Summary of Significant Accounting Policies - Net Revenue Disaggregated by Sales Channel and Geographic Region (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended		39 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018	Mar. 31, 2018
Disaggregation Of Revenue [Line Items]
Total net revenue	$ 30,368	$ 14,588	$ 48,213	$ 28,904	$ 6,200
Direct
Disaggregation Of Revenue [Line Items]
Total net revenue	29,309	13,130	46,371	25,241
Wholesale
Disaggregation Of Revenue [Line Items]
Total net revenue	662	1,420	912	3,595
Managed SaaS
Disaggregation Of Revenue [Line Items]
Total net revenue	397	38	930	68
North America
Disaggregation Of Revenue [Line Items]
Total net revenue	30,335	14,588	48,134	28,904
North America | Direct
Disaggregation Of Revenue [Line Items]
Total net revenue	29,276	13,130	46,292	25,241
North America | Wholesale
Disaggregation Of Revenue [Line Items]
Total net revenue	662	1,420	912	3,595
North America | Managed SaaS
Disaggregation Of Revenue [Line Items]
Total net revenue	397	$ 38	930	$ 68
Other
Disaggregation Of Revenue [Line Items]
Total net revenue	33		79
Other | Direct
Disaggregation Of Revenue [Line Items]
Total net revenue	$ 33		$ 79