Major Customers - Narrative (Details) - Customer Concentration Risk - customer	3 Months Ended		6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018
Revenues
Concentration Risk [Line Items]
Number of customers	3	2	3	2
Revenues | Customer No. 1
Concentration Risk [Line Items]
Concentration risk percentage	29.00%	25.00%	29.00%	21.00%
Revenues | Customer No. 2
Concentration Risk [Line Items]
Concentration risk percentage	22.00%	19.00%	22.00%	24.00%
Revenues | Customer No. 3
Concentration Risk [Line Items]
Concentration risk percentage	10.00%		10.00%
Accounts Receivable
Concentration Risk [Line Items]
Number of customers			2
Accounts Receivable | Customer No. 1
Concentration Risk [Line Items]
Concentration risk percentage			46.00%
Accounts Receivable | Customer No. 2
Concentration Risk [Line Items]
Concentration risk percentage			14.00%