FAIR VALUE MEASUREMENTS - Available for Sale Securities and Gross Realized Gains and Losses (Details) - USD ($) $ in Thousands	3 Months Ended	9 Months Ended
Sep. 23, 2020	Sep. 25, 2019	Sep. 23, 2020	Sep. 25, 2019
Equity securities:
Gross proceeds from sales and redemptions	$ 0	$ 0	$ 20,000	$ 27,000
Cost basis of sales and redemptions	0	0	19,921	26,978
Gross realized gains included in net income (loss)	0	0	79	36
Gross realized losses included in net income (loss)	$ 0	$ 0	$ 0	$ (14)

Amount of cash inflow from sale of investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale).

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 320
-SubTopic 10
-Section 45
-Paragraph 11
-URI http://asc.fasb.org/extlink&oid=118954083&loc=d3e26853-111562

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 230
-SubTopic 10
-Section 45
-Paragraph 11
-URI http://asc.fasb.org/extlink&oid=118932676&loc=d3e3151-108585

Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 230
-SubTopic 10
-Section 45
-Paragraph 12
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=118932676&loc=d3e3179-108585

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Balance Type:	debit
Period Type:	duration