Components of Net Pension (Expense) Income (Detail) (USD $) In Millions, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013	Sep. 30, 2012
Compensation and Retirement Disclosure [Abstract]
Expected employer contribution	$ 1.5		$ 1.5
Components of net pension expense
Service cost	0.7	0.8	2.4	2.2
Interest cost	3.0	3.2	9.0	9.5
Expected return on plan assets	(3.8)	(3.7)	(11.4)	(11.0)
Recognized net actuarial loss	1.5	1.6	4.7	4.7
Net pension expense	$ 1.4	$ 1.9	$ 4.7	$ 5.4