FAIR VALUE MEASUREMENTS (Details) - Fair value, measurements, recurring - USD ($) $ in Thousands	Dec. 31, 2017	Jan. 01, 2017
Assets:
Total assets	$ 15,635	$ 14,692
Level 1
Assets:
Total assets	7,176	1,338
Level 2
Assets:
Total assets	8,459	13,354
Level 3
Assets:
Total assets	0	0
Money market funds
Assets:
Money market funds	15,635	14,692
Money market funds | Level 1
Assets:
Money market funds	7,176	1,338
Money market funds | Level 2
Assets:
Money market funds	8,459	13,354
Money market funds | Level 3
Assets:
Money market funds	$ 0	$ 0