SIGNIFICANT ACCOUNTING POLICIES - Cash, Cash Equivalents, and Restricted Cash (Details) - USD ($) $ in Thousands	Apr. 01, 2018	Dec. 31, 2017	Mar. 26, 2017	Dec. 25, 2016
Reconciliation of cash, cash equivalents and restricted cash as reported in the condensed consolidated balance sheets to the total of the same such amounts shown above:
Cash equivalents	$ 19,976	$ 99,387
Restricted cash included in other assets	31,967	31,967
Cash, cash equivalents and restricted cash	$ 51,943	$ 131,354	$ 53,737	$ 36,248