Components of Net Pension (Expense) Income (Detail) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2016	Jun. 30, 2015	Jun. 30, 2016	Jun. 30, 2015
Compensation and Retirement Disclosure [Abstract]
Expected employer contribution			$ 1.8
Components of net pension expense
Service cost	$ 1.1	$ 1.0	2.3	$ 2.0
Interest cost	3.0	3.3	5.9	6.5
Expected return on plan assets	(3.2)	(4.2)	(6.5)	(8.3)
Recognized net actuarial loss	1.2	1.5	2.4	3.0
Net pension expense	$ 2.1	$ 1.6	$ 4.1	$ 3.2