Profit Sharing, Retirement Savings Plans and Defined Benefit Pension Plans - Fair Values of Pension Plan Assets, by Asset Category and Level of Fair Values (Detail) - USD ($) $ in Millions	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	$ 776.2	$ 771.8	$ 760.3
Level 1
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	5.6	4.3
Level 2
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	681.1	666.8
Level 3
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	89.5	100.7
Cash and cash equivalents
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	7.5	5.8
Cash and cash equivalents | Level 1
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	5.6	4.3
Cash and cash equivalents | Level 2
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	1.9	1.5
Cash and cash equivalents | Level 3
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0.0	0.0
Fixed income funds
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	385.9	371.9
Fixed income funds | Level 1
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0.0	0.0
Fixed income funds | Level 2
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	385.9	371.9
Fixed income funds | Level 3
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0.0	0.0
Equity funds
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	257.6	258.8
Equity funds | Level 1
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0.0	0.0
Equity funds | Level 2
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	257.6	258.8
Equity funds | Level 3
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0.0	0.0
Other
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	125.2	135.3
Other | Level 1
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0.0	0.0
Other | Level 2
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	35.7	34.6
Other | Level 3
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	$ 89.5	$ 100.7