Summary of Significant Accounting Policies - Revenue Recognition, Trade Accounts Receivable and Concentration of Credit Risk (Details) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Cost of Sales from services									$ 84,453	$ 73,111	$ 57,233
Cost of Sales from products									111,627	155,516	113,399
Allowance for bad debt and credit activity
Beginning balance				$ 212				$ 272	212	272
Bad debt expense									12	28
Write-off of uncollectible accounts									(90)	(81)
Currency translation adjustment									(8)	(7)
Ending balance	$ 126				$ 212				126	212	272
Net sales	$ 67,380	$ 81,202	$ 73,725	$ 86,393	$ 93,567	$ 107,697	$ 95,536	$ 77,310	308,700	374,110	261,006
Net sales
Revenue
Freight revenue									4,651	3,882	4,249
Customer Concentration Risk
Allowance for bad debt and credit activity
Net sales											$ 29,523
Customer Concentration Risk | Net sales
Allowance for bad debt and credit activity
Net sales									$ 0	$ 0
Concentration risk (as a percent)											11.30%