Power Solutions International (PSIX) 10-K 16 May 19 2017 FY Annual report Financial data

Document and Entity Information

Document and Entity Information - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	May 03, 2019	Jun. 30, 2017
Document And Entity Information [Abstract]
Entity Registrant Name	POWER SOLUTIONS INTERNATIONAL, INC.
Entity Central Index Key	0001137091
Current Fiscal Year End Date	--12-31
Entity Filer Category	Non-accelerated Filer
Document Type	10-K
Document Period End Date	Dec. 31, 2017
Document Fiscal Year Focus	2017
Document Fiscal Period Focus	FY
Amendment Flag	false
Entity Shell Company	false
Entity Common Stock, Shares Outstanding		22,807,623
Entity Well-known Seasoned Issuer	No
Entity Voluntary Filers	No
Entity Current Reporting Status	No
Entity Emerging Growth Company	false
Entity Small Business	true
Entity Public Float			$ 43.3

CONSOLIDATED BALANCE SHEETS

CONSOLIDATED BALANCE SHEETS - USD ($) $ in Thousands	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Current assets:
Cash and cash equivalents	$ 0	$ 0	$ 0	$ 342	$ 2,292	$ 1,610	$ 435	$ 1,495	$ 8,445	$ 6,561	$ 6,306
Accounts receivable, net of allowances of $1,820, $1,045, $816 and $306 for 2017, 2016, 2015 and 2014, respectively	68,660	60,811	56,673	64,305	60,336	53,364	57,884	45,384	70,532	76,266
Income tax receivable	1,018	841	1,996	6,829	7,127	5,737	3,384	1,723	5,265	0
Inventories, net	86,724	113,074	103,335	97,286	100,548	111,133	115,062	139,519	162,095	106,250
Prepaid expenses and other current assets	14,359	14,536	12,453	15,291	13,644	5,146	4,026	4,132	2,703	4,840
Deferred income taxes										8,552
Total current assets	170,761	189,262	174,457	184,053	183,947	176,990	180,791	192,253	249,040	202,469
Property, plant and equipment, net	18,960	18,974	19,050	19,230	20,127	20,257	20,386	20,662	22,809	17,954
Intangible assets, net	21,491	22,401	23,610	24,819	26,029	27,459	28,888	30,316	31,745	21,192
Goodwill	29,835	29,835	29,835	29,835	29,835	29,835	29,835	29,835	29,835	23,414	0
Deferred income taxes	0				0	0	0	19,285	17,657	13
Other noncurrent assets	5,972	6,035	4,518	5,053	4,681	2,821	2,621	2,664	2,751	1,903
TOTAL ASSETS	247,019	266,507	251,470	262,990	264,619	257,362	262,521	295,015	353,837	266,945
Current liabilities:
Accounts payable	51,225	54,195	55,610	67,167	53,588	45,764	49,729	43,160	79,823	67,713
Current maturities of long-term debt	0				750	375	0	0	0	1,667
Contingent consideration	12	20	29	30	26	88	100	5,481	8,275	0
Revolving line of credit, current	37,055	41,332	25,263	16,887	12,774	16,994	14,038	0	0	0
Other accrued liabilities	38,362	41,393	35,379	35,234	32,507	22,405	19,182	17,929	17,846	18,182
Total current liabilities	126,654	136,940	116,281	119,318	99,645	85,626	83,049	66,570	105,944	87,562
Revolving line of credit	0				0	0	0	80,568	97,299	78,030
Deferred income taxes	703	1,210	1,066	933	464	522	372	0	0
Deferred income taxes										0
Warrants	24,700	23,200	21,500	20,700	0	0	0	226	1,482	11,036
Long-term debt, less current maturities, net	54,439	54,305	54,168	54,045	110,392	111,517	110,929	53,799	53,805	2,361
Other noncurrent liabilities	8,351	13,312	12,438	13,328	13,458	12,730	12,833	11,952	10,434	1,473
TOTAL LIABILITIES	214,847	228,967	205,453	208,324	223,959	210,395	207,184	213,115	268,964	180,462
STOCKHOLDERS’ EQUITY
Preferred stock - $0.001 par value. Shares authorized: 5,000. No shares issued and outstanding at all dates.	0	0	0	0	0	0	0	0	0	0
Common stock - $0.001 par value; 50,000 shares authorized; 19,067, 11,567, 11,413 and 11,408 shares issued; 18,433, 10,922, 10,753 and 10,731 shares outstanding at December 31, 2017, 2016, 2015 and 2014, respectively	19	14	14	14	12	12	12	11	11	11
Additional paid-in capital	123,838	91,737	96,543	100,686	86,764	86,408	86,043	83,729	83,377	81,746
(Accumulated deficit) retained earnings	(82,147)	(76,018)	(66,817)	(59,070)	(34,535)	(27,895)	(19,180)	9,612	12,937	15,828
Treasury stock, at cost; 634, 645, 660 and 677 shares at December 31, 2017, 2016, 2015 and 2014, respectively	(9,538)	(9,604)	(11,530)	(11,582)	(11,581)	(11,558)	(11,537)	(11,452)	(11,452)	(11,102)
TOTAL STOCKHOLDERS’ EQUITY	32,172	6,129	18,210	30,048	40,660	46,967	55,337	81,900	84,873	86,483	$ 47,607
TOTAL LIABILITIES AND STOCKHOLDERS’ EQUITY	$ 247,019	$ 266,507	$ 251,470	$ 262,990	$ 264,619	$ 257,362	$ 262,521	$ 295,015	$ 353,837	$ 266,945

CONSOLIDATED BALANCE SHEETS (Pa

CONSOLIDATED BALANCE SHEETS (Parenthetical) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Statement of Financial Position [Abstract]
Accounts receivable allowance	$ 1,820	$ 1,045	$ 816	$ 306
Series A convertible preferred stock, par value (in dollars per share)	$ 0.001	$ 0.001	$ 0.001	$ 0.001
Series A convertible preferred stock, authorized (in shares)	5,000,000	5,000,000	5,000,000	5,000,000
Series A convertible preferred stock, issued (in shares)	0	0	0	0
Series A convertible preferred stock, outstanding (in shares)	0	0	0	0
Common stock, par value (in dollars per share)	$ 0.001	$ 0.001	$ 0.001	$ 0.001
Common stock, authorized (in shares)	50,000,000	50,000,000	50,000,000	50,000,000
Common stock, issued (in shares)	19,067,000	11,567,000	11,413,000	11,408,000
Common stock, outstanding (in shares)	18,433,000	10,922,000	10,753,000	10,731,000
Treasury stock (in shares)	634,000	645,000	660,000	677,000

CONSOLIDATED STATEMENTS OF OPER

CONSOLIDATED STATEMENTS OF OPERATIONS - USD ($) shares in Thousands, $ in Thousands	3 Months Ended								6 Months Ended		9 Months Ended		12 Months Ended
	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Jun. 30, 2017	Jun. 30, 2016	Sep. 30, 2017	Sep. 30, 2016	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Income Statement [Abstract]
Net sales	$ 131,476	$ 99,953	$ 100,922	$ 84,265	$ 98,280	$ 78,944	$ 85,771	$ 76,470					$ 416,616	$ 339,465	$ 362,387	$ 347,580
Cost of sales	115,981	86,702	88,443	74,497	86,376	72,820	81,253	69,827					365,623	310,276	311,148	283,540
Gross profit	15,495	13,251	12,479	9,768	11,904	6,124	4,518	6,643					50,993	29,189	51,239	64,040
Operating expenses:
Research, development and engineering expenses	6,459	5,687	3,848	3,950	4,742	4,498	4,817	4,904					19,944	18,961	23,574	19,305
Selling, general and administrative expenses	11,297	12,062	10,688	10,209	8,563	6,855	6,699	6,405					44,256	28,522	28,837	23,142
Asset impairment charges	1	0	0	0	167	38	1,064	345					1	1,614	11,686	310
Amortization of intangible assets	1,210	1,210	1,209	1,209	1,430	1,429	1,429	1,428					4,838	5,716	4,582	1,013
Change in fair value of contingent consideration					0	0	(283)	0					0	(283)	(23)	(3,840)
Total operating expenses	18,967	18,959	15,745	15,368	14,902	12,820	13,726	13,082					69,039	54,530	68,656	39,930
Operating (loss) income	(3,472)	(5,708)	(3,266)	(5,600)	(2,998)	(6,696)	(9,208)	(6,439)					(18,046)	(25,341)	(17,417)	24,110
Other expense (income):
Interest expense	1,703	1,654	1,404	6,080	4,402	3,726	1,649	1,438					10,841	11,215	4,320	1,342
Loss (gain) from change in fair value of warrants	1,500	1,700	800	0	0	0	(157)	(1,256)					4,000	(1,413)	(9,300)	(6,170)
Loss on debt extinguishment and modifications	0	0	0	11,921	332	25	0	0					11,921	357	12	0
Other expense (income), net	(225)	(9)	2,142	453	146	62	92	59					2,361	359	144	(283)
Total other expense (income)	2,978	3,345	4,346	18,454	4,880	3,813	1,584	241					29,123	10,518	(4,824)	(5,111)
(Loss) income before income taxes	(6,450)	(9,053)	(7,612)	(24,054)	(7,878)	(10,509)	(10,792)	(6,680)					(47,169)	(35,859)	(12,593)	29,221
Income tax expense (benefit)	(320)	149	135	479	(1,238)	(1,792)	18,000	(3,357)					443	11,613	(9,702)	7,744
Net (loss) income	(6,130)	(9,202)	(7,747)	(24,533)	$ (6,640)	$ (8,717)	$ (28,792)	$ (3,323)	$ (32,280)	$ (32,115)	$ (41,482)	$ (40,832)	(47,612)	(47,472)	(2,891)	21,477
Deemed dividend on Series B preferred stock	(31,067)	(3,603)	(3,190)	0									(37,860)	0	0	0
Net (loss) income available to common stockholders	$ (37,197)	$ (12,805)	$ (10,937)	$ (24,533)									$ (85,472)	$ (47,472)	$ (2,891)	$ 21,477
Weighted-average common shares outstanding:
Basic (in shares)								10,819					13,787	10,931	10,808	10,705
Diluted (in shares)								10,819					13,787	10,931	10,991	11,131
(Loss) earnings per common share:
Basic (in dollars per share)								$ (0.42)					$ (6.20)	$ (4.34)	$ (0.27)	$ 2.01
Diluted (in dollars per share)								$ (0.42)					$ (6.20)	$ (4.47)	$ (1.11)	$ 1.38

CONSOLIDATED STATEMENTS OF CONV

CONSOLIDATED STATEMENTS OF CONVERTIBLE PREFERRED STOCK AND STOCKHOLDERS' EQUITY - USD ($) $ in Thousands	Total	Preferred Stock	Common Stock	Additional Paid-in Capital	Treasury Stock	Retained Earnings (Accumulated Deficit)
Beginning balance at Dec. 31, 2013	$ 47,607	$ 0	$ 11	$ 61,930	$ (8,685)	$ (5,649)
Increase (Decrease) in Stockholders' Equity
Net (loss) income	21,477					21,477
Acquisition consideration, net of tax	4,379			4,379
Stock-based compensation expense	1,409			3,826	(2,417)
Stock-based compensation net settlement for withholding taxes	(430)			(430)
Excess tax benefit from exercise of stock-based awards	3,298			3,298
Exercise of private placement warrants	8,743			8,743
Ending balance at Dec. 31, 2014	86,483	0	11	81,746	(11,102)	15,828
Increase (Decrease) in Stockholders' Equity
Net (loss) income	(2,891)					(2,891)
Stock-based compensation expense	1,278			1,628	(350)
Stock-based compensation net settlement for withholding taxes	(351)			(351)
Excess tax benefit from exercise of stock-based awards	34			34
Exercise of private placement warrants	320			320
Ending balance at Dec. 31, 2015	84,873	0	11	83,377	(11,452)	12,937
Increase (Decrease) in Stockholders' Equity
Net (loss) income	(3,323)
Ending balance at Mar. 31, 2016	81,900
Beginning balance at Dec. 31, 2015	84,873	0	11	83,377	(11,452)	12,937
Increase (Decrease) in Stockholders' Equity
Net (loss) income	(32,115)
Ending balance at Jun. 30, 2016	55,337
Beginning balance at Dec. 31, 2015	84,873	0	11	83,377	(11,452)	12,937
Increase (Decrease) in Stockholders' Equity
Net (loss) income	(40,832)
Ending balance at Sep. 30, 2016	46,967
Beginning balance at Dec. 31, 2015	84,873	0	11	83,377	(11,452)	12,937
Increase (Decrease) in Stockholders' Equity
Net (loss) income	(47,472)					(47,472)
Stock-based compensation expense	1,299			1,428	(129)
Stock-based compensation net settlement for withholding taxes	(110)			(110)
Exercise of private placement warrants	2,070		1	2,069
Ending balance at Dec. 31, 2016	40,660	0	12	86,764	(11,581)	(34,535)
Beginning balance at Mar. 31, 2016	81,900
Increase (Decrease) in Stockholders' Equity
Net (loss) income	(28,792)
Ending balance at Jun. 30, 2016	55,337
Increase (Decrease) in Stockholders' Equity
Net (loss) income	(8,717)
Ending balance at Sep. 30, 2016	46,967
Increase (Decrease) in Stockholders' Equity
Net (loss) income	(6,640)
Ending balance at Dec. 31, 2016	40,660	0	12	86,764	(11,581)	(34,535)
Increase (Decrease) in Stockholders' Equity
Net (loss) income	(24,533)
Ending balance at Mar. 31, 2017	30,048
Beginning balance at Dec. 31, 2016	40,660	0	12	86,764	(11,581)	(34,535)
Increase (Decrease) in Stockholders' Equity
Net (loss) income	(32,280)
Ending balance at Jun. 30, 2017	18,210
Beginning balance at Dec. 31, 2016	40,660	0	12	86,764	(11,581)	(34,535)
Increase (Decrease) in Stockholders' Equity
Net (loss) income	(41,482)
Ending balance at Sep. 30, 2017	6,129
Beginning balance at Dec. 31, 2016	40,660	0	12	86,764	(11,581)	(34,535)
Increase (Decrease) in Stockholders' Equity
Net (loss) income	(47,612)					(47,612)
Acquisition consideration, net of tax	(712)			(712)
Stock-based compensation expense	1,183			(860)	2,043
Stock-based compensation net settlement for withholding taxes	(42)			(42)
Issuance of common stock to Weichai, net of fees	14,078		2	14,076
Issuance of Series B convertible preferred stock, net of fees	0	24,617		0
Deemed dividend on Series B convertible preferred stock	(37,860)	37,860		(37,860)
Conversion of Series B convertible preferred stock to common stock	62,477	(62,477)	5	62,472
Ending balance at Dec. 31, 2017	32,172	0	19	123,838	(9,538)	(82,147)
Beginning balance at Mar. 31, 2017	30,048
Increase (Decrease) in Stockholders' Equity
Net (loss) income	(7,747)
Ending balance at Jun. 30, 2017	18,210
Increase (Decrease) in Stockholders' Equity
Net (loss) income	(9,202)
Ending balance at Sep. 30, 2017	6,129
Increase (Decrease) in Stockholders' Equity
Net (loss) income	(6,130)
Ending balance at Dec. 31, 2017	$ 32,172	$ 0	$ 19	$ 123,838	$ (9,538)	$ (82,147)

CONSOLIDATED STATEMENTS OF CASH

CONSOLIDATED STATEMENTS OF CASH FLOWS - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Cash (used in) provided by operating activities:
Net (loss) income	$ (47,612)	$ (47,472)	$ (2,891)	$ 21,477
Adjustments to reconcile net (loss) income to net cash (used in) provided by operating activities:
Amortization of intangible assets	4,838	5,716	5,287	2,108
Depreciation	4,634	4,582	4,030	2,520
Change in valuation of warrants	4,000	(1,413)	(9,300)	(6,170)
Stock compensation expense	473	1,619	1,501	1,487
Amortization of financing fees	4,117	3,048	443	87
Deferred income taxes	239	18,121	(9,058)	(1,624)
Loss on extinguishment of debt	11,921	357	12	0
Asset impairment charges	1	1,614	11,686	310
Tax benefit from exercise of stock-based compensation	0	(55)	0	0
Change in valuation of contingent consideration	0	(283)	(23)	(3,840)
Provision for doubtful accounts	67	80	288	70
Provision for inventory obsolescence	421	5,341	1,712	1,856
Loss (gain) on disposal of fixed assets	423	(663)	175	321
Other sources, net	13	413	681	612
Changes in operating assets and liabilities:
Trade accounts receivable, net	(8,391)	10,116	10,589	(30,682)
Inventory, net	13,366	55,564	(47,505)	(44,240)
Prepaid expenses and other assets	(2,284)	(12,893)	2,126	(3,224)
Trade accounts payable	(1,198)	(27,037)	5,913	37,647
Income taxes refundable (payable)	6,508	(1,783)	(7,673)	1,327
Accrued expenses	6,029	15,709	1,085	5,096
Other noncurrent liabilities	(5,260)	1,601	8,107	(232)
Net cash (used in) provided by operating activities	(7,695)	32,282	(22,815)	(15,094)
Cash flows from investing activities:
Capital expenditures	(5,061)	(3,872)	(8,409)	(8,214)
Proceeds from disposal of assets	0	2,466	0	0
Acquisitions of businesses, net of cash acquired	0	0	(34,227)	(44,122)
Other (uses) sources, net	(104)	(245)	(1,169)	14
Net cash used in investing activities	(5,165)	(1,651)	(43,805)	(52,322)
Cash flows from financing activities
Proceeds from issuance of long-term debt	0	60,000	55,000	5,000
Repayments of long-term debt	(71,400)		(4,028)	(972)
Financing fees	(928)	(5,802)	(1,517)	(154)
Net proceeds from stock offering and warrants	59,396	2,001	65	1,425
Proceeds from revolving line of credit	436,228	281,007	93,629	82,401
Repayments of revolving line of credit	(411,948)	(365,532)	(74,359)	(22,305)
Business acquisition contingent consideration payments	(26)	(8,348)	0	0
Tax benefit from exercise of stock-based compensation			65	2,706
Other uses, net	(754)	(110)	(351)	(430)
Net cash provided by (used in) financing activities	10,568	(36,784)	68,504	67,671
(Decrease) increase in cash	(2,292)	(6,153)	1,884	255
Cash at beginning of the year	2,292	8,445	6,561	6,306
Cash at end of the year	$ 0	$ 2,292	$ 8,445	$ 6,561

Summary of Significant Accounti

Summary of Significant Accounting Policies and Other Information	12 Months Ended
	Dec. 31, 2017
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Summary of Significant Accounting Policies and Other Information	Summary of Significant Accounting Policies and Other Information Nature of Business Operations Power Solutions International, Inc. (“Power Solutions,” “PSI” or “the Company”), a Delaware corporation, is a global producer and distributor of a broad range of high-performance, certified low-emission power systems, including alternative-fueled power systems for original equipment manufacturers (“OEMs”) of off-highway industrial equipment and certain on-road vehicles and large custom-engineered integrated electrical power generation systems. The Company’s customers include large, industry-leading and multinational organizations. The Company’s products and services are sold predominantly to customers throughout North America as well as to customers located throughout the Pacific Rim and Europe. The Company’s power systems are highly engineered, comprehensive systems which, through the Company's technologically sophisticated development and manufacturing processes, including its in-house design, prototyping, testing and engineering capabilities and its analysis and determination of the specific components to be integrated into a given power system (driven in large part by emission standards and cost considerations), allow the Company to provide its customers with power systems customized to meet specific industrial OEM application requirements, other technical customers' specifications and requirements imposed by environmental regulatory bodies. The Company’s power system configurations range from a basic engine integrated with appropriate fuel system components to completely packaged power systems that include any combination of cooling systems, electronic systems, air intake systems, fuel systems, housings, power takeoff systems, exhaust systems, hydraulic systems, enclosures, brackets, hoses, tubes and other assembled componentry. The Company also designs and manufactures large, custom engineered integrated electrical power generation systems for both standby and prime power applications. The Company purchases engines from third-party suppliers and produces internally-designed engines, all of which are then integrated into its power systems. Of the other components that the Company integrates into its power systems, a substantial portion consist of internally designed components and components for which it coordinates significant design efforts with third-party suppliers, with the remainder consisting largely of parts that are sourced off-the-shelf from third-party suppliers. Some of the key components (including purchased engines) embody proprietary intellectual property of the Company's suppliers. As a result of its design and manufacturing capabilities, the Company is able to provide its customers with a comprehensive power system that can be incorporated, using a single part number, directly into a customer’s specified application. Capitalizing on its expertise in developing and manufacturing emission certified power systems and its access to the latest power system technologies, the Company believes that it is able to provide complete power systems to OEMs at a low cost and with fast design turnaround. In addition to the certified products described above, the Company sells diesel, gasoline and non-certified power systems and aftermarket components. In March 2017, the Company executed a share purchase agreement (the “SPA”) with Weichai America Corp., a wholly-owned subsidiary of Weichai Power Co., Ltd. (HK2338, SZ000338) (herein collectively referred to as “Weichai”). Under the terms of the SPA, Weichai invested $60.0 million in the Company purchasing a combination of newly issued Common and Preferred Stock as well as a stock purchase warrant (the “Weichai Warrant”). Stock Ownership and Control As of May 3, 2019 , Weichai owned 51.5% of the Company’s outstanding shares of Common Stock. Additionally, Gary S. Winemaster, the Company's founder, former Chairman of the Board, Chief Executive Office and President and nonexecutive Chief Strategy Officer, owned approximately 16.1% of the Company's outstanding shares of Common Stock, and Kenneth J. Winemaster, the Company's Executive Vice President, owned approximately 9.7% of the Company's outstanding shares of Common Stock. Each of these stockholders, by virtue of their significant equity ownership in the Company, may be able to significantly influence all matters requiring stockholder approval, including the election and removal of Directors and any merger or other significant corporate transactions. The interest of these stockholders may not coincide with the interests of other stockholders. The concentration of ownership might also have the effect of delaying or preventing a change of control of the Company that other stockholders may view as beneficial. With the exercise of the Weichai Warrant on April 23, 2019, Weichai alone owns a majority of the outstanding shares of Common Stock and, therefore, possesses voting control over the Company sufficient to prevent any change of control from occurring. Weichai entered into an Investor Rights Agreement (the “Rights Agreement”) with the Company upon execution of the SPA. The Rights Agreement provides Weichai with representation on the Company’s Board of Directors (the “Board”) and management representation rights. To date, Weichai currently has three representatives on the Board. According to the Rights Agreement, with Weichai exercising the Weichai Warrant and becoming the owner of 51% of the outstanding shares of the Common Stock calculated on a fully-diluted as-converted basis (excluding certain excepted issuances), the Company shall cause the appointment to the Board of an additional individual designated by Weichai, and Weichai shall thereafter have the right to nominate for election four Directors and any additional number of designees necessary to ensure that its designees constitute the majority of the Directors serving on the Board. According to the Rights Agreement, during any period when the Company is a “controlled company” within the meaning of the NASDAQ Listing Rules, it will take such measures as to avail itself of the “controlled company” exemptions available under Rule 5615 of the NASDAQ Listing Rules of Rules 5605(b), (d) and (e). With Weichai becoming a majority beneficial owner of the Company's outstanding shares of its Common Stock, Weichai is able to exercise control over matters requiring stockholders' approval, including the election of the Directors, amendment of the Company's Charter and approval of significant corporate transactions. This control could have the effect of delaying or preventing a change of control of the Company or changes in management and will make the approval of certain transactions impractical without the support of Weichai. Going Concern Considerations The Company's management has concluded as of December 31, 2017 that, due to uncertainties surrounding the Company’s ability to amend or refinance its current debt agreements and the uncertainty as to whether it will have sufficient liquidity to fund its business activities, substantial doubt exists as to its ability to continue as a going concern. The Company’s plans to alleviate the substantial doubt about its ability to continue as a going concern may not be successful, and it may be forced to limit its business activities or be unable to continue as a going concern, which would have a material adverse effect on its results of operations and financial condition. The consolidated financial statements included herein have been prepared assuming that the Company will continue as a going concern and contemplating the realization of assets and the satisfaction of liabilities and commitments in the normal course of business. The Company's ability to continue as a going concern is dependent on generating profitable operating results, having sufficient liquidity, maintaining compliance with the covenants and other requirements under the Wells Fargo Credit Agreement (the “Wells Fargo Credit Agreement”) with Wells Fargo Bank, N.A. (“Wells Fargo”) and the Unsecured Senior Notes (the “Unsecured Senior Notes”), and refinancing or repaying the indebtedness outstanding under those agreements. The current Wells Fargo Credit Agreement maturity date is the earlier of March 31, 2021, or 60 days prior to the final maturity of the Unsecured Senior Notes, which currently mature on January 1, 2020, resulting in a current maturity date of November 2, 2019 for the Wells Fargo Credit Agreement. Based on the Company’s current forecasts, without additional financing, the Company anticipates that it will not have sufficient cash and cash equivalents to repay the Unsecured Senior Notes by November 1, 2019. Management plans to seek additional liquidity from other lenders by November 1, 2019 to avoid acceleration of the Wells Fargo Credit Agreement. There can be no assurance that the Company's management will be able to effect a financing on acceptable terms or repay this outstanding indebtedness, when required or if at all. The consolidated financial statements included in this Form 10-K do not include any adjustments that might result from the outcome of the Company’s efforts to address these issues. Furthermore, if the Company cannot raise capital on acceptable terms, it may not, among other things, be able to: • Continue to expand the Company's research and product investments and sales and marketing organization; • Expand operations both organically and through acquisitions; and • Respond to competitive pressures or unanticipated working capital requirements. Basis of Presentation and Consolidation The Company is filing this Annual Report on Form 10-K for the year ended December 31, 2017, which contains audited consolidated financial statements as of and for the years ended December 31, 2017, 2016, 2015 and 2014. The consolidated financial statements for 2015 and 2014 included herein restate and replace the Company's previously issued audited annual consolidated financial statements, which were filed with the United States Securities and Exchange Commission (the “SEC”). Accordingly, investors should rely only on the financial information and other disclosures regarding the Company's consolidated financial statements in this Form 10-K or in future filings with the SEC, as applicable, and not on any previously issued or filed reports, earnings releases or similar communications relating to these periods. See Note 2. Restatement of Previously Issued Consolidated Financial Statements for additional information regarding the restatement adjustments for 2015 and 2014. The consolidated financial statements include the accounts of Power Solutions International, Inc. and its wholly-owned subsidiaries. The Company's Consolidated Financial Statements were prepared in accordance with generally accepted accounting principles in the United States (“U.S. GAAP”) and include the assets, liabilities, sales and expenses of all wholly-owned subsidiaries and majority-owned subsidiaries in which the Company exercises control. All intercompany balances and transactions have been eliminated in consolidation. The Company operates as one business and geographic operating segment. Operating segments are defined as components of a business that can earn revenues and incur expenses for which discrete financial information is available that is evaluated on a regular basis by the chief operating decision maker (“CODM”). The Company’s CODM is its principal executive officer, who decides how to allocate resources and assess performance. A single management team reports to the CODM, who manages the entire business. The Company’s CODM reviews Consolidated Statements of Operations to make decisions, allocate resources and assess performance, and the CODM does not evaluate the profit or loss from any separate geography or product line. Concentrations and Entity-wide Information The following table summarizes net sales by end market: (in thousands) For the Year Ended December 31, 2015 2014 End Market 2017 2016 (Restated) (Restated) Industrial $ 190,724 $ 164,245 $ 174,203 $ 155,935 Energy 159,008 115,367 137,190 191,528 Transportation 66,884 59,853 50,994 117 Total $ 416,616 $ 339,465 $ 362,387 $ 347,580 The following table summarizes net sales by geographic area: (in thousands) For the Year Ended December 31, 2015 2014 Geographic Area 2017 2016 (Restated) (Restated) North America $ 355,268 $ 304,621 $ 327,479 $ 323,474 Pacific Rim 42,221 22,827 25,356 17,719 Europe 14,205 11,065 9,552 5,705 Other 4,922 952 — 682 Total $ 416,616 $ 339,465 $ 362,387 $ 347,580 The following table presents customers individually accounting for more than 10% of the Company’s net sales: For the Year Ended December 31, 2015 2014 2017 2016 (Restated) (Restated) Customer A 16 % 17 % 16 % 10 % Customer B 10 % ** ** ** Customer C ** 12 % ** 10 % The following table presents customers individually accounting for more than 10% of the Company’s consolidated accounts receivable: As of December 31, 2015 2014 2017 2016 (Restated) (Restated) Customer A 18 % ** 17 % 15 % Customer B 13 % ** ** ** Customer C ** ** 12 % ** Customer D ** 30 % ** ** Customer E ** ** ** 16 % Customer F ** ** ** 11 % Customer G ** ** 10 % 11 % The following table presents suppliers individually accounting for more than 10% of the Company’s purchases: For the Year Ended December 31, 2015 2014 2017 2016 (Restated) (Restated) Supplier A 21 % 13 % 11 % 15 % Supplier B ** ** 18 % 21 % ** Less than 10% of the total Use of Estimates The preparation of consolidated financial statements in conformity with U.S. GAAP requires that management make estimates and assumptions that affect the reported amounts of assets and liabilities and disclosure of contingent assets and liabilities at the date of the consolidated financial statements and the reported amounts of revenue and expenses during the reporting period. Significant estimates and assumptions include the valuation of allowances for uncollectible receivables, inventory reserves, warranty reserves, stock-based compensation, evaluation of goodwill, plant and equipment for impairment, and determination of useful lives of long-lived assets. Actual results could materially differ from those estimates. Reclassifications Certain amounts recorded in the prior-period consolidated financial statements presented have been reclassified to conform to the current-period financial statement presentation. These reclassifications had no effect on previously reported results of operations. Cash and Cash Equivalents Cash equivalents consist of short-term, highly liquid investments that mature within three months or less. Such investments are stated at cost, which approximates fair value. The Company's revolving credit agreement currently includes a “lockbox” arrangement that receives all receipts and from which the Company can request increases in the revolver borrowings. See Note 7 . Debt for additional information regarding the Wells Fargo Credit Agreement. Stock-Based Compensation The Company accounts for stock-based compensation expense based on the grant date fair value on the award with the cost recognized over the requisite service period, which is generally the vesting period of the respective award. See Note 13. Stock-Based Compensation for additional information. Research and Development Research and development (“R&D”) expenses are expensed when incurred. R&D expenses consist primarily of wages, materials, testing and consulting related to the development of new engines, parts and applications. These costs were $18.4 million , $17.1 million , $21.5 million and $17.4 million for 2017, 2016, 2015 and 2014, respectively. Income Taxes The Company accounts for income taxes under the asset and liability method, which requires the recognition of deferred tax assets and liabilities for the expected future tax consequences of events that have been included in the financial statements. Under this method, deferred tax assets and liabilities are determined based on the differences between the financial statement and tax basis of assets and liabilities using enacted tax rates in effect for the year in which the differences are expected to be settled or realized. The effect of a change in tax rates on deferred tax assets and liabilities is recognized in income in the period that includes the enactment date. The Company records net deferred tax assets to the extent that it believes these assets will more likely than not be realized. In making such a determination, the Company considers all available positive and negative evidence, including future reversals of existing taxable temporary differences, projected future taxable income, tax-planning strategies and results of recent operations. As of December 31, 2017 and 2016, the Company had a valuation allowance of $32.0 million and $26.8 million , respectively. There was no valuation allowance recorded in 2015 or 2014. The Company records uncertain tax positions in accordance with accounting guidance, on the basis of a two-step process whereby (i) it determines whether it is more likely than not that the tax positions will be sustained based on the technical merits of the position and (ii) for those tax positions that meet the more-likely-than-not recognition threshold, the Company recognizes the largest amount of tax benefit that is greater than 50 percent likely to be realized upon ultimate settlement with the related tax authority. Tax benefits related to uncertain tax positions taken or expected to be taken on a tax return are recorded when such benefits meet a more-likely-than-not threshold. Otherwise, these tax benefits are recorded when a tax position has been effectively settled, which means that the appropriate taxing authority has completed its examination even though the statute of limitations remains open, or the statute of limitation has expired. Interest and penalties related to uncertain tax positions are recognized as part of income tax expense and are accrued beginning in the period that such interest and penalties would be applicable under relevant tax law until such time that the related tax benefits are recognized. As of December 31, 2017, 2016, 2015 and 2014, the Company had an unrecognized tax benefit of $1.3 million , $1.2 million , $1.3 million and $0.9 million , respectively, for uncertain tax positions excluding interest and penalties. The Company recognizes interest and penalties related to unrecognized tax benefits in income tax expense. On December 22, 2017, the President of the United States signed into law the Tax Cuts and Jobs Act (the “Tax Act”). The Tax Act includes a number of changes to existing U.S. tax laws that impact the Company, most notably a reduction of the U.S. corporate income tax rate from 34 percent to 21 percent for tax years beginning after December 31, 2017. The Tax Act also provides for the acceleration of depreciation for certain assets placed into service after September 27, 2017 as well as prospective changes beginning in 2018, including repeal of the domestic manufacturing deduction and additional limitations on executive compensation. The Company recognized the income tax effects of the Tax Act in its 2017 financial statements. The Company has analyzed the Tax Act, and remeasurement of U.S. deferred tax balances to reflect the new U.S. corporate income tax rate has been made. Accounts Receivable and Allowance for Doubtful Accounts Trade accounts receivable represent amounts billed to customers and not yet collected. Trade accounts receivable are recorded at the invoiced amount, which approximates net realizable value, and generally do not bear interest. The allowance for doubtful accounts is the Company’s best estimate of the amount of probable credit losses in the existing accounts receivable and is established through a charge to “Selling, general and administrative expenses.” The allowance is primarily determined based on historical collection experience and reviews of customer creditworthiness. Trade accounts receivable and the allowance for doubtful accounts are reviewed on a regular basis. When necessary, an allowance for the full amount of specific accounts deemed uncollectable is recorded. Accounts receivable losses are deducted from the allowance and the account balance is written off when the customer receivable is deemed uncollectable. Recoveries of previously written off balances are recognized when received. An allowance associated with anticipated future sales returns is also included in the allowance for doubtful accounts. Insurance Recoveries The Company records insurance recoveries related to amounts recorded as estimated losses on events covered by the Company's insurance policies when management determines that the recovery is probable and the amount can be reasonably determined. Inventories Inventories are stated at the lower of cost or net realizable value, which approximates current replacement cost. Cost is principally determined using the first-in, first-out method and includes material, labor and manufacturing overhead. It is the Company’s policy to review inventories on a continuing basis for obsolete, excess and slow-moving items and to record valuation adjustments for such items in order to eliminate non-recoverable costs from inventory. Valuation adjustments are recorded in an inventory reserve account and reduce the cost basis of the inventory in the period in which the reduced valuation is determined. Inventory reserves are established based on quantities on hand, usage and sales history, customer orders, projected demand and utilization within a current or future power system. Specific analysis of individual items or groups of items is performed based on these same criteria, as well as on changes in market conditions or any other identified conditions. Inventories consist of the following: (in thousands) As of December 31, 2015 2014 Inventories 2017 2016 (Restated) (Restated) Raw materials $ 71,732 $ 70,498 $ 102,912 $ 92,360 Work in process 4,535 9,270 12,315 6,021 Finished goods 16,684 30,862 52,136 11,904 Total Inventories 92,951 110,630 167,363 110,285 Inventory allowance (6,227 ) (10,082 ) (5,268 ) (4,035 ) Inventories, net $ 86,724 $ 100,548 $ 162,095 $ 106,250 Activity in the Company’s inventory allowance was as follows: (in thousands) For the Year Ended December 31, 2015 2014 Inventory Allowance 2017 2016 (Restated) (Restated) Balance at beginning of period $ 10,082 $ 5,268 $ 4,035 $ 2,982 Charged to expense 421 5,341 1,712 1,856 Write-offs (4,276 ) (527 ) (479 ) (803 ) Balance at end of year $ 6,227 $ 10,082 $ 5,268 $ 4,035 Prepaid Expenses and Other Current Assets Prepaid expenses and other current assets consist of the following: (in thousands) As of December 31, 2015 2014 Prepaid Expenses and Other Current Assets 2017 2016 (Restated) (Restated) Insurance proceeds receivable $ 10,563 $ 8,500 $ — $ — Prepaid expenses 3,710 4,072 2,578 4,840 Other 86 1,072 125 — Total $ 14,359 $ 13,644 $ 2,703 $ 4,840 Estimated insurance recoveries related to litigation reserves in “Other accrued liabilities” shown below are reflected as assets in the Company's Consolidated Balance Sheets when it is determined that the receipt of such amounts is probable, and the amount can be reasonably determined. Property, Plant and Equipment Property, plant and equipment are carried at cost and presented net of accumulated depreciation and impairments. Depreciation is computed using the straight-line method over the estimated useful lives of the assets. Property, plant and equipment are evaluated periodically to determine if an adjustment to depreciable lives is warranted. Such evaluation is based principally on the expected utilization of the long-lived assets. Repairs and maintenance costs are charged directly to expense as incurred. Major renewals or replacements that substantially extend the useful life of an asset are capitalized and depreciated. Estimated useful lives by each type of asset category are as follows: Years Buildings Up to 39 Leasehold improvements Lesser of (i) expected useful life of improvement or (ii) life of lease (including likely extension thereof) Machinery and equipment 1 to 10 Intangible Assets The Company’s intangible assets include backlog, customer relationships, developed technology, trade names and trademarks. Intangible assets are amortized on an accelerated basis over a period of time that approximates the pattern over which the Company expects to gain the estimated economic benefits, and such period generally ranges between three months and 15 years . The useful life of intangible assets is assessed and assigned based on the facts and circumstances specific to the acquisition. See additional information related to intangible assets in Note 5. Acquisitions . Impairment of Long-lived assets The Company assesses potential impairments to its long-lived assets or asset groups, excluding goodwill, which is separately tested for impairment, whenever events indicate that the carrying amount of such assets may not be recoverable. Long-lived assets are evaluated for impairment by comparing the carrying value of the asset or asset group with the estimated future net undiscounted cash flows expected to result from the use of the asset or asset group, including cash flows from disposition. If the future net undiscounted cash flows are less than the carrying value, an impairment loss is calculated. An impairment loss is determined by the amount that the asset’s or asset group’s carrying value exceeds its estimated fair value. Estimated fair value is generally measured by discounting estimated future cash flows. If an impairment loss is recognized, the adjusted balance becomes the new cost basis and is depreciated (amortized) over the remaining useful life. The Company also periodically reassesses the useful lives of its long-lived assets due to advances and changes in technologies. During 2016, 2015 and 2014, the Company recognized impairment charges of $1.6 million , $0.1 million and $0.3 million , respectively, related to the abandonment of certain fixed assets. Goodwill Goodwill represents the excess of the cost of an acquired business over the amounts assigned to the net acquired assets. Goodwill is not amortized but is tested for impairment at the reporting unit level, on an annual basis or more frequently, if events occur or circumstances change indicating potential impairment. The Company annually tests goodwill for impairment on October 1st. In evaluating goodwill for impairment, the Company may first assess qualitative factors to determine whether it is more likely than not (i.e., there is a likelihood of more than 50%) that the Company's fair value is less than its carrying amount. Qualitative factors that the Company considers include, but are not limited to, macroeconomic and industry conditions, overall financial performance and other relevant entity-specific events. If the Company bypasses the qualitative assessment, or if the Company concludes that it is more likely than not that the fair value of a reporting unit is less than its carrying value, then the Company performs a two-step goodwill impairment test to identify potential goodwill impairment and measures the amount of goodwill impairment it will recognize, if any. In the first step of the two-step goodwill impairment test, the Company compares the estimated fair value of the reporting unit with its related carrying value. The Company has had two reporting units since 2014: PSI and Professional Power Products, Inc. (“3PI”). If the estimated fair value exceeds the carrying amount, no further analysis is needed. If, however, the reporting unit's estimated fair value is less than its carrying amount, the Company proceeds to the second step and calculates the implied fair value of goodwill to determine whether any impairment is required. The Company calculates its estimated fair value using the income and market approaches when feasible, or an asset approach when neither the income nor the market approach has sufficient data. For the income approach, a discounted cash flow method, the Company uses internally developed discounted cash flow models that include the following assumptions, among others: projections of revenues, expenses and related cash flows based on assumed long-term growth rates and demand trends, expected future investments to grow new units, and estimated discount rates. The Company based these assumptions on its historical data and experience, third-party appraisals, industry projections, and micro and macro general economic condition projections and expectations. The market approach, also called the Guideline Public Company Approach, compares the value of an entity to similar publicly traded companies. The asset approach estimates the selling price the unit could achieve under assumed market conditions. If the fair value of a reporting unit exceeds its carrying amount, goodwill of the reporting unit is considered not impaired, and the second step of the impairment test is unnecessary. If the carrying amount of a reporting unit exceeds its fair value, the second step of the goodwill impairment test is performed to measure the amount of impairment loss, if any. The second step compares the implied fair value of the reporting unit goodwill with the carrying amount of that goodwill. If the carrying amount of reporting unit goodwill exceeds the implied fair value of that goodwill, an impairment loss is recognized in an amount equal to that excess. Other Accrued Liabilities Other accrued liabilities consisted of the following: (in thousands) As of December 31, 2015 2014 Other Accrued Liabilities 2017 2016 (Restated) (Restated) Warranty $ 12,628 $ 10,200 $ 4,429 $ 2,428 Litigation reserves * 12,137 10,287 3 — Deferred revenue 2,822 1,818 3,564 4,602 Accrued compensation and benefits 2,593 3,975 3,825 5,476 Professional services 1,974 1,509 544 500 Income taxes payable 375 131 107 2,973 Other 5,833 4,587 5,374 2,203 Total $ 38,362 $ 32,507 $ 17,846 $ 18,182 * Litigation reserves primarily consist of accruals for the settlement of the Securities Litigation as of December 31, 2017 and 2016 as well as the tentative settlement of the Federal Derivative Litigation as of December 31, 2017. The Company concluded that insurance recovery was probable and recognized full recovery of the settlement amounts in “Prepaid expenses and other assets”. See Note 10. Commitments and Contingencies for additional information. Warranty Costs The Company offers a standard limited warranty on the workmanship of its products that in most cases covers defects for a defined period. Warranties for certified emission products are mandated by the U.S. Environmental Protection Agency (the “EPA”) and/or the California Air Resources Board (the “CARB”) and are longer than the Company’s standard warranty on certain emission related products. The Company’s products also carry limited warranties from suppliers. Costs related to supplier warranty claims are borne by the supplier; the Company’s warranties apply only to the modifications made to supplier base products. Warranty estimates are based on historical experience and represent the projected cost associated with the product. A liability and related expense are recognized at the time products are sold. The Company adjusts estimates when it is determined that actual costs may differ from initial or previous estimates. Accrued product warranty activities are presented below: (in thousands) For the Year Ended December 31, 2015 2014 Accrued Product Warranty 2017 2016 (Restated) (Restated) Balance at beginning of year $ 10,200 $ 4,429 $ 2,428 $ 1,274 Current year provision 5,405 5,716 2,953 1,348 Acquisitions — — 963 1,600 Changes in estimates for preexisting warranties * — 1,894 — — Payments made during the period (2,977 ) (1,839 ) (1,915 ) (1,794 ) Balance at end of year $ 12,628 $ 10,200 $ 4,429 $ 2,428 * Change in estimates for pre-existing warranties reflect changes in the Company’s estimate of warranty costs for products sold in prior periods. Such adjustments typically occur when claims experience deviates from historic and expected trends. The Company’s warranty liability is generally affected by failure rates, repair costs and the timing of failures. Future events and circumstances related to these factors could materially change the estimates and require adjustments to the warranty liability. In addition, new product launches require a greater use of judgment in developing estimates until historical experience becomes available. In 2016, the Company recorded charges for adjustments for changes in estimat

Restatement of Previously Issue

Restatement of Previously Issued Consolidated Financial Statements	12 Months Ended
	Dec. 31, 2017
Accounting Changes and Error Corrections [Abstract]
Restatement of Previously Issued Consolidated Financial Statements	Restatement of Previously Issued Consolidated Financial Statements The Company has restated its previously reported consolidated financial statements for the years ended December 31, 2015 and 2014. The restatement adjustments resulted in a cumulative net reduction to stockholders’ equity of $21.4 million and $4.3 million as of December 31, 2015 and 2014, respectively, and a reduction in previously reported net income by $17.2 million and $2.2 million for the years ended December 31, 2015 and 2014, respectively. The Company has also restated the December 31, 2013 retained earnings balance to recognize corrected items discussed below that relate to prior periods. Except as otherwise specified, all information presented in the consolidated financial statements and the related notes include all such restatements. Summary of Restatement Items During the Company's comprehensive internal review of its accounting practices as well as its previously issued consolidated financial statements, the Company identified the following categories which required restatement or reclassification and were comprised of a number of related adjustments that have been aggregated for disclosure purposes: The following table sets forth the effects of the restatement adjustments on revenue and pretax income (loss) in the Consolidated Statements of Operations for the years ended December 31, 2015 and 2014. Due to the substantial number of restatement adjustments, each of the restatement categories listed in the table below may represent multiple related adjustments that have been aggregated for disclosure purposes. (in thousands) For the Year Ended December 31, 2015 2014 Net Sales Income (Loss) Before Income Taxes Net Sales Income (Loss) Before Income Taxes Previously reported $ 389,446 $ 13,890 $ 347,995 $ 34,539 Restatement adjustments: Revenue recognition adjustments (27,059 ) (9,215 ) (415 ) (2,700 ) Product development cost — (1,001 ) — (2,397 ) Inventory valuation — (1,069 ) — 38 Impairment of long-lived assets — (11,733 ) — (310 ) Product warranty — (2,484 ) — 591 Accrued liabilities — (1,106 ) — 591 Purchase accounting — — — (845 ) Equity investment — 125 — (286 ) Net restatement adjustments (27,059 ) (26,483 ) (415 ) (5,318 ) Restated $ 362,387 $ (12,593 ) $ 347,580 $ 29,221 Revenue Recognition Adjustments The Company did not have effective internal controls to ensure that all relevant supporting documentation related to information impacting revenue recognition was communicated and/or factored into the evaluation and determination of the accounting for revenue recognition. The Company reevaluated the application and conclusion of revenue recognition requirements on a significant number of transactions during the restatement periods. Procedures included reviewing supporting documentation as well as inquiry and forensic searches of emails and other communications. Based on the procedures performed, the Company concluded that there were numerous errors related to previous revenue recognition, including timing, amounts and classification of revenue recognized. These errors were generally related to the failure to meet all revenue recognition criteria, or, in some instances, there was insufficient supporting documentation for the original conclusions. In addition, there were instances in which additional information or side agreements were identified that contradicted the Company’s original accounting conclusions. The Company recorded adjustments to reduce revenue by $27.1 million and $0.4 million in 2015 and 2014, respectively. The adjustments resulted in net decreases to income (loss) before taxes of $9.2 million and $2.7 million in 2015 and 2014, respectively. The adjustments included the impact of correcting the Company’s revenue recognition for certain transactions in which revenue was previously recognized for undelivered products (“bill and hold transactions”). The Company determined that the transactions did not satisfy revenue recognition requirements for bill and hold transactions. For transactions with a certain customer, the Company originally recognized revenue on a net basis. It was determined that the associated revenue should have been recognized on a gross basis, as the Company was the primary obligor in the arrangements. The adjustments to correct the presentation resulted in increases of revenue and cost of sales of $6.5 million and $7.9 million in 2015 and 2014, respectively. Product Development Costs The Company previously capitalized certain product development costs. The costs included R&D and engineering costs and emission certification costs. The Company concluded that these costs did not meet the applicable criteria for capitalization and should have been expensed as incurred, and as a result it recorded net adjustments of $1.0 million and $2.4 million in 2015 and 2014, respectively, to expense the costs in the proper periods. Inventory Valuation The Company did not have appropriate processes to evaluate and estimate the Company’s reserves for excess and obsolete inventory at lower of cost or market. It was concluded that the previous process was based on unsupportable general assumptions that did not appropriately reflect the expected future utilization of existing inventory on hand, considering the effects of known changes in the business or business outlook. The Company subsequently developed a robust review process that identifies inventory items that may be potentially obsolete, damaged or in excess of market demand. Underlying assumptions in the refined process were developed based on current and historical consumption data, and reserve estimates were established based on those assumptions and other relevant factors. As a result, the Company recognized a charge of $1.1 million to increase the Company’s inventory valuation reserves in 2015. In addition, it was determined that there were errors in the determination of the Company’s finished goods inventory valuation related to the capitalization of overhead costs. As a result, the Company recorded an immaterial adjustment to increase inventory and a corresponding benefit in 2014. Impairment of Long-Lived Assets The Company historically performed its annual goodwill impairment assessment based on one reporting unit, which represented the Company as a whole. It was determined that subsequent to the acquisition of 3PI in 2014, the Company should have been performing separate goodwill impairment assessments for the 3PI reporting unit. During the Company’s 2015 annual goodwill impairment assessment for the 3PI reporting unit, it was determined that the goodwill was impaired, and a charge of $11.6 million was recognized. It was also determined that the Company did not have adequate internal controls to identify and evaluate potential impairments of long-lived assets, including the identification and write-offs of abandoned capital projects. It was determined that certain capital projects were abandoned during the impacted periods and that the Company should have recognized impairment charges of $0.1 million and $0.3 million in 2015 and 2014, respectively. Product Warranty The Company’s process to estimate its product warranty accrual was not designed to sufficiently factor in actual warranty claims experience. In addition, the model was not designed to adequately address the impacts of new-product offerings, with different warranty periods and risk profiles. With the introduction of engines that the Company fully manufactured as well as the introduction of engines supplied to the transportation market in 2015, the Company’s warranty costs have increased significantly, and there has also been increased volatility in warranty claims experience. The existing model did not adequately address these risks and deviations in experience from previous expectations. The Company's methodology used in its former warranty estimation model was determined to be incorrect; therefore, a more robust warranty estimation model was developed, and the Company recorded adjustments to recognize a charge of $2.5 million to increase the warranty accrual in 2015 and a benefit of $0.6 million to reduce the warranty accrual in 2014. Accrued Liabilities Certain transactions had been recorded to the wrong accounts, in the wrong periods, or could not be supported. Some accounts were not reconciled or had been classified inconsistently for reporting purposes. Certain estimate-based accruals, such as medical accruals, workers' compensation accruals, credit memo reserves and freight accruals, were not sufficiently documented and/or supportable. Various corrections and reclassifications were required to report balances at the correct amounts, in the correct periods or within the correct financial statement captions. Purchase Accounting The Company identified errors in the previous accounting for certain business acquisitions in 2015 and 2014, primarily related to the Company’s acquisition of 3PI. A measurement period adjustment recorded in 2014 to increase the opening balance of accrued warranties was determined to be an error. The adjustment was made to accrue for costs incurred subsequent to the acquisition of 3PI and anticipated future costs associated with out-of-policy warranty claims. Prior to the acquisition, 3PI did not historically incur costs associated with out-of-policy warranty claims. It was determined that the charges represented period costs, as they were reflective of post-acquisition management decisions and did not represent an assumed obligation as of the acquisition date. As a result, $0.8 million of warranty charges were recognized in 2014, and the related goodwill was decreased by the same amount. In addition, it was concluded that the initial fair values of certain long-lived assets in the 3PI acquisition were not properly stated as the assets were impaired. As a result, the Company decreased the value of long-lived assets and increased goodwill by $0.7 million . Equity Investment The Company had an investment in an unconsolidated entity that was previously accounted for under the cost method. The Company’s ownership interest was approximately 9% , and it maintained two positions on the unconsolidated entity's five -member board. Based on the Company’s ownership percentage and board positions, it was concluded that the Company had significant influence over the operations of the unconsolidated entity, and, accordingly, it should have been accounted for under the equity method. Under the equity method, the Company’s initial investment should have been recorded at cost, with the carrying amount adjusted to recognize the Company’s share of the unconsolidated entity's earnings or losses. Consolidated Statements of Operations Impact The following table presents the effect of the restatement adjustments and reclassifications on the Consolidated Statement of Operations for 2015: (in thousands, except for per share data) Year Ended December 31, 2015 Previously Reported Restatement Adjustments and Reclassifications Restated Net sales $ 389,446 $ (27,059 ) $ 362,387 Cost of sales 326,612 (15,464 ) 311,148 Gross profit 62,834 (11,595 ) 51,239 Operating expenses: Research, development and engineering expenses 21,681 1,893 23,574 Selling, general and administrative expenses 27,376 1,461 28,837 Asset impairment charge — 11,686 11,686 Amortization of intangible assets 4,582 — 4,582 Change in fair value of contingent consideration — (23 ) — (23 ) Total operating expenses 53,639 15,017 68,656 Operating income (loss) 9,195 (26,612 ) (17,417 ) Other (income) expense: Interest expense 4,327 (7 ) 4,320 Contingent consideration 48 (48 ) — Gain from change in fair value of warrants (9,299 ) (1 ) (9,300 ) Loss on debt extinguishment and modifications — 12 12 Other expense, net 229 (85 ) 144 Total other income (4,695 ) (129 ) (4,824 ) Income (loss) before income taxes 13,890 (26,483 ) (12,593 ) Income tax benefit (388 ) (9,314 ) (9,702 ) Net income (loss) $ 14,278 $ (17,169 ) $ (2,891 ) Weighted-average common shares outstanding: Basic 10,808 — 10,808 Diluted 11,074 (83 ) 10,991 Earnings (loss) per common share: Basic $ 1.32 $ (1.59 ) $ (0.27 ) Diluted $ 0.45 $ (1.56 ) $ (1.11 ) The following table presents the effect of the restatement adjustments and reclassifications on the Consolidated Statement of Operations for 2014: (in thousands, except for per share data) Year Ended December 31, 2014 Previously Reported Restatement Adjustments and Reclassifications Restated Net sales $ 347,995 $ (415 ) $ 347,580 Cost of sales 280,950 2,590 283,540 Gross profit 67,045 (3,005 ) 64,040 Operating expenses: Research, development and engineering expenses 16,900 2,405 19,305 Selling, general and administrative expenses 23,088 54 23,142 Asset impairment charge — 310 310 Amortization of intangible assets 1,013 — 1,013 Change in fair value of contingent consideration — (3,840 ) (3,840 ) Total operating expenses 41,001 (1,071 ) 39,930 Operating income 26,044 (1,934 ) 24,110 Other expense (income): Interest expense 1,331 11 1,342 Contingent consideration (3,840 ) 3,840 — Gain from change in fair value of warrants (6,169 ) (1 ) (6,170 ) Other expense (income), net 183 (466 ) (283 ) Total other income (8,495 ) 3,384 (5,111 ) Income before income taxes 34,539 (5,318 ) 29,221 Income tax expense 10,813 (3,069 ) 7,744 Net income $ 23,726 $ (2,249 ) $ 21,477 Weighted-average common shares outstanding: Basic 10,707 (2 ) 10,705 Diluted 11,132 (1 ) 11,131 Earnings (loss) per common share: Basic $ 2.22 $ (0.21 ) $ 2.01 Diluted $ 2.13 $ (0.75 ) $ 1.38 Consolidated Balance Sheets Impact The following table sets forth the effects of the restatement adjustments and reclassifications adjustments on the Company's Consolidated Balance Sheet as of December 31, 2015: (in thousands) As of December 31, 2015 Previously Reported Restatement Adjustments and Reclassifications Restated ASSETS Current assets Cash and cash equivalents $ 8,445 $ — $ 8,445 Accounts receivable, net 104,365 (33,833 ) 70,532 Income tax receivable 5,230 35 5,265 Inventories, net 130,347 31,748 162,095 Prepaid expenses and other current assets 4,288 (1,585 ) 2,703 Total current assets 252,675 (3,635 ) 249,040 Property, plant and equipment, net 26,001 (3,192 ) 22,809 Intangible assets, net 31,745 — 31,745 Goodwill 41,466 (11,631 ) 29,835 Deferred income taxes 819 16,838 17,657 Other noncurrent assets 7,230 (4,479 ) 2,751 TOTAL ASSETS $ 359,936 $ (6,099 ) $ 353,837 LIABILITIES AND STOCKHOLDERS’ EQUITY Current liabilities Accounts payable $ 76,078 $ 3,745 $ 79,823 Contingent consideration 8,788 (513 ) 8,275 Other accrued liabilities 14,396 3,450 17,846 Total current liabilities 99,262 6,682 105,944 Revolving line of credit 97,299 — 97,299 Warrants 1,482 — 1,482 Long-term debt, less current maturities, net 53,820 (15 ) 53,805 Other noncurrent liabilities 1,776 8,658 10,434 TOTAL LIABILITIES $ 253,639 $ 15,325 $ 268,964 STOCKHOLDERS’ EQUITY Preferred stock $ — $ — $ — Common stock 12 (1 ) 11 Additional paid-in capital 75,179 8,198 83,377 Retained earnings 35,356 (22,419 ) 12,937 Treasury stock, at cost (4,250 ) (7,202 ) (11,452 ) TOTAL STOCKHOLDERS’ EQUITY 106,297 (21,424 ) 84,873 TOTAL LIABILITIES AND STOCKHOLDERS’ EQUITY $ 359,936 $ (6,099 ) $ 353,837 The following table sets forth the effects of the restatement adjustments and reclassifications on the Company's Consolidated Balance Sheet as of December 31, 2014: (in thousands) As of December 31, 2014 Previously Reported Restatement Adjustments and Reclassifications Restated ASSETS Current assets Cash and cash equivalents $ 6,561 $ — $ 6,561 Accounts receivable, net 81,740 (5,474 ) 76,266 Inventories, net 93,903 12,347 106,250 Prepaid expenses and other current assets 4,801 39 4,840 Deferred income taxes 3,998 4,554 8,552 Total current assets 191,003 11,466 202,469 Property, plant and equipment, net 20,892 (2,938 ) 17,954 Intangible assets, net 21,392 (200 ) 21,192 Goodwill 23,546 (132 ) 23,414 Deferred income tax asset — 13 13 Other noncurrent assets 5,804 (3,901 ) 1,903 TOTAL ASSETS $ 262,637 $ 4,308 $ 266,945 LIABILITIES AND STOCKHOLDERS’ EQUITY Current liabilities Accounts payable $ 60,877 $ 6,836 $ 67,713 Current maturities of long-term debt 1,667 — 1,667 Other accrued liabilities 13,504 4,678 18,182 Total current liabilities 76,048 11,514 87,562 Revolving line of credit 78,030 — 78,030 Deferred income taxes 3,241 (3,241 ) — Warrants 11,036 — 11,036 Long-term debt, less current maturities, net 2,361 — 2,361 Other noncurrent liabilities 1,122 351 1,473 TOTAL LIABILITIES $ 171,838 $ 8,624 $ 180,462 STOCKHOLDERS’ EQUITY Preferred stock $ — $ — $ — Common stock 12 (1 ) 11 Additional paid-in capital 73,959 7,787 81,746 Retained earnings 21,078 (5,250 ) 15,828 Treasury stock, at cost (4,250 ) (6,852 ) (11,102 ) TOTAL STOCKHOLDERS’ EQUITY 90,799 (4,316 ) 86,483 TOTAL LIABILITIES AND STOCKHOLDERS’ EQUITY $ 262,637 $ 4,308 $ 266,945 Consolidated Statements of Changes in Stockholders’ Equity Impact The following table sets forth the effect of the restatement adjustments on the components of total stockholders, equity as of December 31, 2013: (in thousands) As of December 31, 2013 Previously Reported Restatement Adjustments Restated Preferred stock $ — $ — $ — Common Stock 11 — 11 Additional paid-in capital 57,308 4,622 61,930 Accumulated deficit (2,649 ) (3,079 ) (5,728 ) Treasury stock, at cost (4,250 ) (4,435 ) (8,685 ) Total stockholders' equity $ 50,421 $ (2,891 ) $ 47,530 The following table summarizes the effects of the restatement on the Company's Consolidated Statements of Changes in Stockholders’ Equity as of December 31, 2015 and 2014: (in thousands) Year Ended December 31, 2015 2014 Stockholders' equity, as previously reported $ 106,297 $ 90,799 Effect of restatement adjustments on net income/retained earnings (21,424 ) (4,316 ) Stockholders' equity, restated $ 84,873 $ 86,483 Consolidated Statements of Cash Flows Impact The following table includes comparison of selected previously reported and restated information from the Company's Consolidated Statements of Cash Flows for 2015 and 2014: (in thousands) For the Year Ended December 31, 2015 2014 Previously Reported Restated Previously Reported Restated Net cash used in operating activities $ (23,049 ) $ (22,815 ) $ (15,685 ) $ (15,094 ) Net cash used in investing activities (43,570 ) (43,805 ) (51,713 ) (52,322 ) Net cash provided by financing activities 68,503 68,504 67,653 67,671 Increase in cash 1,884 1,884 255 255 Cash at beginning of year 6,561 6,561 6,306 6,306 Cash at end of year $ 8,445 $ 8,445 $ 6,561 $ 6,561 Pre-2014 Restatement Adjustments Retained earnings as of December 31, 2013 were adjusted to correct the cumulative effect of errors in 2013 and prior periods. The errors, on a pretax basis, primarily related to the accounting treatment for capitalized product development costs that resulted in a charge of $3.6 million , increase in inventory valuation reserve of $1.5 million , accrued liability benefit of $0.3 million and equity investment benefit of $0.3 million , as described above. Under the provisions of the Company’s incentive compensation plan (the 2012 Plan), new awards were to be issued from the Company’s available treasury stock. The Company previously accounted for the 2012 Plan related stock issuances, net of shares used to satisfy tax withholdings, as new-share issuances. Treasury stock has been adjusted to reflect the issuance of the shares from treasury stock as well as the effect of the tax withholdings. In addition, activity in subsequent periods was restated to reflect the proper accounting treatment for similar transactions. The following table sets forth the effect of the restatement adjustments on the components of total stockholders' equity as of December 31, 2013: (in thousands) As of December 31, 2013 Stockholders' Equity Previously Reported Restatement Adjustments Restated Common stock $ 11 $ — $ 11 Additional paid-in capital 57,308 4,622 61,930 Accumulated deficit (2,648 ) (3,079 ) (5,649 ) Treasury stock, at cost (4,250 ) (4,435 ) (8,685 ) Total $ 50,421 $ (2,891 ) $ 47,607

