Defined Benefit Plans - Components of Consolidated Net Periodic Benefit and Deferred Compensation Benefit Costs and Contributions Made (Detail) (USD $) In Millions, unless otherwise specified	3 Months Ended		9 Months Ended
	Jun. 30, 2014	Jun. 30, 2013	Jun. 30, 2014	Jun. 30, 2013
Defined Benefit Plan Disclosure [Line Items]
Document Period End Date			Jun. 30, 2014
Net periodic benefit cost [Member]
Defined Benefit Plan, Net Periodic Benefit Cost [Abstract]
Service cost	$ 0.9	$ 0.9	$ 2.9	$ 2.6
Interest cost	2.6	2.5	8.6	7.8
Expected return on assets	(2.5)	(2.5)	(8.5)	(7.4)
Recognized net actuarial loss	0.3	0.5	1.1	1.6
Defined Benefit Plan, Contributions by Plan Participants	0	0	0	(0.1)
Net periodic benefit expense	1.3	1.4	4.1	4.5
Contributions made during period	$ 4.0	$ 1.3	$ 9.6	$ 3.2