Commitments and Contingencies Commitments and contingencies - additional Information (Details) (USD $) In Millions, unless otherwise specified	12 Months Ended
Jan. 31, 2012	Jan. 31, 2011	Jan. 31, 2010
Commitments and Contingencies - Additional Information [Abstract]
Total non cancellable purchase commitments	$ 53.5
Total non-cancellable purchase commitments, term	for periods through fiscal 2015.
Royalty expense recorded under cost of license and other revenue	$ 16.5	$ 12.8	$ 16.5

The amount of the fixed and determinable portion of an unrecorded unconditional purchase obligation as of the balance sheet date.

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 47

-Paragraph 7

-Subparagraph b

-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

Reference 2: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 440

-SubTopic 10

-Section 50

-Paragraph 4

-Subparagraph (b)

-URI http://asc.fasb.org/extlink&oid=6394976&loc=d3e25336-109308

Name:	us-gaap_UnrecordedUnconditionalPurchaseObligationBalanceSheetAmount
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant