v3.8.0.1

Amounts Reclassified Out of Accumulated Other Comprehensive Income - Additional Information (Detail) - USD ($) | 12 Months Ended
--- | ---
Sep. 30, 2017 | Sep. 30, 2016 | Sep. 30, 2015
Accumulated Other Comprehensive Income Loss [Line Items] |  |  |
Amounts reclassified out of AOCI | $ 0 | $ 0 |
Maximum [Member] |  |  |
Accumulated Other Comprehensive Income Loss [Line Items] |  |  |
Amounts reclassified out of AOCI pre-tax basis |  |  | $ 300,000

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