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Income Taxes - Additional Information (Detail) - USD ($) | 3 Months Ended
--- | ---
Dec. 31, 2017 | Dec. 31, 2016
Income Tax Disclosure [Line Items] |  |
Effective tax rate | (5.30%) | 41.30%
Provisional income tax benefit due to reduction in Federal corporate tax rate | $ 11,452,000 |
Effective income tax rate excluding impact of net deferred tax liability | 34.70% |
Unrecognized income tax benefits | $ 0 |
Federal |  |
Income Tax Disclosure [Abstract] |  |
Number of years for examination | 4 years |
Federal | Tax Year 2017 |  |
Income Tax Disclosure [Line Items] |  |
Corporate income tax rate | 35.00% |
Federal | Tax Year 2018 |  |
Income Tax Disclosure [Line Items] |  |
Corporate income tax rate | 21.00% |
New York |  |
Income Tax Disclosure [Abstract] |  |
Number of years for examination | 4 years |
Connecticut |  |
Income Tax Disclosure [Abstract] |  |
Number of years for examination | 4 years |
Pennsylvania |  |
Income Tax Disclosure [Abstract] |  |
Number of years for examination | 4 years |
New Jersey |  |
Income Tax Disclosure [Abstract] |  |
Number of years for examination | 5 years |

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