Goodwill and Intangibles, including DAC and VOBA - Summary of Amortization Expense of Definite Lived Intangible Assets (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
Finite-Lived Intangible Assets [Line Items]
Amortization of intangibles	$ 40.7	$ 85.0	$ 121.5	$ 220.6
Customer relationships [Member]
Finite-Lived Intangible Assets [Line Items]
Amortization of intangibles	11.7	11.6	35.0	33.3
Trade names [Member]
Finite-Lived Intangible Assets [Line Items]
Amortization of intangibles	4.1	4.3	12.3	12.2
Technology assets [Member]
Finite-Lived Intangible Assets [Line Items]
Amortization of intangibles	4.7	4.4	13.9	12.0
Definite Lived Intangible Assets [Member]
Finite-Lived Intangible Assets [Line Items]
Amortization of intangibles	$ 20.5	$ 20.3	$ 61.2	$ 57.5