Supplemental financial statement information (Property and equipment) (Details) - USD ($) $ in Thousands	12 Months Ended
Jan. 31, 2020	Jan. 31, 2019	Jan. 31, 2018
Property, Plant and Equipment [Line Items]
Property and equipment, gross	$ 49,243	$ 17,301
Accumulated depreciation	(15,757)	(9,078)
Property and equipment, net	33,486	8,223
Depreciation expense	8,900	3,500	$ 2,800
Leasehold improvements
Property, Plant and Equipment [Line Items]
Property and equipment, gross	19,240	3,583
Furniture and fixtures
Property, Plant and Equipment [Line Items]
Property and equipment, gross	7,929	4,476
Computer equipment
Property, Plant and Equipment [Line Items]
Property and equipment, gross	$ 22,074	$ 9,242

Amount of accumulated depreciation, depletion and amortization for physical assets used in the normal conduct of business to produce goods and services.

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The amount of expense recognized in the current period that reflects the allocation of the cost of tangible assets over the assets' useful lives. Includes production and non-production related depreciation.

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Amount before accumulated depreciation, depletion and amortization of physical assets used in the normal conduct of business and not intended for resale. Examples include, but are not limited to, land, buildings, machinery and equipment, office equipment, and furniture and fixtures.

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Amount after accumulated depreciation, depletion and amortization of physical assets used in the normal conduct of business to produce goods and services and not intended for resale. Examples include, but are not limited to, land, buildings, machinery and equipment, office equipment, and furniture and fixtures.

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