Income Taxes - Additional Information (Detail) - USD ($) $ in Millions	3 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Sep. 30, 2015
Income Tax Disclosure [Abstract]
Effective income tax rate	19.10%	21.40%
Unrecognized tax benefits, uncertain tax positions	$ 5.4		$ 4.6
Unrecognized tax benefits, accrued interest	$ 0.3		$ 0.2