Segment, Geographical and Other Revenue Information - Concentration Risk (Details)	3 Months Ended		6 Months Ended		12 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018	Dec. 31, 2018
Customer Concentration Risk [Member] | Customer A [Member] | Sales [Member]
Concentration Risk [Line Items]
Concentration risk, percentage	35.00%	27.00%	38.00%	38.00%
Customer Concentration Risk [Member] | Customer B [Member] | Sales [Member]
Concentration Risk [Line Items]
Concentration risk, percentage	14.00%	18.00%	26.00%	21.00%
Customer Concentration Risk [Member] | Customer C [Member] | Sales [Member]
Concentration Risk [Line Items]
Concentration risk, percentage		34.00%		22.00%
Customer Concentration Risk [Member] | Customer D [Member] | Sales [Member]
Concentration Risk [Line Items]
Concentration risk, percentage	11.00%
Credit Concentration Risk [Member] | Customer A [Member] | Accounts Receivable [Member]
Concentration Risk [Line Items]
Concentration risk, percentage			39.00%		37.00%
Credit Concentration Risk [Member] | Customer B [Member] | Accounts Receivable [Member]
Concentration Risk [Line Items]
Concentration risk, percentage					17.00%
Credit Concentration Risk [Member] | Customer D [Member] | Accounts Receivable [Member]
Concentration Risk [Line Items]
Concentration risk, percentage			11.00%
Credit Concentration Risk [Member] | Customer E [Member] | Accounts Receivable [Member]
Concentration Risk [Line Items]
Concentration risk, percentage			15.00%
Credit Concentration Risk [Member] | Customer F [Member] | Accounts Receivable [Member]
Concentration Risk [Line Items]
Concentration risk, percentage					16.00%
Credit Concentration Risk [Member] | Customer G [Member] | Accounts Receivable [Member]
Concentration Risk [Line Items]
Concentration risk, percentage					11.00%