Postretirement Benefit Plans - Defined Contribution Plans - Additional Information (Detail)	Sep. 30, 2015 USD ($)
Defined Benefit Pension Plan [Member]
Defined Contribution Plan Disclosure [Line Items]
Balance of trust assets	$ 1,686,000

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.

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