Arq (ARQ) 10-K 12 Mar 18 2017 FY Annual report Financial data

Document and Entity Information

Document and Entity Information - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Mar. 02, 2018	Jun. 30, 2017
Document Documentand Entity Information [Abstract]
Document Type	10-K
Amendment Flag	false
Document Period End Date	Dec. 31, 2017
Document Fiscal Year Focus	2,017
Document Fiscal Period Focus	FY
Entity Registrant Name	Advanced Emissions Solutions, Inc.
Entity Central Index Key	1,515,156
Current Fiscal Year End Date	--12-31
Entity Well-known Seasoned Issuer	No
Entity Current Reporting Status	No
Entity Voluntary Filers	Yes
Entity Filer Category	Accelerated Filer
Entity Common Stock, Shares Outstanding		20,752,939
Entity Public Float			$ 114.3

Consolidated Balance Sheets

Consolidated Balance Sheets - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
ASSETS
Cash and cash equivalents	$ 30,693	$ 13,208
Restricted cash	0	13,736
Receivables, net	1,113	8,648
Receivables, related party	3,247	1,934
Prepaid expenses and other assets	1,835	1,382
Total current assets	36,888	38,908
Property and equipment, net of accumulated depreciation of $1,486 and $2,920, respectively	410	735
Equity method investments	4,351	3,959
Deferred tax assets	38,661	61,396
Other assets	2,308	2,298
Total Assets	82,618	107,296
LIABILITIES AND STOCKHOLDERS’ EQUITY
Accounts payable	1,000	1,920
Accrued payroll and related liabilities	1,384	2,121
Billings in excess of costs on uncompleted contracts	1,830	4,947
Legal settlements and accruals	0	10,706
Other current liabilities	2,664	4,017
Total current liabilities	6,878	23,711
Legal settlements and accruals, long-term	0	5,382
Other long-term liabilities	2,285	2,038
Total Liabilities	9,163	31,131
Commitments and contingencies (Notes 3 and 4)
Stockholders’ equity:
Preferred stock: par value of $.001 per share, 50,000,000 shares authorized, none outstanding	0	0
Common stock: par value of $.001 per share, 100,000,000 shares authorized, 22,465,821 and 22,322,022 shares issued and 20,752,055 and 22,024,675 shares outstanding at December 31, 2017 and 2016, respectively	22	22
Treasury stock, at cost: 1,713,766 and zero shares as of December 31, 2017 and 2016, respectively	(16,397)	0
Additional paid-in capital	105,308	119,494
Accumulated deficit	(15,478)	(43,351)
Total stockholders’ equity	73,455	76,165
Total Liabilities and Stockholders’ Equity	$ 82,618	$ 107,296

Consolidated Balance Sheets (Pa

Consolidated Balance Sheets (Parenthetical) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Statement of Financial Position [Abstract]
Accumulated depreciation and amortization	$ 1,486	$ 2,920
Preferred stock par value (in dollars per share)	$ 0.001	$ 0.001
Preferred stock, shares authorized (in shares)	50,000,000	50,000,000
Preferred stock, shares outstanding (in shares)	0	0
Common stock par value (in dollars per share)	$ 0.001	$ 0.001
Common stock, shares authorized (in shares)	100,000,000	100,000,000
Common stock, shares issued (in shares)	22,465,821	22,322,022
Common stock, shares outstanding (in shares)	20,752,055	22,024,675
Treasury Stock (in shares)	1,713,766	0

Consolidated Statements of Oper

Consolidated Statements of Operations - USD ($) shares in Thousands, $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Revenues:
Equipment sales	$ 31,401	$ 46,949	$ 60,099
Chemicals	4,246	3,025	888
Consulting services and other	45	648	1,752
Total revenues	35,692	50,622	62,739
Operating expenses:
Equipment sales cost of revenue, exclusive of depreciation and amortization	28,438	37,741	45,433
Chemicals cost of revenue, exclusive of depreciation and amortization	3,434	1,700	601
Consulting services and other cost of revenue, exclusive of depreciation and amortization	13	376	1,518
Payroll and benefits	7,669	12,390	23,589
Rent and occupancy	795	2,168	3,309
Legal and professional fees	4,354	8,293	16,604
General and administrative	3,857	3,721	6,104
Research and development, net	157	(648)	5,362
Depreciation and amortization	789	979	2,019
Total operating expenses	49,506	66,720	104,539
Operating loss	(13,814)	(16,098)	(41,800)
Other income (expense):
Earnings from equity method investments	53,843	45,584	8,921
Royalties, related party	9,672	6,125	10,642
Interest income	54	268	24
Interest expense	(3,024)	(5,066)	(8,402)
Litigation settlement and royalty indemnity expense, net	3,269	3,464	0
Other	2,025	2,463	494
Total other income	65,839	52,838	11,679
Income (loss) before income tax expense	52,025	36,740	(30,121)
Income tax expense (benefit)	24,152	(60,938)	20
Net income (loss)	$ 27,873	$ 97,678	$ (30,141)
Earnings (loss) per common share:
Basic (in dollars per share)	$ 1.30	$ 4.40	$ (1.37)
Diluted (in dollars per share)	$ 1.29	$ 4.34	$ (1.37)
Weighted-average number of common shares outstanding:
Basic (in shares)	21,367	21,931	21,773
Diluted (in shares)	21,413	22,234	21,773
Cash dividends declared per common share outstanding (in dollars per share)	$ 0.75	$ 0	$ 0

Consolidated Statements of Chan

Consolidated Statements of Changes in Stockholders’ Equity (Deficit) - USD ($) $ in Thousands	Total	Common Stock	Treasury Stock	Additional Paid-in Capital	Accumulated Deficit
Beginning Balances (in shares) at Dec. 31, 2014		21,853,263
Beginning Balances at Dec. 31, 2014	$ (697)	$ 22		$ 110,169	$ (110,888)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Stock-based compensation (in shares)		127,867
Stock-based compensation	6,462			6,462
Clawback of equity awards (in shares)		(20,656)
Clawback of equity awards	(325)			(325)
Repurchase of shares to satisfy tax withholdings (in shares)		(16,602)
Repurchase of shares to satisfy tax withholdings	(277)			(277)
Net income (loss)	(30,141)				(30,141)
Ending Balances (in shares) at Dec. 31, 2015		21,943,872
Ending Balances at Dec. 31, 2015	(24,978)	$ 22		116,029	(141,029)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Stock-based compensation (in shares)		405,354
Stock-based compensation	2,762			2,762
Repurchase of shares to satisfy tax withholdings (in shares)		(27,204)
Repurchase of shares to satisfy tax withholdings	(196)			(196)
Reclassification and settlement of equity awards	899			899
Net income (loss)	97,678				97,678
Ending Balances (in shares) at Dec. 31, 2016		22,322,022
Ending Balances at Dec. 31, 2016	76,165	$ 22		119,494	(43,351)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Stock-based compensation (in shares)		199,734
Stock-based compensation	2,209			2,209
Repurchase of shares to satisfy tax withholdings (in shares)		(55,935)
Repurchase of shares to satisfy tax withholdings	(566)			(566)
Dividends declared on common stock	(15,829)			(15,829)
Repurchase of common shares (in hares)			(1,713,766)
Repurchase of common shares	(16,397)		$ (16,397)
Net income (loss)	27,873				27,873
Ending Balances (in shares) at Dec. 31, 2017		22,465,821	(1,713,766)
Ending Balances at Dec. 31, 2017	$ 73,455	$ 22	$ (16,397)	$ 105,308	$ (15,478)

Consolidated Statements of Cash

Consolidated Statements of Cash Flows $ in Thousands	12 Months Ended
	Dec. 31, 2017USD ($)	Dec. 31, 2016USD ($)	Dec. 31, 2015USD ($)
Cash flows from operating activities
Net income (loss)	$ 27,873	$ 97,678	$ (30,141)
Adjustments to reconcile net income (loss) to net cash used in operating activities:
Deferred tax benefit from release of valuation allowance	(474)	(61,396)	0
Depreciation and amortization	789	979	2,019
Debt prepayment penalty and amortization of debt issuance costs	109	1,380	987
Impairment of property, equipment, inventory, intangibles and cost method investment	464	2,280	2,087
Provision for accounts receivable and other receivables	385	13	633
Interest costs added to principal balance of notes payable	0	0	923
Share-based compensation expense, net	2,209	2,868	6,879
Earnings from equity method investments	(53,843)	(45,584)	(8,921)
Gain on sale of equity method investment	0	(2,078)	0
Gain on settlement of note payable, licensed technology, and sales-type lease	0	(1,910)	0
Other non-cash items, net	44	35	285
Changes in operating assets and liabilities, net of effects of acquired businesses:
Receivables	6,743	(301)	8,361
Related party receivables	(1,313)	(16)	(479)
Prepaid expenses and other assets	(351)	1,195	(107)
Costs incurred on uncompleted contracts	27,048	29,623	6,492
Deferred tax asset, net	23,208	0	0
Other long-term assets	41	961	205
Accounts payable	(920)	(4,254)	(1,340)
Accrued payroll and related liabilities	(738)	(2,887)	(102)
Other current liabilities	(1,586)	(3,105)	(812)
Billings on uncompleted contracts	(30,140)	(32,272)	(15,186)
Advance deposit, related party	0	(2,980)	(3,544)
Other long-term liabilities	154	(2,175)	595
Legal settlements and accruals	(16,088)	(4,211)	(3,722)
Distributions from equity method investees, return on investment	4,638	7,900	5,019
Net cash used in operating activities	(11,748)	(18,257)	(29,869)
Cash flows from investing activities
Distributions from equity method investees in excess of cumulative earnings	48,875	38,250	8,651
Maturity of investment securities, restricted	0	336	0
Acquisition of property and equipment	(485)	(289)	(507)
Proceeds from sale of property and equipment	57	52	942
Advance on note receivable	0	0	(500)
Acquisition of business	0	0	(2,124)
Purchase of and contributions to equity method investee	(61)	(223)	(2,128)
Proceeds from sale of equity method investment	0	1,773	0
Net cash provided by investing activities	48,386	39,899	4,334
Cash flows from financing activities
Borrowings on Line of Credit	808	0	0
Repayments on Line of Credit	(808)	0	0
Short-term borrowings	0	0	13,539
Repayments on short-term borrowings and notes payable, related party	0	(14,496)	(3,234)
Short-term borrowing loan costs and debt prepayment penalty	(236)	(979)	0
Repurchase of shares to satisfy tax withholdings	(566)	(196)	(276)
Dividends paid	(15,690)	0	0
Repurchase of common shares	(16,397)	0	0
Net cash (used in) provided by financing activities	(32,889)	(15,671)	10,029
Increase (Decrease) in Cash and Cash Equivalents and Restricted Cash	3,749	5,971	(15,506)
Cash and Cash Equivalents and Restricted Cash, beginning of year	26,944	20,973	36,479
Cash and Cash Equivalents and Restricted Cash, end of year	30,693	26,944	20,973
Supplemental disclosure of cash flow information:
Cash paid for interest	3,644	3,647	6,274
Cash paid for income taxes, net of refunds received	1,672	541	29
Supplemental disclosure of non-cash investing and financing activities:
Settlement of RCM6 note payable	0	13,234	0
Non-cash reduction of equity method investment	0	11,156	0
Stock award reclassification (liability to equity)	0	899	0
Dividends payable	$ 139	$ 0	$ 0

