Summary of Convertible Senior Notes (Parenthetical) (Detail) (USD $) In Thousands, unless otherwise specified			12 Months Ended		12 Months Ended
Jan. 31, 2014	Jan. 31, 2013	Jan. 31, 2014 0.75% Convertible Senior Notes due January 15, 2015	Jan. 31, 2010 0.75% Convertible Senior Notes due January 15, 2015	Jan. 31, 2014 0.25% Convertible Senior Notes due April 1, 2018	Mar. 31, 2013 0.25% Convertible Senior Notes due April 1, 2018
Debt Conversion [Line Items]
Contractual interest rate			0.75%	0.75%	0.25%	0.25%
Convertible senior notes, maturity date			Jan. 15, 2015		Apr. 01, 2018
Temporary equity	$ 26,705	$ 53,612

Carrying amount, attributable to parent, of an entity's issued and outstanding stock which is not included within permanent equity. Temporary equity is a security with redemption features that are outside the control of the issuer, is not classified as an asset or liability in conformity with GAAP, and is not mandatorily redeemable. Includes any type of security that is redeemable at a fixed or determinable price or on a fixed or determinable date or dates, is redeemable at the option of the holder, or has conditions for redemption which are not solely within the control of the issuer. Includes stock with a put option held by an ESOP and stock redeemable by a holder only in the event of a change in control of the issuer.

No definition available.

Name:	us-gaap_TemporaryEquityCarryingAmountAttributableToParent
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant