Employee Stock and Savings Plans Summary Stock Option Activity (Details) (USD $) In Thousands, except Per Share data, unless otherwise specified	12 Months Ended
Jan. 31, 2013	Jan. 31, 2012
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding [Roll Forward]
Stock options outstanding	6,717	9,187
Stock options granted	539
Stock options exercised	(2,835)
Stock options forfeited	(34)
Stock options expired	(140)
Stock options outstanding exercisable	5,504
Stock options vested and expected to vest	6,717
Share-based Compensation Arrangement by Share-based Payment Award, Options, Additional Disclosures [Abstract]
Weighted average exercise price of stock options outstanding	$ 11.08	$ 10.00
Weighted average exercise price of stock options granted	$ 16.97
Weighted average exercise price of stock options exercised	$ 8.56
Weighted average exercise price of stock options forfeited	$ 6.61
Weighted average exercise price of stock options expired	$ 14.71
Weighted average exercise price of stock options exercisable	$ 10.61
Weighted average exercise price of stock options vested and expected to vest	$ 11.08
Share Based Compensation Arrangement By Share Based Payment Award Options Weighted Average Remaining Contractual Term [Abstract]
Weighted average remaining contractual term of stock options outstanding	5 years 2 months 26 days
Weighted average remaining contractual term of stock options exercisable	4 years 5 months 22 days
Weighted average remaining contractual term of stock options vested and expected to vest	5 years 2 months 26 days
Share Based Compensation Arrangement By Share Based Payment Award Options Aggregate Intrinsic Value [Abstract]
Aggregate intrinsic value of stock options outstanding	$ 40,677
Aggregate intrinsic value of options exercisable	35,925
Aggregate intrinsic value of stock options vested and expected to vest	$ 40,677

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