Leases (Narrative) (Details) - USD ($) $ in Thousands	3 Months Ended	6 Months Ended
	Jun. 29, 2019	Jun. 29, 2019	Dec. 30, 2018	Dec. 29, 2018
Lessee, Lease, Description [Line Items]
Leases renewal term (up to)	5 years	5 years
Leases termination period (within)		1 year
Operating leases, the weighted-average remaining lease term	6 years 6 months	6 years 6 months
Operating leases, weighted-average discount rate	7.00%	7.00%
Operating lease right-of-use assets	$ 26,092	$ 26,092		$ 0
Total lease liabilities	28,596	28,596		$ 0
Fixed operating lease expenses	1,900	3,900
Operating leases obligation for previously restructured facilities	$ 7,700	$ 7,700
Minimum
Lessee, Lease, Description [Line Items]
Leases remaining term		1 year
Maximum
Lessee, Lease, Description [Line Items]
Leases remaining term		8 years
Accounting Standards Update 2016-02
Lessee, Lease, Description [Line Items]
Operating lease right-of-use assets			$ 29,900
Total lease liabilities			$ 32,300