Income Taxes - Additional Information (Detail) (USD $)	3 Months Ended		9 Months Ended
	Oct. 31, 2014	Oct. 31, 2013	Oct. 31, 2014	Oct. 31, 2013
Income Tax Disclosure [Abstract]
Provision (benefit) for income taxes	$ 17,075,000	$ 393,000	$ 37,336,000	$ (119,236,000)
Loss before benefit from income taxes	21,849,000	124,041,000	159,587,000	234,788,000
Effective tax rate			(23.00%)	51.00%
Federal statutory income tax rate			35.00%
Discrete tax benefit recorded from partial release of company's valuation allowance				135,500,000
Income tax benefit recognized from stock compensation expense			$ 125,700,000	$ 104,300,000