Retirement Plans - Asset Allocations (Detail) - USD ($) $ in Millions		Dec. 29, 2018	Dec. 30, 2017	Dec. 31, 2016
Schedule Of Other Postretirement Benefits [Line Items]
Fair value of plan assets		$ 254.4	$ 299.6	$ 271.9
Defined Benefit Plan, Plan Assets, Actual Allocation, Percentage		100.00%	100.00%
Equity securities [Member]
Schedule Of Other Postretirement Benefits [Line Items]
Defined Benefit Plan, Plan Assets, Actual Allocation, Percentage		54.40%	57.90%
Equity securities [Member] | Fair Value Measured at Net Asset Value Per Share [Member]
Schedule Of Other Postretirement Benefits [Line Items]
Fair value of plan assets	[1]	$ 138.2	$ 173.4
Fixed income securities [Member]
Schedule Of Other Postretirement Benefits [Line Items]
Defined Benefit Plan, Plan Assets, Actual Allocation, Percentage		38.50%	36.40%
Fixed income securities [Member] | Fair Value Measured at Net Asset Value Per Share [Member]
Schedule Of Other Postretirement Benefits [Line Items]
Fair value of plan assets	[1]	$ 98.0	$ 109.1
Real Estate Investment [Member]
Schedule Of Other Postretirement Benefits [Line Items]
Defined Benefit Plan, Plan Assets, Actual Allocation, Percentage		6.30%	5.30%
Real Estate Investment [Member] | Fair Value Measured at Net Asset Value Per Share [Member]
Schedule Of Other Postretirement Benefits [Line Items]
Fair value of plan assets	[1]	$ 16.1	$ 15.8
Other Investments [Member]
Schedule Of Other Postretirement Benefits [Line Items]
Defined Benefit Plan, Plan Assets, Actual Allocation, Percentage		0.80%	0.40%
Other Investments [Member] | Fair Value, Inputs, Level 3 [Member]
Schedule Of Other Postretirement Benefits [Line Items]
Fair value of plan assets	[2]	$ 2.1	$ 1.3

[1] In accordance with ASC 820, Fair Value Measurement (“ASC 820”), certain investments are measured at fair value using the net asset value per share as a practical expedient. These assets have not been classified in the fair value hierarchy.

[2] In accordance with ASC 820, investments have been measured using valuation techniques in which one or more significant inputs are unobservable (Level 3). See Note 15 for additional information.