Summary of Operations and Signi

Summary of Operations and Significant Accounting Policies	12 Months Ended
	Dec. 31, 2017
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Summary of Operations and Significant Accounting Policies	Summary of Operations and Significant Accounting Policies Nature of Operations Advanced Emissions Solutions, Inc. ("ADES" or the "Company") is a Delaware corporation with its principal office located in Highlands Ranch, Colorado. The Company is principally engaged in emissions control ("EC") technologies and associated equipment, consumables and services. Our proprietary environmental technologies enable customers to reduce emissions of mercury and other pollutants, maximize utilization levels and improve operating efficiencies to meet the challenges of existing and pending EC regulations. The Company generates substantial earnings and tax credits under Section 45 ("Section 45 tax credits") of the Internal Revenue Code ("IRC") from its equity investments in certain entities and royalty payment streams related to technologies that are licensed to Tinuum Group, LLC, a Colorado limited liability company ("Tinuum Group"). Such technologies allow Tinuum Group to provide their customers with various solutions to enhance combustion and reduced emissions of nitrogen oxide ("NO x ") and mercury from coal burned to generate electrical power. The Company’s sales occur principally throughout the United States. See Note 13 for additional information regarding the Company's operating segments. Principles of Consolidation The Consolidated Financial Statements include accounts of wholly-owned subsidiaries. All significant intercompany balances and transactions have been eliminated in consolidation. All investments in partially owned entities for which the Company has greater-than-20% ownership are accounted for using the equity method based on the legal form of the Company's ownership percentage and the applicable ownership percentage of the entity and are included in the Equity method investments line item in the Consolidated Balance Sheets . As of December 31, 2017 , the Company holds equity interests of 42.5% , 50.0% and 50.0% in Tinuum Group, Tinuum Services, LLC ("Tinuum Services") and GWN Manager, LLC ("GWN Manager"), respectively. As discussed in Note 2 , the Company purchased its interest in GWN Manager in July 2017 and sold its equity method investment in RCM6, LLC ("RCM6") in March 2016. Tinuum Group is deemed to be variable interest entity ("VIE") under the VIE model of consolidation, but the Company does not consolidate Tinuum Group as it is not deemed to be its primary beneficiary. Cash and Cash Equivalents Cash and cash equivalents include bank deposits and other highly liquid investments purchased with an original maturity of three months or less. Restricted Cash As of December 31, 2017 , all cash and cash equivalents were unrestricted and all cash requirements for contractual performance guarantees and payments were satisfied under the borrowing availability of the 2013 Loan and Security Agreement ("Line of Credit"). As of December 31, 2016 , restricted cash primarily consisted of funds withheld to provide collateral support for certain letters of credit issued to i) customers related to certain contractual performance and payment guarantees, ii) certain settlement parties to provide security for continuing royalty indemnification payments related to the settlement of certain litigation (the "Royalty Award"), and iii) minimum cash balance requirements under the Line of Credit. Receivables and Credit Policies Receivable balances represent unsecured, customer obligations due under trade terms typically requiring payment within 30 - 45 days from the invoice date and are stated net of allowance for doubtful accounts. The Company records allowances for doubtful accounts when it is probable that the accounts receivable balances will not be collected. The following tables show the receivables balances: As of December 31, (in thousands) 2017 2016 Trade receivables $ 1,240 $ 4,289 Less: Allowance for doubtful accounts (127 ) (200 ) Trade receivables, net 1,113 4,089 Other receivables (1) — 4,559 Total $ 1,113 $ 8,648 (1) As of December 31, 2016 , Other receivables included settlement amounts subsequently funded by the Company's insurance carriers for legal proceedings described in Note 4 . During the years ended December 31, 2017 , 2016 and 2015 , the Company recognized zero , zero and $0.1 million , respectively, of bad debt expense related to the write-off of specific accounts whose ultimate collection was in doubt. Bad debt expense is included within the General and administrative line item in the Consolidated Statements of Operations . Notes receivable are reported at their outstanding principal balances, adjusted for any amounts determined to be uncollectible. As of December 31, 2017 and 2016 , the Company had a Note Receivable outstanding in the amount of $1.0 million , which is fully reserved as substantial doubt exists as to collectability. Interest income is accrued and credited to income based on the unpaid principal balance outstanding. The accrual of interest is discontinued when substantial doubt exists about the ability to collect principal and interest based upon the contractual terms. Current portion of notes receivable is included within Prepaid expenses and other assets and long-term portion is included in the Other assets line item in the Consolidated Balance Sheets . Additional details regarding Note receivable balances are included in Note 10 . Inventory Inventories are stated at the lower of cost or market and consist principally of finished goods related to the Company's chemical product offerings. The cost of inventory is determined using the first-in-first-out ("FIFO") method. Inventories are included within the Other assets line item in the Consolidated Balance Sheets . As of December 31, 2017 and 2016 , the balance of inventory was comprised of finished goods of $0.1 million and zero , respectively. Other Intangible Assets Other Intangible assets consist of patents and licensed technology and are included in the Other assets line item in the Consolidated Balance Sheets . The Company has developed technologies resulting in patents being granted by the U.S. Patent and Trademark Office. Legal costs associated with securing the patent are capitalized and amortized over the legal or useful life beginning on the patent filing date. The weighted-average amortization period for the Company's patents is 16 years. All research and development costs associated with the technology development are expensed as incurred. Investments The investments in entities in which the Company does not have a controlling interest (financial or operating), but where it has the ability to exercise significant influence over operating and financial policies, are accounted for using the equity method of accounting. Whether or not the Company exercises significant influence with respect to an investee depends on an evaluation of several factors including, among others, representation on the investee company’s board of directors and the Company's ownership level. Under the equity method of accounting, an investee company’s accounts are not reflected within the Company’s Consolidated Balance Sheets and Consolidated Statements of Operations ; however, the Company’s share of the earnings or losses of the investee company is reported in the Earnings from equity method investments line item in the Consolidated Statements of Operations , and the Company’s carrying value in an equity method investee company is reported in the Equity method investments line in the Consolidated Balance Sheets . When the Company receives distributions in excess of the carrying value of the investment and has not guaranteed any obligations of the investee, nor is it required to provide additional funding to the investee, the Company recognizes such excess distributions as equity method earnings in the period the distributions occur. When the investee subsequently reports income, the Company does not record its share of such income until it equals the amount of distributions in excess of carrying value that were previously recognized in income. During the years ended December 31, 2017 , 2016 and 2015 , the Company had no guarantees or requirements to provide additional funding to investees. Additionally, when the Company's carrying value in an equity method investment is zero and the Company has not guaranteed any obligations of the investee, nor is it required to provide additional funding to the investee, the Company will not recognize its share of any reported losses by the investee until future earnings are generated to offset previously unrecognized losses. As a result, equity income or loss reported on the Company's Consolidated Statements of Operations for certain equity method investees may differ from a mathematical calculation of net income or loss attributable to its equity interest based upon the percentage ownership of the Company's equity interest and the net income or loss attributable to equity owners as shown on investee company's statements of operations. Likewise, distributions from equity method investees are reported on the Consolidated Statements of Cash Flows as “return on investment” within Operating cash flows until such time as the carrying value in an equity method investee company is reduced to zero; thereafter, such distributions are reported as “distributions in excess of cumulative earnings” within Investing cash flows. See Note 2 for additional information regarding the Company's equity method investments. Investments in partially-owned subsidiaries for which the Company has less-than-20% ownership are accounted for using the cost method. Cost method investments are evaluated for impairment upon an indicator of impairment such as an event or change in circumstances that may have a significant adverse effect on the fair value of the investment. If no such events or changes in circumstances have occurred, the fair value is estimated only if practicable to do so. Royalties, Related Party The Company licenses its M-45 TM and M-45-PC TM emission control technologies ("M-45 License") to Tinuum Group and realizes royalty income based upon a percentage of the per-ton, pre-tax margin as defined in the M-45 License. Property and Equipment Property and equipment is stated at cost less accumulated depreciation and includes leasehold improvements. Depreciation on assets is computed using the straight-line method over the lesser of the estimated useful lives of the related assets or the lease term (ranging from 2 to 7 years). Maintenance and repairs that do not extend the useful life of the respective asset are charged to Operating expenses as incurred. When assets are retired, or otherwise disposed of, the property accounts are relieved of costs and accumulated depreciation and any resulting gain or loss is credited or charged to income. The Company performs an evaluation of the recoverability of the carrying value of its long-lived assets to determine if facts and circumstances indicate that the carrying value of assets may be impaired and if any adjustment is warranted. Revenue Recognition The Company recognizes revenues when: (i) persuasive evidence of a customer arrangement exists; (ii) the price is fixed or determinable; (iii) collectability is reasonable assured; and (iv) product delivery has occurred or services have been rendered and it is probable that performance guarantees, if any, will be met. Equipment sales The Company has entered into construction-type contracts that entail the design and construction of emissions control systems ("extended equipment contracts"). Revenues from such extended equipment contracts are recorded using the percentage of completion cost to cost method based on costs incurred to date compared with total estimated contract costs. However, if the Company does not have sufficient information to estimate either costs incurred or total estimated costs for extended equipment contracts at the time contracts are entered into, the completed contract method is used. For all of its Dry Sorbent Injection ("DSI") contracts, the Company has used the completed contract method from inception of the contract to recognize revenues and related cost of revenue. Under the completed contract method, revenues and costs from extended equipment contracts are deferred and recognized when contract obligations are substantially complete. The Company defines substantially complete as delivery of equipment and start-up at the customer site or, as applicable to DSI systems, the completion of any major warranty service period. For each of the years ended December 31, 2017 , 2016 and 2015 , the Company did not have sufficient information to measure ongoing performance for its extended equipment contracts. Accordingly, the completed contract method of revenue recognition has been used for each of these years, and revenues and costs are deferred until the equipment is placed into service and contract obligations are substantially complete. For the years ended December 31, 2017 and 2016 , the Company did not enter into any extended equipment contracts. Deferred revenue and related costs are accumulated in the Costs in excess of billings on uncompleted contracts or Billings in excess of costs on uncompleted contracts line items in the Consolidated Balance Sheets , and typically include direct materials, direct labor and subcontractor costs, and indirect costs related to contract performance, such as indirect labor, supplies, tools and repairs. When multiple contracts exist with a single counterparty, the Company evaluates revenue recognition on a contract-by-contract basis. Provisions for estimated losses on uncompleted contracts are recognized when it has been determined that a loss is probable. The Company also enters into other non-extended equipment contracts for which the Company recognizes revenues as services to build equipment systems are performed or as equipment is delivered. Chemicals Revenues for direct sales of chemicals are recognized at the date of delivery to, and acceptance by, the customer. Certain chemicals customer contracts are comprised of evaluation tests of the Company's chemicals' effectiveness and efficiency in reducing emissions and entail the delivery of chemicals to the customer and the Company evaluating results of emissions reduction over the term of the contract. The Company generally recognizes revenue from these types of contracts over the duration of the contract based on the cost of chemicals consumed by the customer. Consulting services and other The Company recognizes revenues on time and material contracts as services are performed. Cost of Revenue Costs of revenue include all labor, fringe benefits, subcontract labor, chemical and coal costs, materials, equipment, supplies, travel costs and any other costs and expenses directly related to the Company’s production of revenues. The Company records estimated contract losses, if any, in the period they are determined. Warranty costs for Activated Carbon Injection ("ACI") equipment systems are estimated based on historical experience and are recorded as a percentage of revenue when the equipment is substantially complete. Warranty costs, comprised of the cost of replacement materials and direct labor, are included within the Equipment sales cost of revenue line in the Consolidated Statements of Operations . Warranty costs for DSI equipment systems have not been estimable at the time the contracts were entered into, as the Company lacked historical experience in manufacturing DSI systems and was unable to reasonably estimate costs to complete as well as warranty claims. Therefore, revenue recognition on DSI equipment systems has been deferred until the end of the warranty period, which has generally been 12 to 24 months following substantial completion. As warranty claims are incurred, such costs are deferred within the Costs in excess of billings on uncompleted contracts line item in the Consolidated Balance Sheets , until such time that revenues and cost of revenue are recognized. Subsequent to revenues being recognized, warranty claims are included within the Other long-term liabilities line item in the Consolidated Balance Sheets and within Cost of revenue line of the Consolidated Statements of Operations . The changes in the carrying amount of the Company’s warranty obligations, which do not include amounts for DSI systems as revenues, are deferred until the end of the warranty period, and are disclosed in Note 10 . Payroll and Benefits Payroll and benefits costs include direct payroll, personnel related fringe benefits, sales and administrative staff labor costs and stock compensation expense. Payroll and benefits costs exclude direct labor included in Cost of revenue. Rent and Occupancy Rent and occupancy costs include rent, insurance and other occupancy-related expenses. Legal and Professional Legal and professional costs include external legal, audit and consulting expenses. General and Administrative General and administrative costs include director fees and expenses, bad debt expense, impairments and other general costs of conducting business. Research and Development Costs Research and development costs are charged to expense in the period incurred. Research and development expense consists of research relating to continued product development for the Company's ongoing business and various other projects including the CO 2 capture and control market. The Company historically entered into development and cost-sharing contracts with the U.S. Department of Energy (the "DOE"). These contracts were best-effort-basis contracts, and the Company generally included industry cost-share partners to offset the costs incurred that are anticipated to be in excess of funded amounts from the DOE. The Company accounts for these contracts with the DOE and industry cost-share partners by recognizing amounts funded by the DOE under research-and-development-cost-sharing arrangements as an offset to research and development expense, which is reported in the Research and development, net line in the Consolidated Statements of Operations . Asset Retirement Obligations Asset retirement obligations, or "ARO liabilities," consist of estimated costs to remove equipment and reclaim the land associated with one research and development project. The Company estimates ARO liabilities for final reclamation based upon bids obtained from independent third parties and other exit alternatives, which are adjusted for inflation and then discounted at a credit-adjusted risk-free rate. Changes in estimates could occur due to revisions of estimated costs and changes in timing and performance of the reclamation activities. ARO liabilities are included within the Other long-term liabilities line item in the Consolidated Balance Sheets and discussed further in Note 10 . As of December 31, 2017 and December 31, 2016 , the ARO liability was zero and $1.3 million , 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 on the basis of the differences between the financial statements and tax basis of assets and liabilities using enacted tax rates in effect for the year in which the differences are expected to reverse. The effect of a change in tax rates on deferred tax assets and liabilities is recognized in operations in the period that includes the enactment date. The Company recognizes deferred tax assets and liabilities and maintains valuation allowances where it is more likely than not that all or a portion of deferred tax assets will 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. The Company records uncertain tax positions on the basis of a two-step process whereby (1) the Company determines whether it is more-likely-than-not that the tax positions will be sustained on the basis of the technical merits of the position and (2) for those tax positions that meet the more-likely-than-not recognition threshold, the Company recognizes the amount of tax benefit that is more than 50 percent likely to be realized upon ultimate settlement with the related tax authority. The Company records interest expense due to the Company's share of Tinuum Group's equity method earnings for Refined Coal ("RC") facilities, in which the lease income or sale is treated as installment sales for tax purposes. IRS section 453A requires taxpayers using the installment method to pay an interest charge on the portion of the tax liability that is deferred under the installment method. The Company recognizes IRS section 453A interest ("453A interest") and other interest and penalties related to unrecognized tax benefits in the Interest expense line item in the Consolidated Statements of Operations . Stock-Based Compensation Stock-based compensation expense is measured at the grant date based on the estimated fair value of the stock-based award and is generally expensed on a straight-line basis over the requisite service period and/or performance period of the award. Forfeitures are recognized when incurred. These costs are recorded in the Payroll and benefits or General and administrative , for director related expense, line items in the Consolidated Statements of Operations . Earnings (Loss) Per Share Basic earnings (loss) per share is computed using the two-class method, which is an earnings allocation formula that determines earnings (loss) per share for common stock and any participating securities according to dividend and participating rights in undistributed earnings. The Company's restricted stock awards ("RSA's") granted prior to December 31, 2016 contain non-forfeitable rights to dividends or dividend equivalents and are deemed to be participating securities. RSA's granted subsequent to December 31, 2016 do not contain non-forfeitable rights to dividends and are not deemed to be participating securities. Under the two-class method, net income (loss) for the period is allocated between common stockholders and the holders of the participating securities based on the weighted-average of common shares outstanding during the period, excluding participating, unvested RSA's ("common shares"), and the weighted-average number of participating, unvested RSA's outstanding during the period, respectively. The allocated, undistributed income for the period is then divided by the weighted-average number of common shares and participating, unvested RSA's outstanding during the period to determine basic earnings per common share and participating security for the period, respectively. Pursuant to accounting principles generally accepted in the United States ("U.S. GAAP"), the Company has elected not to separately present basic or diluted earnings per share attributable to participating securities in the Consolidated Statements of Operations. Diluted earnings per share is computed in a manner consistent with that of basic earnings per share, while considering other potentially dilutive securities. Potentially dilutive securities consist of both unvested, participating and non-participating RSA's, as well as outstanding options to purchase common stock ("Stock Options") and contingent performance stock units ("PSU's") (collectively, "Potential dilutive shares"). The dilutive effect, if any, for non-participating RSA's, Stock Options and PSU's is determined using the greater of dilution as calculated under the treasury stock method or the two-class method. Potential dilutive shares are excluded from diluted earnings (loss) per share when their effect is anti-dilutive. When there is a net loss for a period, all Potential dilutive shares are anti-dilutive and are excluded from the calculation of diluted loss per share for that period. Each PSU represents a contingent right to receive shares of the Company’s common stock, and the number of shares may range from zero to two times the number of PSU's granted on the award date depending upon the price performance of the Company's common stock as measured against a general index and a specific peer group index over requisite performance periods. The number of Potential dilutive shares related to PSU's is based on the number of shares of the Company's common stock, if any, that would be issuable at the end of the respective reporting period, assuming that the end of the reporting period is the end of the contingency period applicable to such PSU's. See Note 6 for additional information related to PSU's. The following table sets forth the calculations of basic and diluted earnings (loss) per common share: Years Ended December 31, (in thousands, except per share amounts) 2017 2016 2015 Net income (loss) $ 27,873 $ 97,678 $ (30,141 ) Less: Dividends and undistributed income (loss) allocated to participating securities 171 1,105 (275 ) Income (loss) attributable to common stockholders $ 27,702 $ 96,573 $ (29,866 ) Basic weighted-average number of common shares outstanding 21,367 21,931 21,773 Add: dilutive effect of equity instruments 46 303 — Diluted weighted-average shares outstanding 21,413 22,234 21,773 Earnings (loss) per share - basic $ 1.30 $ 4.40 $ (1.37 ) Earnings (loss) per share - diluted $ 1.29 $ 4.34 $ (1.37 ) For the years ended December 31, 2017 and 2016 , options to purchase 0.3 million and 0.2 million shares of common stock for each of the years presented were outstanding, but were not included in the computation of diluted net income per share because the exercise price exceeded the average price of the underlying shares and the effect would have been anti-dilutive. For the year ended December 31, 2015 , 0.4 million shares of the Company's outstanding equity awards were excluded from the calculation of diluted loss per share because their inclusion would have been anti-dilutive. For the years ended December 31, 2017 , 2016 and 2015 , options to purchase of 0.2 million , 0.2 million and 0.1 million shares of common stock, respectively, which vest based on the Company achieving specified performance targets, were outstanding, but not included in the computation of diluted net income per share because they were determined not to be contingently issuable. Use of Estimates The preparation of the Company’s consolidated financial statements in conformity with U.S. GAAP requires the Company’s management to make estimates and assumptions that affect the amounts reported in these financial statements and accompanying notes. Actual results could differ from those estimates. The Company makes assumptions on the following significant financial statement components including: • revenue recognition and warranty estimates accruals related to the Company's extended equipment contracts; • the carrying value of its long-lived assets; • the allowance for doubtful accounts receivable; • stock compensation costs; • estimates related to future obligations, including the Royalty Award, and other legal accruals; and • income taxes, including the valuation allowance for deferred tax assets and uncertain tax positions. Risks and Uncertainties The Company’s earnings are significantly affected by equity earnings it receives from Tinuum Group. Tinuum Group has 17 invested RC facilities of which 11 are leased to a single customer. A majority of these leases are periodically renewed and the loss of this customer by Tinuum Group would have a significant adverse impact on its financial position, results of operations and cash flows, which in turn would have material adverse impact on the Company’s financial position, results of operations and cash flows. Reclassifications Certain balances have been reclassified from prior years to conform to the current year presentation. New Accounting Guidance In May 2014, the FASB issued ASU No. 2014-09, Revenue from Contracts with Customers (Topic 606) ("ASU 2014-09"), which provides a single comprehensive model for entities to use in accounting for revenue arising from contracts with customers and supersedes current revenue recognition guidance, including industry-specific guidance. The core principle of ASU 2014-09 is that “an entity recognizes revenue to depict the transfer of promised goods or services to customers in an amount that reflects the consideration to which the entity expects to be entitled in exchange for those goods or services. ASU 2014-09 and its related amendments are effective for reporting periods (including interim periods) beginning after December 31, 2017. The standard may be applied retrospectively to each prior period presented or retrospectively with the cumulative effect recognized as of the date of adoption ("modified retrospective method"). The Company will adopt the standard under the modified retrospective method effective January 1, 2018, which will be reflected in its financial statements as of and for the three months ended March 31, 2018. As of the date of this filing, the Company has completed its assessment of ASU 2014-09 for the impact to the financial statements as of the adoption date, completed a detailed review of individual customer contracts, completed its review of controls and procedures that will be revised or added from the adoption of the standard, and completed its documentation of the standard's financial statement impact at adoption, financial statement presentation and disclosure changes and changes to existing revenue recognition policies, controls and procedures. As of the adoption date of ASU 2014-09, the Company has determined that deferred revenue and deferred project costs on uncompleted contracts as of December 31, 2017 related to equipment sales projects will be derecognized through a cumulative effect adjustment, which will reduce the opening balance of the Accumulated deficit in the amount of approximately $1.7 million , net of income taxes. In addition, as of the adoption date, the Company will also derecognize deferred revenue and deferred project costs as of December 31, 2017 for a technology licensing arrangement through a cumulative effect adjustment, which will reduce the Accumulated deficit in the amount of approximately $1.3 million , net of income taxes. Except for the reclassification of the Company's royalties received from related parties from Other income to Revenue, the Company expects that there will be no material financial statement impact as of the adoption date from other uncompleted contracts. In January 2016, the FASB issued ASU 2016-01, Financial Instruments (Subtopic 825-10) - Overall: Recognition and Measurement of Financial Assets and Financial Liabilities ("ASU 2016-01"). This standard provides guidance on how entities measure certain equity investments and present changes in the fair value. This standard requires that entities measure certain equity investments that do not result in consolidation and are not accounted for under the equity method at fair value and recognize any changes in fair value in net income. ASU 2016-01 is effective for fiscal years beginning after December 31, 2017. The Company is currently evaluating the provisions of this guidance and assessing its impact on the Company's financial statements and disclosures. The Company does not believe this standard will have a material impact on the Company's financial statements and disclosures. In February 2016, the FASB issued ASU 2016-02, Leases (Topic 842) ("ASU 2016-02"), which requires lessees to recognize a right of use asset and related lease liability for those leases classified as operating leases at the commencement date and have lease terms of more than 12 months. This topic retains the distinction between finance leases and operating leases. ASU 2016-02 is effective for fiscal years beginning after December 15, 2018, and interim periods within those years, and must be applied under a modified retrospective transition approach for leases existing at, or entered into after, the beginning of the earliest comparative period presented in the financial statements. The Company is currently evaluating the provisions of this guidance and assessing its impact on the Company's financial statements and disclosures. In June 2016, the FASB issued ASU 2016-13, Financial Instruments - Credit Losses (Topic 326) Measurement of Credit Losses on Financial Instruments ("ASU 2016-13"). The main objective of ASU 2016-13 is to

