Retirement Plans - Reconciliation of Benefit Obligation, Plan Assets and Funded Status of Plans (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Defined Benefit Plan, Change in Benefit Obligation [Roll Forward]
Plan amendments and other		$ (354.8)
Pension Benefits
Defined Benefit Plan, Change in Benefit Obligation [Roll Forward]
Benefit obligation at beginning of year	$ 974.7	3,932.3
Service cost	0.7	1.0	$ 1.7
Interest cost	31.6	105.7	170.4
Plan participants' contributions	0.0	0.0
Medicare reimbursements	0.0	0.0
Actuarial loss	53.9	349.5
Plan amendments and other	0.0	0.0
Settlements	(5.9)	(304.4)
Foreign currency translation	34.4	(40.5)
Benefits paid	(44.6)	(129.7)
Divestitures	0.0	(23.6)
Benefit obligation at end of year	1,044.8	974.7	3,932.3
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Fair value of plan assets at beginning of year	875.4	3,424.1
Actual return on assets	106.0	424.1
Settlements	(6.3)	(304.4)
Employer contributions	8.6	12.8
Medicare reimbursements	0.0	0.0
Plan participants' contributions	0.0	0.0
Divestitures	0.0	(16.8)
Foreign currency translation	34.4	(45.6)
Benefits paid	(44.6)	(129.7)
Fair value of plan assets at end of year	979.3	875.4	3,424.1
Total net pension and OPEB liability recognized as of December 31	(65.5)	(99.3)
Pension Benefits | Discontinued Operations
Defined Benefit Plan, Change in Benefit Obligation [Roll Forward]
Divestitures	0.0	(2,915.6)
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Divestitures	5.8	(2,489.1)
Other Postretirement Benefits
Defined Benefit Plan, Change in Benefit Obligation [Roll Forward]
Benefit obligation at beginning of year	345.0	373.8
Service cost	1.3	3.8	4.7
Interest cost	11.1	11.7	15.9
Plan participants' contributions	9.0	9.4
Medicare reimbursements	5.0	5.4
Actuarial loss	3.0	5.9
Plan amendments and other	0.0	(33.8)
Settlements	0.0	0.0
Foreign currency translation	2.8	1.3
Benefits paid	(34.8)	(32.5)
Divestitures	0.0	0.0
Benefit obligation at end of year	342.4	345.0	373.8
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Fair value of plan assets at beginning of year	210.3	205.5
Actual return on assets	31.3	14.8
Settlements	0.0	0.0
Employer contributions	7.8	7.7
Medicare reimbursements	5.0	5.4
Plan participants' contributions	9.0	9.4
Divestitures	0.0	0.0
Foreign currency translation	0.0	0.0
Benefits paid	(34.8)	(32.5)
Fair value of plan assets at end of year	228.6	210.3	$ 205.5
Total net pension and OPEB liability recognized as of December 31	(113.8)	(134.7)
Other Postretirement Benefits | Discontinued Operations
Defined Benefit Plan, Change in Benefit Obligation [Roll Forward]
Divestitures	0.0	0.0
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Divestitures	$ 0.0	$ 0.0