Employee Stock and Savings Plans Summary (Details) (USD $) In Thousands, except Per Share data, unless otherwise specified	12 Months Ended
	Jan. 31, 2015	Jan. 31, 2014	Jan. 31, 2013
Restricted Stock Units (RSUs)
Share-based Compensation Arrangement by Share-based Payment Award
Equity instruments other than options, nonvested, number	4,246	4,083
Equity instruments other than options, nonvested, weighted average grant date fair value	$ 19.63	$ 17.07
Equity instruments other than options, grants in period	1,823
Weighted average grant date fair value	$ 21.52	$ 22.42	$ 16.74
Equity instruments other than options, vested in period	(1,548)
Equity instruments other than options, vested in period, weighted average grant date fair value	$ 14.79
Equity instruments other than options, forfeited in period	(112)
Equity instruments other than options, forfeitures, weighted average grant date fair value	$ 17.39
Equity instruments other than options, outstanding, weighted average remaining contractual terms	1 year 7 months 10 days
Equity instruments other than options, aggregate intrinsic value, nonvested	$ 97,699
Equity instruments other than options, vested in period, fair value	22,874	17,736	11,698
Equity Option
Share-based Compensation Arrangement by Share-based Payment Award
Options, outstanding, number	3,152	3,587
Options, outstanding, weighted average exercise price	$ 9.73	$ 9.87
Options, grants in period, gross	0
Options, grants in period, weighted average exercise price	$ 0.00
Options, exercises in period	(426)
Options, exercises in period, weighted average exercise price	$ 10.89
Options, forfeitures in period	0
Options, forfeitures in period, weighted average exercise price	$ 0.00
Options, expirations in period	(9)
Options, expirations in period, weighted average exercise price	$ 10.00
Options, outstanding, weighted average remaining contractual term	4 years 8 months 1 day
Options, outstanding, intrinsic value	41,849
Options, exercisable, number	2,844
Options, exercisable, weighted average exercise price	$ 9.14
Options, exercisable, weighted average remaining contractual term	4 years 4 months 17 days
Options, exercisable, intrinsic value	39,454
Options, vested and expected to vest, outstanding, number	3,152
Options, vested and expected to vest, outstanding, weighted average exercise price	$ 9.73
Options, vested and expected to vest, outstanding, weighted average remaining contractual term	4 years 8 months 1 day
Options, vested and expected to vest, outstanding, aggregate intrinsic value	41,849
Options, exercises in period, intrinsic value	4,601	26,769	21,647
Proceeds from stock options exercised	4,636	38,830	24,262
Expiry period from date of grant	10 years 0 months 0 days
Omnibus Incentive Plan
Share-based Compensation Arrangement by Share-based Payment Award
Requisite service period	4 years 0 months 0 days
Number of shares available for grant	5,538
Omnibus Incentive Plan | Performance Shares
Share-based Compensation Arrangement by Share-based Payment Award
Requisite service period	3 years 0 months 0 days
Employee Stock Purchase Plans
Share-based Compensation Arrangement by Share-based Payment Award
Stock issued during period, shares, employee stock purchase plans	1,389	1,554	1,884
Proceeds from issuance of shares under incentive and share-based compensation plans, excluding stock options	$ 25,642	$ 23,895	$ 22,645
Employee stock purchase plan weighted average purchase price	$ 18.47	$ 15.38	$ 12.02
Employee stock purchase plan maximum number of shares per buy date that may be purchased by eligible participants	6
Discounted price from market price offering	85.00%
Available for future purchase employee stock purchase plan shares	5,158