Equity Method Investments

Equity Method Investments	12 Months Ended
	Dec. 31, 2017
Equity Method Investments and Joint Ventures [Abstract]
Equity Method Investments	Equity Method Investments Tinuum Group, LLC As of December 31, 2017 and 2016 , the Company’s ownership in Tinuum Group was 42.5% . Tinuum Group supplies technology, equipment and technical services to cyclone-fired and other boiler users, but its primary purpose is to place into operation facilities that produce and sell RC that lower emissions and therefore qualifies for Section 45 tax credits. NexGen Refined Coal, LLC ("NexGen") and GSFS Investments I Corp. (“GSFS”), an affiliate of The Goldman Sachs Group, Inc. ("GS"), own the remaining 42.5% and 15.0% , respectively of Tinuum Group. GSFS' ownership interest is in the form of Class B units which provide certain preferences over ADA and NexGen as to liquidation and profit distribution, including a guaranteed 15% annual return on GSFS' unrecovered investment balance, which is calculated as the original GSFS investment, plus a 15% annual return thereon, less any distributions, including the allocation of Section 45 tax credits to the members. Additionally, on the 10 -year anniversary of the date the last RC facility owned by Tinuum Group or one of its subsidiaries is placed into service, but no later than December 31, 2021, if GSFS's unrecovered investment balance has not been reduced to zero, GSFS may require Tinuum Group to redeem its Class B units for an amount equal to the then unrecovered investment balance, payable within 180 days of the notice of redemption. GSFS has no further capital call requirements and does not have a voting interest, but does have approval rights over certain corporate transactions. However, the Class B units do not have voting rights and ADA and NexGen each maintain a 50% voting interest in Tinuum Group. In February 2018, the unrecovered investment balance associated with the Class B units was repaid in full. The Company has determined that Tinuum Group is a VIE, however, the Company does not have the power to direct the activities that most significantly impact Tinuum Group's economic performance and has therefore accounted for the investment under the equity method of accounting. The Company determined the voting partners of Tinuum Group have identical voting rights, equity control interests and board control interests, and therefore, concluded that the power to direct the activities that most significantly impact Tinuum Group's economic performance was shared. The following tables summarize the assets, liabilities and results of operations of Tinuum Group: As of December 31, (in thousands) 2017 2016 Current assets $ 31,068 $ 24,584 Non-current assets $ 75,592 $ 83,621 Current liabilities $ 48,280 $ 43,117 Non-current liabilities $ 8,350 $ 11,456 Redeemable Class B equity $ 821 $ 18,250 Members equity attributable to Class A members $ 40,452 $ 26,475 Noncontrolling interests $ 8,757 $ 8,907 Years Ended December 31, (in thousands) 2017 2016 2015 Gross profit $ 95,552 $ 92,305 $ 108,416 Operating, selling, general and administrative expenses 22,958 23,662 23,405 Income from operations 72,594 68,643 85,011 Other expenses (4,520 ) (8,775 ) (2,203 ) Class B preferred return (1,712 ) (3,901 ) (6,157 ) Loss attributable to noncontrolling interest 43,474 27,234 10,675 Net income available to Class A members $ 109,836 $ 83,201 $ 87,326 ADES equity earnings from Tinuum Group $ 48,875 $ 41,650 $ 8,651 As shown above, the Company reported earnings from its equity investment in Tinuum Group of $48.9 million , $41.7 million and $8.7 million for the years ended December 31, 2017 , 2016 and 2015 , respectively. As shown in the table below, the Company’s carrying value in Tinuum Group was reduced to zero for all years presented as cumulative cash distributions received from Tinuum Group exceeded the Company's pro-rata share of cumulative earnings in Tinuum Group. The carrying value of the Company's investment in Tinuum Group shall remain zero as long as the cumulative amount of distributions received from Tinuum Group continues to exceed the Company's cumulative pro-rata share of Tinuum Group's net income available to Class A members. For periods during which the ending balance of the Company's investment in Tinuum Group is zero , the Company only recognizes equity earnings from Tinuum Group to the extent that cash distributions are received from Tinuum Group during the period. For periods during which the ending balance of the Company's investment is greater than zero (e.g., when the cumulative earnings in Tinuum Group exceeds cumulative cash distributions received), the Company recognizes its pro-rata share of Tinuum Group's net income available to Class A members for the period, less any amount necessary to recover the cumulative earnings short-fall balance as of the end of the immediately preceding period. As of December 31, 2017 , the Company's carrying value in Tinuum Group has been reduced to zero , as the cumulative cash distributions received from Tinuum Group have exceeded the Company's pro-rata share of cumulative earnings in Tinuum Group. If Tinuum Group subsequently reports net income, the Company will not record its pro-rata share of such net income until the cumulative share of pro-rata income equals or exceeds the amount of its cumulative income recognized due to the receipt of cash distributions. Until such time, the Company will only report income from Tinuum Group to the extent of cash distributions received during the period. Thus, the amount of equity earnings or loss reported on the Consolidated Statement of Operations may differ from a mathematical calculation of earnings or loss attributable to the equity interest based upon the factor of the equity interest and the net income or loss available to Class A members as shown on Tinuum Group’s statement of operations. Additionally, for periods during which the carrying value of the Company's investment in Tinuum Group is greater than zero, distributions from Tinuum Group are reported on the Consolidated Statements of Cash Flows as "Distributions from equity method investees, return on investment" within Operating cash flows. For periods during which the carrying value of the Company's investment in Tinuum Group is zero, such cash distributions are reported on the Consolidated Statements of Cash Flows as "Distributions from equity method investees in excess of investment basis" within Investing cash flows. The following table presents the Company's investment balance, equity earnings, cash distributions and cash distributions in excess of the investment balance for the years ended December 31, 2015 through December 31, 2017 ( in thousands ): Description Date(s) Investment balance ADES equity earnings (loss) Cash distributions Memorandum Account: Cash distributions and equity loss in (excess) of investment balance Beginning balance 12/31/2014 $ — $ — $ — $ (29,877 ) ADES proportionate share of net income from Tinuum Group (1) 2015 activity 35,265 35,265 — — Recovery of cash distributions in excess of investment balance (prior to cash distributions) 2015 activity (29,877 ) (29,877 ) — 29,877 Cash distributions from Tinuum Group 2015 activity (8,651 ) — 8,651 — Adjustment for current year cash distributions in excess of investment balance 2015 activity 3,263 3,263 — (3,263 ) Total investment balance, equity earnings (loss) and cash distributions 12/31/2015 $ — $ 8,651 $ 8,651 $ (3,263 ) ADES proportionate share of net income from Tinuum Group (1) 2016 activity $ 35,019 $ 35,019 $ — $ — Recovery of cash distributions in excess of investment balance (prior to cash distributions) 2016 activity (3,263 ) (3,263 ) — 3,263 Cash distributions from Tinuum Group 2016 activity (41,650 ) — 41,650 — Adjustment for current year cash distributions in excess of investment balance 2016 activity 9,894 9,894 — (9,894 ) Total investment balance, equity earnings (loss) and cash distributions 12/31/2016 $ — $ 41,650 $ 41,650 $ (9,894 ) ADES proportionate share of net income from Tinuum Group (1) 2017 activity $ 46,551 $ 46,551 $ — $ — Recovery of cash distributions in excess of investment balance (prior to cash distributions) 2017 activity (9,894 ) (9,894 ) — 9,894 Cash distributions from Tinuum Group 2017 activity (48,875 ) — 48,875 — Adjustment for current year cash distributions in excess of investment balance 2017 activity 12,218 12,218 — (12,218 ) Total investment balance, equity earnings and cash distributions 12/31/2017 $ — $ 48,875 $ 48,875 $ (12,218 ) (1) The amounts of the Company's 42.5% proportionate share of net income as shown in the table above differ from mathematical calculations of the Company’s 42.5% equity interest in Tinuum Group multiplied by the amounts of Net Income available to Class A members as shown in the table above of Tinuum Group's results of operations due to adjustments related to the Class B preferred return and the elimination of Tinuum Group's earnings attributable to RCM6, of which the Company owned 24.95% during the year ended December 31, 2015 and for the period from January 1 through March 3, 2016. As noted below, the Company sold its interest in RCM6 on March 3, 2016. Additional information related to Tinuum Group pursuant to Regulation S-X Rule 3-09 ("Rule 3-09") of the Securities and Exchange Act of 1934 (the "Exchange Act") is included within Item 15 - "Exhibits and Financial Statement Schedules" ("Item 15") of this Form 10-K. Tinuum Services, LLC In 2010, the Company, together with NexGen, formed Tinuum Services for the purpose of operating and maintaining RC facilities, including those RC facilities leased or sold to third parties. The Company has determined that Tinuum Services is not a VIE and has evaluated the consolidation analysis under the Voting Interest Model. The Company has a 50% voting and economic interest in Tinuum Services, which is equivalent to the voting and economic interest of NexGen. Therefore, as the Company does not hold greater than 50% of the outstanding voting interests, either directly or indirectly, it has accounted for the investment under the equity method of accounting. As of December 31, 2017 and 2016 , the Company’s 50% investment in Tinuum Services was $4.3 million and $4.0 million , respectively. The following tables summarize the assets, liabilities and results of operations of Tinuum Services: As of December 31, (in thousands) 2017 2016 Current assets $ 546,681 $ 278,001 Non-current assets $ 98,640 $ 3,426 Current liabilities $ 178,376 $ 97,093 Non-current liabilities $ 75,717 $ 1,488 Equity $ 8,569 $ 7,918 Noncontrolling interests $ 382,659 $ 174,928 Years Ended December 31, (in thousands) 2017 2016 2015 Gross loss $ (64,796 ) $ (54,644 ) $ (42,496 ) Operating, selling, general and administrative expenses 147,917 134,782 161,456 Loss from operations (212,713 ) (189,426 ) (203,952 ) Other expenses (68 ) (56 ) (118 ) Loss attributable to noncontrolling interest 222,707 198,464 213,746 Net income $ 9,926 $ 8,982 $ 9,676 ADES equity earnings from Tinuum Services $ 4,963 $ 4,491 $ 4,838 Included within the Consolidated Statement of Operations of Tinuum Services during the years ended December 31, 2017 , 2016 and 2015 were losses related to VIE entities that are consolidated within Tinuum Services of $222.7 million , $198.5 million and $213.7 million , respectively. These losses do not impact the Company's equity earnings from Tinuum Services as 100% of those losses are attributable to a noncontrolling interest and eliminated in the calculations of Tinuum Services' net income attributable to the Company's interest. Other On March 3, 2016, the Company sold its 24.95% membership interest in RCM6 for a cash payment of $1.8 million and the assumption, by the buyer, of an outstanding note payable made (the ("RCM6 Note Payable") by the Company in connection with its purchase of RCM6 membership interests from Tinuum Group. In doing so, the Company recognized a gain on the sale of $2.1 million for the year ended December 31, 2016 , which is included within the Other line item in the Consolidated Statements of Operations . As a result of the sale of its ownership interest, the Company ceased to be a member of RCM6 and, as such, is no longer subject to any quarterly capital calls and variable payments to RCM6. In addition, the Company has no future obligations related to the RCM6 Note Payable. However, the Company still receives its pro-rata share of income and cash distributions through its ownership in Tinuum Group based on the RCM6 lease payments made to Tinuum Group. Prior to the sale of its ownership interest, the Company recognized equity losses related to its investment in RCM6 of $0.6 million for the three months ended March 31, 2016. On July 27, 2017, the Company obtained a 50% membership interest in GWN Manager in exchange for a capital contribution of $0.1 million . GWN Manager subsequently purchased a 0.2% membership interest in a subsidiary of Tinuum Group, which owns a single RC facility that produces RC that qualifies for Section 45 tax credits. Tinuum Group sold 49.9% of the subsidiary that owns the RC facility to an unrelated third party and retained ownership of the remaining 49.9% . GWN Manager is subject to monthly capital calls based on estimated working capital needs. The Company has determined that GWN Manager is not a VIE and has evaluated the consolidation analysis under the Voting Interest Model. Because the Company does not own greater than 50% of the outstanding voting shares, either directly or indirectly, it has accounted for its investment in GWN Manager under the equity method of accounting. As December 31, 2017 , the Company's ownership in GWN Manager was 50% . The Company's investment in GWN Manager as of December 31, 2017 , was $0.1 million . The following table details the carrying value of the Company's respective equity method investments included within the Equity method investments line item on the Consolidated Balance Sheets and indicates the Company's maximum exposure to loss: As of December 31, (in thousands) 2017 2016 Equity method investment in Tinuum Group $ — $ — Equity method investment in Tinuum Services 4,284 3,959 Equity method investment in other 67 — Total equity method investments $ 4,351 $ 3,959 The Company evaluates the investments for impairment whenever events or changes in circumstances indicate that the carrying amount of the investment might not be recoverable. No impairments were recorded during the years ended December 31, 2017 , 2016 and 2015 . The following table details the components of the Company's respective earnings or loss from equity method investments included within the Earnings from equity method investments line item on the Consolidated Statements of Operations : Year ended December 31, (in thousands) 2017 2016 2015 Earnings from Tinuum Group $ 48,875 $ 41,650 $ 8,651 Earnings from Tinuum Services 4,963 4,491 4,838 Earnings (losses) from other 5 (557 ) (4,568 ) Earnings from equity method investments $ 53,843 $ 45,584 $ 8,921 The following table details the components of the cash distributions from the Company's respective equity method investments included within the Consolidated Statements of Cash Flows . Distributions from equity method investees are reported on the Consolidated Statements of Cash Flows as “return on investment” within Operating cash flows until such time as the carrying value in an equity method investee company is reduced to zero ; thereafter, such distributions are reported as “distributions in excess of cumulative earnings” within Investing cash flows. Year ended December 31, (in thousands) 2017 2016 2015 Distributions from equity method investees, return on investment Tinuum Group (1) $ — $ 3,400 $ — Tinuum Services 4,638 4,500 5,019 Included in Operating Cash Flows $ 4,638 $ 7,900 $ 5,019 Distributions from equity method investees in excess of cumulative earnings Tinuum Group $ 48,875 $ 38,250 $ 8,651 Included in Investing Cash Flows $ 48,875 $ 38,250 $ 8,651 (1) During the three months ended March 31, 2016, the Company's cumulative share of pro-rata Tinuum Group's net income available to Class A members exceeded the amount of its cumulative earnings recognized due to cash being distributed. As such, the Company recognized $3.4 million as "return on investment." During the years ended December 31, 2017 , 2016 and 2015 , the Company, in the aggregate, made purchases of and contributions to equity method investments of $0.1 million , $0.2 million and $2.4 million , respectively.

Borrowings

Borrowings	12 Months Ended
	Dec. 31, 2017
Debt Disclosure [Abstract]
Borrowings	Borrowings Line of Credit In September 2013, ADA, as borrower, and the Company, as guarantor, entered into the 2013 Loan and Security Agreement with a bank (the "Lender") for an aggregate principal amount of $10 million that was secured by certain amounts due to the Company from certain Tinuum Group RC leases (the "Line of Credit"). The Line of Credit was amended nine times from the period from December 2, 2013 through November 25, 2016, most notably to extend the maturity date with each amendment. In addition, during this period, the Lender also granted 10 waivers related to various transactions and obligations to provide financial information to the Lender. Covenants in the Line of Credit included a borrowing base limitation that was based on a percentage of the net present value of ADA’s portion of payments due to Tinuum Group from the RC leases. The Line of Credit also contained other affirmative and negative covenants and customary indemnification obligations of ADA to the Lender and provided for the issuance of letters of credit ("LC's") provided that the aggregate amount of the LC's plus all advances then outstanding did not exceed the calculated borrowing base. The Company guarantees the obligations and agreements of ADA under the Line of Credit. Amounts outstanding under the Line of Credit bear interest payable monthly at a rate per annum equal to the higher of 5% or the “Prime Rate” (as defined in the Line of Credit) plus 1% . As a result of various covenant violations, the Company had no borrowing availability under the Line of Credit from inception through November 29, 2016. On November 30, 2016, ADA-ES, Inc., a wholly-owned subsidiary of the Company, as borrower, the Company, as guarantor, and a bank (the "Lender") entered into an amendment (the "Tenth Amendment") to the Line of Credit. The Tenth Amendment increased the Line of Credit to $15.0 million , extended the maturity date of the Line of Credit to September 30, 2017 and permitted the Line of Credit to be used as collateral (in place of restricted cash) for LC's related to equipment projects, the Royalty Award, as defined in Note 4 , and certain other agreements. Additionally, this amendment collateralized the Line of Credit with amounts due to the Company from an additional existing RC facility lease, which amounts also factor into the borrowing base limitation, and amended certain financial covenants. Pursuant to the Tenth Amendment, the Company was required to maintain a deposit account with the Lender, initially with a minimum balance of $6.0 million , which was reduced to $3.0 million based on the Company meeting certain conditions and maintaining minimum trailing twelve-month EBITDA (earnings before interest, taxes, depreciation and amortization as defined in the Tenth Amendment) of $24.0 million . The minimum deposit balance was classified as Restricted Cash on the Consolidated Balance Sheets as of December 31, 2016 . On September 30, 2017, ADA, as borrower, the Company, as guarantor, and the Lender entered into an amendment (the "Eleventh Amendment") to the Line of Credit. The Eleventh Amendment decreased the Line of Credit to $10.0 million due to decreased collateral requirements for the Company's outstanding LC's, extended the maturity date of the Line of Credit to September 30, 2018, and permitted the Line of Credit to be used as collateral (in place of restricted cash) for LC's up to $8.0 million related to equipment projects, the Royalty Award and certain other agreements. Additionally, under the Eleventh Amendment there is no minimum balance requirement based on the Company meeting certain conditions and maintaining minimum trailing twelve-month EBITDA (earnings before interest, taxes, depreciation and amortization as defined in the Eleventh Amendment) of $24.0 million . As of December 31, 2017 , there were no outstanding borrowings under the Line of Credit, however, LC's in the aggregate amount of $3.5 million were secured under the Line of Credit, resulting in borrowing availability of $6.5 million and LC availability of $4.5 million . Letters of Credit The Company has LC's related to the Royalty Award (as described in Note 4 ), equipment projects, certain other agreements. During March 2017, a customer drew on an LC related to an equipment system in the amount of $0.8 million ("LC Draw"), which was funded by borrowing availability under the LOC. The Company subsequently repaid the LC Draw to the Lender as of March 31, 2017. The Company is contesting the LC Draw and is pursuing legal actions to recover the entire amount of the LC Draw from the customer. The Company recorded an asset for the LC Draw net of estimated allowance of $0.4 million , which is included in Other assets on the Consolidated Balance Sheets. The following tables summarize the LC's outstanding and collateral, by asset type, reported on the Consolidated Balance Sheets: As of December 31, 2017 (in thousands) LC Outstanding Utilization of LOC Availability Restricted Cash Royalty Award (1) $ 3,500 $ 3,500 $ — Total LC outstanding $ 3,500 $ 3,500 $ — (1) As further discussed in Note 4 , the Company settled the liability related to the Royalty Award on December 29, 2017. The Company and other parties associated with the LC, executed the termination of the LC in January 2018. As of December 31, 2016 (in thousands) LC Outstanding Utilization of LOC Availability Restricted Cash Contract performance - equipment systems $ 1,855 $ 1,776 $ 86 Royalty Award 7,150 — 7,150 Other 6,500 — 6,500 Total LC outstanding $ 15,505 $ 1,776 $ 13,736 The following tables summarizes the expiration periods of the LC's based on the ultimate maturity date of the LC's as of December 31, 2017 : Expiration of Letters of Credit as of December 31, 2017 (in thousands) Less than 1 year 1-3 years 4-5 years After 5 years LC's $ 3,500 $ — $ — $ — Credit Agreement On June 30, 2016, the Company, the required lenders and the administrative agent under a $15.0 million short-term loan (the "Credit Agreement") agreed to terminate the Credit Agreement prior to the maturity date of July 8, 2016, effective upon the Company’s prepayment on June 30, 2016 of $9.9 million , which was comprised of the total principal balance of the loan and advances made to or for the benefit of the Company, together with all accrued, but unpaid, interest and the total amount of all fees, costs, expenses and other amounts owed by the Company thereunder, including a prepayment premium. The Lenders were beneficial owners of common stock in the Company. The Credit Agreement was approved by the Board and the Audit Committee as a related party transaction. Tinuum Group - RCM6 Note Payable The Company acquired a 24.95% membership interest in RCM6 from Tinuum Group in February 2014 through an up-front payment and the RCM6 Note Payable. Due to the payment terms of the note purchase agreement, the RCM6 Note Payable periodically added interest to the outstanding principal balance. The stated rate associated with the RCM6 Note Payable was 1.65% and the effective rate of the RCM6 Note Payable at inception was 20% . As discussed in Note 2 , on March 3, 2016, the Company sold its 24.95% membership interest in RCM6 and, as a result, the Company has no future obligations related to the RCM6 Note Payable. DSI Business Owner In February 2016, the Company entered into an agreement to settle an outstanding note payable of approximately $1.1 million for $0.3 million with the former owner of a business ("DSI Business Owner") acquired by the Company in 2012, which was paid during the first quarter of 2016. The Company recognized a gain related to the settlement of $0.9 million , which is included in the Other line item in the Condensed Consolidated Statements of Operations for the year ended December 31, 2016.

