Employee Future Benefits (Allocation of Plan Assets) (Details) - Pension Plan - USD ($) $ in Thousands	Dec. 29, 2019	Dec. 30, 2018	Dec. 31, 2017
UNITED KINGDOM
Defined Benefit Plan Disclosure [Line Items]
Allocation of plan assets	$ 26,748	$ 22,307	$ 25,141
Allocation of plan assets, percent	100.00%	100.00%
UNITED KINGDOM | Equity Securities
Defined Benefit Plan Disclosure [Line Items]
Allocation of plan assets	$ 10,297	$ 10,207
Allocation of plan assets, percent	38.50%	45.80%
Target plan asset allocations, percent	50.00%
UNITED KINGDOM | Debt Securities
Defined Benefit Plan Disclosure [Line Items]
Allocation of plan assets	$ 13,600	$ 11,909
Allocation of plan assets, percent	50.80%	53.30%
Target plan asset allocations, percent	50.00%
UNITED KINGDOM | Other
Defined Benefit Plan Disclosure [Line Items]
Allocation of plan assets	$ 2,851	$ 191
Allocation of plan assets, percent	10.70%	0.90%
UNITED STATES
Defined Benefit Plan Disclosure [Line Items]
Allocation of plan assets	$ 79,422	$ 86,992	$ 92,716
Allocation of plan assets, percent	100.00%	100.00%
UNITED STATES | Equity Securities
Defined Benefit Plan Disclosure [Line Items]
Allocation of plan assets	$ 47,017	$ 51,412
Allocation of plan assets, percent	59.20%	59.10%
Target plan asset allocations, percent	60.00%
UNITED STATES | Debt Securities
Defined Benefit Plan Disclosure [Line Items]
Allocation of plan assets	$ 29,863	$ 32,361
Allocation of plan assets, percent	37.60%	37.20%
Target plan asset allocations, percent	38.00%
UNITED STATES | Other
Defined Benefit Plan Disclosure [Line Items]
Allocation of plan assets	$ 2,542	$ 3,219
Allocation of plan assets, percent	3.20%	3.70%
Target plan asset allocations, percent	2.00%