Lease Commitments (Narrative) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 27, 2019	Dec. 28, 2018	Dec. 29, 2017
Lessee Lease Description [Line Items]
Weighted average remaining lease term	5 years
Weighted average discount rate	4.00%
Operating lease payments	$ 2.5
Lease expense	$ 2.8	$ 2.8	$ 2.4
Lessee, operating lease not yet commenced description	As of December 27, 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
London Office Lease [Member]
Lessee Lease Description [Line Items]
Operating lease opt-out option	5 years
Minimum [Member]
Lessee Lease Description [Line Items]
Operating leases terms	1 year
Maximum [Member]
Lessee Lease Description [Line Items]
Operating leases terms	10 years