Retirement and Other Employee Benefits - Fair Values of Plan Assets by Asset Category (Detail) - USD ($) $ in Millions	Dec. 27, 2019	Dec. 28, 2018	Dec. 29, 2017
Defined Benefit Plan Disclosure [Line Items]
Fair values of plan assets		$ 11.9
Fixed income securities
Defined Benefit Plan Disclosure [Line Items]
Fair values of plan assets		5.4
Value securities
Defined Benefit Plan Disclosure [Line Items]
Fair values of plan assets		2.2
Growth securities
Defined Benefit Plan Disclosure [Line Items]
Fair values of plan assets		4.3
Quoted Prices in Active Markets for Identical Assets (Level 1)
Defined Benefit Plan Disclosure [Line Items]
Fair values of plan assets		11.9
Quoted Prices in Active Markets for Identical Assets (Level 1) | Fixed income securities
Defined Benefit Plan Disclosure [Line Items]
Fair values of plan assets		5.4
Quoted Prices in Active Markets for Identical Assets (Level 1) | Value securities
Defined Benefit Plan Disclosure [Line Items]
Fair values of plan assets		2.2
Quoted Prices in Active Markets for Identical Assets (Level 1) | Growth securities
Defined Benefit Plan Disclosure [Line Items]
Fair values of plan assets		4.3
Significant Observable Inputs (Level 2)
Defined Benefit Plan Disclosure [Line Items]
Fair values of plan assets		0.0
Significant Observable Inputs (Level 2) | Fixed income securities
Defined Benefit Plan Disclosure [Line Items]
Fair values of plan assets		0.0
Significant Observable Inputs (Level 2) | Value securities
Defined Benefit Plan Disclosure [Line Items]
Fair values of plan assets		0.0
Significant Observable Inputs (Level 2) | Growth securities
Defined Benefit Plan Disclosure [Line Items]
Fair values of plan assets		0.0
Significant Unobservable Inputs (Level 3)
Defined Benefit Plan Disclosure [Line Items]
Fair values of plan assets		0.0
Significant Unobservable Inputs (Level 3) | Fixed income securities
Defined Benefit Plan Disclosure [Line Items]
Fair values of plan assets		0.0
Significant Unobservable Inputs (Level 3) | Value securities
Defined Benefit Plan Disclosure [Line Items]
Fair values of plan assets		0.0
Significant Unobservable Inputs (Level 3) | Growth securities
Defined Benefit Plan Disclosure [Line Items]
Fair values of plan assets		0.0
United States | Pension plans
Defined Benefit Plan Disclosure [Line Items]
Fair values of plan assets	$ 13.0	11.9	$ 13.9
United States | Pension plans | Fixed income securities
Defined Benefit Plan Disclosure [Line Items]
Fair values of plan assets	5.6
United States | Pension plans | Value securities
Defined Benefit Plan Disclosure [Line Items]
Fair values of plan assets	2.9
United States | Pension plans | Growth securities
Defined Benefit Plan Disclosure [Line Items]
Fair values of plan assets	4.5
United States | Pension plans | Quoted Prices in Active Markets for Identical Assets (Level 1)
Defined Benefit Plan Disclosure [Line Items]
Fair values of plan assets	13.0
United States | Pension plans | Quoted Prices in Active Markets for Identical Assets (Level 1) | Fixed income securities
Defined Benefit Plan Disclosure [Line Items]
Fair values of plan assets	5.6
United States | Pension plans | Quoted Prices in Active Markets for Identical Assets (Level 1) | Value securities
Defined Benefit Plan Disclosure [Line Items]
Fair values of plan assets	2.9
United States | Pension plans | Quoted Prices in Active Markets for Identical Assets (Level 1) | Growth securities
Defined Benefit Plan Disclosure [Line Items]
Fair values of plan assets	4.5
United States | Pension plans | Significant Observable Inputs (Level 2)
Defined Benefit Plan Disclosure [Line Items]
Fair values of plan assets	0.0
United States | Pension plans | Significant Observable Inputs (Level 2) | Fixed income securities
Defined Benefit Plan Disclosure [Line Items]
Fair values of plan assets	0.0
United States | Pension plans | Significant Observable Inputs (Level 2) | Value securities
Defined Benefit Plan Disclosure [Line Items]
Fair values of plan assets	0.0
United States | Pension plans | Significant Observable Inputs (Level 2) | Growth securities
Defined Benefit Plan Disclosure [Line Items]
Fair values of plan assets	0.0
United States | Pension plans | Significant Unobservable Inputs (Level 3)
Defined Benefit Plan Disclosure [Line Items]
Fair values of plan assets	0.0
United States | Pension plans | Significant Unobservable Inputs (Level 3) | Fixed income securities
Defined Benefit Plan Disclosure [Line Items]
Fair values of plan assets	0.0
United States | Pension plans | Significant Unobservable Inputs (Level 3) | Value securities
Defined Benefit Plan Disclosure [Line Items]
Fair values of plan assets	0.0
United States | Pension plans | Significant Unobservable Inputs (Level 3) | Growth securities
Defined Benefit Plan Disclosure [Line Items]
Fair values of plan assets	0.0
