Income Taxes - Summary of Components of Deferred Income Tax Assets and Liabilities (Details) - USD ($) $ in Thousands	Jan. 31, 2018	Jan. 31, 2017
Deferred tax assets:
Net operating losses	$ 82,375	$ 93,497
Depreciation and amortization	1,877	2,527
Accruals and reserves	12,295	14,565
Stock-based compensation	11,480	3,715
Tax credits	8,202	4,592
Other	3	5
Gross deferred tax assets	116,232	118,901
Valuation allowance	(116,195)	(118,827)
Net deferred tax assets after valuation allowance	37	74
Total net deferred tax assets	$ 37	$ 74