Segment, Geographical and Other Revenue Information - Concentration Risk (Details)	3 Months Ended		6 Months Ended		12 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017	Dec. 31, 2016
Customer Concentration Risk [Member] | Customer A [Member] | Sales [Member]
Concentration Risk [Line Items]
Concentration risk, percentage	27.00%	45.00%	38.00%	42.00%
Customer Concentration Risk [Member] | Customer B [Member] | Sales [Member]
Concentration Risk [Line Items]
Concentration risk, percentage	34.00%	21.00%	22.00%	12.00%
Customer Concentration Risk [Member] | Customer C [Member] | Sales [Member]
Concentration Risk [Line Items]
Concentration risk, percentage	18.00%		21.00%
Credit Concentration Risk [Member] | Customer A [Member] | Accounts Receivable [Member]
Concentration Risk [Line Items]
Concentration risk, percentage			46.00%		31.00%
Credit Concentration Risk [Member] | Customer B [Member] | Accounts Receivable [Member]
Concentration Risk [Line Items]
Concentration risk, percentage			27.00%		16.00%
Credit Concentration Risk [Member] | Customer D [Member] | Accounts Receivable [Member]
Concentration Risk [Line Items]
Concentration risk, percentage			11.00%		15.00%
Credit Concentration Risk [Member] | Customer E [Member] | Accounts Receivable [Member]
Concentration Risk [Line Items]
Concentration risk, percentage					14.00%