Consolidating Condensed Financial Information of Guarantor Subsidiaries - Additional Information (Detail)	12 Months Ended
Sep. 30, 2017
Guarantor Subsidiaries
Condensed Financial Statements, Captions [Line Items]
Collective ownership percentage on guarantor subsidiaries	100.00%

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

No definition available.

Name:	us-gaap_CondensedFinancialStatementsCaptionsLineItems
Namespace Prefix:	us-gaap_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration