Stock Compensation Plans (Details 2) - USD ($) $ / shares in Units, $ in Thousands		3 Months Ended	12 Months Ended
		Apr. 30, 2016	Jan. 31, 2016
Shares
Options exercised (in shares)
Options forfeited and expired (in shares)		(10,392)
Number of Shares
RSUs and PSUs granted (in shares)		1,607,790
Share-based Compensation Arrangement by Share-based Payment Award, Number of Shares Withheld Related to Share Settlement		467,349
RSUs forfeited (in shares)		(390,407)
Options
Shares
Outstanding at the beginning of the period (in shares)		3,715,999
Options exercised (in shares)		(360,275)
Options forfeited and expired (in shares)		(10,392)
Outstanding at the end of the period (in shares)		3,345,332	3,715,999
Vested and expected to vest at the end of the period (in shares)		3,345,141
Exercisable at the end of the period (in shares)		3,264,406
Weighted-Average Exercise Price Per Share
Balances at the beginning of the period (in dollars per share)		$ 4.72
Options exercised (in dollars per share)		4.62
Options forfeited (in dollars per share)		1.36
Balances at the end of the period (in dollars per share)		4.74	$ 4.72
Vested and expected to vest at the end of the period (in dollars per share)		4.74
Exercisable at the end of the period (in dollars per share)		$ 4.57
Weighted-Average Remaining Contractual Term
Balances at the end of the period		3 years 10 months 2 days	4 years 2 months 27 days
Vested and expected to vest at the end of the period		3 years 10 months 2 days
Vested and exercisable at the end of the period		3 years 8 months 27 days
Aggregate Intrinsic Value
Outstanding at the end of the period (in dollars)	[1]	$ 158,222	$ 154,696
Vested and expected to vest at the end of the period (in dollars)	[1]	158,214
Vested and exercisable at the end of the period (in dollars)	[1]	154,852
Tax benefits
Tax benefits that have been realized from exercised stock options		700
Unrecognized compensation cost
Total unrecognized compensation cost related to stock options		$ 3,900
Weighted-average period over which unrecognized compensation cost is expected to be recognized		1 year 9 months 18 days
Additional disclosures
Total intrinsic value of options exercised (in dollars)		$ 15,500
RSUs and PSUs
Number of Shares
Balances at the beginning of the period (in shares)		14,752,253
RSUs and PSUs granted (in shares)		1,607,790
RSUs vested (in shares)		(1,239,699)
RSUs forfeited (in shares)		(390,407)
Balances at the end of the period (in shares)		14,729,937	14,752,253
RSUs vested and expected to vest at the end of the period (in shares)		14,278,462
Unrecognized compensation cost
Weighted-average period over which unrecognized compensation cost is expected to be recognized		2 years 9 months 18 days
Total unrecognized compensation cost		$ 661,900
Additional disclosures
Weighted-average grant date fair value of awards granted (in dollars per share)		$ 45.87
PSUs
Unrecognized compensation cost
Weighted-average period over which unrecognized compensation cost is expected to be recognized		3 years 6 months
Total unrecognized compensation cost		$ 27,300
Additional disclosures
Weighted-average grant date fair value of awards granted (in dollars per share)		$ 46.66
Unregistered Restricted Shares
Number of Shares
RSUs and PSUs granted (in shares)			671,782
RSUs vested (in shares)		(74,828)
Balances at the end of the period (in shares)		596,954
Unrecognized compensation cost
Weighted-average period over which unrecognized compensation cost is expected to be recognized		2 years 8 months 12 days
Total unrecognized compensation cost		$ 34,600
Additional disclosures
Weighted-average grant date fair value of awards granted (in dollars per share)		$ 69.00
Minimum | PSUs
Tax benefits
Award vesting rights		0.00%
Maximum | PSUs
Tax benefits
Award vesting rights		200.00%

[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 April 30, 2016.