Employee Benefits - Additional Information (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Defined Benefit Plan Disclosure [Line Items]
Severance Costs	$ 0.8	$ 2.0	$ 3.3
Metal and Electrical Engineering Industry Pension Fund
Defined Benefit Plan Disclosure [Line Items]
Actual coverage ratio percentage	101.50%
Western Metal Industry Pension Plan
Defined Benefit Plan Disclosure [Line Items]
Contributions by the Company	7.00%	8.00%
Minimum | Metal and Electrical Engineering Industry Pension Fund
Defined Benefit Plan Disclosure [Line Items]
Required coverage ratio percentage	104.30%
Maximum | Metal and Electrical Engineering Industry Pension Fund
Defined Benefit Plan Disclosure [Line Items]
Contributions by the Company	5.00%	5.00%
Maximum | Other Plans
Defined Benefit Plan Disclosure [Line Items]
Contributions by the Company	5.00%
Defined Benefit Pension Plans
Defined Benefit Plan Disclosure [Line Items]
Accumulated unrecognized actuarial gains and losses	10.00%
Contribution to pension plans	$ 70.6	$ 185.7
Expected pension contributions minimum funding requirements	21.2
Annual benefits expected to be paid year one	84.4
Annual benefits expected to be paid year two	87.1
Annual benefits expected to be paid year three	94.0
Annual benefits expected to be paid year four	99.9
Annual benefits expected to be paid year five	106.2
Annual benefits expected to be paid for the five years thereafter	609.7
Unrecognized actuarial loss amount in accumulated other comprehensive loss expected to be amortized next year	30.4
Unrecognized prior service cost amount in accumulated other comprehensive loss expected to be amortized next year	1.3
Accumulated benefit obligation for all pension plans of the Company	2,492.4	$ 2,215.3
Estimated Decrease in Pension Expense for 2017 due to change of method used to estimate service cost and interest cost components of pension expense from a single weighted-average method to an individual spot rate approach	15.0
Defined Benefit Pension Plans | Minimum
Defined Benefit Plan Disclosure [Line Items]
Expected pension contributions by the company to the pension plans in the next year	70.0
Defined Benefit Pension Plans | Maximum
Defined Benefit Plan Disclosure [Line Items]
Expected pension contributions by the company to the pension plans in the next year	$ 100.0
Defined Contribution Plans
Defined Benefit Plan Disclosure [Line Items]
Percentage match for base wages	5.00%	5.00%	5.00%
Defined contribution benefit plans expense	$ 37.9	$ 34.1	$ 36.1