Commitments and Contingencies

Commitments and Contingencies	12 Months Ended
	Dec. 31, 2017
Commitments and Contingencies Disclosure [Abstract]
Commitments and Contingencies	Commitments and Contingencies Legal Proceedings The Company is from time to time subject to, and is presently involved in, various pending or threatened legal actions and proceedings, including those that arise in the ordinary course of its business. Such matters are subject to many uncertainties and to outcomes, the financial impacts of which are not predictable with assurance and that may not be known for extended periods of time. The Company records a liability in its consolidated financial statements for costs related to claims, settlements, and judgments where management has assessed that a loss is probable and an amount can be reasonably estimated. The Company’s significant legal proceedings are discussed below. Securities class action lawsuit: United Food and Commercial Workers Union v. Advanced Emissions Solutions, Inc. , No. 14-cv-01243-CMA-KMT (U.S. District Court, D. Colo.) As of December 31, 2016, the Company had a recorded liability and insurance receivable of $4.0 million in connection with this lawsuit as the losses in connection with this matter were probable and reasonably estimable under U.S. GAAP. The liability was originally recorded as of June 30, 2016 in the Legal settlements and accruals line item of the Consolidated Balance Sheet. The Company's insurance carriers funded the full settlement in November 2016. On February 10, 2017, the Company received an order and final judgment that the lawsuit was settled, and the entire case had been dismissed with prejudice. Stockholder derivative lawsuits: In Re Advanced Emissions Solutions, Inc. Shareholder Derivative Litigation , No. 2014CV-30709 (District Court, Douglas County, Colorado) (consolidated actions). As of December 31, 2016, the Company had a recorded liability and insurance receivable of $0.6 million in connection with this lawsuit as the losses in connection with this matter were probable and reasonably estimable under U.S. GAAP. The liability was originally recorded as of June 30, 2016 in the Legal settlements and accruals line item of the Consolidated Balance Sheet. A settlement for this lawsuit was approved and the case was closed on January 4, 2017, and the Company's insurance carriers funded the full settlement in January 2017. As of March 31, 2017, the Company no longer had any amounts impacting its consolidated financial statements as the order and judgment related to the lawsuit was received during the first quarter of 2017. SEC Inquiry On March 29, 2017, the Company and the Securities and Exchange Commission reached a settlement to resolve a previously disclosed investigation into certain accounting issues, as described in the Company's Annual Report on Form 10-K for the fiscal year ended December 31, 2014. Without admitting or denying the SEC’s allegations, the Company agreed to the terms of the settlement and agreed to pay a civil monetary penalty of $0.5 million . The Company had fully reserved for this penalty as of June 30, 2016. The penalty was paid in the first quarter of 2017. Settlement and Royalty Indemnity In 2011, the Company and Norit International B.V. ("Norit") entered into a settlement agreement (the "Norit Settlement Agreement") whereby the Company paid amounts related to a non-solicitation breach of contract claim ("Norit Litigation"), and was also required to pay additional damages (the "Royalty Award") related to certain future revenues generated from an activated carbon manufacturing plant (the "Red River Plant") that the Company owned through a joint venture with ADA Carbon Solutions, LLC ("Carbon Solutions"). Payments due under the Royalty Award were due quarterly in arrears through June 2018. Additionally, in 2011, the Company entered into the Settlement Agreement Regarding ADA-ES’ Indemnity Obligations (the "Indemnity Settlement Agreement") whereby the Company agreed to settle certain indemnity obligations asserted against the Company related to the Norit Litigation and relinquished all of its equity interest in Carbon Solutions. Under the Norit Settlement Agreement, the Company was required to pledge LC's as collateral for a portion of Royalty Award future payments due. In March 2017, the Company was required to increase its LC's under the Royalty Award based on a provision that required additional amounts be pledged because the Company had achieved annual earnings in excess of $20.0 million for the fiscal year ended December 31, 2016. Under this provision, the Company was required to provide an additional LC of $5.0 million , which was secured under the Line of Credit in March 2017. Under a separate provision of the Norit Settlement Agreement effective during 2017, the Company was required to increase the LC's, subject to the aggregate amount of estimated future payments due related to the Royalty Award, for any dividends issued by the Company prior to January 1, 2018 in amount equal to 50% of the aggregate fair market value of such dividends (the "Dividends Provision"). Based on the estimated remaining future payments due under the Royalty Award, the Dividends Provision did not impact the amount of LC's pledged during 2017. During the years ended December 31, 2017 and 2016 , the Company revised its estimate for future Royalty Award payments based in part on updated forecasts provided to the Company from Carbon Solutions. These forecasts included significant reductions in estimated future revenues generated at the Red River Plant. Based primarily on these updated forecasts, the Company recorded reductions to the Royalty Award accrual of $3.4 million and $4.0 million for the years ended December 31, 2017 and 2016 , respectively. In December 2017, the Company, Carbon Solutions and the parent company of Carbon Solutions agreed to terminate certain provisions of the Indemnity Settlement Agreement (the " Indemnity Termination Agreement"). Pursuant to an agreement executed concurrently with the Indemnity Termination Agreement, the Company, Norit and an affiliate of Norit (collectively referred to as “Norit”) agreed to a final payment in the amount of $3.3 million (the "Settlement Payment") to settle all outstanding royalty obligations owed under the terms of the Norit Settlement Agreement. This amount was paid by the Company on December 29, 2017. Under the Indemnity Termination Agreement, and upon payment of the Settlement Payment, the Company was relieved of certain financial and indemnity obligations required by the terms of the Norit Settlement Agreement, including the obligation to maintain LC's securing future royalty payment obligations. As of December 31, 2017, $3.5 million in LC's related to the Royalty Award were outstanding, but were canceled by all parties in January 2018, pursuant to the Indemnity Termination Agreement. As of December 31, 2016 , the Company carried the components of the Royalty Award in Legal settlements and accruals in the Consolidated Balance Sheets of $5.7 million , and in Legal settlements and accruals, long-term of $5.4 million . The following table summarizes the Company's legal settlements and accruals as described above, which are presented in the Consolidated Balance Sheets : As of December 31, (in thousands) 2017 2016 Settlement and Royalty Indemnification $ — $ 5,656 Legal settlements — 5,050 Legal settlements and accruals, current — 10,706 Settlement and Royalty Indemnification, long-term — 5,382 Total legal settlements and accruals $ — $ 16,088 As of December 31, 2016 , the receivables related to the legal settlements above are shown with the Receivables, net line item in the Consolidated Balance Sheets in the same amounts as the respective liabilities. Advanced Emission Solutions, Inc. Profit Sharing Retirement Plan The Advanced Emissions Solutions, Inc. Profit Sharing Retirement Plan (the “401(k) Plan”) is subject to the jurisdiction of the Internal Revenue Service ("IRS") and the Department of Labor ("DOL"). The DOL opened an investigation into the 401(k) Plan, and the Company is responding to all requests for documents and information from the DOL. The DOL has not issued any formal findings as of the date of this filing. Although the Company believes there has been no breach of fiduciary duty with respect to the 401(k) Plan, the Company believes that it is probable that the DOL will require some payment to the 401(k) Plan in order to close the investigation. The Company determined that this amount is reasonably estimable and, as such, the Company has accrued $1.0 million as of December 31, 2017 . The liability was recorded in the Other current liabilities line item on the Consolidated Balance Sheets. The expense recognized related to this accrual was included in the Other line item in the Consolidated Statements of Operations for the year ended December 31, 2017 . The estimate is based on information currently available and involves elements of judgment and significant uncertainties. As additional information becomes available and the resolution of the uncertainties becomes more apparent, it is possible that actual payment may exceed the accrued amount. Other Commitments and Contingencies Tinuum Group The Company also has certain limited obligations contingent upon future events in connection with the activities of Tinuum Group. The Company, NexGen and two entities affiliated with NexGen have provided GSFS with limited guaranties (the “Tinuum Group Party Guaranties”) related to certain losses it may suffer as a result of inaccuracies or breach of representations and covenants. The Company also is a party to a contribution agreement with NexGen under which any party called upon to pay on a Tinuum Group Party Guaranty is entitled to receive contribution from the other party equal to 50% of the amount paid. No liability or expense provision has been recorded by the Company related to this contingent obligation as the Company believes that it is not probable that a loss will occur with respect to Tinuum Group Party Guaranties. Performance Guarantee on Equipment Systems In the normal course of business related to ACI and DSI systems, the Company may guarantee certain performance thresholds during a discrete performance testing period that do not extend beyond six months from the initial test date, the commencement of which is determined by the customer. Performance thresholds include such matters as the achievement of a certain level of mercury removal and other emissions based upon the injection of a specified quantity of a qualified activated carbon or other chemical at a specified rate given other plant operating conditions, and availability of equipment and electric power usage. In the event the equipment fails to perform as specified during the testing period, the Company may have an obligation to correct or replace the equipment. In the event the performance thresholds are not achieved, the Company may have a “make right” obligation within the contract limits. During 2015, the Company began working to modify and correct two performance guarantee issues related to EC systems that were installed during 2015. No revenue was recognized on these two contracts until the performance guarantees were resolved and contract obligations were substantially complete. During 2016, the Company passed performance testing on both systems and revenues on both systems were recognized. As a result of the resolution of the performance guarantees, the Company incurred approximately $0.9 million of costs on the ACI systems to pass the performance guarantees. During the year ended December 31, 2016 , the Company satisfied all outstanding performance guarantees on its remaining ACI and DSI contracts and it did not incur any additional claims. Purchase Obligations The Company does not have any future purchase obligations as of December 31, 2017 . U.S. Department of Energy ("DOE") Audits Certain of the Company's completed and current contracts awarded by the DOE and related industry participants remain subject to adjustments as a result of future government audits. The Company's historical experience with these audits has not resulted in significant adverse adjustments to amounts previously received; however the Company currently remains subject to audits for the years 2013 and later. Operating Lease Obligations The Company leases office, warehouse and laboratory space in Highlands Ranch, Colorado under operating leases. As of December 31, 2017 , the Company leased approximately 17,344 square feet under two leases. Original lease terms ranged from four to seven years. Certain of these leases have options permitting renewals for additional periods. In addition to minimum fixed payments, a number of leases contain annual escalation clauses that are related to increases in the inflation index. In December 2016, the Company entered into a lease termination related to its leased office space, in which the Company paid a $0.3 million lease termination fee. The lease termination was effective February 2017. Also in December 2016, the Company entered into a new office lease in Highlands Ranch, Colorado effective February 2017. Annual minimum commitments under the leases as of December 31, 2017 are as follows: Years Ending December 31, Operating Lease Commitments (in thousands) 2018 $ 298 2019 205 2020 82 2021 — Thereafter — Total $ 585 Rent expense incurred for the years ended is as follows: Years Ended December 31, (in thousands) 2017 2016 2015 Rent expense (1) $ (60 ) $ 847 $ 1,838 (1) During the year ended December 31, 2017 , the Company accelerated deferred rent and tenant improvement allowances in connection with the termination of the lease agreement of its former corporate office.

Stockholders' Equity

Stockholders' Equity	12 Months Ended
	Dec. 31, 2017
Equity [Abstract]
Stockholders' Equity	Stockholders Equity The Company has two classes of capital stock authorized, common stock and preferred stock, which are described as follows: Preferred Stock The Board is authorized to provide out of the unissued shares of Preferred Stock and to fix the number of shares constituting a series of Preferred Stock and, with respect to each series, to fix the number of shares and designation of such series, the voting powers, if any, the preferences and relative, participating, option or other special rights, if any, and any qualifications, limitations or restrictions thereof, of the shares of such series. As of December 31, 2017 and 2016 , there were no shares of Preferred Stock designated or outstanding. Common Stock Holders of common stock are entitled to one vote for each share held of record on all matters submitted to a vote of the stockholders. Additionally, holders of common stock are entitled to receive dividends when and if declared by the Board, subject to any statutory or contractual restrictions on payment of dividends and to any restrictions on the payment of dividends imposed by the terms of any outstanding shares of preferred stock. Upon dissolution, liquidation or the sale of all or substantially all of the Company's assets, after payment in full of any amounts required to be paid to creditors and to the holders of preferred stock having liquidation preferences, if any, the holders of shares of common stock will be entitled to receive the Company's remaining assets for distribution on a pro rata basis. Stock Repurchase Tender Offer On May 5, 2017 , the Board authorized the commencement of a modified Dutch Auction tender offer ("Tender Offer") to purchase for cash up to 925,000 shares of the Company's common stock at a price per share of not less than $9.40 nor greater than $10.80 , for a maximum aggregate purchase price of $10.0 million , with an option to purchase an additional 2% of the outstanding shares of common stock if the Tender Offer was oversubscribed. The Tender Offer expired on June 6, 2017 and a total of 2,858,425 shares were validly tendered and not properly withdrawn at or below the final purchase price of $9.40 per share. Because the Tender Offer was oversubscribed, the Company purchased a prorated portion of the shares properly tendered by each tendering stockholder (other than "odd lot" holders whose shares were purchased on a priority basis) at the final per share purchase price. Accordingly, the Company acquired 1,370,891 shares of its common stock ("Tendered Shares") at a price of $9.40 per share, for a total cost of approximately $12.9 million , excluding fees and other expenses related to the tender offer. The Tendered Shares represented approximately 6.2% of the Company's outstanding shares prior to the tender offer. The Tendered Shares included the 925,000 shares the Company initially offered to purchase and 445,891 additional shares that the Company elected to purchase pursuant to its right to purchase up to an additional 2% of its outstanding shares of common stock. The Company recorded the Tendered Shares at cost, which included fees and expenses related to the Tender Offer, and reported the Tendered Shares as Treasury Stock on the Condensed Consolidated Balance Sheet as of December 31, 2017 . The Company’s Board and executive officers did not participate in the Tender Offer, except for one director of the Board, who is a manager of a financial institution and holds dispositive powers over the shares of the Company's common stock held by the financial institution that tendered 70,178 of its shares of the Company's common stock. Stock Repurchase Program During December 2017, and under a stock repurchase program authorized by the Board, the Company purchased 342,875 shares of its common stock for cash of $3.4 million , inclusive of commissions and fees, in open market transactions. Under the stock repurchase program, the Company is authorized to purchase up to $10.0 million of its outstanding common stock. This stock repurchase program will remain in effect until December 31, 2018 unless otherwise modified by the Board. Quarterly Cash Dividend Dividends declared and paid to holders of the Company's common shares during the years ended December 31, 2017 , 2016 and 2015 were $15.7 million , zero , and zero , respectively. A portion of the dividends remains accrued subsequent to the payment dates and represents dividends accumulated on nonvested shares of common stock held by employees of the Company that contain forfeitable dividend rights that are not payable until the underlying shares of common stock vest. These amounts are included in both Other current liabilities and Other long-term liabilities on the Condensed Consolidated Balance Sheet as of December 31, 2017 . Dividends declared and paid quarterly per share on all outstanding shares of common stock during the year ended December 31, 2017 were as follows: 2017 Per share Date paid Dividends declared during quarter ended: June 30 $ 0.25 July 17, 2017 September 30 0.25 September 7, 2017 December 31 0.25 December 6, 2017 $ 0.75 Tax Asset Protection Plan On May 5, 2017, the Board approved the declaration of a dividend of rights to purchase Series B Junior Participating Preferred Stock for each outstanding share of common stock as part of a Tax Asset Protection Plan designed to protect the Company’s ability to utilize its net operating losses and tax credits. United States federal income tax rules, and Section 382 of the Internal Revenue Code in particular, could substantially limit the use of net operating losses and other tax assets if ADES experiences an “ownership change” (as defined in the Internal Revenue Code). In general, an ownership change occurs if there is a cumulative change in the ownership of ADES by "5 percent stockholders" that exceeds 50 percentage points over a rolling three-year period. The Tax Asset Protection Plan is intended to act as a deterrent to any person acquiring beneficial ownership of 4.99% or more of the Company’s outstanding common stock and will expire on the earlier of (a) May 4, 2018, or (b) the date of the 2018 Annual Meeting of Stockholders. The Tax Asset Protection Plan may also be terminated earlier in accordance with the terms thereof.

