Income Taxes - Activity Related to Unrecognized Tax Benefits (Details) - USD ($) $ in Thousands	12 Months Ended
Jan. 31, 2017	Jan. 31, 2016	Jan. 31, 2015
Reconciliation of Unrecognized Tax Benefits
Gross unrecognized tax benefits—beginning balance	$ 15,470	$ 13,874	$ 4,676
Decreases related to tax positions taken during prior years	(11,286)	(3,969)	0
Increases related to tax positions taken during prior years	0	35	0
Increases related to tax positions taken during current year	2,191	5,530	9,198
Gross unrecognized tax benefits—ending balance	$ 6,375	$ 15,470	$ 13,874

A roll forward is a reconciliation of a concept from the beginning of a period to the end of a period.

No definition available.

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- Definition

Amount of unrecognized tax benefits.

+ References

Reference 1: 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=65882285&loc=SL6600010-109319

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

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- Definition

Amount of decrease in unrecognized tax benefits resulting from tax positions taken in prior period tax returns.

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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.

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Amount of increase in unrecognized tax benefits resulting from tax positions taken in prior period tax returns.

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