Income Taxes - Additional Information (Detail)	3 Months Ended
	Dec. 31, 2016	Dec. 31, 2015
Income Tax Examination [Line Items]
Effective tax rates	35.70%	38.10%
Federal statutory rate	35.00%
Domestic Tax Authority [Member] | Earliest Tax Year [Member]
Income Tax Examination [Line Items]
Open tax year	2013
Domestic Tax Authority [Member] | Latest Tax Year [Member]
Income Tax Examination [Line Items]
Open tax year	2013