Stock-Based Compensation Expense - Additional Information (Detail) (USD $) In Millions, except Share data, unless otherwise specified	3 Months Ended				6 Months Ended
	Jul. 31, 2011 Year Entity Investment		Jul. 31, 2010		Jul. 31, 2011 Year Entity Investment		Jul. 31, 2010
Compensation Related Costs Share Based Payments Disclosure [Line Items]
Total compensation costs related to non-vested options	$ 96.4				$ 96.4
Total compensation costs related to non-vested options, expected to be recognized over a weighted average period (in years)	2.1				2.1
Weighted average grant date fair value	$ 11.95	[1]	$ 8.51	[1]	$ 14.26	[1]	$ 9.15	[1]
Employee Stock Plan, 2008 Plan
Compensation Related Costs Share Based Payments Disclosure [Line Items]
Maximum vesting period of options and restricted stock granted (in years)	4				4
Shares of common stock reserved for issuance	16,000,000				16,000,000
Shares available for future issuance	9,800,000				9,800,000
Restricted stock shares available for future issuance	1,300,000				1,300,000
Employee Stock Plan, 2008 Plan | Restricted Stock and Restricted Stock Units
Compensation Related Costs Share Based Payments Disclosure [Line Items]
Shares of common stock reserved for issuance	2,500,000				2,500,000
Employee Stock Plan, 2008 Plan | Restricted Stock Units (RSUs)
Compensation Related Costs Share Based Payments Disclosure [Line Items]
Restricted stock granted					700,100
Compensation expense	8.3		2.2		13.6		3.9
Total compensation cost related to non-vested awards not yet recognized					37.5
Total compensation cost related to non-vested awards not yet recognized, weighted average period of recognition (in years)					1.4
Number of restricted stock granted but unreleased	1,900,000				1,900,000
Employee Stock Plan, 2008 Plan | Minimum
Compensation Related Costs Share Based Payments Disclosure [Line Items]
Option expiration term (in years)					7
Employee Stock Plan, 2008 Plan | Maximum
Compensation Related Costs Share Based Payments Disclosure [Line Items]
Option expiration term (in years)					10
Outside Directors Option Plan, 2010 Plan
Compensation Related Costs Share Based Payments Disclosure [Line Items]
Minimum vesting period of options and restricted stock granted (in years)	1				1
Maximum vesting period of options and restricted stock granted (in years)	4				4
Option expiration term (in years)					7
Shares of common stock reserved for issuance	3,000,000				3,000,000
Shares available for future issuance	2,600,000				2,600,000
Outside Directors Option Plan, 2010 Plan | Restricted Stock Awards
Compensation Related Costs Share Based Payments Disclosure [Line Items]
Restricted stock granted					16,000
Compensation expense	0.2		0.3		0.3		0.4
Total compensation cost related to non-vested awards not yet recognized					$ 0.5
Total compensation cost related to non-vested awards not yet recognized, weighted average period of recognition (in years)					0.9
Number of restricted stock granted but unreleased	16,000				16,000
ESP Plan
Compensation Related Costs Share Based Payments Disclosure [Line Items]
Percentage of compensation that eligible employees can use to purchase common stock, maximum					15.00%
Percentage of fair market value eligible employees can purchase common stock, minimum					85.00%
Shares available for future issuance	30,700,000				30,700,000
Description of increases of shares available for future issuance					automatically increases on the first trading day of each fiscal year by an amount equal to the lesser of 10.0 million shares or 2.0% of the total of (1) outstanding shares plus (2) any shares repurchased by Autodesk during the prior fiscal year
Shares issued under the ESP Plan					1,800,000		1,700,000
Shares issued under the ESP Plan, average price					$ 15.28		$ 14.65
Weighted average grant date fair value					$ 8.12		$ 6.90

[1] The weighted average grant date fair value of stock options granted is calculated, as of the stock option grant date, using the Black-Scholes-Merton option pricing model.