Basis of Presentation and General Information (Carrying Amounts of Major Classes of Assets and Liabilities Presented in Discontinued Operations) (Parenthetical) (Details) - USD ($) $ in Thousands	Jun. 28, 2019	Dec. 28, 2018
European REL Working Capital group [Member]
Income Statement Balance Sheet And Additional Disclosures By Disposal Groups Including Discontinued Operations [Line Items]
Accounts receivable and unbilled revenue, allowance	$ 0	$ 0