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 Plans The Company currently has incentive plans, including the Amended and Restated 2010 Non-Management Compensation and Incentive Plan, as amended (the “2010 Plan”) and the 2017 Omnibus Incentive Plan (the “2017 Plan”) as described below. Collectively, these plans are called the “Stock Plans" and permit the Company to issue stock-based awards, including common stock, restricted stock, stock options and other rights and benefits under the plans to employees, directors and non-employees. The 2010 Plan - During 2010, the Company adopted the 2010 Plan which permits grants of stock awards to employees, which may be shares, rights to purchase restricted stock, bonuses of restricted stock, or other rights or benefits under the plan. The Company reserved 600,000 shares of its common stock for these purposes. The Plan was amended and restated as of July 19, 2012 to make non-material changes to assure Internal Revenue Code Section 409A compliance. Upon the adoption of the 2017 Plan in June 2017, the Company no longer grants any awards from the 2010 Plan. The 2017 Plan - During 2017, the Company adopted the 2017 Plan which permits grants of awards to employees, directors and non-employees, which may be shares, rights to purchase restricted stock, bonuses of restricted stock, or other rights or benefits under the plan. The Company reserved 2,000,000 shares of its common stock under the 2017 Plan. Expense Restricted Stock - Restricted stock is typically granted with vesting terms of three or five years. The fair value of Restricted Stock Awards ("RSA's") is determined based on the closing price of the Company’s common stock on the authorization date of the grant multiplied by the number of shares subject to the stock award. Compensation expense for RSA's is generally recognized over the entire vesting period on a straight-line basis. Stock Options - Stock options generally vest over three years or upon satisfaction of performance-based conditions and have a contractual limit of five years from the date of grant to exercise. The fair value of stock options granted is determined on the date of grant using the Black-Scholes option pricing model and the related expense is recognized on a straight-line basis over the entire vesting period. The following table indicates the weighted-average assumptions that were used related to the stock options granted for the years ended December 31, 2016 and 2015 , respectively. No stock options were granted during the year ended December 31, 2017 . Years Ended December 31, 2016 2015 Stock options granted: Risk-free interest rate 1.3 % 1.8 % Dividend yield — % — % Volatility 78.8 % 74.5 % Expected term (in years) 2.6 5.0 The Company uses historical data to estimate inputs used in the Black-Scholes option pricing model. Risk-free interest rate - The risk-free interest rate for stock options granted during the period was determined by using a zero-coupon U.S. Treasury rate for the periods that coincided with the expected terms listed above. Dividends - As historically no dividends had been paid as of the date by which grants occurred, no dividend yield was included in the calculations. Expected volatility - To calculate expected volatility, the historical volatility of the Company's common stock was used. Expected term - The Company’s expected term of options was based upon historical exercise behavior and consideration of the options' vesting and contractual terms. Stock Appreciation Rights - Stock Appreciation Rights ("SAR's") generally vest over three years and have a contractual limit of five years from the date of grant to exercise. The fair value of SAR's granted is determined on the date of grant using the Black-Scholes option pricing model and the related expense is recognized on a straight-line basis over the derived service period of the respective awards. During 2015, the Company granted a SAR award, and as settlement of the award was out of the control of the Company, the awards were classified as liability-based equity awards and were recorded at the estimated fair value at the grant and remeasured as a liability-based award as of each reporting period. This SAR award was converted to a stock option as of June 30, 2016 as discussed below. The following table indicates the weighted-average assumptions that were used related to the awards granted for the year ended December 31, 2015 . No SAR's were granted during the year ended December 31, 2017 or 2016 . Year ended December 31, 2015 SAR's granted: Risk-free interest rate 1.8 % Dividend yield — % Volatility 74.5 % Expected term (in years) 5.0 The Company uses historical data to estimate inputs used in the Black-Scholes option pricing model. Risk-free interest rate - The risk-free interest rate for SAR's granted during the period was determined by using a zero-coupon U.S. Treasury rate for the periods that coincided with the expected terms listed above. Dividends - As historically no dividends have been paid as of the date by which grants occurred, no dividend yield was included in the calculations. Expected volatility - To calculate expected volatility, the historical volatility of the Company's common stock was used. Expected term - The Company’s expected term of SAR's was based upon consideration of the contractual term of the Company’s SAR's of 5 years. PSU's - Performance share units ("PSU's") vest based on the grantee’s continuous service with the Company, performance measures or a combination of both. Each PSU represents a contingent right to receive shares of the Company’s common stock if the Company meets certain performance measures over the requisite period. Vesting of the PSU's, if at all, occurs no later than January 2 after the conclusion of the third year of the performance period, subject to the grantee’s continuous service and the achievement of certain pre-established performance goals. Amounts vested are measured as of December 31, immediately prior to the end of the service period, unless the PSU's vest sooner at the target amount as a result of certain transactions pursuant to Section 11 of the Amended and Restated 2007 Equity Incentive Plan, as amended ("2007 Plan"). The number of shares of common stock a participant receives will be increased (up to 200 percent of target levels) or reduced (down to zero ) based on the level of achievement of performance goals. The number of PSU's that may be earned by a participant is determined at the end of the performance period based on the relative placement of the Company’s total stockholder return (“TSR”) for that period with approximately 75% of the award based on the relative performance of the Company’s TSR performance compared to the respective TSRs of a specified group of peer companies and the remaining portion of the award based on the Company’s TSR performance compared to the Russell 3000 Index. Compensation expense is recognized for PSU awards on a straight-line basis over a 3 -year service period based on the estimated fair value at the date of grant using a Monte Carlo simulation model. The following table indicates the weighted-average assumptions that were used related to the awards granted for the year ended December 31, 2015 . No PSU's were granted during the years ended December 31, 2017 or 2016 . Year Ended December 31, 2015 PSUs granted: Risk-free interest rate 1.0 % Dividend yield — % Volatility 64.3 % Performance period (in years) 3.0 The Company uses historical data to estimate inputs used in the Monte Carlo pricing model. Risk-free interest rate - The risk-free interest rate for PSU's granted during the period was determined by using a zero-coupon U.S. Treasury rate for the periods that coincided with the expected terms listed above. Dividends - As historically no dividends had been paid as of the date by which grants occurred, no dividend yield was included in the calculations. Expected volatility - To calculate expected volatility, the historical volatility of the Company's common stock was used. Performance period - The Company’s performance period is based upon the vesting term of the Company’s PSU awards. The Company recorded the following compensation expense related to the Stock Plans and the 2007 Plan: Years Ended December 31, (in thousands) 2017 2016 2015 RSA expense $ 1,400 $ 2,021 $ 2,909 Stock option expense 672 285 658 SAR expense — 106 742 PSU expense 137 456 2,895 Total stock-based compensation expense $ 2,209 $ 2,868 $ 7,204 The Company recorded stock-based compensation expense related to awards to Directors in the General and administrative expense line and all other awards within the Payroll and benefit expense line in the Consolidated Statements of Operations. During the years ended December 31, 2016 and 2015 , the Company modified the terms of awards granted to 27 and 37 employees, respectively, in connection with its restructuring plans and termination of the impacted employees discussed in Note 18 . These modifications resulted in the accelerated vesting and incremental expense related to certain performance-based awards and restricted stock awards. As a result, during 2016 and 2015 the Company recognized incremental stock-based compensation of $0.4 million and $3.4 million respectively, which was included in the Payroll and benefits line item in the Consolidated Statements of Operations. There were no material modifications to awards during the year ended December 31, 2017 . The amount of unrecognized compensation cost as of December 31, 2017 , and the expected weighted-average period over which the cost will be recognized is as follows: As of December 31, 2017 (in thousands) Unrecognized Compensation Cost Expected Weighted-Average Period of Recognition (in years) RSA expense $ 1,735 1.93 Stock option expense 58 0.25 PSU expense — 0 Total unrecognized stock-based compensation expense $ 1,793 1.88 Activity Restricted Stock A summary of the status and activity of non-vested RSA's is presented in the following table: For the Years Ended December 31. 2017 2016 2015 (in thousands, except for share and per share amounts) Shares Weighted- Shares Weighted-Average Shares Weighted-Average Non-vested at beginning of year 297,347 $ 8.03 134,708 $ 8.49 209,921 $ 13.59 Granted 191,076 $ 9.50 363,758 $ 7.46 127,943 $ 14.97 Vested (210,129 ) $ 8.03 (175,956 ) $ 11.96 (165,796 ) $ 17.51 Forfeited (1) (1,687 ) $ 9.17 (25,163 ) $ 15.58 (37,360 ) $ 19.30 Non-vested at end of year 276,607 $ 9.03 297,347 $ 8.03 134,708 $ 8.49 (1) Included within the 2015 forfeited / canceled units are RSA's related to a former executive that were clawed back. The Company recognized $0.1 million within Other Income line item on the Consolidated Statement of Operations related to these awards. The weighted-average grant-date fair value of RSA's granted or modified during the years ended December 31, 2017 , 2016 , and 2015 was $1.8 million , $2.7 million , and $1.9 million , respectively. The total fair value of RSA's vested during the years ended December 31, 2017 , 2016 and 2015 was $1.7 million , $2.1 million and $2.9 million , respectively. Stock Options A summary of option activity under the Plans is presented below: (in thousands, except for share and per share amounts) Number of Weighted- Aggregate Intrinsic Value Weighted- For the year ended December 31, 2015 Options outstanding, January 1, 2015 74,200 $ 13.76 Options granted 56,250 $ 13.87 Options exercised — $ — Options expired / forfeited (24,200 ) $ 7.59 Options outstanding, December 31, 2015 106,250 $ 15.22 $ — 3.8 Options vested and exercisable, December 31, 2015 82,915 $ 14.04 $ — 3.9 For the year ended December 31, 2016 Options outstanding, January 1, 2016 106,250 $ 15.22 Options granted (1) 546,196 $ 11.10 Options exercised — $ — Options expired / forfeited (20,000 ) $ 16.90 Options outstanding, December 31, 2016 632,446 $ 11.61 $ 183 4.0 Options vested and exercisable, December 31, 2016 247,780 $ 13.30 $ 69 3.4 For the year ended December 31, 2017 Options outstanding, January 1, 2017 632,446 $ 11.61 Options granted — $ — Options exercised — $ — Options expired / forfeited (10,000 ) $ 9.77 Options outstanding, December 31, 2017 622,446 $ 11.64 $ 119 2.24 Options vested and exercisable, December 31, 2017 429,780 $ 11.47 $ 119 2.03 (1) Included in options granted are 243,750 awards granted that were initially granted on a contingent basis and became exercisable as a result of the automatic expiration of the same number of SAR's, as a result of stockholder approval of Amendment No. 4 of the 2007 Plan. See "SAR's" section below for a discussion of the provisions of the exchange and incremental expense recognized. The weighted-average grant-date fair value of options granted during the years ended December 31, 2017 , 2016 , and 2015 was zero , $0.5 million , and $0.8 million , respectively. There were no options exercised during the years ended December 31, 2017 , 2016 and 2015 . The weighted-average grant-date fair value of options vesting during the years ended December 31, 2017 , 2016 , and 2015 was $0.7 million , $0.5 million , and $0.7 million , respectively. Cash flows resulting from excess tax benefits, if any, are classified as part of cash flows from financing activities. Excess tax benefits are realized tax benefits from tax deductions for vested RSA's, settled PSU's and exercised options in excess of the deferred tax asset attributable to stock compensation costs for such equity awards. The Company recorded no excess tax benefits for the years ended December 31, 2017 , 2016 , and 2015 . During 2015, approximately $0.5 million of stock-based compensation expense was recognized as a result of granting an executive officer stock options which were immediately vested, with an exercise price of $13.87 per option. SAR's A summary of SAR activity under the Plans is presented below: (in thousands, except for share and per share amounts) Number of Weighted- Aggregate Intrinsic Value Weighted- For the year ended December 31, 2015 SAR's outstanding, January 1, 2015 — $ — Granted 243,750 $ 13.87 Exercised — $ — Expired / forfeited — $ — SAR's outstanding, December 31, 2015 243,750 $ 13.87 $ — 4.5 SAR's vested and exercisable, December 31, 2015 43,750 $ 13.87 $ — — For the year ended December 31, 2016 SAR's outstanding, January 1, 2016 243,750 $ 13.87 Granted — $ — Exercised — $ — Expired / forfeited (243,750 ) $ 13.87 SAR's outstanding, December 31, 2016 — $ — $ — — SAR's vested and exercisable, December 31, 2016 — $ — $ — — In June 2016, the Company's stockholders approved Amendment No. 4 to the 2007 Plan, which triggered an automatic expiration of the SAR's and an equal number of stock options being exercisable and no longer granted on a contingent basis. Upon approval, all existing SAR's expired under this provision. The Company recorded incremental expense of $0.1 million to stock-based compensation related to the change in fair value of the SAR's prior to the reclassification date. Upon reclassification, the impact to Additional paid-in capital was a $0.9 million increase. The Company had no SAR's outstanding as of December 31, 2017 . PSU's A summary of the status and activity of non-vested PSU's is presented in the following table: For the Years Ended December 31. 2017 2016 2015 (in thousands, except for unit and per unit amounts) Units Weighted-Average Units Weighted-Average Units Weighted-Average Non-vested at beginning of year 49,516 $ 25.20 169,334 $ 26.38 142,357 $ 30.65 Granted (1) — $ — — $ — 69,218 $ 20.10 Vested (1) (30,110 ) $ 26.87 (119,818 ) $ 26.87 (13,763 ) $ 30.52 Forfeited / Canceled (1) (2) — $ — — $ — (28,478 ) $ 30.44 Non-vested at end of year 19,406 $ 19.95 49,516 $ 25.20 169,334 $ 26.38 (1) The number of units shown in the table above are based on target performance. The final number of shares of common stock issued may vary depending on the achievement of market conditions established within the awards, which could result in the actual number of shares issued ranging from zero to a maximum of two times the number of units shown in the above table. (2) Included within the 2015 forfeited / canceled units are PSU's related to a former executive that were clawed back. The Company recognized $0.2 million within Other Income line item on the Consolidated Statement of Operations related to these awards . The weighted-average grant date fair value of PSU's granted during the years ended December 31, 2017 , 2016 , and 2015 was zero , zero , and $1.4 million , respectively. The PSU's granted will remain unvested until the third anniversary date of their issuance, at which time the actual number of vested shares will be determined based upon the actual price performances of the Company’s common stock relative to a broad stock index and a peer group performance index. The following table shows the PSUs that were settled by issuing the Company's common stock relative to a peer group performance index and broad stock index. Year of Grant Net Number of Issued Shares upon Vesting Shares Withheld to Settle Tax Withholding Obligations TSR Multiple Range Russell 3000 Multiple Low High Low High For the year ended December 31, 2017 2014 6,476 3,573 0.75 1.00 — — 2015 3,869 2,310 0.60 0.60 — — For the year ended December 31, 2016 2013 38,706 1,572 0.63 1.00 — — 2014 11,487 — 0.63 0.63 — — 2015 13,529 — 0.50 0.50 — — For the year ended December 31, 2015 2013 8,768 3,954 1.75 1.75 2.00 2.00 2014 2,506 1,145 0.63 0.75 — 0.75

Property and Equipment

Property and Equipment	12 Months Ended
	Dec. 31, 2017
Property, Plant and Equipment [Abstract]
Property and Equipment	Property and Equipment The carrying basis and accumulated depreciation of property and equipment at December 31, 2017 and 2016 are: Life in Years As of December 31, (in thousands) 2017 2016 Machinery and equipment 2-7 $ 1,429 $ 1,634 Leasehold improvements 3 205 1,244 Furniture and fixtures 3-7 262 777 1,896 3,655 Less accumulated depreciation and amortization (1,486 ) (2,920 ) Total property and equipment, net $ 410 $ 735 Depreciation expense for the years ended December 31, 2017 , 2016 and 2015 was $0.7 million , $0.9 million and $1.7 million , respectively. During the year ended December 31, 2016 , the Company recorded impairments totaling approximately $0.5 million to reduce the carrying value of certain property and equipment that the Company intended to sell at its estimated sales value, less estimated costs to sell. The property and equipment was subsequently sold at auction. No gain or loss was recognized on the sale of the property and equipment. During the year ended December 31, 2016 , the Company accelerated depreciation of approximately $0.2 million related to property and equipment that will be no longer be in service due to the lease termination described in Note 4 .

Costs and Billings on Uncomplet

Costs and Billings on Uncompleted Contracts	12 Months Ended
	Dec. 31, 2017
Costs and Billings on Uncompleted Contracts [Abstract]
Costs and Billings on Uncompleted Contracts	Costs and Billings on Uncompleted Contracts Costs incurred on uncompleted contracts represent the gross costs as of the balance sheet dates. Billings on uncompleted contracts represent the gross billings as of the balance sheet dates. Costs and billings are netted on an individual contract basis, with contracts in a net cost position aggregated and presented as Costs in excess of billings on uncompleted contracts in the Consolidated Balance Sheets , and contracts in a net billing position aggregated and presented as Prepaid expenses and other assets in the Consolidated Balance Sheets . The below table shows the components of these items: As of December 31, (in thousands) 2017 2016 Costs incurred on uncompleted contracts (gross) $ 15,945 $ 42,993 Billings on uncompleted contracts (gross) (17,775 ) (47,915 ) $ (1,830 ) $ (4,922 ) Included in the accompanying balance sheets under the following captions (1) : Costs in excess of billings on uncompleted contracts (2) $ — $ 25 Billings in excess of costs on uncompleted contracts (1,830 ) (4,947 ) $ (1,830 ) $ (4,922 ) (1) Amounts presented after netting of costs and billings on an individual contract basis. (2) Costs in excess of billings on uncompleted contracts is included in the Prepaid expenses and other assets caption on the Consolidated Balance Sheets. When the Company determines that a contract will ultimately be completed at a loss, the Company estimates such loss and accrues the loss as a loss contract accrual in the period that the loss determination is made. Loss contract accruals of $0.1 million and $0.2 million as of December 31, 2017 and 2016 , respectively, are included in Other current liabilities line item in the Consolidated Balance Sheets . During the years ended December 31, 2017 , 2016 and 2015 , the Company recorded loss contract provisions of $0.1 million , $0.4 million and $0.3 million , respectively. Loss contract provisions are included within the Equipment sales cost of revenue, exclusive of depreciation and amortization line item in the Consolidated Statements of Operations .

Research and Development and Go

Research and Development and Government and Industry Funded Contracts	12 Months Ended
	Dec. 31, 2017
Government and Industry Funded Contracts [Abstract]
Research and Development and Government and Industry Funded Contracts	Research and Development and Government and Industry Funded Contracts Research and development expense consists of research relating to continued product development for the Company’s ongoing business and various other projects, including the CO 2 capture and control market. The Company historically entered into certain development and cost-sharing contracts with the DOE and generally included industry cost-share partners to offset the costs incurred that are anticipated to be in excess of funded amounts from the DOE. Contracts with the DOE can take the form of grants or cooperative agreements and are considered financial assistance awards. The deliverables required by the DOE agreements include various technical and financial reports that the Company submits on a prescribed schedule. The agreements require the Company to perform the negotiated scope of work in agreed phases, which includes testing and demonstration of technologies. The Company typically invoices the DOE and industry cost-share partners monthly for labor and expenditures plus estimated overhead factors, less any cost share amounts. The contracts under which the Company has performed are subject to audit, the result of which may require the Company to reimburse the DOE for disallowed costs and other adjustments. The Company has not experienced any material adverse adjustments as a result of completed government audits. However, the potential government audits for years ended 2013 through 2015 have not yet been finalized. The following table shows the impact to Research and development expense amounts recognized in the Consolidated Statement of Operations: Years Ended December 31, (in thousands) 2017 2016 2015 Research and development expense $ 979 $ 173 $ 6,737 Less: Changes due to amount and timing of ARO reclamation 822 — — DOE funding — 821 1,375 Research and development expense, net $ 157 $ (648 ) $ 5,362 Included within the above research and development expenses during 2015 is net impairment expense of $1.9 million for the entire carrying value of the Company's ADA Analytics Israel Ltd's ("ADA Analytics") assets, as discussed in Note 17 and Note 18 .

Supplemental Financial Informat

Supplemental Financial Information	12 Months Ended
	Dec. 31, 2017
Deferred Costs, Capitalized, Prepaid, and Other Assets Disclosure [Abstract]
Supplemental Financial Information	Supplemental Financial Information Supplemental Balance Sheet Information The following table summarizes the components of Prepaid expenses and other assets and Other assets as presented in the Consolidated Balance Sheets : As of December 31, (in thousands) 2017 2016 Other current assets: Prepaid expenses $ 1,678 $ 1,169 Inventory 74 16 Costs in excess of billings — 25 Other 83 172 $ 1,835 $ 1,382 Other long-term assets: Deposits $ 223 $ 263 Intangibles 805 696 Cost method investment 552 1,016 Other long-term assets 728 323 $ 2,308 $ 2,298 The Company's cost method investment relates to its investment in Highview Enterprises Limited ("Highview"). In November 2014, the Company acquired an 8% ownership interest in the common stock of Highview for $2.8 million in cash (the "Highview Investment"). The Company evaluated the Highview Investment and determined that it should account for the investment under the cost method. The Highview Investment is evaluated for impairment upon an indicator of impairment such as an event or change in circumstances that may have a significant adverse effect on the fair value of the investment. As of December 31, 2016 , the Company recorded an impairment charge of $1.8 million based on an estimated fair value of £2.00 per share, compared to the carrying value prior to the impairment charge of £4.25 per share. The estimated fair value as of December 31, 2016 was based on an equity raise that was completed during the first quarter of 2017 at a price of £2.00 per share. During the year ended December 31, 2017 , the Company recorded an impairment charge of $0.5 million , which is included in the Other line item in the Consolidated Statement of Operations, based on an estimated fair value of £1.00 per share, compared to the carrying value prior to the impairment charge of £2.00 per share. The estimated fair value as of December 31, 2017 was based on an equity raise that commenced during the third quarter of 2017 at a price of £1.00 per share. The following table details the components of the Company's intangible assets: As of December 31, 2017 2016 (in thousands, except years) Initial Cost Net of Accumulated Amortization Initial Cost Net of Accumulated Amortization Patents $ 1,079 $ 805 $ 913 $ 696 Licensed technology — — 1,525 — Total $ 1,079 $ 805 $ 2,438 $ 696 Included in the Consolidated Statements of Operations is amortization expense related to intangible assets of $0.1 million , $0.1 million and $0.4 million for the years ended December 31, 2017 , 2016 and 2015 , respectively. The estimated future amortization expense for existing intangible assets as of December 31, 2017 is expected to be $0.1 million for each of the five succeeding fiscal years. During the year ended December 31, 2016, the Company entered into an agreement with Highview to terminate a license agreement (the "Highview License") to certain technology ("Licensed Technology") in exchange for a one-time payment by the Company of £0.2 million (approximately $0.2 million ). Under the termination, payment of the termination fee, if any, will only be settled by relinquishing shares of Highview currently owned by the Company equal to £0.2 million . As a result of terminating the Highview License, the Company wrote off the Licensed Technology, reduced the corresponding long-term liability ("Highview Obligation") to the amount of the one-time payment, and recognized a gain of approximately $0.2 million . The gain on the settlement of the Highview Obligation is included in the Other income line on the Company's Consolidated Statement of Operations for the year ended December 31, 2016. The following table details the components of Other current liabilities and Other long-term liabilities as presented in the Consolidated Balance Sheets : As of December 31, (in thousands) 2017 2016 Other current liabilities: Estimated Company contribution to 401(k) Plan $ 1,000 $ — Accrued interest — 618 Accrued losses on equipment contracts 69 183 Taxes payable 207 244 Deferred revenue — 76 Warranty liabilities 316 287 Deferred rent — 369 Asset retirement obligation — 1,312 Other 1,072 928 $ 2,664 $ 4,017 Other long-term liabilities: Deferred revenue, related party $ 2,000 $ 2,000 Deferred rent 192 38 Other long-term liabilities 93 — $ 2,285 $ 2,038 The tables below detail components of Other current liabilities as presented above: The changes in the carrying amount of the Company’s warranty obligations were as follows: As of December 31, (in thousands) 2017 2016 Balance, beginning of year $ 287 $ 1,197 Warranties accrued, net 580 89 Warranty claims (635 ) (899 ) Change in estimate related to previous warranties accrued 84 (100 ) Balance, end of year $ 316 $ 287 Included within Other current liabilities is the Company's asset retirement obligation. Changes in the Company's asset retirement obligation were as follows: As of December 31, (in thousands) 2017 2016 Asset retirement obligation, beginning of year $ 1,312 $ 1,248 Accretion 37 64 Liabilities settled (527 ) — Changes due to scope and timing of reclamation (822 ) — Asset retirement obligations, end of year $ — $ 1,312 The Company settled its asset retirement obligation during the year ended December 31, 2017 for less than its estimate as the scope of the asset retirement obligation was reduced. The change in estimate was recorded within the Research and development, net line item of the Consolidated Statements of Operations as the asset retirement obligation related to a research project of which expenses were originally recorded within the same line item. Supplemental Consolidated Statements of Operations Information The following table details the components of Interest expense in the Consolidated Statements of Operations : Years Ended December 31, (in thousands) 2017 2016 2015 453A interest $ 2,555 $ 2,490 $ 4,639 Line of Credit interest and letters of credit fees 417 89 49 Credit Agreement interest — 2,112 1,180 Interest on RCM6 Note Payable, related party — 263 2,468 Other 52 112 66 $ 3,024 $ 5,066 $ 8,402 The following table details the components of Other in the Consolidated Statements of Operations : Years Ended December 31, (in thousands) 2017 2016 2015 Impairment of cost method investment $ (464 ) $ (1,760 ) $ — Settlement agreement (1) 3,500 — — Estimate of Company contribution to 401(k) Plan (1,000 ) — — Gain on sale of equity method investment — 2,078 — Gain on settlement of note payable and licensed technology — 1,019 — Gain on termination of sales-type lease — 891 — Other (11 ) 235 494 $ 2,025 $ 2,463 $ 494 (1) On November 6, 2017, the Company entered into a settlement agreement with a former third-party service provider and as part of the settlement the Company received cash in the amount of $ 3.5 million . This amount was paid to the Company during the fourth quarter of 2017.

