REVENUE FROM CONTRACTS WITH CUSTOMERS - Schedule of Client Receivables, Contract Assets and Contract Liabilities (Details) - USD ($) $ in Thousands	Mar. 30, 2019	Dec. 29, 2018
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Client receivables	$ 377,188	$ 370,131
Contract assets (unbilled revenue)	120,607	105,216
Contract liabilities (current and long-term deferred revenue)	166,705
Contract liabilities (customer contract deposits)	$ 32,380	38,245
Calculated under Revenue Guidance in Effect before Topic 606
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Client receivables		370,131
Contract assets (unbilled revenue)		105,216
Contract liabilities (current and long-term deferred revenue)		$ 179,559