Weichai Transactions

Weichai Transactions	12 Months Ended
	Dec. 31, 2017
Equity [Abstract]
Weichai Transactions	Weichai Transactions In March 2017, the Company and Weichai executed the SPA in which the Company issued stock and a warrant to Weichai for aggregate proceeds of $60.0 million , comprised of: • 2,728,752 shares of Common Stock; • 2,385,624 shares of Series B Redeemable Convertible Preferred Stock (“Series B Convertible Preferred Stock”) convertible on a two -for-one basis into 4,771,248 shares of Common Stock; and • The Weichai Warrant was exercisable for any number of additional shares of Common Stock such that Weichai, upon exercise, would hold 51% of the Common Stock then outstanding (on a fully-diluted as-converted basis). The Weichai Warrant also included an option to be exercised for Series B Convertible Preferred Stock upon approval of the Company's stockholders. The Company used proceeds from the sale of the above securities pursuant to the SPA and borrowings under the Wells Fargo Credit Agreement to pay off the outstanding TPG Term Loan (the “TPG Term Loan”) with TPG Specialty Lending, Inc. (“TPG”), discussed in Note 7. Debt . In August 2017, Gary S. Winemaster, former Chairman of the Board, Chief Executive Officer and President and nonexecutive Chief Strategy Officer, separately sold 200,000 additional shares to Weichai. Series B Redeemable Convertible Preferred Stock The Series B Convertible Preferred Stock was automatically convertible into Common Stock upon stockholder approval, as defined in the SPA. Commencing on September 30, 2017, Weichai was entitled to cumulative dividends at a stated rate of 10% per share, payable quarterly upon declaration by the Board, or as a liquidation preference for the Series B Convertible Preferred Stock. Any unpaid and deferred cash dividends would be deemed canceled and null upon conversion of the Series B Convertible Preferred Stock. In the event of liquidation, dissolution or winding-up of the Company, the holders of the Series B Convertible Preferred Stock would have been entitled to receive out of the assets of the Company available for distribution to stockholders of the Company, before any distributions on the Common Stock or any other junior stock, an amount equal to the greater of the liquidation preference ( $16.00 per share), plus accrued and unpaid dividends, or the amount that would otherwise be payable on an as-converted basis assuming the conversion of the Series B Convertible Preferred Stock into Common Stock. The Series B Convertible Preferred Stock also included a $23.1 million contingent beneficial conversion feature (“BCF”) that was considered to be “in the money” and “contingently beneficial” to Weichai, the warrant holder, upon the actual exercise of the Weichai Warrant, at Weichai's option at the commitment date, March 31, 2017, as the Company's stock price was greater than the conversion price at the commitment date. The Series B Convertible Preferred Stock and the Common Stock were assigned value based on their relative fair values after reducing the net proceeds from the Weichai transaction by the fair value of the Weichai Warrant, as required by accounting guidance. The resulting discount on the Series B Convertible Preferred Stock was accreted, with the remaining unaccreted amount included in the deemed dividend discussed below under “Deemed Dividend and Beneficial Conversion Feature .” In November 2017, the Company entered into a Securities Exchange Agreement (the “Exchange Agreement”) with Weichai that resulted in conversion of the 2,385,624 shares of Series B Convertible Preferred Stock into 4,771,248 shares of Common Stock. Weichai Warrant The Weichai Warrant was exercisable for a ninety ( 90 ) day period from September 30, 2018 to December 31, 2018 at a price per share of Common Stock equal to 85% of the Volume-Weighted Average Price (“VWAP”) during the 20 -day trading period immediately preceding the warrant exercise date or at a price per share of Common Stock equal to 50% of such preceding VWAP if the Company was delisted from NASDAQ as of September 30, 2018. The Weichai Warrant exercise price was subject to further reduction pursuant to a formula that provided for such adjustment in case the Company’s 2017 adjusted earnings before interest expense, income taxes, depreciation and amortization (“EBITDA”) (as defined within the SPA) were less than $22.0 million , or its net book value per share as of December 31, 2016 was less than $8.00 , provided that the aggregate amount of such downward adjustments would not exceed $15.0 million . The Exchange Agreement executed on November 30, 2017 amended the Weichai Warrant (the “Restated Warrant”) in addition to converting the Series B Convertible Preferred Stock to Common Stock as noted above. Under the Exchange Agreement, the Restated Warrant (i) was exercisable for Common Stock without obtaining stockholder approval, (ii) was no longer exercisable for Series B Convertible Preferred Stock and (iii) permitted the Company to accelerate the exercise of the Restated Warrant prior to September 30, 2018, to the extent that the Company required additional financing for any reason. In September 2018, the Weichai Warrant was amended under terms of a second amended and restated warrant (“Amended and Restated Warrant”) to defer its exercise date to a 90 -day period commencing April 1, 2019, at a price per share of the Company's Common Stock equal to the lesser of (i) 50% of the VWAP during the 20 consecutive trading day period preceding October 1, 2018 and (ii) 50% of the VWAP during the 20 consecutive trading day period preceding the date of exercise, subject to an adjustment that could reduce the exercise price by up to $15.0 million . In the event that the adjustment exceeded the exercise price, the excess would be due to the warrant holder. On April 23, 2019, Weichai exercised the Weichai Warrant resulting in the Company issuing 4,049,759 shares of the Company’s Common Stock and Weichai becoming the owner of 51.5% of the outstanding shares of the Company's Common Stock. The exercise proceeds for the warrants of $1.6 million were based on 50% of the VWAP during the 20 consecutive trading day period preceding April 23, 2019 and $15.0 million reduction in the exercise price described above. Valuation and Accounting for Issuance and Conversion to Common Stock, Series B Convertible Preferred Stock (and Related Beneficial Conversion Feature) and Weichai Warrant Detachable warrants issued in a bundled transaction with debt and equity offerings should be accounted for separately. If the warrants are classified as a liability recorded at fair value, then the total proceeds from the transaction are first allocated to the warrants based on their fair value, and residual proceeds are allocated to the remaining instruments based on their relative fair value. The Weichai Warrant is a freestanding derivative financial instrument that is not indexed solely to the Company's Common Stock due to the Weichai Warrant's exercise terms. Therefore, the Weichai Warrant is presented at fair value in the Company's Consolidated Balance Sheets in “Warrants” for $20.7 million at March 31, 2017 and $24.7 million at December 31, 2017. Changes in fair value of a loss of $4.0 million are reported in “Loss (gain) from change in fair value of warrants” in the Company's 2017 Consolidated Statement of Operations. See Note 8. Fair Value of Financial Instruments for additional details and assumptions used in valuing the Weichai Warrant, as well as 2017 fair value adjustments. The carrying values of the Common Stock and the Series B Convertible Preferred Stock were determined based on their relative fair values to the $39.3 million in aggregate remaining proceeds: $14.3 million was allocated to Common Stock and $25.0 million was allocated to the Series B Convertible Preferred Stock. Deemed Dividend and Beneficial Conversion Feature The difference between the stated proceeds related to the Common Stock and the Series B Convertible Preferred Stock of $38.7 million , pursuant to the SPA, and the net proceeds allocated to the Series B Convertible Preferred Stock based on relative fair value of $24.6 million (net of $0.4 million in transaction costs), is a discount of $14.1 million related to the Series B Convertible Preferred Stock, which was fully accreted onto the Consolidated Balance Sheet as part of the deemed dividend of $37.8 million ; which was recorded in “Additional paid-in capital”, as the Company had no retained earnings from the issuance date on March 31, 2017 until November 30, 2017, the date the Series B Convertible Preferred Stock was converted into Common Stock. The remaining portion of the deemed dividend was comprised of the $23.1 million BCF, which was recorded on the conversion date. Additionally, the Company recorded the exercise of the conversion option by reclassifying the $62.9 million carrying value of the Series B Convertible Preferred Stock to Common Stock, par value of $0.001 per share, with the remainder to “Additional paid-in capital.” Deemed dividends on Series B Convertible Preferred Stock were considered for calculations of earnings (loss) per share on Common Stock in 2017. See Note 14. Earnings Per Share . The Series B Convertible Preferred Stock also included a nondetachable contingent BCF that was considered to be “in the money” and “contingently beneficial” to Weichai, the warrant holder, upon the actual exercise of the warrant, at Weichai's option at the commitment date, March 31, 2017, as the Company's stock price was greater than the conversion price at the commitment date. The contingent BCF was recognized when the Series B Convertible Preferred Stock was converted into Common Stock. The carrying value for the contingent BCF was determined to be $23.1 million , based on conversion of 4,771,248 shares and a per-share value of $4.85 . The contingent BCF was included in the amount of deemed dividend on the Series B Convertible Preferred Stock when converted on November 30, 2017. Weichai Collaboration Arrangement The Company and Weichai executed a strategic collaboration agreement (the “Collaboration Agreement”) on March 20, 2017, in order to achieve their respective strategic objectives and enhance the strategic cooperation alliance to share experiences, expertise and resources. Among other things, the collaboration arrangement established a joint steering committee, permitted Weichai to second a limited number of certain technical, marketing, sales, procurement and finance personnel to work at the Company and established several collaborations, related to stationary natural-gas applications and Weichai Diesel Engines. The collaboration arrangement provided for the steering committee to create various sub-committees with operating roles and otherwise governs the treatment of intellectual property of parties prior to the collaboration and the intellectual property developed during the collaboration. The collaboration arrangement has a term of three years . The Company evaluates whether an arrangement is a collaborative arrangement at its inception based on the facts and circumstances specific to the arrangement. The Company also reevaluates whether an arrangement qualifies or continues to qualify as a collaborative arrangement whenever there is a change in either the roles of the participants or the participants’ exposure to significant risks and rewards dependent on the ultimate commercial success of the endeavor. For those collaborative arrangements, where it is determined that the Company is the principal participant, costs incurred and revenue generated from third parties are recorded on a gross basis in the financial statements. As of December 31, 2017, sales and purchases among the parties under the arrangement have been insignificant. Stockholders' Equity Common and Treasury Stock The changes in shares of Common and Treasury Stock were as follows: (in thousands) Common Shares Originally Issued Treasury Stock Shares Common Shares Outstanding Balance as of December 31, 2013 (Restated) 11,299 777 10,522 Net shares issued for Stock awards — (100 ) 100 Warrants exercised 109 — 109 Balance as of December 31, 2014 (Restated) 11,408 677 10,731 Net shares issued for Stock awards — (17 ) 17 Warrants exercised 5 — 5 Balance as of December 31, 2015 (Restated) 11,413 660 10,753 Net shares issued for Stock awards — (15 ) 15 Warrants exercised 154 — 154 Balance as of December 31, 2016 11,567 645 10,922 Net shares issued for Stock awards — (11 ) 11 Shares issued to Weichai * 2,729 — 2,729 Shares converted from Series B Convertible Preferred Stock * 4,771 — 4,771 Balance as of December 31, 2017 19,067 634 18,433 * See Note 3. Weichai Transactions for additional information. Preferred Stock The Company is authorized to issue 5,000,000 shares of preferred stock, par value $0.001 per share. The preferred stock may be designated into one or more series as determined by the Board. As of December 31, 2017, the Board had authorized two series of preferred stock as discussed further herein. At December 31, 2017, 2016, 2015 and 2014, there were no shares of preferred stock outstanding. Series B Convertible Preferred Stock and Weichai Warrant In March 2017, the Company issued 2,385,624 shares of Series B Convertible Preferred Stock to Weichai that were converted into 4,771,248 shares of the Company’s Common Stock in November 2017. On April 23, 2019, Weichai exercised the Weichai Warrant resulting in the Company issuing 4,049,759 shares of the Company’s Common Stock and Weichai becoming the owner of 51.5% of the outstanding shares of the Company's Common Stock. See Note 3. Weichai Transactions for additional information. Private Placement Warrants In connection with a private placement in April 2011, investors in the private placement received Series A Convertible Preferred Stock, which subsequently converted to shares of Common Stock, and Private Placement Warrants, with a five -year term. The Private Placement Warrants represented the right to purchase a total of 750,002 shares of Common Stock at an exercise price of $13.00 per share, subject to adjustments. The Private Placement Warrants were accounted for as a liability with the effect of the change in fair value of the obligation being reflected in “Loss (gain) from change in fair value of warrants” in the Consolidated Statements of Operations. See Note 8. Fair Value of Financial Instruments for details describing the valuation approach for the Private Placement Warrants as well as the impact on the Consolidated Statements of Operations for any changes in the value of the Private Placement Warrants. During 2016, 2015 and 2014, portions of the Private Placement Warrants were exercised, resulting in the issuance of 153,916 shares, 5,000 shares and 109,585 shares of the Common Stock, respectively. The unexercised Private Placement Warrants totaling 128,341 shares expired in April 2016. As of December 31, 2015 and 2014, 282,257 shares and 287,257 shares of Common Stock, respectively, remained reserved for the exercise of the Private Placement Warrants.

Property, Plant and Equipment a

Property, Plant and Equipment and Leases	12 Months Ended
	Dec. 31, 2017
Property, Plant and Equipment [Abstract]
Property, Plant and Equipment and Leases	Property, Plant and Equipment, and Leases Property, plant and equipment by type were as follows: (in thousands) As of December 31, 2015 2014 Property, Plant and Equipment 2017 2016 (Restated) (Restated) Land $ — $ — $ 260 $ 260 Buildings — — 1,471 1,471 Leasehold improvements 6,320 6,199 6,450 3,333 Machinery and equipment 27,379 24,490 23,523 17,500 Construction in progress 2,036 2,084 2,466 3,566 Total property, plant and equipment, at cost 35,735 32,773 34,170 26,130 Accumulated depreciation (16,775 ) (12,646 ) (11,361 ) (8,176 ) Property, plant and equipment, net $ 18,960 $ 20,127 $ 22,809 $ 17,954 Property, plant and equipment in 2016 includes a noncash conversion of inventory of $1.1 million purchased prior to 2016. Leases The Company leases certain buildings and equipment under various non-cancelable operating leases and a capital lease. Rent expense under operating leases approximated $4.7 million , $5.2 million , $4.9 million and $3.6 million for 2017, 2016, 2015 and 2014, respectively. Rent expense is recorded on a straight-line basis over the period of the lease term. The Company recognized the capital lease obligation of $0.4 million and related leased equipment based on the present value of the minimum lease payments at lease inception. The future minimum lease payments due under operating and capital leases in effect, as amended and extended, as of December 31, 2017, were as follows: (in thousands) Operating Capital 2018 $ 4,341 $ 22 2019 4,136 21 2020 3,786 20 2021 3,482 20 2022 3,578 19 2023 and beyond 3,202 51 Total $ 22,525 $ 153 In July 2018, the Company entered into the first and second lease amendments for two industrial buildings located in Wood Dale, Illinois. The extended terms of the lease amendments are from August 1, 2018 through and including July 31, 2023. These buildings are used for manufacturing, warehousing and certain administrative functions. Total base rental payments over these extended periods are $9.4 million and are included in the future minimum lease payments above. In December 2018, the Company entered into a new lease agreement for an industrial building located in Hanover Park, Illinois. The terms of the lease are from January 1, 2019 through and including July 31, 2023. This building is used primarily for operations, storage and certain administrative functions. Total base rental payments over the life of the lease are $4.2 million , which are not included in the future minimum lease payments above .

Acquisitions

Acquisitions	12 Months Ended
	Dec. 31, 2017
Business Combinations [Abstract]
Acquisitions	Acquisitions The Company accounts for business combinations by recording assets acquired and liabilities assumed at their respective fair values. The excess of the acquisition consideration over the fair value of tangible and intangible assets acquired and liabilities assumed, if any, is then allocated to goodwill. The estimated fair values of assets acquired and liabilities assumed are based on the information that was available through the date of the most recent balance sheet and are provisional, until the Company has completed the required analysis of fair values to be assigned to the assets acquired and the liabilities assumed. The ultimate determination of fair values assigned to the assets acquired and the liabilities assumed requires management to make significant assumptions and estimates. The more significant assumptions include estimating future cash flows and developing appropriate discount rates. These estimates and assumptions of the fair-value allocation are subject to change upon the finalization of all valuation analyses. When required, valuations are prepared to determine the estimated fair values of trade receivables, inventory, machinery and equipment, intangible assets and liabilities assumed, including contingent consideration. Fair value measurements can be subjective, and the reasonable application of measurement principles may result in a range of alternative estimates using the same facts and circumstances. The final allocation could be materially different from the preliminary allocation recorded in the Company’s Consolidated Balance Sheet. The Company's consolidated financial statements include the assets, liabilities and operating results of each acquired business subsequent to the date of each respective acquisition. Acquisition Summary Powertrain Integration, LLC In May 2015, the Company entered into an Asset Purchase Agreement (“APA”) with Powertrain Integration, LLC (“Powertrain”) and its owners to acquire the assets of Powertrain. Powertrain provides on-road powertrain solutions, including systems, components and services for niche OEM automakers and fleets. Powertrain also specializes in alternative-fueled gasoline and diesel systems and offers design, engineering, testing and production capabilities to deliver one-stop vehicle integration. The acquisition of Powertrain provided the Company with an opportunity to establish and strengthen its relationships with key customers and solidified the Company’s transportation end market position, knowledge and experience. The transaction also positioned the Company as the only on-highway OEM integrator for General Motors Company (“GM”) powertrains. At closing, the Company paid cash of $20.9 million representing the initial cash consideration adjusted for estimated working capital. Subsequently, the Company recorded a $0.1 million favorable final working capital adjustment that reduced the net cash paid to $20.8 million . The purchase price was subject to further adjustments for assumed liabilities and contingent consideration consisting of the Base and Additional Earn-outs, as described in the APA. The contingent consideration attributable to the Base Earn-out was based upon the 2015 full-year net sales of Powertrain, with a maximum value of $8.0 million and the Additional Earn-out was defined as the Base Earn-out multiplied by the greater of (i) a 5.0% per annum rate or (ii) the rate of growth of the Company’s volume-weighted Common Stock price from the acquisition announcement to year-end. The aggregate fair value of the Base and Additional Earn-outs of $8.2 million was initially estimated using a Monte Carlo simulation model and was considered a Level 3 financial instrument, as the inputs to determine the fair value were unobservable. The initial fair value of the contingent consideration and cash paid at closing, along with the final working capital adjustment, resulted in a purchase price of $29.0 million . The contingent consideration is reflected within “Contingent Consideration” in the Company’s Consolidated Balance Sheet at December 31, 2015 with adjustments to the liability recognized within “Change in fair value of contingent consideration” in the Company’s Consolidated Statements of Operations. As of December 31, 2015, the Base and Additional Earn-outs were finalized based on the final inputs in the calculations. There were no material changes in the fair value of the contingent consideration during 2015, and, under the terms of the APA, the final amount was paid in cash during 2016. The following table summarizes the purchase price allocation of the fair value of assets acquired and liabilities assumed in the Powertrain acquisition: (in thousands) Purchase Price Allocation Purchase consideration: Initial cash paid at date of acquisition $ 20,873 Fair value of contingent consideration 8,200 Working capital adjustment (97 ) Total purchase consideration $ 28,976 Allocation of consideration to assets acquired and liabilities assumed: Accounts receivable $ 4,931 Inventories 1,890 Prepaid expenses and other current assets 23 Property, plant and equipment 314 Intangible assets 13,600 Goodwill 15,311 Other non-current assets 24 Current liabilities (7,117 ) Net assets acquired $ 28,976 During the restatement process, the Company identified a warranty accrual adjustment to Powertrain's opening balance sheet in the amount of $0.3 million . The table above, as presented, includes this restatement adjustment. See Note 2. Restatement of Previously Issued Consolidated Financial Statements for additional information. The intangible assets are amortized over their respective estimated useful lives as follows: (in thousands) Asset Amount Estimated Life Backlog $ 600 3 months Customer relationships 13,000 12 years Total intangible assets $ 13,600 The weighted-average useful life of the intangibles identified above is approximately 11.5 years , which approximates the period over which the Company expects to gain the estimated economic benefits. The fair value of backlog and customer relationships were derived using the multi-period excess earnings method, an income approach. The Company used several assumptions, including revenue and operating expense growth rates, customer attrition rates and discount rates. The multi-period excess earnings method is based on valuations involving significant unobservable inputs that were Level 3 inputs in the fair-value hierarchy. Goodwill primarily relates to geographic expansion of product sales, manufacturing and other synergies of the combined companies, including the value of the assembled workforce. Bi-Phase Technologies, LLC In May 2015, the Company acquired all of the membership interests in Bi-Phase Technologies, LLC (“Bi-Phase”), a Minnesota limited liability company and wholly-owned subsidiary of TPB, Inc., a Minnesota corporation. Bi-Phase was engaged in the design and manufacture of liquid propane electronic fuel-injection systems to allow for the conversion of vehicles from gasoline to propane fuel. Bi-Phase systems achieved EPA and CARB on-highway certification for certain engines. The Company uses the Bi-Phase fuel-injection system on propane school buses, trucks and tractors. The initial purchase price was $3.6 million in cash plus certain working capital adjustments, assumption of certain liabilities and Earn-out Payments as defined in the “Membership Interest Purchase Agreement” under which the transaction took place. Subsequently, the Company paid an additional $0.3 million representing the final working capital adjustment, for total cash consideration of $3.9 million before the contingent consideration. The Company also recorded a liability for the fair value of contingent consideration of $0.5 million , representing an estimate of the Earn-out Payments expected to be paid in connection with the Bi-Phase acquisition. This contingent consideration was based upon certain sales of Bi-Phase fuel systems over a period of three to five years. Accordingly, the aggregate purchase price was $4.4 million . Through December 31, 2017, the Company had paid an immaterial amount of additional consideration related to the Bi-Phase acquisition. The following table summarizes the purchase price allocation of the fair value of assets acquired and liabilities assumed in the Bi-Phase acquisition: (in thousands) Purchase Price Allocation Purchase consideration: Initial cash paid at date of acquisition $ 3,619 Fair value of contingent consideration 540 Working capital adjustment 266 Purchase price, net of cash acquired $ 4,425 Allocation of consideration to assets acquired and liabilities assumed: Accounts receivable $ 212 Inventories 2,103 Prepaid expenses and other current assets 166 Property, plant and equipment 113 Intangible assets 860 Goodwill 1,217 Current liabilities (246 ) Net assets acquired $ 4,425 The intangible assets are amortized over their respective estimated useful lives as follows: (in thousands) Asset Amount Estimated Life Developed technology $ 700 7 years Customer relationships 160 15 years Total intangible assets $ 860 The weighted-average useful life of the intangibles identified above is approximately 8.5 years , which approximates the period over which the Company expects to gain the estimated economic benefits. Goodwill primarily consists of geographic expansion of product sales, manufacturing and other synergies of the combined companies and the value of the assembled workforce. Buck’s Acquisition Company, LLC In March 2015, the Company acquired all of the membership interests in Buck’s Acquisition Company, LLC (“Buck’s”) from United Engines Powertrain, doing business as Buck’s Engines and United Holdings, LLC, for cash consideration of $9.7 million . Buck’s manufactured alternative-fueled engines for industrial markets and was formerly a product line of United Engines, LLC. Buck’s supplies a range of alternative-fueled engines that run on natural gas, propane and liquid propane gas fuels. Buck’s targets an extensive range of industrial applications, including irrigation, gas compression, oil production, industrial equipment, power generation, mobile equipment, wind turbines and re-power applications. The acquisition added the Buck’s customer base to the Company’s existing customer base and enabled the Company to take advantage of economies of scale to further expand its product offering in the alternative-fueled engine markets. The following table summarizes the purchase price allocation of the fair value of assets acquired and liabilities assumed in the Buck's acquisition: (in thousands) Purchase Price Allocation Purchase Consideration: Cash Consideration at date of acquisition $ 9,735 Allocation of consideration to assets acquired: Inventories $ 6,598 Property, plant and equipment 231 Intangible assets 1,380 Goodwill 1,526 Net assets acquired $ 9,735 The Company recorded an inventory step-up of $0.3 million to reflect inventory at its fair value as of the date of the acquisition. All of the step-up was amortized as a noncash charge to cost of goods sold during 2015, as all acquired inventory was sold. The intangible asset is amortized over its estimated useful life as follows: (in thousands) Asset Amount Estimated Life Customer relationships $ 1,380 10 years Goodwill primarily consists of geographic expansion of product sales, manufacturing and other synergies of the combined companies and the value of the assembled workforce. Professional Power Products, Inc. In April 2014, pursuant to a stock purchase agreement with Carl L. Trent and Kenneth C. Trent (collectively, the “Trents”) and CKT Holdings Inc., a Wisconsin corporation owned by the Trents, the Company acquired 3PI, a designer and manufacturer of large, custom engineered integrated electrical power generation systems serving the global diesel and natural-gas power generation markets, power generation systems and equipment for both standby and prime. 3PI also produces switchgear, control panels, load banks, mobile power trailers and UL tanks. 3PI’s products are used in a wide range of industries; including utilities, offshore oil and gas platforms, hospital systems, data centers, mining, transportation operations in remote locations, corporate and government buildings, and educational institutions. The acquisition extends the Company’s global reach, broadens the Company’s product offerings and customer base, and is expected to help accelerate growth and provide value-added power solutions fueled by diesel and natural-gas trends. The Company acquired all of the issued and outstanding stock of 3PI for an initial cash purchase price of $45.4 million , including cash acquired of $1.3 million . The Company also agreed to pay additional consideration, which consisted of (i) fixed consideration of 65,772 shares of the Company's Common Stock at a future date and (ii) variable contingent consideration of up to an additional 131,544 shares of the Company's Common Stock, based upon the final determination of 3PI's 2014 EBITDA. Including the fair value of this contingent consideration that was valued at $8.9 million at the date of acquisition, the total consideration, net of cash acquired, was valued at $53.0 million . (in thousands) Purchase Price Allocation (Restated) Purchase consideration: Initial cash paid at date of acquisition, net of acquired cash $ 44,122 Fair value of contingent consideration 3,840 Fair value of the fixed number of shares of Common Stock 5,060 Purchase considerations: $ 53,022 Allocation of consideration to assets acquired and liabilities assumed: Accounts receivable $ 3,989 Inventories 4,953 Prepaid expenses and other current assets 243 Property, plant and equipment 2,346 Intangible assets 23,300 Goodwill 23,414 Current liabilities (5,223 ) Net assets acquired $ 53,022 The Company also recorded an inventory step-up of $0.4 million to record inventory at fair value as of the date of the acquisition. All of the step-up was amortized as a noncash charge to “Cost of goods sold” during 2014, as the acquired inventory was sold. The fair value of the fixed number of shares of the Company's Common Stock was determined based on its stock price on the date of acquisition and was recognized as an increase of $4.4 million , net of tax, to “Additional paid-in capital.” The fair value of the variable portion of the contingent consideration was recorded as a liability, with changes in the fair value subsequently recognized within “Change in fair value of contingent consideration” in the Company’s Consolidated Statement of Operations. The fair value of the variable portion of the contingent consideration was estimated based on a Monte Carlo simulation model utilizing unobservable inputs and was considered a Level 3 financial instrument. The initial fair value of the variable portion was estimated to be $3.8 million . During 2014, due to a decrease in the fair value of the variable portion of the contingent consideration, the Company recognized income of $3.8 million . Subsequent to the acquisition of 3PI, the Company and the Trents were involved in a dispute involving multiple claims, and counterclaims. In June 2017, the parties settled the matter for $3.0 million in return for full and final mutual releases of all claims, including the cancellation of the issuance of the Company’s Common Stock related to the fixed consideration. In the second quarter of 2017, the Company reduced “Additional paid-in capital” by $0.7 million for the portion of the settlement related to the cancellation of the share issuance. See Note 10. Commitments and Contingencies for additional information. The intangible assets are amortized over their respective estimated useful lives, which approximate the period over which the Company expects to gain the estimated economic benefits as follows: (in thousands) Asset Amount Estimated Life Backlog $ 1,200 15 months Customer relationships 20,400 13 years Trade names and trademarks 1,700 13 years Total intangible assets $ 23,300 The weighted-average useful life of the intangibles identified above is approximately 12.4 years , which approximates the period over which the Company expects to gain the estimated economic benefits. The fair value of backlog, customer relationships, and trade names and trademarks were derived using the multi-period excess earnings method, an income approach, and based on valuations involving significant unobservable inputs that were Level 3 inputs in the fair-value hierarchy. The Company used several assumptions, including revenue and operating expense growth rates, customer attrition rates and discount rates. Goodwill primarily consists of geographic expansion of product sales, manufacturing and other synergies of the combined companies, and the value of the assembled workforce. The write-off of the variable contingent consideration and the difference in the book and tax basis of the fixed portion of the consideration resulted in a lower amount of goodwill that is deductible by the Company for income tax purposes. Accordingly, the Company recognized deferred income tax liabilities arising from these differences that amounted to $1.5 million . The $1.5 million was recognized in the Company’s income tax expense for the year ended December 31, 2014. The total amount of goodwill that is expected to be deductible for income tax purposes was $19.7 million at December 31, 2014. The total amount of goodwill was $14.5 million at December 31, 2017. Acquisition Financing The Powertrain and Bi-Phase acquisitions were funded by the proceeds received from the original issuance of the Unsecured Senior Notes on April 29, 2015. The Buck’s acquisition was financed through the revolving line of credit with Wells Fargo. To finance the 3PI acquisition, the Company entered into an amended and restated credit agreement with Wells Fargo on April 1, 2014, to increase its revolving line of credit and to secure a $5.0 million term loan. See Note 7. Debt for additional information of these obligations. Treatments for Income Tax Purposes The Company treated all of the above acquisitions as asset purchases for income tax purposes. Accordingly, the financial and income tax bases of the assets and liabilities acquired were considered to be the same at the acquisition dates; therefore, a provision for deferred income tax was not recorded in connection with the purchase price allocations. Any excess of the purchase price over the fair value of the net assets acquired is expected to be deductible for income tax purposes. Supplemental Pro-Forma Information (Unaudited) The following supplemental unaudited pro-forma information presents the combined results of operations of the Company and 3PI as though the acquisition of 3PI occurred on January 1, 2014. The Company also presents the combined results of operations of the Company and Powertrain as though the acquisition of Powertrain occurred on January 1, 2015. The Company did not include pro-forma results of operations for Bi-Phase and Buck’s, as the results are immaterial to the Company's Consolidated Statements of Operations. The pro-forma information is not necessarily indicative of the actual consolidated results had the 3PI acquisition occurred as of January 1, 2014, or had the Powertrain acquisition occurred as of January 1, 2015, or of future consolidated operating results. (in thousands, except per share amounts) For the Year Ended December 31, 2015 2014 Net sales $ 383,455 $ 352,760 Net income (580 ) 21,696 Earnings per common share, basic $ (0.05 ) $ 2.03 Earnings per common share, diluted $ (0.05 ) $ 1.95 The historical operating results of 3PI included in the 2014 pro-forma information above were adjusted to (i) exclude $3.5 million of non-recurring transaction-related expenses, (ii) reflect $0.8 million of amortization expense related to intangibles recorded in the acquisition purchase accounting, (iii) reflect $0.2 million in additional acquisition-related interest expense for the first three months of 2014 and (iv) reflect $0.4 million in tax-related benefits resulting from such expenses. Transaction Fees and Expenses The Company incurred transaction costs related to acquisition activities of $1.1 million and $0.8 million during 2015 and 2014, respectively, all of which were recognized as operating expenses and classified within “Selling, general and administrative expenses” in the Company’s Consolidated Statements of Operations.

Goodwill and Other Intangibles

Goodwill and Other Intangibles	12 Months Ended
	Dec. 31, 2017
Goodwill and Intangible Assets Disclosure [Abstract]
Goodwill and Other Intangibles	Goodwill and Other Intangibles Goodwill The carrying amounts for goodwill and changes in the carrying value were as follows: (in thousands) For the Year Ended December 31, 2015 2014 2017 2016 (Restated) (Restated) Balance at beginning of year, net $ 29,835 $ 29,835 $ 23,414 $ — Acquisitions — — 18,054 23,414 Impairment losses — — (11,633 ) — Balance at end of year, net $ 29,835 $ 29,835 $ 29,835 $ 23,414 Accumulated impairment losses $ (11,633 ) $ (11,633 ) $ — $ — During 2015, the Company’s 3PI reporting unit was impacted by depressed oil and gas prices and lower demand from existing customers, which contributed to continued sales and profitability reductions over historic experience and prior forecasts. In the fourth quarter of 2015, the Company performed its annual impairment assessment, utilizing the income approach, based on discounted cash flows derived from internal forecasts and the Company's specific risk premium. It was determined that the carrying value of the 3PI reporting unit, including goodwill, exceeded its fair value. As a result, the Company compared the implied fair value of the reporting unit’s goodwill with the carrying amount of that goodwill, which resulted in the recognition of an impairment charge of $11.6 million . See Note 2. Restatement of Previously Issued Consolidated Financial Statements for additional information. Other Intangible Assets Components of intangible assets are as follows: (in thousands, except weighted-average useful life) As of December 31, 2017 Weighted-Average Useful Life (in years) Gross Carrying Value Accumulated Amortization Net Book Value Customer relationships 10.0 $ 34,940 $ (14,915 ) $ 20,025 Developed technology 4.2 1,000 (434 ) 566 Trade names and trademarks 6.1 1,700 (800 ) 900 Total $ 37,640 $ (16,149 ) $ 21,491 (in thousands, except weighted-average useful life) As of December 31, 2016 Weighted-Average Useful Life (in years) Gross Carrying Value Accumulated Amortization Net Book Value Customer relationships 10.8 $ 34,940 $ (10,430 ) $ 24,510 Developed technology 8.3 700 (287 ) 413 Trade names and trademarks 6.8 1,700 (594 ) 1,106 Total $ 37,340 $ (11,311 ) $ 26,029 (in thousands, except weighted-average useful life) As of December 31, 2015 Weighted-Average Useful Life (in years) Gross Carrying Value Accumulated Amortization Net Book Value (Restated) (Restated) (Restated) Backlog $ 1,800 $ (1,800 ) $ — Customer relationships 11.5 34,940 (5,129 ) 29,811 Developed technology 8.2 700 (113 ) 587 Trade names and trademarks 7.5 1,700 (353 ) 1,347 Total $ 39,140 $ (7,395 ) $ 31,745 (in thousands, except weighted-average useful life) As of December 31, 2014 Weighted-Average Useful Life (in years) Gross Carrying Value Accumulated Amortization Net Book Value (Restated) (Restated) (Restated) Backlog 1.0 $ 1,200 $ (1,095 ) $ 105 Customer relationships 21.0 20,400 (926 ) 19,474 Trade names and trademarks 8.3 1,700 (87 ) 1,613 Total $ 23,300 $ (2,108 ) $ 21,192 Amortization expense was classified as follows in the Consolidated Statements of Operations: (in thousands) For the Year Ended December 31, 2015 2014 2017 2016 (Restated) (Restated) Cost of sales $ — $ — $ 705 $ 1,095 Operating expenses 4,838 5,716 4,582 1,013 Total $ 4,838 $ 5,716 $ 5,287 $ 2,108 Estimated future amortization expense for intangible assets as of December 31, 2017 is as follows: (in thousands) Year Ending December 31, Estimated Amortization 2018 $ 4,227 2019 3,698 2020 3,113 2021 2,594 2022 2,184 2023 and beyond 5,675 Total $ 21,491

Debt

Debt	12 Months Ended
	Dec. 31, 2017
Debt Disclosure [Abstract]
Debt	Debt The Company's outstanding debt consisted of the following: (in thousands) As of December 31, 2015 2014 Description of Debt 2017 2016 (Restated) (Restated) Short-Term Debt: Current portion of Wells Fargo Term Loan $ — $ — $ — $ 1,667 Current portion of TPG Term Loan — 750 — — Wells Fargo Revolving Credit Facility 37,055 12,774 — — Total Short-Term Debt $ 37,055 $ 13,524 $ — $ 1,667 Long-Term Debt: Senior Secured Credit Facility - Wells Fargo Revolving Credit Facility $ — $ — $ 97,299 $ 78,030 Wells Fargo Term Loan — — — 2,361 Unsecured Senior Notes 55,000 55,000 55,000 — TPG Term Loan — 70,650 — — Less Unamortized Debt Issuance Costs * (561 ) (15,258 ) (1,195 ) — Total Long-Term Debt $ 54,439 $ 110,392 $ 151,104 $ 80,391 * Unamortized financing costs and deferred fees on the Wells Fargo revolving credit facility are not presented in the above table as they are classified as “ Current Assets ” on the Consolidated Balance Sheets. Debt issuance costs incurred, including gross waiver fees (primarily paid to the lenders), were $0.9 million , $17.2 million , $1.5 million and $0.2 million in 2017, 2016, 2015 and 2014, respectively. The Company paid $7.8 million , $6.7 million , $3.3 million and $1.1 million in cash for interest in 2017, 2016, 2015 and 2014, respectively. The Company's debt includes restrictive covenants that, if not met, could lead to renegotiation of its revolving credit facility, notes and indentures, a requirement to repay the Company's borrowings and/or a significant increase in the cost of financing. These restrictive covenants may include, among other items, financial covenants pertaining to availability, permitted indebtedness, restrictions on dividends and various events of default. Certain events of default (including delinquent filing of annual and periodic reports with the SEC, failure to maintain EBITDA requirements, material weaknesses in the control environment and failure to disclose litigation) have occurred with respect to the Company's credit agreements. While waivers have been obtained or debt renegotiated with the respective lenders, in particular after March 31, 2017, absent such waivers, the debt would have been in breach of covenants. The Company and its subsidiaries pledged substantially all of their tangible and intangible assets, including inventory, receivables and fixed assets, as collateral under the Wells Fargo Credit Agreement. The schedule of remaining principal maturities of Long-Term Debt is as follows: (in thousands) Year Ending December 31, Maturities of Long-Term Debt 2018 $ — 2019 — 2020 55,000 Total $ 55,000 Subsequent to December 31, 2017, the Unsecured Senior Notes and the Wells Fargo Credit Agreement were amended. The maturity date of the Unsecured Senior Notes was extended to January 1, 2020 and the interest rate was increased effective October 1, 2018 from 6.50% to 8.50% per annum. The interest rate will decrease to 7.50% per annum upon filing this 2017 Form 10-K with the SEC. The maturity of the Wells Fargo revolving credit facility was extended to the earlier of March 31, 2021 or 60 days prior to the final maturity of the Unsecured Senior Notes (resulting in a current maturity date of November 2, 2019). Additionally, the facility will continue to bear interest at a per annum rate equal to 1% above the per annum rate applicable under the credit agreement until the Company has completed all filings required to be made with the SEC. Wells Fargo Credit Agreement On June 28, 2013, the Company entered into the Wells Fargo Credit Agreement. The Wells Fargo Credit Agreement enabled the Company to borrow under a revolving credit facility secured by substantially all of the Company's tangible and intangible assets, other than real property. The Wells Fargo Credit Agreement had an initial maturity date of June 28, 2018 and: • Provided an initial maximum $75.0 million revolving line of credit to the Company, with flexibility to increase up to $100.0 million ; • Bore interest at Wells Fargo’s prime rate plus a margin ranging from 0% to 0.50% per annum or at the London Interbank Offered Rate (“LIBOR”) plus a margin ranging from 1.50% to 2.00% per annum at the Company’s option; • Had an unused line fee of 0.25% ; • Required the Company to meet a minimum fixed charge coverage ratio of 1.0 to 1.0 and to report such coverage ratio if availability was below the greater of $9.4 million or 12.5% of the maximum revolver amount; • Limited borrowings to the lesser of the maximum revolving line of credit and the borrowing base, which is defined as a percentage of the Company’s eligible accounts receivable and inventory. Information regarding amounts borrowed under the Wells Fargo Credit Agreement includes the following: (in thousands, except interest rate) As of December 31, 2015 2014 Description 2017 2016 (Restated) (Restated) Average borrowings under Wells Fargo Revolving Credit Facility $ 26,662 $ 44,335 $ 96,390 $ 53,250 Average Interest Cost on Wells Fargo Revolving Credit Facility 6.85 % 2.75 % 1.96 % 2.36 % Accrued and unpaid interest $ 90 $ 24 $ 86 $ 105 LIBOR loan interest rate 4.51 % 2.71 % 1.84 % 1.66 % Wells Fargo Prime Rate (Base Rate) loan interest rate 6.00 % 4.25 % 3.50 % 3.25 % As of December 31, 2017, the Company had adjusted available borrowing capacity under the revolving line of credit of approximately $13 million . The Wells Fargo Credit Agreement was amended a number of times. The most significant changes are summarized in the table below: Amendment Date and Title Reason for Amendment Significant Changes to the Wells Fargo Credit Agreement April 1, 2014. Amended Wells Fargo Credit Agreement To finance acquisition of 3PI • Increased maximum borrowing under the under the revolving credit facility to $90.0 million; September 30, 2014 and February 11, 2015. Wells Fargo Credit Agreement II To increase capacity of Wells Fargo Credit Agreement • Increased maximum borrowing under the under the revolving credit facility to $100.0 million on September 30, 2014. April 29, 2015. Amended Wells Fargo Credit Agreement III To facilitate Issuance of the Unsecured Senior Notes • Accelerated maturity date to no earlier than December 31, 2016 and no later than January 31, 2018, to ensure that it matures prior to repayment of the Unsecured Senior Notes; June 28, 2016. Second Amended and Restated Credit Agreement (the “June 28, 2016 Agreement”) To facilitate issuance of TPG Term Loan • Decreased maximum borrowing under the revolving credit facility to $75.0 million from $125.0 million in response to issuance of TPG Term Loan; August 22, 2016. First Amendment and Waivers to the June 28, 2016 Agreement To consider implications of various events of default • Provided for certain waivers related to the failure to disclose litigation and the Company’s delay in filing its Form 10-Q for the period ended June 30, 2016; • Reduced borrowing base by $12.5 million to be reduced to $7.5 million upon filing the Form 10-Q for the period ended June 30, 2016. December 16, 2016. Waiver to June 28, 2016 Agreement To consider implications of various events of default • Provided for certain waivers for events of default due to the Company's failure to timely deliver the monthly financial statements and required certificates for the month ended October 31, 2016, provided that such documents were delivered by December 19, 2016. December 19, 2016. Second Amendment and Waivers to the June 28, 2016 Agreement To consider implications of various events of default • Made the $12.5 million borrowing base reserve permanent; • Provided for certain waivers related to the Company’s non-compliance with the TPG Agreement’s minimum trailing twelve months EBITDA maintenance covenant; • The Company paid an amendment fee of $0.1 million. February 10, 2017, effective as of February 6, 2017. Limited Waiver Agreement to the June 28, 2016 Agreement (“Limited Waiver”) To consider implications of various events of default • Provided waiver for various events of default including identified material weaknesses in internal control through February 28, 2017; • Wells Fargo reserved the right to increase the interest rate by 200 basis points (2%) effective January 27, 2017, though the interest rate was not increased; • Provided Wells Fargo with access to additional financial information including cash flow forecasts and budgets. February 28, 2017, effective as of February 6, 2017. First Amendment to Limited Waiver To refine provisions of Limited Waiver to June 28, 2016 Agreement • Established minimum financial metrics related to liquidity and cash which were required to be maintained through March 3, 2017; • Extended the Limited Waiver to March 3, 2017. March 9, 2017, effective as of February 6, 2017. Second Amendment to Limited Waiver To refine provisions of Limited Waiver to June 28, 2016 Agreement • Extended the Limited Waiver to March 10, 2017. March 31, 2017, effective as of February 7, 2017. Third Amendment to Limited Waiver To facilitate changes necessary due to Weichai SPA • Modified certain changes in control and other definitions to permit issuance of securities to Weichai and pay off TPG Term Loan; July 17, 2017. Fourth Amendment to the June 28, 2016 Agreement To facilitate changes to availability, commitment fee and interest rate terms • Increases available borrowing under the revolving credit facility to $52.5 million (maximum borrowing amount of $65.0 million less a reserve of $12.5 million); • Reduced the incremental interest rate by 100 basis points (1%) from 200 basis points (2%) until the Company’s 2016 audited financial statements have been provided. October 3, 2017. Consent and Fifth Amendment to the June 28, 2016 Agreement To facilitate an acquisition • Increased available borrowing under the revolving credit facility to $58.75 million (maximum borrowing amount of $65.0 million less a reserve of $6.25 million). March 29, 2018. Sixth Amendment and Waiver to the June 28, 2016 Agreement To consider implications of various events of default • Increased the maximum borrowing under the revolving credit facility to $75.0 million from $65.0 million; • Modified the reserve against the maximum borrowing under the revolving credit facility to the greater of $6.5 million and 10% of borrowing base, but no more than $7.5 million on or prior to September 30, 2018 and thereafter equal to $9.0 million; • Extended the maturity date of the facility to the earlier of March 31, 2021 or 60 days prior to the final maturity of the Unsecured Senior Notes, which were extended to January 1, 2020, resulting in a maturity date of November 2, 2019 on the Wells Fargo revolving credit facility. • The revolving credit facility will continue to bear interest at a per annum rate equal to 100 basis points (1%) above the per annum rate otherwise applicable under the credit agreement until the Company has completed all filings required to be made with the SEC; • The Company paid an amendment fee of $0.8 million. The Company evaluated modifications to all of its debt amendments between 2014 and 2017 according to FASB guidance . As a result of the aforementioned amendments, consents and waivers related to the Wells Fargo Credit Agreement, the Company accelerated the recognition of previously deferred debt issuance costs and third-party fees totaling $0.1 million and $0.1 million for the modifications in 2017 and 2016, respectively. Third-party fees were immaterial in 2015. In addition, new-lender fees totaled $0.7 million , $0.3 million and $0.1 million in 2017, 2016 and 2014, respectively, and were deferred and amortized through the anticipated maturity date of the Wells Fargo Credit Agreement. Lender-related fees were immaterial in 2015. The Wells Fargo revolving credit facility is presented as a “Current liability” on the Consolidated Balance Sheets as of December 31, 2017 and 2016, reflecting the provisions of the June 28, 2016 amendment which included a subjective acceleration clause and a lockbox arrangement that sweeps cash receipts to pay down the revolver balance, without requiring the Company's specific consent, and provides advances up to current limits to cover outlays. Prior to that amendment, the revolving line of credit was presented as a “Non-current liability.” The Company’s term loan, which bore interest at 4.67% per annum (LIBOR rate plus 4.50% margin), had $3.5 million outstanding at the time of repayment on April 29, 2015. Unsecured Senior Notes On April 29, 2015, the Company entered into an agreement with certain institutional investors for a private sale of its Unsecured Senior Notes for the aggregate amount of $55.0 million with an interest rate of 5.50% per annum. Concurrently, in connection with the issuance of the Unsecured Senior Notes, the Company entered into an indenture agreement (“Indenture”), by and among the Company and its subsidiaries as guarantors and the Bank of New York Mellon, as Trustee. The Company received net proceeds of $53.5 million after financing costs of $1.5 million . As discussed previously in Note 1. Summary of Significant Accounting Policies and Other Information , the Company has presented issuance costs associated with its Unsecured Senior Notes as a direct deduction from the carrying value of the obligation on its Consolidated Balance Sheets. The Unsecured Senior Notes are unsecured debt of the Company and are effectively subordinated to its existing and future secured debt, including the debt in connection with the Third Amended Wells Fargo Credit Agreement. The Unsecured Senior Notes originally had the following key terms: • Matures on May 1, 2018, provided that a mandatory offer to purchase must be made for all Unsecured Senior Notes at a purchase price of 100% of the principal amount, plus accrued and unpaid interest, in the event the Company does not certify certain financial metrics related to pro-forma EBITDA and EBITDA-to-fixed charges ratios prior to March 15, 2017 (the offer was eliminated by the Second Supplemental Indenture on April 1, 2016, see table below); • Accrues interest at 5.50% per annum, payable semiannually in arrears on May 1 and November 1 of each year beginning November 1, 2015; • Redeemable at the Company’s option, in whole or in part, at any time on or after May 1, 2016, together with accrued and unpaid interest to the date of redemption (expressed as percentages of the principal amount), at 101.0% plus a “make whole” premium as further defined in the Unsecured Senior Notes; • Redeemable by the holders in whole or in part upon a change in control at a purchase price of 101% of the principal amount, plus accrued and unpaid interest; • Contains restrictive covenants that, among other things, limit the ability of the Company and its subsidiaries to incur additional debt, prepay subordinated indebtedness, pay dividends or make other distributions on capital stock; and • Provides for customary events of default (subject in certain cases to customary grace and cure periods). The indenture was amended from time to time as follows: Amendment Date and Title Reason for Amendment Significant Changes to the Unsecured Senior Notes November 2, 2015. First Supplemental Indenture To add subsidiaries unconditional guarantee of the Unsecured Senior Notes • Added each guaranteeing subsidiary as a party to the Indenture on a joint and several basis. April 1, 2016. Second Supplemental Indenture To facilitate increase in indebtedness • Increased permitted indebtedness from $125.0 million to $145.0 million, with such amount reducing to $135.0 million, effective February 1, 2017; • Increased the interest rate from 5.50% to 6.50% per annum; • Eliminated special mandatory purchase offer requirement; • The Company paid a consent fee of $0.3 million. March 31, 2017. Third Supplemental Indenture To facilitate the changes necessary due to the Weichai SPA • Extended maturity date to January 1, 2019; • Amended certain provisions to permit the issuance of the securities to Weichai under the SPA, and provisions to permit ongoing transactions with an affiliate of Weichai under the Collaboration Arrangement; • Waived any defaults occurring prior to March 31, 2017 with respect to the failure to file periodic and annual reports; • Extended the deadline for the Company to file its delinquent SEC periodic and annual reports; • The Company paid a consent fee of $0.2 million and legal fees of $0.1 million. April 19, 2018. Fourth Supplemental Indenture To amend certain covenants and waive certain events of default • Extended the maturity date to January 1, 2020; • Waived defaults with respect to the failure to file with the Trustee and the SEC for 2015 through 2019; • Increased the interest rate from 6.50% to 8.50% per annum effective October 1, 2018. The interest rate decreases to 7.50% per annum upon filing this 2017 Form 10-K with the SEC; • The Company paid a consent fee of $0.3 million. As a result of the supplemental indenture amendments, charges of $0.1 million were incurred in 2017 related to legal fees and other third-party costs, which were expensed to “Loss on debt extinguishment and modifications” in the Consolidated Statement of Operations. Additional debt issuance costs of $0.2 million and $0.3 million incurred in 2017 and 2016, respectively, were deferred and amortized to Interest expense through the anticipated maturity date of the Unsecured Senior Notes. There were no fees incurred related to the amendments made in 2015. The Unsecured Senior Notes are presented as a “Non-current liability” on the Consolidated Balance Sheets. As of December 31, 2017, 2016 and 2015, the accrued, but unpaid, interest on the Unsecured Senior Notes was $0.6 million , $0.6 million and $0.5 million , respectively. TPG Term Loan On June 28, 2016, the Company entered into a $135.0 million senior secured credit facility, which consisted of a new $60.0 million TPG Term Loan and a $75.0 million revolving credit facility with Wells Fargo, as discussed in the Wells Fargo Credit Agreement section above. A related “Side Letter” was also executed at the time, in which the Company agreed to certain amounts as meeting certain borrowing limit calculations. The TPG Term Loan was executed with the following terms: • Bore interest at LIBOR plus 9.75% per annum (or 10.75% per annum at June 28, 2016) or at the Base Rate, as defined in the TPG Term Loan; • Required quarterly principal repayments of (i) $0.4 million , commencing September 30, 2017 and ending on June 30, 2018, and (ii) $0.8 million thereafter, with any remaining unpaid principal or interest due on the maturity date; • Permitted prepayment at any time after December 31, 2017; • Required a minimum EBITDA covenant of trailing twelve-month EBITDA commencing October 31, 2016; • Permitted the lender to require the Company to pay additional interest of 2.00% per annum during an event of default; • Redeemable by the lender in an event of default or various other situations; and • Matured on the earlier of (i) June 28, 2021, (ii) the maturity date of the Wells Fargo Credit Agreement, which at the time of issuance of the TPG Term Loan was January 31, 2018, because the Wells Fargo Credit Agreement matures 90 days prior to the maturity of the Unsecured Senior Notes, or (iii) 90 days prior to the final maturity of the Unsecured Senior Notes, which at the time of issuance of the TPG Term Loan was May 1, 2018. Therefore, the TPG Term Loan maturity date upon issuance was January 31, 2018. The proceeds received from the TPG Term Loan were used to reduce the Wells Fargo revolving credit facility borrowings. The Company paid $1.3 million of lender fees and $1.6 million of other deferred costs in connection with the original TPG Term Loan. The TPG Term Loan was amended as follows: Amendment Date and Title Reason for Amendment Significant Changes to the TPG Term Loan August 22, 2016. TPG First Amendment To facilitate waiver of events of default triggered by the Company's delay in filing Form 10-Q for the period ended June 30, 2016 and failure to disclose a litigation • Provided certain waivers under the credit agreements related to the delayed Form 10-Q filing for the period ended June 30, 2016 and a failure to disclose litigation; December 19, 2016. TPG Second Amendment To facilitate waiver of event of default triggered by the Company's failure to meet minimum EBITDA required for the month ended October 31, 2016 • Made permanent the $12.5 million reserve against the Wells Fargo borrowing base availability as discussed in the Wells Fargo Credit Agreement section above; February 6, 2017. Limited Waiver Agreement To facilitate waiver of various Events of Default triggered by resignation of the Company's auditor and removal of audit opinion on the Company's 2015 and 2014 consolidated financial statements • Waived various events of default related to resignation of the Company's external auditors; • Provided the lenders with the right to charge additional interest of 2% per annum even though events of default had been waived; and • Agreed that the outstanding principal amount of the TPG Term Loan was $71.4 million, comprised of the original amount of $60.0 million, the $3.0 million fee from the August 22, 2016 Amendment and the $8.4 million fee from the December 19, 2016 Amendment. The Company incurred lender-related fees of $2.3 million in 2016, which were deferred and amortized to “Interest expense” in the Consolidated Statements of Operations over the remaining term of the TPG Loan. In addition, the amendment fees of $11.4 million that the Company agreed to pay upon maturity of the TPG Loan were accrued and amortized as “Interest expense” over the remaining term of the TPG Loan. There were no such fees incurred in 2017. Third-party fees of $0.4 million and $0.4 million were incurred in 2017 and 2016, respectively. These costs were expensed to “Loss on debt extinguishment and modifications” in the Consolidated Statements of Operations. At December 31, 2016, the accrued and unpaid interest on the TPG Term Loan, which bore interest at 10.84% per annum (LIBOR plus 9.75% margin), was $1.2 million . In March 2017, the Company repaid the TPG Term Loan using the proceeds of the Weichai investment as discussed in Note 3. Weichai Transactions . In conjunction with this repayment, the Company recorded an $11.9 million (including third-party fees of $0.4 million mentioned above) loss on debt extinguishment based on the difference between the amount repaid to the lender and the net carrying value of the TPG Term Loan immediately preceding repayment, including accrued and unpaid interest. This item is reflected within “Loss on debt extinguishment and modifications” in the Company's 2017 Consolidated Statement of Operations.