Fair Value Measurements

Fair Value Measurements	12 Months Ended
	Dec. 31, 2017
Fair Value Disclosures [Abstract]
Fair Value Measurements	Fair Value Measurements Fair Value of Financial Instruments The carrying amounts of financial instruments, including cash and cash equivalents, accounts receivable, accounts payable, deposits and accrued expenses, approximate fair value due to the short maturity of these instruments. Accordingly, these instruments are not presented in the table below. The following table provides the estimated fair values of the remaining financial instruments: As of December 31, 2017 As of December 31, 2016 (in thousands) Carrying Value Fair Value Carrying Value Fair Value Financial Instruments: Highview Investment $ 552 $ 552 $ 1,016 $ 1,016 Highview Obligation $ 210 $ 210 $ 207 $ 207 Concentration of credit risk As of December 31, 2017 , the Company’s financial instruments that are exposed to concentrations of credit risk consist primarily of cash and cash equivalents. The Company holds cash and cash equivalents at one financial institution as of December 31, 2017. If that institution was to be unable to perform its obligations, the Company would be at risk regarding the amount of investment in excess of the federal deposit insurance corporation limits ( $250 thousand ) that would be returned to the Company. Assets and Liabilities Measured at Fair Value on a Recurring Basis As of December 31, 2017 and December 31, 2016 , the Company had no financial instruments carried and measured at fair value on a recurring basis. Assets and Liabilities Measured at Fair Value on a Non-Recurring Basis As discussed in Note 10 , during the years ended December 31, 2017 and 2016 , the Company recorded impairment charges approximately $0.5 million and $1.8 million , respectively, to reduce the carrying value of the Highview Investment to its estimated fair value. During 2016 , the Company recorded impairments totaling approximately $0.5 million to reduce the carrying value of certain property and equipment that the Company intended to sell at its estimated sales value, less estimated costs to sell. The property and equipment was subsequently sold at auction. Proceeds from the sale of the impaired assets totaled approximately $0.1 million . No gain or loss was recognized on the sale of the property and equipment. Additionally, the Company recorded an impairment of approximately $0.8 million included within Equipment sales cost of revenue for the year ended December 31, 2016. During December 2014 and March 2015, the Company loaned to an independent technology development company exploring energy storage a total of $1.0 million to provide financing to pursue emissions technology projects. This note bore annual interest of 8% , and interest and principal were payable at maturity in March 2018. Based on uncertainty of collectability, the Company recorded an allowance against the entire principal balance reversed accrued interest and put the note on non-accrual status as of December 31, 2015. The fair value measurements represent Level 3 measurements as they are based on significant inputs not observable in the market.

Income Taxes

Income Taxes	12 Months Ended
	Dec. 31, 2017
Income Tax Disclosure [Abstract]
Income Taxes	Income Taxes On December 22, 2017 (the "Enactment Date"), the U.S. government enacted comprehensive tax legislation commonly referred to as the Tax Cuts and Jobs Act (the "Tax Act"). The Tax Act makes broad and complex changes to the U.S. tax code and key provisions applicable to the Company, or certain of Tinuum Group's existing or potential customers, for 2018 include the following: (1) reduction of the U.S. federal corporate tax rate from 35 percent to 21 percent ; (2) elimination of the corporate alternative minimum tax (AMT); (3) a new limitation on deductible interest expense; (4) limitations on the deductibility of certain executive compensation; (5) limitations on the use of federal tax credits ("FTCs") to reduce the U.S. income tax liability; (6) limitations on net operating losses (“NOL’s”) generated after December 31, 2017, to 80 percent of taxable income; and the introduction of the Base Erosion Anti-Abuse Tax (“BEAT”) for tax years beginning after December 31, 2017. Concurrent with the enactment of the Tax Act, in December 2017, the SEC staff issued Staff Accounting Bulletin 118 ("SAB 118"), which provides guidance on accounting for the tax effects of the Tax Act. SAB 118 provides a measurement period that should not extend beyond one year from the Enactment Date for companies to complete the accounting under Accounting Standards Codification 740 - Income Taxes ("ASC 740"). In accordance with SAB 118, a company must reflect the income tax effects of those aspects of the Tax Act for which the accounting under ASC 740 is complete. To the extent that an entity's accounting for certain income tax effects of the Tax Act is incomplete but it is able to determine a reasonable estimate, it must record a provisional estimate in the financial statements. If a company cannot determine a provisional estimate to be included in the financial statements, it should continue to apply ASC 740 on the basis of the provisions of the tax laws that were in effect immediately before the enactment of the Tax Act. The Company's accounting for the income tax effects of the Tax Act affecting its consolidated financial statements as of December 31, 2017 is generally complete, subject to continued evaluation under SAB 118, and as such, the Company recorded an adjustment to its recorded deferred tax assets and deferred tax liabilities as of the Enactment Date from 35 percent to 21 percent. Accordingly, the Company has recorded a reduction of $5.8 million to its net deferred tax asset as of December 22, 2017 with a corresponding entry to deferred tax expense for the year ended December 31, 2017 for those temporary differences expected to reverse after the Enactment Date. The Company does not anticipate any other accounting impacts of the Tax Act during the period within one year from the Enactment Date however, it will continue to assess any potential impact from the Tax Act through this period. The provision for income taxes consists of the following: Years Ended December 31, (in thousands, except for rate) 2017 2016 2015 Current portion of income tax expense: Federal $ 519 $ — $ — State 894 458 20 1,413 458 20 Deferred portion of income tax (benefit) expense: Federal 23,003 (61,396 ) — State (264 ) — — 22,739 (61,396 ) — Total income tax (benefit) expense $ 24,152 $ (60,938 ) $ 20 Effective tax rate 46 % (166 )% — % A reconciliation of expected federal income taxes on income from operations at statutory rates with the expense (benefit) for income taxes is as follows: Years Ended December 31, (in thousands) 2017 2016 2015 Federal statutory rate $ 18,209 $ 12,859 $ (10,542 ) State income taxes, net of federal benefit 1,721 987 (781 ) Permanent differences 777 84 35 Tax credits (1,949 ) (2,419 ) (38,998 ) Valuation allowances (474 ) (72,359 ) 50,066 Changes in tax rates 5,818 (125 ) (243 ) Stock-based compensation 303 36 487 Other (253 ) (1 ) (4 ) Expense (benefit) for the provision for income taxes $ 24,152 $ (60,938 ) $ 20 Deferred income taxes are provided for the effects of temporary differences between the tax basis of an asset or liability and its reported amount in the accompanying Consolidated Balance Sheets. These temporary differences result in taxable or deductible amounts in future years. Details of the Company’s deferred tax assets and liabilities are summarized as follows: As of December 31, (in thousands) 2017 2016 Deferred tax assets Tax credits $ 100,367 $ 99,903 Deferred revenues and loss contract provisions 906 268 Employee related liabilities 393 3,796 Intangible assets 914 1,518 Equity method investments 8,457 12,326 Net operating loss carryforwards 2,004 13,341 Settlement and Royalty Indemnification — 4,264 Other investments 563 680 Other 648 1,429 Total deferred tax assets 114,252 137,525 Less valuation allowance (75,436 ) (75,910 ) Deferred tax assets 38,816 61,615 Less: Deferred tax liabilities Property and equipment and other (155 ) (219 ) Total deferred tax liabilities (155 ) (219 ) Net deferred tax assets $ 38,661 $ 61,396 For 2017 , the Company recorded an income tax expense of $24.2 million compared to an income tax benefit of $60.9 million for 2016 . The income tax expense for the year ended December 31, 2017 was primarily related to federal and state taxes of $19.9 million , plus the aforementioned adjustment related to the Tax Act, which increased the Company's income tax expense by $5.8 million . The income tax benefit for the year ended December 31, 2016 was primarily due to reversals of the valuation allowance of the Company’s net deferred tax assets of $61.4 million . Accounting for income taxes requires that companies assess whether a valuation allowance should be recorded against their deferred tax asset based on an assessment of the amount of the deferred tax asset that is “more likely than not” to be realized. Valuation allowances are established, when necessary, to reduce deferred tax assets to the amount that is more likely than not to be realized. The Company assesses the valuation allowance recorded against deferred tax assets at each reporting date. The determination of whether a valuation allowance for deferred tax assets is appropriate requires the evaluation of positive and negative evidence that can be objectively verified. Consideration must be given to all sources of taxable income available to realize the deferred tax asset, including, as applicable, the future reversal of existing temporary differences, future taxable income forecasts exclusive of the reversal of temporary differences and carryforwards, taxable income in carryback years and tax planning strategies. In estimating taxes, the Company assesses the relative merits and risks of the appropriate tax treatment of transactions taking into account statutory, judicial, and regulatory guidance. As of December 31, 2017 , the Company concluded it is more likely than not the Company will generate sufficient taxable income within the applicable NOL and tax credit carry-forward periods to realize $38.7 million of its net deferred tax assets, and therefore, reversed $0.5 million of the valuation allowance. In reaching this conclusion, the Company most significantly considered: (1) forecasts of continued future taxable income, (2) changes to the current DTA balances related to the effects of the Tax Act, (3) changes to forecasts of future utilization of DTA's related to the effects of the Tax Act, and (4) impacts of additional RC invested facilities during 2017. Prior to 2016, the Company had recorded a valuation allowance for all of its deferred tax assets, primarily due to its historical three-year cumulative loss position. However, as of December 31, 2016, the Company concluded it was more likely than not the Company would generate sufficient taxable income within the applicable NOL and tax credit carry-forward periods to realize $61.4 million of its net deferred tax assets, and therefore, reversed $61.4 million of the valuation allowance, after utilizing $11.0 million during 2016. This conclusion was reached after weighing all of the evidence and determining that the positive evidence outweighed the negative evidence. The positive evidence considered by management in arriving at its conclusion to partially reverse the valuation allowance includes factors such as: (1) emergence from the previous three-year cumulative loss position during the fourth quarter of 2016, (2) completion of four consecutive quarters of profitability and (3) forecasts of continued future profitability. The following table presents the approximate amount of state net operating loss carryforwards and federal tax credit carryforwards available to reduce future taxable income, along with the respective range of years that the net operating loss and tax credit carryforwards would expire if not utilized: As of December 31, (in thousands) 2017 Beginning expiration year Ending expiration year State net operating loss carryforwards $ 41,071 2021 2037 Federal tax credit carryforwards $ 100,367 2031 2037 The following table sets forth a reconciliation of the beginning and ending unrecognized tax benefits on a gross basis for the years ended December 31, 2017 , 2016 and 2015 : Years Ended December 31, (in thousands) 2017 2016 2015 Balance as of January 1 $ 54 $ — $ — Increases for tax positions of current year — 54 — Balance as of December 31 $ 54 $ 54 $ — The Company did not record any adjustments or recognize interest expense for uncertain tax positions for the years ended December 31, 2017 , 2016 and 2015 . Interest and penalties related to uncertain tax positions are accrued and included in the Interest expense line item in the Consolidated Statements of Operations . Additionally, the Company recognizes interest expense related to tax treatment of RC facilities at Tinuum Group in the Interest expense line item in the Consolidated Statements of Operations. Additional information related to these interest amounts is included in Note 10 . The Company files income tax returns in the U.S. and in various states. The Company is no longer subject to U.S. federal examinations by tax authorities for years before 2014 . The Company is generally no longer subject to state examinations by tax authorities for years before 2013

Business Segment Information

Business Segment Information	12 Months Ended
	Dec. 31, 2017
Segment Reporting [Abstract]
Business Segment Information	Business Segment Information Operating segments are defined as components of an enterprise about which separate financial information is available that is evaluated regularly by a company's chief operating decision maker ("CODM"), or a decision making group, in deciding how to allocate resources and in assessing financial performance. As of December 31, 2017 , the Company's CODM was the Company's CEO. The Company's operating and reportable segments are organized by products and services provided. As of December 31, 2016, the Company has two reportable segments: (1) Refined Coal ("RC"); and (2) Emissions Control ("EC"). The business segment measurements provided to and evaluated by the CODM are computed in accordance with the principles listed below: • The accounting policies of the operating segments are the same as those described in the summary of significant accounting policies except as described below. • Segment revenues include equity method earnings and losses from the Company's equity method investments and royalties earned from Tinuum Group and income related to sales-type leases. • Segment operating income (loss) includes segment revenues, gains related to sales of equity method investments and allocation of certain "Corporate general and administrative expenses," which includes Payroll and benefits , Rent and occupancy , Legal and professional fees , and General and administrative . • RC segment operating income includes interest expense directly attributable to the RC segment. As of December 31, 2017 and December 31, 2016 , substantially all of the Company's material assets are located in the U.S. and all significant customers are U.S. companies. The following table presents the Company's operating segment results for the years ended December 31, 2017 , 2016 and 2015 : Years Ended December 31, (in thousands) 2017 2016 2015 Revenues: Refined Coal: Earnings in equity method investments $ 53,843 $ 45,584 $ 8,921 Consulting services — — 55 Royalties, related party 9,672 6,125 10,642 63,515 51,709 19,618 Emissions Control: Equipment sales 31,401 46,949 60,099 Chemicals 4,246 3,025 888 Consulting services 45 648 1,697 35,692 50,622 62,684 Total segment reporting revenues 99,207 102,331 82,302 Adjustments to reconcile to reported revenues: Refined Coal: Earnings in equity method investments (53,843 ) (45,584 ) (8,921 ) Royalties, related party (9,672 ) (6,125 ) (10,642 ) (63,515 ) (51,709 ) (19,563 ) Total reported revenues $ 35,692 $ 50,622 $ 62,739 Segment operating income (loss) Refined Coal (1) $ 59,908 $ 51,264 $ 12,131 Emissions Control (2) 379 7,334 (7,583 ) Total segment operating income $ 60,287 $ 58,598 $ 4,548 (1) Included within the RC segment operating income for the year ended December 31, 2016 is a $2.1 million gain on the sale of RCM6 and for the years ended December 31, 2017 , 2016 and 2015 , 453A interest expense of $2.6 million , $2.5 million and $4.6 million , respectively. Also included within the RC segment operating income for the years ended December 31, 2016 and 2015 is interest expense related to the RCM6 Note Payable of $0.3 million and $2.5 million , respectively. (2) Included within the EC segment operating income for the year ended December 31, 2016 is a $0.9 million gain related to a termination of a sales-type lease. A reconciliation of reportable segment operating income to the Company's consolidated net income is as follows: Years Ended December 31, (in thousands) 2017 2016 2015 Segment operating income Total reported segment operating income $ 60,287 $ 58,598 $ 4,548 Adjustments to reconcile to net income (loss) attributable to the Company Corporate payroll and benefits (5,565 ) (9,415 ) (14,842 ) Corporate rent and occupancy (293 ) (1,187 ) (707 ) Corporate legal and professional fees (4,010 ) (8,230 ) (15,199 ) Corporate general and administrative (3,400 ) (3,811 ) (3,640 ) Corporate depreciation and amortization (342 ) (608 ) (578 ) Corporate interest (expense) income, net (432 ) (2,334 ) 24 Other income (expense), net 5,780 3,727 273 Income tax (expense) benefit (24,152 ) 60,938 (20 ) Net income (loss) $ 27,873 $ 97,678 $ (30,141 ) Corporate general and administrative expenses include certain costs that benefit the business as a whole but are not directly related to one of the Company's segments. Such costs include, but are not limited to, accounting and human resources staff, information systems costs, legal fees, facility costs, audit fees and corporate governance expenses. A reconciliation of reportable segment assets to the Company's consolidated assets is as follows: As of December 31, (in thousands) 2017 2016 Assets: Refined Coal (1) $ 8,092 $ 6,310 Emissions Control 3,755 24,551 Total segment assets 11,847 30,861 All Other and Corporate (2) 70,771 76,435 Consolidated $ 82,618 $ 107,296 (1) Includes $4.4 million of investments in equity method investees. (2) Included within All Other and Corporate are the Company's deferred tax assets.

Major Customers

Major Customers	12 Months Ended
	Dec. 31, 2017
Major Customers Disclosure [Abstract]
Major Customers	Major Customers Revenues from unaffiliated customers who represent 10% or more of the Company’s revenues in for the years ended December 31, 2017 , 2016 and 2015 were as follows: Years Ended December 31, Customer Revenue Type Segment(s) 2017 2016 2015 A Equipment sales EC 62% 21% 3% B Equipment sales, Consulting services EC —% 14% 16% C Consulting services EC —% —% 11% D Equipment sales EC —% —% 15%

Related Party Transactions

Related Party Transactions	12 Months Ended
	Dec. 31, 2017
Related Party Transactions [Abstract]
Related Party Transactions	Related Party Transactions Accounts Receivable The following table shows the Company's receivable balance associated with related parties as of December 31, 2017 and 2016 : As of December 31, (in thousands) 2017 2016 Receivable from related party - Tinuum Group $ 3,247 $ 1,934 Other Income The following table shows the other income recognized with related parties during the years ended December 31, 2017 , 2016 and 2015 : Years Ended December 31, (in thousands) 2017 2016 2015 Royalties, related party - Tinuum Group $ 9,672 $ 6,125 $ 10,642 The above Tinuum Group royalties are included within the Royalties, related party line in the Consolidated Statements of Operations . DSI Business Owner As of December 31, 2014, the Company terminated the consulting portion of the agreements with the DSI Business Owner. However, according to the terms of the remaining agreements, the Company was required to make all remaining payments structured as a note payable (the "DSI Business Owner Note Payable") through the third quarter of 2017. In February 2016, the Company entered into an agreement with the DSI Business Owner and settled the remaining amounts owed under the DSI Business Owner Note Payable as of the date of the agreement of approximately $1.1 million for $0.3 million , which was paid during the first quarter of 2016. The difference between the remaining amounts owed and the settlement amount was included within the Gain on settlement of note payable and licensed technology line item in the Consolidated Statements of Operations for the year ended December 31, 2016 . Highview License As discussed in Note 10 , the Company has an obligation of £0.2 million (approximately $0.2 million ) as a result of the termination of the Highview License, which will only be settled by relinquishing shares of Highview currently owned by the Company equal to £0.2 million . Arch Coal License In June 2010, the Company entered into a Development and License Agreement with Arch Coal, Inc. ("Arch"), a related party as an Arch designee held a Board seat through June 2017, pursuant to which the Company licensed, on an exclusive, non-transferable basis, the use of certain of its technology to enhance coal by a proprietary treatment process. The Company received a non-refundable license fee payment from Arch in the amount of $2.0 million and incurred non-reimbursable costs associated with this agreement in the amount of $ 0.3 million .

Defined Contributions Savings P

Defined Contributions Savings Plan	12 Months Ended
	Dec. 31, 2017
Retirement Benefits [Abstract]
Defined Contributions Savings Plan	Defined Contribution Savings Plan The Company sponsors a qualified defined contribution savings plan (the "401(k) Plan") that allows participation by eligible employees who may defer a portion of their gross pay. The Company makes contributions to the 401(k) Plan based on percentages of an employee's eligible compensation as specified in the 401(k) Plan, and such employer contributions are in the form of cash. The following table presents the amount of the Company' contributions made to the 401(k) Plan, which is reflected within the Payroll and benefits line item in the Consolidated Statements of Operations : Years Ended December 31, (in thousands) 2017 2016 2015 401(k) Plan employer contributions $ 56 $ 172 $ 439 Due to the prior year Restructuring actions discussed in Note 18 as well as usage of forfeitures within the 401(k) Plan, there was a decrease in employer contributions made to the 401(k) Plan for the year ended December 31, 2017 .

Acquisition

Acquisition	12 Months Ended
	Dec. 31, 2017
Business Combinations [Abstract]
Acquisition	Acquisition 2015 Acquisition In March 2015 , the Company acquired the certain assets of InSyst Ltd. and ClearView Monitoring Solutions Ltd. (collectively "ClearView"), to be operated under the Company's wholly-owned subsidiary, ADA Analytics, for total cash payments of $2.4 million , which was inclusive of value-add tax of $0.4 million . The acquisition was accounted for under the acquisition method of accounting, which requires the total purchase consideration to be allocated to the assets acquired and liabilities assumed based on estimates of fair value. Operating results related to the acquired assets were consolidated into the Company’s results of operations beginning March 6, 2015 . A summary of the purchase consideration and allocation of the purchase consideration is as follows: (in thousands) Purchase consideration: Cash paid $ 2,360 Fair value of liabilities assumed: Accrued liabilities 10 Contingent consideration 451 Total fair value of liabilities assumed 461 Total purchase consideration $ 2,821 Allocation of purchase consideration Receivables $ 360 Property and equipment and other 82 Intangibles - in process research and development 2,379 Total $ 2,821 During August 2015, as part of a broader strategic restructuring of the Company's business, the Company’s management approved an action to wind down operations of ADA Analytics. As a result of these actions, the Company fully impaired the carrying value of the assets and reversed the liability for the contingent consideration, thereby recognizing net impairment expense in the amount of $1.9 million during 2015. As disclosed in Note 9 , the impairment expense was included as a component of research and development expense for the year ended December 31, 2015 .

