Pension and Other Postretirement Benefit Plans (Components of Net Periodic Benefit Cost) (Detail) (USD $) In Millions, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2014	Jun. 30, 2013	Jun. 30, 2014	Jun. 30, 2013
Pension Plans
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Service cost - benefits earned during the period	$ 0.3	$ 0.5	$ 0.7	$ 0.9
Interest cost	8.5	8.0	16.9	15.9
Expected return on plan assets	(9.1)	(8.9)	(18.3)	(17.8)
Recognized net actuarial loss	2.9	3.6	5.8	7.3
Amortization of prior service cost	0.1		0.1
Net periodic pension cost (benefit)	2.7	3.2	5.2	6.3
Postretirement Plans
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Service cost - benefits earned during the period		0.1		0.1
Interest cost	0.2	0.3	0.4	0.8
Recognized net actuarial loss				0.1
Amortization of prior service cost	(0.5)	(1.0)	(0.9)	(1.9)
Net settlement gain		(1.6)		(1.6)
Net periodic pension cost (benefit)	$ (0.3)	$ (2.2)	$ (0.5)	$ (2.5)