Fair Value of Financial Instrum

Fair Value of Financial Instruments	12 Months Ended
	Dec. 31, 2017
Fair Value Disclosures [Abstract]
Fair Value of Financial Instruments	Fair Value of Financial Instruments For assets and liabilities measured at fair value on a recurring and nonrecurring basis, a three-level hierarchy of measurements based upon observable and unobservable inputs is used to arrive at fair value. Observable inputs are developed based on market data obtained from independent sources, while unobservable inputs reflect the Company’s assumptions about valuation based on the best information available in the circumstances. Depending on the inputs, the Company classifies each fair-value measurement as follows: • Level 1 — based on quoted prices in active markets for identical assets or liabilities; • Level 2 — based on other significant observable inputs for the assets or liabilities through corroborations with market data at the measurement date; and • Level 3 — based on significant unobservable inputs that reflect management’s best estimate of what market participants would use to price the assets or liabilities at the measurement date. Financial Instruments Measured at Carrying Value Current Assets Cash and cash equivalents are measured at carrying value, which approximates fair value because of the short-term maturities of these instruments. Debt The Company measures its Wells Fargo revolving credit facility, term loans and the Unsecured Senior Notes at original carrying value adjusted for unpaid waiver fees agreed to be added to principal, including accrued interest, net of unamortized deferred financing costs and fees. The fair value of the revolving credit facility approximates carrying value, as it consists of short-term variable rate loans. The Unsecured Senior Notes were issued on April 29, 2015, and their fair value as of December 31, 2015 approximated their carrying value. The fair-value measurement of these financial liabilities subsequent to December 31, 2015 was defined as Level 3 in the three-level valuation hierarchy, as the inputs to their valuation are not all market observable. (in thousands) As of December 31, 2017 Carrying Value Fair Value Level 1 Level 2 Level 3 Wells Fargo revolving credit facility $ 37,055 $ — $ 37,055 $ — Unsecured Senior Notes 55,000 — — 50,000 (in thousands) As of December 31, 2016 Carrying Value Fair Value Level 1 Level 2 Level 3 Wells Fargo revolving credit facility $ 12,774 $ — $ 12,774 $ — Unsecured Senior Notes 55,000 — — 49,800 TPG Term Loan 71,400 — — 70,800 (in thousands) As of December 31, 2015 Carrying Value Fair Value (Restated) (Restated) Level 1 Level 2 Level 3 Wells Fargo revolving credit facility $ 97,299 $ — $ 97,299 $ — Unsecured Senior Notes 55,000 — — 55,000 (in thousands) As of December 31, 2014 Carrying Value Fair Value (Restated) (Restated) Level 1 Level 2 Level 3 Wells Fargo revolving credit facility $ 78,030 $ — $ 78,030 $ — Wells Fargo Term Loan 4,028 — 4,028 — Other Financial Assets and Liabilities In addition to the methods and assumptions used for the financial instruments discussed above, Accounts receivable, net, Income tax receivables and Accounts payable are measured at carrying value, which approximates fair value because of the short-term maturities of these instruments. Financial Instruments Measured at Fair Value The Company's warrants and the contingent consideration liabilities were measured at fair value based on unobservable inputs and were, thus, considered Level 3 financial instruments in the three-level valuation hierarchy. As of December 31, 2015, the Base and Additional Earn-outs were finalized. The Base and Additional Earn-outs were paid in cash during 2016, as discussed below in Contingent Consideration section. (in thousands) As of December 31, 2017 Carrying Value Fair Value Level 1 Level 2 Level 3 Weichai warrant liability $ 24,700 $ — $ — $ 24,700 Contingent consideration 12 — — 12 (in thousands) As of December 31, 2016 Carrying Value Fair Value Level 1 Level 2 Level 3 Contingent consideration $ 38 $ — $ — $ 38 (in thousands) As of December 31, 2015 Carrying Value Fair Value (Restated) (Restated) Level 1 Level 2 Level 3 Private placement warranty liability $ 1,482 $ — $ — $ 1,482 Contingent consideration 8,717 — — 8,717 (in thousands) As of December 31, 2014 Carrying Value Fair Value (Restated) (Restated) Level 1 Level 2 Level 3 Private placement warranty liability $ 11,036 $ — $ — $ 11,036 Warrants The following table summarizes changes in the estimated fair value of the Company’s warrant liability: (in thousands) As of December 31, 2017 2016 2015 2014 (Restated) (Restated) Balance at beginning of year $ — $ 1,482 $ 11,036 $ 24,525 Exercise of private placement warrants — (69 ) (255 ) (7,320 ) Issuance of warrants 20,700 — — — Increase (decrease) in value * 4,000 (1,413 ) (9,299 ) (6,169 ) Balance at end of year $ 24,700 $ — $ 1,482 $ 11,036 * Loss (gain) related to the change in fair value of the warrants for each year are presented as “ Loss (gain) from change in fair value of warrants ” in the Company's Consolidated Statements of Operations. Weichai Warrant Liability The Company estimated the fair value of the Weichai Warrant financial instrument using a publicly traded stock pricing approach with a Black-Scholes option pricing model and a Monte Carlo simulation. Given the unobservable nature of the inputs to the pricing models, the Weichai Warrant was classified as a Level 3 instrument. The inputs of the Black-Scholes option pricing model were as follows: Assumptions December 31, 2017 Market value of the Common Stock $7.50 Exercise price varies Risk-free interest rate 1.8 % Estimated price volatility 95 % Contractual term 1.0 year Dividend yield — The estimated price volatility represents the upper end of the range of implied volatility of publicly traded call options of benchmark companies. Private Placement Warrant Liability As of December 31, 2015 and 2014, the Company estimated the fair value of its Private Placement Warrant liability using the Black-Scholes option pricing model. Given the unobservable nature of the inputs to the pricing model, the Private Placement Warrants were classified as Level 3 instruments. The inputs of the Black-Scholes option pricing model were as follows: As of December 31, Assumptions 2015 2014 Closing price of the Common Stock $18.25 $51.61 Exercise price $13.00 $13.00 Estimated price volatility * 55 % 55 % Contractual term 0.58 years 1.33 years * Represents the upper end of the range of implied volatility of publicly traded call options of benchmark companies. Contingent Consideration The following table summarizes the change in the estimated fair value of the Company’s contingent consideration, primarily for Powertrain in 2016 and 2015 and for 3PI in 2014. (in thousands) For the Year Ended December 31, 2017 2016 2015 (Restated) 2014 (Restated) Balance at beginning of year $ 38 $ 8,717 $ — $ — Initial estimate of contingent consideration liability — — 8,740 3,840 Increase (decrease) in value reflected in income 1 — (230 ) (23 ) (3,840 ) Payment of contingent consideration 2 (26 ) (8,449 ) — — — Balance at end of year $ 12 $ 38 $ 8,717 $ — Less: Noncurrent portion — 12 442 — Short-term contingent consideration at end of year $ 12 $ 26 $ 8,275 $ — 1. Includes $0.1 million of interest on contingent consideration recorded in Interest expense on the Consolidated Statement of Operations. 2. Includes $0.1 million of cash paid in excess of the initial fair value estimate of contingent consideration at the time of the Powertrain acquisition and presented in “ Other, net ” within cash flows from operating activities in the Consolidated Statement of Cash Flows. The Company's original liability for Powertrain's contingent consideration for the Base and Additional Earn-outs associated with the May 2015 acquisition was measured at fair value based on unobservable inputs and it was, therefore, considered a Level 3 financial instrument. The Base and Additional Earn-outs were initially determined using a Monte Carlo simulation model. The Base Earn-out was to be paid upon the achievement of predetermined levels of net sales for 2015, and the Additional Earn-out was defined as the greater of a 5.0% per annum return on the Base Earn-out or the increase in the Company's VWAP Common Stock price, as defined in the APA, from the acquisition date of May 1, 2015 through January 1, 2016. The Powertrain Base and Additional Earn-outs were adjusted to estimated fair value at the end of each quarter in 2015. At December 31, 2015, however, the end of the measurement period, all of the inputs needed to compute the Powertrain Base and Additional Earn-outs were known and determined to be $8.2 million . The Company recognized additional “Contingent consideration” expense in its 2015 Consolidated Statement of Operations for Powertrain as indicated in the table above. This adjustment was due to changes in the original estimated fair value of the Powertrain Base and Additional Earn-outs during 2015. See Note 5. Acquisitions for additional information related to the Powertrain and 3PI acquisitions and information related to other insignificant contingent consideration liabilities noted in the above table.

Defined Contribution Plans

Defined Contribution Plans	12 Months Ended
	Dec. 31, 2017
Retirement Benefits [Abstract]
Defined Contribution Plans	Defined Contribution Plans The Company has defined contribution plans for the benefit of its employees meeting certain eligibility requirements. Under the plans, participants may choose from various investment options and can contribute an amount of their eligible compensation annually as defined by the applicable plan documents, subject to IRS limitations. The Company contributed $0.1 million to these plans in each of 2017, 2016, 2015 and 2014. Subsequent to December 31, 2017, the Company merged its defined contribution plans into a single plan, sponsored by the Company, with the final merger effective December 1, 2018.

Commitments and Contingencies

Commitments and Contingencies	12 Months Ended
	Dec. 31, 2017
Commitments and Contingencies Disclosure [Abstract]
Commitments and Contingencies	Commitments and Contingencies Legal Contingencies From time to time, the Company is a party to legal proceedings and potential claims arising in the ordinary course of business. Despite the inherent uncertainties of litigation, management believes that the ultimate disposition of such proceedings and exposure, after taking into account recorded accruals and the availability and limits of insurance coverage, will not have a material adverse impact on its results of operations. The legal matters discussed below and others could result in losses, including damages, fines, civil penalties and criminal charges, which could be substantial. The Company records accruals for these contingencies to the extent the Company concludes that a loss is both probable and reasonably estimable. The Company also records an accrual for legal fees related to these contingencies. Regarding the matters disclosed below, unless otherwise disclosed, the Company has determined that liabilities associated with these legal matters are reasonably possible; however, unless otherwise stated, the liabilities cannot be reasonably estimated. Given the nature of the litigation and investigations and the complexities involved, the Company is unable to reasonably estimate a possible loss for all such matters until the Company knows, among other factors: • What claims, if any, will survive dispositive motion practice; • The extent of the claims, particularly when damages are not specified or are indeterminate; • How the discovery process will affect the litigation; • The settlement posture of the other parties to the litigation; and • Any other factors that may have a material effect on the litigation or investigation. However, the Company could incur judgments, enter into settlements or revise its expectations regarding the outcome of certain matters, and such developments could have a material adverse effect on the Company's results of operations in the period in which the amounts are accrued and/or liquidity in the period in which the amounts are paid. Carl Trent, Kenneth Trent, and CKT Holdings, Inc. vs. 3PI and the Company On October 24, 2014, the Trents filed a complaint in Circuit Court in Walworth County, Wisconsin against the Company and its subsidiary, 3PI, asserting that the Company breached their employment contracts and seeking declaratory judgment with regard to the stock purchase agreement entered into by and between the Company and the Trents on April 1, 2014 relating to the Company's acquisition of 3PI. As part of the Trents’ claim for breach of their employment agreements, they sought damages of between $0.5 million and $1.0 million . As part of the Trents’ claim for declaratory judgment, the Trents sought judgment against the Company obligating the Company to calculate and issue certain accelerated payments and an earn-out described in the stock purchase agreement. On April 24, 2015, together with 3PI, the Company filed an amended answer and affirmative defenses to the complaint, along with a counterclaim against the Trents alleging that they had breached their employment contracts, fraudulently induced the Company to enter into the employment agreements, breached their fiduciary duties, converted 3PI property and confidential business information, conspired to interfere with and steal 3PI’s confidential and proprietary business information, and misappropriated trade secrets belonging to 3PI. By way of the counterclaim, the Company and 3PI sought compensatory damages in the amount of $20.0 million , consequential damages, punitive damages in excess of $20.0 million , and also an injunction prohibiting the Trents from continuing to retain 3PI’s confidential business information and other equitable relief. On June 30, 2016, the Trents amended their complaint to additionally allege that the Company and 3PI breached the stock purchase agreement by failing to maintain the assets and properties of 3PI in good working order and condition, failed to operate 3PI in good faith, took actions to reduce 3PI's EBITDA used in connection with determining the number of shares issuable to the Trents as part of the earn-out described in the stock purchase agreement, and failed to make a tax gross-up payment to the Trents as mandated by the stock purchase agreement. The Trents sought additional damages for these alleged breaches in the amount of $0.35 million for the tax gross-up payment and $9.3 million for the equity payment under the stock purchase agreement. On June 1, 2017, the Company settled this matter for $3.0 million in return for full and final mutual releases of all claims, predicated on the Company making a payment of $1.75 million on June 30, 2017 and the remaining $1.25 million in 12 equal monthly installment payments from June 2017 to June 2018. As of December 31, 2017, $0.625 million remained owed to the Trents, with the final payment being made in June 2018. Bandit / U.S. EPA In December 2014, Bandit, an OEM customer of the Company, inquired as to the designation of approximately 2,300 diesel engines it had purchased from the Company since January 1, 2012 pursuant to the Transition Program for Equipment Manufacturers (“TPEM”) under the Federal Clean Air Act. Bandit alleged that its records of the engines' designations did not match the Company's records of the engines’ designations, and that Bandit initially believed these engines to be legally conforming engines pursuant to TPEM, but later ascertained that it had exceeded its TPEM flex credit allowance set forth in its TPEM plan for Tier 3 flex engines for the years 2012 to 2015 (“Bandit’s Flex Plan”). The Company is not the Manufacturer of Record (“MOR”) or the OEM with regard to enforcement of the TPEM regulations but serves as a supplier of non-road diesel engines to Bandit as part of the distribution chain. Some engines ordered by and delivered to Bandit by the Company were not labeled with the required information upon sale to Bandit. In May 2015, the Company self-reported to the EPA the potential mislabeling of a small number of engines sold to Bandit, along with the Company's remediation actions pursuant to the EPA’s Voluntary Audit and Self-Disclosure Policy, including a new standard operating procedure with new shipment restrictions, and record-keeping and labeling requirements to verify the status of each engine upon delivery. To date, the EPA has not contacted the Company with regard to the Company's self-disclosure and remediation actions, and, therefore, it is the Company's and its outside counsel’s belief that it is not probable that the EPA will initiate any action against it related to this matter. The Company has not had any previous clean-air violations pursuant to the Federal Clean Air Act. In February 2015, Bandit self-disclosed that it had exceeded Bandit’s Flex Plan, and in November 2016, the EPA and Bandit reached an agreement to resolve the government’s allegations against Bandit whereby Bandit would continue to operate and supply products and services to its customers. Securities and Exchange Commission and United States Attorney’s Office for the Northern District of Illinois Investigations The Chicago Regional Office of the SEC is conducting an investigation and issued a subpoena to the Company requiring the production of documents and information. The investigation is focused on, among other things, the Company's financial reporting, misapplication of U.S. GAAP, revenue recognition practices and related conduct, which resulted in the accounting errors giving rise to the restatements reported herein. The United States Attorney's Office for the Northern District of Illinois (the “USAO”) also is conducting a parallel investigation regarding these matters. The Company has been fully cooperating with the SEC and the USAO with respect to these investigations. At this time, the Company is unable to predict the outcome of these matters or provide meaningful quantification of how the final resolution of these matters may impact its results of operations, financial condition or cash flows. Securities Litigation On August 22, 2016, Sumit Gupta filed a putative stockholder class-action complaint against the Company, Gary S. Winemaster, Michael P. Lewis and Daniel P. Gorey in the U.S. District Court for the Northern District of Illinois (the “ Gupta Action”). The complaint alleged violations of Sections 10(b) and 20(a) of the Securities Exchange Act of 1934, arising from public filings made between May 8, 2015 and August 15, 2016. On October 7, 2016, Peter Stout initiated a second suit, asserting similar claims against the same defendants (the “ Stout Action”). On January 19, 2017, the Court consolidated the Gupta Action and the Stout Action and appointed Richard Giunta as lead plaintiff. The consolidated case is captioned Giunta v. Power Solutions International, Inc. , No. 1:16-cv-09599 (N.D. Ill.) (the “ Giunta Action”). The plaintiffs then filed an Amended Class Action Complaint (the “Amended Complaint”) against the Company and certain current and former officers and directors. The Amended Complaint alleges violations of Sections 10(b) and 20(a) of the Securities Exchange Act of 1934 arising from public filings, press releases and conference calls between February 27, 2014 and February 2, 2017. On January 22, 2019, the parties executed a Stipulation and Agreement of Settlement (the “Settlement”) to resolve the Giunta Action. Under the terms of the Settlement, a payment of $8.5 million will be made by the Company and/or its insurers in exchange for the release of claims against the defendants and other released parties by the lead plaintiff and all settlement class members and for the dismissal of the Giunta Action with prejudice. On May 13, 2019, the court granted final approval of the settlement. The Company has accrued for the settlement in “Other accrued liabilities” and for the full insurance recovery of the settlement amount in “Prepaid expenses and other current assets” as of December 31, 2017 and 2016. No future impact is anticipated on the Company's financial condition or results of operations. See Note 1 , Summary of Significant Accounting Policies and Other Information for additional information related to the Company's insurance proceeds receivable and litigation reserves. Federal Derivative Litigation On February 10, 2017, Travis Dorvit filed a putative stockholder derivative action in the U.S. District Court for the Northern District of Illinois, captioned Dorvit v. Winemaster, et al. , No. 1:17-cv-01097 (N.D. Ill.) (the “ Dorvit Action”), against certain of the Company’s current and former officers and directors. The complaint asserted claims for breach of fiduciary duty and unjust enrichment arising from the same matters at issue in the Giunta Action. On April 3, 2018, Michael Martin filed a second putative stockholder derivative action, captioned Martin v. Winemaster, et al. , No. 18-CV-2386 (N.D. Ill.) (the “ Martin Action”), in the same court against certain of the Company’s current and former officers and directors. On July 3, 2018, the court consolidated the Martin Action and the Dorvit Actions. On July 17, 2018, the plaintiffs in the consolidated Dorvit and Martin Actions filed an amended consolidated complaint (the “Second Amended Complaint”) against certain of the Company’s current and former officers and directors, who are indemnified by the Company as to their legal fees and defense costs. The Second Amended Complaint asserts claims for breach of fiduciary duty, unjust enrichment, corporate waste and failure to hold an annual stockholders' meeting, and it seeks an unspecified amount of damages, an order compelling the Company to hold an annual stockholders' meeting and an award of costs, including reasonable attorneys’ fees and expenses. On October 1, 2018, the Company and individual defendants moved to dismiss the Second Amended Complaint on the grounds that the Second Amended Complaint fails to state a claim and does not adequately allege that pre-suit demand on the Company’s Board was excused. The motions to dismiss are fully briefed and pending before the court. On April 11, 2019, the parties reached an agreement in principle to settle the litigation for approximately $1.9 million , half of which will consist of a payment to the Company for certain defense costs, and the remaining half the plaintiffs intend to seek as an award of their attorney’s fees and expenses in connection with the benefit conferred by the settlement. The settlement is pending preliminary and final approval by the court. The Company has accrued for the settlement in “Other accrued liabilities” and for the full insurance recovery of the settlement amount in “Prepaid expenses and other current assets” as of December 31, 2017. If approved by the Court, the settlement would not have a material impact on the Company’s results of operations, financial condition or cash flows. State Derivative Litigation On May 5, 2017, Lewis McClenney filed a putative stockholder derivative action in the Chancery Division of the Circuit Court of Cook County, Illinois, captioned McClenney v. Winemaster, et al. , No. 2017-CH-06481 (the “ McClenney Action”), against certain of the Company’s current and former officers and directors. The McClenney Action asserted claims for breach of fiduciary duty, unjust enrichment, abuse of control, gross mismanagement and corporate waste arising from the same matters at issue in the Giunta Action. On the same day that the McClenney Action was filed, Sara Rebscher also filed a putative stockholder derivative action in the same court, captioned Rebscher v. Winemaster, et al. , No. 2017-CH-06517 (the “ Rebscher Action”). The Rebscher Action asserts claims for breach of fiduciary duty and unjust enrichment against certain of the Company’s current and former officers and directors, arising from the same matters at issue in the Giunta Action. Additionally, the complaint in the Rebscher Action asserts a claim for professional negligence and accounting malpractice against the Company’s former auditor, RSM U.S. LLP (“RSM”). On July 26, 2017, the court consolidated the McClenney Action and the Rebscher Action. Subsequently, the court appointed Rebscher as lead plaintiff and designated the Rebscher complaint as the operative complaint. On November 9, 2018, the court granted the Company’s motion to dismiss the consolidated case with prejudice on the grounds that it is duplicative of the Dorvit and Martin Actions. Plaintiffs moved for reconsideration of the Court’s decision, which the Court denied on January 14, 2019. On February 5, 2019, plaintiffs filed a notice of appeal from the Court’s order dismissing the case. If the settlement of the consolidated Dorvit and Martin Actions is approved by that Court, the settlement would result in a release of the claims alleged by Rebscher against the Company and its current and former Officers and Directors. Eric Cohen vs. The Company On May 17, 2016, the Company announced that Eric A. Cohen would no longer serve as its Chief Operating Officer effective as of the close of business May 16, 2016, and that he had left the Company. On November 11, 2016, Mr. Cohen filed an administrative charge with the U.S. Department of Labor, and on June 9, 2017, Mr. Cohen filed a complaint against the Company in the U.S. District Court for the Northern District of Illinois alleging statutory violations of the Sarbanes-Oxley Act of 2002, the Dodd-Frank Wall Street Reform and Consumer Protection Act (“DFA”), and the Illinois Whistleblower Act, common-law claims of retaliatory discharge and fraudulent inducement and a claim for breach of his employment agreement and Stock Appreciation Rights agreements. Due to Mr. Cohen electing to proceed with his case in federal court rather than before the Secretary of Labor, his administrative charge with the U.S. Department of Labor was dismissed on July 25, 2017. On November 3, 2017, the Company filed a motion for partial judgment on the pleadings seeking to dismiss Mr. Cohen’s DFA claim and his retaliatory-discharge claim. After the parties fully briefed this motion, the U.S. Supreme Court issued a conclusive decision regarding the DFA in Digital Realty Trust, Inc. v. Somers . As a result, Cohen withdrew his opposition to the Company’s motion regarding the DFA claim (Count II), and the court granted judgment in favor of the Company regarding Count II. On April 23, 2018, the court also granted judgment on the pleadings in the Company's favor with regard to Cohen’s common-law claim for retaliatory discharge (Count IV). Discovery is proceeding on the remaining claims. The Company believes it has strong defenses against the remaining claims and intends to continue to vigorously defend against them. At this time, the Company is unable to predict the outcome of this matter or provide meaningful quantification of how the final resolution of this matter may impact its results of operations, financial condition or cash flows. Jerome Treadwell v. The Company On October 30, 2018, a putative class-action complaint was filed against the Company and NOVAtime Technology, Inc. (“NOVAtime”) in the Circuit Court of Cook County, Illinois. On December 14, 2018, NOVAtime removed the case to the U.S. District Court for the Northern District of Illinois, Eastern Division under the Class Action Fairness Act. Plaintiff has since voluntarily dismissed NOVAtime from the lawsuit without prejudice and filed an amended complaint on April 11, 2019. The operable, amended complaint asserts violations of the Illinois Biometric Information Privacy Act (“BIPA”) in connection with employees’ use of the time clock to clock in and clock out using a finger scan and seeks statutory damages, attorneys’ fees, and injunctive and equitable relief. An aggrieved party under BIPA may recover (i) $1,000 per violation if the Company is found to have negligently violated BIPA or (ii) $5,000 per violation if the Company is found to have intentionally or recklessly violated BIPA plus reasonable attorneys’ fees. The Company intends to vigorously defend against this action. At this time, the Company is unable to predict the outcome of this matter or provide meaningful quantification of how the final resolution of this matter may impact its results of operations, financial condition or cash flows. Other Commitments Letters of Credit At December 31, 2017, the Company had two outstanding letters of credit totaling $0.5 million . Guaranteed Minimum Commission Payment In September 2017, the Company entered into an asset purchase agreement to acquire the Alternative-Fuel Specialty vehicle modifier technology from AGA Systems, LLC (“AGA”), a Utah limited liability company, and paid an initial cash consideration of $0.5 million . Pursuant to the AGA asset purchase agreement, the Company also agreed to make quarterly commission payments with guaranteed minimum commission payment of $1.2 million , including $0.4 million to be made in 2018. In March 2018, the Company executed an asset purchase agreement to acquire the Alternative-Fuel Specialty vehicle modifier technology, including certifications, source code, drawings, computer-aided design models, engineering analyses, know-how, files and scripts, from AGA, for cash consideration of $1.5 million plus a potential commission payment of up to $4.5 million , of which $1.2 million was guaranteed.

Income Taxes

Income Taxes	12 Months Ended
	Dec. 31, 2017
Income Tax Disclosure [Abstract]
Income Taxes	Income Taxes Income tax expense (benefit) was as follows: (in thousands) For the Year Ended December 31, 2017 2016 2015 (Restated) 2014 (Restated) Current tax expense (benefit): Federal $ 127 $ (6,568 ) $ (859 ) $ 7,476 State 77 60 215 1,892 Total $ 204 $ (6,508 ) $ (644 ) $ 9,368 Deferred tax expense (benefit) Federal $ 100 $ 13,907 $ (6,713 ) $ (1,183 ) State 139 4,214 (2,345 ) (441 ) Total deferred tax expense (benefit) 239 18,121 (9,058 ) (1,624 ) Total tax expense (benefit) $ 443 $ 11,613 $ (9,702 ) $ 7,744 The Company received net cash refunds for income taxes of $6.3 million and $4.6 million in 2017 and 2016, respectively, and made net cash payments for income taxes of $7.1 million and $5.3 million in 2015 and 2014, respectively. A reconciliation between the Company’s effective tax rate on (loss) income before income taxes and the statutory tax rate was as follows: (in thousands) For the Year Ended December 31, 2017 2016 2015 (Restated) 2014 (Restated) Amount Percent Amount Percent Amount Percent Amount Percent Income tax (benefit) expense at federal statutory rate $ (16,037 ) 34.0 % $ (12,192 ) 34.0 % $ (4,282 ) 34.0 % $ 9,935 34.0 % State income tax, net of federal benefit (2,283 ) 4.8 % (1,758 ) 4.9 % (1,101 ) 8.7 % 1,295 4.4 % Non-deductible warrants (income)/expense 1,360 (2.9 )% (481 ) 1.3 % (3,162 ) 25.1 % (2,098 ) (7.2 )% Domestic production activity — — % — — % — — % (334 ) (1.1 )% Other permanent differences 106 (0.2 )% 110 (0.3 )% 137 (1.1 )% 191 0.7 % Research and development tax credits (426 ) 0.9 % (837 ) 2.3 % (1,632 ) 13.0 % (1,953 ) (6.7 )% Tax reserve reassessment 104 (0.2 )% (141 ) 0.4 % 412 (3.3 )% 246 0.8 % Federal tax rate change 10,899 (23.1 )% — — % — — % — — % Change in valuation allowance 4,956 (10.4 )% 26,846 (74.9 )% — — % — — % 3PI Settlement 1,976 (4.2 )% — — % — — % — — % Other, net (212 ) 0.4 % 66 (0.1 )% (74 ) 0.6 % 462 1.6 % Income tax expense (benefit) $ 443 (0.9 )% $ 11,613 (32.4 )% $ (9,702 ) 77.0 % $ 7,744 26.5 % For the year ended December 31, 2017, the Company recognized a pretax loss of $47.2 million , which included $4.0 million of permanently excludable loss associated with the change in the valuation of the Weichai Warrant. For the year ended December 31, 2016, the Company recognized a pretax loss of $35.9 million , which included $1.4 million of permanently excludable income associated with the change in the valuation of its Private Placement Warrants. For the year ended December 31, 2015, the Company recognized a pretax loss of $12.6 million , which included $9.3 million of permanently excludable income associated with the change in the valuation of its Private Placement Warrants. For the year ended December 31, 2014, the Company recognized pretax income of $29.2 million , which included $6.2 million of permanently excludable income associated with the change in the valuation of the Private Placement Warrants. On December 22, 2017, the President of the U.S. signed the Tax Act, which made broad and complex changes to the U.S. Tax Code, including, but not limited to, (i) reducing the U.S. federal corporate income tax rate from 34.0% to 21.0% , (ii) requiring companies to pay a one-time transitional tax on certain un-repatriated earnings of foreign subsidiaries, (iii) generally eliminating U.S. federal income tax on dividends from foreign subsidiaries of U.S. corporations, (iv) repealing the domestic production activity deduction, (v) providing for the full expensing of qualified property, (vi) adding a new provision designed to tax global intangible low-taxed income (“GILTI”), (vii) revising the limitation imposed on deductions for executive compensation paid by publicly-traded companies, (viii) eliminating the corporate alternative minimum tax (“AMT”) and changing how existing AMT credits can be utilized, (ix) creating a base erosion-anti-abuse tax (“BEAT”), a new minimum tax on payments made by certain U.S. corporations to related foreign parties, (x) imposing a new limitation on the deductibility of interest expense, (xi) allowing for a deduction related to foreign-derived intangible income (“FDII”) and (xii) changing the rules related to the uses and limitations of net operating loss carryforwards generated in tax years beginning after December 31, 2017. The Company calculated the impact of the Tax Act in accordance with its understanding of the act and guidance available as of December 31, 2017, and, as a result, recorded $10.8 million as additional income tax expense, offset with an $11.3 million tax benefit from the change in the valuation allowance in the fourth quarter of 2017, the period in which the legislation was enacted. In December 2015, the Protecting Americans from Tax Hikes Act of 2015 (“PATH Act”) was signed into law making the research and development tax credit permanent. The Company’s income tax expense for the year ended December 31, 2015 was favorably affected by the recognition of federal tax credits in 2015. Partially offsetting the increase in income tax expense for the year ended December 31, 2014 were research and development tax credits recorded in 2014, net of unrecognized tax benefits, arising from the one-year extension of the federal research and development tax credit as well as continuing state research tax credits. The Company generates R&D tax credits as a result of its R&D activities, which reduce the Company’s effective income tax rate. In general, these credits are general business credits and may be carried forward up to 20 years to be offset against future taxable income. Significant components of deferred income tax assets and liabilities consisted of the following: (in thousands) As of December 31, 2017 2016 2015 (Restated) 2014 (Restated) Deferred tax assets: Net operating loss carryforwards $ 15,399 $ 1,154 $ 66 $ — Research and development credits 2,806 2,118 139 — Other state credits 989 407 164 — Inventory 2,560 5,837 5,094 3,035 Allowances and bad debts 596 501 334 119 Accrued warranty 3,387 3,820 1,413 948 Accrued wages and benefits 351 786 893 917 Stock-based compensation 645 1,021 756 576 Capitalized research and development costs 1,090 2,291 2,617 2,316 Intangible amortization 1,734 4,519 4,311 — Other 3,397 6,638 5,069 3,615 Total deferred tax assets 32,954 29,092 20,856 11,526 Valuation allowance (31,992 ) (26,847 ) — — Total deferred tax assets, net of valuation allowance $ 962 $ 2,245 $ 20,856 $ 11,526 Deferred tax liabilities: Intangible amortization $ — $ — $ — $ (1,091 ) Tax depreciation in excess of book depreciation on property, plant and equipment (1,665 ) (2,709 ) (3,199 ) (1,870 ) Total deferred tax liabilities $ (1,665 ) $ (2,709 ) $ (3,199 ) $ (2,961 ) Net deferred tax (liability) asset $ (703 ) $ (464 ) $ 17,657 $ 8,565 The Company’s net deferred tax assets and liabilities are presented as follows in the Consolidated Balance Sheets: (in thousands) As of December 31, 2017 2016 2015 (Restated) 2014 (Restated) Current deferred tax assets, net $ — $ — $ — $ 8,552 Non-current deferred tax asset/(liabilities), net (703 ) (464 ) 17,657 13 Net deferred tax (liability) asset $ (703 ) $ (464 ) $ 17,657 $ 8,565 In preparing the Consolidated Statements of Operations, the Company has assessed the likelihood that its deferred income tax assets will be realized from future taxable income. In evaluating the ability to recover its deferred income tax assets, the Company considers all available evidence, positive and negative, including the Company’s operating results, ongoing tax planning and forecasts of future taxable income on a jurisdiction-by-jurisdiction basis. A valuation allowance is established if it is determined that it is more likely than not that some portion or all of the net deferred income tax assets will not be realized. The Company exercises significant judgment in determining the Company’s income tax expense, its deferred income tax assets and liabilities, and its future taxable income for purposes of assessing its ability to utilize any future tax benefit from its deferred income tax assets. Although the Company believes that its tax estimates are reasonable, the ultimate tax determination involves significant judgments that could become subject to audit by tax authorities in the ordinary course of business. As of each reporting date, the Company considers new evidence, both positive and negative, that could impact the Company's view with regard to future realization of deferred tax assets. During the second quarter of 2016, the Company considered both the positive and the negative evidence available in order to assess the realizability of its deferred tax assets. As a result of this evaluation, the Company concluded that the negative evidence outweighed the positive evidence and recorded a full valuation allowance of the $17.8 million against its net deferred tax assets. The Company continues to maintain a full valuation allowance of $32.0 million and $26.8 million on its deferred tax assets as of December 31, 2017 and 2016, respectively. As of December 31, 2017, the Company has, on a tax-effected basis, $2.4 million in R&D and state tax credit carryforwards and $10.8 million in federal net operating loss carryforwards that are available to offset taxable income in the future. The tax credit carryforwards will begin to expire in 2020. The federal net operating loss carryforwards begin to expire in 2037. The state net operating loss carryforwards, on a tax-effected basis and net of federal tax benefit, are $4.6 million . The state net operating loss carryforwards begin to expire in 2025. The change in unrecognized tax benefits excluding interest and penalties were as follows: (in thousands) For the Year Ended December 31, 2017 2016 2015 2014 Unrecognized Tax Benefits Excluding Interest and Penalties (Restated) (Restated) Balance at beginning of year $ 1,202 $ 1,338 $ 894 $ 614 Additions based on tax positions related to the current year 105 168 525 373 Additions/(reductions) for tax positions of prior years — (304 ) (81 ) (93 ) Balance at end of year $ 1,307 $ 1,202 $ 1,338 $ 894 The Company recognizes interest and penalties related to unrecognized tax benefits in income tax expense. As of December 31, 2017, 2016, 2015 and 2014, the amount accrued for interest and penalties was not material. The Company reflects the liability for unrecognized tax benefits as “Other noncurrent liabilities” in its Consolidated Balance Sheets. The amounts included in “Additions/(reductions) for tax positions of prior years” represent decreases in the unrecognized tax benefits relating to settlements reached with taxing authorities during each year shown. As of December 31, 2017, the Company believes the liability for unrecognized tax benefits, excluding interest and penalties, could decrease by $0.2 million in 2018 due to lapses in the statute of limitations. Due to the various jurisdictions in which the Company files tax returns, it is possible that there could be other significant changes in the amount of unrecognized tax benefits in 2018, but the amount cannot be estimated. With few exceptions, the major jurisdictions subject to examination by the relevant tax authorities and open tax years, stated as the Company’s fiscal years, are as follows: Jurisdiction Open Tax Years U.S. Federal 2014 - 2017 U.S. States 2013 - 2017 The Company is currently under federal income tax audit for tax years 2015 and 2016 and federal employment tax audit for tax years 2017, 2016 and 2015. The Company is currently under Illinois income tax audit for tax years 2014, 2013, 2012 and 2011.

Stockholders' Equity

Stockholders' Equity	12 Months Ended
	Dec. 31, 2017
Equity [Abstract]
Stockholders' Equity	Weichai Transactions In March 2017, the Company and Weichai executed the SPA in which the Company issued stock and a warrant to Weichai for aggregate proceeds of $60.0 million , comprised of: • 2,728,752 shares of Common Stock; • 2,385,624 shares of Series B Redeemable Convertible Preferred Stock (“Series B Convertible Preferred Stock”) convertible on a two -for-one basis into 4,771,248 shares of Common Stock; and • The Weichai Warrant was exercisable for any number of additional shares of Common Stock such that Weichai, upon exercise, would hold 51% of the Common Stock then outstanding (on a fully-diluted as-converted basis). The Weichai Warrant also included an option to be exercised for Series B Convertible Preferred Stock upon approval of the Company's stockholders. The Company used proceeds from the sale of the above securities pursuant to the SPA and borrowings under the Wells Fargo Credit Agreement to pay off the outstanding TPG Term Loan (the “TPG Term Loan”) with TPG Specialty Lending, Inc. (“TPG”), discussed in Note 7. Debt . In August 2017, Gary S. Winemaster, former Chairman of the Board, Chief Executive Officer and President and nonexecutive Chief Strategy Officer, separately sold 200,000 additional shares to Weichai. Series B Redeemable Convertible Preferred Stock The Series B Convertible Preferred Stock was automatically convertible into Common Stock upon stockholder approval, as defined in the SPA. Commencing on September 30, 2017, Weichai was entitled to cumulative dividends at a stated rate of 10% per share, payable quarterly upon declaration by the Board, or as a liquidation preference for the Series B Convertible Preferred Stock. Any unpaid and deferred cash dividends would be deemed canceled and null upon conversion of the Series B Convertible Preferred Stock. In the event of liquidation, dissolution or winding-up of the Company, the holders of the Series B Convertible Preferred Stock would have been entitled to receive out of the assets of the Company available for distribution to stockholders of the Company, before any distributions on the Common Stock or any other junior stock, an amount equal to the greater of the liquidation preference ( $16.00 per share), plus accrued and unpaid dividends, or the amount that would otherwise be payable on an as-converted basis assuming the conversion of the Series B Convertible Preferred Stock into Common Stock. The Series B Convertible Preferred Stock also included a $23.1 million contingent beneficial conversion feature (“BCF”) that was considered to be “in the money” and “contingently beneficial” to Weichai, the warrant holder, upon the actual exercise of the Weichai Warrant, at Weichai's option at the commitment date, March 31, 2017, as the Company's stock price was greater than the conversion price at the commitment date. The Series B Convertible Preferred Stock and the Common Stock were assigned value based on their relative fair values after reducing the net proceeds from the Weichai transaction by the fair value of the Weichai Warrant, as required by accounting guidance. The resulting discount on the Series B Convertible Preferred Stock was accreted, with the remaining unaccreted amount included in the deemed dividend discussed below under “Deemed Dividend and Beneficial Conversion Feature .” In November 2017, the Company entered into a Securities Exchange Agreement (the “Exchange Agreement”) with Weichai that resulted in conversion of the 2,385,624 shares of Series B Convertible Preferred Stock into 4,771,248 shares of Common Stock. Weichai Warrant The Weichai Warrant was exercisable for a ninety ( 90 ) day period from September 30, 2018 to December 31, 2018 at a price per share of Common Stock equal to 85% of the Volume-Weighted Average Price (“VWAP”) during the 20 -day trading period immediately preceding the warrant exercise date or at a price per share of Common Stock equal to 50% of such preceding VWAP if the Company was delisted from NASDAQ as of September 30, 2018. The Weichai Warrant exercise price was subject to further reduction pursuant to a formula that provided for such adjustment in case the Company’s 2017 adjusted earnings before interest expense, income taxes, depreciation and amortization (“EBITDA”) (as defined within the SPA) were less than $22.0 million , or its net book value per share as of December 31, 2016 was less than $8.00 , provided that the aggregate amount of such downward adjustments would not exceed $15.0 million . The Exchange Agreement executed on November 30, 2017 amended the Weichai Warrant (the “Restated Warrant”) in addition to converting the Series B Convertible Preferred Stock to Common Stock as noted above. Under the Exchange Agreement, the Restated Warrant (i) was exercisable for Common Stock without obtaining stockholder approval, (ii) was no longer exercisable for Series B Convertible Preferred Stock and (iii) permitted the Company to accelerate the exercise of the Restated Warrant prior to September 30, 2018, to the extent that the Company required additional financing for any reason. In September 2018, the Weichai Warrant was amended under terms of a second amended and restated warrant (“Amended and Restated Warrant”) to defer its exercise date to a 90 -day period commencing April 1, 2019, at a price per share of the Company's Common Stock equal to the lesser of (i) 50% of the VWAP during the 20 consecutive trading day period preceding October 1, 2018 and (ii) 50% of the VWAP during the 20 consecutive trading day period preceding the date of exercise, subject to an adjustment that could reduce the exercise price by up to $15.0 million . In the event that the adjustment exceeded the exercise price, the excess would be due to the warrant holder. On April 23, 2019, Weichai exercised the Weichai Warrant resulting in the Company issuing 4,049,759 shares of the Company’s Common Stock and Weichai becoming the owner of 51.5% of the outstanding shares of the Company's Common Stock. The exercise proceeds for the warrants of $1.6 million were based on 50% of the VWAP during the 20 consecutive trading day period preceding April 23, 2019 and $15.0 million reduction in the exercise price described above. Valuation and Accounting for Issuance and Conversion to Common Stock, Series B Convertible Preferred Stock (and Related Beneficial Conversion Feature) and Weichai Warrant Detachable warrants issued in a bundled transaction with debt and equity offerings should be accounted for separately. If the warrants are classified as a liability recorded at fair value, then the total proceeds from the transaction are first allocated to the warrants based on their fair value, and residual proceeds are allocated to the remaining instruments based on their relative fair value. The Weichai Warrant is a freestanding derivative financial instrument that is not indexed solely to the Company's Common Stock due to the Weichai Warrant's exercise terms. Therefore, the Weichai Warrant is presented at fair value in the Company's Consolidated Balance Sheets in “Warrants” for $20.7 million at March 31, 2017 and $24.7 million at December 31, 2017. Changes in fair value of a loss of $4.0 million are reported in “Loss (gain) from change in fair value of warrants” in the Company's 2017 Consolidated Statement of Operations. See Note 8. Fair Value of Financial Instruments for additional details and assumptions used in valuing the Weichai Warrant, as well as 2017 fair value adjustments. The carrying values of the Common Stock and the Series B Convertible Preferred Stock were determined based on their relative fair values to the $39.3 million in aggregate remaining proceeds: $14.3 million was allocated to Common Stock and $25.0 million was allocated to the Series B Convertible Preferred Stock. Deemed Dividend and Beneficial Conversion Feature The difference between the stated proceeds related to the Common Stock and the Series B Convertible Preferred Stock of $38.7 million , pursuant to the SPA, and the net proceeds allocated to the Series B Convertible Preferred Stock based on relative fair value of $24.6 million (net of $0.4 million in transaction costs), is a discount of $14.1 million related to the Series B Convertible Preferred Stock, which was fully accreted onto the Consolidated Balance Sheet as part of the deemed dividend of $37.8 million ; which was recorded in “Additional paid-in capital”, as the Company had no retained earnings from the issuance date on March 31, 2017 until November 30, 2017, the date the Series B Convertible Preferred Stock was converted into Common Stock. The remaining portion of the deemed dividend was comprised of the $23.1 million BCF, which was recorded on the conversion date. Additionally, the Company recorded the exercise of the conversion option by reclassifying the $62.9 million carrying value of the Series B Convertible Preferred Stock to Common Stock, par value of $0.001 per share, with the remainder to “Additional paid-in capital.” Deemed dividends on Series B Convertible Preferred Stock were considered for calculations of earnings (loss) per share on Common Stock in 2017. See Note 14. Earnings Per Share . The Series B Convertible Preferred Stock also included a nondetachable contingent BCF that was considered to be “in the money” and “contingently beneficial” to Weichai, the warrant holder, upon the actual exercise of the warrant, at Weichai's option at the commitment date, March 31, 2017, as the Company's stock price was greater than the conversion price at the commitment date. The contingent BCF was recognized when the Series B Convertible Preferred Stock was converted into Common Stock. The carrying value for the contingent BCF was determined to be $23.1 million , based on conversion of 4,771,248 shares and a per-share value of $4.85 . The contingent BCF was included in the amount of deemed dividend on the Series B Convertible Preferred Stock when converted on November 30, 2017. Weichai Collaboration Arrangement The Company and Weichai executed a strategic collaboration agreement (the “Collaboration Agreement”) on March 20, 2017, in order to achieve their respective strategic objectives and enhance the strategic cooperation alliance to share experiences, expertise and resources. Among other things, the collaboration arrangement established a joint steering committee, permitted Weichai to second a limited number of certain technical, marketing, sales, procurement and finance personnel to work at the Company and established several collaborations, related to stationary natural-gas applications and Weichai Diesel Engines. The collaboration arrangement provided for the steering committee to create various sub-committees with operating roles and otherwise governs the treatment of intellectual property of parties prior to the collaboration and the intellectual property developed during the collaboration. The collaboration arrangement has a term of three years . The Company evaluates whether an arrangement is a collaborative arrangement at its inception based on the facts and circumstances specific to the arrangement. The Company also reevaluates whether an arrangement qualifies or continues to qualify as a collaborative arrangement whenever there is a change in either the roles of the participants or the participants’ exposure to significant risks and rewards dependent on the ultimate commercial success of the endeavor. For those collaborative arrangements, where it is determined that the Company is the principal participant, costs incurred and revenue generated from third parties are recorded on a gross basis in the financial statements. As of December 31, 2017, sales and purchases among the parties under the arrangement have been insignificant. Stockholders' Equity Common and Treasury Stock The changes in shares of Common and Treasury Stock were as follows: (in thousands) Common Shares Originally Issued Treasury Stock Shares Common Shares Outstanding Balance as of December 31, 2013 (Restated) 11,299 777 10,522 Net shares issued for Stock awards — (100 ) 100 Warrants exercised 109 — 109 Balance as of December 31, 2014 (Restated) 11,408 677 10,731 Net shares issued for Stock awards — (17 ) 17 Warrants exercised 5 — 5 Balance as of December 31, 2015 (Restated) 11,413 660 10,753 Net shares issued for Stock awards — (15 ) 15 Warrants exercised 154 — 154 Balance as of December 31, 2016 11,567 645 10,922 Net shares issued for Stock awards — (11 ) 11 Shares issued to Weichai * 2,729 — 2,729 Shares converted from Series B Convertible Preferred Stock * 4,771 — 4,771 Balance as of December 31, 2017 19,067 634 18,433 * See Note 3. Weichai Transactions for additional information. Preferred Stock The Company is authorized to issue 5,000,000 shares of preferred stock, par value $0.001 per share. The preferred stock may be designated into one or more series as determined by the Board. As of December 31, 2017, the Board had authorized two series of preferred stock as discussed further herein. At December 31, 2017, 2016, 2015 and 2014, there were no shares of preferred stock outstanding. Series B Convertible Preferred Stock and Weichai Warrant In March 2017, the Company issued 2,385,624 shares of Series B Convertible Preferred Stock to Weichai that were converted into 4,771,248 shares of the Company’s Common Stock in November 2017. On April 23, 2019, Weichai exercised the Weichai Warrant resulting in the Company issuing 4,049,759 shares of the Company’s Common Stock and Weichai becoming the owner of 51.5% of the outstanding shares of the Company's Common Stock. See Note 3. Weichai Transactions for additional information. Private Placement Warrants In connection with a private placement in April 2011, investors in the private placement received Series A Convertible Preferred Stock, which subsequently converted to shares of Common Stock, and Private Placement Warrants, with a five -year term. The Private Placement Warrants represented the right to purchase a total of 750,002 shares of Common Stock at an exercise price of $13.00 per share, subject to adjustments. The Private Placement Warrants were accounted for as a liability with the effect of the change in fair value of the obligation being reflected in “Loss (gain) from change in fair value of warrants” in the Consolidated Statements of Operations. See Note 8. Fair Value of Financial Instruments for details describing the valuation approach for the Private Placement Warrants as well as the impact on the Consolidated Statements of Operations for any changes in the value of the Private Placement Warrants. During 2016, 2015 and 2014, portions of the Private Placement Warrants were exercised, resulting in the issuance of 153,916 shares, 5,000 shares and 109,585 shares of the Common Stock, respectively. The unexercised Private Placement Warrants totaling 128,341 shares expired in April 2016. As of December 31, 2015 and 2014, 282,257 shares and 287,257 shares of Common Stock, respectively, remained reserved for the exercise of the Private Placement Warrants.

