Components Of Net Periodic Benefit Cost (Detail) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Pension Plans, Defined Benefit
Defined Benefit Plan Disclosure [Line Items]
Service cost	$ 0.9	$ 0.9	$ 1.7
Interest cost	4.2	4.6	6.9
Expected return on plan assets	(3.9)	(4.3)	(5.1)
Amortization of prior service cost	0	0	0
Recognized actuarial loss (gain)	0.2	0	0.7
Settlement (gain) loss	0	0	24.3
Net periodic benefit cost	1.4	1.2	28.5
Other Postretirement Benefit Plans, Defined Benefit
Defined Benefit Plan Disclosure [Line Items]
Service cost	0.4	0.4	0.3
Interest cost	1.2	1.3	1.3
Expected return on plan assets	0	0	0
Amortization of prior service cost	(0.1)	0.1	0.1
Recognized actuarial loss (gain)	0.2	0	0
Settlement (gain) loss	0	0	0
Net periodic benefit cost	$ 1.7	$ 1.8	$ 1.7