LEASES AND RELATED PARTY LEASES (Narrative) (Details) - USD ($)		12 Months Ended
	Dec. 27, 2016	Dec. 31, 2017	Dec. 31, 2016	Dec. 27, 2016	Dec. 31, 2015
Operating Leased Assets [Line Items]
Rental expense		$ 12,900,000	$ 10,300,000		$ 10,100,000
Future minimum lease payments, capital leases		0
Production equipment purchased		43,503,000	$ 47,328,000		33,413,000
Related Party
Operating Leased Assets [Line Items]
Rental expense		$ 300,000			$ 100,000
Payment per year to related party lessor				$ 100,000
Production equipment purchased	$ 400,000
Percent of manufacturing facility owned by corporation whose shareholders are trusts whose beneficiaries include family members of company's former chairman		50.00%
Annual rate of lease agreement		$ 300,000
Related Party | Five-Year Option Lease From November 1, 2032 Through October 31, 2037
Operating Leased Assets [Line Items]
Option to extend lease, years		5 years
Period for extended lease		November 1, 2032 through October 31, 2037
Related Party | Five-Year Option Lease From November 1, 2037 Through October 31, 2042
Operating Leased Assets [Line Items]
Option to extend lease, years		5 years
Period for extended lease		November 1, 2037 through October 31, 2042