Stock-Based Compensation

Stock-Based Compensation	12 Months Ended
	Dec. 31, 2017
Disclosure of Compensation Related Costs, Share-based Payments [Abstract]
Stock-Based Compensation	Stock-Based Compensation The Company has the 2012 Plan, which authorizes the granting of a variety of different types of awards including, but not limited to, non-qualified stock options, incentive stock options, Stock Appreciation Rights (“SARs”), Restricted Stock Awards (“RSAs”), deferred stock and performance units to its executive officers, employees, consultants and Directors. The 2012 Plan is administered by the Compensation Committee of the Board. Under the 2012 Plan, 830,925 shares were initially made available for awards, with 700,000 additional shares added to the 2012 Plan in 2013. Forfeited shares are added back to the pool of shares available for future awards. As of December 31, 2017, the Company had 567,311 shares available for issuance of future awards. SAR Award Agreements SAR awards entitle the recipients to receive, upon exercise, a number of shares of the Common Stock equal to (i) the number of shares for which the SAR is being exercised multiplied by the value of one share of the Common Stock on the date of exercise (determined as provided in the SAR award agreement), less (ii) the number of shares for which the SAR is being exercised multiplied by the applicable exercise price, divided by (iii) by the value of one share of the Common Stock on the date of exercise (determined as provided in the SAR award agreement). The exercised SAR is to be settled only in whole shares of Common Stock, and the value of any fractional share of Common Stock is forfeited. For all SAR award assumptions, the Company used rates on the grant date of zero-coupon government bonds with maturities over periods covering the term of the awards, converted to continuously compounded forward rates. Volatility is measured as the amount by which a financial variable such as a share price is expected to fluctuate during a period. The Company considered the historical volatility of its stock price over a term similar to the expected life of the awards in determining expected volatility. The expected term is the period that the awards granted are expected to remain outstanding. The Company has never declared or paid a cash dividend on its Common Stock and has no plans to pay cash dividends in the foreseeable future. 2012 SAR award In June 2012, the Company’s then Chief Operating Officer (“COO”) was granted a SAR award (“2012 SAR award”) for 543,872 shares at a strike price per share of $22.07 . The 2012 SAR award was to vest and become exercisable ratably on each of the first three anniversaries of the grant date and had a ten -year contractual term. In addition, the SAR award included a market condition by which the SAR shares were not exercisable until the last of any seven Valuation Dates (as defined in the SAR award agreement) within any period of ten or fewer consecutive Valuation Dates that commenced after the grant date and prior to the expiration date on each of which the market value per share of Common Stock was at least $22.07 . This market condition was met during the first quarter of 2013. The fair value of the SAR award was determined using the Black-Scholes option valuation pricing model. This fair value would approximate a valuation under a Monte Carlo simulation model, as the derived service period is substantially shorter than the effective term used in the Black-Scholes model. The suggested value from the Black-Scholes method reflected a fully marketable security that was not affected by limited marketability. The Common Stock was not actively traded, and accordingly the valuation was discounted by 15% . The resulting fair value of the 2012 SAR award was $3.31 per share. The assumptions used for valuing the SARs granted in 2012 included the following: Assumptions 2012 SARs Market closing price of the Common Stock $ 16.50 Exercise price $ 22.07 Risk-free interest rate 0.92 % Expected volatility 55.0 % Expected term 6 years Dividend yield — % Total compensation expense for the 2012 SAR award was initially determined to be $1.8 million . The Company recognized expense on a straight-line basis over the requisite service period for each separately vesting portion of the award as if the award was, in substance, multiple awards (graded vesting attribution method). As the 2012 SAR award included both a market and a service condition, the Company used the longest of the periods to define its requisite service period in each separately vesting portion or tranche. Using a Monte Carlo analysis, the Company determined that 1.78 years was the likely period until the market condition would be met. As a result, compensation expense for the first tranche was computed on a straight-line basis over the derived service period of 1.78 years . The second and third tranches were computed on a straight-line basis over the explicit service periods. With the market condition being met in the first quarter of 2013, the remaining unrecognized compensation expense for the first tranche was accelerated. In June 2015, prior to the third tranche vesting, the Company and the recipient agreed to defer the vesting of the remaining 181,290 unvested SAR shares for 30 days. In July 2015, the Company and recipient entered into a SAR and Bonus Agreement, which amended the 2012 SAR award by extending the vesting period applicable to the remaining unvested SAR shares with 100,000 vesting in June 2017 and 81,290 vesting in June 2019. The SAR and Bonus Agreement also limited the sale of any vested SAR shares to no more than $0.8 million within a six -month period without the written consent of the Company’s Compensation Committee and provided the recipient with an annual bonus of $0.3 million for each of calendar years 2019, 2018, 2017 and 2016, as long as the conditions of the 2012 SAR award agreement were met, including the service conditions, and subject to forfeiture under certain circumstances enumerated in the 2012 SAR award agreement. The Company measured incremental compensation cost related to the amendment by comparing the fair value of the modified award to the fair value of the original award immediately before the modification. Primarily based on differences in risk-free interest rates, it was determined that the modification resulted in incremental compensation expense of $1.84 per SAR share, or $0.3 million in aggregate. The assumptions used for valuing the incremental compensation related to the modification included the following: Assumptions Pre-Modification Post-Modification Market closing price of the Common Stock $ 53.64 $ 51.13 Exercise price $ 22.07 $ 22.07 Risk-free interest rate 1.10 % 1.53 % Expected volatility 50.0 % 50.0 % Expected term 3.5 years 4.9 years Dividend yield — % — % Fair value of the Common Stock $ 31.97 $ 33.81 During 2013, the first tranche of 181,291 SAR shares that vested in June 2013 was exercised. During 2014, 120,000 of the 181,291 SAR shares that vested in June 2014 were exercised. In 2015 and 2014, the Company recognized compensation expense of $0.2 million and $0.3 million , respectively, in “Selling, general and administrative expenses” related to the 2012 SAR award. In the second quarter of 2016, with the recipient's termination of employment with the Company, 61,291 of unexercised SAR shares expired, 181,290 of unvested shares were forfeited, and $0.1 million of previously recognized expense, related to the incremental stock compensation expense, was reversed. 2015 SAR award In October 2015, the Company’s then Chief Financial Officer was granted a SAR award (“2015 SAR award”) for 60,000 SAR shares at a strike price per share of $24.41 . The 2015 SAR award was to vest and become exercisable with respect to one-fourth of the covered shares annually beginning on the third anniversary of the grant date. The 2015 SAR award had a ten -year contractual term. The assumptions used for valuing the SARs granted in 2015 included the following: Assumptions 2015 SARs Market closing price of the Common Stock $ 24.41 Exercise price $ 24.41 Risk-free interest rate 1.76 % Expected volatility 50.0 % Expected term 7.25 years Dividend yield — % The resulting fair value of the 2015 SAR award was $12.96 per underlying share. In 2016, the Company recognized compensation expense of $0.1 million in “Selling, general and administrative expenses” in connection with the 2015 SAR award. In 2015, the compensation expense was immaterial. In the first quarter of 2017, as a result of the resignation of the recipient, 60,000 unvested shares were forfeited, and $0.2 million of previously recognized expense was reversed. 2016 SAR awards In 2016, the Company granted 106,800 SAR awards to various employees. In February 2016, the Company initiated cost reduction efforts, which included salaried head count reductions, salaried wage reductions and hourly furlough programs. In connection with the cost reduction efforts, the Company granted 103,350 SAR awards as a retention incentive for certain employees impacted by these efforts (“February 2016 SAR awards”). The assumptions used for valuing the February 2016 SAR awards included the following: Assumptions February 2016 SAR awards Market closing price of the Common Stock $ 10.76 Exercise price $ 11.25 Risk-free interest rate 1.36 % Estimated price volatility 55.0 % Expected term 5.75 years Dividend yield — % The resulting fair value of the February 2016 SAR awards was $5.37 per underlying share. The individual SAR awards vest ratably over two years, with half of the shares becoming exercisable on each of the first two anniversaries of the grant. In 2017 and 2016, the Company recognized compensation expense of $0.2 million and $0.2 million , respectively, primarily in “Selling, general and administrative expenses” related to the February 2016 SAR award grants. The Company recognized an immaterial amount of compensation expense in 2017 and 2016, related to other 2016 SAR awards. 2017 SAR award In 2017, the Company granted 5,000 SAR awards. The assumptions used for valuing the 2017 SARs included the following: Assumptions 2017 SARs Market closing price of the Common Stock $ 7.37 Exercise price $ 7.37 Risk-free interest rate 2.1 % Estimated price volatility 58.5 % Expected term 6.00 years Dividend yield — % The resulting fair value was $4.10 per underlying share. The SAR award vests ratably over two years , with half of the shares becoming exercisable on each of the first two anniversary of the grant. In 2017, the Company recognized an immaterial amount of compensation expense related to the 2017 SAR award. SAR activity consisted of the following: Number of Shares under SARs Shares Weighted-Average Exercise Price Weighted-Average Remaining Contractual Term (years) Aggregate Intrinsic Value (in thousands) Outstanding at December 31, 2013 362,581 $ 22.07 8.44 $ 19,228 Granted — — — Exercised (120,000 ) 22.07 6,673 Forfeited — — — Expired — — — Outstanding at December 31, 2014 242,581 22.07 7.44 7,166 Exercisable at December 31, 2014 61,291 $ 22.07 7.44 $ 1,811 Number of Shares under SARs Shares Weighted-Average Exercise Price Weighted-Average Remaining Contractual Term (years) Aggregate Intrinsic Value (in thousands) Outstanding at December 31, 2014 242,581 $ 22.07 7.44 $ 7,166 Granted 60,000 24.41 — Exercised — — — Forfeited — — — Expired — — — Outstanding at December 31, 2015 302,581 22.53 7.10 — Exercisable at December 31, 2015 61,291 $ 22.07 6.44 $ — Number of Shares under SARs Shares Weighted-Average Exercise Price Weighted-Average Remaining Contractual Term (years) Aggregate Intrinsic Value (in thousands) Outstanding at December 31, 2015 302,581 $ 22.53 7.10 $ — Granted 106,800 11.43 — Exercised — — — Forfeited (195,490 ) 21.28 — Expired (61,291 ) 22.07 — Outstanding at December 31, 2016 152,600 16.55 9.02 — Exercisable at December 31, 2016 — $ — $ — Number of Shares under SARs Shares Weighted-Average Exercise Price Weighted-Average Remaining Contractual Term (years) Aggregate Intrinsic Value (in thousands) Outstanding at December 31, 2016 152,600 $ 16.55 9.02 $ — Granted 5,000 7.37 — Exercised — — — Forfeited (67,130 ) 23.16 — Expired (6,750 ) 12.68 — Outstanding at December 31, 2017 83,720 11.02 8.21 1,000 Exercisable at December 31, 2017 39,360 $ 11.25 8.15 $ — Restricted Stock Awards RSA grants represent Common Stock issued subject to forfeiture or other restrictions that will lapse upon satisfaction of specified conditions. RSAs are valued based on the fair value of the common stock at grant date, with compensation expense for recipients recognized over the vesting period based on the date of the award, primarily recognized in “Selling, general and administrative expenses.” Restricted stock activity consisted of the following: Shares Weighted-Average Grant Date Fair Value Balance as of December 31, 2013 162,993 $ 39.29 Granted 23,000 71.47 Forfeited (12,000 ) 60.44 Vested (19,742 ) 41.89 Balance as of December 31, 2014 154,251 42.11 Granted 1,000 28.48 Forfeited (800 ) 65.51 Vested (24,207 ) 42.63 Balance as of December 31, 2015 130,244 41.77 Granted 750 18.50 Forfeited (4,668 ) 36.00 Vested (21,986 ) 42.96 Balance as of December 31, 2016 104,340 41.61 Granted 437,472 8.13 Forfeited (29,144 ) 38.33 Vested (16,395 ) 44.19 Balance as of December 31, 2017 496,273 $ 12.20 In 2017, 2016, 2015 and 2014, the Company recognized $1.4 million , $1.0 million , $1.0 million and $1.0 million , respectively, of compensation expense, net of forfeitures, in connection with the RSAs. The original grant date fair value of restricted stock that vested during 2017, 2016, 2015 and 2014 was $0.7 million , $0.9 million , $1.0 million and $0.8 million , respectively, based on the value at the vesting date. Unrecognized compensation expense related to RSAs as of December 31, 2017, 2016, 2015 and 2014 was $4.6 million , $3.5 million , $4.7 million and $5.8 million , respectively. As of December 31, 2017, the weighted-average period over which the unrecognized compensation cost is expected to be recognized was approximately 3.04 years . 2017 Retention Program The restricted stock information above includes retention awards granted in July 2017. As part of the Company’s efforts to retain certain employees, 379,472 RSAs with a total market value of $2.9 million were granted along with $3.3 million of cash awards. Half of the shares granted vested in March 2018, and the second half vested in March 2019. Half of the cash awards were paid in quarterly installments commencing in July 2017, with the remaining half to be paid in 2019. Other Equity Award In 2012, the Company entered into an employment agreement that included an award of $0.5 million of restricted stock with a put option for the recipient to have the Company repurchase the related restricted stock for $2.0 million upon vesting at December 31, 2020. The Company recognized $0.4 million , $0.3 million and $0.1 million of compensation expense related to the restricted stock award in 2016, 2015 and 2014, respectively. In the first quarter of 2017, the award was forfeited, and $1.0 million of previously recognized expense was reversed.

Earnings Per Share

Earnings Per Share	12 Months Ended
	Dec. 31, 2017
Earnings Per Share [Abstract]
Earnings Per Share	Earnings Per Share The Company computes earnings per share (“EPS”) in accordance with FASB guidance. The Company computes basic earnings per share by dividing net income available to common shares by the weighted-average shares outstanding during the year. Diluted earnings per share is calculated to give effect to all potentially dilutive common shares that were outstanding during the year. Weighted-average diluted common shares outstanding primarily reflect the additional shares that would be issued upon the assumed exercise of stock options and the assumed vesting of unvested share awards. The treasury stock method has been used to compute EPS for 2017, 2016, 2015 and 2014. For 2017, the Company has recognized deemed dividends on the Series B Convertible Preferred Stock issued to Weichai and subsequently converted to Common Stock. The Company issued Private Placement Warrants that represent the right to purchase shares of Common Stock, SARs and RSAs, all of which have been evaluated for their potentially dilutive effect under the treasury stock method. See Note 12. Stockholders’ Equity for additional information of the Private Placement Warrants and Note 13. Stock-Based Compensation for additional information of the SARs and the RSAs. The computations of basic and diluted EPS were as follows: (in thousands, except per share basis) For the Year Ended December 31, 2017 2016 2015 (Restated) 2014 (Restated) Numerator: Net (loss) income $ (47,612 ) $ (47,472 ) $ (2,891 ) $ 21,477 Less: Deemed dividend on Series B convertible preferred stock (37,860 ) — — — Net (loss) income available to common stockholders - basic (85,472 ) (47,472 ) (2,891 ) 21,477 Exclude (gain) loss from change in fair value of warrants — (1,413 ) (9,300 ) (6,170 ) Net (loss) income available to common stockholders - diluted $ (85,472 ) $ (48,885 ) $ (12,191 ) $ 15,307 Denominator: Shares used in computing net (loss) income per share: Weighted-average basic shares outstanding 13,787 10,931 10,808 10,705 Effect of dilutive securities — — 183 426 Weighted-average common shares outstanding — diluted 13,787 10,931 10,991 11,131 (Loss) earnings per common share: (Loss) earnings per share — basic $ (6.20 ) $ (4.34 ) $ (0.27 ) $ 2.01 (Loss) earnings per share — diluted $ (6.20 ) $ (4.47 ) $ (1.11 ) $ 1.38 For 2017, 2016 and 2015, dilutive impacts from SAR and RSA grants were not included in the diluted EPS calculation, as they would have been anti-dilutive due to the losses reported in the Consolidated Statements of Operations. Additionally, for all periods, certain SAR grants were excluded from the diluted EPS calculation, as the Company’s average stock price was less than their respective exercise prices. For 2017, the Weichai Warrant and the Series B Convertible Preferred Stock were excluded from the diluted EPS calculation, as they would have been anti-dilutive. The aggregate shares excluded from the diluted EPS calculations, as they would have been anti-dilutive, were 6.3 million shares, 0.3 million shares and 0.1 million shares in 2017, 2016 and 2015, respectively.

Related Party Transactions

Related Party Transactions	12 Months Ended
	Dec. 31, 2017
Related Party Transactions [Abstract]
Related Party Transactions	Related Party Transactions Weichai Transactions See Note 3. Weichai Transactions for information regarding the Weichai SPA and collaboration arrangement . 3PI Lease Agreement In connection with the acquisition of 3PI, the Company entered into a lease agreement effective April 1, 2014, with a limited liability company in which one of the former owners of 3PI is the sole member. The lease is for the land, buildings and certain equipment located at 3PI’s facilities in Darien, Wisconsin. The lease expires on March 31, 2021. In 2017, 2016, 2015 and 2014, the Company recognized expense of $0.5 million , $0.5 million , $0.5 million and $0.4 million , respectively, in connection with this lease. See Note 5. Acquisitions for additional information on this acquisition. The former 3PI owner is no longer employed by the Company and is no longer a related party. Transactions with Joint Ventures MAT-PSI Holdings, LLC On December 7, 2012, the Company and MAT Holdings, Inc. (“MAT”) entered into an agreement to create MAT-PSI Holdings, LLC (“MAT-PSI”), which was intended to be a holding company of its 100% Chinese wholly-owned foreign entity, referred to as Green Power. The Company invested $0.9 million for its 50% share of MAT-PSI, which was formed to manufacture, assemble and supply natural gas, gas and alternative-fueled power systems to Chinese and Asian forklift customers. The venture established a production facility in Dalian and also sourced base engines from a local Chinese factory. As MAT-PSI was not profitable, the venture was closed in 2017. The Company’s investment was accounted for under the equity method of accounting. Doosan-PSI, LLC In 2015, the Company and Doosan Infracore Co., Ltd. (“Doosan”), a subsidiary of Doosan Group, entered into an agreement to form Doosan-PSI, LLC. The Company invested $1.0 million to acquire 50% of the venture, which was formed to operate in the field of developing, designing, testing, manufacturing, assembling, branding, marketing, selling, distributing and providing support for industrial gas engines and all components and materials required for assembly of the gas engines to the global power generation market outside of North America and South Korea. Sterling and Wilson Cogen Solutions, LLC On April 13, 2016, the Company and Sterling and Wilson Power Systems Inc. (“SW”) entered into an agreement for the formation and operation of Sterling and Wilson Cogen Solutions, LLC. The Company invested $0.2 million for its 49% share of the venture. Effective May 31, 2017, the Company sold its 49% membership interest in the venture to SW for $0.2 million pursuant to the agreement. Joint Venture Operating Results The Company's Consolidated Statements of Operations included losses of $0.4 million , $0.1 million and a gain of $0.3 million presented in “Other income (expense), net” in 2016, 2015 and 2014, respectively, for these ventures. In 2017, the gain was immaterial. Transactions with Related Individuals William D. Winemaster William D. Winemaster, the father of Gary S. Winemaster, former Chairman of the Board, Chief Executive Officer and President and nonexecutive Chief Strategy Officer, and Kenneth J. Winemaster, Executive Vice President, served as an employee performing consulting and advisory-type services, for which he was paid a salary, an amount for automobiles and related insurance premiums, mobile-telephone services and a bonus. The Company paid to William D. Winemaster $0.2 million in each of the years 2017, 2016, 2015 and 2014.

Selected Quarterly Financial Da

Selected Quarterly Financial Data (Unaudited)	12 Months Ended
	Dec. 31, 2017
Quarterly Financial Information Disclosure [Abstract]
Selected Quarterly Financial Data (Unaudited)	Selected Quarterly Financial Data (Unaudited) Set forth below is unaudited quarterly financial data for 2017 and 2016. POWER SOLUTIONS INTERNATIONAL, INC. CONDENSED CONSOLIDATED BALANCE SHEETS (in thousands) As of March 31, 2017 June 30, September 30, 2017 ASSETS Current assets Cash and cash equivalents $ 342 $ — $ — Accounts receivable, net 64,305 56,673 60,811 Income tax receivable 6,829 1,996 841 Inventories, net 97,286 103,335 113,074 Prepaid expenses and other current assets 15,291 12,453 14,536 Total current assets 184,053 174,457 189,262 Property, plant and equipment, net 19,230 19,050 18,974 Intangible assets, net 24,819 23,610 22,401 Goodwill 29,835 29,835 29,835 Other noncurrent assets 5,053 4,518 6,035 TOTAL ASSETS $ 262,990 $ 251,470 $ 266,507 LIABILITIES, MEZZANINE AND STOCKHOLDERS’ EQUITY Current liabilities Accounts payable $ 67,167 $ 55,610 $ 54,195 Contingent consideration 30 29 20 Revolving line of credit, current 16,887 25,263 41,332 Other accrued liabilities 35,234 35,379 41,393 Total current liabilities 119,318 116,281 136,940 Deferred income taxes 933 1,066 1,210 Warrants 20,700 21,500 23,200 Long-term debt, less current maturities, net 54,045 54,168 54,305 Other noncurrent liabilities 13,328 12,438 13,312 TOTAL LIABILITIES $ 208,324 $ 205,453 $ 228,967 MEZZANINE EQUITY Series B convertible preferred stock, net of issuance costs $ 24,617 $ 27,807 $ 31,411 STOCKHOLDERS’ EQUITY Preferred stock $ — $ — $ — Common stock 14 14 14 Additional paid-in capital 100,686 96,543 91,737 Accumulated deficit (59,070 ) (66,817 ) (76,018 ) Treasury stock, at cost (11,582 ) (11,530 ) (9,604 ) TOTAL STOCKHOLDERS’ EQUITY 30,048 18,210 6,129 TOTAL LIABILITIES, MEZZANINE AND STOCKHOLDERS’ EQUITY $ 262,990 $ 251,470 $ 266,507 POWER SOLUTIONS INTERNATIONAL, INC. CONDENSED CONSOLIDATED BALANCE SHEETS (in thousands) As of March 31, 2016 (Restated) June 30, September 30, 2016 ASSETS Current assets Cash and cash equivalents $ 1,495 $ 435 $ 1,610 Accounts receivable, net 45,384 57,884 53,364 Income tax receivable 1,723 3,384 5,737 Inventories, net 139,519 115,062 111,133 Prepaid expenses and other current assets 4,132 4,026 5,146 Total current assets 192,253 180,791 176,990 Property, plant and equipment, net 20,662 20,386 20,257 Intangible assets, net 30,316 28,888 27,459 Goodwill 29,835 29,835 29,835 Deferred income taxes 19,285 — — Other noncurrent assets 2,664 2,621 2,821 TOTAL ASSETS $ 295,015 $ 262,521 $ 257,362 LIABILITIES AND STOCKHOLDERS’ EQUITY Current liabilities Accounts payable $ 43,160 $ 49,729 $ 45,764 Current maturities of long-term debt — — 375 Contingent consideration 5,481 100 88 Revolving line of credit, current — 14,038 16,994 Other accrued liabilities 17,929 19,182 22,405 Total current liabilities 66,570 83,049 85,626 Revolving line of credit 80,568 — — Deferred income taxes — 372 522 Warrants 226 — — Long-term debt, less current maturities, net 53,799 110,929 111,517 Other noncurrent liabilities 11,952 12,833 12,730 TOTAL LIABILITIES $ 213,115 $ 207,184 $ 210,395 STOCKHOLDERS’ EQUITY Preferred stock $ — $ — $ — Common stock 11 12 12 Additional paid-in capital 83,729 86,043 86,408 Retained earnings (accumulated deficit) 9,612 (19,180 ) (27,895 ) Treasury stock, at cost (11,452 ) (11,537 ) (11,558 ) TOTAL STOCKHOLDERS’ EQUITY 81,900 55,337 46,967 TOTAL LIABILITIES AND STOCKHOLDERS’ EQUITY $ 295,015 $ 262,521 $ 257,362 POWER SOLUTIONS INTERNATIONAL, INC. CONDENSED CONSOLIDATED STATEMENTS OF OPERATIONS (in thousands, except per share amounts) For the Quarter Ended March 31, 2017 June 30, 2017 September 30, 2017 December 31, 2017 Net sales $ 84,265 $ 100,922 $ 99,953 $ 131,476 Cost of sales 74,497 88,443 86,702 115,981 Gross profit 9,768 12,479 13,251 15,495 Operating expenses: Research, development and engineering expenses 3,950 3,848 5,687 6,459 Selling, general and administrative expenses 10,209 10,688 12,062 11,297 Asset impairment charges — — — 1 Amortization of intangible assets 1,209 1,209 1,210 1,210 Total operating expenses 15,368 15,745 18,959 18,967 Operating loss (5,600 ) (3,266 ) (5,708 ) (3,472 ) Other expense: Interest expense 6,080 1,404 1,654 1,703 Loss from change in fair value of warrants — 800 1,700 1,500 Loss on debt extinguishment and modifications 11,921 — — — Other expense (income), net 453 2,142 (9 ) (225 ) Total other expense 18,454 4,346 3,345 2,978 Loss before income taxes (24,054 ) (7,612 ) (9,053 ) (6,450 ) Income tax expense (benefit) 479 135 149 (320 ) Net loss (24,533 ) (7,747 ) (9,202 ) (6,130 ) Deemed dividend on Series B convertible stock — (3,190 ) (3,603 ) (31,067 ) Net loss available to common stockholders $ (24,533 ) $ (10,937 ) $ (12,805 ) $ (37,197 ) POWER SOLUTIONS INTERNATIONAL, INC. CONDENSED CONSOLIDATED STATEMENTS OF OPERATIONS (in thousands, except per share amounts) For the Quarter Ended March 31, 2016 (Restated) June 30, 2016 September 30, 2016 December 31, 2016 Net sales $ 76,470 $ 85,771 $ 78,944 $ 98,280 Cost of sales 69,827 81,253 72,820 86,376 Gross profit 6,643 4,518 6,124 11,904 Operating expenses: Research, development and engineering expenses 4,904 4,817 4,498 4,742 Selling, general and administrative expenses 6,405 6,699 6,855 8,563 Asset impairment charges 345 1,064 38 167 Amortization of intangible assets 1,428 1,429 1,429 1,430 Contingent consideration — (283 ) — — Total operating expenses 13,082 13,726 12,820 14,902 Operating loss (6,439 ) (9,208 ) (6,696 ) (2,998 ) Other expense: Interest expense 1,438 1,649 3,726 4,402 Gain from change in fair value of warrants (1,256 ) (157 ) — — Loss on debt extinguishment and modifications — — 25 332 Other expense, net 59 92 62 146 Total other expense 241 1,584 3,813 4,880 Loss before income taxes (6,680 ) (10,792 ) (10,509 ) (7,878 ) Income tax (benefit) expense (3,357 ) 18,000 (1,792 ) (1,238 ) Net loss $ (3,323 ) $ (28,792 ) $ (8,717 ) $ (6,640 ) POWER SOLUTIONS INTERNATIONAL, INC. CONDENSED CONSOLIDATED STATEMENTS OF CASH FLOWS (in thousands) For the Year to Date Period Ended March 31, 2017 June 30, September 30, 2017 Cash provided by (used in) operating activities Net loss $ (24,533 ) $ (32,280 ) $ (41,482 ) Adjustments to reconcile net (loss) income to net cash provided by operating activities: Amortization of intangible assets 1,209 2,419 3,628 Depreciation 1,172 2,342 3,502 Change in valuation of warrants — 800 2,500 Stock compensation expense (865 ) (1,028 ) (297 ) Amortization of financing fees 3,109 3,441 3,778 Deferred income taxes 469 602 746 Loss on extinguishment of debt 11,921 11,921 11,921 Provision for doubtful accounts 48 131 216 Provision for inventory obsolescence 146 539 882 Loss on disposal of fixed assets 10 66 115 Other sources, net 135 198 189 Changes in operating assets and liabilities: Trade accounts receivable, net (4,017 ) 3,532 (691 ) Inventory, net 3,122 (3,326 ) (13,408 ) Prepaid expenses and other assets (1,624 ) 1,238 (1,359 ) Trade accounts payable 15,186 3,244 1,879 Income taxes refundable 298 5,135 6,293 Accrued expenses 2,432 3,242 8,867 Other noncurrent liabilities (121 ) (894 ) (821 ) Net cash provided by (used in) operating activities 8,097 1,322 (13,542 ) Cash (used in) provided by investing activities Capital expenditures (1,896 ) (2,669 ) (3,856 ) Other sources, net — 245 245 Net cash used in investing activities (1,896 ) (2,424 ) (3,611 ) Cash (used in) provided by financing activities Repayments of issuance of long-term debt (71,400 ) (71,400 ) (71,400 ) Financing fees (253 ) (928 ) (928 ) Net proceeds from stock offering and warrant 59,396 59,396 59,396 Proceeds from revolving line of credit 85,945 209,082 324,416 Repayments of revolving line of credit (81,833 ) (196,593 ) (295,859 ) Acquisition of businesses contingent consideration payments (6 ) (9 ) (19 ) Other uses, net — (738 ) (745 ) Net cash (used in) provided by financing activities (8,151 ) (1,190 ) 14,861 Decrease in cash (1,950 ) (2,292 ) (2,292 ) Cash at beginning of the year 2,292 2,292 2,292 Cash at end of the period $ 342 $ — $ — POWER SOLUTIONS INTERNATIONAL, INC. CONDENSED CONSOLIDATED STATEMENTS OF CASH FLOWS (in thousands) For the Year to Date Period Ended March 31, 2016 (Restated) June 30, September 30, 2016 Cash provided by (used in) operating activities Net loss $ (3,323 ) $ (32,115 ) $ (40,832 ) Adjustments to reconcile net (loss) income to net cash provided by operating activities: Amortization of intangible assets 1,429 2,857 4,286 Depreciation 1,118 2,250 3,412 Change in valuation of warrants (1,256 ) (1,413 ) (1,413 ) Stock compensation expense 441 692 1,188 Amortization of financing fees 143 445 1,451 Deferred income taxes (1,628 ) 18,029 18,179 Loss on extinguishment of debt — — 25 Asset impairment charges 345 1,410 1,447 Change in valuation of contingent consideration — (283 ) (283 ) (Income) provision for doubtful accounts (10 ) 24 69 Provision for inventory obsolescence 288 3,441 3,928 Loss (gain) on disposal of fixed assets 236 (852 ) (846 ) Other sources, net 113 205 266 Changes in operating assets and liabilities: Trade accounts receivable, net 25,158 12,624 17,100 Inventory, net 22,288 42,947 46,390 Prepaid expenses and other assets (207 ) (1,261 ) (2,443 ) Trade accounts payable (36,459 ) (30,324 ) (34,056 ) Income taxes refundable (payable) 3,441 1,783 (682 ) Accrued expenses 1,891 3,041 6,099 Other noncurrent liabilities (98 ) 1,011 1,028 Net cash provided by operating activities 13,910 24,511 24,313 Cash flows from investing activities Capital expenditures (1,099 ) (1,977 ) (3,286 ) Proceeds from disposal of assets — 2,466 2,466 Other uses, net — — (245 ) Net cash (used in) provided by investing activities (1,099 ) 489 (1,065 ) Cash flows from financing activities Proceeds from issuance of long-term debt — 60,000 60,000 Financing fees — (3,402 ) (3,402 ) Net proceeds from stock offering and warrant — 2,001 2,001 Proceeds from revolving line of credit 46,902 111,902 196,179 Repayments of revolving line of credit (63,634 ) (195,164 ) (276,484 ) Acquisition of businesses contingent consideration payments (3,029 ) (8,258 ) (8,279 ) Other uses, net — (89 ) (98 ) Net cash used in financing activities (19,761 ) (33,010 ) (30,083 ) Decrease in cash (6,950 ) (8,010 ) (6,835 ) Cash at beginning of the year 8,445 8,445 8,445 Cash at end of the period $ 1,495 $ 435 $ 1,610 EFFECT OF RESTATEMENT The restatement adjustments identified in the three months ended March 31, 2016 were similar in nature to those described in Note 2. Restatement of Previously Issued Consolidated Financial Statements and arose during the Company's comprehensive internal review of its accounting practices as well as its previously issued consolidated financial statements. The Company identified the following categories that required restatement or reclassification and were comprised of a number of related adjustments that have been aggregated for disclosure purposes: (in thousands) Three Months Ended March 31, 2016 Net Sales (Loss) Income Before Income Taxes Previously Reported $ 61,814 $ (8,931 ) Restatement adjustments: Revenue recognition adjustments $ 14,656 $ 3,111 Product development cost — 123 Inventory valuation — (404 ) Impairment of long-lived assets — (557 ) Product warranty — (319 ) Accrued liabilities — 422 Equity investment — (125 ) Net restatement adjustments 14,656 2,251 Restated $ 76,470 $ (6,680 ) The following table presents the effect of the restatement adjustments and reclassifications on the Consolidated Statement of Operations for three months ended March 31, 2016: (in thousands, except for per share data) Three Months Ended March 31, 2016 Previously Reported Restatement Adjustments and Reclassifications Restated Net sales $ 61,814 $ 14,656 $ 76,470 Cost of sales 57,758 12,069 69,827 Gross profit 4,056 2,587 6,643 Operating expenses: Research, development and engineering expenses 5,250 (346 ) 4,904 Selling, general and administrative expenses 6,058 347 6,405 Asset impairment charge — 345 345 Amortization of intangible assets 1,429 (1 ) 1,428 Total operating expenses 12,737 345 13,082 Operating loss (8,681 ) 2,242 (6,439 ) Other expense (income): Interest expense 1,421 17 1,438 Private placement warrants income (1,256 ) — (1,256 ) Other expense, net 85 (26 ) 59 Total other expense 250 (9 ) 241 Loss before income taxes (8,931 ) 2,251 (6,680 ) Income tax benefit (3,680 ) 323 (3,357 ) Net loss $ (5,251 ) $ 1,928 $ (3,323 ) Weighted-average common shares outstanding: Basic 10,819 — 10,819 Diluted 10,819 — 10,819 (Loss) earnings per common share: Basic $ (0.49 ) $ 0.07 $ (0.42 ) Diluted $ (0.49 ) $ 0.07 $ (0.42 ) as of March 31, 2016: (in thousands) As of March 31, 2016 Previously Reported Restatement Adjustments and Reclassifications Restated ASSETS Current assets Cash and cash equivalents $ 1,495 $ — $ 1,495 Accounts receivable, net 63,163 (17,779 ) 45,384 Income tax receivable — 1,723 1,723 Inventories, net 120,735 18,784 139,519 Prepaid expenses and other current assets 9,496 (5,364 ) 4,132 Total current assets 194,889 (2,636 ) 192,253 Property, plant and equipment, net 24,289 (3,627 ) 20,662 Intangible assets, net 30,316 — 30,316 Goodwill 41,466 (11,631 ) 29,835 Deferred income taxes 819 18,466 19,285 Other noncurrent assets 7,181 (4,517 ) 2,664 TOTAL ASSETS $ 298,960 $ (3,945 ) $ 295,015 LIABILITIES AND STOCKHOLDERS’ EQUITY Current liabilities Accounts payable $ 41,491 $ 1,669 $ 43,160 Contingent consideration — 5,481 5,481 Other accrued liabilities 19,692 (1,763 ) 17,929 Total current liabilities 61,183 5,387 66,570 Revolving line of credit 80,568 — 80,568 Warrants 226 — 226 Long-term debt, less current maturities, net 53,946 (147 ) 53,799 Other noncurrent liabilities 1,670 10,282 11,952 TOTAL LIABILITIES $ 197,593 $ 15,522 $ 213,115 STOCKHOLDERS’ EQUITY Preferred stock $ — $ — $ — Common stock 12 (1 ) 11 Additional paid-in capital 75,500 8,229 83,729 Retained earnings 30,105 (20,493 ) 9,612 Treasury stock, at cost (4,250 ) (7,202 ) (11,452 ) TOTAL STOCKHOLDERS’ EQUITY 101,367 (19,467 ) 81,900 TOTAL LIABILITIES AND STOCKHOLDERS’ EQUITY $ 298,960 $ (3,945 ) $ 295,015 The restatement effect on the previously issued condensed Consolidated Statement of Cash Flow for the three months ended March 31, 2016 is as follows: (in thousands) Three Months Ended March 31, 2016 Previously Reported Restatement and Reclassification Reclassified Net cash provided by operating activities $ 9,995 $ 3,915 $ 13,910 Net cash used in investing activities (214 ) (885 ) (1,099 ) Net cash used in financing activities (16,731 ) (3,030 ) (19,761 ) Decrease in cash (6,950 ) — (6,950 ) Cash at beginning of year 8,445 — 8,445 Cash at end of period $ 1,495 $ — $ 1,495 The primary reclassification moved payment of contingent consideration to financing from operating.

Subsequent Events

Subsequent Events	12 Months Ended
	Dec. 31, 2017
Subsequent Events [Abstract]
Subsequent Events	Subsequent Events In April 2018, the Company finalized the purchase of emissions testing assets and the sublease of an emissions testing facility from Ricardo, Inc., a subsidiary of the strategic engineering and environmental consultancy, Ricardo Plc., for $5.6 million in cash. The acquisition strategically expands and strengthens the Company’s R&D and testing capabilities.

Summary of Significant Accoun_2

Summary of Significant Accounting Policies and Other Information (Policies)	12 Months Ended
	Dec. 31, 2017
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Basis of Presentation and Consolidation	Basis of Presentation and Consolidation The Company is filing this Annual Report on Form 10-K for the year ended December 31, 2017, which contains audited consolidated financial statements as of and for the years ended December 31, 2017, 2016, 2015 and 2014. The consolidated financial statements for 2015 and 2014 included herein restate and replace the Company's previously issued audited annual consolidated financial statements, which were filed with the United States Securities and Exchange Commission (the “SEC”). Accordingly, investors should rely only on the financial information and other disclosures regarding the Company's consolidated financial statements in this Form 10-K or in future filings with the SEC, as applicable, and not on any previously issued or filed reports, earnings releases or similar communications relating to these periods. See Note 2. Restatement of Previously Issued Consolidated Financial Statements for additional information regarding the restatement adjustments for 2015 and 2014. The consolidated financial statements include the accounts of Power Solutions International, Inc. and its wholly-owned subsidiaries. The Company's Consolidated Financial Statements were prepared in accordance with generally accepted accounting principles in the United States (“U.S. GAAP”) and include the assets, liabilities, sales and expenses of all wholly-owned subsidiaries and majority-owned subsidiaries in which the Company exercises control. All intercompany balances and transactions have been eliminated in consolidation. The Company operates as one business and geographic operating segment. Operating segments are defined as components of a business that can earn revenues and incur expenses for which discrete financial information is available that is evaluated on a regular basis by the chief operating decision maker (“CODM”). The Company’s CODM is its principal executive officer, who decides how to allocate resources and assess performance. A single management team reports to the CODM, who manages the entire business. The Company’s CODM reviews Consolidated Statements of Operations to make decisions, allocate resources and assess performance, and the CODM does not evaluate the profit or loss from any separate geography or product line.
Use of Estimates	Use of Estimates The preparation of consolidated financial statements in conformity with U.S. GAAP requires that management make estimates and assumptions that affect the reported amounts of assets and liabilities and disclosure of contingent assets and liabilities at the date of the consolidated financial statements and the reported amounts of revenue and expenses during the reporting period. Significant estimates and assumptions include the valuation of allowances for uncollectible receivables, inventory reserves, warranty reserves, stock-based compensation, evaluation of goodwill, plant and equipment for impairment, and determination of useful lives of long-lived assets. Actual results could materially differ from those estimates. Reclassifications Certain amounts recorded in the prior-period consolidated financial statements presented have been reclassified to conform to the current-period financial statement presentation. These reclassifications had no effect on previously reported results of operations.
Cash and Cash Equivalents	Cash and Cash Equivalents Cash equivalents consist of short-term, highly liquid investments that mature within three months or less. Such investments are stated at cost, which approximates fair value. The Company's revolving credit agreement currently includes a “lockbox” arrangement that receives all receipts and from which the Company can request increases in the revolver borrowings.
Stock-Based Compensation	Stock-Based Compensation The Company accounts for stock-based compensation expense based on the grant date fair value on the award with the cost recognized over the requisite service period, which is generally the vesting period of the respective award.
Research and Development	Research and Development Research and development (“R&D”) expenses are expensed when incurred. R&D expenses consist primarily of wages, materials, testing and consulting related to the development of new engines, parts and applications.
Income Taxes	Income Taxes The Company accounts for income taxes under the asset and liability method, which requires the recognition of deferred tax assets and liabilities for the expected future tax consequences of events that have been included in the financial statements. Under this method, deferred tax assets and liabilities are determined based on the differences between the financial statement and tax basis of assets and liabilities using enacted tax rates in effect for the year in which the differences are expected to be settled or realized. The effect of a change in tax rates on deferred tax assets and liabilities is recognized in income in the period that includes the enactment date. The Company records net deferred tax assets to the extent that it believes these assets will more likely than not be realized. In making such a determination, the Company considers all available positive and negative evidence, including future reversals of existing taxable temporary differences, projected future taxable income, tax-planning strategies and results of recent operations. As of December 31, 2017 and 2016, the Company had a valuation allowance of $32.0 million and $26.8 million , respectively. There was no valuation allowance recorded in 2015 or 2014. The Company records uncertain tax positions in accordance with accounting guidance, on the basis of a two-step process whereby (i) it determines whether it is more likely than not that the tax positions will be sustained based on the technical merits of the position and (ii) for those tax positions that meet the more-likely-than-not recognition threshold, the Company recognizes the largest amount of tax benefit that is greater than 50 percent likely to be realized upon ultimate settlement with the related tax authority. Tax benefits related to uncertain tax positions taken or expected to be taken on a tax return are recorded when such benefits meet a more-likely-than-not threshold. Otherwise, these tax benefits are recorded when a tax position has been effectively settled, which means that the appropriate taxing authority has completed its examination even though the statute of limitations remains open, or the statute of limitation has expired. Interest and penalties related to uncertain tax positions are recognized as part of income tax expense and are accrued beginning in the period that such interest and penalties would be applicable under relevant tax law until such time that the related tax benefits are recognized. As of December 31, 2017, 2016, 2015 and 2014, the Company had an unrecognized tax benefit of $1.3 million , $1.2 million , $1.3 million and $0.9 million , respectively, for uncertain tax positions excluding interest and penalties. The Company recognizes interest and penalties related to unrecognized tax benefits in income tax expense. On December 22, 2017, the President of the United States signed into law the Tax Cuts and Jobs Act (the “Tax Act”). The Tax Act includes a number of changes to existing U.S. tax laws that impact the Company, most notably a reduction of the U.S. corporate income tax rate from 34 percent to 21 percent for tax years beginning after December 31, 2017. The Tax Act also provides for the acceleration of depreciation for certain assets placed into service after September 27, 2017 as well as prospective changes beginning in 2018, including repeal of the domestic manufacturing deduction and additional limitations on executive compensation. The Company recognized the income tax effects of the Tax Act in its 2017 financial statements. The Company has analyzed the Tax Act, and remeasurement of U.S. deferred tax balances to reflect the new U.S. corporate income tax rate has been made.
Accounts Receivable and Allowance for Doubtful Accounts	Accounts Receivable and Allowance for Doubtful Accounts Trade accounts receivable represent amounts billed to customers and not yet collected. Trade accounts receivable are recorded at the invoiced amount, which approximates net realizable value, and generally do not bear interest. The allowance for doubtful accounts is the Company’s best estimate of the amount of probable credit losses in the existing accounts receivable and is established through a charge to “Selling, general and administrative expenses.” The allowance is primarily determined based on historical collection experience and reviews of customer creditworthiness. Trade accounts receivable and the allowance for doubtful accounts are reviewed on a regular basis. When necessary, an allowance for the full amount of specific accounts deemed uncollectable is recorded. Accounts receivable losses are deducted from the allowance and the account balance is written off when the customer receivable is deemed uncollectable. Recoveries of previously written off balances are recognized when received. An allowance associated with anticipated future sales returns is also included in the allowance for doubtful accounts.
Insurance Recoveries	Insurance Recoveries The Company records insurance recoveries related to amounts recorded as estimated losses on events covered by the Company's insurance policies when management determines that the recovery is probable and the amount can be reasonably determined.
Inventories	Inventories Inventories are stated at the lower of cost or net realizable value, which approximates current replacement cost. Cost is principally determined using the first-in, first-out method and includes material, labor and manufacturing overhead. It is the Company’s policy to review inventories on a continuing basis for obsolete, excess and slow-moving items and to record valuation adjustments for such items in order to eliminate non-recoverable costs from inventory. Valuation adjustments are recorded in an inventory reserve account and reduce the cost basis of the inventory in the period in which the reduced valuation is determined. Inventory reserves are established based on quantities on hand, usage and sales history, customer orders, projected demand and utilization within a current or future power system. Specific analysis of individual items or groups of items is performed based on these same criteria, as well as on changes in market conditions or any other identified conditions.
Property, Plant and Equipment	Property, Plant and Equipment Property, plant and equipment are carried at cost and presented net of accumulated depreciation and impairments. Depreciation is computed using the straight-line method over the estimated useful lives of the assets. Property, plant and equipment are evaluated periodically to determine if an adjustment to depreciable lives is warranted. Such evaluation is based principally on the expected utilization of the long-lived assets. Repairs and maintenance costs are charged directly to expense as incurred. Major renewals or replacements that substantially extend the useful life of an asset are capitalized and depreciated. Estimated useful lives by each type of asset category are as follows: Years Buildings Up to 39 Leasehold improvements Lesser of (i) expected useful life of improvement or (ii) life of lease (including likely extension thereof) Machinery and equipment 1 to 10
Intangible Assets	Intangible Assets The Company’s intangible assets include backlog, customer relationships, developed technology, trade names and trademarks. Intangible assets are amortized on an accelerated basis over a period of time that approximates the pattern over which the Company expects to gain the estimated economic benefits, and such period generally ranges between three months and 15 years . The useful life of intangible assets is assessed and assigned based on the facts and circumstances specific to the acquisition.
Impairment of Long-lived assets	Impairment of Long-lived assets The Company assesses potential impairments to its long-lived assets or asset groups, excluding goodwill, which is separately tested for impairment, whenever events indicate that the carrying amount of such assets may not be recoverable. Long-lived assets are evaluated for impairment by comparing the carrying value of the asset or asset group with the estimated future net undiscounted cash flows expected to result from the use of the asset or asset group, including cash flows from disposition. If the future net undiscounted cash flows are less than the carrying value, an impairment loss is calculated. An impairment loss is determined by the amount that the asset’s or asset group’s carrying value exceeds its estimated fair value. Estimated fair value is generally measured by discounting estimated future cash flows. If an impairment loss is recognized, the adjusted balance becomes the new cost basis and is depreciated (amortized) over the remaining useful life. The Company also periodically reassesses the useful lives of its long-lived assets due to advances and changes in technologies.
Goodwill	Goodwill Goodwill represents the excess of the cost of an acquired business over the amounts assigned to the net acquired assets. Goodwill is not amortized but is tested for impairment at the reporting unit level, on an annual basis or more frequently, if events occur or circumstances change indicating potential impairment. The Company annually tests goodwill for impairment on October 1st. In evaluating goodwill for impairment, the Company may first assess qualitative factors to determine whether it is more likely than not (i.e., there is a likelihood of more than 50%) that the Company's fair value is less than its carrying amount. Qualitative factors that the Company considers include, but are not limited to, macroeconomic and industry conditions, overall financial performance and other relevant entity-specific events. If the Company bypasses the qualitative assessment, or if the Company concludes that it is more likely than not that the fair value of a reporting unit is less than its carrying value, then the Company performs a two-step goodwill impairment test to identify potential goodwill impairment and measures the amount of goodwill impairment it will recognize, if any. In the first step of the two-step goodwill impairment test, the Company compares the estimated fair value of the reporting unit with its related carrying value. The Company has had two reporting units since 2014: PSI and Professional Power Products, Inc. (“3PI”). If the estimated fair value exceeds the carrying amount, no further analysis is needed. If, however, the reporting unit's estimated fair value is less than its carrying amount, the Company proceeds to the second step and calculates the implied fair value of goodwill to determine whether any impairment is required. The Company calculates its estimated fair value using the income and market approaches when feasible, or an asset approach when neither the income nor the market approach has sufficient data. For the income approach, a discounted cash flow method, the Company uses internally developed discounted cash flow models that include the following assumptions, among others: projections of revenues, expenses and related cash flows based on assumed long-term growth rates and demand trends, expected future investments to grow new units, and estimated discount rates. The Company based these assumptions on its historical data and experience, third-party appraisals, industry projections, and micro and macro general economic condition projections and expectations. The market approach, also called the Guideline Public Company Approach, compares the value of an entity to similar publicly traded companies. The asset approach estimates the selling price the unit could achieve under assumed market conditions. If the fair value of a reporting unit exceeds its carrying amount, goodwill of the reporting unit is considered not impaired, and the second step of the impairment test is unnecessary. If the carrying amount of a reporting unit exceeds its fair value, the second step of the goodwill impairment test is performed to measure the amount of impairment loss, if any. The second step compares the implied fair value of the reporting unit goodwill with the carrying amount of that goodwill. If the carrying amount of reporting unit goodwill exceeds the implied fair value of that goodwill, an impairment loss is recognized in an amount equal to that excess.
Warranty Costs	arranty Costs The Company offers a standard limited warranty on the workmanship of its products that in most cases covers defects for a defined period. Warranties for certified emission products are mandated by the U.S. Environmental Protection Agency (the “EPA”) and/or the California Air Resources Board (the “CARB”) and are longer than the Company’s standard warranty on certain emission related products. The Company’s products also carry limited warranties from suppliers. Costs related to supplier warranty claims are borne by the supplier; the Company’s warranties apply only to the modifications made to supplier base products. Warranty estimates are based on historical experience and represent the projected cost associated with the product. A liability and related expense are recognized at the time products are sold. The Company adjusts estimates when it is determined that actual costs may differ from initial or previous estimates.
Revenue Recognition	Revenue Recognition As of December 31, 2017, the Company recognizes revenue upon transfer of title and risk of loss to the customer, typically when products are shipped, provided there is persuasive evidence of an arrangement, the sales price is fixed or determinable, and management believes collectability is reasonably assured. Customer orders sometimes include multiple products that are delivered at different times. In these situations, revenue associated with the delivered components is recognized under the guidance of Financial Accounting Standards Board (“FASB”) Accounting Standards Codification (“ASC”) 605-25, Revenue Recognition Multiple-Element Arrangements , which considers whether products represent separate deliverables with stand-alone value. For discussion of the impact to revenue recognition resulting from the new revenue guidance, FASB ASC Topic 606, Revenue from Contracts with Customers , effective January 1, 2018, see the Recently Issued Accounting Pronouncements Not Yet Adopted section below. The Company classifies shipping and handling charges billed to customers as revenue. Shipping and handling costs paid to others are classified as a component of cost of sales when incurred. The Company provides various sales incentives to its customers, including rebate opportunities and price incentives for attaining specified volumes during a particular quarter or year. The Company accrues for the expected amount of these sales incentives as a reduction of revenue at the time of the original sale and updates its accruals as needed based on the best estimate of the volume levels the customer will reach during the measurement period. Historically, the Company has often, late in a fiscal quarter, offered to certain customers various incentives, such as extended payment terms or discounts, primarily in an effort to increase customer's orders during the period and achieve sales target goals. The Company also from time to time offers incentives with respect to the launch of new products.
Recently Issued Accounting Pronouncements - Adopted and Not Yet Adopted	Recently Issued Accounting Pronouncements - Adopted In August 2016, the FASB issued Accounting Standards Update (“ASU”) 2016-15, Statement of Cash Flows (Topic 230), Classification of Certain Cash Receipts and Cash Payments. This guidance specified cash flow statement classification of, among other things, debt prepayment or extinguishment costs, contingent consideration payments made after a business combination, proceeds from the settlement of insurance claims, proceeds from the settlement of corporate-owned life insurance policies, and distributions received from equity method investees. This guidance is effective for periods beginning after December 15, 2017, with early adoption permitted. The Company had adopted this guidance and applied it retrospectively to all periods presented. In March 2016, the FASB issued ASU 2016-09, Improvements to Employee Share-Based Payment Accounting (Topic 718). The ASU simplifies several aspects of the accounting for stock-based compensation transactions, including accounting for income taxes, forfeitures and statutory withholding requirements, as well as classification in the consolidated statements of cash flows. The ASU was effective for financial statements issued for fiscal years beginning after December 15, 2016 and interim periods within those fiscal years, with early adoption permitted. The Company adopted the new standard during the second quarter of 2016, with an effective date of January 1, 2016, which did not a have a significant impact on the Consolidated Balance Sheets or Consolidated Statements of Operations. Historically, these amounts were recorded as “Additional paid-in capital.” The Company also elected to apply the change prospectively to the Consolidated Statements of Cash Flows. As a result, on a prospective basis, share-based payments will be reported as operating activities in the Consolidated Statements of Cash Flows. The Company elected to recognize forfeitures as they occur. Additional amendments to the accounting for income taxes and minimum statutory withholding requirements had no impact on the results of operations. In January 2016, the FASB issued ASU 2016-01, Financial Instruments, Recognition and Measurement of Financial Assets and Financial Liabilities. This guidance requires disclosures to compare carrying values to fair values of financial assets and liabilities, with some exceptions. This guidance is effective for annual and interim periods in 2018 but was early adopted by the Company on January 1, 2017. The adoption of this ASU did not have an impact on the Consolidated Balance Sheets or the Consolidated Statements of Operations. In November 2015, the FASB issued ASU 2015-17, Income Taxes (Topic 740): Balance Sheet Classification of Deferred Taxes, which required companies to classify all deferred tax assets and liabilities as noncurrent on the consolidated balance sheet instead of separating deferred taxes into current and noncurrent amounts. Although the standard is effective for the Company for financial statements issued for annual periods beginning after December 15, 2016 and interim periods within those annual periods, the Company chose early adoption as of the year ended December 31, 2015 and has prospectively classified all deferred tax assets and liabilities as noncurrent on its Consolidated Balance Sheet in accordance with the standard. Balances for 2014 were not required to be retrospectively adjusted. In July 2015, the FASB issued ASU 2015-11, Simplifying the Measurement of Inventory (Topic 330), which simplifies the measurement of inventory by requiring inventory to be measured at the lower of cost and net realizable value. The update is effective for financial statements issued for fiscal years beginning after December 15, 2016 and interim periods within those fiscal years. The Company adopted the new standard on January 1, 2017. The adoption of this ASU had no impact on the Consolidated Balance Sheets or Consolidated Statements of Operations. In April 2015, the FASB issued ASU 2015-03, Interest-Imputation of Interest, Simplifying the Presentation of Debt Issuance Costs , to simplify the presentation of debt issuance costs. This new guidance required that debt issuance costs related to a recognized debt liability be presented in the balance sheet as a direct deduction from the carrying amount of that debt liability, consistent with debt discounts. The standard was effective for financial statements issued for fiscal years beginning after December 15, 2015 and interim periods within those fiscal years, as permitted under the standard. The Company chose to early-adopt this guidance in 2015 and has therefore presented the debt issuance costs associated with the issuance of its Unsecured Senior Notes as a direct deduction from the carrying value of the liability as of December 31, 2015. See Note 7. Debt for additional information related to the Company’s Unsecured Senior Notes. In August 2014, the FASB Issued ASU 2014-15, Presentation of Financial Statements-Going Concern; Disclosure of Uncertainties about an Entity's Ability to Continue as a Going Concern, which requires management to annually evaluate whether there are conditions or events that raise substantial doubts about the Company's ability to continue as a going concern within one year after the date the financial statements are issued. This guidance was effective for the annual period ending after December 15, 2016 and annual and interim periods thereafter, with early adoption permitted. See the discussion of going concern considerations above in this Note. Recently Issued Accounting Pronouncements - Not Yet Adopted In August 2018, the FASB issued ASU 2018-15, Intangibles-Goodwill and Other-Internal Use Software, Customer's Accounting for Implementation Costs Incurred in a Cloud Computing Arrangement That is a Service Contract . This guidance requires the use of existing accounting guidance applicable to software developed for internal use to be applied to cloud computing service contracts' implementation costs. The costs capitalized would be amortized over the life of the agreement, including renewal option periods likely to be used. This guidance is effective for fiscal 2020, with early adoption permitted. The Company does not anticipate that this guidance will have a material impact on its Consolidated Balance Sheet and Consolidated Statement of Operations. In August 2018, the FASB issued ASU 2018-13, Fair Value Measurement-Changes to the Disclosure Requirements for Fair Value Measurement, which both reduces and expands selected disclosure requirements. The principal changes expected to impact the Company's disclosure are requirements to disclose the range and weighted average of each of the significant unobservable items and the way the weighted average of a range is calculated for items in the “table of significant unobservable inputs.” The guidance also requires disclosure of changes in unrealized gains and losses in other comprehensive income and removes requirements regarding, among other items, disclosure of the valuation process for Level 3 measurements. This guidance is effective for all fiscal years and for interim periods within those years, beginning in fiscal 2020. The Company does not anticipate this guidance will have a material impact on its Consolidated Balance Sheet and Consolidated Statement of Operations. In January 2017, the FASB issued ASU 2017-04, Intangibles – Goodwill and Other (Topic 350) – Simplifying the Test for Goodwill Impairment , which eliminated the requirement to calculate the implied fair value of goodwill to measure a goodwill impairment charge. Instead, entities will record an impairment charge based on the excess of a reporting unit’s carrying amount over its fair value. The ASU is effective for annual and interim impairment tests performed in periods beginning after December 15, 2019; early adoption is permitted for annual and interim goodwill impairment testing dates after January 1, 2017. The amendments in this ASU are to be applied on a prospective basis. The Company is continuing to evaluate the impact of this guidance on its financial statements. In June 2016, the FASB issued ASU 2016-13, Financial Instruments-Credit Losses-Measurement of Credit Losses on Financial Instruments , which applies primarily to the Company's accounts receivable impairment loss allowances. The guidance provides a revised model whereby the current expected credit losses are used to compute impairment of financial instruments. The new model requires evaluation of historical experience and various current and expected factors, which may affect the estimated amount of losses and requires determination of whether the affected financial instruments should be grouped in units of account. The Company does not expect any material impact on its Consolidated Statements of Operations when this guidance becomes effective in fiscal 2020. In February 2016, the FASB issued ASU 2016-02, Leases , which created ASC Topic 842, Leases and superseded the existing guidance in ASC 840, Leases. The core principle of ASU 2016-02 is that an entity should recognize on its balance sheets assets and liabilities arising from a lease. In accordance with that principle, ASU 2016-02 required that a lessee recognize a liability to make lease payments (the lease liability) and a right-of-use asset representing its right to use the underlying leased asset for the lease term. The recognition, measurement and presentation of expenses and cash flows arising from a lease by a lessee will depend on the lease's classification as a finance or operating lease. This new accounting guidance is effective for fiscal years beginning after December 15, 2018 under a modified retrospective approach, and early adoption is permitted. In July 2018, the FASB issued ASU 2018-11, which modified the transition guidance in ASU 2016-02 to provide preparers the option to adopt the ASU as of the effective date instead of adjusting prior periods under the modified retrospective approach. The Company is currently evaluating the impact the adoption of this guidance will have on its financial statements. The Company is in the process of assessing its portfolio of leases and compiling a central repository of all active leases. It is also in the process of assessing the design of the future lease process and drafting a policy to address the new standard requirements. Key lease data elements are being evaluated. The Company has selected a software solution to track and account for leases under ASU 2016-02 and is in the process of implementing the solution. While the Company has not yet completed its evaluation of the impact the new lease accounting standard will have on its Consolidated Financial Statements, the Company expects to recognize material right-of-use assets and lease liabilities for its operating leases in the Consolidated Balance Sheet upon the effective date. In May 2014, the FASB issued ASU 2014-09, Revenue from Contracts with Customers (Topic 606) , which supersedes the existing revenue recognition requirements of ASC 605, Revenue Recognition . This ASU provides a single comprehensive model for entities to use in accounting for revenue arising from contracts with customers and will supersede most current revenue recognition guidance. Under the new guidance, an entity will recognize revenue to depict the transfer of promised goods or services to customers at an amount that the entity expects to be entitled to in exchange for those goods or services. A five-step model has been introduced for an entity to apply when recognizing revenue. The new guidance also includes enhanced disclosure requirements. The guidance permits two implementation approaches, one requiring retrospective application of the new standard with restatement of prior years and one requiring prospective application of the new standard with disclosure of results under old standards. In August 2015, the FASB issued ASU 2015-14, which postponed the effective date of ASU 2014-09 to fiscal years and interim periods within those fiscal years, beginning after December 15, 2017, with early adoption permitted on the original effective date of fiscal years beginning after December 15, 2016. The Company adopted the new guidance effective January 1, 2018 using the modified retrospective approach and will expand its consolidated financial statement disclosures in order to comply with the ASU. The Company is continuing to evaluate the impact of this guidance on its financial statements.

