Summary of Significant Accounting Policies - Inventory (Details) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Inventory, net
Raw materials	$ 124,635	$ 84,431
Work-in-progress	19,113	1,204
Finished goods	22,559	17,960
Total inventory	166,307	$ 103,595
Inventory Valuation Reserves	$ 28,900