Income Taxes - Additional Information (Detail) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Jun. 30, 2015	Jun. 30, 2014	Jun. 30, 2015	Jun. 30, 2014	Sep. 30, 2014
Income Tax Disclosure [Abstract]
Effective income tax rate	34.70%	32.20%	28.90%	34.40%
Unrecognized tax benefits, uncertain tax positions	$ 5.2		$ 5.2		$ 4.6
Unrecognized tax benefits, accrued interest	$ 0.7		$ 0.7		$ 0.5