Debt - Components of Warrants (Detail) (USD $) In Thousands, except Share data, unless otherwise specified	3 Months Ended		9 Months Ended
	Oct. 31, 2014	Oct. 31, 2013	Oct. 31, 2014	Oct. 31, 2013
Class of Warrant or Right [Line Items]
Proceeds (in thousands)	$ 0	$ 0	$ 0	$ 84,800
Shares	44,252,692		44,252,692
0.75% Warrants
Class of Warrant or Right [Line Items]
Proceeds (in thousands)			59,300
Shares	26,943,812		26,943,812
Strike Price	29.88		29.88
Contractual interest rate	0.75%		0.75%
0.25% Warrants
Class of Warrant or Right [Line Items]
Proceeds (in thousands)			$ 84,800
Shares	17,308,880		17,308,880
Strike Price	90.40		90.40
Contractual interest rate	0.25%		0.25%