Income Taxes - Additional Information (Detail) $ in Millions	3 Months Ended	9 Months Ended
	Oct. 31, 2016 USD ($)	Oct. 31, 2016 USD ($)
Income Tax Disclosure [Abstract]
Decrease in income before income tax	$ 2.2	$ 2.8
Unrecognized tax benefits	$ 35.9	$ 35.9