Segment Data - Additional Information (Detail) $ in Millions	3 Months Ended	6 Months Ended
Mar. 31, 2016 USD ($)	Mar. 31, 2015 USD ($)	Mar. 31, 2016 USD ($) Segment	Mar. 31, 2015 USD ($)
Segment Reporting Information [Line Items]
Asset Impairment Charges	$ 27.6	$ 214.6	$ 90.8	$ 464.4
Number of reporting segments \| Segment			4
Asset Management segment [Member]
Segment Reporting Information [Line Items]
Asset Impairment Charges			$ 15.1	$ 62.6

Amount of write-down of assets recognized in the income statement. Includes, but is not limited to, losses from tangible assets, intangible assets and goodwill.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 360
-SubTopic 10
-Section 45
-Paragraph 4
-URI http://asc.fasb.org/extlink&oid=51824106&loc=d3e2420-110228

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 230
-SubTopic 10
-Section 45
-Paragraph 28
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=56944662&loc=d3e3602-108585

Name:	us-gaap_AssetImpairmentCharges
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration