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New Accounting Standards - Additional Information (Detail) - USD ($)
$ in Thousands
3 Months Ended 6 Months Ended
Mar. 31, 2018
Mar. 31, 2017
Dec. 31, 2016
Mar. 31, 2018
Mar. 31, 2017
New Accounting Pronouncements or Change in Accounting Principle [Line Items]          
Income tax expense (benefits) $ 1,424 $ 2,205   $ (616) $ 4,185
ASU 2016-09 [Member] | New Accounting Pronouncement Early Adoption Effect [Member]          
New Accounting Pronouncements or Change in Accounting Principle [Line Items]          
Income tax expense (benefits)     $ (200)