Options Outstanding and Exercisable (Detail) (USD $) In Millions, except Per Share data, unless otherwise specified	Jul. 31, 2011 Year Entity Investment		Jan. 31, 2011
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Options Exercisable - Number of Shares	18.6
Options Exercisable - Weighted average contractual life (in years)	2.5
Options Exercisable - Weighted average exercise price	$ 31.02
Options Exercisable - Aggregate intrinsic value	$ 125.0	[1]
Options Outstanding - Number of Shares	30.7		30.4
Options Outstanding - Weighted average contractual life (in years)	4.2
Options Outstanding - Weighted average exercise price	$ 31.36		$ 28.93
Options Outstanding - Aggregate intrinsic value	$ 191.1	[1]
Range 1
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Range of per-share exercise prices, Lower Limit	$ 0.61
Range of per-share exercise prices, Upper Limit	$ 17.37
Options Exercisable - Number of Shares	4.2
Options Exercisable - Weighted average exercise price	$ 12.80
Options Outstanding - Number of Shares	6.3
Options Outstanding - Weighted average exercise price	$ 13.51
Range 2
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Range of per-share exercise prices, Lower Limit	$ 17.39
Range of per-share exercise prices, Upper Limit	$ 29.49
Options Exercisable - Number of Shares	3.2
Options Exercisable - Weighted average exercise price	$ 26.53
Options Outstanding - Number of Shares	6.7
Options Outstanding - Weighted average exercise price	$ 27.67
Range 3
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Range of per-share exercise prices, Lower Limit	$ 29.50
Range of per-share exercise prices, Upper Limit	$ 37.16
Options Exercisable - Number of Shares	4.6
Options Exercisable - Weighted average exercise price	$ 32.95
Options Outstanding - Number of Shares	6.2
Options Outstanding - Weighted average exercise price	$ 32.65
Range 4
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Range of per-share exercise prices, Lower Limit	$ 37.26
Range of per-share exercise prices, Upper Limit	$ 41.62
Options Exercisable - Number of Shares	2.2
Options Exercisable - Weighted average exercise price	$ 38.65
Options Outstanding - Number of Shares	6.3
Options Outstanding - Weighted average exercise price	$ 40.49
Range 5
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Range of per-share exercise prices, Lower Limit	$ 41.70
Range of per-share exercise prices, Upper Limit	$ 49.80
Options Exercisable - Number of Shares	4.4
Options Exercisable - Weighted average exercise price	$ 45.67
Options Outstanding - Number of Shares	5.2
Options Outstanding - Weighted average exercise price	$ 45.43

[1] Represents the total pre-tax intrinsic value, based on Autodesk's closing stock price of $34.40 per share as of July 31, 2011, which would have been received by the option holders had all option holders exercised their options as of that date.