Principal Business Activity and Significant Accounting Policies - Adopted Accounting Standard Updates (“ASU”) (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017	Dec. 31, 2017
Condensed Consolidated Statements of Operations
Revenues	$ 171,142	$ 87,178	$ 286,208	$ 154,207
Cost of sales	144,824	71,227	244,007	126,056
General and administrative expenses	16,943	9,277	35,911	16,682
Income tax (expense) benefit	(1,020)		47
Net Income	5,398	$ 6,070	1,441	$ 10,349
Assets
Accounts receivable	50,910		50,910		$ 21,759
Inventories	81,208		81,208		44,056
Other current assets	1,967		1,967		1,991
Liabilities and equity
Accounts payable	65,291		65,291		14,234
Accumulated deficit	(3,197)		(3,197)		$ (3,493)
Adjustments
Condensed Consolidated Statements of Operations
Revenues			5,965
Cost of sales			3,734
General and administrative expenses			444
Income tax (expense) benefit			(286)
Net Income			1,501
Balance Without Adoption of ASC 606
Condensed Consolidated Statements of Operations
Revenues			292,173
Cost of sales			247,741
General and administrative expenses			36,355
Income tax (expense) benefit			(239)
Net Income			2,942
ASU 2014-09 | Adjustments
Condensed Consolidated Statements of Operations
Revenues	5,349
Cost of sales	3,748
General and administrative expenses	345
Income tax (expense) benefit	(202)
Net Income	1,054
Assets
Accounts receivable	5,296		5,296
Inventories	(4,962)		(4,962)
Other current assets	426		426
Liabilities and equity
Accounts payable	(1,099)		(1,099)
Accumulated deficit	1,216		1,216
ASU 2014-09 | Balance Without Adoption of ASC 606
Condensed Consolidated Statements of Operations
Revenues	176,491
Cost of sales	148,572
General and administrative expenses	17,288
Income tax (expense) benefit	(1,222)
Net Income	6,452
Assets
Accounts receivable	56,206		56,206
Inventories	76,246		76,246
Other current assets	2,393		2,393
Liabilities and equity
Accounts payable	64,192		64,192
Accumulated deficit	$ (1,981)		$ (1,981)