Retirement Plans - Narrative (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Defined Benefit Plan Disclosure [Line Items]
Reduction of defined benefit plan liability		$ 426.5
Reduction of defined deferred tax assets		351.3
Reduction of defined accumulated other comprehensive loss		906.1
Pension liability, before tax	$ 5.8
Pension liability, after tax	3.6
Reduction in pension obligation		354.8
Pension and postretirement contributions	16.4	22.5	$ 25.6
Defined benefit plan, accumulated benefit obligation	$ 1,032.0	961.1
Threshold for recognition in net periodic benefit costs, percentage of projected benefit obligation or fair value of plan assets	10.00%
Multi-employer pension plan withdrawal obligations
Defined Benefit Plan Disclosure [Line Items]
Other Charges	$ 2.3	2.3	$ 2.2
Hedging Investments
Defined Benefit Plan Disclosure [Line Items]
Target asset allocation percentage	45.00%
Return Seeking Securities
Defined Benefit Plan Disclosure [Line Items]
Target asset allocation percentage	55.00%
Selling, General and Administrative Expenses
Defined Benefit Plan Disclosure [Line Items]
Pension and other post retirement non-cash settlement expense		21.1
Net Earnings from Discontinued Operations
Defined Benefit Plan Disclosure [Line Items]
Pension and other post retirement non-cash settlement expense		77.7
Lump Sum Pension Payment Or Annuity
Defined Benefit Plan Disclosure [Line Items]
Benefits Paid		328.4
Pension Plans, Defined Benefit
Defined Benefit Plan Disclosure [Line Items]
Reduction in pension obligation	$ 0.0	0.0
Benefits Paid	44.6	129.7
Pension and postretirement contributions	8.6
Medicare reimbursements	0.0	0.0
Other Postretirement Benefit Plans, Defined Benefit
Defined Benefit Plan Disclosure [Line Items]
Reduction in pension obligation	0.0	33.8
Benefits Paid	34.8	32.5
Pension and postretirement contributions	7.8
Reduction in pension liability due to curtailment		35.0
Medicare reimbursements	5.0	5.4
Other Postretirement Benefit Plans, Defined Benefit | Selling, General and Administrative Expenses
Defined Benefit Plan Disclosure [Line Items]
Curtailment gain		3.3
Other Postretirement Benefit Plans, Defined Benefit | Cost of Sales
Defined Benefit Plan Disclosure [Line Items]
Curtailment gain		$ 16.2
Pension and Retirement Benefit Plans
Defined Benefit Plan Disclosure [Line Items]
Pension and other postretirement expected contributions for next year	16.0
EGWP
Defined Benefit Plan Disclosure [Line Items]
Medicare reimbursements	$ 5.0