Basis of Presentation and Significant Accounting Policies - Concentration of 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
Accounts Receivable | Customer Concentration Risk | Customer One
Concentration Risk [Line Items]
Concentration risk, percentage			38.20%		66.80%
Accounts Receivable | Customer Concentration Risk | Customer Two
Concentration Risk [Line Items]
Concentration risk, percentage			13.40%
Sales Revenue, Net | Customer Concentration Risk | Customer One
Concentration Risk [Line Items]
Concentration risk, percentage	17.00%		20.00%
Sales Revenue, Net | Customer Concentration Risk | Customer Two
Concentration Risk [Line Items]
Concentration risk, percentage	52.00%	45.00%	40.00%	49.00%
Sales Revenue, Net | Customer Concentration Risk | Customer Three
Concentration Risk [Line Items]
Concentration risk, percentage	2.00%		12.00%
Asia Pacific | Sales Revenue, Net | Geographic Concentration Risk
Concentration Risk [Line Items]
Concentration risk, percentage	17.70%	0.90%	20.60%	9.10%