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
	Dec. 31, 2013	Dec. 31, 2012
Finite-Lived Intangible Assets [Line Items]
Amortization of intangibles	$ 43.4	$ 86.6
Customer relationships [Member]
Finite-Lived Intangible Assets [Line Items]
Amortization of intangibles	11.7	10.4
Trade names [Member]
Finite-Lived Intangible Assets [Line Items]
Amortization of intangibles	4.1	3.6
Technology assets [Member]
Finite-Lived Intangible Assets [Line Items]
Amortization of intangibles	4.4	3.1
Definite Lived Intangible Assets [Member]
Finite-Lived Intangible Assets [Line Items]
Amortization of intangibles	$ 20.2	$ 17.1