Income Taxes - Reconciliation of Unrecognized Tax Benefits (Details) - USD ($) $ in Thousands	12 Months Ended
	Jan. 31, 2019	Jan. 31, 2018	Jan. 31, 2017
Reconciliation of Unrecognized Tax Benefits, Excluding Amounts Pertaining to Examined Tax Returns [Roll Forward]
Balance, beginning of the year	$ 683	$ 0	$ 0
Increases to tax positions taken during the current year	808	360	0
Increases to tax positions taken in prior years	0	323	0
Decreases to tax positions taken in prior years	(75)	0	0
Balance, end of year	$ 1,416	$ 683	$ 0