Restructuring

Restructuring	12 Months Ended
	Dec. 31, 2017
Restructuring and Related Activities [Abstract]
Restructuring	Restructuring During the year ended December 31, 2017 , the Company did not record material restructuring charges. During the year ended December 31, 2016 , the Company recorded restructuring charges in connection with a reduction in force, the departure of certain executive officers and management's further alignment of the business with strategic objectives. These charges related to severance arrangements with departing employees and executives as well as non-cash charges related to the acceleration of vesting of certain stock awards. During the year ended December 31, 2015 , the Company recorded restructuring charges in connection with a reduction in force, the departure of executive officers and management's further alignment of the business with strategic objectives. These charges related to severance arrangements with departing employees and executives, including non-cash charges related to the acceleration of vesting of certain stock awards. In 2015, the charges also related to the closing of the Pennsylvania office and fabrication facility and the termination of the operations of ADA Analytics, a foreign subsidiary that was involved in the development of certain data analytics and monitoring products. Furthermore, during the fourth quarter of 2015, the Company closed its fabrication facility in Pennsylvania and recorded restructuring charges related thereto. A summary of the net pretax charges incurred by segment is as follows: Pretax Charge (in thousands, except employee data) Approximate Number of Employees Refined Coal Emissions Control All Other and Corporate Total Year ended December 31, 2016 Restructuring charges 40 $ — $ 1,164 $ 881 $ 2,045 Changes in estimates — (210 ) (276 ) (486 ) Total pretax charge, net of reversals $ — $ 954 $ 605 $ 1,559 Year ended December 31, 2015 Restructuring charges 162 $ — $ 5,108 $ 5,264 $ 10,372 Changes in estimates $ — $ (10 ) $ (2 ) $ (12 ) Total pretax charge, net of reversals $ — $ 5,098 $ 5,262 $ 10,360 The following table summarizes the Company's utilization of restructuring accruals for the years ended December 31, 2017 , 2016 and 2015 : (in thousands) Employee Severance Facility Closures Beginning accrual as of January 1, 2015 $ 1,690 $ — Expense provision (1) 8,498 2,650 Cash payments and other (1) (7,595 ) (1,873 ) Change in estimates (1) (12 ) — Accrual as of December 31, 2015 2,581 777 Expense provision (1) 2,045 — Cash payments and other (1) (3,898 ) (320 ) Change in estimates (1) (276 ) (210 ) Accrual as of December 31, 2016 452 247 Expense provision (1) 56 — Cash payments and other (1) (508 ) (250 ) Change in estimates (1) — 3 Accrual as of December 31, 2017 $ — $ — (1) Included within the Expense provision and Cash payments and other line items in the above table is stock-based compensation of zero , $0.4 million and $3.4 million for the years ended December 31, 2017 , 2016 and 2015 , respectively, resulting from the accelerated vesting of modified equity-based compensation awards for certain terminated employees. Additionally, as discussed in Note 17 , due to restructuring activities the Company fully impaired the carrying value of certain assets, thereby recognizing net impairment expense in the amount of $1.9 million during the year ended December 31, 2015. Restructuring accruals related to personnel are included within the Accrued payroll and related liabilities line item in the Consolidated Balance Sheets . Restructuring expenses related to personnel are included within the Payroll and benefits and Research and development, net line items in the Consolidated Statements of Operations . Restructuring accruals related to facilities are included within the Other current liabilities line item in the Consolidated Balance Sheets . Restructuring expenses related to facilities are included within the Rent and occupancy line item in the Consolidated Statements of Operations .

Quarterly Financial Results (un

Quarterly Financial Results (unaudited)	12 Months Ended
	Dec. 31, 2017
Quarterly Financial Information Disclosure [Abstract]
Quarterly Financial Results (unaudited)	Quarterly Financial Results (unaudited) Summarized quarterly results for the two years ended December 31, 2017 and December 31, 2016 are as follows: For the Quarter Ended (in thousands, except per share data) December 31, 2017 September 30, 2017 June 30, 2017 March 31, 2017 Revenues $ 544 $ 2,294 $ 25,465 $ 7,389 Cost of revenues, exclusive of operating expenses shown below 648 2,041 23,295 5,901 Other operating expenses 4,205 4,197 4,020 5,199 Operating loss (4,309 ) (3,944 ) (1,850 ) (3,711 ) Earnings from equity method investments 17,754 12,120 10,155 13,814 Royalties, related party 3,247 2,804 1,866 1,755 Other income (expenses), net 1,831 (1,602 ) (121 ) 2,216 Income before income tax expense 18,523 9,378 10,050 14,074 Income tax expense 11,538 (1) 3,586 3,642 5,386 Net income $ 6,985 $ 5,792 $ 6,408 $ 8,688 Earnings per common share – basic $ 0.34 $ 0.28 $ 0.29 $ 0.39 Earnings per common share – diluted $ 0.33 $ 0.28 $ 0.29 $ 0.39 Weighted-average number of common shares outstanding Basic 20,767 20,808 21,866 22,056 Diluted 20,864 20,854 21,880 22,243 For the Quarter Ended (in thousands, except per share data) December 31, 2016 September 30, 2016 June 30, 2016 March 31, 2016 Revenues $ 3,604 $ 15,710 $ 8,951 $ 22,357 Cost of revenues, exclusive of operating expenses shown below 3,478 13,259 5,769 17,311 Other operating expenses 5,388 5,364 7,794 8,357 Operating loss (5,262 ) (2,913 ) (4,612 ) (3,311 ) Earnings from equity method investments 15,518 10,735 13,754 5,577 Royalties, related party 2,203 2,064 669 1,189 Other expenses, net 1,698 (2) 309 (1,852 ) 974 Income before income tax expense 14,157 10,195 7,959 4,429 Income tax (benefit) expense (61,673 ) (3) 583 99 53 Net income $ 75,830 $ 9,612 $ 7,860 $ 4,376 Loss per common share – basic $ 3.45 $ 0.44 $ 0.36 $ 0.20 Loss per common share – diluted $ 3.39 $ 0.43 $ 0.35 $ 0.20 Weighted-average number of common shares outstanding Basic 21,693 21,740 21,875 21,849 Diluted 22,061 22,098 22,187 22,177 (1) During the fourth quarter of 2017, the Company recorded an income tax expense of $11.5 million primarily related to statutory federal and state taxes of $5.7 million at the statutory rates, and the impact of the Tax Act, which increased the Company's income tax expense by $ 5.8 million . (2) During the fourth quarter of 2016, the Company revised its estimate for future Royalty Award payments based on an updated forecast provided to the Company from Carbon Solutions. Based primarily on the updated forecast, the Company recorded a $4.0 million reduction to its Royalty Award accrual. (3) During the fourth quarter of 2016, the Company released $ 61.4 million of the valuation allowance related to the deferred tax assets that resulted in an income tax benefit of $61.7 million . See further discussion in Note 12 .

Subsequent Events

Subsequent Events	12 Months Ended
	Dec. 31, 2017
Subsequent Events [Abstract]
Subsequent Events	Subsequent Events Unless disclosed elsewhere within the notes to the Consolidated Financial Statements, the following are the significant matters that occurred subsequent to December 31, 2017. Dividends On February 8, 2018, the Company's Board of Directors declared a quarterly dividend of $0.25 per share of common stock, which was paid on March 8, 2018 to stockholders of record at the close of business on February 21, 2018.

Summary of Operations and Sig27

Summary of Operations and Significant Accounting Policies (Policies)	12 Months Ended
	Dec. 31, 2017
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Principles of Consolidation	The Consolidated Financial Statements include accounts of wholly-owned subsidiaries. All significant intercompany balances and transactions have been eliminated in consolidation. All investments in partially owned entities for which the Company has greater-than-20% ownership are accounted for using the equity method based on the legal form of the Company's ownership percentage and the applicable ownership percentage of the entity and are included in the Equity method investments line item in the Consolidated Balance Sheets . As of December 31, 2017 , the Company holds equity interests of 42.5% , 50.0% and 50.0% in Tinuum Group, Tinuum Services, LLC ("Tinuum Services") and GWN Manager, LLC ("GWN Manager"), respectively. As discussed in Note 2 , the Company purchased its interest in GWN Manager in July 2017 and sold its equity method investment in RCM6, LLC ("RCM6") in March 2016. Tinuum Group is deemed to be variable interest entity ("VIE") under the VIE model of consolidation, but the Company does not consolidate Tinuum Group as it is not deemed to be its primary beneficiary.
Cash and Cash Equivalents and Restricted Cash	Cash and Cash Equivalents Cash and cash equivalents include bank deposits and other highly liquid investments purchased with an original maturity of three months or less. Restricted Cash As of December 31, 2017 , all cash and cash equivalents were unrestricted and all cash requirements for contractual performance guarantees and payments were satisfied under the borrowing availability of the 2013 Loan and Security Agreement ("Line of Credit"). As of December 31, 2016 , restricted cash primarily consisted of funds withheld to provide collateral support for certain letters of credit issued to i) customers related to certain contractual performance and payment guarantees, ii) certain settlement parties to provide security for continuing royalty indemnification payments related to the settlement of certain litigation (the "Royalty Award"), and iii) minimum cash balance requirements under the Line of Credit.
Receivables and Credit Policies	Receivable balances represent unsecured, customer obligations due under trade terms typically requiring payment within 30 - 45 days from the invoice date and are stated net of allowance for doubtful accounts. The Company records allowances for doubtful accounts when it is probable that the accounts receivable balances will not be collected. Notes receivable are reported at their outstanding principal balances, adjusted for any amounts determined to be uncollectible. As of December 31, 2017 and 2016 , the Company had a Note Receivable outstanding in the amount of $1.0 million , which is fully reserved as substantial doubt exists as to collectability. Interest income is accrued and credited to income based on the unpaid principal balance outstanding. The accrual of interest is discontinued when substantial doubt exists about the ability to collect principal and interest based upon the contractual terms. Current portion of notes receivable is included within Prepaid expenses and other assets and long-term portion is included in the Other assets line item in the Consolidated Balance Sheets .
Inventory	Inventories are stated at the lower of cost or market and consist principally of finished goods related to the Company's chemical product offerings. The cost of inventory is determined using the first-in-first-out ("FIFO") method. Inventories are included within the Other assets line item in the Consolidated Balance Sheets .
Other Intangible Assets	Other Intangible assets consist of patents and licensed technology and are included in the Other assets line item in the Consolidated Balance Sheets . The Company has developed technologies resulting in patents being granted by the U.S. Patent and Trademark Office. Legal costs associated with securing the patent are capitalized and amortized over the legal or useful life beginning on the patent filing date. The weighted-average amortization period for the Company's patents is 16 years. All research and development costs associated with the technology development are expensed as incurred.
Investments	The investments in entities in which the Company does not have a controlling interest (financial or operating), but where it has the ability to exercise significant influence over operating and financial policies, are accounted for using the equity method of accounting. Whether or not the Company exercises significant influence with respect to an investee depends on an evaluation of several factors including, among others, representation on the investee company’s board of directors and the Company's ownership level. Under the equity method of accounting, an investee company’s accounts are not reflected within the Company’s Consolidated Balance Sheets and Consolidated Statements of Operations ; however, the Company’s share of the earnings or losses of the investee company is reported in the Earnings from equity method investments line item in the Consolidated Statements of Operations , and the Company’s carrying value in an equity method investee company is reported in the Equity method investments line in the Consolidated Balance Sheets . When the Company receives distributions in excess of the carrying value of the investment and has not guaranteed any obligations of the investee, nor is it required to provide additional funding to the investee, the Company recognizes such excess distributions as equity method earnings in the period the distributions occur. When the investee subsequently reports income, the Company does not record its share of such income until it equals the amount of distributions in excess of carrying value that were previously recognized in income. During the years ended December 31, 2017 , 2016 and 2015 , the Company had no guarantees or requirements to provide additional funding to investees. Additionally, when the Company's carrying value in an equity method investment is zero and the Company has not guaranteed any obligations of the investee, nor is it required to provide additional funding to the investee, the Company will not recognize its share of any reported losses by the investee until future earnings are generated to offset previously unrecognized losses. As a result, equity income or loss reported on the Company's Consolidated Statements of Operations for certain equity method investees may differ from a mathematical calculation of net income or loss attributable to its equity interest based upon the percentage ownership of the Company's equity interest and the net income or loss attributable to equity owners as shown on investee company's statements of operations. Likewise, distributions from equity method investees are reported on the Consolidated Statements of Cash Flows as “return on investment” within Operating cash flows until such time as the carrying value in an equity method investee company is reduced to zero; thereafter, such distributions are reported as “distributions in excess of cumulative earnings” within Investing cash flows.
Royalties, related party	The Company licenses its M-45 TM and M-45-PC TM emission control technologies ("M-45 License") to Tinuum Group and realizes royalty income based upon a percentage of the per-ton, pre-tax margin as defined in the M-45 License.
Property and Equipment	Property and equipment is stated at cost less accumulated depreciation and includes leasehold improvements. Depreciation on assets is computed using the straight-line method over the lesser of the estimated useful lives of the related assets or the lease term (ranging from 2 to 7 years). Maintenance and repairs that do not extend the useful life of the respective asset are charged to Operating expenses as incurred. When assets are retired, or otherwise disposed of, the property accounts are relieved of costs and accumulated depreciation and any resulting gain or loss is credited or charged to income. The Company performs an evaluation of the recoverability of the carrying value of its long-lived assets to determine if facts and circumstances indicate that the carrying value of assets may be impaired and if any adjustment is warranted.
Revenue Recognition	The Company recognizes revenues when: (i) persuasive evidence of a customer arrangement exists; (ii) the price is fixed or determinable; (iii) collectability is reasonable assured; and (iv) product delivery has occurred or services have been rendered and it is probable that performance guarantees, if any, will be met. Equipment sales The Company has entered into construction-type contracts that entail the design and construction of emissions control systems ("extended equipment contracts"). Revenues from such extended equipment contracts are recorded using the percentage of completion cost to cost method based on costs incurred to date compared with total estimated contract costs. However, if the Company does not have sufficient information to estimate either costs incurred or total estimated costs for extended equipment contracts at the time contracts are entered into, the completed contract method is used. For all of its Dry Sorbent Injection ("DSI") contracts, the Company has used the completed contract method from inception of the contract to recognize revenues and related cost of revenue. Under the completed contract method, revenues and costs from extended equipment contracts are deferred and recognized when contract obligations are substantially complete. The Company defines substantially complete as delivery of equipment and start-up at the customer site or, as applicable to DSI systems, the completion of any major warranty service period. For each of the years ended December 31, 2017 , 2016 and 2015 , the Company did not have sufficient information to measure ongoing performance for its extended equipment contracts. Accordingly, the completed contract method of revenue recognition has been used for each of these years, and revenues and costs are deferred until the equipment is placed into service and contract obligations are substantially complete. For the years ended December 31, 2017 and 2016 , the Company did not enter into any extended equipment contracts. Deferred revenue and related costs are accumulated in the Costs in excess of billings on uncompleted contracts or Billings in excess of costs on uncompleted contracts line items in the Consolidated Balance Sheets , and typically include direct materials, direct labor and subcontractor costs, and indirect costs related to contract performance, such as indirect labor, supplies, tools and repairs. When multiple contracts exist with a single counterparty, the Company evaluates revenue recognition on a contract-by-contract basis. Provisions for estimated losses on uncompleted contracts are recognized when it has been determined that a loss is probable. The Company also enters into other non-extended equipment contracts for which the Company recognizes revenues as services to build equipment systems are performed or as equipment is delivered. Chemicals Revenues for direct sales of chemicals are recognized at the date of delivery to, and acceptance by, the customer. Certain chemicals customer contracts are comprised of evaluation tests of the Company's chemicals' effectiveness and efficiency in reducing emissions and entail the delivery of chemicals to the customer and the Company evaluating results of emissions reduction over the term of the contract. The Company generally recognizes revenue from these types of contracts over the duration of the contract based on the cost of chemicals consumed by the customer. Consulting services and other The Company recognizes revenues on time and material contracts as services are performed.
Cost of Revenues	Costs of revenue include all labor, fringe benefits, subcontract labor, chemical and coal costs, materials, equipment, supplies, travel costs and any other costs and expenses directly related to the Company’s production of revenues. The Company records estimated contract losses, if any, in the period they are determined.
Warranty Costs	Warranty costs for Activated Carbon Injection ("ACI") equipment systems are estimated based on historical experience and are recorded as a percentage of revenue when the equipment is substantially complete. Warranty costs, comprised of the cost of replacement materials and direct labor, are included within the Equipment sales cost of revenue line in the Consolidated Statements of Operations . Warranty costs for DSI equipment systems have not been estimable at the time the contracts were entered into, as the Company lacked historical experience in manufacturing DSI systems and was unable to reasonably estimate costs to complete as well as warranty claims. Therefore, revenue recognition on DSI equipment systems has been deferred until the end of the warranty period, which has generally been 12 to 24 months following substantial completion. As warranty claims are incurred, such costs are deferred within the Costs in excess of billings on uncompleted contracts line item in the Consolidated Balance Sheets , until such time that revenues and cost of revenue are recognized. Subsequent to revenues being recognized, warranty claims are included within the Other long-term liabilities line item in the Consolidated Balance Sheets and within Cost of revenue line of the Consolidated Statements of Operations . The changes in the carrying amount of the Company’s warranty obligations, which do not include amounts for DSI systems as revenues, are deferred until the end of the warranty period, and are disclosed in Note 10 .
Expenses	Payroll and Benefits Payroll and benefits costs include direct payroll, personnel related fringe benefits, sales and administrative staff labor costs and stock compensation expense. Payroll and benefits costs exclude direct labor included in Cost of revenue. Rent and Occupancy Rent and occupancy costs include rent, insurance and other occupancy-related expenses. Legal and Professional Legal and professional costs include external legal, audit and consulting expenses. General and Administrative General and administrative costs include director fees and expenses, bad debt expense, impairments and other general costs of conducting business.
Research and Development Costs	Research and development costs are charged to expense in the period incurred. Research and development expense consists of research relating to continued product development for the Company's ongoing business and various other projects including the CO 2 capture and control market. The Company historically entered into development and cost-sharing contracts with the U.S. Department of Energy (the "DOE"). These contracts were best-effort-basis contracts, and the Company generally included industry cost-share partners to offset the costs incurred that are anticipated to be in excess of funded amounts from the DOE. The Company accounts for these contracts with the DOE and industry cost-share partners by recognizing amounts funded by the DOE under research-and-development-cost-sharing arrangements as an offset to research and development expense, which is reported in the Research and development, net line in the Consolidated Statements of Operations .
Asset Retirement Obligations	Asset retirement obligations, or "ARO liabilities," consist of estimated costs to remove equipment and reclaim the land associated with one research and development project. The Company estimates ARO liabilities for final reclamation based upon bids obtained from independent third parties and other exit alternatives, which are adjusted for inflation and then discounted at a credit-adjusted risk-free rate. Changes in estimates could occur due to revisions of estimated costs and changes in timing and performance of the reclamation activities.
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 on the basis of the differences between the financial statements and tax basis of assets and liabilities using enacted tax rates in effect for the year in which the differences are expected to reverse. The effect of a change in tax rates on deferred tax assets and liabilities is recognized in operations in the period that includes the enactment date. The Company recognizes deferred tax assets and liabilities and maintains valuation allowances where it is more likely than not that all or a portion of deferred tax assets will 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. The Company records uncertain tax positions on the basis of a two-step process whereby (1) the Company determines whether it is more-likely-than-not that the tax positions will be sustained on the basis of the technical merits of the position and (2) for those tax positions that meet the more-likely-than-not recognition threshold, the Company recognizes the amount of tax benefit that is more than 50 percent likely to be realized upon ultimate settlement with the related tax authority. The Company records interest expense due to the Company's share of Tinuum Group's equity method earnings for Refined Coal ("RC") facilities, in which the lease income or sale is treated as installment sales for tax purposes. IRS section 453A requires taxpayers using the installment method to pay an interest charge on the portion of the tax liability that is deferred under the installment method. The Company recognizes IRS section 453A interest ("453A interest") and other interest and penalties related to unrecognized tax benefits in the Interest expense line item in the Consolidated Statements of Operations .
Stock-Based Compensation	Stock-based compensation expense is measured at the grant date based on the estimated fair value of the stock-based award and is generally expensed on a straight-line basis over the requisite service period and/or performance period of the award. Forfeitures are recognized when incurred. These costs are recorded in the Payroll and benefits or General and administrative , for director related expense, line items in the Consolidated Statements of Operations .
Earnings (Loss) Per Share	Basic earnings (loss) per share is computed using the two-class method, which is an earnings allocation formula that determines earnings (loss) per share for common stock and any participating securities according to dividend and participating rights in undistributed earnings. The Company's restricted stock awards ("RSA's") granted prior to December 31, 2016 contain non-forfeitable rights to dividends or dividend equivalents and are deemed to be participating securities. RSA's granted subsequent to December 31, 2016 do not contain non-forfeitable rights to dividends and are not deemed to be participating securities. Under the two-class method, net income (loss) for the period is allocated between common stockholders and the holders of the participating securities based on the weighted-average of common shares outstanding during the period, excluding participating, unvested RSA's ("common shares"), and the weighted-average number of participating, unvested RSA's outstanding during the period, respectively. The allocated, undistributed income for the period is then divided by the weighted-average number of common shares and participating, unvested RSA's outstanding during the period to determine basic earnings per common share and participating security for the period, respectively. Pursuant to accounting principles generally accepted in the United States ("U.S. GAAP"), the Company has elected not to separately present basic or diluted earnings per share attributable to participating securities in the Consolidated Statements of Operations. Diluted earnings per share is computed in a manner consistent with that of basic earnings per share, while considering other potentially dilutive securities. Potentially dilutive securities consist of both unvested, participating and non-participating RSA's, as well as outstanding options to purchase common stock ("Stock Options") and contingent performance stock units ("PSU's") (collectively, "Potential dilutive shares"). The dilutive effect, if any, for non-participating RSA's, Stock Options and PSU's is determined using the greater of dilution as calculated under the treasury stock method or the two-class method. Potential dilutive shares are excluded from diluted earnings (loss) per share when their effect is anti-dilutive. When there is a net loss for a period, all Potential dilutive shares are anti-dilutive and are excluded from the calculation of diluted loss per share for that period. Each PSU represents a contingent right to receive shares of the Company’s common stock, and the number of shares may range from zero to two times the number of PSU's granted on the award date depending upon the price performance of the Company's common stock as measured against a general index and a specific peer group index over requisite performance periods. The number of Potential dilutive shares related to PSU's is based on the number of shares of the Company's common stock, if any, that would be issuable at the end of the respective reporting period, assuming that the end of the reporting period is the end of the contingency period applicable to such PSU's. See Note 6 for additional information related to PSU's.
Use of Estimates	The preparation of the Company’s consolidated financial statements in conformity with U.S. GAAP requires the Company’s management to make estimates and assumptions that affect the amounts reported in these financial statements and accompanying notes. Actual results could differ from those estimates. The Company makes assumptions on the following significant financial statement components including: • revenue recognition and warranty estimates accruals related to the Company's extended equipment contracts; • the carrying value of its long-lived assets; • the allowance for doubtful accounts receivable; • stock compensation costs; • estimates related to future obligations, including the Royalty Award, and other legal accruals; and • income taxes, including the valuation allowance for deferred tax assets and uncertain tax positions.
Risks and Uncertainties	The Company’s earnings are significantly affected by equity earnings it receives from Tinuum Group. Tinuum Group has 17 invested RC facilities of which 11 are leased to a single customer. A majority of these leases are periodically renewed and the loss of this customer by Tinuum Group would have a significant adverse impact on its financial position, results of operations and cash flows, which in turn would have material adverse impact on the Company’s financial position, results of operations and cash flows. Concentration of credit risk As of December 31, 2017 , the Company’s financial instruments that are exposed to concentrations of credit risk consist primarily of cash and cash equivalents. The Company holds cash and cash equivalents at one financial institution as of December 31, 2017. If that institution was to be unable to perform its obligations, the Company would be at risk regarding the amount of investment in excess of the federal deposit insurance corporation limits ( $250 thousand ) that would be returned to the Company.
Reclassifications	Certain balances have been reclassified from prior years to conform to the current year presentation.
New Accounting Guidance	In May 2014, the FASB issued ASU No. 2014-09, Revenue from Contracts with Customers (Topic 606) ("ASU 2014-09"), which provides a single comprehensive model for entities to use in accounting for revenue arising from contracts with customers and supersedes current revenue recognition guidance, including industry-specific guidance. The core principle of ASU 2014-09 is that “an entity recognizes revenue to depict the transfer of promised goods or services to customers in an amount that reflects the consideration to which the entity expects to be entitled in exchange for those goods or services. ASU 2014-09 and its related amendments are effective for reporting periods (including interim periods) beginning after December 31, 2017. The standard may be applied retrospectively to each prior period presented or retrospectively with the cumulative effect recognized as of the date of adoption ("modified retrospective method"). The Company will adopt the standard under the modified retrospective method effective January 1, 2018, which will be reflected in its financial statements as of and for the three months ended March 31, 2018. As of the date of this filing, the Company has completed its assessment of ASU 2014-09 for the impact to the financial statements as of the adoption date, completed a detailed review of individual customer contracts, completed its review of controls and procedures that will be revised or added from the adoption of the standard, and completed its documentation of the standard's financial statement impact at adoption, financial statement presentation and disclosure changes and changes to existing revenue recognition policies, controls and procedures. As of the adoption date of ASU 2014-09, the Company has determined that deferred revenue and deferred project costs on uncompleted contracts as of December 31, 2017 related to equipment sales projects will be derecognized through a cumulative effect adjustment, which will reduce the opening balance of the Accumulated deficit in the amount of approximately $1.7 million , net of income taxes. In addition, as of the adoption date, the Company will also derecognize deferred revenue and deferred project costs as of December 31, 2017 for a technology licensing arrangement through a cumulative effect adjustment, which will reduce the Accumulated deficit in the amount of approximately $1.3 million , net of income taxes. Except for the reclassification of the Company's royalties received from related parties from Other income to Revenue, the Company expects that there will be no material financial statement impact as of the adoption date from other uncompleted contracts. In January 2016, the FASB issued ASU 2016-01, Financial Instruments (Subtopic 825-10) - Overall: Recognition and Measurement of Financial Assets and Financial Liabilities ("ASU 2016-01"). This standard provides guidance on how entities measure certain equity investments and present changes in the fair value. This standard requires that entities measure certain equity investments that do not result in consolidation and are not accounted for under the equity method at fair value and recognize any changes in fair value in net income. ASU 2016-01 is effective for fiscal years beginning after December 31, 2017. The Company is currently evaluating the provisions of this guidance and assessing its impact on the Company's financial statements and disclosures. The Company does not believe this standard will have a material impact on the Company's financial statements and disclosures. In February 2016, the FASB issued ASU 2016-02, Leases (Topic 842) ("ASU 2016-02"), which requires lessees to recognize a right of use asset and related lease liability for those leases classified as operating leases at the commencement date and have lease terms of more than 12 months. This topic retains the distinction between finance leases and operating leases. ASU 2016-02 is effective for fiscal years beginning after December 15, 2018, and interim periods within those years, and must be applied under a modified retrospective transition approach for leases existing at, or entered into after, the beginning of the earliest comparative period presented in the financial statements. The Company is currently evaluating the provisions of this guidance and assessing its impact on the Company's financial statements and disclosures. In June 2016, the FASB issued ASU 2016-13, Financial Instruments - Credit Losses (Topic 326) Measurement of Credit Losses on Financial Instruments ("ASU 2016-13"). The main objective of ASU 2016-13 is to provide financial statement users with more decision-useful information about the expected credit losses on financial instruments and other commitments to extend credit held by a reporting entity at each reporting date. To achieve this objective, the amendments in ASU 2016-13 replace the incurred loss impairment methodology in current U.S. GAAP with a methodology that reflects expected credit losses and requires consideration of a broader range of reasonable and supportable information to inform credit loss estimates. ASU 2016-13 is effective for fiscal years beginning after December 15, 2019, including interim periods within those years, and must be adopted under a modified retrospective method approach. Entities may adopt ASU 2016-13 earlier as of the fiscal years beginning after December 15, 2018, including interim periods within those years. The Company is currently evaluating the provisions of this guidance and assessing its impact on the Company's financial statements and disclosures. The Company does not believe this standard will have a material impact on the Company's financial statements and disclosures.
Fair Value of Financial Instruments	The carrying amounts of financial instruments, including cash and cash equivalents, accounts receivable, accounts payable, deposits and accrued expenses, approximate fair value due to the short maturity of these instruments.
Segment Reporting	Corporate general and administrative expenses include certain costs that benefit the business as a whole but are not directly related to one of the Company's segments. Such costs include, but are not limited to, accounting and human resources staff, information systems costs, legal fees, facility costs, audit fees and corporate governance expenses. Operating segments are defined as components of an enterprise about which separate financial information is available that is evaluated regularly by a company's chief operating decision maker ("CODM"), or a decision making group, in deciding how to allocate resources and in assessing financial performance. As of December 31, 2017 , the Company's CODM was the Company's CEO. The Company's operating and reportable segments are organized by products and services provided. As of December 31, 2016, the Company has two reportable segments: (1) Refined Coal ("RC"); and (2) Emissions Control ("EC"). The business segment measurements provided to and evaluated by the CODM are computed in accordance with the principles listed below: • The accounting policies of the operating segments are the same as those described in the summary of significant accounting policies except as described below. • Segment revenues include equity method earnings and losses from the Company's equity method investments and royalties earned from Tinuum Group and income related to sales-type leases. • Segment operating income (loss) includes segment revenues, gains related to sales of equity method investments and allocation of certain "Corporate general and administrative expenses," which includes Payroll and benefits , Rent and occupancy , Legal and professional fees , and General and administrative . • RC segment operating income includes interest expense directly attributable to the RC segment

