Concentration of Credit Risk (Details) - customer	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Concentration Risk [Line Items]
Percentage of U.S. demand supplied by company	1.00%
Customer Concentration Risk [Member] | Minimum [Member]
Concentration Risk [Line Items]
Number of customers	3
Customer Concentration Risk [Member] | Maximum [Member]
Concentration Risk [Line Items]
Number of customers	5
Accounts Receivable [Member] | Customer Concentration Risk [Member] | Customer One [Member]
Concentration Risk [Line Items]
Concentration risk, percentage	19.10%	20.90%	20.30%
Accounts Receivable [Member] | Customer Concentration Risk [Member] | Customer Two [Member]
Concentration Risk [Line Items]
Concentration risk, percentage	15.00%	14.00%	16.50%
Accounts Receivable [Member] | Customer Concentration Risk [Member] | Customer Three [Member]
Concentration Risk [Line Items]
Concentration risk, percentage	11.10%	10.10%	12.70%
Accounts Receivable [Member] | Customer Concentration Risk [Member] | Customer Four [Member]
Concentration Risk [Line Items]
Concentration risk, percentage	10.40%
Sales Revenue, Goods, Net [Member] | Customer Concentration Risk [Member]
Concentration Risk [Line Items]
Concentration risk, percentage	50.00%
Sales Revenue, Goods, Net [Member] | Customer Concentration Risk [Member] | Customer One [Member]
Concentration Risk [Line Items]
Concentration risk, percentage	22.80%	18.20%	24.40%
Sales Revenue, Goods, Net [Member] | Customer Concentration Risk [Member] | Customer Two [Member]
Concentration Risk [Line Items]
Concentration risk, percentage	17.10%	16.50%	13.80%
Sales Revenue, Goods, Net [Member] | Customer Concentration Risk [Member] | Customer Three [Member]
Concentration Risk [Line Items]
Concentration risk, percentage	10.80%	15.90%
Sales Revenue, Goods, Net [Member] | Customer Concentration Risk [Member] | Customer Four [Member]
Concentration Risk [Line Items]
Concentration risk, percentage	10.70%	10.60%