Concentration of Credit Risk (Details)	3 Months Ended	9 Months Ended	12 Months Ended
	Sep. 30, 2018	Sep. 30, 2019	Dec. 31, 2018
Net accounts receivable | Customer concentration | Company A
Concentration Risk [Line Items]
Risk concentration		14.00%	10.00%
Total revenue | Customer concentration | Company A
Concentration Risk [Line Items]
Risk concentration	20.00%
Total revenue | Customer concentration | Company B
Concentration Risk [Line Items]
Risk concentration	18.00%
Total revenue | Customer concentration | Company C
Concentration Risk [Line Items]
Risk concentration	17.00%
Financial institution A | Cash and cash equivalents | Concentration of credit risk
Concentration Risk [Line Items]
Risk concentration		71.00%	46.00%
Financial institution B | Cash and cash equivalents | Concentration of credit risk
Concentration Risk [Line Items]
Risk concentration		26.00%	43.00%