Selected Quarterly Financial Data (Unaudited) - CONDENSED CONSOLIDATED STATEMENTS OF CASH FLOWS (Details) - USD ($) $ in Thousands	3 Months Ended								6 Months Ended		9 Months Ended		12 Months Ended
	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Jun. 30, 2018	Jun. 30, 2017	Sep. 30, 2018	Sep. 30, 2017	Dec. 31, 2018	Dec. 31, 2017
Cash provided by (used in) operating activities
Net loss	$ (9,898)	$ (18,819)	$ (11,805)	$ (14,204)	$ (6,129)	$ (9,201)	$ (7,747)	$ (24,535)	$ (26,009)	$ (32,282)	$ (44,828)	$ (41,483)	$ (54,726)	$ (47,612)
Adjustments to reconcile net (loss) income to net cash provided by operating activities:
Amortization of intangible assets				1,045				1,209	2,366	2,419	3,687	3,628	5,008	4,838
Depreciation				1,196				1,172	2,524	2,342	3,849	3,502	5,196	4,634
Change in valuation of warrants				2,500				0	9,000	800	19,200	2,500	10,400	4,000
Stock compensation expense				799				(865)	1,418	(1,028)	1,963	(297)	2,662	473
Amortization of financing fees				341				3,109	659	3,441	947	3,778	1,497	4,117
Deferred income taxes				(276)				469	(208)	602	(87)	746	(56)	239
Loss on debt extinguishment and modifications								11,921		11,921		11,921	0	11,921
Asset impairment charges													2,234	1
(Decrease) increase in allowance for doubtful accounts								48		131		216
Provision for inventory obsolescence								146		539		882
Loss (gain) on disposal of fixed assets								10		66		115
Other non-cash adjustments, net				(350)				137	325	200	1,661	190	2,086	924
Changes in operating assets and liabilities:
Trade accounts receivable, net				9,710				(4,017)	(1,739)	3,532	(3,058)	(691)	(17,890)	(8,391)
Inventory, net				(9,822)				3,122	(14,825)	(3,326)	(32,657)	(13,408)	(26,202)	13,366
Prepaid expenses and other assets				(76)				(1,624)	(4,815)	1,238	(5,387)	(1,359)	(886)	(2,284)
Trade accounts payable				3,748				15,186	13,200	3,244	37,355	1,879	33,968	(1,198)
Income taxes refundable				8				298	(2)	5,135	7	6,293	125	6,508
Accrued expenses				4,757				1,861	7,914	3,826	10,773	10,622	11,630	7,839
Other noncurrent liabilities				2,902				450	2,000	(1,478)	2,901	(2,576)	18,786	(7,070)
Net cash used in operating activities				2,278				8,097	(8,192)	1,322	(3,674)	(13,542)	(6,168)	(7,695)
Cash used in investing activities
Capital expenditures				(467)				(1,896)	(1,588)	(2,669)	(2,321)	(3,856)	(3,645)	(5,061)
Asset acquisitions				(1,029)					(6,595)		(6,595)		(6,595)	(300)
Other sources, net								0		245		245	1	196
Net cash used in investing activities				(1,496)				(1,896)	(8,183)	(2,424)	(8,916)	(3,611)	(10,239)	(5,165)
Cash provided by financing activities
Repayments of long-term debt								(71,400)		(71,400)		(71,400)	0	(71,400)
Financing fees								(253)		(928)		(928)
Net proceeds from stock offering and warrants								59,396		59,396		59,396	0	59,396
Proceeds from revolving line of credit				106,216				85,945	240,698	209,082	372,557	324,416	516,440	436,228
Repayments of revolving line of credit				(106,608)				(81,833)	(223,419)	(196,593)	(357,121)	(295,859)	(498,881)	(411,948)
Acquisition of businesses contingent consideration payments								(6)		(9)		(19)
Other uses, net				(390)				0	(902)	(738)	(832)	(745)	(1,098)	(1,708)
Net cash provided by financing activities				(782)				(8,151)	16,377	(1,190)	14,604	14,861	16,461	10,568
Net (decrease) increase in cash and restricted cash				0				(1,950)	2	(2,292)	2,014	(2,292)	54	(2,292)
Cash at beginning of the year	2,014	2	0	0	0	0	342	2,292	0	2,292	0	2,292	0	2,292
Cash at end of the year	$ 54	$ 2,014	$ 2	$ 0	$ 0	$ 0	$ 0	$ 342	$ 2	$ 0	$ 2,014	$ 0	$ 54	$ 0