Stock-based Compensation Expense Intrinsic Value of Options Exercised and Weighted Average Grant Date Fair Value of Stock Options Granted (Details) (USD $) In Millions, except Per Share data, unless otherwise specified	3 Months Ended
	Apr. 30, 2014		Apr. 30, 2013
Disclosure of Compensation Related Costs, Share-based Payments [Abstract]
Pre-tax intrinsic value of options exercised	$ 22.8	[1]	$ 32.8	[1]
Weighted average grant date fair value per share of stock options granted (in dollars per share)	$ 0.00	[2]	$ 0.00	[2]

[1] The intrinsic value of options exercised is calculated as the difference between the exercise price of the option and the market value of the stock on the date of exercise.

[2] The weighted average grant date fair value per share of stock options granted is calculated, as of the stock option grant date, using the BSM option pricing model. For the three months ended April 30, 2014 and 2013, Autodesk did not grant stock options.