Income Taxes Narrative (Detail) - USD ($) $ in Thousands	3 Months Ended
	Dec. 31, 2016	Dec. 31, 2015
Income Tax Contingency [Line Items]
Income tax provision (benefit)	$ (2,800)	$ 3,370
Reductions in unrecognized tax benefits from expiration	700	700
Income tax benefit resulted from reinstatement of tax credit		$ 900
Minimum
Income Tax Contingency [Line Items]
Anticipated unrecognized tax benefit reduction during next twelve months	$ 700