| Property, plant and equipment, net | 12 Months Ended | |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
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| Dec. 31, 2018 | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Property, plant and equipment, net | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Property, plant and equipment, net | Note 6 — Property, plant and equipment, net Property and equipment, net consisted of the following (in thousands): 
 
 Depreciation expense was $7,188,000, $5,032,000 and $3,126,000 for the years ended December 31, 2018 2017, and 2016, respectively. The Company has disposed of leasehold improvements resulting in a loss on disposal of $7,000, $194,000 and $122,000 in the years ended December 31, 2018 and 2017, respectively, which is included within general and administrative expenses in the statement of operations. | |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||