Retirement Plans - Components of Net Periodic Pension Benefit Cost and Other Changes in Plan Assets and Obligations Recognized in Earnings and Other Comprehensive Earnings (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Compensation and Retirement Disclosure [Abstract]
Service cost	$ 1.5	$ 1.1	$ 0.7
Interest cost on benefit obligation	10.8	10.8	12.7
Expected return on plan assets	(14.6)	(15.3)	(18.7)
Amortization of net loss	5.3	6.2	2.3
Settlement			12.0
Net periodic benefit cost	3.0	2.8	9.0
Net loss incurred	1.4	2.9	42.5
Settlement recognition			(12.0)
Amortization of net loss	(5.3)	(6.2)	(2.3)
Total recognized in other comprehensive loss	(3.9)	(3.3)	28.2
Total recognized in net periodic pension cost and other comprehensive loss	(0.9)	(0.5)	37.2
Amortization of net loss	$ 5.5	$ 5.9	$ 6.0