Goodwill and Intangibles, including DAC and VOBA - Summary of Definite Lived Intangible Assets (Detail) (USD $) In Millions, unless otherwise specified	6 Months Ended
Mar. 31, 2015	Sep. 30, 2014
Finite-Lived Intangible Assets [Line Items]
Cost	1,272.2	$ 1,240.4
Accumulated Amortization	(357.3)	(323.2)
Net	914.9us-gaap_FiniteLivedIntangibleAssetsNet	917.2us-gaap_FiniteLivedIntangibleAssetsNet
Minimum [Member]
Finite-Lived Intangible Assets [Line Items]
Amortizable Life	1 year
Maximum [Member]
Finite-Lived Intangible Assets [Line Items]
Amortizable Life	20 years
Customer Relationships [Member]
Finite-Lived Intangible Assets [Line Items]
Cost	903.0	877.1
Accumulated Amortization	(221.2)	(204.6)
Net	681.8	672.5
Customer Relationships [Member] \| Minimum [Member]
Finite-Lived Intangible Assets [Line Items]
Amortizable Life	15 years
Customer Relationships [Member] \| Maximum [Member]
Finite-Lived Intangible Assets [Line Items]
Amortizable Life	20 years
Trade Names [Member]
Finite-Lived Intangible Assets [Line Items]
Cost	173.7	171.1
Accumulated Amortization	(69.1)	(61.0)
Net	104.6	110.1
Trade Names [Member] \| Minimum [Member]
Finite-Lived Intangible Assets [Line Items]
Amortizable Life	1 year
Trade Names [Member] \| Maximum [Member]
Finite-Lived Intangible Assets [Line Items]
Amortizable Life	12 years
Technology assets [Member]
Finite-Lived Intangible Assets [Line Items]
Cost	195.5	192.2
Accumulated Amortization	(67.0)	(57.6)
Net	128.5	$ 134.6
Technology assets [Member] \| Minimum [Member]
Finite-Lived Intangible Assets [Line Items]
Amortizable Life	4 years
Technology assets [Member] \| Maximum [Member]
Finite-Lived Intangible Assets [Line Items]
Amortizable Life	17 years

Accumulated amount of amortization of assets, excluding financial assets and goodwill, lacking physical substance with a finite life.

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 350

-SubTopic 30

-Section 50

-Paragraph 2

-Subparagraph (a)(1)

-URI http://asc.fasb.org/extlink&oid=26713463&loc=d3e16323-109275

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- Definition

Amount before amortization of assets, excluding financial assets and goodwill, lacking physical substance with a finite life.

+ References

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- Definition

Amount after amortization of assets, excluding financial assets and goodwill, lacking physical substance with a finite life.

+ References

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- Definition

Useful life of finite-lived intangible assets, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

+ References

No definition available.

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