Options Outstanding and Exercisable (Detail) (USD $) In Millions, except Per Share data, unless otherwise specified	Jan. 31, 2012 Year		Jan. 31, 2011
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Options Exercisable - Number of Shares	16.7
Options Exercisable - Weighted average contractual life (in years)	2.1
Options Exercisable - Weighted average exercise price	$ 30.98
Options Exercisable - Aggregate intrinsic value	$ 127.7
Options Outstanding - Number of Shares	28.4		30.4
Options Outstanding - Weighted average contractual life (in years)	4.0
Options Outstanding - Weighted average exercise price	$ 31.39		$ 28.93
Options Outstanding - Aggregate intrinsic value	$ 201.3	[1]
Range 1
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Range of per-share exercise prices, Lower Limit	$ 2.28
Range of per-share exercise prices, Upper Limit	$ 17.37
Options Exercisable - Number of Shares	3.8
Options Exercisable - Weighted average exercise price	$ 12.94
Options Outstanding - Number of Shares	5.8
Options Outstanding - Weighted average exercise price	$ 13.61
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	2.6
Options Exercisable - Weighted average exercise price	$ 25.81
Options Outstanding - Number of Shares	6.1
Options Outstanding - Weighted average exercise price	$ 27.64
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	4.4
Options Exercisable - Weighted average exercise price	$ 32.94
Options Outstanding - Number of Shares	6.0
Options Outstanding - Weighted average exercise price	$ 32.72
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	2.0
Options Exercisable - Weighted average exercise price	$ 38.40
Options Outstanding - Number of Shares	5.9
Options Outstanding - Weighted average exercise price	$ 40.46
Range 5
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Range of per-share exercise prices, Lower Limit	$ 42.01
Range of per-share exercise prices, Upper Limit	$ 49.80
Options Exercisable - Number of Shares	3.9
Options Exercisable - Weighted average exercise price	$ 45.69
Options Outstanding - Number of Shares	4.6
Options Outstanding - Weighted average exercise price	$ 45.42

[1] Represents the total intrinsic value, based on Autodesk’s closing stock price of $36.00 per share as of January 31, 2012, which would have been received by the option holders had all option holders exercised their options as of that date.