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				9 Months Ended
	Oct. 31, 2014		Oct. 31, 2013		Oct. 31, 2014		Oct. 31, 2013
Disclosure of Compensation Related Costs, Share-based Payments [Abstract]
Pre-tax intrinsic value of options exercised	$ 10.3	[1]	$ 37.4	[1]	$ 54.5	[1]	$ 80.2	[1]
Weighted average grant date fair value per share of stock options granted (in dollars per share)	$ 0.00	[2]	$ 0.00	[2]	$ 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 Black-Scholes Merton ("BSM") option pricing model. For the three and nine months ended October 31, 2014 and 2013, Autodesk did not grant stock options.