Reinsurance - Effect of Reinsurance on Premiums Earned, Benefits Incurred and Reserve Changes (Detail) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Sep. 30, 2014	Sep. 30, 2013	Sep. 30, 2012
Insurance Premiums:
Direct	$ 409.3	$ 414.7	$ 415.9
Assumed	35.9	32.8	47.2
Ceded	(317.5)	(328.2)	(369.5)
Benefits and Other Changes in Insurance Policy Reserves:
Net	852.7	531.8	777.4
Life Insurance Product Line
Insurance Premiums:
Direct	266.8	279.2	298.0
Assumed	35.9	32.8	47.2
Ceded	(246.1)	(253.2)	(289.9)
Net	56.6	58.8	55.3
Benefits and Other Changes in Insurance Policy Reserves:
Direct	1,103.3	776.5	1,033.4
Assumed	33.0	23.3	34.9
Ceded	(283.6)	(268.0)	(290.9)
Net	$ 852.7	$ 531.8	$ 777.4