$ 3,951	$ 4,185
Non-pension post-retirement benefits	43,015	49,758
Non-pension Post-retirement Benefit Plans
Defined Benefit Plan Disclosure [Line Items]
Non-pension post-retirement benefits (current portion)	3,951	4,185
Non-pension post-retirement benefits	43,015	49,758
Total non-pension post-retirement benefits liability	$ 46,966	$ 53,943