Concentration of Credit Risk (Details)	3 Months Ended		6 Months Ended	12 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Dec. 31, 2018
Net accounts receivable | Customer concentration | Company A
Concentration Risk [Line Items]
Risk concentration			19.00%	10.00%
Total revenue | Customer concentration | Company A
Concentration Risk [Line Items]
Risk concentration	13.00%
Total revenue | Customer concentration | Company B
Concentration Risk [Line Items]
Risk concentration	11.00%
Total revenue | Customer concentration | Company C
Concentration Risk [Line Items]
Risk concentration			10.00%
Total revenue | Customer concentration | Company D
Concentration Risk [Line Items]
Risk concentration		13.00%
Total revenue | Customer concentration | Company E
Concentration Risk [Line Items]
Risk concentration		12.00%
Total revenue | Customer concentration | Company F
Concentration Risk [Line Items]
Risk concentration		11.00%
Financial institution A | Cash and cash equivalents | Concentration of credit risk
Concentration Risk [Line Items]
Risk concentration			55.00%	46.00%
Financial institution B | Cash and cash equivalents | Concentration of credit risk
Concentration Risk [Line Items]
Risk concentration			41.00%	43.00%