Income Taxes - Additional Information (Detail)	3 Months Ended		6 Months Ended
	Jul. 31, 2014	Jul. 31, 2013	Jul. 31, 2014	Jul. 31, 2013
Income Tax Contingency [Line Items]
Effective tax rates	42.60%	38.60%	42.50%	37.90%
Increase in effective tax rate	4.00%		4.60%