Components of Net Periodic Benefit Expense Related to Post-Retirement Plans (Detail) (USD $) In Millions, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2014	Sep. 30, 2013	Sep. 30, 2014	Sep. 30, 2013
Pension Plans Defined Benefit [Member]
Defined Benefit Plan Disclosure [Line Items]
Service cost	$ 4.6	$ 4.9	$ 13.8	$ 14.8
Interest cost	4.2	3.4	12.4	10.1
Expected return on plan assets	(3.7)	(3.3)	(10.7)	(9.7)
Amortization of net actuarial loss from earlier periods	1.7	2.8	5.0	8.2
Amortization of net prior service costs from earlier periods	0.2	0.2	0.5	0.5
Net periodic expense	7.0	8.0	21.0	23.9
Benefit Plan Recognized
Other Postretirement Benefit Plans Defined Benefit [Member]
Defined Benefit Plan Disclosure [Line Items]
Service cost	0.5	0.5	1.3	1.3
Interest cost	0.2	0.2	0.7	0.6
Expected return on plan assets			0	0
Amortization of net actuarial loss from earlier periods			0	0
Amortization of net prior service costs from earlier periods			0	0.2
Net periodic expense	0.7	0.7	2.0	2.1
Benefit Plan Recognized