RESTRICTED CASH AND INVESTMENTS (Details) $ in Thousands	3 Months Ended	12 Months Ended
Apr. 01, 2018 USD ($) security	Dec. 31, 2017 USD ($) security
Restricted Cash and Investments [Line Items]
Cash collateral held by insurance carriers	$ 23,035	$ 22,926
Cash and cash equivalents held in Trust	28,981	16,113
Investments held in Trust	166,255	171,752
Deferred compensation mutual funds	24,093	22,428
Other restricted cash and cash equivalents	402	6,012
Restricted cash and investments	242,766	239,231
Held-to-maturity Securities, Reconciliation to Fair Value [Abstract]
Gross Unrealized Gain	294	1,324
Gross Unrealized Loss	(2,103)	(838)
Fair Value	164,446	172,238
Estimated fair value
Less than 12 months	111,332	73,392
12 months or more	20,153	20,600
Total	131,485	93,992
Unrealized losses
Less than 12 months	(1,409)	(445)
12 months or more	(694)	(393)
Total	$ (2,103)	$ (838)
Securities in unrealized loss positions, number of positions \| security	112	83
Held-to-maturity Securities, Investment Maturities, Fair Value [Abstract]
Fair Value	$ 164,446	$ 172,238
Municipal debt securities
Restricted Cash and Investments [Line Items]
Investments held in Trust	79,291	82,770
Held-to-maturity Securities, Reconciliation to Fair Value [Abstract]
Gross Unrealized Gain	262	974
Gross Unrealized Loss	(910)	(378)
Fair Value	78,643	83,366
Estimated fair value
Less than 12 months	42,461	23,078
12 months or more	9,369	9,631
Total	51,830	32,709
Unrealized losses
Less than 12 months	(452)	(124)
12 months or more	(458)	(254)
Total	(910)	(378)
Held-to-maturity Securities, Investment Maturities, Fair Value [Abstract]
Fair Value	78,643	83,366
Corporate debt securities
Restricted Cash and Investments [Line Items]
Investments held in Trust	82,302	83,916
Held-to-maturity Securities, Reconciliation to Fair Value [Abstract]
Gross Unrealized Gain	20	309
Gross Unrealized Loss	(1,140)	(434)
Fair Value	81,182	83,791
Estimated fair value
Less than 12 months	66,664	48,952
12 months or more	9,982	10,081
Total	76,646	59,033
Unrealized losses
Less than 12 months	(927)	(311)
12 months or more	(213)	(123)
Total	(1,140)	(434)
Held-to-maturity Securities, Investment Maturities, Fair Value [Abstract]
Fair Value	81,182	83,791
Agency mortgage-backed securities
Restricted Cash and Investments [Line Items]
Investments held in Trust	3,663	4,066
Held-to-maturity Securities, Reconciliation to Fair Value [Abstract]
Gross Unrealized Gain	12	22
Gross Unrealized Loss	(45)	(26)
Fair Value	3,630	4,062
Estimated fair value
Less than 12 months	1,216	1,362
12 months or more	802	888
Total	2,018	2,250
Unrealized losses
Less than 12 months	(22)	(10)
12 months or more	(23)	(16)
Total	(45)	(26)
Held-to-maturity Securities, Investment Maturities, Fair Value [Abstract]
Fair Value	3,630	4,062
U.S. government and agency securities
Restricted Cash and Investments [Line Items]
Investments held in Trust	999	1,000
Held-to-maturity Securities, Reconciliation to Fair Value [Abstract]
Gross Unrealized Gain	0	19
Gross Unrealized Loss	(8)	0
Fair Value	991	1,019
Estimated fair value
Less than 12 months	991
12 months or more	0
Total	991
Unrealized losses
Less than 12 months	(8)
12 months or more	0
Total	(8)
Held-to-maturity Securities, Investment Maturities, Fair Value [Abstract]
Fair Value	991	$ 1,019
Restricted Cash and Investments [Member]
Restricted Cash and Investments [Line Items]
Investments held in Trust	166,255
Held-to-maturity Securities, Reconciliation to Fair Value [Abstract]
Fair Value	164,446
Held-to-maturity Securities, Investment Maturities, Amortized Cost [Abstract]
Due in one year or less	17,960
Due after one year through five years	86,743
Due after five years through ten years	61,552
Held-to-maturity Securities, Investment Maturities, Fair Value [Abstract]
Due in one year or less	17,892
Due after one year through five years	85,910
Due after five years through ten years	60,644
Fair Value	$ 164,446

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