Leases - Schedule of lease cost (Details) $ in Thousands	12 Months Ended
	Dec. 28, 2019 USD ($)
Lessee, Lease, Description [Line Items]
Total lease cost	$ 12,881
Facilities and facilities related
Lessee, Lease, Description [Line Items]
Operating lease cost	11,538
Depreciation and Amortization
Lessee, Lease, Description [Line Items]
Amortization of right of use assets	1,245
Interest expense
Lessee, Lease, Description [Line Items]
Interest on lease liabilities	$ 98