FAIR VALUE MEASUREMENTS - Cash, Cash Equivalents and Marketable Securities (Details) - USD ($) $ in Thousands	Jun. 24, 2020	Dec. 25, 2019
Debt Securities, Available-for-sale [Line Items]
Cost Basis	$ 173,984	$ 37,099
Total cost basis including Mutual Funds	190,767	73,535
Gross Unrealized Gains	50	72
Gross Unrealized Losses	0	0
Cash and cash equivalents fair value	173,984	37,099
Fair value of marketable securities	16,833	36,508
Fair Value	190,817	73,607
Level 1 | Mutual funds
Debt Securities, Available-for-sale [Line Items]
Mutual funds	16,783	36,436
Gross Unrealized Gains	50	72
Gross Unrealized Losses	0	0
Fair value of marketable securities	16,833	36,508
Cash
Debt Securities, Available-for-sale [Line Items]
Cost Basis	173,984	32,094
Cash and cash equivalents fair value	173,984	32,094
Money market funds | Level 1
Debt Securities, Available-for-sale [Line Items]
Cost Basis	0	5,005
Cash and cash equivalents fair value	$ 0	$ 5,005