REVENUE FROM CONTRACTS WITH CUSTOMERS - Additional Information (Details) - USD ($) $ in Thousands	6 Months Ended
Jun. 30, 2018	Dec. 30, 2017
Revenue from Contract with Customer [Abstract]
Payment terms	30 days
Unpaid advanced client billings	$ 20,000
Contract liabilities (customer contract deposits)	37,543	$ 0
Revenue billed during period	79,000
Revenue recognized during period related to contract liabilities	$ 103,000

Amount of decrease in right to consideration in exchange for good or service transferred to customer when right is conditioned on something other than passage of time from transfer to receivable due to right to consideration becoming unconditional.

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 606
-SubTopic 10
-Section 50
-Paragraph 10
-Subparagraph (d)
-URI http://asc.fasb.org/extlink&oid=109196051&loc=SL49130551-203045

Name:	us-gaap_ContractWithCustomerAssetReclassifiedToReceivable
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration