Goodwill and Intangibles, including DAC and VOBA, net - Summary of Amortization Expense of Definite Lived Intangible Assets (Detail) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Sep. 30, 2014	Sep. 30, 2013	Sep. 30, 2012
Finite-Lived Intangible Assets [Line Items]
Amortization of intangibles	$ 179.2	$ 260.1	$ 224.3
Customer relationships
Finite-Lived Intangible Assets [Line Items]
Amortization of intangibles	46.7	44.9	40.2
Trade names
Finite-Lived Intangible Assets [Line Items]
Amortization of intangibles	16.4	16.6	14.4
Technology assets
Finite-Lived Intangible Assets [Line Items]
Amortization of intangibles	18.6	16.3	9.1
Definite Lived Intangible Assets
Finite-Lived Intangible Assets [Line Items]
Amortization of intangibles	$ 81.7	$ 77.8	$ 63.7