Basis of Presentation and Significant Accounting Policies - Concentration Risks (Details) - Customer Concentration Risk [Member] - Sales [Member] - customer	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Product Information [Line Items]
Customers above benchmark (in customers)	2	1	2
Concentration risk, percentage	10.00%	10.00%	10.00%
Customer A
Product Information [Line Items]
Concentration risk, percentage	11.30%	16.30%
Customer B
Product Information [Line Items]
Concentration risk, percentage	10.10%
Customer C
Product Information [Line Items]
Concentration risk, percentage			14.50%
Customer D
Product Information [Line Items]
Concentration risk, percentage			12.50%