Employee Benefit Plans (Narrative) (Details) (USD $)	12 Months Ended
	Jan. 31, 2013	Jan. 31, 2012		Jan. 31, 2011
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	$ 13,616,000	$ 11,994,000	[1]	$ 10,353,000	[1]
Stock-based compensation expense, related income tax benefits	4,400,000	3,700,000		3,100,000
Cash received from equity-based incentives exercised	3,400,000	35,100,000		5,000,000
Tax deduction from the exercise of equity-based incentives	11,700,000	7,600,000		4,400,000
RSU compensation expense	12,600,000	10,700,000		8,000,000
Weighted-average estimated fair value	$ 52.80
Stock-based compensation expense for the vesting of MV Stock-settled SARS and MVOs	1,000,000	1,300,000		2,400,000
Equity instruments other than options, granted during period	305,097
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	9,300,000	7,900,000		7,100,000
Weighted-average estimated fair value		$ 48.53		$ 44.88
Unrecognized stock-based compensation expense	17,000,000
Unrecognized stock-based compensation expense, weighted average period of recognition (in years)	3 years
Remaining weighted average period (in years)	2 years
Equity instruments other than options, granted during period		272,949		277,527
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
Weighted-average estimated fair value	$ 10.77	$ 10.78		$ 7.97
Unrecognized stock-based compensation expense	200,000
Unrecognized stock-based compensation expense, weighted average period of recognition (in years)	2 years
Remaining weighted average period (in years)	1 year
Intrinsic value of MV Stock-settled SARs, MVO and stock option awards exercised	21,000,000	14,100,000		5,300,000
Total fair value of MV Stock-settled SARs and MVOs vested	1,200,000	1,500,000		4,500,000
Equity instruments other than options, granted during period	6,236	12,882		17,799
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	482,776
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)	$ 2,500,000	$ 2,500,000		$ 2,300,000
Number of common stock shares held by the Company's 401(k) Savings Plan	0	157,722
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

[1] See Note 2 - Restatement of Consolidated Financial Statements.