DEFINED BENEFIT RETIREMENT PLAN (Details 2) £ in Thousands, $ in Thousands	12 Months Ended
	Dec. 30, 2017 GBP (£)	Dec. 30, 2017 USD ($)	Dec. 31, 2016 USD ($)	Dec. 26, 2015 USD ($)
Defined Benefit Plan Disclosure [Line Items]
Limit on employer contributions per annum	£ 10,000	$ 13,490
Defined Benefit Plan, Other Costs	£ 1,100	1,484
Plan assets at fair value		18,451	$ 2,380
Plan assets at NAV		575,298	484,287
Total plan assets		593,749	486,667	$ 518,126
Fair Value, Inputs, Level 1 [Member]
Defined Benefit Plan Disclosure [Line Items]
Plan assets at fair value		$ 18,451	2,380
Common stock mutual funds and diversified growth funds
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Target Plan Asset Allocations	50.00%	50.00%
Temporary cash investments
Defined Benefit Plan Disclosure [Line Items]
Plan assets at fair value		$ 17,915	1,900
Temporary cash investments | Fair Value, Inputs, Level 1 [Member]
Defined Benefit Plan Disclosure [Line Items]
Plan assets at fair value		17,915	1,900
Index linked gilts
Defined Benefit Plan Disclosure [Line Items]
Plan assets at NAV		158,011	135,141
Corporate bonds
Defined Benefit Plan Disclosure [Line Items]
Plan assets at NAV		88,905	83,834
Corporate stock
Defined Benefit Plan Disclosure [Line Items]
Plan assets at fair value		536	480
Plan assets at NAV		212,505	165,338
Corporate stock | Fair Value, Inputs, Level 1 [Member]
Defined Benefit Plan Disclosure [Line Items]
Plan assets at fair value		536	480
Diversified growth funds
Defined Benefit Plan Disclosure [Line Items]
Plan assets at NAV		$ 115,877	$ 99,974