Reinsurance - Effect of Reinsurance on Premiums Earned, Benefits Incurred and Reserve Changes (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
Reinsurance Disclosures [Abstract]
Document Period End Date			Jun. 30, 2014
Insurance Premiums:
Direct	$ 65.6	$ 69.9	$ 200.3	$ 212.3
Assumed	8.8	9.1	27.6	24.5
Ceded	(61.1)	(60.0)	(185.9)	(189.9)
Net	13.3	19.0	42.0	46.9
Benefits and Other Changes in Insurance Policy Reserves:
Direct	324.0	150.9	876.8	579.8
Assumed	12.0	8.2	27.3	15.7
Ceded	(70.9)	(51.9)	(207.8)	(163.8)
Net	$ 265.1	$ 107.2	$ 696.3	$ 431.7