Debt - Summary of Convertible Senior Notes (Detail) (USD $) In Thousands, unless otherwise specified	Oct. 31, 2014	Jan. 31, 2014	Oct. 31, 2014 0.75% Convertible Senior Notes due January 15, 2015	Jan. 31, 2014 0.75% Convertible Senior Notes due January 15, 2015	Jan. 31, 2011 0.75% Convertible Senior Notes due January 15, 2015	Oct. 31, 2014 0.25% Convertible Senior Notes due April 1, 2018	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]
Par Value			$ 181,637			$ 1,150,000
Equity Component Recorded at Issuance			125,530			122,421
Convertible 0.75% senior notes, net	179,755	542,159	179,755	542,159
Convertible 0.25% senior notes, net	1,064,683	1,046,930				1,064,683	1,046,930
Contractual interest rate			0.75%		0.75%	0.25%		0.25%
Temporary equity	$ 1,882	$ 26,705	$ 1,900