Stock-based Compensation Expense Assumption Used to Estimate the Fair Value of Stock-Based Awards (Details)	3 Months Ended		6 Months Ended
	Jul. 31, 2012	Jul. 31, 2011	Jul. 31, 2012	Jul. 31, 2011
Stock Options 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 Volatility Rate	41.00%	40.00%	41.00%	40.00%
Expected Term, Share Based Compensation Arrangement by Share Based Payment Award, Fair Value Assumptions	3.6	3.6	3.6	2.6
Share-based Compensation Arrangement by Share-based Payment Award, Fair Value Assumptions, Risk Free Interest Rate	0.50%	0.90%	0.50%	0.90%
Share Based Compensation Arrangement by Share Based Payment Award, Fair Value Assumptions Expected Forfeitures	7.70%	7.80%	7.70%	7.80%
Stock Options 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 Volatility Rate	43.00%	42.00%	45.00%	43.00%
Expected Term, Share Based Compensation Arrangement by Share Based Payment Award, Fair Value Assumptions	4.6	4.6	4.6	4.6
Share-based Compensation Arrangement by Share-based Payment Award, Fair Value Assumptions, Risk Free Interest Rate	0.60%	1.40%	0.80%	1.90%
Share Based Compensation Arrangement by Share Based Payment Award, Fair Value Assumptions Expected Forfeitures	0.00%	0.00%	7.80%	10.50%
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	0.00%	0.00%	0.00%	0.00%
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	0.00%	0.00%	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 Volatility Rate	41.00%	34.00%	41.00%	34.00%
Expected Term, Share Based Compensation Arrangement by Share Based Payment Award, Fair Value Assumptions	0.5	0.5	0.5	0.5
Share-based Compensation Arrangement by Share-based Payment Award, Fair Value Assumptions, Risk Free Interest Rate	0.10%	0.20%	0.10%	0.20%
Share Based Compensation Arrangement by Share Based Payment Award, Fair Value Assumptions Expected Forfeitures	0.00%	7.80%	7.70%	7.80%
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 Volatility Rate	43.00%	37.00%	43.00%	37.00%
Expected Term, Share Based Compensation Arrangement by Share Based Payment Award, Fair Value Assumptions	2.0	2.0	2.0	2.0
Share-based Compensation Arrangement by Share-based Payment Award, Fair Value Assumptions, Risk Free Interest Rate	0.30%	0.80%	0.30%	0.80%
Share Based Compensation Arrangement by Share Based Payment Award, Fair Value Assumptions Expected Forfeitures	0.00%	0.00%	7.80%	10.50%