Summary of Significant Accounting Policies - Revenue Recognition, Trade Accounts Receivable and Concentration of Credit Risk (Details) - USD ($) $ in Thousands	3 Months Ended								6 Months Ended		9 Months Ended		12 Months Ended
	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Jun. 30, 2015	Jun. 30, 2014	Sep. 30, 2015	Sep. 30, 2014	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Cost of Sales from services													$ 73,111	$ 57,233	$ 63,054
Cost of Sales from products													155,516	113,399	66,154
Allowance for bad debt and credit activity
Beginning balance				$ 272				$ 1,365	$ 272	$ 1,365	$ 272	$ 1,365	272	1,365
Bad debt expense													28	(100)
Write-off of uncollectible accounts													(81)	(986)
Currency translation adjustment													(7)	(7)
Ending balance	$ 212				$ 272								212	272	1,365
Net sales	$ 93,567	$ 107,697	$ 95,536	77,310	$ 87,865	$ 77,374	$ 53,236	42,531					374,110	261,006	196,370
Adjustment for Immaterial Error in Classification of Cost of Sales Between Services And Products [Member]
Cost of Sales from services		(4,349)	1,146	508		(1,124)	806	1,400	1,654	2,206	(2,695)	1,082		(7,819)
Cost of Sales from products		$ 4,349	$ (1,146)	$ (508)		$ 1,124	$ (806)	$ (1,400)	$ (1,654)	$ (2,206)	$ 2,695	$ (1,082)		7,819
Net sales
Revenue
Freight revenue													3,882	4,249	4,278
Customer Concentration Risk
Allowance for bad debt and credit activity
Net sales														$ 29,523	$ 31,924
Customer Concentration Risk | Net sales
Allowance for bad debt and credit activity
Net sales													$ 0
Concetration risk (as a percent)														11.30%	16.30%