Investments - Additional Information (Detail) (USD $)	9 Months Ended	12 Months Ended
	Oct. 31, 2014	Jan. 31, 2014
Investment Holdings [Line Items]
Unrealized losses on fixed rate investments, lower range value	$ 1,000
Unrealized losses on fixed rate investments, upper range value	44,000
Fair value of marketable security	980,952,000	539,382,000
Investments in privately-held companies	121,000,000	77,000,000
Investments in privately-held companies, estimated fair value	230,000,000
Restricted cash	114,935,000	0
Strategic Investments
Investment Holdings [Line Items]
Fair value of marketable security	11,200,000	15,500,000
Unrealized gain on marketable securities	$ 9,300,000	$ 13,300,000