Summary of Significant Accoun_3

Summary of Significant Accounting Policies and Other Information (Tables)	12 Months Ended
	Dec. 31, 2017
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Revenue from External Customers by Geographic Areas	The following table summarizes net sales by end market: (in thousands) For the Year Ended December 31, 2015 2014 End Market 2017 2016 (Restated) (Restated) Industrial $ 190,724 $ 164,245 $ 174,203 $ 155,935 Energy 159,008 115,367 137,190 191,528 Transportation 66,884 59,853 50,994 117 Total $ 416,616 $ 339,465 $ 362,387 $ 347,580 The following table summarizes net sales by geographic area: (in thousands) For the Year Ended December 31, 2015 2014 Geographic Area 2017 2016 (Restated) (Restated) North America $ 355,268 $ 304,621 $ 327,479 $ 323,474 Pacific Rim 42,221 22,827 25,356 17,719 Europe 14,205 11,065 9,552 5,705 Other 4,922 952 — 682 Total $ 416,616 $ 339,465 $ 362,387 $ 347,580
Schedules of Concentration of Risk, by Risk Factor	The following table presents customers individually accounting for more than 10% of the Company’s net sales: For the Year Ended December 31, 2015 2014 2017 2016 (Restated) (Restated) Customer A 16 % 17 % 16 % 10 % Customer B 10 % ** ** ** Customer C ** 12 % ** 10 % The following table presents customers individually accounting for more than 10% of the Company’s consolidated accounts receivable: As of December 31, 2015 2014 2017 2016 (Restated) (Restated) Customer A 18 % ** 17 % 15 % Customer B 13 % ** ** ** Customer C ** ** 12 % ** Customer D ** 30 % ** ** Customer E ** ** ** 16 % Customer F ** ** ** 11 % Customer G ** ** 10 % 11 % The following table presents suppliers individually accounting for more than 10% of the Company’s purchases: For the Year Ended December 31, 2015 2014 2017 2016 (Restated) (Restated) Supplier A 21 % 13 % 11 % 15 % Supplier B ** ** 18 % 21 % ** Less than 10% of the total
Schedule of Inventory, Current	Inventories consist of the following: (in thousands) As of December 31, 2015 2014 Inventories 2017 2016 (Restated) (Restated) Raw materials $ 71,732 $ 70,498 $ 102,912 $ 92,360 Work in process 4,535 9,270 12,315 6,021 Finished goods 16,684 30,862 52,136 11,904 Total Inventories 92,951 110,630 167,363 110,285 Inventory allowance (6,227 ) (10,082 ) (5,268 ) (4,035 ) Inventories, net $ 86,724 $ 100,548 $ 162,095 $ 106,250 Activity in the Company’s inventory allowance was as follows: (in thousands) For the Year Ended December 31, 2015 2014 Inventory Allowance 2017 2016 (Restated) (Restated) Balance at beginning of period $ 10,082 $ 5,268 $ 4,035 $ 2,982 Charged to expense 421 5,341 1,712 1,856 Write-offs (4,276 ) (527 ) (479 ) (803 ) Balance at end of year $ 6,227 $ 10,082 $ 5,268 $ 4,035
Schedule of Other Current Assets	Prepaid expenses and other current assets consist of the following: (in thousands) As of December 31, 2015 2014 Prepaid Expenses and Other Current Assets 2017 2016 (Restated) (Restated) Insurance proceeds receivable $ 10,563 $ 8,500 $ — $ — Prepaid expenses 3,710 4,072 2,578 4,840 Other 86 1,072 125 — Total $ 14,359 $ 13,644 $ 2,703 $ 4,840
Property, Plant and Equipment	Estimated useful lives by each type of asset category are as follows: Years Buildings Up to 39 Leasehold improvements Lesser of (i) expected useful life of improvement or (ii) life of lease (including likely extension thereof) Machinery and equipment 1 to 10 Property, plant and equipment by type were as follows: (in thousands) As of December 31, 2015 2014 Property, Plant and Equipment 2017 2016 (Restated) (Restated) Land $ — $ — $ 260 $ 260 Buildings — — 1,471 1,471 Leasehold improvements 6,320 6,199 6,450 3,333 Machinery and equipment 27,379 24,490 23,523 17,500 Construction in progress 2,036 2,084 2,466 3,566 Total property, plant and equipment, at cost 35,735 32,773 34,170 26,130 Accumulated depreciation (16,775 ) (12,646 ) (11,361 ) (8,176 ) Property, plant and equipment, net $ 18,960 $ 20,127 $ 22,809 $ 17,954
Schedule of Other Accrued Liabilities	Other accrued liabilities consisted of the following: (in thousands) As of December 31, 2015 2014 Other Accrued Liabilities 2017 2016 (Restated) (Restated) Warranty $ 12,628 $ 10,200 $ 4,429 $ 2,428 Litigation reserves * 12,137 10,287 3 — Deferred revenue 2,822 1,818 3,564 4,602 Accrued compensation and benefits 2,593 3,975 3,825 5,476 Professional services 1,974 1,509 544 500 Income taxes payable 375 131 107 2,973 Other 5,833 4,587 5,374 2,203 Total $ 38,362 $ 32,507 $ 17,846 $ 18,182 * Litigation reserves primarily consist of accruals for the settlement of the Securities Litigation as of December 31, 2017 and 2016 as well as the tentative settlement of the Federal Derivative Litigation as of December 31, 2017. The Company concluded that insurance recovery was probable and recognized full recovery of the settlement amounts in “Prepaid expenses and other assets”. See Note 10. Commitments and Contingencies for additional information.
Schedule of Product Warranty Liability	Accrued product warranty activities are presented below: (in thousands) For the Year Ended December 31, 2015 2014 Accrued Product Warranty 2017 2016 (Restated) (Restated) Balance at beginning of year $ 10,200 $ 4,429 $ 2,428 $ 1,274 Current year provision 5,405 5,716 2,953 1,348 Acquisitions — — 963 1,600 Changes in estimates for preexisting warranties * — 1,894 — — Payments made during the period (2,977 ) (1,839 ) (1,915 ) (1,794 ) Balance at end of year $ 12,628 $ 10,200 $ 4,429 $ 2,428 * Change in estimates for pre-existing warranties reflect changes in the Company’s estimate of warranty costs for products sold in prior periods. Such adjustments typically occur when claims experience deviates from historic and expected trends. The Company’s warranty liability is generally affected by failure rates, repair costs and the timing of failures. Future events and circumstances related to these factors could materially change the estimates and require adjustments to the warranty liability. In addition, new product launches require a greater use of judgment in developing estimates until historical experience becomes available. In 2016, the Company recorded charges for adjustments for changes in estimates of $1.9 million ( $1.2 million , net of tax), or $0.11 per diluted share.

Restatement of Previously Iss_2

Restatement of Previously Issued Consolidated Financial Statements (Tables)	12 Months Ended
	Dec. 31, 2017
Accounting Changes and Error Corrections [Abstract]
Schedule of Error Corrections and Prior Period Adjustments	The following table sets forth the effects of the restatement adjustments on revenue and pretax income (loss) in the Consolidated Statements of Operations for the years ended December 31, 2015 and 2014. Due to the substantial number of restatement adjustments, each of the restatement categories listed in the table below may represent multiple related adjustments that have been aggregated for disclosure purposes. (in thousands) For the Year Ended December 31, 2015 2014 Net Sales Income (Loss) Before Income Taxes Net Sales Income (Loss) Before Income Taxes Previously reported $ 389,446 $ 13,890 $ 347,995 $ 34,539 Restatement adjustments: Revenue recognition adjustments (27,059 ) (9,215 ) (415 ) (2,700 ) Product development cost — (1,001 ) — (2,397 ) Inventory valuation — (1,069 ) — 38 Impairment of long-lived assets — (11,733 ) — (310 ) Product warranty — (2,484 ) — 591 Accrued liabilities — (1,106 ) — 591 Purchase accounting — — — (845 ) Equity investment — 125 — (286 ) Net restatement adjustments (27,059 ) (26,483 ) (415 ) (5,318 ) Restated $ 362,387 $ (12,593 ) $ 347,580 $ 29,221 The following table presents the effect of the restatement adjustments and reclassifications on the Consolidated Statement of Operations for 2015: (in thousands, except for per share data) Year Ended December 31, 2015 Previously Reported Restatement Adjustments and Reclassifications Restated Net sales $ 389,446 $ (27,059 ) $ 362,387 Cost of sales 326,612 (15,464 ) 311,148 Gross profit 62,834 (11,595 ) 51,239 Operating expenses: Research, development and engineering expenses 21,681 1,893 23,574 Selling, general and administrative expenses 27,376 1,461 28,837 Asset impairment charge — 11,686 11,686 Amortization of intangible assets 4,582 — 4,582 Change in fair value of contingent consideration — (23 ) — (23 ) Total operating expenses 53,639 15,017 68,656 Operating income (loss) 9,195 (26,612 ) (17,417 ) Other (income) expense: Interest expense 4,327 (7 ) 4,320 Contingent consideration 48 (48 ) — Gain from change in fair value of warrants (9,299 ) (1 ) (9,300 ) Loss on debt extinguishment and modifications — 12 12 Other expense, net 229 (85 ) 144 Total other income (4,695 ) (129 ) (4,824 ) Income (loss) before income taxes 13,890 (26,483 ) (12,593 ) Income tax benefit (388 ) (9,314 ) (9,702 ) Net income (loss) $ 14,278 $ (17,169 ) $ (2,891 ) Weighted-average common shares outstanding: Basic 10,808 — 10,808 Diluted 11,074 (83 ) 10,991 Earnings (loss) per common share: Basic $ 1.32 $ (1.59 ) $ (0.27 ) Diluted $ 0.45 $ (1.56 ) $ (1.11 ) The following table presents the effect of the restatement adjustments and reclassifications on the Consolidated Statement of Operations for 2014: (in thousands, except for per share data) Year Ended December 31, 2014 Previously Reported Restatement Adjustments and Reclassifications Restated Net sales $ 347,995 $ (415 ) $ 347,580 Cost of sales 280,950 2,590 283,540 Gross profit 67,045 (3,005 ) 64,040 Operating expenses: Research, development and engineering expenses 16,900 2,405 19,305 Selling, general and administrative expenses 23,088 54 23,142 Asset impairment charge — 310 310 Amortization of intangible assets 1,013 — 1,013 Change in fair value of contingent consideration — (3,840 ) (3,840 ) Total operating expenses 41,001 (1,071 ) 39,930 Operating income 26,044 (1,934 ) 24,110 Other expense (income): Interest expense 1,331 11 1,342 Contingent consideration (3,840 ) 3,840 — Gain from change in fair value of warrants (6,169 ) (1 ) (6,170 ) Other expense (income), net 183 (466 ) (283 ) Total other income (8,495 ) 3,384 (5,111 ) Income before income taxes 34,539 (5,318 ) 29,221 Income tax expense 10,813 (3,069 ) 7,744 Net income $ 23,726 $ (2,249 ) $ 21,477 Weighted-average common shares outstanding: Basic 10,707 (2 ) 10,705 Diluted 11,132 (1 ) 11,131 Earnings (loss) per common share: Basic $ 2.22 $ (0.21 ) $ 2.01 Diluted $ 2.13 $ (0.75 ) $ 1.38 The following table sets forth the effects of the restatement adjustments and reclassifications adjustments on the Company's Consolidated Balance Sheet as of December 31, 2015: (in thousands) As of December 31, 2015 Previously Reported Restatement Adjustments and Reclassifications Restated ASSETS Current assets Cash and cash equivalents $ 8,445 $ — $ 8,445 Accounts receivable, net 104,365 (33,833 ) 70,532 Income tax receivable 5,230 35 5,265 Inventories, net 130,347 31,748 162,095 Prepaid expenses and other current assets 4,288 (1,585 ) 2,703 Total current assets 252,675 (3,635 ) 249,040 Property, plant and equipment, net 26,001 (3,192 ) 22,809 Intangible assets, net 31,745 — 31,745 Goodwill 41,466 (11,631 ) 29,835 Deferred income taxes 819 16,838 17,657 Other noncurrent assets 7,230 (4,479 ) 2,751 TOTAL ASSETS $ 359,936 $ (6,099 ) $ 353,837 LIABILITIES AND STOCKHOLDERS’ EQUITY Current liabilities Accounts payable $ 76,078 $ 3,745 $ 79,823 Contingent consideration 8,788 (513 ) 8,275 Other accrued liabilities 14,396 3,450 17,846 Total current liabilities 99,262 6,682 105,944 Revolving line of credit 97,299 — 97,299 Warrants 1,482 — 1,482 Long-term debt, less current maturities, net 53,820 (15 ) 53,805 Other noncurrent liabilities 1,776 8,658 10,434 TOTAL LIABILITIES $ 253,639 $ 15,325 $ 268,964 STOCKHOLDERS’ EQUITY Preferred stock $ — $ — $ — Common stock 12 (1 ) 11 Additional paid-in capital 75,179 8,198 83,377 Retained earnings 35,356 (22,419 ) 12,937 Treasury stock, at cost (4,250 ) (7,202 ) (11,452 ) TOTAL STOCKHOLDERS’ EQUITY 106,297 (21,424 ) 84,873 TOTAL LIABILITIES AND STOCKHOLDERS’ EQUITY $ 359,936 $ (6,099 ) $ 353,837 The following table sets forth the effects of the restatement adjustments and reclassifications on the Company's Consolidated Balance Sheet as of December 31, 2014: (in thousands) As of December 31, 2014 Previously Reported Restatement Adjustments and Reclassifications Restated ASSETS Current assets Cash and cash equivalents $ 6,561 $ — $ 6,561 Accounts receivable, net 81,740 (5,474 ) 76,266 Inventories, net 93,903 12,347 106,250 Prepaid expenses and other current assets 4,801 39 4,840 Deferred income taxes 3,998 4,554 8,552 Total current assets 191,003 11,466 202,469 Property, plant and equipment, net 20,892 (2,938 ) 17,954 Intangible assets, net 21,392 (200 ) 21,192 Goodwill 23,546 (132 ) 23,414 Deferred income tax asset — 13 13 Other noncurrent assets 5,804 (3,901 ) 1,903 TOTAL ASSETS $ 262,637 $ 4,308 $ 266,945 LIABILITIES AND STOCKHOLDERS’ EQUITY Current liabilities Accounts payable $ 60,877 $ 6,836 $ 67,713 Current maturities of long-term debt 1,667 — 1,667 Other accrued liabilities 13,504 4,678 18,182 Total current liabilities 76,048 11,514 87,562 Revolving line of credit 78,030 — 78,030 Deferred income taxes 3,241 (3,241 ) — Warrants 11,036 — 11,036 Long-term debt, less current maturities, net 2,361 — 2,361 Other noncurrent liabilities 1,122 351 1,473 TOTAL LIABILITIES $ 171,838 $ 8,624 $ 180,462 STOCKHOLDERS’ EQUITY Preferred stock $ — $ — $ — Common stock 12 (1 ) 11 Additional paid-in capital 73,959 7,787 81,746 Retained earnings 21,078 (5,250 ) 15,828 Treasury stock, at cost (4,250 ) (6,852 ) (11,102 ) TOTAL STOCKHOLDERS’ EQUITY 90,799 (4,316 ) 86,483 TOTAL LIABILITIES AND STOCKHOLDERS’ EQUITY $ 262,637 $ 4,308 $ 266,945 The following table sets forth the effect of the restatement adjustments on the components of total stockholders, equity as of December 31, 2013: (in thousands) As of December 31, 2013 Previously Reported Restatement Adjustments Restated Preferred stock $ — $ — $ — Common Stock 11 — 11 Additional paid-in capital 57,308 4,622 61,930 Accumulated deficit (2,649 ) (3,079 ) (5,728 ) Treasury stock, at cost (4,250 ) (4,435 ) (8,685 ) Total stockholders' equity $ 50,421 $ (2,891 ) $ 47,530 The following table summarizes the effects of the restatement on the Company's Consolidated Statements of Changes in Stockholders’ Equity as of December 31, 2015 and 2014: (in thousands) Year Ended December 31, 2015 2014 Stockholders' equity, as previously reported $ 106,297 $ 90,799 Effect of restatement adjustments on net income/retained earnings (21,424 ) (4,316 ) Stockholders' equity, restated $ 84,873 $ 86,483 The following table includes comparison of selected previously reported and restated information from the Company's Consolidated Statements of Cash Flows for 2015 and 2014: (in thousands) For the Year Ended December 31, 2015 2014 Previously Reported Restated Previously Reported Restated Net cash used in operating activities $ (23,049 ) $ (22,815 ) $ (15,685 ) $ (15,094 ) Net cash used in investing activities (43,570 ) (43,805 ) (51,713 ) (52,322 ) Net cash provided by financing activities 68,503 68,504 67,653 67,671 Increase in cash 1,884 1,884 255 255 Cash at beginning of year 6,561 6,561 6,306 6,306 Cash at end of year $ 8,445 $ 8,445 $ 6,561 $ 6,561 The following table sets forth the effect of the restatement adjustments on the components of total stockholders' equity as of December 31, 2013: (in thousands) As of December 31, 2013 Stockholders' Equity Previously Reported Restatement Adjustments Restated Common stock $ 11 $ — $ 11 Additional paid-in capital 57,308 4,622 61,930 Accumulated deficit (2,648 ) (3,079 ) (5,649 ) Treasury stock, at cost (4,250 ) (4,435 ) (8,685 ) Total $ 50,421 $ (2,891 ) $ 47,607 The Company identified the following categories that required restatement or reclassification and were comprised of a number of related adjustments that have been aggregated for disclosure purposes: (in thousands) Three Months Ended March 31, 2016 Net Sales (Loss) Income Before Income Taxes Previously Reported $ 61,814 $ (8,931 ) Restatement adjustments: Revenue recognition adjustments $ 14,656 $ 3,111 Product development cost — 123 Inventory valuation — (404 ) Impairment of long-lived assets — (557 ) Product warranty — (319 ) Accrued liabilities — 422 Equity investment — (125 ) Net restatement adjustments 14,656 2,251 Restated $ 76,470 $ (6,680 ) The following table presents the effect of the restatement adjustments and reclassifications on the Consolidated Statement of Operations for three months ended March 31, 2016: (in thousands, except for per share data) Three Months Ended March 31, 2016 Previously Reported Restatement Adjustments and Reclassifications Restated Net sales $ 61,814 $ 14,656 $ 76,470 Cost of sales 57,758 12,069 69,827 Gross profit 4,056 2,587 6,643 Operating expenses: Research, development and engineering expenses 5,250 (346 ) 4,904 Selling, general and administrative expenses 6,058 347 6,405 Asset impairment charge — 345 345 Amortization of intangible assets 1,429 (1 ) 1,428 Total operating expenses 12,737 345 13,082 Operating loss (8,681 ) 2,242 (6,439 ) Other expense (income): Interest expense 1,421 17 1,438 Private placement warrants income (1,256 ) — (1,256 ) Other expense, net 85 (26 ) 59 Total other expense 250 (9 ) 241 Loss before income taxes (8,931 ) 2,251 (6,680 ) Income tax benefit (3,680 ) 323 (3,357 ) Net loss $ (5,251 ) $ 1,928 $ (3,323 ) Weighted-average common shares outstanding: Basic 10,819 — 10,819 Diluted 10,819 — 10,819 (Loss) earnings per common share: Basic $ (0.49 ) $ 0.07 $ (0.42 ) Diluted $ (0.49 ) $ 0.07 $ (0.42 ) as of March 31, 2016: (in thousands) As of March 31, 2016 Previously Reported Restatement Adjustments and Reclassifications Restated ASSETS Current assets Cash and cash equivalents $ 1,495 $ — $ 1,495 Accounts receivable, net 63,163 (17,779 ) 45,384 Income tax receivable — 1,723 1,723 Inventories, net 120,735 18,784 139,519 Prepaid expenses and other current assets 9,496 (5,364 ) 4,132 Total current assets 194,889 (2,636 ) 192,253 Property, plant and equipment, net 24,289 (3,627 ) 20,662 Intangible assets, net 30,316 — 30,316 Goodwill 41,466 (11,631 ) 29,835 Deferred income taxes 819 18,466 19,285 Other noncurrent assets 7,181 (4,517 ) 2,664 TOTAL ASSETS $ 298,960 $ (3,945 ) $ 295,015 LIABILITIES AND STOCKHOLDERS’ EQUITY Current liabilities Accounts payable $ 41,491 $ 1,669 $ 43,160 Contingent consideration — 5,481 5,481 Other accrued liabilities 19,692 (1,763 ) 17,929 Total current liabilities 61,183 5,387 66,570 Revolving line of credit 80,568 — 80,568 Warrants 226 — 226 Long-term debt, less current maturities, net 53,946 (147 ) 53,799 Other noncurrent liabilities 1,670 10,282 11,952 TOTAL LIABILITIES $ 197,593 $ 15,522 $ 213,115 STOCKHOLDERS’ EQUITY Preferred stock $ — $ — $ — Common stock 12 (1 ) 11 Additional paid-in capital 75,500 8,229 83,729 Retained earnings 30,105 (20,493 ) 9,612 Treasury stock, at cost (4,250 ) (7,202 ) (11,452 ) TOTAL STOCKHOLDERS’ EQUITY 101,367 (19,467 ) 81,900 TOTAL LIABILITIES AND STOCKHOLDERS’ EQUITY $ 298,960 $ (3,945 ) $ 295,015 The restatement effect on the previously issued condensed Consolidated Statement of Cash Flow for the three months ended March 31, 2016 is as follows: (in thousands) Three Months Ended March 31, 2016 Previously Reported Restatement and Reclassification Reclassified Net cash provided by operating activities $ 9,995 $ 3,915 $ 13,910 Net cash used in investing activities (214 ) (885 ) (1,099 ) Net cash used in financing activities (16,731 ) (3,030 ) (19,761 ) Decrease in cash (6,950 ) — (6,950 ) Cash at beginning of year 8,445 — 8,445 Cash at end of period $ 1,495 $ — $ 1,495

Property, Plant and Equipment_2

Property, Plant and Equipment and Leases (Tables)	12 Months Ended
	Dec. 31, 2017
Property, Plant and Equipment [Abstract]
Property, Plant and Equipment	Estimated useful lives by each type of asset category are as follows: Years Buildings Up to 39 Leasehold improvements Lesser of (i) expected useful life of improvement or (ii) life of lease (including likely extension thereof) Machinery and equipment 1 to 10 Property, plant and equipment by type were as follows: (in thousands) As of December 31, 2015 2014 Property, Plant and Equipment 2017 2016 (Restated) (Restated) Land $ — $ — $ 260 $ 260 Buildings — — 1,471 1,471 Leasehold improvements 6,320 6,199 6,450 3,333 Machinery and equipment 27,379 24,490 23,523 17,500 Construction in progress 2,036 2,084 2,466 3,566 Total property, plant and equipment, at cost 35,735 32,773 34,170 26,130 Accumulated depreciation (16,775 ) (12,646 ) (11,361 ) (8,176 ) Property, plant and equipment, net $ 18,960 $ 20,127 $ 22,809 $ 17,954
Schedule of Future Minimum Lease Payments	The future minimum lease payments due under operating and capital leases in effect, as amended and extended, as of December 31, 2017, were as follows: (in thousands) Operating Capital 2018 $ 4,341 $ 22 2019 4,136 21 2020 3,786 20 2021 3,482 20 2022 3,578 19 2023 and beyond 3,202 51 Total $ 22,525 $ 153

Acquisitions (Tables)

Acquisitions (Tables)	12 Months Ended
	Dec. 31, 2017
Business Combinations [Abstract]
Schedule of Recognized Identified Assets Acquired and Liabilities Assumed	The following table summarizes the purchase price allocation of the fair value of assets acquired and liabilities assumed in the Bi-Phase acquisition: (in thousands) Purchase Price Allocation Purchase consideration: Initial cash paid at date of acquisition $ 3,619 Fair value of contingent consideration 540 Working capital adjustment 266 Purchase price, net of cash acquired $ 4,425 Allocation of consideration to assets acquired and liabilities assumed: Accounts receivable $ 212 Inventories 2,103 Prepaid expenses and other current assets 166 Property, plant and equipment 113 Intangible assets 860 Goodwill 1,217 Current liabilities (246 ) Net assets acquired $ 4,425 The following table summarizes the purchase price allocation of the fair value of assets acquired and liabilities assumed in the Buck's acquisition: (in thousands) Purchase Price Allocation Purchase Consideration: Cash Consideration at date of acquisition $ 9,735 Allocation of consideration to assets acquired: Inventories $ 6,598 Property, plant and equipment 231 Intangible assets 1,380 Goodwill 1,526 Net assets acquired $ 9,735 The following table summarizes the purchase price allocation of the fair value of assets acquired and liabilities assumed in the Powertrain acquisition: (in thousands) Purchase Price Allocation Purchase consideration: Initial cash paid at date of acquisition $ 20,873 Fair value of contingent consideration 8,200 Working capital adjustment (97 ) Total purchase consideration $ 28,976 Allocation of consideration to assets acquired and liabilities assumed: Accounts receivable $ 4,931 Inventories 1,890 Prepaid expenses and other current assets 23 Property, plant and equipment 314 Intangible assets 13,600 Goodwill 15,311 Other non-current assets 24 Current liabilities (7,117 ) Net assets acquired $ 28,976 (in thousands) Purchase Price Allocation (Restated) Purchase consideration: Initial cash paid at date of acquisition, net of acquired cash $ 44,122 Fair value of contingent consideration 3,840 Fair value of the fixed number of shares of Common Stock 5,060 Purchase considerations: $ 53,022 Allocation of consideration to assets acquired and liabilities assumed: Accounts receivable $ 3,989 Inventories 4,953 Prepaid expenses and other current assets 243 Property, plant and equipment 2,346 Intangible assets 23,300 Goodwill 23,414 Current liabilities (5,223 ) Net assets acquired $ 53,022
Summary of Identifiable Intangible Assets	The intangible assets are amortized over their respective estimated useful lives as follows: (in thousands) Asset Amount Estimated Life Backlog $ 600 3 months Customer relationships 13,000 12 years Total intangible assets $ 13,600 The intangible asset is amortized over its estimated useful life as follows: (in thousands) Asset Amount Estimated Life Customer relationships $ 1,380 10 years The intangible assets are amortized over their respective estimated useful lives, which approximate the period over which the Company expects to gain the estimated economic benefits as follows: (in thousands) Asset Amount Estimated Life Backlog $ 1,200 15 months Customer relationships 20,400 13 years Trade names and trademarks 1,700 13 years Total intangible assets $ 23,300 The intangible assets are amortized over their respective estimated useful lives as follows: (in thousands) Asset Amount Estimated Life Developed technology $ 700 7 years Customer relationships 160 15 years Total intangible assets $ 860
Business Acquisition, Pro Forma Information	The following supplemental unaudited pro-forma information presents the combined results of operations of the Company and 3PI as though the acquisition of 3PI occurred on January 1, 2014. The Company also presents the combined results of operations of the Company and Powertrain as though the acquisition of Powertrain occurred on January 1, 2015. The Company did not include pro-forma results of operations for Bi-Phase and Buck’s, as the results are immaterial to the Company's Consolidated Statements of Operations. The pro-forma information is not necessarily indicative of the actual consolidated results had the 3PI acquisition occurred as of January 1, 2014, or had the Powertrain acquisition occurred as of January 1, 2015, or of future consolidated operating results. (in thousands, except per share amounts) For the Year Ended December 31, 2015 2014 Net sales $ 383,455 $ 352,760 Net income (580 ) 21,696 Earnings per common share, basic $ (0.05 ) $ 2.03 Earnings per common share, diluted $ (0.05 ) $ 1.95

Goodwill and Other Intangibles

Goodwill and Other Intangibles (Tables)	12 Months Ended
	Dec. 31, 2017
Goodwill and Intangible Assets Disclosure [Abstract]
Schedule of Goodwill	The carrying amounts for goodwill and changes in the carrying value were as follows: (in thousands) For the Year Ended December 31, 2015 2014 2017 2016 (Restated) (Restated) Balance at beginning of year, net $ 29,835 $ 29,835 $ 23,414 $ — Acquisitions — — 18,054 23,414 Impairment losses — — (11,633 ) — Balance at end of year, net $ 29,835 $ 29,835 $ 29,835 $ 23,414 Accumulated impairment losses $ (11,633 ) $ (11,633 ) $ — $ —
Schedule of Finite-Lived Intangible Assets	Components of intangible assets are as follows: (in thousands, except weighted-average useful life) As of December 31, 2017 Weighted-Average Useful Life (in years) Gross Carrying Value Accumulated Amortization Net Book Value Customer relationships 10.0 $ 34,940 $ (14,915 ) $ 20,025 Developed technology 4.2 1,000 (434 ) 566 Trade names and trademarks 6.1 1,700 (800 ) 900 Total $ 37,640 $ (16,149 ) $ 21,491 (in thousands, except weighted-average useful life) As of December 31, 2016 Weighted-Average Useful Life (in years) Gross Carrying Value Accumulated Amortization Net Book Value Customer relationships 10.8 $ 34,940 $ (10,430 ) $ 24,510 Developed technology 8.3 700 (287 ) 413 Trade names and trademarks 6.8 1,700 (594 ) 1,106 Total $ 37,340 $ (11,311 ) $ 26,029 (in thousands, except weighted-average useful life) As of December 31, 2015 Weighted-Average Useful Life (in years) Gross Carrying Value Accumulated Amortization Net Book Value (Restated) (Restated) (Restated) Backlog $ 1,800 $ (1,800 ) $ — Customer relationships 11.5 34,940 (5,129 ) 29,811 Developed technology 8.2 700 (113 ) 587 Trade names and trademarks 7.5 1,700 (353 ) 1,347 Total $ 39,140 $ (7,395 ) $ 31,745 (in thousands, except weighted-average useful life) As of December 31, 2014 Weighted-Average Useful Life (in years) Gross Carrying Value Accumulated Amortization Net Book Value (Restated) (Restated) (Restated) Backlog 1.0 $ 1,200 $ (1,095 ) $ 105 Customer relationships 21.0 20,400 (926 ) 19,474 Trade names and trademarks 8.3 1,700 (87 ) 1,613 Total $ 23,300 $ (2,108 ) $ 21,192
Summary of Amortization Expense	Amortization expense was classified as follows in the Consolidated Statements of Operations: (in thousands) For the Year Ended December 31, 2015 2014 2017 2016 (Restated) (Restated) Cost of sales $ — $ — $ 705 $ 1,095 Operating expenses 4,838 5,716 4,582 1,013 Total $ 4,838 $ 5,716 $ 5,287 $ 2,108
Schedule of Future Amortization Expense	Estimated future amortization expense for intangible assets as of December 31, 2017 is as follows: (in thousands) Year Ending December 31, Estimated Amortization 2018 $ 4,227 2019 3,698 2020 3,113 2021 2,594 2022 2,184 2023 and beyond 5,675 Total $ 21,491

Debt (Tables)

Debt (Tables)	12 Months Ended
	Dec. 31, 2017
Debt Disclosure [Abstract]
Schedule of Debt	The TPG Term Loan was amended as follows: Amendment Date and Title Reason for Amendment Significant Changes to the TPG Term Loan August 22, 2016. TPG First Amendment To facilitate waiver of events of default triggered by the Company's delay in filing Form 10-Q for the period ended June 30, 2016 and failure to disclose a litigation • Provided certain waivers under the credit agreements related to the delayed Form 10-Q filing for the period ended June 30, 2016 and a failure to disclose litigation; December 19, 2016. TPG Second Amendment To facilitate waiver of event of default triggered by the Company's failure to meet minimum EBITDA required for the month ended October 31, 2016 • Made permanent the $12.5 million reserve against the Wells Fargo borrowing base availability as discussed in the Wells Fargo Credit Agreement section above; February 6, 2017. Limited Waiver Agreement To facilitate waiver of various Events of Default triggered by resignation of the Company's auditor and removal of audit opinion on the Company's 2015 and 2014 consolidated financial statements • Waived various events of default related to resignation of the Company's external auditors; • Provided the lenders with the right to charge additional interest of 2% per annum even though events of default had been waived; and • Agreed that the outstanding principal amount of the TPG Term Loan was $71.4 million, comprised of the original amount of $60.0 million, the $3.0 million fee from the August 22, 2016 Amendment and the $8.4 million fee from the December 19, 2016 Amendment. The Company's outstanding debt consisted of the following: (in thousands) As of December 31, 2015 2014 Description of Debt 2017 2016 (Restated) (Restated) Short-Term Debt: Current portion of Wells Fargo Term Loan $ — $ — $ — $ 1,667 Current portion of TPG Term Loan — 750 — — Wells Fargo Revolving Credit Facility 37,055 12,774 — — Total Short-Term Debt $ 37,055 $ 13,524 $ — $ 1,667 Long-Term Debt: Senior Secured Credit Facility - Wells Fargo Revolving Credit Facility $ — $ — $ 97,299 $ 78,030 Wells Fargo Term Loan — — — 2,361 Unsecured Senior Notes 55,000 55,000 55,000 — TPG Term Loan — 70,650 — — Less Unamortized Debt Issuance Costs * (561 ) (15,258 ) (1,195 ) — Total Long-Term Debt $ 54,439 $ 110,392 $ 151,104 $ 80,391 * Unamortized financing costs and deferred fees on the Wells Fargo revolving credit facility are not presented in the above table as they are classified as “ Current Assets ” on the Consolidated Balance Sheets. Debt issuance costs incurred, including gross waiver fees (primarily paid to the lenders), were $0.9 million , $17.2 million , $1.5 million and $0.2 million in 2017, 2016, 2015 and 2014, respectively. • Provides for customary events of default (subject in c
Schedule of Maturities of Long-term Debt	The schedule of remaining principal maturities of Long-Term Debt is as follows: (in thousands) Year Ending December 31, Maturities of Long-Term Debt 2018 $ — 2019 — 2020 55,000 Total $ 55,000
Schedule of Line of Credit Facilities	Information regarding amounts borrowed under the Wells Fargo Credit Agreement includes the following: (in thousands, except interest rate) As of December 31, 2015 2014 Description 2017 2016 (Restated) (Restated) Average borrowings under Wells Fargo Revolving Credit Facility $ 26,662 $ 44,335 $ 96,390 $ 53,250 Average Interest Cost on Wells Fargo Revolving Credit Facility 6.85 % 2.75 % 1.96 % 2.36 % Accrued and unpaid interest $ 90 $ 24 $ 86 $ 105 LIBOR loan interest rate 4.51 % 2.71 % 1.84 % 1.66 % Wells Fargo Prime Rate (Base Rate) loan interest rate 6.00 % 4.25 % 3.50 % 3.25 % The most significant changes are summarized in the table below: Amendment Date and Title Reason for Amendment Significant Changes to the Wells Fargo Credit Agreement April 1, 2014. Amended Wells Fargo Credit Agreement To finance acquisition of 3PI • Increased maximum borrowing under the under the revolving credit facility to $90.0 million; September 30, 2014 and February 11, 2015. Wells Fargo Credit Agreement II To increase capacity of Wells Fargo Credit Agreement • Increased maximum borrowing under the under the revolving credit facility to $100.0 million on September 30, 2014. April 29, 2015. Amended Wells Fargo Credit Agreement III To facilitate Issuance of the Unsecured Senior Notes • Accelerated maturity date to no earlier than December 31, 2016 and no later than January 31, 2018, to ensure that it matures prior to repayment of the Unsecured Senior Notes; June 28, 2016. Second Amended and Restated Credit Agreement (the “June 28, 2016 Agreement”) To facilitate issuance of TPG Term Loan • Decreased maximum borrowing under the revolving credit facility to $75.0 million from $125.0 million in response to issuance of TPG Term Loan; August 22, 2016. First Amendment and Waivers to the June 28, 2016 Agreement To consider implications of various events of default • Provided for certain waivers related to the failure to disclose litigation and the Company’s delay in filing its Form 10-Q for the period ended June 30, 2016; • Reduced borrowing base by $12.5 million to be reduced to $7.5 million upon filing the Form 10-Q for the period ended June 30, 2016. December 16, 2016. Waiver to June 28, 2016 Agreement To consider implications of various events of default • Provided for certain waivers for events of default due to the Company's failure to timely deliver the monthly financial statements and required certificates for the month ended October 31, 2016, provided that such documents were delivered by December 19, 2016. December 19, 2016. Second Amendment and Waivers to the June 28, 2016 Agreement To consider implications of various events of default • Made the $12.5 million borrowing base reserve permanent; • Provided for certain waivers related to the Company’s non-compliance with the TPG Agreement’s minimum trailing twelve months EBITDA maintenance covenant; • The Company paid an amendment fee of $0.1 million. February 10, 2017, effective as of February 6, 2017. Limited Waiver Agreement to the June 28, 2016 Agreement (“Limited Waiver”) To consider implications of various events of default • Provided waiver for various events of default including identified material weaknesses in internal control through February 28, 2017; • Wells Fargo reserved the right to increase the interest rate by 200 basis points (2%) effective January 27, 2017, though the interest rate was not increased; • Provided Wells Fargo with access to additional financial information including cash flow forecasts and budgets. February 28, 2017, effective as of February 6, 2017. First Amendment to Limited Waiver To refine provisions of Limited Waiver to June 28, 2016 Agreement • Established minimum financial metrics related to liquidity and cash which were required to be maintained through March 3, 2017; • Extended the Limited Waiver to March 3, 2017. March 9, 2017, effective as of February 6, 2017. Second Amendment to Limited Waiver To refine provisions of Limited Waiver to June 28, 2016 Agreement • Extended the Limited Waiver to March 10, 2017. March 31, 2017, effective as of February 7, 2017. Third Amendment to Limited Waiver To facilitate changes necessary due to Weichai SPA • Modified certain changes in control and other definitions to permit issuance of securities to Weichai and pay off TPG Term Loan; July 17, 2017. Fourth Amendment to the June 28, 2016 Agreement To facilitate changes to availability, commitment fee and interest rate terms • Increases available borrowing under the revolving credit facility to $52.5 million (maximum borrowing amount of $65.0 million less a reserve of $12.5 million); • Reduced the incremental interest rate by 100 basis points (1%) from 200 basis points (2%) until the Company’s 2016 audited financial statements have been provided. October 3, 2017. Consent and Fifth Amendment to the June 28, 2016 Agreement To facilitate an acquisition • Increased available borrowing under the revolving credit facility to $58.75 million (maximum borrowing amount of $65.0 million less a reserve of $6.25 million). March 29, 2018. Sixth Amendment and Waiver to the June 28, 2016 Agreement To consider implications of various events of default • Increased the maximum borrowing under the revolving credit facility to $75.0 million from $65.0 million; • Modified the reserve against the maximum borrowing under the revolving credit facility to the greater of $6.5 million and 10% of borrowing base, but no more than $7.5 million on or prior to September 30, 2018 and thereafter equal to $9.0 million; • Extended the maturity date of the facility to the earlier of March 31, 2021 or 60 days prior to the final maturity of the Unsecured Senior Notes, which were extended to January 1, 2020, resulting in a maturity date of November 2, 2019 on the Wells Fargo revolving credit facility. • The revolving credit facility will continue to bear interest at a per annum rate equal to 100 basis points (1%) above the per annum rate otherwise applicable under the credit agreement until the Company has completed all filings required to be made with the SEC; • The Company paid an amendment fee of $0.8 million.

Fair Value of Financial Instr_2

Fair Value of Financial Instruments (Tables)	12 Months Ended
	Dec. 31, 2017
Fair Value Disclosures [Abstract]
Schedule of Fair Value Measurements at Reporting Date	The Base and Additional Earn-outs were paid in cash during 2016, as discussed below in Contingent Consideration section. (in thousands) As of December 31, 2017 Carrying Value Fair Value Level 1 Level 2 Level 3 Weichai warrant liability $ 24,700 $ — $ — $ 24,700 Contingent consideration 12 — — 12 (in thousands) As of December 31, 2016 Carrying Value Fair Value Level 1 Level 2 Level 3 Contingent consideration $ 38 $ — $ — $ 38 (in thousands) As of December 31, 2015 Carrying Value Fair Value (Restated) (Restated) Level 1 Level 2 Level 3 Private placement warranty liability $ 1,482 $ — $ — $ 1,482 Contingent consideration 8,717 — — 8,717 (in thousands) As of December 31, 2014 Carrying Value Fair Value (Restated) (Restated) Level 1 Level 2 Level 3 Private placement warranty liability $ 11,036 $ — $ — $ 11,036 (in thousands) As of December 31, 2017 Carrying Value Fair Value Level 1 Level 2 Level 3 Wells Fargo revolving credit facility $ 37,055 $ — $ 37,055 $ — Unsecured Senior Notes 55,000 — — 50,000 (in thousands) As of December 31, 2016 Carrying Value Fair Value Level 1 Level 2 Level 3 Wells Fargo revolving credit facility $ 12,774 $ — $ 12,774 $ — Unsecured Senior Notes 55,000 — — 49,800 TPG Term Loan 71,400 — — 70,800 (in thousands) As of December 31, 2015 Carrying Value Fair Value (Restated) (Restated) Level 1 Level 2 Level 3 Wells Fargo revolving credit facility $ 97,299 $ — $ 97,299 $ — Unsecured Senior Notes 55,000 — — 55,000 (in thousands) As of December 31, 2014 Carrying Value Fair Value (Restated) (Restated) Level 1 Level 2 Level 3 Wells Fargo revolving credit facility $ 78,030 $ — $ 78,030 $ — Wells Fargo Term Loan 4,028 — 4,028 —
Summary of Change in the Estimated Fair Value of Private Placement Warrants	The following table summarizes the change in the estimated fair value of the Company’s contingent consideration, primarily for Powertrain in 2016 and 2015 and for 3PI in 2014. (in thousands) For the Year Ended December 31, 2017 2016 2015 (Restated) 2014 (Restated) Balance at beginning of year $ 38 $ 8,717 $ — $ — Initial estimate of contingent consideration liability — — 8,740 3,840 Increase (decrease) in value reflected in income 1 — (230 ) (23 ) (3,840 ) Payment of contingent consideration 2 (26 ) (8,449 ) — — — Balance at end of year $ 12 $ 38 $ 8,717 $ — Less: Noncurrent portion — 12 442 — Short-term contingent consideration at end of year $ 12 $ 26 $ 8,275 $ — 1. Includes $0.1 million of interest on contingent consideration recorded in Interest expense on the Consolidated Statement of Operations. 2. Includes $0.1 million of cash paid in excess of the initial fair value estimate of contingent consideration at the time of the Powertrain acquisition and presented in “ Other, net ” within cash flows from operating activities in the Consolidated Statement of Cash Flows. The following table summarizes changes in the estimated fair value of the Company’s warrant liability: (in thousands) As of December 31, 2017 2016 2015 2014 (Restated) (Restated) Balance at beginning of year $ — $ 1,482 $ 11,036 $ 24,525 Exercise of private placement warrants — (69 ) (255 ) (7,320 ) Issuance of warrants 20,700 — — — Increase (decrease) in value * 4,000 (1,413 ) (9,299 ) (6,169 ) Balance at end of year $ 24,700 $ — $ 1,482 $ 11,036 * Loss (gain) related to the change in fair value of the warrants for each year are presented as “ Loss (gain) from change in fair value of warrants ” in the Company's Consolidated Statements of Operations.
Schedule of Inputs of the Black-Scholes Option Pricing Model	The inputs of the Black-Scholes option pricing model were as follows: As of December 31, Assumptions 2015 2014 Closing price of the Common Stock $18.25 $51.61 Exercise price $13.00 $13.00 Estimated price volatility * 55 % 55 % Contractual term 0.58 years 1.33 years * Represents the upper end of the range of implied volatility of publicly traded call options of benchmark companies. The inputs of the Black-Scholes option pricing model were as follows: Assumptions December 31, 2017 Market value of the Common Stock $7.50 Exercise price varies Risk-free interest rate 1.8 % Estimated price volatility 95 % Contractual term 1.0 year Dividend yield —

Income Taxes (Tables)

Income Taxes (Tables)	12 Months Ended
	Dec. 31, 2017
Income Tax Disclosure [Abstract]
Schedule of Expense (Benefit) for Income Taxes	Income tax expense (benefit) was as follows: (in thousands) For the Year Ended December 31, 2017 2016 2015 (Restated) 2014 (Restated) Current tax expense (benefit): Federal $ 127 $ (6,568 ) $ (859 ) $ 7,476 State 77 60 215 1,892 Total $ 204 $ (6,508 ) $ (644 ) $ 9,368 Deferred tax expense (benefit) Federal $ 100 $ 13,907 $ (6,713 ) $ (1,183 ) State 139 4,214 (2,345 ) (441 ) Total deferred tax expense (benefit) 239 18,121 (9,058 ) (1,624 ) Total tax expense (benefit) $ 443 $ 11,613 $ (9,702 ) $ 7,744
Reconciliation of Effective Tax Rate to the Statutory Rate	A reconciliation between the Company’s effective tax rate on (loss) income before income taxes and the statutory tax rate was as follows: (in thousands) For the Year Ended December 31, 2017 2016 2015 (Restated) 2014 (Restated) Amount Percent Amount Percent Amount Percent Amount Percent Income tax (benefit) expense at federal statutory rate $ (16,037 ) 34.0 % $ (12,192 ) 34.0 % $ (4,282 ) 34.0 % $ 9,935 34.0 % State income tax, net of federal benefit (2,283 ) 4.8 % (1,758 ) 4.9 % (1,101 ) 8.7 % 1,295 4.4 % Non-deductible warrants (income)/expense 1,360 (2.9 )% (481 ) 1.3 % (3,162 ) 25.1 % (2,098 ) (7.2 )% Domestic production activity — — % — — % — — % (334 ) (1.1 )% Other permanent differences 106 (0.2 )% 110 (0.3 )% 137 (1.1 )% 191 0.7 % Research and development tax credits (426 ) 0.9 % (837 ) 2.3 % (1,632 ) 13.0 % (1,953 ) (6.7 )% Tax reserve reassessment 104 (0.2 )% (141 ) 0.4 % 412 (3.3 )% 246 0.8 % Federal tax rate change 10,899 (23.1 )% — — % — — % — — % Change in valuation allowance 4,956 (10.4 )% 26,846 (74.9 )% — — % — — % 3PI Settlement 1,976 (4.2 )% — — % — — % — — % Other, net (212 ) 0.4 % 66 (0.1 )% (74 ) 0.6 % 462 1.6 % Income tax expense (benefit) $ 443 (0.9 )% $ 11,613 (32.4 )% $ (9,702 ) 77.0 % $ 7,744 26.5 %
Schedule of Significant Components of the Deferred Income Tax Assets and Liabilities	Significant components of deferred income tax assets and liabilities consisted of the following: (in thousands) As of December 31, 2017 2016 2015 (Restated) 2014 (Restated) Deferred tax assets: Net operating loss carryforwards $ 15,399 $ 1,154 $ 66 $ — Research and development credits 2,806 2,118 139 — Other state credits 989 407 164 — Inventory 2,560 5,837 5,094 3,035 Allowances and bad debts 596 501 334 119 Accrued warranty 3,387 3,820 1,413 948 Accrued wages and benefits 351 786 893 917 Stock-based compensation 645 1,021 756 576 Capitalized research and development costs 1,090 2,291 2,617 2,316 Intangible amortization 1,734 4,519 4,311 — Other 3,397 6,638 5,069 3,615 Total deferred tax assets 32,954 29,092 20,856 11,526 Valuation allowance (31,992 ) (26,847 ) — — Total deferred tax assets, net of valuation allowance $ 962 $ 2,245 $ 20,856 $ 11,526 Deferred tax liabilities: Intangible amortization $ — $ — $ — $ (1,091 ) Tax depreciation in excess of book depreciation on property, plant and equipment (1,665 ) (2,709 ) (3,199 ) (1,870 ) Total deferred tax liabilities $ (1,665 ) $ (2,709 ) $ (3,199 ) $ (2,961 ) Net deferred tax (liability) asset $ (703 ) $ (464 ) $ 17,657 $ 8,565 The Company’s net deferred tax assets and liabilities are presented as follows in the Consolidated Balance Sheets: (in thousands) As of December 31, 2017 2016 2015 (Restated) 2014 (Restated) Current deferred tax assets, net $ — $ — $ — $ 8,552 Non-current deferred tax asset/(liabilities), net (703 ) (464 ) 17,657 13 Net deferred tax (liability) asset $ (703 ) $ (464 ) $ 17,657 $ 8,565
Schedule of the Change in Unrecognized Tax Benefits	The change in unrecognized tax benefits excluding interest and penalties were as follows: (in thousands) For the Year Ended December 31, 2017 2016 2015 2014 Unrecognized Tax Benefits Excluding Interest and Penalties (Restated) (Restated) Balance at beginning of year $ 1,202 $ 1,338 $ 894 $ 614 Additions based on tax positions related to the current year 105 168 525 373 Additions/(reductions) for tax positions of prior years — (304 ) (81 ) (93 ) Balance at end of year $ 1,307 $ 1,202 $ 1,338 $ 894
Summary of Income Tax Examinations	With few exceptions, the major jurisdictions subject to examination by the relevant tax authorities and open tax years, stated as the Company’s fiscal years, are as follows: Jurisdiction Open Tax Years U.S. Federal 2014 - 2017 U.S. States 2013 - 2017

Stockholders' Equity (Tables)

Stockholders' Equity (Tables)	12 Months Ended
	Dec. 31, 2017
Equity [Abstract]
Schedule of Common Stock Outstanding Roll Forward	The changes in shares of Common and Treasury Stock were as follows: (in thousands) Common Shares Originally Issued Treasury Stock Shares Common Shares Outstanding Balance as of December 31, 2013 (Restated) 11,299 777 10,522 Net shares issued for Stock awards — (100 ) 100 Warrants exercised 109 — 109 Balance as of December 31, 2014 (Restated) 11,408 677 10,731 Net shares issued for Stock awards — (17 ) 17 Warrants exercised 5 — 5 Balance as of December 31, 2015 (Restated) 11,413 660 10,753 Net shares issued for Stock awards — (15 ) 15 Warrants exercised 154 — 154 Balance as of December 31, 2016 11,567 645 10,922 Net shares issued for Stock awards — (11 ) 11 Shares issued to Weichai * 2,729 — 2,729 Shares converted from Series B Convertible Preferred Stock * 4,771 — 4,771 Balance as of December 31, 2017 19,067 634 18,433 * See Note 3. Weichai Transactions for additional information.