United Kingdom | Pension plans
Defined Benefit Plan Disclosure [Line Items]
Fair values of plan assets	58.0	52.3	$ 61.3
United Kingdom | Pension plans | Cash
Defined Benefit Plan Disclosure [Line Items]
Fair values of plan assets	0.5	0.8
United Kingdom | Pension plans | United Kingdom companies
Defined Benefit Plan Disclosure [Line Items]
Fair values of plan assets	0.0	4.5
United Kingdom | Pension plans | Diversified growth funds
Defined Benefit Plan Disclosure [Line Items]
Fair values of plan assets	16.7	17.5
United Kingdom | Pension plans | Other international companies
Defined Benefit Plan Disclosure [Line Items]
Fair values of plan assets	9.2	15.0
United Kingdom | Pension plans | United Kingdom government bonds
Defined Benefit Plan Disclosure [Line Items]
Fair values of plan assets	13.0	6.1
United Kingdom | Pension plans | Liability-driven investments
Defined Benefit Plan Disclosure [Line Items]
Fair values of plan assets	18.6	8.4
United Kingdom | Pension plans | Quoted Prices in Active Markets for Identical Assets (Level 1)
Defined Benefit Plan Disclosure [Line Items]
Fair values of plan assets	0.5	0.8
United Kingdom | Pension plans | Quoted Prices in Active Markets for Identical Assets (Level 1) | Cash
Defined Benefit Plan Disclosure [Line Items]
Fair values of plan assets	0.5	0.8
United Kingdom | Pension plans | Quoted Prices in Active Markets for Identical Assets (Level 1) | United Kingdom companies
Defined Benefit Plan Disclosure [Line Items]
Fair values of plan assets	0.0	0.0
United Kingdom | Pension plans | Quoted Prices in Active Markets for Identical Assets (Level 1) | Diversified growth funds
Defined Benefit Plan Disclosure [Line Items]
Fair values of plan assets	0.0	0.0
United Kingdom | Pension plans | Quoted Prices in Active Markets for Identical Assets (Level 1) | Other international companies
Defined Benefit Plan Disclosure [Line Items]
Fair values of plan assets	0.0	0.0
United Kingdom | Pension plans | Quoted Prices in Active Markets for Identical Assets (Level 1) | United Kingdom government bonds
Defined Benefit Plan Disclosure [Line Items]
Fair values of plan assets	0.0	0.0
United Kingdom | Pension plans | Quoted Prices in Active Markets for Identical Assets (Level 1) | Liability-driven investments
Defined Benefit Plan Disclosure [Line Items]
Fair values of plan assets	0.0	0.0
United Kingdom | Pension plans | Significant Observable Inputs (Level 2)
Defined Benefit Plan Disclosure [Line Items]
Fair values of plan assets	57.5	51.5
United Kingdom | Pension plans | Significant Observable Inputs (Level 2) | Cash
Defined Benefit Plan Disclosure [Line Items]
Fair values of plan assets	0.0	0.0
United Kingdom | Pension plans | Significant Observable Inputs (Level 2) | United Kingdom companies
Defined Benefit Plan Disclosure [Line Items]
Fair values of plan assets	0.0	4.5
United Kingdom | Pension plans | Significant Observable Inputs (Level 2) | Diversified growth funds
Defined Benefit Plan Disclosure [Line Items]
Fair values of plan assets	16.7	17.5
United Kingdom | Pension plans | Significant Observable Inputs (Level 2) | Other international companies
Defined Benefit Plan Disclosure [Line Items]
Fair values of plan assets	9.2	15.0
United Kingdom | Pension plans | Significant Observable Inputs (Level 2) | United Kingdom government bonds
Defined Benefit Plan Disclosure [Line Items]
Fair values of plan assets	13.0	6.1
United Kingdom | Pension plans | Significant Observable Inputs (Level 2) | Liability-driven investments
Defined Benefit Plan Disclosure [Line Items]
Fair values of plan assets	18.6	8.4
United Kingdom | Pension plans | Significant Unobservable Inputs (Level 3)
Defined Benefit Plan Disclosure [Line Items]
Fair values of plan assets	0.0	0.0
United Kingdom | Pension plans | Significant Unobservable Inputs (Level 3) | Cash
Defined Benefit Plan Disclosure [Line Items]
Fair values of plan assets	0.0	0.0
United Kingdom | Pension plans | Significant Unobservable Inputs (Level 3) | United Kingdom companies
Defined Benefit Plan Disclosure [Line Items]
Fair values of plan assets	0.0	0.0
United Kingdom | Pension plans | Significant Unobservable Inputs (Level 3) | Diversified growth funds
Defined Benefit Plan Disclosure [Line Items]
Fair values of plan assets	0.0	0.0
United Kingdom | Pension plans | Significant Unobservable Inputs (Level 3) | Other international companies
Defined Benefit Plan Disclosure [Line Items]
Fair values of plan assets	0.0	0.0
United Kingdom | Pension plans | Significant Unobservable Inputs (Level 3) | United Kingdom government bonds
Defined Benefit Plan Disclosure [Line Items]
Fair values of plan assets	0.0	0.0
United Kingdom | Pension plans | Significant Unobservable Inputs (Level 3) | Liability-driven investments
Defined Benefit Plan Disclosure [Line Items]
Fair values of plan assets	$ 0.0	$ 0.0