Significant Accounting Policies - Impact of Adoption of ASC 606 (Details) $ in Thousands	3 Months Ended
	Mar. 31, 2018 USD ($) item	Mar. 31, 2017 USD ($)
Recently Adopted Accounting Standards
Cost of goods sold	$ 130,342	$ 106,075
Gross margin	$ (4,541)	$ 16,368
Accounting Standards Update 2014-09
Recently Adopted Accounting Standards
Number of revenue categories | item	2
Accounting Standards Update 2014-09 | Calculated under Revenue Guidance in Effect before Topic 606
Recently Adopted Accounting Standards
Cost of goods sold	$ 124,068
Gross margin	(4,541)
Accounting Standards Update 2014-09 | Difference between Revenue Guidance in Effect before and after Topic 606
Recently Adopted Accounting Standards
Cost of goods sold	(6,274)
Product sales
Recently Adopted Accounting Standards
Revenue	122,799
Product sales | Accounting Standards Update 2014-09 | Calculated under Revenue Guidance in Effect before Topic 606
Recently Adopted Accounting Standards
Revenue	116,578
Product sales | Accounting Standards Update 2014-09 | Difference between Revenue Guidance in Effect before and after Topic 606
Recently Adopted Accounting Standards
Revenue	(6,221)
Other revenue
Recently Adopted Accounting Standards
Revenue	3,002
Other revenue | Accounting Standards Update 2014-09 | Calculated under Revenue Guidance in Effect before Topic 606
Recently Adopted Accounting Standards
Revenue	2,949
Other revenue | Accounting Standards Update 2014-09 | Difference between Revenue Guidance in Effect before and after Topic 606
Recently Adopted Accounting Standards
Revenue	$ (53)