RESTRICTED CASH AND INVESTMENTS (Details) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2019 USD ($) security	Jul. 01, 2018 USD ($)	Jun. 30, 2019 USD ($) security	Jul. 01, 2018 USD ($)	Dec. 30, 2018 USD ($) security
Restricted Cash and Investments [Line Items]
Cash collateral held by insurance carriers	$ 23,877		$ 23,877		$ 24,182
Cash and cash equivalents held in Trust	24,721		24,721		28,021
Investments held in Trust	145,396		145,396		156,618
Deferred compensation mutual funds	28,416		28,416		23,363
Other restricted cash and cash equivalents	146		146		3,259
Restricted cash and investments	222,556		222,556		235,443
Held-to-maturity Securities, Reconciliation to Fair Value [Abstract]
Gross Unrealized Gain	2,833		2,833		491
Gross Unrealized Loss	(75)		(75)		(1,468)
Fair Value	148,154		148,154		155,641
Estimated fair value
Less than 12 months	0		0		36,743
12 months or more	30,046		30,046		68,476
Total	30,046		30,046		105,219
Unrealized losses
Less than 12 months	0		0		(362)
12 months or more	(75)		(75)		(1,106)
Total	$ (75)		$ (75)		$ (1,468)
Securities in unrealized loss positions, number of positions | security	28		28		93
Held-to-maturity Securities, Investment Maturities, Fair Value [Abstract]
Fair Value	$ 148,154		$ 148,154		$ 155,641
Unrealized gain	800		3,200
Unrealized loss		$ 100		$ (100)
Municipal debt securities
Restricted Cash and Investments [Line Items]
Investments held in Trust	74,206		74,206		76,750
Held-to-maturity Securities, Reconciliation to Fair Value [Abstract]
Gross Unrealized Gain	1,883		1,883		456
Gross Unrealized Loss	(5)		(5)		(516)
Fair Value	76,084		76,084		76,690
Estimated fair value
Less than 12 months	0		0		12,803
12 months or more	5,992		5,992		22,638
Total	5,992		5,992		35,441
Unrealized losses
Less than 12 months	0		0		(74)
12 months or more	(5)		(5)		(442)
Total	(5)		(5)		(516)
Held-to-maturity Securities, Investment Maturities, Fair Value [Abstract]
Fair Value	76,084		76,084		76,690
Corporate debt securities
Restricted Cash and Investments [Line Items]
Investments held in Trust	68,262		68,262		76,310
Held-to-maturity Securities, Reconciliation to Fair Value [Abstract]
Gross Unrealized Gain	883		883		30
Gross Unrealized Loss	(64)		(64)		(908)
Fair Value	69,081		69,081		75,432
Estimated fair value
Less than 12 months	0		0		22,567
12 months or more	23,378		23,378		44,463
Total	23,378		23,378		67,030
Unrealized losses
Less than 12 months	0		0		(277)
12 months or more	(64)		(64)		(631)
Total	(64)		(64)		(908)
Held-to-maturity Securities, Investment Maturities, Fair Value [Abstract]
Fair Value	69,081		69,081		75,432
Agency mortgage-backed securities
Restricted Cash and Investments [Line Items]
Investments held in Trust	1,929		1,929		2,559
Held-to-maturity Securities, Reconciliation to Fair Value [Abstract]
Gross Unrealized Gain	21		21		5
Gross Unrealized Loss	(6)		(6)		(33)
Fair Value	1,944		1,944		2,531
Estimated fair value
Less than 12 months	0		0		385
12 months or more	676		676		1,375
Total	676		676		1,760
Unrealized losses
Less than 12 months	0		0		0
12 months or more	(6)		(6)		(33)
Total	(6)		(6)		(33)
Held-to-maturity Securities, Investment Maturities, Fair Value [Abstract]
Fair Value	1,944		1,944		2,531
U.S. government and agency securities
Restricted Cash and Investments [Line Items]
Investments held in Trust	999		999		999
Held-to-maturity Securities, Reconciliation to Fair Value [Abstract]
Gross Unrealized Gain	46		46		0
Gross Unrealized Loss	0		0		(11)
Fair Value	1,045		1,045		988
Estimated fair value
Less than 12 months					988
12 months or more					0
Total					988
Unrealized losses
Less than 12 months					(11)
12 months or more					0
Total					(11)
Held-to-maturity Securities, Investment Maturities, Fair Value [Abstract]
Fair Value	1,045		1,045		$ 988
Restricted Cash and Investments
Restricted Cash and Investments [Line Items]
Investments held in Trust	145,396		145,396
Held-to-maturity Securities, Reconciliation to Fair Value [Abstract]
Fair Value	148,154		148,154
Held-to-maturity Securities, Investment Maturities, Amortized Cost [Abstract]
Due in one year or less	10,453		10,453
Due after one year through five years	88,986		88,986
Due after five years through ten years	45,957		45,957
Held-to-maturity Securities, Investment Maturities, Fair Value [Abstract]
Due in one year or less	10,442		10,442
Due after one year through five years	90,201		90,201
Due after five years through ten years	47,511		47,511
Fair Value	$ 148,154		$ 148,154