Other Intangible Assets and Related Accumulated Amortization (Detail) (USD $) In Millions, unless otherwise specified	Apr. 30, 2012		Jan. 31, 2012
Finite-Lived Intangible Assets [Line Items]
Purchased technologies at cost	$ 400.5	[1]	$ 400.5	[1]
Customer relationships and trade names, at cost	215.0	[2]	215.3	[2]
Finite-Lived Intangible Assets, Gross, Total	615.5		615.8
Less: Accumulated amortization	(484.3)	[1]	(467.0)	[1]
Other intangible assets, net	$ 131.2		$ 148.8

[1] As of April 30, 2012, the purchased technologies balances are presented gross. Previously, Autodesk reported the cost and amortization balance for purchased technologies net of fully amortized intangible assets. For comparability, the presentation of the purchased technologies cost and amortization balances at January 31, 2012 were adjusted to align to current year presentation.

[2] Included in “Other assets” in the accompanying Condensed Consolidated Balance Sheets. Customer relationships and trade names include the effects of foreign currency translation.