For an entity that discloses a concentration risk in relation to quantitative amount, which serves as the "benchmark" (or denominator) in the equation, this concept represents the concentration percentage derived from the division.

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 275
-SubTopic 10
-Section 50
-Paragraph 18
-URI http://asc.fasb.org/extlink&oid=99393423&loc=d3e6351-108592

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 825
-SubTopic 10
-Section 50
-Paragraph 20
-URI http://asc.fasb.org/extlink&oid=118260190&loc=d3e13531-108611

Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 825
-SubTopic 10
-Section 50
-Paragraph 21
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=118260190&loc=d3e13537-108611

Reference 4: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 275
-SubTopic 10
-Section 50
-Paragraph 20
-URI http://asc.fasb.org/extlink&oid=99393423&loc=d3e6404-108592

Name:	us-gaap_ConcentrationRiskPercentage1
Namespace Prefix:	us-gaap_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

Summary of significant accounting policies - Schedule of Concentrations of Risk (Details) - Customer Concentration Risk	3 Months Ended	12 Months Ended
	Mar. 31, 2019	Mar. 31, 2020	Mar. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Revenue \| Walmart
Product Information [Line Items]
Concentration risk percentage	36.00%	31.00%		30.00%	29.00%
Revenue \| Target
Product Information [Line Items]
Concentration risk percentage	17.00%	22.00%		21.00%	25.00%
Accounts Receivable \| Walmart
Product Information [Line Items]
Concentration risk percentage		22.00%	19.00%	27.00%
Accounts Receivable \| Target
Product Information [Line Items]
Concentration risk percentage		20.00%	27.00%	20.00%