Leases (Narrative) (Details) $ in Millions	3 Months Ended	6 Months Ended
	Jun. 28, 2019 USD ($)	Jun. 28, 2019 USD ($)
Lessee Lease Description [Line Items]
Weighted average remaining lease term	5 years 3 months 18 days	5 years 3 months 18 days
Weighted average discount rate	4.00%	4.00%
Operating lease payments	$ 0.7	$ 1.4
Lessee, operating lease not yet commenced description		As of June 28, 2019, the Company does not have any additional operating leases that have not yet commenced that create significant rights and obligations for the Company.
Five Year Opt-Out Option for London Office Lease [Member]
Lessee Lease Description [Line Items]
Weighted average remaining lease term	3 years 2 months 12 days	3 years 2 months 12 days
London Office Lease [Member]
Lessee Lease Description [Line Items]
Operating lease opt-out option	5 years	5 years
Minimum [Member]
Lessee Lease Description [Line Items]
Operating leases terms	1 year	1 year
Maximum [Member]
Lessee Lease Description [Line Items]
Operating leases terms	10 years	10 years