SEGMENT AND GEOGRAPHICAL INFORMATION - Unallocated Corporate Assets (Details) - USD ($) $ in Thousands	Dec. 31, 2021	Jan. 01, 2021	Dec. 27, 2019
Assets:
Cash and cash equivalents	$ 11,221	$ 28,405
Accounts receivable, net	67,211	53,104
Prepaid expenses	4,972	5,564
Goodwill	130,124	130,124	$ 127,647
Other receivables	6,267	6,405
Equipment and leasehold improvements, net	16,757	12,506
Right-of-use assets	15,177	20,130
Other	13,843	5,993
Deferred income taxes	16,849	14,111
Corporate, Non-Segment [Member]
Assets:
Cash and cash equivalents	11,221	28,405
Accounts receivable, net	(40,441)	(12,144)
Prepaid expenses	2,811	2,422
Intercompany receivables	1,131,100	691,440
Goodwill	2	2
Other receivables	4,328	4,409
Equipment and leasehold improvements, net	1,190	1,585
Investments in subsidiaries	36,084	26,576
Right-of-use assets	452	809
Other	399	444
Deferred income taxes	16,849	14,111
Total assets	$ 1,163,995	$ 758,059