Stock-Based Compensation (Table

Stock-Based Compensation (Tables)	12 Months Ended
	Dec. 31, 2017
Disclosure of Compensation Related Costs, Share-based Payments [Abstract]
Schedule of Fair Value Assumptions	The assumptions used for valuing the SARs granted in 2012 included the following: Assumptions 2012 SARs Market closing price of the Common Stock $ 16.50 Exercise price $ 22.07 Risk-free interest rate 0.92 % Expected volatility 55.0 % Expected term 6 years Dividend yield — % The assumptions used for valuing the February 2016 SAR awards included the following: Assumptions February 2016 SAR awards Market closing price of the Common Stock $ 10.76 Exercise price $ 11.25 Risk-free interest rate 1.36 % Estimated price volatility 55.0 % Expected term 5.75 years Dividend yield — % The assumptions used for valuing the incremental compensation related to the modification included the following: Assumptions Pre-Modification Post-Modification Market closing price of the Common Stock $ 53.64 $ 51.13 Exercise price $ 22.07 $ 22.07 Risk-free interest rate 1.10 % 1.53 % Expected volatility 50.0 % 50.0 % Expected term 3.5 years 4.9 years Dividend yield — % — % Fair value of the Common Stock $ 31.97 $ 33.81 The assumptions used for valuing the 2017 SARs included the following: Assumptions 2017 SARs Market closing price of the Common Stock $ 7.37 Exercise price $ 7.37 Risk-free interest rate 2.1 % Estimated price volatility 58.5 % Expected term 6.00 years Dividend yield — % The assumptions used for valuing the SARs granted in 2015 included the following: Assumptions 2015 SARs Market closing price of the Common Stock $ 24.41 Exercise price $ 24.41 Risk-free interest rate 1.76 % Expected volatility 50.0 % Expected term 7.25 years Dividend yield — %
Schedule of SAR Activity	SAR activity consisted of the following: Number of Shares under SARs Shares Weighted-Average Exercise Price Weighted-Average Remaining Contractual Term (years) Aggregate Intrinsic Value (in thousands) Outstanding at December 31, 2013 362,581 $ 22.07 8.44 $ 19,228 Granted — — — Exercised (120,000 ) 22.07 6,673 Forfeited — — — Expired — — — Outstanding at December 31, 2014 242,581 22.07 7.44 7,166 Exercisable at December 31, 2014 61,291 $ 22.07 7.44 $ 1,811 Number of Shares under SARs Shares Weighted-Average Exercise Price Weighted-Average Remaining Contractual Term (years) Aggregate Intrinsic Value (in thousands) Outstanding at December 31, 2014 242,581 $ 22.07 7.44 $ 7,166 Granted 60,000 24.41 — Exercised — — — Forfeited — — — Expired — — — Outstanding at December 31, 2015 302,581 22.53 7.10 — Exercisable at December 31, 2015 61,291 $ 22.07 6.44 $ — Number of Shares under SARs Shares Weighted-Average Exercise Price Weighted-Average Remaining Contractual Term (years) Aggregate Intrinsic Value (in thousands) Outstanding at December 31, 2015 302,581 $ 22.53 7.10 $ — Granted 106,800 11.43 — Exercised — — — Forfeited (195,490 ) 21.28 — Expired (61,291 ) 22.07 — Outstanding at December 31, 2016 152,600 16.55 9.02 — Exercisable at December 31, 2016 — $ — $ — Number of Shares under SARs Shares Weighted-Average Exercise Price Weighted-Average Remaining Contractual Term (years) Aggregate Intrinsic Value (in thousands) Outstanding at December 31, 2016 152,600 $ 16.55 9.02 $ — Granted 5,000 7.37 — Exercised — — — Forfeited (67,130 ) 23.16 — Expired (6,750 ) 12.68 — Outstanding at December 31, 2017 83,720 11.02 8.21 1,000 Exercisable at December 31, 2017 39,360 $ 11.25 8.15 $ —
Schedule of Restricted Stock Activity	Restricted stock activity consisted of the following: Shares Weighted-Average Grant Date Fair Value Balance as of December 31, 2013 162,993 $ 39.29 Granted 23,000 71.47 Forfeited (12,000 ) 60.44 Vested (19,742 ) 41.89 Balance as of December 31, 2014 154,251 42.11 Granted 1,000 28.48 Forfeited (800 ) 65.51 Vested (24,207 ) 42.63 Balance as of December 31, 2015 130,244 41.77 Granted 750 18.50 Forfeited (4,668 ) 36.00 Vested (21,986 ) 42.96 Balance as of December 31, 2016 104,340 41.61 Granted 437,472 8.13 Forfeited (29,144 ) 38.33 Vested (16,395 ) 44.19 Balance as of December 31, 2017 496,273 $ 12.20

Earnings Per Share (Tables)

Earnings Per Share (Tables)	12 Months Ended
	Dec. 31, 2017
Earnings Per Share [Abstract]
Schedule of Basic and Diluted Earnings (Loss) Per Share	The computations of basic and diluted EPS were as follows: (in thousands, except per share basis) For the Year Ended December 31, 2017 2016 2015 (Restated) 2014 (Restated) Numerator: Net (loss) income $ (47,612 ) $ (47,472 ) $ (2,891 ) $ 21,477 Less: Deemed dividend on Series B convertible preferred stock (37,860 ) — — — Net (loss) income available to common stockholders - basic (85,472 ) (47,472 ) (2,891 ) 21,477 Exclude (gain) loss from change in fair value of warrants — (1,413 ) (9,300 ) (6,170 ) Net (loss) income available to common stockholders - diluted $ (85,472 ) $ (48,885 ) $ (12,191 ) $ 15,307 Denominator: Shares used in computing net (loss) income per share: Weighted-average basic shares outstanding 13,787 10,931 10,808 10,705 Effect of dilutive securities — — 183 426 Weighted-average common shares outstanding — diluted 13,787 10,931 10,991 11,131 (Loss) earnings per common share: (Loss) earnings per share — basic $ (6.20 ) $ (4.34 ) $ (0.27 ) $ 2.01 (Loss) earnings per share — diluted $ (6.20 ) $ (4.47 ) $ (1.11 ) $ 1.38

Selected Quarterly Financial _2

Selected Quarterly Financial Data (Unaudited) (Tables)	12 Months Ended
	Dec. 31, 2017
Quarterly Financial Information Disclosure [Abstract]
Quarterly Financial Information	POWER SOLUTIONS INTERNATIONAL, INC. CONDENSED CONSOLIDATED BALANCE SHEETS (in thousands) As of March 31, 2017 June 30, September 30, 2017 ASSETS Current assets Cash and cash equivalents $ 342 $ — $ — Accounts receivable, net 64,305 56,673 60,811 Income tax receivable 6,829 1,996 841 Inventories, net 97,286 103,335 113,074 Prepaid expenses and other current assets 15,291 12,453 14,536 Total current assets 184,053 174,457 189,262 Property, plant and equipment, net 19,230 19,050 18,974 Intangible assets, net 24,819 23,610 22,401 Goodwill 29,835 29,835 29,835 Other noncurrent assets 5,053 4,518 6,035 TOTAL ASSETS $ 262,990 $ 251,470 $ 266,507 LIABILITIES, MEZZANINE AND STOCKHOLDERS’ EQUITY Current liabilities Accounts payable $ 67,167 $ 55,610 $ 54,195 Contingent consideration 30 29 20 Revolving line of credit, current 16,887 25,263 41,332 Other accrued liabilities 35,234 35,379 41,393 Total current liabilities 119,318 116,281 136,940 Deferred income taxes 933 1,066 1,210 Warrants 20,700 21,500 23,200 Long-term debt, less current maturities, net 54,045 54,168 54,305 Other noncurrent liabilities 13,328 12,438 13,312 TOTAL LIABILITIES $ 208,324 $ 205,453 $ 228,967 MEZZANINE EQUITY Series B convertible preferred stock, net of issuance costs $ 24,617 $ 27,807 $ 31,411 STOCKHOLDERS’ EQUITY Preferred stock $ — $ — $ — Common stock 14 14 14 Additional paid-in capital 100,686 96,543 91,737 Accumulated deficit (59,070 ) (66,817 ) (76,018 ) Treasury stock, at cost (11,582 ) (11,530 ) (9,604 ) TOTAL STOCKHOLDERS’ EQUITY 30,048 18,210 6,129 TOTAL LIABILITIES, MEZZANINE AND STOCKHOLDERS’ EQUITY $ 262,990 $ 251,470 $ 266,507 POWER SOLUTIONS INTERNATIONAL, INC. CONDENSED CONSOLIDATED BALANCE SHEETS (in thousands) As of March 31, 2016 (Restated) June 30, September 30, 2016 ASSETS Current assets Cash and cash equivalents $ 1,495 $ 435 $ 1,610 Accounts receivable, net 45,384 57,884 53,364 Income tax receivable 1,723 3,384 5,737 Inventories, net 139,519 115,062 111,133 Prepaid expenses and other current assets 4,132 4,026 5,146 Total current assets 192,253 180,791 176,990 Property, plant and equipment, net 20,662 20,386 20,257 Intangible assets, net 30,316 28,888 27,459 Goodwill 29,835 29,835 29,835 Deferred income taxes 19,285 — — Other noncurrent assets 2,664 2,621 2,821 TOTAL ASSETS $ 295,015 $ 262,521 $ 257,362 LIABILITIES AND STOCKHOLDERS’ EQUITY Current liabilities Accounts payable $ 43,160 $ 49,729 $ 45,764 Current maturities of long-term debt — — 375 Contingent consideration 5,481 100 88 Revolving line of credit, current — 14,038 16,994 Other accrued liabilities 17,929 19,182 22,405 Total current liabilities 66,570 83,049 85,626 Revolving line of credit 80,568 — — Deferred income taxes — 372 522 Warrants 226 — — Long-term debt, less current maturities, net 53,799 110,929 111,517 Other noncurrent liabilities 11,952 12,833 12,730 TOTAL LIABILITIES $ 213,115 $ 207,184 $ 210,395 STOCKHOLDERS’ EQUITY Preferred stock $ — $ — $ — Common stock 11 12 12 Additional paid-in capital 83,729 86,043 86,408 Retained earnings (accumulated deficit) 9,612 (19,180 ) (27,895 ) Treasury stock, at cost (11,452 ) (11,537 ) (11,558 ) TOTAL STOCKHOLDERS’ EQUITY 81,900 55,337 46,967 TOTAL LIABILITIES AND STOCKHOLDERS’ EQUITY $ 295,015 $ 262,521 $ 257,362 POWER SOLUTIONS INTERNATIONAL, INC. CONDENSED CONSOLIDATED STATEMENTS OF OPERATIONS (in thousands, except per share amounts) For the Quarter Ended March 31, 2017 June 30, 2017 September 30, 2017 December 31, 2017 Net sales $ 84,265 $ 100,922 $ 99,953 $ 131,476 Cost of sales 74,497 88,443 86,702 115,981 Gross profit 9,768 12,479 13,251 15,495 Operating expenses: Research, development and engineering expenses 3,950 3,848 5,687 6,459 Selling, general and administrative expenses 10,209 10,688 12,062 11,297 Asset impairment charges — — — 1 Amortization of intangible assets 1,209 1,209 1,210 1,210 Total operating expenses 15,368 15,745 18,959 18,967 Operating loss (5,600 ) (3,266 ) (5,708 ) (3,472 ) Other expense: Interest expense 6,080 1,404 1,654 1,703 Loss from change in fair value of warrants — 800 1,700 1,500 Loss on debt extinguishment and modifications 11,921 — — — Other expense (income), net 453 2,142 (9 ) (225 ) Total other expense 18,454 4,346 3,345 2,978 Loss before income taxes (24,054 ) (7,612 ) (9,053 ) (6,450 ) Income tax expense (benefit) 479 135 149 (320 ) Net loss (24,533 ) (7,747 ) (9,202 ) (6,130 ) Deemed dividend on Series B convertible stock — (3,190 ) (3,603 ) (31,067 ) Net loss available to common stockholders $ (24,533 ) $ (10,937 ) $ (12,805 ) $ (37,197 ) POWER SOLUTIONS INTERNATIONAL, INC. CONDENSED CONSOLIDATED STATEMENTS OF OPERATIONS (in thousands, except per share amounts) For the Quarter Ended March 31, 2016 (Restated) June 30, 2016 September 30, 2016 December 31, 2016 Net sales $ 76,470 $ 85,771 $ 78,944 $ 98,280 Cost of sales 69,827 81,253 72,820 86,376 Gross profit 6,643 4,518 6,124 11,904 Operating expenses: Research, development and engineering expenses 4,904 4,817 4,498 4,742 Selling, general and administrative expenses 6,405 6,699 6,855 8,563 Asset impairment charges 345 1,064 38 167 Amortization of intangible assets 1,428 1,429 1,429 1,430 Contingent consideration — (283 ) — — Total operating expenses 13,082 13,726 12,820 14,902 Operating loss (6,439 ) (9,208 ) (6,696 ) (2,998 ) Other expense: Interest expense 1,438 1,649 3,726 4,402 Gain from change in fair value of warrants (1,256 ) (157 ) — — Loss on debt extinguishment and modifications — — 25 332 Other expense, net 59 92 62 146 Total other expense 241 1,584 3,813 4,880 Loss before income taxes (6,680 ) (10,792 ) (10,509 ) (7,878 ) Income tax (benefit) expense (3,357 ) 18,000 (1,792 ) (1,238 ) Net loss $ (3,323 ) $ (28,792 ) $ (8,717 ) $ (6,640 ) POWER SOLUTIONS INTERNATIONAL, INC. CONDENSED CONSOLIDATED STATEMENTS OF CASH FLOWS (in thousands) For the Year to Date Period Ended March 31, 2017 June 30, September 30, 2017 Cash provided by (used in) operating activities Net loss $ (24,533 ) $ (32,280 ) $ (41,482 ) Adjustments to reconcile net (loss) income to net cash provided by operating activities: Amortization of intangible assets 1,209 2,419 3,628 Depreciation 1,172 2,342 3,502 Change in valuation of warrants — 800 2,500 Stock compensation expense (865 ) (1,028 ) (297 ) Amortization of financing fees 3,109 3,441 3,778 Deferred income taxes 469 602 746 Loss on extinguishment of debt 11,921 11,921 11,921 Provision for doubtful accounts 48 131 216 Provision for inventory obsolescence 146 539 882 Loss on disposal of fixed assets 10 66 115 Other sources, net 135 198 189 Changes in operating assets and liabilities: Trade accounts receivable, net (4,017 ) 3,532 (691 ) Inventory, net 3,122 (3,326 ) (13,408 ) Prepaid expenses and other assets (1,624 ) 1,238 (1,359 ) Trade accounts payable 15,186 3,244 1,879 Income taxes refundable 298 5,135 6,293 Accrued expenses 2,432 3,242 8,867 Other noncurrent liabilities (121 ) (894 ) (821 ) Net cash provided by (used in) operating activities 8,097 1,322 (13,542 ) Cash (used in) provided by investing activities Capital expenditures (1,896 ) (2,669 ) (3,856 ) Other sources, net — 245 245 Net cash used in investing activities (1,896 ) (2,424 ) (3,611 ) Cash (used in) provided by financing activities Repayments of issuance of long-term debt (71,400 ) (71,400 ) (71,400 ) Financing fees (253 ) (928 ) (928 ) Net proceeds from stock offering and warrant 59,396 59,396 59,396 Proceeds from revolving line of credit 85,945 209,082 324,416 Repayments of revolving line of credit (81,833 ) (196,593 ) (295,859 ) Acquisition of businesses contingent consideration payments (6 ) (9 ) (19 ) Other uses, net — (738 ) (745 ) Net cash (used in) provided by financing activities (8,151 ) (1,190 ) 14,861 Decrease in cash (1,950 ) (2,292 ) (2,292 ) Cash at beginning of the year 2,292 2,292 2,292 Cash at end of the period $ 342 $ — $ — POWER SOLUTIONS INTERNATIONAL, INC. CONDENSED CONSOLIDATED STATEMENTS OF CASH FLOWS (in thousands) For the Year to Date Period Ended March 31, 2016 (Restated) June 30, September 30, 2016 Cash provided by (used in) operating activities Net loss $ (3,323 ) $ (32,115 ) $ (40,832 ) Adjustments to reconcile net (loss) income to net cash provided by operating activities: Amortization of intangible assets 1,429 2,857 4,286 Depreciation 1,118 2,250 3,412 Change in valuation of warrants (1,256 ) (1,413 ) (1,413 ) Stock compensation expense 441 692 1,188 Amortization of financing fees 143 445 1,451 Deferred income taxes (1,628 ) 18,029 18,179 Loss on extinguishment of debt — — 25 Asset impairment charges 345 1,410 1,447 Change in valuation of contingent consideration — (283 ) (283 ) (Income) provision for doubtful accounts (10 ) 24 69 Provision for inventory obsolescence 288 3,441 3,928 Loss (gain) on disposal of fixed assets 236 (852 ) (846 ) Other sources, net 113 205 266 Changes in operating assets and liabilities: Trade accounts receivable, net 25,158 12,624 17,100 Inventory, net 22,288 42,947 46,390 Prepaid expenses and other assets (207 ) (1,261 ) (2,443 ) Trade accounts payable (36,459 ) (30,324 ) (34,056 ) Income taxes refundable (payable) 3,441 1,783 (682 ) Accrued expenses 1,891 3,041 6,099 Other noncurrent liabilities (98 ) 1,011 1,028 Net cash provided by operating activities 13,910 24,511 24,313 Cash flows from investing activities Capital expenditures (1,099 ) (1,977 ) (3,286 ) Proceeds from disposal of assets — 2,466 2,466 Other uses, net — — (245 ) Net cash (used in) provided by investing activities (1,099 ) 489 (1,065 ) Cash flows from financing activities Proceeds from issuance of long-term debt — 60,000 60,000 Financing fees — (3,402 ) (3,402 ) Net proceeds from stock offering and warrant — 2,001 2,001 Proceeds from revolving line of credit 46,902 111,902 196,179 Repayments of revolving line of credit (63,634 ) (195,164 ) (276,484 ) Acquisition of businesses contingent consideration payments (3,029 ) (8,258 ) (8,279 ) Other uses, net — (89 ) (98 ) Net cash used in financing activities (19,761 ) (33,010 ) (30,083 ) Decrease in cash (6,950 ) (8,010 ) (6,835 ) Cash at beginning of the year 8,445 8,445 8,445 Cash at end of the period $ 1,495 $ 435 $ 1,610
Effect of Restatement	The following table sets forth the effects of the restatement adjustments on revenue and pretax income (loss) in the Consolidated Statements of Operations for the years ended December 31, 2015 and 2014. Due to the substantial number of restatement adjustments, each of the restatement categories listed in the table below may represent multiple related adjustments that have been aggregated for disclosure purposes. (in thousands) For the Year Ended December 31, 2015 2014 Net Sales Income (Loss) Before Income Taxes Net Sales Income (Loss) Before Income Taxes Previously reported $ 389,446 $ 13,890 $ 347,995 $ 34,539 Restatement adjustments: Revenue recognition adjustments (27,059 ) (9,215 ) (415 ) (2,700 ) Product development cost — (1,001 ) — (2,397 ) Inventory valuation — (1,069 ) — 38 Impairment of long-lived assets — (11,733 ) — (310 ) Product warranty — (2,484 ) — 591 Accrued liabilities — (1,106 ) — 591 Purchase accounting — — — (845 ) Equity investment — 125 — (286 ) Net restatement adjustments (27,059 ) (26,483 ) (415 ) (5,318 ) Restated $ 362,387 $ (12,593 ) $ 347,580 $ 29,221 The following table presents the effect of the restatement adjustments and reclassifications on the Consolidated Statement of Operations for 2015: (in thousands, except for per share data) Year Ended December 31, 2015 Previously Reported Restatement Adjustments and Reclassifications Restated Net sales $ 389,446 $ (27,059 ) $ 362,387 Cost of sales 326,612 (15,464 ) 311,148 Gross profit 62,834 (11,595 ) 51,239 Operating expenses: Research, development and engineering expenses 21,681 1,893 23,574 Selling, general and administrative expenses 27,376 1,461 28,837 Asset impairment charge — 11,686 11,686 Amortization of intangible assets 4,582 — 4,582 Change in fair value of contingent consideration — (23 ) — (23 ) Total operating expenses 53,639 15,017 68,656 Operating income (loss) 9,195 (26,612 ) (17,417 ) Other (income) expense: Interest expense 4,327 (7 ) 4,320 Contingent consideration 48 (48 ) — Gain from change in fair value of warrants (9,299 ) (1 ) (9,300 ) Loss on debt extinguishment and modifications — 12 12 Other expense, net 229 (85 ) 144 Total other income (4,695 ) (129 ) (4,824 ) Income (loss) before income taxes 13,890 (26,483 ) (12,593 ) Income tax benefit (388 ) (9,314 ) (9,702 ) Net income (loss) $ 14,278 $ (17,169 ) $ (2,891 ) Weighted-average common shares outstanding: Basic 10,808 — 10,808 Diluted 11,074 (83 ) 10,991 Earnings (loss) per common share: Basic $ 1.32 $ (1.59 ) $ (0.27 ) Diluted $ 0.45 $ (1.56 ) $ (1.11 ) The following table presents the effect of the restatement adjustments and reclassifications on the Consolidated Statement of Operations for 2014: (in thousands, except for per share data) Year Ended December 31, 2014 Previously Reported Restatement Adjustments and Reclassifications Restated Net sales $ 347,995 $ (415 ) $ 347,580 Cost of sales 280,950 2,590 283,540 Gross profit 67,045 (3,005 ) 64,040 Operating expenses: Research, development and engineering expenses 16,900 2,405 19,305 Selling, general and administrative expenses 23,088 54 23,142 Asset impairment charge — 310 310 Amortization of intangible assets 1,013 — 1,013 Change in fair value of contingent consideration — (3,840 ) (3,840 ) Total operating expenses 41,001 (1,071 ) 39,930 Operating income 26,044 (1,934 ) 24,110 Other expense (income): Interest expense 1,331 11 1,342 Contingent consideration (3,840 ) 3,840 — Gain from change in fair value of warrants (6,169 ) (1 ) (6,170 ) Other expense (income), net 183 (466 ) (283 ) Total other income (8,495 ) 3,384 (5,111 ) Income before income taxes 34,539 (5,318 ) 29,221 Income tax expense 10,813 (3,069 ) 7,744 Net income $ 23,726 $ (2,249 ) $ 21,477 Weighted-average common shares outstanding: Basic 10,707 (2 ) 10,705 Diluted 11,132 (1 ) 11,131 Earnings (loss) per common share: Basic $ 2.22 $ (0.21 ) $ 2.01 Diluted $ 2.13 $ (0.75 ) $ 1.38 The following table sets forth the effects of the restatement adjustments and reclassifications adjustments on the Company's Consolidated Balance Sheet as of December 31, 2015: (in thousands) As of December 31, 2015 Previously Reported Restatement Adjustments and Reclassifications Restated ASSETS Current assets Cash and cash equivalents $ 8,445 $ — $ 8,445 Accounts receivable, net 104,365 (33,833 ) 70,532 Income tax receivable 5,230 35 5,265 Inventories, net 130,347 31,748 162,095 Prepaid expenses and other current assets 4,288 (1,585 ) 2,703 Total current assets 252,675 (3,635 ) 249,040 Property, plant and equipment, net 26,001 (3,192 ) 22,809 Intangible assets, net 31,745 — 31,745 Goodwill 41,466 (11,631 ) 29,835 Deferred income taxes 819 16,838 17,657 Other noncurrent assets 7,230 (4,479 ) 2,751 TOTAL ASSETS $ 359,936 $ (6,099 ) $ 353,837 LIABILITIES AND STOCKHOLDERS’ EQUITY Current liabilities Accounts payable $ 76,078 $ 3,745 $ 79,823 Contingent consideration 8,788 (513 ) 8,275 Other accrued liabilities 14,396 3,450 17,846 Total current liabilities 99,262 6,682 105,944 Revolving line of credit 97,299 — 97,299 Warrants 1,482 — 1,482 Long-term debt, less current maturities, net 53,820 (15 ) 53,805 Other noncurrent liabilities 1,776 8,658 10,434 TOTAL LIABILITIES $ 253,639 $ 15,325 $ 268,964 STOCKHOLDERS’ EQUITY Preferred stock $ — $ — $ — Common stock 12 (1 ) 11 Additional paid-in capital 75,179 8,198 83,377 Retained earnings 35,356 (22,419 ) 12,937 Treasury stock, at cost (4,250 ) (7,202 ) (11,452 ) TOTAL STOCKHOLDERS’ EQUITY 106,297 (21,424 ) 84,873 TOTAL LIABILITIES AND STOCKHOLDERS’ EQUITY $ 359,936 $ (6,099 ) $ 353,837 The following table sets forth the effects of the restatement adjustments and reclassifications on the Company's Consolidated Balance Sheet as of December 31, 2014: (in thousands) As of December 31, 2014 Previously Reported Restatement Adjustments and Reclassifications Restated ASSETS Current assets Cash and cash equivalents $ 6,561 $ — $ 6,561 Accounts receivable, net 81,740 (5,474 ) 76,266 Inventories, net 93,903 12,347 106,250 Prepaid expenses and other current assets 4,801 39 4,840 Deferred income taxes 3,998 4,554 8,552 Total current assets 191,003 11,466 202,469 Property, plant and equipment, net 20,892 (2,938 ) 17,954 Intangible assets, net 21,392 (200 ) 21,192 Goodwill 23,546 (132 ) 23,414 Deferred income tax asset — 13 13 Other noncurrent assets 5,804 (3,901 ) 1,903 TOTAL ASSETS $ 262,637 $ 4,308 $ 266,945 LIABILITIES AND STOCKHOLDERS’ EQUITY Current liabilities Accounts payable $ 60,877 $ 6,836 $ 67,713 Current maturities of long-term debt 1,667 — 1,667 Other accrued liabilities 13,504 4,678 18,182 Total current liabilities 76,048 11,514 87,562 Revolving line of credit 78,030 — 78,030 Deferred income taxes 3,241 (3,241 ) — Warrants 11,036 — 11,036 Long-term debt, less current maturities, net 2,361 — 2,361 Other noncurrent liabilities 1,122 351 1,473 TOTAL LIABILITIES $ 171,838 $ 8,624 $ 180,462 STOCKHOLDERS’ EQUITY Preferred stock $ — $ — $ — Common stock 12 (1 ) 11 Additional paid-in capital 73,959 7,787 81,746 Retained earnings 21,078 (5,250 ) 15,828 Treasury stock, at cost (4,250 ) (6,852 ) (11,102 ) TOTAL STOCKHOLDERS’ EQUITY 90,799 (4,316 ) 86,483 TOTAL LIABILITIES AND STOCKHOLDERS’ EQUITY $ 262,637 $ 4,308 $ 266,945 The following table sets forth the effect of the restatement adjustments on the components of total stockholders, equity as of December 31, 2013: (in thousands) As of December 31, 2013 Previously Reported Restatement Adjustments Restated Preferred stock $ — $ — $ — Common Stock 11 — 11 Additional paid-in capital 57,308 4,622 61,930 Accumulated deficit (2,649 ) (3,079 ) (5,728 ) Treasury stock, at cost (4,250 ) (4,435 ) (8,685 ) Total stockholders' equity $ 50,421 $ (2,891 ) $ 47,530 The following table summarizes the effects of the restatement on the Company's Consolidated Statements of Changes in Stockholders’ Equity as of December 31, 2015 and 2014: (in thousands) Year Ended December 31, 2015 2014 Stockholders' equity, as previously reported $ 106,297 $ 90,799 Effect of restatement adjustments on net income/retained earnings (21,424 ) (4,316 ) Stockholders' equity, restated $ 84,873 $ 86,483 The following table includes comparison of selected previously reported and restated information from the Company's Consolidated Statements of Cash Flows for 2015 and 2014: (in thousands) For the Year Ended December 31, 2015 2014 Previously Reported Restated Previously Reported Restated Net cash used in operating activities $ (23,049 ) $ (22,815 ) $ (15,685 ) $ (15,094 ) Net cash used in investing activities (43,570 ) (43,805 ) (51,713 ) (52,322 ) Net cash provided by financing activities 68,503 68,504 67,653 67,671 Increase in cash 1,884 1,884 255 255 Cash at beginning of year 6,561 6,561 6,306 6,306 Cash at end of year $ 8,445 $ 8,445 $ 6,561 $ 6,561 The following table sets forth the effect of the restatement adjustments on the components of total stockholders' equity as of December 31, 2013: (in thousands) As of December 31, 2013 Stockholders' Equity Previously Reported Restatement Adjustments Restated Common stock $ 11 $ — $ 11 Additional paid-in capital 57,308 4,622 61,930 Accumulated deficit (2,648 ) (3,079 ) (5,649 ) Treasury stock, at cost (4,250 ) (4,435 ) (8,685 ) Total $ 50,421 $ (2,891 ) $ 47,607 The Company identified the following categories that required restatement or reclassification and were comprised of a number of related adjustments that have been aggregated for disclosure purposes: (in thousands) Three Months Ended March 31, 2016 Net Sales (Loss) Income Before Income Taxes Previously Reported $ 61,814 $ (8,931 ) Restatement adjustments: Revenue recognition adjustments $ 14,656 $ 3,111 Product development cost — 123 Inventory valuation — (404 ) Impairment of long-lived assets — (557 ) Product warranty — (319 ) Accrued liabilities — 422 Equity investment — (125 ) Net restatement adjustments 14,656 2,251 Restated $ 76,470 $ (6,680 ) The following table presents the effect of the restatement adjustments and reclassifications on the Consolidated Statement of Operations for three months ended March 31, 2016: (in thousands, except for per share data) Three Months Ended March 31, 2016 Previously Reported Restatement Adjustments and Reclassifications Restated Net sales $ 61,814 $ 14,656 $ 76,470 Cost of sales 57,758 12,069 69,827 Gross profit 4,056 2,587 6,643 Operating expenses: Research, development and engineering expenses 5,250 (346 ) 4,904 Selling, general and administrative expenses 6,058 347 6,405 Asset impairment charge — 345 345 Amortization of intangible assets 1,429 (1 ) 1,428 Total operating expenses 12,737 345 13,082 Operating loss (8,681 ) 2,242 (6,439 ) Other expense (income): Interest expense 1,421 17 1,438 Private placement warrants income (1,256 ) — (1,256 ) Other expense, net 85 (26 ) 59 Total other expense 250 (9 ) 241 Loss before income taxes (8,931 ) 2,251 (6,680 ) Income tax benefit (3,680 ) 323 (3,357 ) Net loss $ (5,251 ) $ 1,928 $ (3,323 ) Weighted-average common shares outstanding: Basic 10,819 — 10,819 Diluted 10,819 — 10,819 (Loss) earnings per common share: Basic $ (0.49 ) $ 0.07 $ (0.42 ) Diluted $ (0.49 ) $ 0.07 $ (0.42 ) as of March 31, 2016: (in thousands) As of March 31, 2016 Previously Reported Restatement Adjustments and Reclassifications Restated ASSETS Current assets Cash and cash equivalents $ 1,495 $ — $ 1,495 Accounts receivable, net 63,163 (17,779 ) 45,384 Income tax receivable — 1,723 1,723 Inventories, net 120,735 18,784 139,519 Prepaid expenses and other current assets 9,496 (5,364 ) 4,132 Total current assets 194,889 (2,636 ) 192,253 Property, plant and equipment, net 24,289 (3,627 ) 20,662 Intangible assets, net 30,316 — 30,316 Goodwill 41,466 (11,631 ) 29,835 Deferred income taxes 819 18,466 19,285 Other noncurrent assets 7,181 (4,517 ) 2,664 TOTAL ASSETS $ 298,960 $ (3,945 ) $ 295,015 LIABILITIES AND STOCKHOLDERS’ EQUITY Current liabilities Accounts payable $ 41,491 $ 1,669 $ 43,160 Contingent consideration — 5,481 5,481 Other accrued liabilities 19,692 (1,763 ) 17,929 Total current liabilities 61,183 5,387 66,570 Revolving line of credit 80,568 — 80,568 Warrants 226 — 226 Long-term debt, less current maturities, net 53,946 (147 ) 53,799 Other noncurrent liabilities 1,670 10,282 11,952 TOTAL LIABILITIES $ 197,593 $ 15,522 $ 213,115 STOCKHOLDERS’ EQUITY Preferred stock $ — $ — $ — Common stock 12 (1 ) 11 Additional paid-in capital 75,500 8,229 83,729 Retained earnings 30,105 (20,493 ) 9,612 Treasury stock, at cost (4,250 ) (7,202 ) (11,452 ) TOTAL STOCKHOLDERS’ EQUITY 101,367 (19,467 ) 81,900 TOTAL LIABILITIES AND STOCKHOLDERS’ EQUITY $ 298,960 $ (3,945 ) $ 295,015 The restatement effect on the previously issued condensed Consolidated Statement of Cash Flow for the three months ended March 31, 2016 is as follows: (in thousands) Three Months Ended March 31, 2016 Previously Reported Restatement and Reclassification Reclassified Net cash provided by operating activities $ 9,995 $ 3,915 $ 13,910 Net cash used in investing activities (214 ) (885 ) (1,099 ) Net cash used in financing activities (16,731 ) (3,030 ) (19,761 ) Decrease in cash (6,950 ) — (6,950 ) Cash at beginning of year 8,445 — 8,445 Cash at end of period $ 1,495 $ — $ 1,495

Summary of Significant Accoun_4

Summary of Significant Accounting Policies and Other Information - Narrative (Details)	May 03, 2019	Apr. 01, 2019	Mar. 29, 2018	Mar. 31, 2017USD ($)	Mar. 31, 2017USD ($)	Dec. 31, 2017USD ($)board_memberreporting_unitsegment	Dec. 31, 2016USD ($)	Dec. 31, 2015USD ($)board_member	Dec. 31, 2014USD ($)	Jun. 30, 2016USD ($)	Dec. 31, 2013USD ($)
Concentration Risk [Line Items]
Number of board members | board_member						3		5
Number Of Board Members Eligible For Election | board_member						4
Number of operating segments | segment						1
Research and development and engineering expenses						$ 18,400,000	$ 17,100,000	$ 21,500,000	$ 17,400,000
Deferred tax valuation allowance						(31,992,000)	(26,847,000)	0	0	$ (17,800,000)
Unrecognized tax benefits						$ 1,307,000	1,202,000	1,338,000	894,000		$ 614,000
Asset impairment charges							$ 1,600,000	$ 100,000	$ 300,000
Number of reporting units | reporting_unit						2
Maximum
Concentration Risk [Line Items]
Amortization period						15 years
Wells Fargo Credit Agreement | Wells Fargo Revolving Credit Facility
Concentration Risk [Line Items]
Maturity, period prior to senior notes maturity						60 days
Share Purchase Agreement, Weichai Transaction
Concentration Risk [Line Items]
Consideration received on transaction				$ 60,000,000	$ 60,000,000
Subsequent Event | Wells Fargo Credit Agreement | Wells Fargo Revolving Credit Facility
Concentration Risk [Line Items]
Maturity, period prior to senior notes maturity			60 days
Subsequent Event | Series B | Share Purchase Agreement, Second Amended And Restated Warrant
Concentration Risk [Line Items]
Percent ownership of outstanding common stock	51.50%	51.00%
Weichai | Power Solutions International, Inc. | Subsequent Event | Chief Strategy Officer
Concentration Risk [Line Items]
Percentage of ownership after transaction	16.10%
Weichai | Power Solutions International, Inc. | Subsequent Event | Executive Vice President
Concentration Risk [Line Items]
Percentage of ownership after transaction	9.70%

Summary of Significant Accoun_5

Summary of Significant Accounting Policies and Other Information - Revenue from External Customers by Geographic Areas (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Disaggregation of Revenue [Line Items]
Net revenue recognized under year-end delivery incentives	$ 416,616	$ 339,465	$ 362,387	$ 347,580
North America
Disaggregation of Revenue [Line Items]
Net revenue recognized under year-end delivery incentives	355,268	304,621	327,479	323,474
Pacific Rim
Disaggregation of Revenue [Line Items]
Net revenue recognized under year-end delivery incentives	42,221	22,827	25,356	17,719
Europe
Disaggregation of Revenue [Line Items]
Net revenue recognized under year-end delivery incentives	14,205	11,065	9,552	5,705
Other
Disaggregation of Revenue [Line Items]
Net revenue recognized under year-end delivery incentives	4,922	952	0	682
Industrial
Disaggregation of Revenue [Line Items]
Net revenue recognized under year-end delivery incentives	190,724	164,245	174,203	155,935
Energy
Disaggregation of Revenue [Line Items]
Net revenue recognized under year-end delivery incentives	159,008	115,367	137,190	191,528
Transportation
Disaggregation of Revenue [Line Items]
Net revenue recognized under year-end delivery incentives	$ 66,884	$ 59,853	$ 50,994	$ 117

Summary of Significant Accoun_6

Summary of Significant Accounting Policies and Other Information - Schedules of Concentration of Risk, by Risk Factor (Details)	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Purchases | Supplier Concentration Risk | Supplier A
Concentration Risk [Line Items]
Concentration risk, percentage	21.00%	13.00%	11.00%	15.00%
Purchases | Supplier Concentration Risk | Supplier B
Concentration Risk [Line Items]
Concentration risk, percentage			18.00%	21.00%
Customer A | Net sales | Customer Concentration Risk
Concentration Risk [Line Items]
Concentration risk, percentage	16.00%	17.00%	16.00%	10.00%
Customer A | Accounts Receivable | Customer Concentration Risk
Concentration Risk [Line Items]
Concentration risk, percentage	18.00%		17.00%	15.00%
Customer B | Net sales | Customer Concentration Risk
Concentration Risk [Line Items]
Concentration risk, percentage	10.00%
Customer B | Accounts Receivable | Customer Concentration Risk
Concentration Risk [Line Items]
Concentration risk, percentage	13.00%
Customer C | Net sales | Customer Concentration Risk
Concentration Risk [Line Items]
Concentration risk, percentage		12.00%		10.00%
Customer C | Accounts Receivable | Customer Concentration Risk
Concentration Risk [Line Items]
Concentration risk, percentage			12.00%
Customer D | Accounts Receivable | Customer Concentration Risk
Concentration Risk [Line Items]
Concentration risk, percentage		30.00%
Customer E | Accounts Receivable | Customer Concentration Risk
Concentration Risk [Line Items]
Concentration risk, percentage				16.00%
Customer F | Accounts Receivable | Customer Concentration Risk
Concentration Risk [Line Items]
Concentration risk, percentage				11.00%
Customer G | Accounts Receivable | Customer Concentration Risk
Concentration Risk [Line Items]
Concentration risk, percentage			10.00%	11.00%

Summary of Significant Accoun_7

Summary of Significant Accounting Policies and Other Information - Schedule of Inventory, Current (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016
Inventories, Net
Raw materials	$ 71,732	$ 70,498	$ 102,912	$ 92,360
Work in process	4,535	9,270	12,315	6,021
Finished goods	16,684	30,862	52,136	11,904
Total Inventories	92,951	110,630	167,363	110,285
Inventory allowance	(6,227)	(10,082)	(5,268)	(4,035)
Inventories, net	86,724	100,548	162,095	106,250	$ 113,074	$ 103,335	$ 97,286	$ 111,133	$ 115,062	$ 139,519
Allowance for Doubtful Accounts Receivable
Balance at beginning of period	10,082	5,268	4,035	2,982
Charged to expense	421	5,341	1,712	1,856
Write-offs	(4,276)	(527)	(479)	(803)
Balance at end of year	$ 6,227	$ 10,082	$ 5,268	$ 4,035

Summary of Significant Accoun_8

Summary of Significant Accounting Policies and Other Information - Schedule of Prepaid Expense and Other Current Assets (Details) - USD ($) $ in Thousands	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Insurance proceeds receivable	$ 10,563				$ 8,500				$ 0	$ 0
Prepaid expenses	3,710				4,072				2,578	4,840
Other	86				1,072				125	0
Total	$ 14,359	$ 14,536	$ 12,453	$ 15,291	$ 13,644	$ 5,146	$ 4,026	$ 4,132	$ 2,703	$ 4,840

Summary of Significant Accoun_9

Summary of Significant Accounting Policies and Other Information - Property, Plant and Equipment (Details)	12 Months Ended
	Dec. 31, 2017
Buildings | Maximum
Property, Plant and Equipment [Line Items]
Useful life	39 years
Leasehold improvements
Property, Plant and Equipment [Line Items]
Useful life
Machinery and equipment | Maximum
Property, Plant and Equipment [Line Items]
Useful life	10 years
Machinery and equipment | Minimum
Property, Plant and Equipment [Line Items]
Useful life	1 year

Summary of Significant Accou_10

Summary of Significant Accounting Policies and Other Information - Schedule of Other Accrued Liabilities (Details) - USD ($) $ in Thousands	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Warranty	$ 12,628				$ 10,200				$ 4,429	$ 2,428	$ 1,274
Litigation reserves	12,137				10,287				3	0
Deferred revenue	2,822				1,818				3,564	4,602
Accrued compensation and benefits	2,593				3,975				3,825	5,476
Professional services	1,974				1,509				544	500
Income taxes payable	375				131				107	2,973
Other	5,833				4,587				5,374	2,203
Balance at end of year	$ 38,362	$ 41,393	$ 35,379	$ 35,234	$ 32,507	$ 22,405	$ 19,182	$ 17,929	$ 17,846	$ 18,182

Summary of Significant Accou_11

Summary of Significant Accounting Policies and Other Information - Schedule of Product Warranty Liability (Details) - USD ($) $ / shares in Units, $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Movement in Standard Product Warranty Accrual
Balance at beginning of year	$ 10,200	$ 4,429	$ 2,428	$ 1,274
Current year provision	5,405	5,716	2,953	1,348
Acquisitions	0	0	963	1,600
Changes in estimates for preexisting warranties	0	1,894	0	0
Payments made during the period	2,977	1,839	1,915	1,794
Balance at end of year	$ 12,628	10,200	$ 4,429	$ 2,428
Charges for adjustments for changes in estimates, net of tax		$ 1,200
Diluted share (in dollars per share)		$ 0.11

Restatement of Previously Iss_3

Restatement of Previously Issued Consolidated Financial Statements - Narrative (Details) $ in Thousands	3 Months Ended								6 Months Ended		9 Months Ended		12 Months Ended
	Dec. 31, 2017USD ($)board_member	Sep. 30, 2017USD ($)	Jun. 30, 2017USD ($)	Mar. 31, 2017USD ($)	Dec. 31, 2016USD ($)	Sep. 30, 2016USD ($)	Jun. 30, 2016USD ($)	Mar. 31, 2016USD ($)	Jun. 30, 2017USD ($)	Jun. 30, 2016USD ($)	Sep. 30, 2017USD ($)	Sep. 30, 2016USD ($)	Dec. 31, 2017USD ($)board_member	Dec. 31, 2016USD ($)	Dec. 31, 2015USD ($)board_member	Dec. 31, 2014USD ($)	Dec. 31, 2013USD ($)
Error Corrections and Prior Period Adjustments Restatement [Line Items]
Reduction to stockholders' equity balances	$ (32,172)	$ (6,129)	$ (18,210)	$ (30,048)	$ (40,660)	$ (46,967)	$ (55,337)	$ (81,900)	$ (18,210)	$ (55,337)	$ (6,129)	$ (46,967)	$ (32,172)	$ (40,660)	$ (84,873)	$ (86,483)	$ (47,607)
Net (loss) income	(6,130)	(9,202)	(7,747)	(24,533)	(6,640)	(8,717)	(28,792)	(3,323)	(32,280)	(32,115)	(41,482)	(40,832)	(47,612)	(47,472)	(2,891)	21,477
Net sales	131,476	99,953	100,922	84,265	98,280	78,944	85,771	76,470					416,616	339,465	362,387	347,580
(Loss) income before taxes	(6,450)	(9,053)	(7,612)	(24,054)	(7,878)	(10,509)	(10,792)	(6,680)					(47,169)	(35,859)	(12,593)	29,221
Impairment losses													0	0	(11,633)	0
Asset impairment charges	1	0	0	0	167	38	1,064	345					1	1,614	11,686	310
Goodwill	$ 29,835	$ 29,835	$ 29,835	$ 29,835	$ 29,835	$ 29,835	$ 29,835	29,835	$ 29,835	$ 29,835	$ 29,835	$ 29,835	$ 29,835	$ 29,835	$ 29,835	23,414	0
Ownership interest of nonconsolidated subsidiary															9.00%
Number of board member positions held | board_member															2
Number of board members | board_member	3												3		5
Restatement Adjustment
Error Corrections and Prior Period Adjustments Restatement [Line Items]
Reduction to stockholders' equity balances								19,467							$ 21,424	4,316	2,891
Net (loss) income								1,928							(17,169)	(2,249)
Net sales								14,656							(27,059)	(415)
(Loss) income before taxes								2,251							(26,483)	(5,318)
Cost of sales															6,500	7,900
Asset impairment charges								345							11,686	310
Goodwill								(11,631)							(11,631)	(132)
Revenue recognition adjustments | Restatement Adjustment
Error Corrections and Prior Period Adjustments Restatement [Line Items]
Net sales								14,656							(27,059)	(415)
(Loss) income before taxes								3,111							(9,215)	(2,700)
Gross basis | Restatement Adjustment
Error Corrections and Prior Period Adjustments Restatement [Line Items]
Net sales															6,500	7,900
Product development cost | Restatement Adjustment
Error Corrections and Prior Period Adjustments Restatement [Line Items]
Net sales								0							0
(Loss) income before taxes								123							(1,001)	(2,397)	(3,600)
Inventory valuation | Restatement Adjustment
Error Corrections and Prior Period Adjustments Restatement [Line Items]
Net sales								0							0
(Loss) income before taxes								(404)							(1,069)	38	$ (1,500)
Impairment of long-lived assets | Restatement Adjustment
Error Corrections and Prior Period Adjustments Restatement [Line Items]
Net sales								0							0
(Loss) income before taxes								(557)							(11,733)	(310)
Asset impairment charges															100	300
Product warranty | Restatement Adjustment
Error Corrections and Prior Period Adjustments Restatement [Line Items]
Net sales								0							0
(Loss) income before taxes								$ (319)							(2,484)	591
Purchase accounting | Restatement Adjustment
Error Corrections and Prior Period Adjustments Restatement [Line Items]
Net sales															0	0
(Loss) income before taxes															$ 0	(845)
Increase in long-lived assets																700
Goodwill																$ 700

Restatement of Previously Iss_4

Restatement of Previously Issued Consolidated Financial Statements - Effects of Restatement Adjustments on Net Sales and Income (Loss) Before Income Tax (Details) - USD ($)	3 Months Ended								12 Months Ended
	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Error Corrections and Prior Period Adjustments Restatement [Line Items]
Net Sales	$ 131,476,000	$ 99,953,000	$ 100,922,000	$ 84,265,000	$ 98,280,000	$ 78,944,000	$ 85,771,000	$ 76,470,000	$ 416,616,000	$ 339,465,000	$ 362,387,000	$ 347,580,000
Income (Loss) Before Income Taxes	$ (6,450,000)	$ (9,053,000)	$ (7,612,000)	$ (24,054,000)	$ (7,878,000)	$ (10,509,000)	$ (10,792,000)	(6,680,000)	$ (47,169,000)	$ (35,859,000)	(12,593,000)	29,221,000
Previously reported
Error Corrections and Prior Period Adjustments Restatement [Line Items]
Net Sales								61,814,000			389,446,000	347,995,000
Income (Loss) Before Income Taxes								(8,931,000)			13,890,000	34,539,000
Restatement adjustments
Error Corrections and Prior Period Adjustments Restatement [Line Items]
Net Sales								14,656,000			(27,059,000)	(415,000)
Income (Loss) Before Income Taxes								2,251,000			(26,483,000)	(5,318,000)
Restatement adjustments | Revenue recognition adjustments
Error Corrections and Prior Period Adjustments Restatement [Line Items]
Net Sales								14,656,000			(27,059,000)	(415,000)
Income (Loss) Before Income Taxes								3,111,000			(9,215,000)	(2,700,000)
Restatement adjustments | Product development cost
Error Corrections and Prior Period Adjustments Restatement [Line Items]
Net Sales								0			0
Income (Loss) Before Income Taxes								123,000			(1,001,000)	(2,397,000)	$ (3,600,000)
Restatement adjustments | Inventory valuation
Error Corrections and Prior Period Adjustments Restatement [Line Items]
Net Sales								0			0
Income (Loss) Before Income Taxes								(404,000)			(1,069,000)	38,000	(1,500,000)
Restatement adjustments | Impairment of long-lived assets
Error Corrections and Prior Period Adjustments Restatement [Line Items]
Net Sales								0			0
Income (Loss) Before Income Taxes								(557,000)			(11,733,000)	(310,000)
Restatement adjustments | Product warranty
Error Corrections and Prior Period Adjustments Restatement [Line Items]
Net Sales								0			0
Income (Loss) Before Income Taxes								(319,000)			(2,484,000)	591,000
Restatement adjustments | Accrued liabilities
Error Corrections and Prior Period Adjustments Restatement [Line Items]
Net Sales								0			0
Income (Loss) Before Income Taxes								422,000			(1,106,000)	591,000	300,000
Restatement adjustments | Purchase accounting
Error Corrections and Prior Period Adjustments Restatement [Line Items]
Net Sales											0	0
Income (Loss) Before Income Taxes											0	(845,000)
Restatement adjustments | Equity investment
Error Corrections and Prior Period Adjustments Restatement [Line Items]
Net Sales								0			0	0
Income (Loss) Before Income Taxes								$ (125,000)			$ 125,000	$ (286,000)	$ 300,000

Restatement of Previously Iss_5

Restatement of Previously Issued Consolidated Financial Statements - Consolidated Statements of Operations Impact (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended								6 Months Ended		9 Months Ended		12 Months Ended
	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Jun. 30, 2017	Jun. 30, 2016	Sep. 30, 2017	Sep. 30, 2016	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Error Corrections and Prior Period Adjustments Restatement [Line Items]
Net sales	$ 131,476	$ 99,953	$ 100,922	$ 84,265	$ 98,280	$ 78,944	$ 85,771	$ 76,470					$ 416,616	$ 339,465	$ 362,387	$ 347,580
Cost of sales	115,981	86,702	88,443	74,497	86,376	72,820	81,253	69,827					365,623	310,276	311,148	283,540
Gross profit	15,495	13,251	12,479	9,768	11,904	6,124	4,518	6,643					50,993	29,189	51,239	64,040
Operating expenses:
Research, development and engineering expenses	6,459	5,687	3,848	3,950	4,742	4,498	4,817	4,904					19,944	18,961	23,574	19,305
Selling, general and administrative expenses	11,297	12,062	10,688	10,209	8,563	6,855	6,699	6,405					44,256	28,522	28,837	23,142
Asset impairment charges	1	0	0	0	167	38	1,064	345					1	1,614	11,686	310
Amortization of intangible assets	1,210	1,210	1,209	1,209	1,430	1,429	1,429	1,428					4,838	5,716	4,582	1,013
Change in fair value of contingent consideration															(23)	(3,840)
Total operating expenses	18,967	18,959	15,745	15,368	14,902	12,820	13,726	13,082					69,039	54,530	68,656	39,930
Operating (loss) income	(3,472)	(5,708)	(3,266)	(5,600)	(2,998)	(6,696)	(9,208)	(6,439)					(18,046)	(25,341)	(17,417)	24,110
Other expense (income):
Interest expense	1,703	1,654	1,404	6,080	4,402	3,726	1,649	1,438					10,841	11,215	4,320	1,342
Contingent consideration															0	0
Gain from change in fair value of warrants	1,500	1,700	800	0	0	0	(157)	(1,256)					4,000	(1,413)	(9,300)	(6,170)
Loss on debt extinguishment and modifications	0	0	0	11,921	332	25	0	0					11,921	357	12	0
Other expense (income), net	(225)	(9)	2,142	453	146	62	92	59					2,361	359	144	(283)
Total other expense (income)	2,978	3,345	4,346	18,454	4,880	3,813	1,584	241					29,123	10,518	(4,824)	(5,111)
(Loss) income before income taxes	(6,450)	(9,053)	(7,612)	(24,054)	(7,878)	(10,509)	(10,792)	(6,680)					(47,169)	(35,859)	(12,593)	29,221
Income tax expense (benefit)	(320)	149	135	479	(1,238)	(1,792)	18,000	(3,357)					443	11,613	(9,702)	7,744
Net (loss) income	$ (6,130)	$ (9,202)	$ (7,747)	$ (24,533)	$ (6,640)	$ (8,717)	$ (28,792)	$ (3,323)	$ (32,280)	$ (32,115)	$ (41,482)	$ (40,832)	$ (47,612)	$ (47,472)	$ (2,891)	$ 21,477
Weighted-average common shares outstanding:
Basic (in shares)								10,819					13,787	10,931	10,808	10,705
Diluted (in shares)								10,819					13,787	10,931	10,991	11,131
(Loss) earnings per common share:
Basic (in dollars per share)								$ (0.42)					$ (6.20)	$ (4.34)	$ (0.27)	$ 2.01
Diluted (in dollars per share)								$ (0.42)					$ (6.20)	$ (4.47)	$ (1.11)	$ 1.38
Previously Reported
Error Corrections and Prior Period Adjustments Restatement [Line Items]
Net sales								$ 61,814							$ 389,446	$ 347,995
Cost of sales								57,758							326,612	280,950
Gross profit								4,056							62,834	67,045
Operating expenses:
Research, development and engineering expenses								5,250							21,681	16,900
Selling, general and administrative expenses								6,058							27,376	23,088
Asset impairment charges								0							0	0
Amortization of intangible assets								1,429							4,582	1,013
Change in fair value of contingent consideration															0	0
Total operating expenses								12,737							53,639	41,001
Operating (loss) income								(8,681)							9,195	26,044
Other expense (income):
Interest expense								1,421							4,327	1,331
Contingent consideration															48	(3,840)
Gain from change in fair value of warrants								(1,256)							(9,299)	(6,169)
Loss on debt extinguishment and modifications															0
Other expense (income), net								85							229	183
Total other expense (income)								250							(4,695)	(8,495)
(Loss) income before income taxes								(8,931)							13,890	34,539
Income tax expense (benefit)								(3,680)							(388)	10,813
Net (loss) income								$ (5,251)							$ 14,278	$ 23,726
Weighted-average common shares outstanding:
Basic (in shares)								10,819							10,808	10,707
Diluted (in shares)								10,819							11,074	11,132
(Loss) earnings per common share:
Basic (in dollars per share)								$ (0.49)							$ 1.32	$ 2.22
Diluted (in dollars per share)								$ (0.49)							$ 0.45	$ 2.13
Restatement Adjustments and Reclassifications
Error Corrections and Prior Period Adjustments Restatement [Line Items]
Net sales								$ 14,656							$ (27,059)	$ (415)
Cost of sales								12,069							(15,464)	2,590
Gross profit								2,587							(11,595)	(3,005)
Operating expenses:
Research, development and engineering expenses								(346)							1,893	2,405
Selling, general and administrative expenses								347							1,461	54
Asset impairment charges								345							11,686	310
Amortization of intangible assets								(1)							0	0
Change in fair value of contingent consideration															(23)	(3,840)
Total operating expenses								345							15,017	(1,071)
Operating (loss) income								2,242							(26,612)	(1,934)
Other expense (income):
Interest expense								17							(7)	11
Contingent consideration															(48)	3,840
Gain from change in fair value of warrants								0							(1)	(1)
Loss on debt extinguishment and modifications															12
Other expense (income), net								(26)							(85)	(466)
Total other expense (income)								(9)							(129)	3,384
(Loss) income before income taxes								2,251							(26,483)	(5,318)
Income tax expense (benefit)								323							(9,314)	(3,069)
Net (loss) income								$ 1,928							$ (17,169)	$ (2,249)
Weighted-average common shares outstanding:
Basic (in shares)								0							0	(2)
Diluted (in shares)								0							(83)	(1)
(Loss) earnings per common share:
Basic (in dollars per share)								$ 0.07							$ (1.59)	$ (0.21)
Diluted (in dollars per share)								$ 0.07							$ (1.56)	$ (0.75)

Restatement of Previously Iss_6

Restatement of Previously Issued Consolidated Financial Statements - Consolidated Balance Sheets Impact (Details) - USD ($) $ in Thousands	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Current assets:
Cash and cash equivalents	$ 0	$ 0	$ 0	$ 342	$ 2,292	$ 1,610	$ 435	$ 1,495	$ 8,445	$ 6,561	$ 6,306
Accounts receivable, net	68,660	60,811	56,673	64,305	60,336	53,364	57,884	45,384	70,532	76,266
Income tax receivable	1,018	841	1,996	6,829	7,127	5,737	3,384	1,723	5,265	0
Inventories, net	86,724	113,074	103,335	97,286	100,548	111,133	115,062	139,519	162,095	106,250
Prepaid expenses and other current assets	14,359	14,536	12,453	15,291	13,644	5,146	4,026	4,132	2,703	4,840
Deferred income taxes										8,552
Total current assets	170,761	189,262	174,457	184,053	183,947	176,990	180,791	192,253	249,040	202,469
Property, plant and equipment, net	18,960	18,974	19,050	19,230	20,127	20,257	20,386	20,662	22,809	17,954
Intangible assets, net	21,491	22,401	23,610	24,819	26,029	27,459	28,888	30,316	31,745	21,192
Goodwill	29,835	29,835	29,835	29,835	29,835	29,835	29,835	29,835	29,835	23,414	0
Deferred income taxes	0				0	0	0	19,285	17,657	13
Other noncurrent assets	5,972	6,035	4,518	5,053	4,681	2,821	2,621	2,664	2,751	1,903
TOTAL ASSETS	247,019	266,507	251,470	262,990	264,619	257,362	262,521	295,015	353,837	266,945
Current liabilities:
Accounts payable	51,225	54,195	55,610	67,167	53,588	45,764	49,729	43,160	79,823	67,713
Current maturities of long-term debt	0				750	375	0	0	0	1,667
Contingent consideration	12	20	29	30	26	88	100	5,481	8,275	0
Other accrued liabilities	38,362	41,393	35,379	35,234	32,507	22,405	19,182	17,929	17,846	18,182
Total current liabilities	126,654	136,940	116,281	119,318	99,645	85,626	83,049	66,570	105,944	87,562
Revolving line of credit	0				0	0	0	80,568	97,299	78,030
Deferred income taxes										0
Warrants	24,700	23,200	21,500	20,700	0	0	0	226	1,482	11,036
Long-term debt, less current maturities, net	54,439	54,305	54,168	54,045	110,392	111,517	110,929	53,799	53,805	2,361
Other noncurrent liabilities	8,351	13,312	12,438	13,328	13,458	12,730	12,833	11,952	10,434	1,473
TOTAL LIABILITIES	214,847	228,967	205,453	208,324	223,959	210,395	207,184	213,115	268,964	180,462
STOCKHOLDERS’ EQUITY
Preferred stock	0	0	0	0	0	0	0	0	0	0
Common stock	19	14	14	14	12	12	12	11	11	11
Additional paid-in capital	123,838	91,737	96,543	100,686	86,764	86,408	86,043	83,729	83,377	81,746
Retained earnings	(82,147)	(76,018)	(66,817)	(59,070)	(34,535)	(27,895)	(19,180)	9,612	12,937	15,828
Treasury stock, at cost	(9,538)	(9,604)	(11,530)	(11,582)	(11,581)	(11,558)	(11,537)	(11,452)	(11,452)	(11,102)
TOTAL STOCKHOLDERS’ EQUITY	32,172	6,129	18,210	30,048	40,660	46,967	55,337	81,900	84,873	86,483	47,607
TOTAL LIABILITIES AND STOCKHOLDERS’ EQUITY	$ 247,019	$ 266,507	$ 251,470	$ 262,990	$ 264,619	$ 257,362	$ 262,521	295,015	353,837	266,945
Previously Reported
Current assets:
Cash and cash equivalents								1,495	8,445	6,561
Accounts receivable, net								63,163	104,365	81,740
Income tax receivable								0	5,230
Inventories, net								120,735	130,347	93,903
Prepaid expenses and other current assets								9,496	4,288	4,801
Deferred income taxes										3,998
Total current assets								194,889	252,675	191,003
Property, plant and equipment, net								24,289	26,001	20,892
Intangible assets, net								30,316	31,745	21,392
Goodwill								41,466	41,466	23,546
Deferred income taxes								819	819	0
Other noncurrent assets								7,181	7,230	5,804
TOTAL ASSETS								298,960	359,936	262,637
Current liabilities:
Accounts payable								41,491	76,078	60,877
Current maturities of long-term debt										1,667
Contingent consideration								0	8,788
Other accrued liabilities								19,692	14,396	13,504
Total current liabilities								61,183	99,262	76,048
Revolving line of credit								80,568	97,299	78,030
Deferred income taxes										3,241
Warrants								226	1,482	11,036
Long-term debt, less current maturities, net								53,946	53,820	2,361
Other noncurrent liabilities								1,670	1,776	1,122
TOTAL LIABILITIES								197,593	253,639	171,838
STOCKHOLDERS’ EQUITY
Preferred stock								0	0	0
Common stock								12	12	12
Additional paid-in capital								75,500	75,179	73,959
Retained earnings								30,105	35,356	21,078
Treasury stock, at cost								(4,250)	(4,250)	(4,250)
TOTAL STOCKHOLDERS’ EQUITY								101,367	106,297	90,799	50,421
TOTAL LIABILITIES AND STOCKHOLDERS’ EQUITY								298,960	359,936	262,637
Restatement Adjustments and Reclassifications
Current assets:
Cash and cash equivalents								0	0	0
Accounts receivable, net								(17,779)	(33,833)	(5,474)
Income tax receivable								1,723	35
Inventories, net								18,784	31,748	12,347
Prepaid expenses and other current assets								(5,364)	(1,585)	39
Deferred income taxes										4,554
Total current assets								(2,636)	(3,635)	11,466
Property, plant and equipment, net								(3,627)	(3,192)	(2,938)
Intangible assets, net								0	0	(200)
Goodwill								(11,631)	(11,631)	(132)
Deferred income taxes								18,466	16,838	13
Other noncurrent assets								(4,517)	(4,479)	(3,901)
TOTAL ASSETS								(3,945)	(6,099)	4,308
Current liabilities:
Accounts payable								1,669	3,745	6,836
Current maturities of long-term debt										0
Contingent consideration								5,481	(513)
Other accrued liabilities								(1,763)	3,450	4,678
Total current liabilities								5,387	6,682	11,514
Revolving line of credit								0	0	0
Deferred income taxes										(3,241)
Warrants								0	0	0
Long-term debt, less current maturities, net								(147)	(15)	0
Other noncurrent liabilities								10,282	8,658	351
TOTAL LIABILITIES								15,522	15,325	8,624
STOCKHOLDERS’ EQUITY
Preferred stock								0	0	0
Common stock								(1)	(1)	(1)
Additional paid-in capital								8,229	8,198	7,787
Retained earnings								(20,493)	(22,419)	(5,250)
Treasury stock, at cost								(7,202)	(7,202)	(6,852)
TOTAL STOCKHOLDERS’ EQUITY								(19,467)	(21,424)	(4,316)	$ (2,891)
TOTAL LIABILITIES AND STOCKHOLDERS’ EQUITY								$ (3,945)	$ (6,099)	$ 4,308

