Retirement Plans and Other Post-Retirement Benefits - Additional Information (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Defined Benefit Plan Disclosure [Line Items]
Accumulated benefit obligation for all defined benefit pension plans	$ 537.6	$ 526.7
Defined contribution plans Employees contribution	50.00%
Expense associated with Defined Contribution Plans	$ 2.0	$ 2.1	$ 2.0
Pension Benefits [Member]
Defined Benefit Plan Disclosure [Line Items]
Pension settlement charge	7.3
Pension settlement charge settled	$ 24.2
Discount rates	4.43%	4.65%
Prior service cost as a component of net periodic benefit cost from accumulated other comprehensive income (loss)	$ 2.8
Actuarial net (gain) loss as a component of net periodic benefit cost from accumulated other comprehensive income (loss)	$ 0.2
Pension Benefits [Member] | Minimum [Member]
Defined Benefit Plan Disclosure [Line Items]
Discount rates	1.90%
Pension Benefits [Member] | Maximum [Member]
Defined Benefit Plan Disclosure [Line Items]
Discount rates	4.55%
Other Benefits [Member]
Defined Benefit Plan Disclosure [Line Items]
Discount rates	4.18%	4.38%
Prior service cost as a component of net periodic benefit cost from accumulated other comprehensive income (loss)		$ 11.3
Actuarial net (gain) loss as a component of net periodic benefit cost from accumulated other comprehensive income (loss)		$ 0.6
Other Benefits [Member] | Minimum [Member]
Defined Benefit Plan Disclosure [Line Items]
Discount rates	4.02%
Other Benefits [Member] | Maximum [Member]
Defined Benefit Plan Disclosure [Line Items]
Discount rates	4.21%