Reinsurance - Effect of Reinsurance on Premiums Earned, Benefits Incurred and Reserve Changes (Detail) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2011
Insurance Premiums:
Direct	$ 414.7	$ 415.9	$ 226.3
Assumed	32.8	47.2	22.8
Ceded	(328.2)	(369.5)	(160.4)
Benefits and Other Changes in Insurance Policy Reserves:
Direct	776.5	1,033.4	392.1
Assumed	23.3	34.9	19.5
Ceded	(268.0)	(290.9)	(164.0)
Net	531.8	777.4	247.6
Life Insurance Product Line
Insurance Premiums:
Direct	279.2	298.0	157.8
Assumed	32.8	47.2	22.8
Ceded	(253.2)	(289.9)	(141.6)
Net	$ 58.8	$ 55.3	$ 39.0