Commitments - Additional Information (Detail) $ in Millions	12 Months Ended
Sep. 30, 2015 USD ($) executive	Sep. 30, 2014 USD ($)	Sep. 30, 2013 USD ($)
Commitments and Contingencies Disclosure [Abstract]
Rent expense under operating leases \| $	$ 20.7	$ 19.4	$ 22.1
Number of executives in a management agreement providing for certain payments and other benefits in the event of a qualified change	23

Rental expense for the reporting period incurred under operating leases, including minimum and any contingent rent expense, net of related sublease income.

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 840

-SubTopic 20

-Section 50

-Paragraph 1

-URI http://asc.fasb.org/extlink&oid=6453985&loc=d3e41499-112717

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