Income Taxes - Narrative (Details) - USD ($)	12 Months Ended
	Jan. 31, 2018	Jan. 31, 2017
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Income tax benefit related to stock based compensation	$ 1,300,000
Increase in valuation allowance	27,500,000	$ 26,900,000
Reduction in deferred tax asset before valuation allowance due to change in tax rate	61,000,000
Accrued penalties and interest related to unrecognized tax benefits	0	0
Domestic Tax Authority
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Operating loss carryforwards	490,600,000	264,700,000
State and Local Jurisdiction
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Operating loss carryforwards	295,600,000	$ 164,200,000
Foreign Tax Authority
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Operating loss carryforwards	2,300,000
Research Tax Credit Carryforward | Domestic Tax Authority
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Tax credit carryforward	6,200,000
Research Tax Credit Carryforward | State and Local Jurisdiction
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Tax credit carryforward	5,600,000
California Enterprise Zone Credit | State and Local Jurisdiction
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Tax credit carryforward	$ 1,000,000