Stock-based Compensation Expense Assumption Used to Estimate the Fair Value of Stock-Based Awards (Details)	3 Months Ended
	Apr. 30, 2013	Apr. 30, 2012
Employee Stock Option [Member]
Share based Compensation Arrangement by Share based Payment Award, Fair Value Assumptions, Method Used [Line Items]
Share-based Compensation Arrangement by Share-based Payment Award, Fair Value Assumptions, Expected Dividend Rate (in %)		0.00%
Employee Stock Option [Member] | Minimum [Member]
Share based Compensation Arrangement by Share based Payment Award, Fair Value Assumptions, Method Used [Line Items]
Share-based Compensation Arrangement by Share-based Payment Award, Fair Value Assumptions, Expected Term (in years)		3 years 7 months 6 days
Share-based Compensation Arrangement by Share-based Payment Award, Fair Value Assumptions, Expected Volatility Rate (in %)		44.00%
Share-based Compensation Arrangement by Share-based Payment Award, Fair Value Assumptions, Risk Free Interest Rate (in %)		0.50%
Share Based Compensation Arrangement by Share Based Payment Award, Fair Value Assumptions Expected Forfeitures (in %)		0.00%
Employee Stock Option [Member] | Maximum [Member]
Share based Compensation Arrangement by Share based Payment Award, Fair Value Assumptions, Method Used [Line Items]
Share-based Compensation Arrangement by Share-based Payment Award, Fair Value Assumptions, Expected Term (in years)		4 years 7 months 6 days
Share-based Compensation Arrangement by Share-based Payment Award, Fair Value Assumptions, Expected Volatility Rate (in %)		45.00%
Share-based Compensation Arrangement by Share-based Payment Award, Fair Value Assumptions, Risk Free Interest Rate (in %)		0.80%
Share Based Compensation Arrangement by Share Based Payment Award, Fair Value Assumptions Expected Forfeitures (in %)		7.80%
Employee Qualified Stock Purchase Plan 1998 ESP Plan [Member]
Share based Compensation Arrangement by Share based Payment Award, Fair Value Assumptions, Method Used [Line Items]
Share-based Compensation Arrangement by Share-based Payment Award, Fair Value Assumptions, Expected Dividend Rate (in %)	0.00%	0.00%
Employee Qualified Stock Purchase Plan 1998 ESP Plan [Member] | Minimum [Member]
Share based Compensation Arrangement by Share based Payment Award, Fair Value Assumptions, Method Used [Line Items]
Share-based Compensation Arrangement by Share-based Payment Award, Fair Value Assumptions, Expected Term (in years)	6 months	6 months
Share-based Compensation Arrangement by Share-based Payment Award, Fair Value Assumptions, Expected Volatility Rate (in %)	27.00%	41.00%
Share-based Compensation Arrangement by Share-based Payment Award, Fair Value Assumptions, Risk Free Interest Rate (in %)	0.10%	0.10%
Share Based Compensation Arrangement by Share Based Payment Award, Fair Value Assumptions Expected Forfeitures (in %)	0.00%	0.00%
Employee Qualified Stock Purchase Plan 1998 ESP Plan [Member] | Maximum [Member]
Share based Compensation Arrangement by Share based Payment Award, Fair Value Assumptions, Method Used [Line Items]
Share-based Compensation Arrangement by Share-based Payment Award, Fair Value Assumptions, Expected Term (in years)	2 years	2 years
Share-based Compensation Arrangement by Share-based Payment Award, Fair Value Assumptions, Expected Volatility Rate (in %)	36.00%	43.00%
Share-based Compensation Arrangement by Share-based Payment Award, Fair Value Assumptions, Risk Free Interest Rate (in %)	0.30%	0.30%
Share Based Compensation Arrangement by Share Based Payment Award, Fair Value Assumptions Expected Forfeitures (in %)	7.70%	7.80%
Performance Shares [Member]
Share based Compensation Arrangement by Share based Payment Award, Fair Value Assumptions, Method Used [Line Items]
Share-based Compensation Arrangement by Share-based Payment Award, Fair Value Assumptions, Expected Volatility Rate (in %)	34.00%
Share-based Compensation Arrangement by Share-based Payment Award, Fair Value Assumptions, Expected Dividend Rate (in %)	0.00%
Share-based Compensation Arrangement by Share-based Payment Award, Fair Value Assumptions, Risk Free Interest Rate (in %)	0.10%