Income Taxes Summary of the activity related to the gross unrecognized tax benefits (excluding interest and penalties) (Details) (USD $) In Thousands, unless otherwise specified	12 Months Ended
Jan. 31, 2012	Jan. 31, 2011	Jan. 31, 2010
Reconciliation of Unrecognized Tax Benefits, Excluding Amounts Pertaining to Examined Tax Returns [Roll Forward]
Gross unrecognized tax benefits at beginning of year	$ 3,112	$ 2,656	$ 2,269
Increases in tax positions related to the current year	699	601	463
Decreases as a result of a lapse in applicable statute of limitations	(244)	(145)	(76)
Gross unrecognized tax benefits at end of year	$ 3,567	$ 3,112	$ 2,656

The gross amount of unrecognized tax benefits pertaining to uncertain tax positions taken in tax returns as of the balance sheet date.

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

-Publisher FASB

-Name FASB Interpretation (FIN)

-Number 48

-Paragraph 21

-Subparagraph a

-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009.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

-Glossary Unrecognized Tax Benefit

-URI http://asc.fasb.org/extlink&oid=6527854

Reference 3: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 740

-SubTopic 10

-Section 50

-Paragraph 15A

-Subparagraph (a)

-URI http://asc.fasb.org/extlink&oid=6907707&loc=SL6600010-109319

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Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant