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, 2015	Jan. 31, 2014	Jan. 31, 2013
Reconciliation of Unrecognized Tax Benefits, Excluding Amounts Pertaining to Examined Tax Returns [Roll Forward]
Gross unrecognized tax benefits at beginning of year	$ 4,660us-gaap_UnrecognizedTaxBenefits	$ 4,213us-gaap_UnrecognizedTaxBenefits	$ 3,567us-gaap_UnrecognizedTaxBenefits
Increases in tax positions related to the current year	909	795	993
Decreases as a result of a lapse in applicable statute of limitations	(393)	(348)	(347)
Unrecognized Tax Benefits, Decrease Resulting from Settlements with Taxing Authorities	(2,869)	0	0
Gross unrecognized tax benefits at end of year	$ 2,307us-gaap_UnrecognizedTaxBenefits	$ 4,660us-gaap_UnrecognizedTaxBenefits	$ 4,213us-gaap_UnrecognizedTaxBenefits

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Amount of unrecognized tax benefits pertaining to uncertain tax positions taken in tax returns.

+ References

Reference 1: 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

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-Publisher FASB

-Name Accounting Standards Codification

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Amount of decrease in unrecognized tax benefits resulting from settlements with taxing authorities.

+ References

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 740

-SubTopic 10

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

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Amount of increase in unrecognized tax benefits resulting from tax positions that have been or will be taken in current period tax return.

+ References

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

-Publisher FASB

-Name Accounting Standards Codification

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Amount of decrease in unrecognized tax benefits resulting from lapses of applicable statutes of limitations.

+ References

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 740

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