Revenue Recognition - Remaining performance obligations (Details) $ in Thousands	Oct. 31, 2019 USD ($)
Revenue from Contract with Customer [Abstract]
Revenue, remaining performance obligation, amount	$ 73,456
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2019-11-01
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Revenue, remaining performance obligation, percentage	70.00%
Revenue, remaining performance obligation, expected timing of satisfaction, period	1 year 9 months