Income Taxes - Activity Related to Unrecognized Tax Benefits (Details) - USD ($) $ in Thousands	12 Months Ended
Jan. 31, 2016	Jan. 31, 2015	Jan. 31, 2014
Income Tax Disclosure [Abstract]
Gross unrecognized tax benefits—beginning balance	$ 13,874	$ 4,676	$ 479
Decreases related to tax positions taken during prior years	(3,969)	0	(10)
Increases related to tax positions taken during prior years	35	0	0
Increases related to tax positions taken during current year	5,530	9,198	4,207
Gross unrecognized tax benefits—ending balance	$ 15,470	$ 13,874	$ 4,676

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- Definition

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
-Topic 740
-SubTopic 10
-Section 50
-Paragraph 15A
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=6907707&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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