Restatement of Previously Iss_7

Restatement of Previously Issued Consolidated Financial Statements - Consolidated Statements of Cash Flows Impact (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended		9 Months Ended		12 Months Ended
	Mar. 31, 2017	Mar. 31, 2016	Jun. 30, 2017	Jun. 30, 2016	Sep. 30, 2017	Sep. 30, 2016	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Error Corrections and Prior Period Adjustments Restatement [Line Items]
Net cash used in operating activities	$ 8,097	$ 13,910	$ 1,322	$ 24,511	$ (13,542)	$ 24,313	$ (7,695)	$ 32,282	$ (22,815)	$ (15,094)
Net cash used in investing activities	(1,896)	(1,099)	(2,424)	489	(3,611)	(1,065)	(5,165)	(1,651)	(43,805)	(52,322)
Net cash provided by financing activities	(8,151)	(19,761)	(1,190)	(33,010)	14,861	(30,083)	10,568	(36,784)	68,504	67,671
Increase in cash	(1,950)	(6,950)	(2,292)	(8,010)	(2,292)	(6,835)	(2,292)	(6,153)	1,884	255
Cash at beginning of the year	2,292	8,445	2,292	8,445	2,292	8,445	$ 2,292	8,445	6,561	6,306
Cash at end of the year	$ 342	1,495	$ 0	435	$ 0	1,610		2,292	8,445	6,561
Previously Reported
Error Corrections and Prior Period Adjustments Restatement [Line Items]
Net cash used in operating activities		9,995							(23,049)	(15,685)
Net cash used in investing activities		(214)							(43,570)	(51,713)
Net cash provided by financing activities		(16,731)							68,503	67,653
Increase in cash									1,884	255
Cash at beginning of the year		8,445		$ 8,445		$ 8,445		$ 8,445	6,561	6,306
Cash at end of the year		$ 1,495							$ 8,445	$ 6,561

Restatement of Previously Iss_8

Restatement of Previously Issued Consolidated Financial Statements - Pre-2014 Restatement Adjustments (Details) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Error Corrections and Prior Period Adjustments Restatement [Line Items]
(Loss) income before taxes	$ (6,450)	$ (9,053)	$ (7,612)	$ (24,054)	$ (7,878)	$ (10,509)	$ (10,792)	$ (6,680)	$ (47,169)	$ (35,859)	$ (12,593)	$ 29,221
Stockholders' equity	32,172	$ 6,129	$ 18,210	$ 30,048	40,660	$ 46,967	$ 55,337	81,900	32,172	40,660	84,873	86,483	$ 47,607
Common stock
Error Corrections and Prior Period Adjustments Restatement [Line Items]
Stockholders' equity	19				12				19	12	11	11	11
Additional paid-in capital
Error Corrections and Prior Period Adjustments Restatement [Line Items]
Stockholders' equity	123,838				86,764				123,838	86,764	83,377	81,746	61,930
Accumulated deficit
Error Corrections and Prior Period Adjustments Restatement [Line Items]
Stockholders' equity	(82,147)				(34,535)				(82,147)	(34,535)	12,937	15,828	(5,649)
Treasury stock, at cost
Error Corrections and Prior Period Adjustments Restatement [Line Items]
Stockholders' equity	$ (9,538)				$ (11,581)				$ (9,538)	$ (11,581)	(11,452)	(11,102)	(8,685)
Previously Reported
Error Corrections and Prior Period Adjustments Restatement [Line Items]
(Loss) income before taxes								(8,931)			13,890	34,539
Stockholders' equity								101,367			106,297	90,799	50,421
Previously Reported | Common stock
Error Corrections and Prior Period Adjustments Restatement [Line Items]
Stockholders' equity													11
Previously Reported | Additional paid-in capital
Error Corrections and Prior Period Adjustments Restatement [Line Items]
Stockholders' equity													57,308
Previously Reported | Accumulated deficit
Error Corrections and Prior Period Adjustments Restatement [Line Items]
Stockholders' equity													(2,648)
Previously Reported | Treasury stock, at cost
Error Corrections and Prior Period Adjustments Restatement [Line Items]
Stockholders' equity													(4,250)
Restatement Adjustments and Reclassifications
Error Corrections and Prior Period Adjustments Restatement [Line Items]
(Loss) income before taxes								2,251			(26,483)	(5,318)
Stockholders' equity								(19,467)			(21,424)	(4,316)	(2,891)
Restatement Adjustments and Reclassifications | Common stock
Error Corrections and Prior Period Adjustments Restatement [Line Items]
Stockholders' equity													0
Restatement Adjustments and Reclassifications | Additional paid-in capital
Error Corrections and Prior Period Adjustments Restatement [Line Items]
Stockholders' equity													4,622
Restatement Adjustments and Reclassifications | Accumulated deficit
Error Corrections and Prior Period Adjustments Restatement [Line Items]
Stockholders' equity													(3,079)
Restatement Adjustments and Reclassifications | Treasury stock, at cost
Error Corrections and Prior Period Adjustments Restatement [Line Items]
Stockholders' equity													(4,435)
Product development cost | Restatement Adjustments and Reclassifications
Error Corrections and Prior Period Adjustments Restatement [Line Items]
(Loss) income before taxes								123			(1,001)	(2,397)	(3,600)
Inventory valuation | Restatement Adjustments and Reclassifications
Error Corrections and Prior Period Adjustments Restatement [Line Items]
(Loss) income before taxes								(404)			(1,069)	38	(1,500)
Accrued liabilities | Restatement Adjustments and Reclassifications
Error Corrections and Prior Period Adjustments Restatement [Line Items]
(Loss) income before taxes								422			(1,106)	591	300
Equity investment | Restatement Adjustments and Reclassifications
Error Corrections and Prior Period Adjustments Restatement [Line Items]
(Loss) income before taxes								$ (125)			$ 125	$ (286)	$ 300

Weichai Transactions - Weichai

Weichai Transactions - Weichai Transaction (Details) - Share Purchase Agreement, Weichai Transaction	Mar. 31, 2017USD ($)shares	Aug. 31, 2017shares	Mar. 31, 2017USD ($)shares	Dec. 31, 2017shares
Subsidiary, Sale of Stock [Line Items]
Consideration received on transaction | $	$ 60,000,000		$ 60,000,000
Common Stock
Subsidiary, Sale of Stock [Line Items]
Number of shares issued in transaction (in shares)			2,728,752	2,729,000
Common Stock | Chief Strategy Officer
Subsidiary, Sale of Stock [Line Items]
Number of shares issued in transaction (in shares)		200,000
Redeemable Convertible Series B Preferred Stock
Subsidiary, Sale of Stock [Line Items]
Number of shares issued in transaction (in shares)	2,385,624
Debt instrument, convertible, conversion ratio			2
Issuance of redeemable convertible Series B Preferred Stock, net of fees (in shares)	4,771,248			4,771,000
Power Solutions International, Inc. | Weichai | Common Stock
Subsidiary, Sale of Stock [Line Items]
Percentage of ownership after transaction			51.00%

Weichai Transactions - Series B

Weichai Transactions - Series B Redeemable Convertible Preferred Stock (Details) - Share Purchase Agreement, Weichai Transaction - USD ($) $ / shares in Units, $ in Millions	Oct. 30, 2017	Sep. 30, 2017	Mar. 31, 2017	Dec. 31, 2017
Class of Stock [Line Items]
Preferred stock, dividend rate, percentage		10.00%
Redeemable Convertible Series B Preferred Stock
Class of Stock [Line Items]
Exercise price of warrants or rights (in dollars per share)				$ 16
Beneficial conversion feature	$ 23.1
Number of shares issued in transaction (in shares)			2,385,624
Issuance of redeemable convertible Series B Preferred Stock, net of fees (in shares)			4,771,248	4,771,000

Weichai Transactions - Weicha_2

Weichai Transactions - Weichai Warrant (Details) - USD ($)	May 03, 2019	Apr. 23, 2019	Apr. 01, 2019	Oct. 01, 2018	Sep. 30, 2018	Dec. 31, 2018	Dec. 31, 2016
Share Purchase Agreement, Weichai Transaction
Class of Warrant or Right [Line Items]
EBITDA, minimum							$ 22,000,000
Net book value per share, minimum (in dollars per share)							$ 8
Aggregate amount							$ 15,000,000
Share Purchase Agreement, Weichai Transaction | Subsequent Event
Class of Warrant or Right [Line Items]
Volume weighted average share price percentage					50.00%	85.00%
Trading period						20 days
Exercisable (term)						90 days
Share Purchase Agreement, Second Amended And Restated Warrant | Subsequent Event
Class of Warrant or Right [Line Items]
Volume weighted average share price percentage				50.00%	50.00%
Trading period				20 days	20 days
Exercisable (term)					90 days
Share Purchase Agreement, Second Amended And Restated Warrant | Subsequent Event | Maximum
Class of Warrant or Right [Line Items]
Reduction of exercise price				$ 15,000,000
Series B | Share Purchase Agreement, Second Amended And Restated Warrant | Subsequent Event
Class of Warrant or Right [Line Items]
Percent ownership of outstanding common stock	51.50%		51.00%
Exercise proceeds for the warrants		$ 1,600,000
Exercise of private placement warrants (in shares)		4,049,759

Weichai Transactions - Valuatio

Weichai Transactions - Valuation and Accounting for Issuance and Conversion of Common Stock, Preferred Stock (and Related Beneficial Conversion Feature) and Warrants (Details) - USD ($)	Oct. 30, 2017	Mar. 31, 2017	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Subsidiary, Sale of Stock [Line Items]
Loss (gain) from change in fair value of warrants			$ 1,500,000	$ 1,700,000	$ 800,000	$ 0	$ 0	$ 0	$ (157,000)	$ (1,256,000)	$ 4,000,000	$ (1,413,000)	$ (9,300,000)	$ (6,170,000)
Carrying value of the common stock and series b preferred stock			39,300,000								39,300,000
Aggregate remaining proceeds											38,700,000
Proceeds allocated based on related fair value, net of transaction costs											24,600,000
Transaction costs											(400,000)
Deemed dividend recorded in additional paid in capital											37,800,000
Carrying value of preferred stock		$ 24,617,000	62,900,000	$ 31,411,000	$ 27,807,000	24,617,000					62,900,000
Par value (in dollars per share)			0.001								0.001
Conversion price (in dollars per share)	$ 4.85
Share Purchase Agreement, Weichai Transaction
Subsidiary, Sale of Stock [Line Items]
Weichai warrant liability		$ 20,700,000				$ 20,700,000
Warrant, current			$ 24,700,000								24,700,000
Redeemable Convertible Series B Preferred Stock
Subsidiary, Sale of Stock [Line Items]
Proceeds allocated to Series B Preferred Stock											25,000,000
Fully accreted discount											$ 14,100,000
Redeemable Convertible Series B Preferred Stock | Share Purchase Agreement, Weichai Transaction
Subsidiary, Sale of Stock [Line Items]
Beneficial conversion feature	$ 23,100,000
Issuance of redeemable convertible Series B Preferred Stock, net of fees (in shares)		4,771,248									4,771,000
Common stock
Subsidiary, Sale of Stock [Line Items]
Proceeds allocated to common stock											$ 14,300,000

Weichai Transactions - Weicha_3

Weichai Transactions - Weichai Collaboration Arrangement (Details)	Mar. 20, 2017
Equity [Abstract]
Term of collaborative arrangement	3 years

Property, Plant and Equipment_3

Property, Plant and Equipment and Leases - Property, Plant and Equipment (Details) - USD ($) $ in Thousands	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Property, Plant and Equipment [Line Items]
Total property, plant and equipment, at cost	$ 35,735				$ 32,773				$ 34,170	$ 26,130
Accumulated depreciation	(16,775)				(12,646)				(11,361)	(8,176)
Property, plant and equipment, net	18,960	$ 18,974	$ 19,050	$ 19,230	20,127	$ 20,257	$ 20,386	$ 20,662	22,809	17,954
Land
Property, Plant and Equipment [Line Items]
Total property, plant and equipment, at cost	0				0				260	260
Buildings
Property, Plant and Equipment [Line Items]
Total property, plant and equipment, at cost	0				0				1,471	1,471
Leasehold improvements
Property, Plant and Equipment [Line Items]
Total property, plant and equipment, at cost	6,320				6,199				6,450	3,333
Machinery and equipment
Property, Plant and Equipment [Line Items]
Total property, plant and equipment, at cost	27,379				24,490				23,523	17,500
Construction in progress
Property, Plant and Equipment [Line Items]
Total property, plant and equipment, at cost	$ 2,036				$ 2,084				$ 2,466	$ 3,566

Property, Plant and Equipment_4

Property, Plant and Equipment and Leases - Narrative (Details) $ in Millions	1 Months Ended		12 Months Ended
	Dec. 31, 2018USD ($)	Jul. 31, 2018USD ($)industrial_building	Dec. 31, 2017USD ($)	Dec. 31, 2016USD ($)	Dec. 31, 2015USD ($)	Dec. 31, 2014USD ($)
Property, Plant and Equipment [Line Items]
Noncash conversion of inventory				$ 1.1
Rent expense under operating leases			$ 4.7	$ 5.2	$ 4.9	$ 3.6
Capital lease obligation			$ 0.4
Subsequent Event
Property, Plant and Equipment [Line Items]
Number of industrial buildings | industrial_building		2
Base rental payments	$ 4.2	$ 9.4

Property, Plant and Equipment_5

Property, Plant and Equipment and Leases - Schedule of Future Minimum Lease Payments (Details) $ in Thousands	Dec. 31, 2017USD ($)
Operating
2018	$ 4,341
2019	4,136
2020	3,786
2021	3,482
2022	3,578
2023 and beyond	3,202
Total	22,525
Capital
2018	22
2019	21
2020	20
2021	20
2022	19
2023 and beyond	51
Total	$ 153

Acquisitions - Narrative (Detai

Acquisitions - Narrative (Details) - USD ($)	1 Months Ended				3 Months Ended									12 Months Ended
	Jun. 30, 2017	May 31, 2015	Mar. 31, 2015	Apr. 30, 2014	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Mar. 31, 2014	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014	Apr. 29, 2015	Apr. 01, 2014	Dec. 31, 2013
Business Acquisition [Line Items]
Initial cash paid at date of acquisition, net of acquired cash														$ 0	$ 0	$ 34,227,000	$ 44,122,000
Contingent consideration					$ 12,000				$ 38,000					12,000	38,000	8,717,000	0			$ 0
Warranty accrual adjustment														0	0	963,000	1,600,000
Acquisition consideration, net of tax														(712,000)			4,379,000
Other expense (income), net					(225,000)	$ (9,000)	$ 2,142,000	$ 453,000	146,000	$ 62,000	$ 92,000	$ 59,000		2,361,000	359,000	144,000	(283,000)
Deferred income taxes	$ 1,066,000				703,000	1,210,000	1,066,000	933,000	464,000	522,000	372,000	0		703,000	464,000	0
Goodwill	29,835,000				29,835,000	29,835,000	29,835,000	29,835,000	29,835,000	29,835,000	29,835,000	29,835,000		29,835,000	29,835,000	29,835,000	23,414,000			$ 0
Amortization of intangible assets					1,210,000	1,210,000	1,209,000	1,209,000	1,430,000	1,429,000	1,429,000	1,428,000		4,838,000	5,716,000	4,582,000	1,013,000
Income tax (benefit) provision					320,000	$ (149,000)	(135,000)	$ (479,000)	$ 1,238,000	$ 1,792,000	$ (18,000,000)	3,357,000		(443,000)	(11,613,000)	9,702,000	(7,744,000)
Total transaction costs incurred related to acquisition activities																1,100,000	800,000
Increase (decrease) in value reflected in income														0	$ (230,000)	(23,000)	(3,840,000)
Settled Litigation | Carl Trent, Kenneth Trent, and CKT Holdings, Inc. vs. 3PI and PSI
Business Acquisition [Line Items]
Legal settlement	$ 3,000,000
Restatement adjustments
Business Acquisition [Line Items]
Other expense (income), net												(26,000)				(85,000)	(466,000)
Goodwill												(11,631,000)				(11,631,000)	(132,000)
Amortization of intangible assets												(1,000)				0	0
Income tax (benefit) provision												$ (323,000)				9,314,000	3,069,000
Term Loan | Wells Fargo Credit Agreement
Business Acquisition [Line Items]
Debt instrument, face amount																		$ 3,500,000	$ 5,000,000
Powertrain
Business Acquisition [Line Items]
Cash purchase price		$ 20,873,000
Working capital adjustment		(97,000)
Initial cash paid at date of acquisition, net of acquired cash		$ 20,800,000
Debt instrument, interest rate		5.00%
Fair value of contingent consideration		$ 8,200,000
Purchase price		28,976,000
Warranty accrual adjustment																$ 300,000
Weighted average useful life																11 years 6 months
Goodwill																$ 15,311,000
Intangible assets acquired																$ 13,600,000
Powertrain | Customer relationships
Business Acquisition [Line Items]
Weighted average useful life																12 years
Intangible assets acquired																$ 13,000,000
Powertrain | Maximum
Business Acquisition [Line Items]
Contingent consideration		8,000,000
Bi-Phase
Business Acquisition [Line Items]
Cash purchase price		3,619,000
Working capital adjustment		266,000
Initial cash paid at date of acquisition, net of acquired cash		3,900,000
Fair value of contingent consideration		540,000
Purchase price		$ 4,425,000
Weighted average useful life																8 years 6 months
Goodwill																$ 1,217,000
Intangible assets acquired																$ 860,000
Bi-Phase | Customer relationships
Business Acquisition [Line Items]
Weighted average useful life																15 years
Intangible assets acquired																$ 160,000
Bi-Phase | Minimum
Business Acquisition [Line Items]
Contingent consideration, earn-out period		3 years
Bi-Phase | Maximum
Business Acquisition [Line Items]
Contingent consideration, earn-out period		5 years
Buck's
Business Acquisition [Line Items]
Cash purchase price			$ 9,735,000
Inventory step-up			300,000
Goodwill			$ 1,526,000
Buck's | Customer relationships
Business Acquisition [Line Items]
Weighted average useful life																10 years
Intangible assets acquired																$ 1,380,000
3PI
Business Acquisition [Line Items]
Cash purchase price				$ 45,400,000
Initial cash paid at date of acquisition, net of acquired cash				44,122,000
Contingent consideration																	3,800,000
Fair value of contingent consideration				3,840,000
Purchase price				53,022,000
Weighted average useful life																12 years 5 months 8 days
Inventory step-up				400,000
Cash acquired				$ 1,300,000
Contingent consideration (in shares)				65,772
Fair value of contingent consideration				$ 8,900,000
Acquisition consideration, net of tax							$ 700,000										4,400,000
Deferred income taxes																	1,500,000
Goodwill				$ 23,414,000	$ 14,500,000									$ 14,500,000
Goodwill expected to be deductible for income tax purposes																	19,700,000
Intangible assets acquired																	23,300,000
Amortization of intangible assets																	800,000
Acquisition-related interest expense													$ 200,000
Income tax (benefit) provision																	400,000
Increase (decrease) in value reflected in income																	3,800,000
3PI | Acquisition-related Costs
Business Acquisition [Line Items]
Non-recurring transaction related expenses																	3,500,000
3PI | Restatement adjustments
Business Acquisition [Line Items]
Other expense (income), net																	$ (3,800,000)
3PI | Customer relationships
Business Acquisition [Line Items]
Weighted average useful life																	13 years
Intangible assets acquired																	$ 20,400,000
3PI | Tradenames and trademarks
Business Acquisition [Line Items]
Weighted average useful life																	13 years
Intangible assets acquired																	$ 1,700,000
3PI | Maximum
Business Acquisition [Line Items]
Contingent consideration (in shares)				131,544

Acquisitions - Schedule of Reco

Acquisitions - Schedule of Recognized Identified Assets Acquired and Liabilities Assumed (Details) - USD ($) $ in Thousands	1 Months Ended			12 Months Ended
	May 31, 2015	Mar. 31, 2015	Apr. 30, 2014	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2013
Purchase consideration:
Initial cash paid at date of acquisition, net of acquired cash				$ 0	$ 0	$ 34,227	$ 44,122
Allocation of consideration to assets acquired and liabilities assumed:
Goodwill				29,835	$ 29,835	29,835	$ 23,414	$ 29,835	$ 29,835	$ 29,835	$ 29,835	$ 29,835	$ 29,835	$ 0
Powertrain
Purchase consideration:
Initial cash paid at date of acquisition	$ 20,873
Initial cash paid at date of acquisition, net of acquired cash	20,800
Fair value of contingent consideration	8,200
Working capital adjustment	(97)
Total purchase consideration	28,976
Allocation of consideration to assets acquired and liabilities assumed:
Accounts receivable						4,931
Inventories						1,890
Prepaid expenses and other current assets						23
Property, plant and equipment						314
Intangible assets						13,600
Goodwill						15,311
Other non-current assets						24
Current liabilities						(7,117)
Net assets acquired						28,976
Bi-Phase
Purchase consideration:
Initial cash paid at date of acquisition	3,619
Initial cash paid at date of acquisition, net of acquired cash	3,900
Fair value of contingent consideration	540
Working capital adjustment	266
Total purchase consideration	$ 4,425
Allocation of consideration to assets acquired and liabilities assumed:
Accounts receivable						212
Inventories						2,103
Prepaid expenses and other current assets						166
Property, plant and equipment						113
Intangible assets						860
Goodwill						1,217
Current liabilities						(246)
Net assets acquired						$ 4,425
Buck's
Purchase consideration:
Initial cash paid at date of acquisition		$ 9,735
Allocation of consideration to assets acquired and liabilities assumed:
Inventories		6,598
Property, plant and equipment		231
Goodwill		1,526
Net assets acquired		9,735
Buck's | Customer relationships
Allocation of consideration to assets acquired and liabilities assumed:
Intangible assets		$ 1,380
3PI
Purchase consideration:
Initial cash paid at date of acquisition			$ 45,400
Initial cash paid at date of acquisition, net of acquired cash			44,122
Fair value of contingent consideration			3,840
Fair value of the fixed number of shares of Common Stock			5,060
Total purchase consideration			53,022
Allocation of consideration to assets acquired and liabilities assumed:
Accounts receivable			3,989
Inventories			4,953
Prepaid expenses and other current assets			243
Property, plant and equipment			2,346
Intangible assets			23,300
Goodwill			23,414	$ 14,500
Current liabilities			(5,223)
Net assets acquired			$ 53,022

Acquisitions - Summary of Ident

Acquisitions - Summary of Identifiable Intangible Assets (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014
Powertrain
Acquired Finite-Lived Intangible Assets [Line Items]
Asset Amount	$ 13,600
Estimated life	11 years 6 months
Powertrain | Backlog
Acquired Finite-Lived Intangible Assets [Line Items]
Asset Amount	$ 600
Estimated life	3 months
Powertrain | Customer relationships
Acquired Finite-Lived Intangible Assets [Line Items]
Asset Amount	$ 13,000
Estimated life	12 years
Bi-Phase
Acquired Finite-Lived Intangible Assets [Line Items]
Asset Amount	$ 860
Estimated life	8 years 6 months
Bi-Phase | Developed technology
Acquired Finite-Lived Intangible Assets [Line Items]
Asset Amount	$ 700
Estimated life	7 years
Bi-Phase | Customer relationships
Acquired Finite-Lived Intangible Assets [Line Items]
Asset Amount	$ 160
Estimated life	15 years
Buck's | Customer relationships
Acquired Finite-Lived Intangible Assets [Line Items]
Asset Amount	$ 1,380
Estimated life	10 years
3PI
Acquired Finite-Lived Intangible Assets [Line Items]
Asset Amount		$ 23,300
Estimated life	12 years 5 months 8 days
3PI | Backlog
Acquired Finite-Lived Intangible Assets [Line Items]
Asset Amount		$ 1,200
Estimated life		15 months
3PI | Customer relationships
Acquired Finite-Lived Intangible Assets [Line Items]
Asset Amount		$ 20,400
Estimated life		13 years
3PI | Tradenames and trademarks
Acquired Finite-Lived Intangible Assets [Line Items]
Asset Amount		$ 1,700
Estimated life		13 years

Acquisitions - Business Acquisi

Acquisitions - Business Acquisition, Pro Forma Information (Details) - 3PI - USD ($) $ / shares in Units, $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014
Business Acquisition [Line Items]
Net sales	$ 383,455	$ 352,760
Net income	$ (580)	$ 21,696
Earnings per share, basic (in dollars per share)	$ (0.05)	$ 2.03
Earnings per share, diluted (in dollars per share)	$ (0.05)	$ 1.95

Goodwill and Other Intangible_2

Goodwill and Other Intangibles - Schedule of Goodwill (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Goodwill
Balance at beginning of year, net	$ 29,835	$ 29,835	$ 23,414	$ 0
Acquisitions	0	0	18,054	23,414
Impairment losses	0	0	(11,633)	0
Balance at end of year, net	$ 29,835	29,835	29,835	23,414
Accumulated impairment losses		$ (11,633)	$ (11,633)	$ 0	$ 0

Goodwill and Other Intangible_3

Goodwill and Other Intangibles - Schedule of Finite-Lived Intangible Assets (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Finite-Lived Intangible Assets [Line Items]
Gross Carrying Value	$ 37,640	$ 37,340	$ 39,140	$ 23,300
Accumulated Amortization	(16,149)	(11,311)	(7,395)	(2,108)
Net Book Value	$ 21,491	$ 26,029	31,745	$ 21,192
Backlog
Finite-Lived Intangible Assets [Line Items]
Weighted-Average Useful Life (in years)				1 year
Gross Carrying Value			1,800	$ 1,200
Accumulated Amortization			(1,800)	(1,095)
Net Book Value			$ 0	$ 105
Customer relationships
Finite-Lived Intangible Assets [Line Items]
Weighted-Average Useful Life (in years)	10 years 18 days	10 years 9 months 7 days	11 years 6 months 11 days	21 years
Gross Carrying Value	$ 34,940	$ 34,940	$ 34,940	$ 20,400
Accumulated Amortization	(14,915)	(10,430)	(5,129)	(926)
Net Book Value	$ 20,025	$ 24,510	$ 29,811	$ 19,474
Developed technology
Finite-Lived Intangible Assets [Line Items]
Weighted-Average Useful Life (in years)	4 years 2 months 23 days	8 years 3 months 11 days	8 years 2 months 12 days
Gross Carrying Value	$ 1,000	$ 700	$ 700
Accumulated Amortization	(434)	(287)	(113)
Net Book Value	$ 566	$ 413	$ 587
Trade names and trademarks
Finite-Lived Intangible Assets [Line Items]
Weighted-Average Useful Life (in years)	6 years 22 days	6 years 9 months 14 days	7 years 6 months 18 days	8 years 3 months 11 days
Gross Carrying Value	$ 1,700	$ 1,700	$ 1,700	$ 1,700
Accumulated Amortization	(800)	(594)	(353)	(87)
Net Book Value	$ 900	$ 1,106	$ 1,347	$ 1,613

Goodwill and Other Intangible_4

Goodwill and Other Intangibles - Summary of Amortization Expense (Details) - USD ($) $ in Thousands	3 Months Ended								6 Months Ended		9 Months Ended		12 Months Ended
	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Jun. 30, 2017	Jun. 30, 2016	Sep. 30, 2017	Sep. 30, 2016	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Goodwill and Intangible Assets Disclosure [Abstract]
Cost of sales													$ 0	$ 0	$ 705	$ 1,095
Operating expenses	$ 1,210	$ 1,210	$ 1,209	$ 1,209	$ 1,430	$ 1,429	$ 1,429	$ 1,428					4,838	5,716	4,582	1,013
Total				$ 1,209				$ 1,429	$ 2,419	$ 2,857	$ 3,628	$ 4,286	$ 4,838	$ 5,716	$ 5,287	$ 2,108

Goodwill and Other Intangible_5

Goodwill and Other Intangibles - Schedule of Future Amortization Expense (Details) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Year Ending December 31,
2018	$ 4,227
2019	3,698
2020	3,113
2021	2,594
2022	2,184
2023 and beyond	5,675
Net Book Value	$ 21,491	$ 26,029	$ 31,745	$ 21,192

Debt - Schedule of Debt (Detail

Debt - Schedule of Debt (Details) - USD ($) $ in Thousands	Dec. 31, 2017	Mar. 31, 2017	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Schedule Of Long Term Debt And Short Term Debt Instruments [Line Items]
Total Short-Term Debt	$ 37,055		$ 13,524	$ 0	$ 1,667
Long-Term Debt	55,000
Less Unamortized Debt Issuance Costs	(561)		(15,258)	(1,195)	0
Total Long-Term Debt	54,439		110,392	151,104	80,391
Debt issuance costs	900		17,200	1,500	200
Term Loan
Schedule Of Long Term Debt And Short Term Debt Instruments [Line Items]
Long-Term Debt	0		0	0	2,361
Term Loan | TPG Term Loan
Schedule Of Long Term Debt And Short Term Debt Instruments [Line Items]
Long-Term Debt	0		70,650	0	0
Debt issuance costs	400	$ 400	400
Wells Fargo Revolving Credit Facility
Schedule Of Long Term Debt And Short Term Debt Instruments [Line Items]
Long-Term Debt	0		0	97,299	78,030
Unsecured Senior Notes
Schedule Of Long Term Debt And Short Term Debt Instruments [Line Items]
Long-Term Debt	55,000		55,000	55,000	0
Term Loan | Wells Fargo Credit Agreement
Schedule Of Long Term Debt And Short Term Debt Instruments [Line Items]
Total Short-Term Debt	0		0	0	1,667
Term Loan | TPG Term Loan
Schedule Of Long Term Debt And Short Term Debt Instruments [Line Items]
Total Short-Term Debt	0		750	0	0
Wells Fargo Revolving Credit Facility
Schedule Of Long Term Debt And Short Term Debt Instruments [Line Items]
Total Short-Term Debt	$ 37,055		$ 12,774	$ 0	$ 0

Debt - Debt Narrative (Details)

Debt - Debt Narrative (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014	Oct. 01, 2018	Sep. 30, 2018
Debt Instrument [Line Items]
Interest paid	$ 7.8	$ 6.7	$ 3.3	$ 1.1
Revolving Credit Facility and Senior Notes
Debt Instrument [Line Items]
Debt instrument, interest rate	7.50%
Wells Fargo Revolving Credit Facility
Debt Instrument [Line Items]
Maturity period prior to the final maturity of unsecured senior notes	60 days
Subsequent Event | Revolving Credit Facility and Senior Notes
Debt Instrument [Line Items]
Debt instrument, interest rate					8.50%	6.50%
Subsequent Event | Wells Fargo Revolving Credit Facility
Debt Instrument [Line Items]
Debt instrument, interest rate						1.00%

Debt - Schedule of Maturities o

Debt - Schedule of Maturities of Long-Term Debt (Details) $ in Thousands	Dec. 31, 2017USD ($)
Debt Disclosure [Abstract]
2018	$ 0
2019	0
2020	55,000
Total Long-Term Debt	$ 55,000

Debt - Wells Fargo Credit Agree

Debt - Wells Fargo Credit Agreement - Narrative (Details)	Jun. 28, 2016USD ($)	Apr. 29, 2015USD ($)	Apr. 01, 2014USD ($)	Jun. 28, 2013USD ($)	Dec. 31, 2017USD ($)	Oct. 03, 2017USD ($)	Jul. 17, 2017USD ($)	Mar. 31, 2017USD ($)	Dec. 31, 2016USD ($)	Dec. 19, 2016USD ($)	Dec. 31, 2015USD ($)	Feb. 11, 2015USD ($)	Dec. 31, 2014USD ($)	Sep. 30, 2014USD ($)
Line of Credit Facility [Line Items]
Debt issuance costs					$ 900,000				$ 17,200,000		$ 1,500,000		$ 200,000
Wells Fargo Credit Agreement
Line of Credit Facility [Line Items]
Lender fees	$ 200,000							$ 700,000		$ 100,000
Wells Fargo Credit Agreement | Term Loan
Line of Credit Facility [Line Items]
Interest rate, effective percentage		4.67%
Debt instrument, face amount		$ 3,500,000	$ 5,000,000
Wells Fargo Credit Agreement | LIBOR | Term Loan
Line of Credit Facility [Line Items]
Basis spread on variable rate		4.50%	4.50%
Wells Fargo Credit Agreement | Revolving Credit Facility
Line of Credit Facility [Line Items]
Maximum borrowing capacity	$ 75,000,000		$ 90,000,000	$ 75,000,000		$ 58,750,000	$ 52,500,000	$ 65,000,000				$ 125,000,000		$ 100,000,000
Line of credit facility, increase limit				$ 100,000,000			$ 12,500,000
Unused line fee percentage				0.25%
Debt covenant, fixed charge coverage ratio, minimum			1.2	1
Debt covenant, threshold to report fixed charge coverage ratio, availability amount				$ 9,375,000
Debt covenant, threshold to report fixed charge coverage ratio, percentage of maximum borrowing capacity				12.50%
Debt issuance costs					100,000				100,000
Lender fees					$ 700,000				$ 300,000				$ 100,000
Wells Fargo Credit Agreement | Revolving Credit Facility | Minimum
Line of Credit Facility [Line Items]
Line of credit facility, increase limit						$ 6,250,000
Wells Fargo Credit Agreement | Revolving Credit Facility | Minimum | Prime Rate
Line of Credit Facility [Line Items]
Basis spread on variable rate				0.00%
Wells Fargo Credit Agreement | Revolving Credit Facility | Minimum | LIBOR
Line of Credit Facility [Line Items]
Basis spread on variable rate	1.75%			1.50%
Wells Fargo Credit Agreement | Revolving Credit Facility | Maximum | Prime Rate
Line of Credit Facility [Line Items]
Basis spread on variable rate				0.50%
Wells Fargo Credit Agreement | Revolving Credit Facility | Maximum | LIBOR
Line of Credit Facility [Line Items]
Basis spread on variable rate	2.25%			2.00%

Debt - Schedule of Amounts Borr

Debt - Schedule of Amounts Borrowed Under Wells Fargo Revolving Credit Agreement (Details) - Wells Fargo Credit Agreement - Wells Fargo Revolving Credit Facility - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014	Mar. 31, 2017
Line of Credit Facility [Line Items]
Average borrowings under Wells Fargo Revolving Credit Facility	$ 26,662	$ 44,335	$ 96,390	$ 53,250
Average Interest Cost on Wells Fargo Revolving Credit Facility	6.85%	2.75%	1.96%	2.36%
Accrued and unpaid interest	$ 90	$ 24	$ 86	$ 105
Available revolving line of credit balance	$ 13,000				$ 40,000
Prime Rate
Line of Credit Facility [Line Items]
Wells Fargo Prime Rate (Base Rate) loan interest rate	6.00%	4.25%	3.50%	3.25%
LIBOR
Line of Credit Facility [Line Items]
LIBOR loan interest rate	4.51%	2.71%	1.84%	1.66%

Debt - Wells Fargo Credit Agr_2

Debt - Wells Fargo Credit Agreement - Amendments (Details)

Mar. 29, 2018USD ($)

Jul. 17, 2017USD ($)

Mar. 31, 2017USD ($)

Jan. 27, 2017

Jun. 28, 2016USD ($)

Apr. 29, 2015USD ($)

Apr. 01, 2014USD ($)

Jun. 28, 2013USD ($)

Dec. 31, 2017USD ($)

Dec. 31, 2016USD ($)

Dec. 31, 2015USD ($)

Dec. 31, 2014USD ($)

Oct. 01, 2018USD ($)

Oct. 03, 2017USD ($)

Dec. 19, 2016USD ($)

Aug. 22, 2016USD ($)

Feb. 11, 2015USD ($)

Sep. 30, 2014USD ($)

Line of Credit Facility [Line Items]

Repayments of long-term debt

$ 71,400,000

$ 4,028,000

$ 972,000

Wells Fargo Credit Agreement

Line of Credit Facility [Line Items]

Lender fees

$ 700,000

$ 200,000

$ 100,000

Reserve against borrowing base availability

$ 12,500,000

$ 12,500,000

Reserve against borrowing base availability upon filing delinquent reports

$ 7,500,000

Wells Fargo Credit Agreement | Subsequent Event

Line of Credit Facility [Line Items]

Lender fees

$ 800,000

Wells Fargo Credit Agreement | Term Loan

Line of Credit Facility [Line Items]

Debt instrument, face amount

$ 3,500,000

$ 5,000,000

Debt instrument, term

36 months

Repayments of long-term debt

$ 5,000,000

Wells Fargo Credit Agreement | Term Loan | LIBOR

Line of Credit Facility [Line Items]

Basis spread on variable rate

4.50%

4.50%

Revolving Credit Facility | Wells Fargo Credit Agreement

Line of Credit Facility [Line Items]

Maximum borrowing capacity

$ 52,500,000

$ 65,000,000

$ 75,000,000

$ 90,000,000

$ 75,000,000

$ 58,750,000

$ 125,000,000

$ 100,000,000

Debt covenant, fixed charge coverage ratio, minimum

1.2

1

Debt covenant, debt leverage ratio, maximum

4

Lender fees

700,000

$ 300,000

$ 100,000

Commitment fee percentage

1.00%

1.00%

2.00%

Interest rate increase

2.00%

Line of credit facility, decrease limit

$ 25,000,000

Available revolving line of credit balance

$ 40,000,000

$ 13,000,000

Line of credit facility, increase limit

$ 12,500,000

$ 100,000,000

Decrease in interest rate margin

(1.00%)

Maturity, period prior to senior notes maturity

60 days

Revolving Credit Facility | Wells Fargo Credit Agreement | Subsequent Event

Line of Credit Facility [Line Items]

Maximum borrowing capacity

$ 75,000,000

Commitment fee percentage

1.00%

Maturity, period prior to senior notes maturity

60 days

Percentage of borrowing base

10.00%

Revolving Credit Facility | Wells Fargo Credit Agreement | Subsequent Event | Forecast

Line of Credit Facility [Line Items]

Line of credit facility, increase limit

$ 9,000,000

Revolving Credit Facility | Wells Fargo Credit Agreement | Minimum

Line of Credit Facility [Line Items]

Line of credit facility, increase limit

$ 6,250,000

Revolving Credit Facility | Wells Fargo Credit Agreement | Minimum | Subsequent Event

Line of Credit Facility [Line Items]

Line of credit facility, increase limit

$ 6,500,000

Revolving Credit Facility | Wells Fargo Credit Agreement | Maximum | Subsequent Event

Line of Credit Facility [Line Items]

Line of credit facility, increase limit

$ 7,500,000

Revolving Credit Facility | Wells Fargo Credit Agreement | LIBOR | Minimum

Line of Credit Facility [Line Items]

Basis spread on variable rate

1.75%

1.50%

Revolving Credit Facility | Wells Fargo Credit Agreement | LIBOR | Maximum

Line of Credit Facility [Line Items]

Basis spread on variable rate

2.25%

2.00%

Debt - Senior Notes - Narrative

Debt - Senior Notes - Narrative (Details) - USD ($)	Mar. 31, 2017	Apr. 29, 2015	Dec. 31, 2017	Dec. 31, 2016	Apr. 01, 2016	Dec. 31, 2015	Dec. 31, 2014
Debt Instrument [Line Items]
Debt financing costs			$ 900,000	$ 17,200,000		$ 1,500,000	$ 200,000
Unsecured Senior Notes
Debt Instrument [Line Items]
Debt instrument, interest rate		5.50%			6.50%
Purchase price percentage if debt covenants are not certified		100.00%
Legal fees	$ 100,000
Consent fee	$ 200,000		200,000	300,000	$ 300,000	0
Unsecured Senior Notes | 5.50% Senior Notes
Debt Instrument [Line Items]
Debt instrument, face amount		$ 55,000,000
Debt instrument, interest rate		5.50%
Proceeds from issuance of long-term debt		$ 53,500,000
Debt financing costs		$ 1,500,000
Accrued unpaid interest			$ 600,000	$ 600,000		$ 500,000
Unsecured Senior Notes | 5.50% Senior Notes | Before May 1, 2016
Debt Instrument [Line Items]
Redemption price, percentage		101.00%
Unsecured Senior Notes | 5.50% Senior Notes | May 1, 2016 through October 31, 2016
Debt Instrument [Line Items]
Redemption price, percentage		101.00%

Debt - Senior Notes - Amendment

Debt - Senior Notes - Amendments (Details) - Unsecured Senior Notes - USD ($)	Mar. 31, 2017	Apr. 19, 2018	Dec. 31, 2017	Feb. 01, 2017	Dec. 31, 2016	Apr. 01, 2016	Dec. 31, 2015	Nov. 02, 2015	Apr. 29, 2015
Debt Instrument [Line Items]
Debt covenant, permitted indebtedness				$ 135,000,000		$ 145,000,000		$ 125,000,000
Debt instrument, interest rate						6.50%			5.50%
Consent fee	$ 200,000		$ 200,000		$ 300,000	$ 300,000	$ 0
Legal fees	$ 100,000
Subsequent Event
Debt Instrument [Line Items]
Consent fee		$ 300,000
Interest rate if Form 10-K is filed on or before September 30, 2018		7.50%
Interest rate if Form 10-K has not been filed on or before September 30, 2018		8.50%
Interest rate subsequent to Form 10-K filing		7.50%

Debt - TPG Term Loan - Narrativ

Debt - TPG Term Loan - Narrative (Details) - USD ($)	Feb. 06, 2017	Aug. 22, 2016	Jun. 28, 2016	Mar. 31, 2017	Feb. 28, 2017	Mar. 31, 2017	Mar. 31, 2016	Jun. 30, 2017	Jun. 30, 2016	Sep. 30, 2017	Sep. 30, 2016	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Debt Instrument [Line Items]
Debt issuance costs												$ 900,000	$ 17,200,000	$ 1,500,000	$ 200,000
Loss on debt extinguishment and modifications						$ 11,921,000	$ 0	$ 11,921,000	$ 0	$ 11,921,000	$ 25,000	11,921,000	357,000	$ 12,000	$ 0
Term Loan | TPG Term Loan
Debt Instrument [Line Items]
Debt instrument, face amount			$ 60,000,000
Debt default, basis spread on interest rate	2.00%		2.00%
Maturity, period prior to senior notes maturity			90 days
Lender fees			$ 1,300,000										2,300,000
Deferred costs			$ 1,600,000
Amendment fee		$ 3,000,000		$ 6,100,000	$ 5,100,000								11,400,000
Debt issuance costs				400,000		$ 400,000						$ 400,000	$ 400,000
Interest rate, effective percentage			10.75%										10.84%
Accrued unpaid interest													$ 1,200,000
Loss on debt extinguishment and modifications				$ (11,900,000)
Term Loan | TPG Term Loan | September 30, 2017 to June 30, 2018
Debt Instrument [Line Items]
Periodic payment, principal			$ 375,000
Term Loan | TPG Term Loan | After June 30, 2018
Debt Instrument [Line Items]
Periodic payment, principal			$ 750,000
Term Loan | TPG Term Loan | LIBOR
Debt Instrument [Line Items]
Basis spread on variable rate			9.75%										9.75%
Secured Debt
Debt Instrument [Line Items]
Maximum borrowing capacity			$ 135,000,000

Debt - TPG Term Loan - Amendmen

Debt - TPG Term Loan - Amendments (Details) - Term Loan - TPG Term Loan - USD ($)	Feb. 06, 2017	Dec. 19, 2016	Aug. 22, 2016	Jun. 28, 2016	Mar. 31, 2017	Feb. 28, 2017	Jan. 31, 2018	Dec. 31, 2016
Debt Instrument [Line Items]
Reserve against borrowing base availability		$ 12,500,000	$ 12,500,000
Reserve against borrowing base after Form 10-Q is filed			7,500,000
Amendment fee			$ 3,000,000		$ 6,100,000	$ 5,100,000		$ 11,400,000
Prepayment right notice period		10 days
Waiver fee amount		$ 2,300,000
Legal fees		$ 400,000
Debt default, basis spread on interest rate	2.00%			2.00%
Principal amount of loan with amendment fees	$ 71,400,000
Debt instrument, face amount				$ 60,000,000
Forecast
Debt Instrument [Line Items]
Amendment fee							$ 8,400,000

Fair Value of Financial Instr_3

Fair Value of Financial Instruments - Schedule of Debt Instruments Measured at Fair Value (Details) - Fair Value, Measurements, Recurring - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Unsecured Senior Notes
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Unsecured Senior Notes	$ 55,000	$ 55,000	$ 55,000
Unsecured Senior Notes | Level 1
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Unsecured Senior Notes	0	0	0
Unsecured Senior Notes | Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Unsecured Senior Notes	0	0	0
Unsecured Senior Notes | Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Unsecured Senior Notes	50,000	49,800	55,000
TPG Term Loan
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
TPG Term Loan		71,400
TPG Term Loan | Level 1
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
TPG Term Loan		0
TPG Term Loan | Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
TPG Term Loan		0
TPG Term Loan | Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
TPG Term Loan		70,800
Wells Fargo Credit Agreement
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
TPG Term Loan				$ 4,028
Wells Fargo Credit Agreement | Level 1
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
TPG Term Loan				0
Wells Fargo Credit Agreement | Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
TPG Term Loan				4,028
Wells Fargo Credit Agreement | Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
TPG Term Loan				0
Wells Fargo Revolving Credit Facility
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Wells Fargo revolving credit facility	37,055	12,774	97,299	78,030
Wells Fargo Revolving Credit Facility | Level 1
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Wells Fargo revolving credit facility	0	0	0	0
Wells Fargo Revolving Credit Facility | Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Wells Fargo revolving credit facility	37,055	12,774	97,299	78,030
Wells Fargo Revolving Credit Facility | Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Wells Fargo revolving credit facility	$ 0	$ 0	$ 0	$ 0

Fair Value of Financial Instr_4

Fair Value of Financial Instruments - Schedule of Financial Instruments Measured at Fair Value (Details) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Contingent consideration	$ 12	$ 38	$ 8,717	$ 0	$ 0
Fair Value, Measurements, Recurring
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Contingent consideration	12	38	8,717
Fair Value, Measurements, Recurring | Level 1
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Contingent consideration	0	0	0
Fair Value, Measurements, Recurring | Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Contingent consideration	0	0	0
Fair Value, Measurements, Recurring | Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Contingent consideration	12	$ 38	8,717
Weichai warrant liability | Fair Value, Measurements, Recurring
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Weichai warrant liability	24,700
Weichai warrant liability | Fair Value, Measurements, Recurring | Level 1
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Weichai warrant liability	0
Weichai warrant liability | Fair Value, Measurements, Recurring | Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Weichai warrant liability	0
Weichai warrant liability | Fair Value, Measurements, Recurring | Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Weichai warrant liability	$ 24,700
Private placement warranty liability | Fair Value, Measurements, Recurring
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Weichai warrant liability			1,482	11,036
Private placement warranty liability | Fair Value, Measurements, Recurring | Level 1
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Weichai warrant liability			0	0
Private placement warranty liability | Fair Value, Measurements, Recurring | Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Weichai warrant liability			0	0
Private placement warranty liability | Fair Value, Measurements, Recurring | Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Weichai warrant liability			$ 1,482	$ 11,036

Fair Value of Financial Instr_5

Fair Value of Financial Instruments - Summary of Change in the Estimated Fair Value of Private Placement Warrants (Details) - Warrants - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation
Balance at beginning of year	$ 0	$ 1,482	$ 11,036	$ 24,525
Issuance of warrants	(20,700)	0	0	0
Increase (decrease) in value	4,000	(1,413)	(9,299)	(6,169)
Balance at end of year	24,700	0	1,482	11,036
Private placement warranty liability
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation
Issuance of warrants	$ 0	$ (69)	$ (255)	$ (7,320)

Fair Value of Financial Instr_6

Fair Value of Financial Instruments - Schedule of Inputs of the Black-Scholes Option Pricing Model (Details) - Black-Scholes option pricing model - Level 3	Dec. 31, 2017$ / shares	Dec. 31, 2015$ / shares	Dec. 31, 2014$ / shares
Weichai warrant liability
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Contractual term	1 year
Private placement warranty liability
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Contractual term		6 months 29 days	1 year 4 months
Market value of the Common Stock | Weichai warrant liability
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Option pricing model input	7.50
Market value of the Common Stock | Private placement warranty liability
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Option pricing model input		18.25	51.61
Exercise price | Private placement warranty liability
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Option pricing model input		13	13
Risk-free interest rate | Weichai warrant liability
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Option pricing model input	0.018
Estimated price volatility | Weichai warrant liability
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Option pricing model input	0.95
Estimated price volatility | Private placement warranty liability
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Option pricing model input		0.55	0.55
Dividend yield | Weichai warrant liability
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Option pricing model input	0

Fair Value of Financial Instr_7

Fair Value of Financial Instruments - Narrative (Details) $ in Thousands	1 Months Ended
	May 31, 2015USD ($)
Powertrain
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Fair value of contingent consideration	$ 8,200

Fair Value of Financial Instr_8

Fair Value of Financial Instruments - Change in Estimated Fair Value Contingent Consideration (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016
Loss Contingency Accrual [Roll Forward]
Balance at beginning of year	$ 38	$ 8,717	$ 0	$ 0
Initial estimate of contingent consideration liability	0	0	8,740	3,840
Increase (decrease) in value reflected in income	0	(230)	(23)	(3,840)
Payment of contingent consideration	(26)	(8,449)	0	0
Balance at end of year	12	38	8,717	0
Contingent consideration	12	26	8,275	0	$ 20	$ 29	$ 30	$ 88	$ 100	$ 5,481
Short-term contingent consideration at end of year	0	$ 12	$ 442	$ 0
Interest on contingent consideration	100
Cash paid in excess of initial fair value estimate	$ 100

Defined Contribution Plans (Det

Defined Contribution Plans (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Retirement Benefits [Abstract]
Employer contributions	$ 0.1	$ 0.1	$ 0.1	$ 0.1

Commitments and Contingencies (

Commitments and Contingencies (Details)

Jan. 22, 2019USD ($)

Oct. 30, 2018USD ($)

Jun. 30, 2017USD ($)

Jun. 30, 2016USD ($)

Mar. 31, 2018USD ($)

Sep. 30, 2017USD ($)

Dec. 31, 2014diesel_engine

Dec. 31, 2018USD ($)

Dec. 31, 2017USD ($)letter_of_credit

Jun. 30, 2018USD ($)installment_payment

Apr. 11, 2019USD ($)

Jun. 01, 2017USD ($)

Apr. 24, 2015USD ($)

Oct. 24, 2014USD ($)

Loss Contingencies [Line Items]

Number of outstanding letters of credit | letter_of_credit

2

Outstanding letters of credit amount

$ 500,000

Asset Purchase Agreement - Alternative Fuel Supply Technology

Loss Contingencies [Line Items]

Consideration received on transaction

$ 500,000

Payments for commissions

$ 1,200,000

Subsequent Event | Asset Purchase Agreement - Alternative Fuel Supply Technology

Loss Contingencies [Line Items]

Consideration received on transaction

$ 1,500,000

Payments for commissions

1,200,000

$ 400,000

Designation of diesel engines purchased

Loss Contingencies [Line Items]

Number of engines affected | diesel_engine

2,300

Guinta v. Power Solutions International, Inc. | Forecast

Loss Contingencies [Line Items]

Litigation settlement payment

$ 8,500,000

Jerome Treadwell v. The Company | Subsequent Event

Loss Contingencies [Line Items]

Recovery per negligent violation

$ 1,000

Recovery per intentional or reckless violation

$ 5,000

Settled Litigation | Carl Trent, Kenneth Trent, and CKT Holdings, Inc. vs. 3PI and PSI

Loss Contingencies [Line Items]

Range of damages sought

$ 3,000,000

Settlement payments

$ 1,750,000

Legal settlement accrual

$ 625,000

Settled Litigation | Carl Trent, Kenneth Trent, and CKT Holdings, Inc. vs. 3PI and PSI | Forecast

Loss Contingencies [Line Items]

Settlement payments

$ 1,250,000

Number of settlement payments | installment_payment

12

Settled Litigation | Carl Trent, Kenneth Trent, and CKT Holdings, Inc. vs. 3PI and PSI | Tax gross-up payment under the SPA

Loss Contingencies [Line Items]

Damages sought

$ 350,000

Settled Litigation | Carl Trent, Kenneth Trent, and CKT Holdings, Inc. vs. 3PI and PSI | Equity payment due under the SPA

Loss Contingencies [Line Items]

Damages sought

$ 9,300,000

Settled Litigation | Carl Trent, Kenneth Trent, and CKT Holdings, Inc. vs. 3PI and PSI | Compensatory damages | Compensatory damages

Loss Contingencies [Line Items]

Counterclaim damages sought

$ 20,000,000

Settled Litigation | Carl Trent, Kenneth Trent, and CKT Holdings, Inc. vs. 3PI and PSI | Consequential and punitive damages, in excess of | Consequential and punitive damages, in excess of

Loss Contingencies [Line Items]

Counterclaim damages sought

$ 20,000,000

Settled Litigation | Dorvit v. Winemaster | Subsequent Event

Loss Contingencies [Line Items]

Range of damages sought

$ 1,900,000

Minimum | Settled Litigation | Carl Trent, Kenneth Trent, and CKT Holdings, Inc. vs. 3PI and PSI

Loss Contingencies [Line Items]

Range of damages sought

$ 500,000

Maximum | Subsequent Event | Asset Purchase Agreement - Alternative Fuel Supply Technology

Loss Contingencies [Line Items]

Payments for commissions

$ 4,500,000

Maximum | Settled Litigation | Carl Trent, Kenneth Trent, and CKT Holdings, Inc. vs. 3PI and PSI

Loss Contingencies [Line Items]

Range of damages sought

$ 1,000,000

Income Taxes - Schedule of Expe

Income Taxes - Schedule of Expense (Benefit) for Income Taxes (Details) - USD ($) $ in Thousands	3 Months Ended								6 Months Ended		9 Months Ended		12 Months Ended
	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Jun. 30, 2017	Jun. 30, 2016	Sep. 30, 2017	Sep. 30, 2016	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Current tax expense (benefit):
Federal													$ 127	$ (6,568)	$ (859)	$ 7,476
State													77	60	215	1,892
Current tax expense (benefit)													204	(6,508)	(644)	9,368
Deferred tax expense (benefit)
Federal													100	13,907	(6,713)	(1,183)
State													139	4,214	(2,345)	(441)
Total deferred tax expense (benefit)				$ 469				$ (1,628)	$ 602	$ 18,029	$ 746	$ 18,179	239	18,121	(9,058)	(1,624)
Total tax expense (benefit)	$ (320)	$ 149	$ 135	$ 479	$ (1,238)	$ (1,792)	$ 18,000	$ (3,357)					$ 443	$ 11,613	$ (9,702)	$ 7,744

