Stock Compensation Plans (Details 2) (USD $)	6 Months Ended		12 Months Ended
	Jul. 31, 2013		Jan. 31, 2013
Shares
Options forfeited and expired (in shares)	(226,285)
Number of Shares
RSUs granted (in shares)	1,055,713
Shares withheld related to net share settlement of RSUs	11,618
RSUs forfeited and expired (in shares)	(114,713)
Options
Shares
Outstanding at the beginning of the period (in shares)	18,917,547
Options exercised (in shares)	(3,907,868)
Options forfeited and expired (in shares)	(226,285)
Outstanding at the end of the period (in shares)	14,783,394		18,917,547
Vested and expected to vest at the end of the period (in shares)	14,411,462
Exercisable at the end of the period (in shares)	7,344,751
Weighted-Average Exercise Price Per Share
Balances at the beginning of the period (in dollars per share)	$ 4.26
Options exercised (in dollars per share)	$ 3.20
Options forfeited (in dollars per share)	$ 6.46
Balances at the end of the period (in dollars per share)	$ 4.50		$ 4.26
Vested and expected to vest at the end of the period (in dollars per share)	$ 4.44
Exercisable at the end of the period (in dollars per share)	$ 2.10
Weighted-Average Remaining Contractual Term
Balances at the end of the period	7 years 2 months 5 days
Vested and expected to vest at the end of the period	7 years 1 month 28 days
Vested and exercisable at the end of the period	6 years 1 month 24 days
Aggregate Intrinsic Value
Outstanding at the end of the period (in dollars)	$ 672,760,000	[1]		[1]
Vested and expected to vest at the end of the period (in dollars)	656,716,000	[1]
Vested and exercisable at the end of the period (in dollars)	351,876,000	[1]
Tax benefits
Tax benefits that have been realized from exercised stock options	300,000
Unrecognized compensation cost
Total unrecognized compensation cost related to stock options	24,700,000
Weighted-average period over which unrecognized compensation cost is expected to be recognized	2 years 1 month 17 days
Additional disclosures
Total intrinsic value of options exercised (in dollars)	149,200,000
RSUs
Number of Shares
Balances at the beginning of the period (in shares)	2,904,707
RSUs granted (in shares)	1,055,713
RSUs vested (in shares)	(37,151)
RSUs forfeited and expired (in shares)	(114,713)
Balances at the end of the period (in shares)	3,808,556
RSU's vested and expected to vest at the end of the period (in shares)	3,618,128
Unrecognized compensation cost
Weighted-average period over which unrecognized compensation cost is expected to be recognized	3 years 5 months 5 days
Total unrecognized compensation cost	$ 99,400,000
Additional disclosures
Weighted-average grant date fair value of RSUs granted (in dollars per share)	$ 41.41

[1] The intrinsic value is calculated as the difference between the exercise price of the underlying stock option award and the closing market price of our common stock as of July 31, 2013.