Summary of Significant Accounting Policies - Net Revenue Disaggregated by Sales Channel and Geographic Region (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended		39 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018	Mar. 31, 2018
Disaggregation Of Revenue [Line Items]
Total net revenue	$ 40,603	$ 24,672	$ 88,817	$ 53,576	$ 6,200
Direct
Disaggregation Of Revenue [Line Items]
Total net revenue	40,026	24,420	86,398	49,662
Wholesale
Disaggregation Of Revenue [Line Items]
Total net revenue	259	136	1,171	3,730
Managed SaaS
Disaggregation Of Revenue [Line Items]
Total net revenue	318	116	1,248	184
North America
Disaggregation Of Revenue [Line Items]
Total net revenue	40,584	24,595	88,731	53,350
North America | Direct
Disaggregation Of Revenue [Line Items]
Total net revenue	40,007	24,343	86,312	49,498
North America | Wholesale
Disaggregation Of Revenue [Line Items]
Total net revenue	259	136	1,171	3,668
North America | Managed SaaS
Disaggregation Of Revenue [Line Items]
Total net revenue	318	116	1,248	184
Other
Disaggregation Of Revenue [Line Items]
Total net revenue	19	77	86	226
Other | Direct
Disaggregation Of Revenue [Line Items]
Total net revenue	$ 19	$ 77	$ 86	164
Other | Wholesale
Disaggregation Of Revenue [Line Items]
Total net revenue				$ 62