Employee Benefit Plans (Narrative) (Details) (USD $)	12 Months Ended
	Jan. 31, 2014	Jan. 31, 2013	Jan. 31, 2012
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of shares authorized for grant	4,000,000.0
Number of shares available for grant	3,000,000
Contractual term (in years)	10 years
Stock-based compensation expense	$ 8,858,000	$ 13,616,000	$ 11,994,000
Stock-based compensation expense, related income tax benefits	2,900,000	4,400,000	3,700,000
Cash received from equity-based incentives exercised	1,100,000	3,400,000	35,100,000
Tax deduction from the exercise of equity-based incentives	5,500,000	11,700,000	7,600,000
RSU compensation expense	8,700,000	12,600,000	10,700,000
Stock-based compensation expense for the vesting of MV Stock-settled SARS and MVOs	200,000	1,000,000	1,300,000
Restricted Stock Units (RSUs)
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Total fair value of equity instruments other than options which vested	12,900,000	9,300,000	7,900,000
Equity instruments other than options, granted during period		305,097	272,949
Weighted-average estimated fair value		$ 52.80	$ 48.53
Unrecognized stock-based compensation expense	6,200,000
Unrecognized stock-based compensation expense, weighted average period of recognition (in years)	2 years
Remaining weighted average period (in years)	2 years
Mv Stock Settled Sars Mvos And Stock Options
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Contractual term (in years)	10 years
Equity instruments other than options, granted during period		6,236	12,882
Weighted-average estimated fair value		$ 10.77	$ 10.78
Remaining weighted average period (in years)	1 year
Intrinsic value of MV Stock-settled SARs, MVO and stock option awards exercised	3,300,000	21,000,000	14,100,000
Total fair value of MV Stock-settled SARs and MVOs vested	1,000,000	1,200,000	1,500,000
Employee Stock Purchase Plan
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Common stock shares authorized under ESPP	1,000,000
Purchase price as a percentage of the market value	85.00%
Maximum annual fair market value per employee	25,000
Common stock shares issued to ESPP	483,538
ESPP, holding period for shares purchased	1 year
Retirement Savings Plan
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Percentage of employer's matching contribution	50.00%
Maximum percentage of participant's deferrals matched by Company	6.00%
401(k) Savings Plan vesting period (years)	four
Company's contribution to 401(k)	$ 700,000	$ 2,500,000
Minimum
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Awards vesting period, (in years)	1 year
Minimum | Restricted Stock Units (RSUs)
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Awards vesting period, (in years)	1 year
Minimum | Mv Stock Settled Sars Mvos And Stock Options
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Awards vesting period, (in years)	1 year
Maximum
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Awards vesting period, (in years)	4 years
Maximum | Restricted Stock Units (RSUs)
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Awards vesting period, (in years)	4 years
Maximum | Mv Stock Settled Sars Mvos And Stock Options
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Awards vesting period, (in years)	4 years