PENSION AND OTHER POSTRETIREMENT BENEFITS (Narrative) (Details) - USD ($)	3 Months Ended		9 Months Ended
	Sep. 24, 2017	Sep. 25, 2016	Sep. 24, 2017	Sep. 25, 2016	Dec. 25, 2016
Defined Benefit Plans and Other Postretirement Benefit Plans [Line Items]
Retirement plan expenses	$ 2,800,000	$ 2,300,000	$ 8,000,000	$ 6,900,000
Accumulated benefit obligation, defined benefit pension plans	173,200,000		$ 173,200,000		$ 167,200,000
Weighted average duration of defined benefit obligation			32 years 8 months 18 days
Actuarial loss expected to be recognized in net pension cost, remainder of 2015	$ 200,000		$ 200,000
Fixed income securities | Pooled separate accounts
Defined Benefit Plans and Other Postretirement Benefit Plans [Line Items]
Target plan asset allocations	50.00%		50.00%
Fixed income securities | Common collective trusts funds
Defined Benefit Plans and Other Postretirement Benefit Plans [Line Items]
Target plan asset allocations	30.00%		30.00%
Equity securities | Common collective trusts funds
Defined Benefit Plans and Other Postretirement Benefit Plans [Line Items]
Target plan asset allocations	70.00%		70.00%
Pension Benefits
Defined Benefit Plans and Other Postretirement Benefit Plans [Line Items]
Expected contributions, remainder of 2017 (less than for other postretirement plans)	$ 100,000		$ 100,000
Other Benefits
Defined Benefit Plans and Other Postretirement Benefit Plans [Line Items]
Impact of 0.25% change in discount rate on projected benefit obligation			1,000
Expected contributions, remainder of 2017 (less than for other postretirement plans)	$ 100,000		$ 100,000