Income Taxes - Narrative (Detai

Income Taxes - Narrative (Details) - USD ($)	3 Months Ended								12 Months Ended
	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Income Tax Contingency [Line Items]
Income tax refunds									$ 6,300,000	$ 4,600,000
Cash payments for taxes											$ 7,100,000	$ 5,300,000
Pretax income including permanently excludable income									(47,200,000)	(35,900,000)	(12,600,000)
Gain from change in fair value of warrants	$ 1,500,000	$ 1,700,000	$ 800,000	$ 0	$ 0	$ 0	$ (157,000)	$ (1,256,000)	$ 4,000,000	$ (1,413,000)	$ (9,300,000)	$ (6,170,000)
Effective income tax rate if the impact of the change in valuation of warrants had been excluded									(0.90%)	(32.40%)	77.00%	26.50%
Provisional adjustment to decrease net deferred tax assets	(10,800,000)								$ (10,800,000)
Corresponding net adjustment to deferred tax expense	11,300,000
Period to carry forward general business credits									20 years
Valuation allowance against net deferred tax assets	31,992,000				$ 26,847,000		$ 17,800,000		$ 31,992,000	$ 26,847,000	$ 0	$ 0
Tax credit carryforwards	2,400,000								2,400,000
Federal net operating loss carryforwards	10,800,000								10,800,000
State net operating loss carryforwards	4,600,000								4,600,000
Possible decrease in liability for unrecognized tax benefits, excluding interest and penalties	$ 200,000								200,000
Private placement warranty liability
Income Tax Contingency [Line Items]
Permanently excludable income (expense) associated with change in valuation of warrants									$ 4,000,000	$ (1,400,000)	$ 9,300,000	$ (29,200,000)

Income Taxes - Reconciliation o

Income Taxes - Reconciliation of Effective Tax Rate to the Statutory Rate (Details) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Amount
Income tax (benefit) expense at federal statutory rate									$ (16,037)	$ (12,192)	$ (4,282)	$ 9,935
State income tax, net of federal benefit									(2,283)	(1,758)	(1,101)	1,295
Non-deductible warrants (income)/expense									1,360	(481)	(3,162)	(2,098)
Domestic production activity									0	0	0	(334)
Other permanent differences									106	110	137	191
Research and development tax credits									(426)	(837)	(1,632)	(1,953)
Tax reserve reassessment									104	(141)	412	246
Federal tax rate change									10,899	0	0	0
Change in valuation allowance									4,956	26,846	0	0
3PI Settlement									1,976	0	0	0
Other, net									(212)	66	(74)	462
Total tax expense (benefit)	$ (320)	$ 149	$ 135	$ 479	$ (1,238)	$ (1,792)	$ 18,000	$ (3,357)	$ 443	$ 11,613	$ (9,702)	$ 7,744
Percent
Income tax (benefit) expense at federal statutory rate									34.00%	34.00%	34.00%	34.00%
State income tax, net of federal benefit									4.80%	4.90%	8.70%	4.40%
Non-deductible warrants (income)/expense									(2.90%)	1.30%	25.10%	(7.20%)
Domestic production activity									(0.00%)	(0.00%)	(0.00%)	(1.10%)
Other permanent differences									(0.20%)	(0.30%)	(1.10%)	0.70%
Research and development tax credits									0.90%	2.30%	13.00%	(6.70%)
Tax reserve reassessment									(0.20%)	0.40%	(3.30%)	0.80%
Federal tax rate change									(23.10%)	0.00%	0.00%	0.00%
Change in valuation allowance									(10.40%)	(74.90%)	0.00%	0.00%
3PI Settlement									(4.20%)	0.00%	0.00%	0.00%
Other, net									0.40%	(0.10%)	0.60%	1.60%
Income tax expense (benefit)									(0.90%)	(32.40%)	77.00%	26.50%

Income Taxes - Schedule of Sign

Income Taxes - Schedule of Significant Components of the Deferred Income Tax Assets and Liabilities (Details) - USD ($)	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Deferred tax assets:
Net operating loss carryforwards	$ 15,399,000				$ 1,154,000				$ 66,000	$ 0
Research and development credits	2,806,000				2,118,000				139,000	0
Other state credits	989,000				407,000				164,000	0
Inventory	2,560,000				5,837,000				5,094,000	3,035,000
Allowances and bad debts	596,000				501,000				334,000	119,000
Accrued warranty	3,387,000				3,820,000				1,413,000	948,000
Accrued wages and benefits	351,000				786,000				893,000	917,000
Stock-based compensation	645,000				1,021,000				756,000	576,000
Capitalized research and development costs	1,090,000				2,291,000				2,617,000	2,316,000
Intangible amortization	1,734,000				4,519,000				4,311,000	0
Other	3,397,000				6,638,000				5,069,000	3,615,000
Total deferred tax assets	32,954,000				29,092,000				20,856,000	11,526,000
Valuation allowance	(31,992,000)				(26,847,000)		$ (17,800,000)		0	0
Total deferred tax assets, net of valuation allowance	962,000				2,245,000				20,856,000	11,526,000
Deferred tax liabilities:
Intangible amortization	0				0				0	(1,091,000)
Tax depreciation in excess of book depreciation on property, plant and equipment	(1,665,000)				(2,709,000)				(3,199,000)	(1,870,000)
Total deferred tax liabilities	(1,665,000)				(2,709,000)				(3,199,000)	(2,961,000)
Net deferred tax (liability) asset	(703,000)				(464,000)
Current deferred tax assets, net										8,552,000
Net deferred tax (liability) asset	(703,000)	$ (1,210,000)	$ (1,066,000)	$ (933,000)	(464,000)	$ (522,000)	(372,000)	$ 0	0
Deferred income taxes	$ 0				$ 0	$ 0	$ 0	$ 19,285,000	17,657,000	13,000
Net deferred tax asset									$ 17,657,000	$ 8,565,000

Income Taxes - Schedule of the

Income Taxes - Schedule of the Change in Unrecognized Tax Benefits (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Reconciliation of Unrecognized Tax Benefits, Excluding Amounts Pertaining to Examined Tax Returns
Balance at beginning of year	$ 1,202	$ 1,338	$ 894	$ 614
Additions based on tax positions related to the current year	105	168	525	373
Additions/(reductions) for tax positions of prior years	0	(304)	(81)	(93)
Balance at end of year	$ 1,307	$ 1,202	$ 1,338	$ 894

Stockholders' Equity - Common S

Stockholders' Equity - Common Stock and Series B Convertible Preferred Stock (Details)	May 03, 2019	Apr. 23, 2019shares	Apr. 01, 2019	Mar. 31, 2017shares	Mar. 31, 2017shares	Dec. 31, 2017series_of_preferred$ / sharesshares	Dec. 31, 2016$ / sharesshares	Dec. 31, 2015$ / sharesshares	Dec. 31, 2014$ / sharesshares
Shares
Common stock, issued, beginning balance (in shares)						11,567,000	11,413,000	11,408,000	11,299,000
Treasury stock shares, beginning balance (in shares)						645,000	660,000	677,000	777,000
Common stock, outstanding, beginning balance (in shares)						10,922,000	10,753,000	10,731,000	10,522,000
Treasury stock shares issued (in shares)						(11,000)	(15,000)	(17,000)	(100,000)
Common stock, issued, ending balance (in shares)						19,067,000	11,567,000	11,413,000	11,408,000
Treasury stock shares, ending balance (in shares)						634,000	645,000	660,000	677,000
Common stock, outstanding, ending balance (in shares)						18,433,000	10,922,000	10,753,000	10,731,000
Series B convertible preferred stock, authorized (in shares)						5,000,000	5,000,000	5,000,000	5,000,000
Series B convertible preferred stock, par value (in dollars per share) | $ / shares						$ 0.001	$ 0.001	$ 0.001	$ 0.001
Series A convertible preferred stock, issued (in shares)						0	0	0	0
Series A convertible preferred stock, outstanding (in shares)						0	0	0	0
Series B
Shares
Series B convertible preferred stock, authorized (in shares)						5,000,000
Series B convertible preferred stock, par value (in dollars per share) | $ / shares						$ 0.001
Number of series of Preferred authorized | series_of_preferred						2
Common Stock
Shares
Conversion of outstanding stock (in shares)						11,000	15,000	17,000	100,000
Share Purchase Agreement, Weichai Transaction | Redeemable Convertible Series B Preferred Stock
Shares
Shares issued to Weichai (in shares)				2,385,624
Issuance of redeemable convertible Series B Preferred Stock, net of fees (in shares)				4,771,248		4,771,000
Share Purchase Agreement, Weichai Transaction | Common Stock
Shares
Shares issued to Weichai (in shares)					2,728,752	2,729,000
Private placement warranty liability
Shares
Warrants exercised (in shares)							153,916	5,000	109,585
Subsequent Event | Share Purchase Agreement, Second Amended And Restated Warrant | Series B
Shares
Warrants exercised (in shares)		4,049,759
Percent ownership of outstanding common stock	51.50%		51.00%

Stockholders' Equity - Private

Stockholders' Equity - Private Placement Warrants (Details) - Private placement warranty liability - $ / shares	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014	Apr. 30, 2016	Apr. 30, 2011
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Warrants term					5 years
Common stock shares issuable private placement warrants (in shares)					750,002
Exercise price of warrants or rights (in dollars per share)					$ 13
Warrants exercised (in shares)	153,916	5,000	109,585
Number of private placement warrants expired (in shares)				128,341
Common stock reserved for future issuance (in shares)		282,257	287,257

Stock-Based Compensation - Narr

Stock-Based Compensation - Narrative (Details) - SARs - shares	12 Months Ended
	Dec. 31, 2013	Dec. 31, 2017	Dec. 31, 2012
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share initially made available for awards (in shares)			830,925
Additional shares added to the plan (in shares)	700,000
Share available for issuance of future awards (in shares)		567,311

Stock-Based Compensation - 2012

Stock-Based Compensation - 2012 SAR Award Narrative (Details) - SARs $ / shares in Units, $ in Millions	1 Months Ended				3 Months Ended	12 Months Ended
	Jul. 31, 2015USD ($)$ / sharesshares	Jun. 30, 2015$ / sharesshares	Jun. 30, 2014shares	Jun. 30, 2012USD ($)valuation_dateanniversaryshares	Jun. 30, 2016USD ($)$ / sharesshares	Dec. 31, 2017shares	Dec. 31, 2016shares	Dec. 31, 2015USD ($)shares	Dec. 31, 2014USD ($)shares	Dec. 31, 2013shares
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Granted (in shares)						5,000	106,800	60,000	0
Exercised (in shares)						0	0	0	120,000
Expired (in shares)						6,750	61,291	0	0
Forfeited (in shares)						67,130	195,490	0	0
2012 SAR
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Granted (in shares)				543,872
Exercise price (in dollars per share) | $ / shares		$ 22.07			$ 22.07
Number of grant date anniversaries | anniversary				3
Contractual term				10 years
Number of valuation dates to trigger SAR shares to be exercisable | valuation_date				7
Number of consecutive valuation dates needed | valuation_date				10
Discount rate				15.00%
Resulting fair value per share (in dollars per share) | $ / shares					$ 3.31
Aggregate compensation expense | $				$ 1.8
Period until market condition will be met				1 year 9 months 11 days
Unvested shares (in shares)		181,290
Period for deferred vesting		30 days
Exercised (in shares)									120,000	181,291
Vested (in shares)			181,291
Expired (in shares)					61,291
Forfeited (in shares)					181,290
Previously recognized expensed now reversed | $					$ 0.1
2012 SAR | Selling, General and Administrative Expenses
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Aggregate compensation expense | $								$ 0.2	$ 0.3
SAR And Bonus Agreement
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Limit of sale of any vested SAR | $	$ 0.8
Period without written consent of the compensation committee	6 months
Annual bonus | $	$ 0.3
Incremental compensation expense (in dollars per share) | $ / shares	$ 1.84
Incremental compensation expense from modification | $	$ 0.3
SAR And Bonus Agreement | Tranche one
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Unvested shares (in shares)	100,000
SAR And Bonus Agreement | Tranche two
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Unvested shares (in shares)	81,290

Stock-Based Compensation - Sche

Stock-Based Compensation - Schedule of Fair Value Assumptions (Details) - SARs - $ / shares	1 Months Ended					12 Months Ended
	Feb. 29, 2016	Oct. 31, 2015	Jul. 31, 2015	Jun. 30, 2015	Jun. 30, 2012	Dec. 31, 2017	Jun. 30, 2016
2012 SAR
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Market value closing price of the Common Stock (in dollars per share)				$ 53.64			$ 16.50
Exercise price (in dollars per share)				$ 22.07			$ 22.07
Risk-free interest rate				1.10%	0.92%
Expected volatility				50.00%	55.00%
Expected term				3 years 6 months	6 years
Dividend yield				0.00%	0.00%
Fair value of the Common Stock (in dollars per share)				$ 31.97
2012 SAR Bonus Agreement
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Market value closing price of the Common Stock (in dollars per share)			$ 51.13
Exercise price (in dollars per share)			$ 22.07
Risk-free interest rate			1.53%
Expected volatility			50.00%
Expected term			4 years 10 months 24 days
Dividend yield			0.00%
Fair value of the Common Stock (in dollars per share)			$ 33.81
2015 SARs
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Market value closing price of the Common Stock (in dollars per share)		$ 24.41
Exercise price (in dollars per share)		$ 24.41
Risk-free interest rate		1.76%
Expected volatility		50.00%
Expected term		7 years 3 months
Dividend yield		0.00%
February 2016 SAR awards
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Market value closing price of the Common Stock (in dollars per share)	$ 10.76
Exercise price (in dollars per share)	$ 11.25
Risk-free interest rate	1.36%
Expected volatility	55.00%
Expected term	5 years 9 months
Dividend yield	0.00%
2017 SARs
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Market value closing price of the Common Stock (in dollars per share)						$ 7.37
Exercise price (in dollars per share)						$ 7.37
Risk-free interest rate						2.10%
Expected volatility						58.50%
Expected term						6 years
Dividend yield						0.00%

Stock-Based Compensation - 2015

Stock-Based Compensation - 2015 SAR Award Narrative (Details) - SARs - USD ($) $ / shares in Units, $ in Millions	1 Months Ended	3 Months Ended	12 Months Ended
	Oct. 31, 2015	Mar. 31, 2017	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Award (in shares)			5,000	106,800	60,000	0
Forfeited (in shares)			67,130	195,490	0	0
2015 SARs
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Award (in shares)	60,000
Exercise price (in dollars per share)	$ 24.41
Contractual term	10 years
Resulting fair value per share (in dollars per share)	$ 12.96
Forfeited (in shares)		60,000
Previously recognized expensed now reversed		$ 0.2
2015 SARs | Selling, General and Administrative Expenses
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share-based compensation expense				$ 0.1

Stock-Based Compensation - Febr

Stock-Based Compensation - February 2016 SAR Award Narrative (Details) - SARs - USD ($) $ / shares in Units, $ in Millions	1 Months Ended	12 Months Ended
	Feb. 29, 2016	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Award (in shares)		5,000	106,800	60,000	0
February 2016 SAR awards
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Award (in shares)	103,350		106,800
Resulting fair value per share (in dollars per share)	$ 5.37
Vesting period	2 years
February 2016 SAR awards | Selling, General and Administrative Expenses
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share-based compensation expense		$ 0.2	$ 0.2

Stock-Based Compensation - 2017

Stock-Based Compensation - 2017 SAR Award Narrative (Details) - SARs - $ / shares	1 Months Ended	12 Months Ended
	Feb. 29, 2016	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Award (in shares)		5,000	106,800	60,000	0
2017 SARs
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Award (in shares)		5,000
Resulting fair value per share (in dollars per share)		$ 4.10
Vesting period	2 years

Stock-Based Compensation - Sc_2

Stock-Based Compensation - Schedule of SAR Activity (Details) - SARs - USD ($) $ / shares in Units, $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Shares
Outstanding, beginning balance (in shares)	152,600	302,581	242,581	362,581
Granted (in shares)	5,000	106,800	60,000	0
Exercised (in shares)	0	0	0	(120,000)
Forfeited (in shares)	(67,130)	(195,490)	0	0
Expired (in shares)	(6,750)	(61,291)	0	0
Outstanding, ending balance (in shares)	83,720	152,600	302,581	242,581	362,581
Exercisable (in shares)	39,360	0	61,291	61,291
Weighted-Average Exercise Price
Outstanding, beginning balance (in dollars per share)	$ 16.55	$ 22.53	$ 22.07	$ 22.07
Granted (in dollars per share)	7.37	11.43	24.41	0
Exercised (in dollars per share)	0	0	0	22.07
Forfeited (in dollars per share)	23.16	21.28	0	0
Expired (in dollars per share)	12.68	22.07	0	0
Outstanding, ending balance (in dollars per share)	11.02	16.55	22.53	22.07	$ 22.07
Exercisable (in dollars per share)	$ 11.25	$ 0	$ 22.07	$ 22.07
Weighted-Average Remaining Contractual Term (years)
Outstanding (term)	8 years 2 months 16 days	9 years 7 days	7 years 1 month 6 days	7 years 5 months 8 days	8 years 5 months 8 days
Exercisable (term)	8 years 1 month 24 days		6 years 5 months 8 days	7 years 5 months 8 days
Aggregate Intrinsic Value (in thousands)
Outstanding	$ 1,000	$ 0	$ 0	$ 7,166	$ 19,228
Exercised				6,673
Exercisable	$ 0	$ 0	$ 0	$ 1,811

Stock-Based Compensation - Sc_3

Stock-Based Compensation - Schedule of Restricted Stock Activity (Details) - Restricted Stock Awards - $ / shares	1 Months Ended	12 Months Ended
	Jul. 31, 2017	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Shares
Outstanding, beginning balance (in shares)		104,340	130,244	154,251	162,993
Granted (in shares)	379,472	437,472	750	1,000	23,000
Forfeited (in shares)		(29,144)	(4,668)	(800)	(12,000)
Vested (in shares)		(16,395)	(21,986)	(24,207)	(19,742)
Outstanding, ending balance (in shares)		496,273	104,340	130,244	154,251
Weighted-Average Grant Date Fair Value
Outstanding, beginning balance (in dollars per share)		$ 41.61	$ 41.77	$ 42.11	$ 39.29
Granted (in dollars per share)		8.13	18.50	28.48	71.47
Forfeited (in dollars per share)		38.33	36	65.51	60.44
Vested (in dollars per share)		44.19	42.96	42.63	41.89
Outstanding, ending balance (in dollars per share)		$ 12.20	$ 41.61	$ 41.77	$ 42.11

Stock-Based Compensation - Rest

Stock-Based Compensation - Restricted Stock Awards Narrative (Details) - Restricted Stock Awards - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share-based compensation expense	$ 1.4	$ 1	$ 1	$ 1
Fair value of restricted stock vested	0.7	0.9	1	0.8
Unrecognized compensation expense	$ 4.6	$ 3.5	$ 4.7	$ 5.8
Weighted-average period the unrecognized compensation cost is expected to be recognized	3 years 14 days

Stock-Based Compensation - 20_2

Stock-Based Compensation - 2017 Retention Program Narrative (Details) - Restricted Stock Awards - USD ($) $ in Millions	1 Months Ended	12 Months Ended
	Jul. 31, 2017	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Granted (in shares)	379,472	437,472	750	1,000	23,000
Outstanding	$ 2.9
Cash awards	$ 3.3

Stock-Based Compensation - Othe

Stock-Based Compensation - Other Equity Award (Details) - Restricted Stock Awards - USD ($) $ in Millions	3 Months Ended		12 Months Ended
	Mar. 31, 2020	Mar. 31, 2017	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2012
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share-based compensation expense			$ 1.4	$ 1	$ 1	$ 1
RSA 2012
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Restricted stock awarded							$ 0.5
Share-based compensation expense		$ (1)		$ 0.4	$ 0.3	$ 0.1
RSA 2012 | Forecast
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Restricted stock upon vesting	$ 2

Earnings Per Share (Details)

Earnings Per Share (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended								6 Months Ended		9 Months Ended		12 Months Ended
	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Jun. 30, 2017	Jun. 30, 2016	Sep. 30, 2017	Sep. 30, 2016	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Numerator:
Net (loss) income	$ (6,130)	$ (9,202)	$ (7,747)	$ (24,533)	$ (6,640)	$ (8,717)	$ (28,792)	$ (3,323)	$ (32,280)	$ (32,115)	$ (41,482)	$ (40,832)	$ (47,612)	$ (47,472)	$ (2,891)	$ 21,477
Less: Deemed dividend on Series B convertible preferred stock													(37,860)	0	0	0
Net (loss) income available to common stockholders	$ (37,197)	$ (12,805)	$ (10,937)	$ (24,533)									(85,472)	(47,472)	(2,891)	21,477
Exclude (gain) loss from change in fair value of warrants													0	(1,413)	(9,300)	(6,170)
Net (loss) income available to common stockholders - diluted													$ (85,472)	$ (48,885)	$ (12,191)	$ 15,307
Shares used in computing net (loss) income per share:
Weighted average basic shares outstanding (in shares)								10,819					13,787	10,931	10,808	10,705
Effect of dilutive securities (in shares)													0	0	183	426
Weighted average common shares outstanding-diluted (in shares)								10,819					13,787	10,931	10,991	11,131
(Loss) earnings per common share:
(Loss) Earnings per share — basic (in dollars per share)								$ (0.42)					$ (6.20)	$ (4.34)	$ (0.27)	$ 2.01
(Loss) Earnings per share — diluted (in dollars per share)								$ (0.42)					$ (6.20)	$ (4.47)	$ (1.11)	$ 1.38
Antidilutive shares (in shares)													6,300	300	100

Related Party Transactions - 3P

Related Party Transactions - 3PI Lease Agreement (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Limited Liability Company
Related Party Transaction [Line Items]
Expenses from transactions with related party	$ 0.5	$ 0.5	$ 0.5	$ 0.4

Related Party Transactions - Tr

Related Party Transactions - Transactions with Joint Ventures (Details) - USD ($) $ in Thousands	May 31, 2017	Apr. 13, 2016	Dec. 07, 2012	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Related Party Transaction [Line Items]
Other (income) expense, net				$ 225	$ 9	$ (2,142)	$ (453)	$ (146)	$ (62)	$ (92)	$ (59)	$ (2,361)	$ (359)	$ (144)	$ 283
Corporate Joint Venture
Related Party Transaction [Line Items]
Other (income) expense, net													$ 400	100	$ (300)
Doosan-PSI, LLC | Corporate Joint Venture
Related Party Transaction [Line Items]
Investment amount with related party														$ 1,000
Percent of noncontrolling interest														50.00%
MAT-PSI Holdings, LLC | Green Power | Corporate Joint Venture
Related Party Transaction [Line Items]
Ownership percentage			100.00%
Investment amount with related party			$ 900
Percent of noncontrolling interest			50.00%
SW | Sterling And Wilson Cogen Solutions, LLC | Corporate Joint Venture
Related Party Transaction [Line Items]
Investment amount with related party	$ 200	$ 200
Percent of noncontrolling interest	49.00%	49.00%

Related Party Transactions - _2

Related Party Transactions - Transactions with Related Individuals (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Father of Management
Related Party Transaction [Line Items]
Paid to individual	$ 0.2	$ 0.2	$ 0.2	$ 0.2

Selected Quarterly Financial _3

Selected Quarterly Financial Data (Unaudited) - CONDENSED CONSOLIDATED BALANCE SHEETS (Details) - USD ($) $ in Thousands	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Current assets:
Cash and cash equivalents		$ 0	$ 0	$ 342	$ 2,292	$ 1,610	$ 435	$ 1,495	$ 8,445	$ 6,561	$ 6,306
Cash and cash equivalents	$ 0	0	0	342	2,292	1,610	435	1,495	8,445	6,561	6,306
Accounts receivable, net of allowances of $1,820, $1,045, $816 and $306 for 2017, 2016, 2015 and 2014, respectively	68,660	60,811	56,673	64,305	60,336	53,364	57,884	45,384	70,532	76,266
Income tax receivable	1,018	841	1,996	6,829	7,127	5,737	3,384	1,723	5,265	0
Inventories, net	86,724	113,074	103,335	97,286	100,548	111,133	115,062	139,519	162,095	106,250
Prepaid expenses and other current assets	14,359	14,536	12,453	15,291	13,644	5,146	4,026	4,132	2,703	4,840
Total current assets	170,761	189,262	174,457	184,053	183,947	176,990	180,791	192,253	249,040	202,469
Property, plant and equipment, net	18,960	18,974	19,050	19,230	20,127	20,257	20,386	20,662	22,809	17,954
Intangible assets, net	21,491	22,401	23,610	24,819	26,029	27,459	28,888	30,316	31,745	21,192
Goodwill	29,835	29,835	29,835	29,835	29,835	29,835	29,835	29,835	29,835	23,414	0
Deferred income taxes	0				0	0	0	19,285	17,657	13
Other noncurrent assets	5,972	6,035	4,518	5,053	4,681	2,821	2,621	2,664	2,751	1,903
TOTAL ASSETS	247,019	266,507	251,470	262,990	264,619	257,362	262,521	295,015	353,837	266,945
Current liabilities:
Accounts payable	51,225	54,195	55,610	67,167	53,588	45,764	49,729	43,160	79,823	67,713
Current maturities of long-term debt	0				750	375	0	0	0	1,667
Revolving line of credit, current	37,055	41,332	25,263	16,887	12,774	16,994	14,038	0	0	0
Contingent consideration	12	20	29	30	26	88	100	5,481	8,275	0
Other accrued liabilities	38,362	41,393	35,379	35,234	32,507	22,405	19,182	17,929	17,846	18,182
Total current liabilities	126,654	136,940	116,281	119,318	99,645	85,626	83,049	66,570	105,944	87,562
Long-term obligations
Revolving line of credit	0				0	0	0	80,568	97,299	78,030
Deferred income taxes	703	1,210	1,066	933	464	522	372	0	0
Warrant, noncurrent	24,700	23,200	21,500	20,700	0	0	0	226	1,482	11,036
Long-term debt, less current maturities, net	54,439	54,305	54,168	54,045	110,392	111,517	110,929	53,799	53,805	2,361
Other noncurrent liabilities	8,351	13,312	12,438	13,328	13,458	12,730	12,833	11,952	10,434	1,473
TOTAL LIABILITIES	214,847	228,967	205,453	208,324	223,959	210,395	207,184	213,115	268,964	180,462
MEZZANINE EQUITY / STOCKHOLDERS’ EQUITY
Series B convertible preferred stock, net of issuance costs	62,900	31,411	27,807	24,617
Preferred stock	0	0	0	0	0	0	0	0	0	0
Common stock - $0.001 par value; 50,000 shares authorized; 19,067, 11,567, 11,413 and 11,408 shares issued; 18,433, 10,922, 10,753 and 10,731 shares outstanding at December 31, 2017, 2016, 2015 and 2014, respectively	19	14	14	14	12	12	12	11	11	11
Additional paid-in capital	123,838	91,737	96,543	100,686	86,764	86,408	86,043	83,729	83,377	81,746
(Accumulated deficit) retained earnings	(82,147)	(76,018)	(66,817)	(59,070)	(34,535)	(27,895)	(19,180)	9,612	12,937	15,828
Treasury stock, at cost; 634, 645, 660 and 677 shares at December 31, 2017, 2016, 2015 and 2014, respectively	(9,538)	(9,604)	(11,530)	(11,582)	(11,581)	(11,558)	(11,537)	(11,452)	(11,452)	(11,102)
TOTAL STOCKHOLDERS’ EQUITY	32,172	6,129	18,210	30,048	40,660	46,967	55,337	81,900	84,873	86,483	$ 47,607
TOTAL LIABILITIES AND STOCKHOLDERS’ EQUITY	$ 247,019	$ 266,507	$ 251,470	$ 262,990	$ 264,619	$ 257,362	$ 262,521	$ 295,015	$ 353,837	$ 266,945

Selected Quarterly Financial _4

Selected Quarterly Financial Data (Unaudited) - CONDENSED CONSOLIDATED RESULTS OF OPERATIONS (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended								6 Months Ended		9 Months Ended		12 Months Ended
	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Jun. 30, 2017	Jun. 30, 2016	Sep. 30, 2017	Sep. 30, 2016	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Quarterly Financial Information Disclosure [Abstract]
Net sales	$ 131,476	$ 99,953	$ 100,922	$ 84,265	$ 98,280	$ 78,944	$ 85,771	$ 76,470					$ 416,616	$ 339,465	$ 362,387	$ 347,580
Cost of sales	115,981	86,702	88,443	74,497	86,376	72,820	81,253	69,827					365,623	310,276	311,148	283,540
Gross profit	15,495	13,251	12,479	9,768	11,904	6,124	4,518	6,643					50,993	29,189	51,239	64,040
Operating expenses:
Research, development and engineering expenses	6,459	5,687	3,848	3,950	4,742	4,498	4,817	4,904					19,944	18,961	23,574	19,305
Selling, general and administrative expenses	11,297	12,062	10,688	10,209	8,563	6,855	6,699	6,405					44,256	28,522	28,837	23,142
Asset impairment charges	1	0	0	0	167	38	1,064	345					1	1,614	11,686	310
Amortization of intangible assets	1,210	1,210	1,209	1,209	1,430	1,429	1,429	1,428					4,838	5,716	4,582	1,013
Change in fair value of contingent consideration					0	0	(283)	0					0	(283)	(23)	(3,840)
Total operating expenses	18,967	18,959	15,745	15,368	14,902	12,820	13,726	13,082					69,039	54,530	68,656	39,930
Operating (loss) income	(3,472)	(5,708)	(3,266)	(5,600)	(2,998)	(6,696)	(9,208)	(6,439)					(18,046)	(25,341)	(17,417)	24,110
Other expense (income):
Interest expense	1,703	1,654	1,404	6,080	4,402	3,726	1,649	1,438					10,841	11,215	4,320	1,342
Gain from change in fair value of warrants	1,500	1,700	800	0	0	0	(157)	(1,256)					4,000	(1,413)	(9,300)	(6,170)
Loss on debt extinguishment and modifications	0	0	0	11,921	332	25	0	0					11,921	357	12	0
Other expense (income), net	(225)	(9)	2,142	453	146	62	92	59					2,361	359	144	(283)
Total other expense (income)	2,978	3,345	4,346	18,454	4,880	3,813	1,584	241					29,123	10,518	(4,824)	(5,111)
(Loss) income before income taxes	(6,450)	(9,053)	(7,612)	(24,054)	(7,878)	(10,509)	(10,792)	(6,680)					(47,169)	(35,859)	(12,593)	29,221
Income tax expense (benefit)	(320)	149	135	479	(1,238)	(1,792)	18,000	(3,357)					443	11,613	(9,702)	7,744
Net (loss) income	(6,130)	(9,202)	(7,747)	(24,533)	$ (6,640)	$ (8,717)	$ (28,792)	$ (3,323)	$ (32,280)	$ (32,115)	$ (41,482)	$ (40,832)	(47,612)	(47,472)	(2,891)	21,477
Deemed dividend on Series B preferred stock	(31,067)	(3,603)	(3,190)	0									(37,860)	0	0	0
Net (loss) income available to common stockholders	$ (37,197)	$ (12,805)	$ (10,937)	$ (24,533)									$ (85,472)	$ (47,472)	$ (2,891)	$ 21,477
Weighted-average common shares outstanding:
Basic (in shares)								10,819					13,787	10,931	10,808	10,705
Diluted (in shares)								10,819					13,787	10,931	10,991	11,131
(Loss) earnings per common share:
Basic (in dollars per share)								$ (0.42)					$ (6.20)	$ (4.34)	$ (0.27)	$ 2.01
Diluted (in dollars per share)								$ (0.42)					$ (6.20)	$ (4.47)	$ (1.11)	$ 1.38

Selected Quarterly Financial _5

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, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Jun. 30, 2017	Jun. 30, 2016	Sep. 30, 2017	Sep. 30, 2016	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Cash provided by (used in) operating activities
Net (loss) income	$ (6,130)	$ (9,202)	$ (7,747)	$ (24,533)	$ (6,640)	$ (8,717)	$ (28,792)	$ (3,323)	$ (32,280)	$ (32,115)	$ (41,482)	$ (40,832)	$ (47,612)	$ (47,472)	$ (2,891)	$ 21,477
Adjustments to reconcile net (loss) income to net cash provided by operating activities:
Amortization of intangible assets				1,209				1,429	2,419	2,857	3,628	4,286	4,838	5,716	5,287	2,108
Depreciation				1,172				1,118	2,342	2,250	3,502	3,412	4,634	4,582	4,030	2,520
Change in valuation of warrants				0				(1,256)	800	(1,413)	2,500	(1,413)	4,000	(1,413)	(9,300)	(6,170)
Stock compensation expense				(865)				441	(1,028)	692	(297)	1,188	473	1,619	1,501	1,487
Amortization of financing fees				3,109				143	3,441	445	3,778	1,451	4,117	3,048	443	87
Deferred income taxes				469				(1,628)	602	18,029	746	18,179	239	18,121	(9,058)	(1,624)
Loss on debt extinguishment and modifications				11,921				0	11,921	0	11,921	25	11,921	357	12	0
Asset impairment charges								345		1,410		1,447	1	1,614	11,686	310
Change in valuation of contingent consideration								0		(283)		(283)	0	(283)	(23)	(3,840)
Provision for doubtful accounts				48				(10)	131	24	216	69	67	80	288	70
Provision for inventory obsolescence				146				288	539	3,441	882	3,928	421	5,341	1,712	1,856
Loss (gain) on disposal of fixed assets				10				236	66	(852)	115	(846)	423	(663)	175	321
Other sources, net				135				113	198	205	189	266	13	413	681	612
Changes in operating assets and liabilities:
Trade accounts receivable, net				(4,017)				25,158	3,532	12,624	(691)	17,100	(8,391)	10,116	10,589	(30,682)
Inventory, net				3,122				22,288	(3,326)	42,947	(13,408)	46,390	13,366	55,564	(47,505)	(44,240)
Prepaid expenses and other assets				(1,624)				(207)	1,238	(1,261)	(1,359)	(2,443)	(2,284)	(12,893)	2,126	(3,224)
Trade accounts payable				15,186				(36,459)	3,244	(30,324)	1,879	(34,056)	(1,198)	(27,037)	5,913	37,647
Income taxes refundable (payable)				298				3,441	5,135	1,783	6,293	(682)	6,508	(1,783)	(7,673)	1,327
Accrued expenses				2,432				1,891	3,242	3,041	8,867	6,099	6,029	15,709	1,085	5,096
Other noncurrent liabilities				121				98	894	(1,011)	821	(1,028)	(5,260)	1,601	8,107	(232)
Net cash (used in) provided by operating activities				8,097				13,910	1,322	24,511	(13,542)	24,313	(7,695)	32,282	(22,815)	(15,094)
Cash flows from investing activities:
Capital expenditures				(1,896)				(1,099)	(2,669)	(1,977)	(3,856)	(3,286)	(5,061)	(3,872)	(8,409)	(8,214)
Proceeds from disposal of assets								0		2,466		2,466	0	2,466	0	0
Other sources, net				0				0	245	0	245	245	(104)	(245)	(1,169)	14
Net cash used in investing activities				(1,896)				(1,099)	(2,424)	489	(3,611)	(1,065)	(5,165)	(1,651)	(43,805)	(52,322)
Cash flows from financing activities
Proceeds from issuance of long-term debt				(71,400)				0	(71,400)	60,000	(71,400)	60,000
Financing fees				(253)				0	(928)	(3,402)	(928)	(3,402)	(928)	(5,802)	(1,517)	(154)
Net proceeds from stock offering and warrants				59,396				0	59,396	2,001	59,396	2,001	59,396	2,001	65	1,425
Proceeds from revolving line of credit				85,945				46,902	209,082	111,902	324,416	196,179	436,228	281,007	93,629	82,401
Repayments of revolving line of credit				(81,833)				(63,634)	(196,593)	(195,164)	(295,859)	(276,484)	(411,948)	(365,532)	(74,359)	(22,305)
Acquisition of businesses contingent consideration payments				(6)				(3,029)	(9)	(8,258)	(19)	(8,279)	(26)	(8,348)	0	0
Other uses, net				0				0	(738)	(89)	(745)	(98)	(754)	(110)	(351)	(430)
Net cash provided by (used in) financing activities				(8,151)				(19,761)	(1,190)	(33,010)	14,861	(30,083)	10,568	(36,784)	68,504	67,671
Decrease in cash				(1,950)				(6,950)	(2,292)	(8,010)	(2,292)	(6,835)	(2,292)	(6,153)	1,884	255
Cash at beginning of the year	$ 0	0	342	2,292	1,610	435	1,495	8,445	2,292	8,445	2,292	8,445	$ 2,292	8,445	6,561	6,306
Cash at end of the year		$ 0	$ 0	$ 342	$ 2,292	$ 1,610	$ 435	$ 1,495	$ 0	$ 435	$ 0	$ 1,610		$ 2,292	$ 8,445	$ 6,561

Selected Quarterly Financial _6

Selected Quarterly Financial Data (Unaudited) - Effect of Restatement Categories of Restatement (Details) - USD ($)	3 Months Ended								12 Months Ended
	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Error Corrections and Prior Period Adjustments Restatement [Line Items]
Net sales	$ 131,476,000	$ 99,953,000	$ 100,922,000	$ 84,265,000	$ 98,280,000	$ 78,944,000	$ 85,771,000	$ 76,470,000	$ 416,616,000	$ 339,465,000	$ 362,387,000	$ 347,580,000
(Loss) income before taxes	$ (6,450,000)	$ (9,053,000)	$ (7,612,000)	$ (24,054,000)	$ (7,878,000)	$ (10,509,000)	$ (10,792,000)	(6,680,000)	$ (47,169,000)	$ (35,859,000)	(12,593,000)	29,221,000
Restatement adjustments
Error Corrections and Prior Period Adjustments Restatement [Line Items]
Net sales								14,656,000			(27,059,000)	(415,000)
(Loss) income before taxes								2,251,000			(26,483,000)	(5,318,000)
Previously reported
Error Corrections and Prior Period Adjustments Restatement [Line Items]
Net sales								61,814,000			389,446,000	347,995,000
(Loss) income before taxes								(8,931,000)			13,890,000	34,539,000
Revenue recognition adjustments | Restatement adjustments
Error Corrections and Prior Period Adjustments Restatement [Line Items]
Net sales								14,656,000			(27,059,000)	(415,000)
(Loss) income before taxes								3,111,000			(9,215,000)	(2,700,000)
Product development cost | Restatement adjustments
Error Corrections and Prior Period Adjustments Restatement [Line Items]
Net sales								0			0
(Loss) income before taxes								123,000			(1,001,000)	(2,397,000)	$ (3,600,000)
Inventory valuation | Restatement adjustments
Error Corrections and Prior Period Adjustments Restatement [Line Items]
Net sales								0			0
(Loss) income before taxes								(404,000)			(1,069,000)	38,000	(1,500,000)
Impairment of long-lived assets | Restatement adjustments
Error Corrections and Prior Period Adjustments Restatement [Line Items]
Net sales								0			0
(Loss) income before taxes								(557,000)			(11,733,000)	(310,000)
Product warranty | Restatement adjustments
Error Corrections and Prior Period Adjustments Restatement [Line Items]
Net sales								0			0
(Loss) income before taxes								(319,000)			(2,484,000)	591,000
Accrued liabilities | Restatement adjustments
Error Corrections and Prior Period Adjustments Restatement [Line Items]
Net sales								0			0
(Loss) income before taxes								422,000			(1,106,000)	591,000	300,000
Equity investment | Restatement adjustments
Error Corrections and Prior Period Adjustments Restatement [Line Items]
Net sales								0			0	0
(Loss) income before taxes								$ (125,000)			$ 125,000	$ (286,000)	$ 300,000

Selected Quarterly Financial _7

Selected Quarterly Financial Data (Unaudited) - Effect of Restatement on Consolidated Statements of Operations (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended								6 Months Ended		9 Months Ended		12 Months Ended
	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Jun. 30, 2017	Jun. 30, 2016	Sep. 30, 2017	Sep. 30, 2016	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Error Corrections and Prior Period Adjustments Restatement [Line Items]
Net sales	$ 131,476	$ 99,953	$ 100,922	$ 84,265	$ 98,280	$ 78,944	$ 85,771	$ 76,470					$ 416,616	$ 339,465	$ 362,387	$ 347,580
Cost of sales	115,981	86,702	88,443	74,497	86,376	72,820	81,253	69,827					365,623	310,276	311,148	283,540
Gross profit	15,495	13,251	12,479	9,768	11,904	6,124	4,518	6,643					50,993	29,189	51,239	64,040
Operating expenses:
Research, development and engineering expenses	6,459	5,687	3,848	3,950	4,742	4,498	4,817	4,904					19,944	18,961	23,574	19,305
Selling, general and administrative expenses	11,297	12,062	10,688	10,209	8,563	6,855	6,699	6,405					44,256	28,522	28,837	23,142
Asset impairment charges	1	0	0	0	167	38	1,064	345					1	1,614	11,686	310
Amortization of intangible assets	1,210	1,210	1,209	1,209	1,430	1,429	1,429	1,428					4,838	5,716	4,582	1,013
Total operating expenses	18,967	18,959	15,745	15,368	14,902	12,820	13,726	13,082					69,039	54,530	68,656	39,930
Operating (loss) income	(3,472)	(5,708)	(3,266)	(5,600)	(2,998)	(6,696)	(9,208)	(6,439)					(18,046)	(25,341)	(17,417)	24,110
Other expense (income):
Interest expense	1,703	1,654	1,404	6,080	4,402	3,726	1,649	1,438					10,841	11,215	4,320	1,342
Gain from change in fair value of warrants	1,500	1,700	800	0	0	0	(157)	(1,256)					4,000	(1,413)	(9,300)	(6,170)
Other expense, net	(225)	(9)	2,142	453	146	62	92	59					2,361	359	144	(283)
Total other expense (income)	2,978	3,345	4,346	18,454	4,880	3,813	1,584	241					29,123	10,518	(4,824)	(5,111)
(Loss) income before income taxes	(6,450)	(9,053)	(7,612)	(24,054)	(7,878)	(10,509)	(10,792)	(6,680)					(47,169)	(35,859)	(12,593)	29,221
Income tax expense (benefit)	(320)	149	135	479	(1,238)	(1,792)	18,000	(3,357)					443	11,613	(9,702)	7,744
Net (loss) income	$ (6,130)	$ (9,202)	$ (7,747)	$ (24,533)	$ (6,640)	$ (8,717)	$ (28,792)	$ (3,323)	$ (32,280)	$ (32,115)	$ (41,482)	$ (40,832)	$ (47,612)	$ (47,472)	$ (2,891)	$ 21,477
Weighted-average common shares outstanding:
Basic (in shares)								10,819					13,787	10,931	10,808	10,705
Diluted (in shares)								10,819					13,787	10,931	10,991	11,131
(Loss) earnings per common share:
Basic (in dollars per share)								$ (0.42)					$ (6.20)	$ (4.34)	$ (0.27)	$ 2.01
Diluted (in dollars per share)								$ (0.42)					$ (6.20)	$ (4.47)	$ (1.11)	$ 1.38
Previously Reported
Error Corrections and Prior Period Adjustments Restatement [Line Items]
Net sales								$ 61,814							$ 389,446	$ 347,995
Cost of sales								57,758							326,612	280,950
Gross profit								4,056							62,834	67,045
Operating expenses:
Research, development and engineering expenses								5,250							21,681	16,900
Selling, general and administrative expenses								6,058							27,376	23,088
Asset impairment charges								0							0	0
Amortization of intangible assets								1,429							4,582	1,013
Total operating expenses								12,737							53,639	41,001
Operating (loss) income								(8,681)							9,195	26,044
Other expense (income):
Interest expense								1,421							4,327	1,331
Gain from change in fair value of warrants								(1,256)							(9,299)	(6,169)
Other expense, net								85							229	183
Total other expense (income)								250							(4,695)	(8,495)
(Loss) income before income taxes								(8,931)							13,890	34,539
Income tax expense (benefit)								(3,680)							(388)	10,813
Net (loss) income								$ (5,251)							$ 14,278	$ 23,726
Weighted-average common shares outstanding:
Basic (in shares)								10,819							10,808	10,707
Diluted (in shares)								10,819							11,074	11,132
(Loss) earnings per common share:
Basic (in dollars per share)								$ (0.49)							$ 1.32	$ 2.22
Diluted (in dollars per share)								$ (0.49)							$ 0.45	$ 2.13
Restatement Adjustments and Reclassifications
Error Corrections and Prior Period Adjustments Restatement [Line Items]
Net sales								$ 14,656							$ (27,059)	$ (415)
Cost of sales								12,069							(15,464)	2,590
Gross profit								2,587							(11,595)	(3,005)
Operating expenses:
Research, development and engineering expenses								(346)							1,893	2,405
Selling, general and administrative expenses								347							1,461	54
Asset impairment charges								345							11,686	310
Amortization of intangible assets								(1)							0	0
Total operating expenses								345							15,017	(1,071)
Operating (loss) income								2,242							(26,612)	(1,934)
Other expense (income):
Interest expense								17							(7)	11
Gain from change in fair value of warrants								0							(1)	(1)
Other expense, net								(26)							(85)	(466)
Total other expense (income)								(9)							(129)	3,384
(Loss) income before income taxes								2,251							(26,483)	(5,318)
Income tax expense (benefit)								323							(9,314)	(3,069)
Net (loss) income								$ 1,928							$ (17,169)	$ (2,249)
Weighted-average common shares outstanding:
Basic (in shares)								0							0	(2)
Diluted (in shares)								0							(83)	(1)
(Loss) earnings per common share:
Basic (in dollars per share)								$ 0.07							$ (1.59)	$ (0.21)
Diluted (in dollars per share)								$ 0.07							$ (1.56)	$ (0.75)

Selected Quarterly Financial _8

Selected Quarterly Financial Data (Unaudited) - Effect of Restatement on Consolidated Balance Sheets (Details) - USD ($) $ in Thousands	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Current assets:
Cash and cash equivalents	$ 0	$ 0	$ 0	$ 342	$ 2,292	$ 1,610	$ 435	$ 1,495	$ 8,445	$ 6,561	$ 6,306
Accounts receivable, net	68,660	60,811	56,673	64,305	60,336	53,364	57,884	45,384	70,532	76,266
Income tax receivable	1,018	841	1,996	6,829	7,127	5,737	3,384	1,723	5,265	0
Inventories, net	86,724	113,074	103,335	97,286	100,548	111,133	115,062	139,519	162,095	106,250
Prepaid expenses and other current assets	14,359	14,536	12,453	15,291	13,644	5,146	4,026	4,132	2,703	4,840
Total current assets	170,761	189,262	174,457	184,053	183,947	176,990	180,791	192,253	249,040	202,469
Property, plant and equipment, net	18,960	18,974	19,050	19,230	20,127	20,257	20,386	20,662	22,809	17,954
Intangible assets, net	21,491	22,401	23,610	24,819	26,029	27,459	28,888	30,316	31,745	21,192
Goodwill	29,835	29,835	29,835	29,835	29,835	29,835	29,835	29,835	29,835	23,414	0
Deferred income taxes	0				0	0	0	19,285	17,657	13
Other noncurrent assets	5,972	6,035	4,518	5,053	4,681	2,821	2,621	2,664	2,751	1,903
TOTAL ASSETS	247,019	266,507	251,470	262,990	264,619	257,362	262,521	295,015	353,837	266,945
Current liabilities:
Accounts payable	51,225	54,195	55,610	67,167	53,588	45,764	49,729	43,160	79,823	67,713
Contingent consideration	12	20	29	30	26	88	100	5,481	8,275	0
Other accrued liabilities	38,362	41,393	35,379	35,234	32,507	22,405	19,182	17,929	17,846	18,182
Total current liabilities	126,654	136,940	116,281	119,318	99,645	85,626	83,049	66,570	105,944	87,562
Long-term obligations
Revolving line of credit	0				0	0	0	80,568	97,299	78,030
Warrants	24,700	23,200	21,500	20,700	0	0	0	226	1,482	11,036
Long-term debt, less current maturities, net	54,439	54,305	54,168	54,045	110,392	111,517	110,929	53,799	53,805	2,361
Other noncurrent liabilities	8,351	13,312	12,438	13,328	13,458	12,730	12,833	11,952	10,434	1,473
TOTAL LIABILITIES	214,847	228,967	205,453	208,324	223,959	210,395	207,184	213,115	268,964	180,462
STOCKHOLDERS’ EQUITY
Preferred stock	0	0	0	0	0	0	0	0	0	0
Common stock - $0.001 par value. Authorized: 50,000,000 shares. Issued and Outstanding: 11,583,831 and 11,562,209 shares, at December 31, 2015 and 2014	19	14	14	14	12	12	12	11	11	11
Additional paid-in capital	123,838	91,737	96,543	100,686	86,764	86,408	86,043	83,729	83,377	81,746
Retained earnings	(82,147)	(76,018)	(66,817)	(59,070)	(34,535)	(27,895)	(19,180)	9,612	12,937	15,828
Treasury stock, at cost	(9,538)	(9,604)	(11,530)	(11,582)	(11,581)	(11,558)	(11,537)	(11,452)	(11,452)	(11,102)
TOTAL STOCKHOLDERS’ EQUITY	32,172	6,129	18,210	30,048	40,660	46,967	55,337	81,900	84,873	86,483	47,607
TOTAL LIABILITIES AND STOCKHOLDERS’ EQUITY	$ 247,019	$ 266,507	$ 251,470	$ 262,990	$ 264,619	$ 257,362	$ 262,521	295,015	353,837	266,945
Previously Reported
Current assets:
Cash and cash equivalents								1,495	8,445	6,561
Accounts receivable, net								63,163	104,365	81,740
Income tax receivable								0	5,230
Inventories, net								120,735	130,347	93,903
Prepaid expenses and other current assets								9,496	4,288	4,801
Total current assets								194,889	252,675	191,003
Property, plant and equipment, net								24,289	26,001	20,892
Intangible assets, net								30,316	31,745	21,392
Goodwill								41,466	41,466	23,546
Deferred income taxes								819	819	0
Other noncurrent assets								7,181	7,230	5,804
TOTAL ASSETS								298,960	359,936	262,637
Current liabilities:
Accounts payable								41,491	76,078	60,877
Contingent consideration								0	8,788
Other accrued liabilities								19,692	14,396	13,504
Total current liabilities								61,183	99,262	76,048
Long-term obligations
Revolving line of credit								80,568	97,299	78,030
Warrants								226	1,482	11,036
Long-term debt, less current maturities, net								53,946	53,820	2,361
Other noncurrent liabilities								1,670	1,776	1,122
TOTAL LIABILITIES								197,593	253,639	171,838
STOCKHOLDERS’ EQUITY
Preferred stock								0	0	0
Common stock - $0.001 par value. Authorized: 50,000,000 shares. Issued and Outstanding: 11,583,831 and 11,562,209 shares, at December 31, 2015 and 2014								12	12	12
Additional paid-in capital								75,500	75,179	73,959
Retained earnings								30,105	35,356	21,078
Treasury stock, at cost								(4,250)	(4,250)	(4,250)
TOTAL STOCKHOLDERS’ EQUITY								101,367	106,297	90,799	50,421
TOTAL LIABILITIES AND STOCKHOLDERS’ EQUITY								298,960	359,936	262,637
Restatement Adjustments and Reclassifications
Current assets:
Cash and cash equivalents								0	0	0
Accounts receivable, net								(17,779)	(33,833)	(5,474)
Income tax receivable								1,723	35
Inventories, net								18,784	31,748	12,347
Prepaid expenses and other current assets								(5,364)	(1,585)	39
Total current assets								(2,636)	(3,635)	11,466
Property, plant and equipment, net								(3,627)	(3,192)	(2,938)
Intangible assets, net								0	0	(200)
Goodwill								(11,631)	(11,631)	(132)
Deferred income taxes								18,466	16,838	13
Other noncurrent assets								(4,517)	(4,479)	(3,901)
TOTAL ASSETS								(3,945)	(6,099)	4,308
Current liabilities:
Accounts payable								1,669	3,745	6,836
Contingent consideration								5,481	(513)
Other accrued liabilities								(1,763)	3,450	4,678
Total current liabilities								5,387	6,682	11,514
Long-term obligations
Revolving line of credit								0	0	0
Warrants								0	0	0
Long-term debt, less current maturities, net								(147)	(15)	0
Other noncurrent liabilities								10,282	8,658	351
TOTAL LIABILITIES								15,522	15,325	8,624
STOCKHOLDERS’ EQUITY
Preferred stock								0	0	0
Common stock - $0.001 par value. Authorized: 50,000,000 shares. Issued and Outstanding: 11,583,831 and 11,562,209 shares, at December 31, 2015 and 2014								(1)	(1)	(1)
Additional paid-in capital								8,229	8,198	7,787
Retained earnings								(20,493)	(22,419)	(5,250)
Treasury stock, at cost								(7,202)	(7,202)	(6,852)
TOTAL STOCKHOLDERS’ EQUITY								(19,467)	(21,424)	(4,316)	$ (2,891)
TOTAL LIABILITIES AND STOCKHOLDERS’ EQUITY								$ (3,945)	$ (6,099)	$ 4,308

Selected Quarterly Financial _9

Selected Quarterly Financial Data (Unaudited) - Effect of Restatement on Consolidated Statement of Cash Flow (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended		9 Months Ended		12 Months Ended
	Mar. 31, 2017	Mar. 31, 2016	Jun. 30, 2017	Jun. 30, 2016	Sep. 30, 2017	Sep. 30, 2016	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Error Corrections and Prior Period Adjustments Restatement [Line Items]
Accrued expenses	$ 2,432	$ 1,891	$ 3,242	$ 3,041	$ 8,867	$ 6,099	$ 6,029	$ 15,709	$ 1,085	$ 5,096
Prepaid expenses and other assets	(1,624)	(207)	1,238	(1,261)	(1,359)	(2,443)	(2,284)	(12,893)	2,126	(3,224)
Net cash provided by operating activities	8,097	13,910	1,322	24,511	(13,542)	24,313	(7,695)	32,282	(22,815)	(15,094)
Net cash used in investing activities	(1,896)	(1,099)	(2,424)	489	(3,611)	(1,065)	(5,165)	(1,651)	(43,805)	(52,322)
Net cash used in financing activities	(8,151)	(19,761)	(1,190)	(33,010)	14,861	(30,083)	10,568	(36,784)	68,504	67,671
Decrease in cash		(6,950)
Cash at beginning of the year	2,292	8,445	2,292	8,445	2,292	8,445	2,292	8,445	6,561	6,306
Cash at end of the year	342	1,495	0	435	0	1,610		2,292	8,445	6,561
Other noncurrent liabilities	$ 121	98	$ 894	(1,011)	$ 821	(1,028)	$ (5,260)	1,601	8,107	(232)
Previously Reported
Error Corrections and Prior Period Adjustments Restatement [Line Items]
Net cash provided by operating activities		9,995							(23,049)	(15,685)
Net cash used in investing activities		(214)							(43,570)	(51,713)
Net cash used in financing activities		(16,731)							68,503	67,653
Decrease in cash		(6,950)
Cash at beginning of the year		8,445		8,445		8,445		8,445	6,561	6,306
Cash at end of the year		1,495							8,445	$ 6,561
Restatement Adjustments and Reclassifications
Error Corrections and Prior Period Adjustments Restatement [Line Items]
Net cash provided by operating activities		3,915
Net cash used in investing activities		(885)
Net cash used in financing activities		(3,030)
Decrease in cash		0
Cash at beginning of the year		0		$ 0		$ 0		$ 0
Cash at end of the year		$ 0							$ 0

Subsequent Events (Details)

Subsequent Events (Details) $ in Millions	Apr. 02, 2018USD ($)
Subsequent Event | Asset Purchase Agreement, Chicago Technical Center Research and Development Facility
Subsequent Event [Line Items]
Purchase price	$ 5.6