Summary of Operations and Sig28

Summary of Operations and Significant Accounting Policies (Tables)	12 Months Ended
	Dec. 31, 2017
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Schedule of Receivables	The following tables show the receivables balances: As of December 31, (in thousands) 2017 2016 Trade receivables $ 1,240 $ 4,289 Less: Allowance for doubtful accounts (127 ) (200 ) Trade receivables, net 1,113 4,089 Other receivables (1) — 4,559 Total $ 1,113 $ 8,648 (1) As of December 31, 2016 , Other receivables included settlement amounts subsequently funded by the Company's insurance carriers for legal proceedings described in Note 4 .
Calculations of Basic and Diluted Earnings Per Share	The following table sets forth the calculations of basic and diluted earnings (loss) per common share: Years Ended December 31, (in thousands, except per share amounts) 2017 2016 2015 Net income (loss) $ 27,873 $ 97,678 $ (30,141 ) Less: Dividends and undistributed income (loss) allocated to participating securities 171 1,105 (275 ) Income (loss) attributable to common stockholders $ 27,702 $ 96,573 $ (29,866 ) Basic weighted-average number of common shares outstanding 21,367 21,931 21,773 Add: dilutive effect of equity instruments 46 303 — Diluted weighted-average shares outstanding 21,413 22,234 21,773 Earnings (loss) per share - basic $ 1.30 $ 4.40 $ (1.37 ) Earnings (loss) per share - diluted $ 1.29 $ 4.34 $ (1.37 )

Equity Method Investments (Tabl

Equity Method Investments (Tables)	12 Months Ended
	Dec. 31, 2017
Equity Method Investments and Joint Ventures [Abstract]
Equity Method Investments	The following table details the carrying value of the Company's respective equity method investments included within the Equity method investments line item on the Consolidated Balance Sheets and indicates the Company's maximum exposure to loss: As of December 31, (in thousands) 2017 2016 Equity method investment in Tinuum Group $ — $ — Equity method investment in Tinuum Services 4,284 3,959 Equity method investment in other 67 — Total equity method investments $ 4,351 $ 3,959 The following table presents the Company's investment balance, equity earnings, cash distributions and cash distributions in excess of the investment balance for the years ended December 31, 2015 through December 31, 2017 ( in thousands ): Description Date(s) Investment balance ADES equity earnings (loss) Cash distributions Memorandum Account: Cash distributions and equity loss in (excess) of investment balance Beginning balance 12/31/2014 $ — $ — $ — $ (29,877 ) ADES proportionate share of net income from Tinuum Group (1) 2015 activity 35,265 35,265 — — Recovery of cash distributions in excess of investment balance (prior to cash distributions) 2015 activity (29,877 ) (29,877 ) — 29,877 Cash distributions from Tinuum Group 2015 activity (8,651 ) — 8,651 — Adjustment for current year cash distributions in excess of investment balance 2015 activity 3,263 3,263 — (3,263 ) Total investment balance, equity earnings (loss) and cash distributions 12/31/2015 $ — $ 8,651 $ 8,651 $ (3,263 ) ADES proportionate share of net income from Tinuum Group (1) 2016 activity $ 35,019 $ 35,019 $ — $ — Recovery of cash distributions in excess of investment balance (prior to cash distributions) 2016 activity (3,263 ) (3,263 ) — 3,263 Cash distributions from Tinuum Group 2016 activity (41,650 ) — 41,650 — Adjustment for current year cash distributions in excess of investment balance 2016 activity 9,894 9,894 — (9,894 ) Total investment balance, equity earnings (loss) and cash distributions 12/31/2016 $ — $ 41,650 $ 41,650 $ (9,894 ) ADES proportionate share of net income from Tinuum Group (1) 2017 activity $ 46,551 $ 46,551 $ — $ — Recovery of cash distributions in excess of investment balance (prior to cash distributions) 2017 activity (9,894 ) (9,894 ) — 9,894 Cash distributions from Tinuum Group 2017 activity (48,875 ) — 48,875 — Adjustment for current year cash distributions in excess of investment balance 2017 activity 12,218 12,218 — (12,218 ) Total investment balance, equity earnings and cash distributions 12/31/2017 $ — $ 48,875 $ 48,875 $ (12,218 ) (1) The amounts of the Company's 42.5% proportionate share of net income as shown in the table above differ from mathematical calculations of the Company’s 42.5% equity interest in Tinuum Group multiplied by the amounts of Net Income available to Class A members as shown in the table above of Tinuum Group's results of operations due to adjustments related to the Class B preferred return and the elimination of Tinuum Group's earnings attributable to RCM6, of which the Company owned 24.95% during the year ended December 31, 2015 and for the period from January 1 through March 3, 2016. As noted below, the Company sold its interest in RCM6 on March 3, 2016. The following tables summarize the assets, liabilities and results of operations of Tinuum Group: As of December 31, (in thousands) 2017 2016 Current assets $ 31,068 $ 24,584 Non-current assets $ 75,592 $ 83,621 Current liabilities $ 48,280 $ 43,117 Non-current liabilities $ 8,350 $ 11,456 Redeemable Class B equity $ 821 $ 18,250 Members equity attributable to Class A members $ 40,452 $ 26,475 Noncontrolling interests $ 8,757 $ 8,907 Years Ended December 31, (in thousands) 2017 2016 2015 Gross profit $ 95,552 $ 92,305 $ 108,416 Operating, selling, general and administrative expenses 22,958 23,662 23,405 Income from operations 72,594 68,643 85,011 Other expenses (4,520 ) (8,775 ) (2,203 ) Class B preferred return (1,712 ) (3,901 ) (6,157 ) Loss attributable to noncontrolling interest 43,474 27,234 10,675 Net income available to Class A members $ 109,836 $ 83,201 $ 87,326 ADES equity earnings from Tinuum Group $ 48,875 $ 41,650 $ 8,651 The following tables summarize the assets, liabilities and results of operations of Tinuum Services: As of December 31, (in thousands) 2017 2016 Current assets $ 546,681 $ 278,001 Non-current assets $ 98,640 $ 3,426 Current liabilities $ 178,376 $ 97,093 Non-current liabilities $ 75,717 $ 1,488 Equity $ 8,569 $ 7,918 Noncontrolling interests $ 382,659 $ 174,928 Years Ended December 31, (in thousands) 2017 2016 2015 Gross loss $ (64,796 ) $ (54,644 ) $ (42,496 ) Operating, selling, general and administrative expenses 147,917 134,782 161,456 Loss from operations (212,713 ) (189,426 ) (203,952 ) Other expenses (68 ) (56 ) (118 ) Loss attributable to noncontrolling interest 222,707 198,464 213,746 Net income $ 9,926 $ 8,982 $ 9,676 ADES equity earnings from Tinuum Services $ 4,963 $ 4,491 $ 4,838 The following table details the components of the Company's respective earnings or loss from equity method investments included within the Earnings from equity method investments line item on the Consolidated Statements of Operations : Year ended December 31, (in thousands) 2017 2016 2015 Earnings from Tinuum Group $ 48,875 $ 41,650 $ 8,651 Earnings from Tinuum Services 4,963 4,491 4,838 Earnings (losses) from other 5 (557 ) (4,568 ) Earnings from equity method investments $ 53,843 $ 45,584 $ 8,921 The following table details the components of the cash distributions from the Company's respective equity method investments included within the Consolidated Statements of Cash Flows . Distributions from equity method investees are reported on the Consolidated Statements of Cash Flows as “return on investment” within Operating cash flows until such time as the carrying value in an equity method investee company is reduced to zero ; thereafter, such distributions are reported as “distributions in excess of cumulative earnings” within Investing cash flows. Year ended December 31, (in thousands) 2017 2016 2015 Distributions from equity method investees, return on investment Tinuum Group (1) $ — $ 3,400 $ — Tinuum Services 4,638 4,500 5,019 Included in Operating Cash Flows $ 4,638 $ 7,900 $ 5,019 Distributions from equity method investees in excess of cumulative earnings Tinuum Group $ 48,875 $ 38,250 $ 8,651 Included in Investing Cash Flows $ 48,875 $ 38,250 $ 8,651 (1) During the three months ended March 31, 2016, the Company's cumulative share of pro-rata Tinuum Group's net income available to Class A members exceeded the amount of its cumulative earnings recognized due to cash being distributed. As such, the Company recognized $3.4 million as "return on investment."

Borrowings (Tables)

Borrowings (Tables)	12 Months Ended
	Dec. 31, 2017
Debt Disclosure [Abstract]
Schedule of Borrowings	The following tables summarize the LC's outstanding and collateral, by asset type, reported on the Consolidated Balance Sheets: As of December 31, 2017 (in thousands) LC Outstanding Utilization of LOC Availability Restricted Cash Royalty Award (1) $ 3,500 $ 3,500 $ — Total LC outstanding $ 3,500 $ 3,500 $ — (1) As further discussed in Note 4 , the Company settled the liability related to the Royalty Award on December 29, 2017. The Company and other parties associated with the LC, executed the termination of the LC in January 2018. As of December 31, 2016 (in thousands) LC Outstanding Utilization of LOC Availability Restricted Cash Contract performance - equipment systems $ 1,855 $ 1,776 $ 86 Royalty Award 7,150 — 7,150 Other 6,500 — 6,500 Total LC outstanding $ 15,505 $ 1,776 $ 13,736 The following tables summarizes the expiration periods of the LC's based on the ultimate maturity date of the LC's as of December 31, 2017 : Expiration of Letters of Credit as of December 31, 2017 (in thousands) Less than 1 year 1-3 years 4-5 years After 5 years LC's $ 3,500 $ — $ — $ —

Commitments and Contingencies (

Commitments and Contingencies (Tables)	12 Months Ended
	Dec. 31, 2017
Commitments and Contingencies Disclosure [Abstract]
Settlement and Royalty Indemnity Obligation	The following table summarizes the Company's legal settlements and accruals as described above, which are presented in the Consolidated Balance Sheets : As of December 31, (in thousands) 2017 2016 Settlement and Royalty Indemnification $ — $ 5,656 Legal settlements — 5,050 Legal settlements and accruals, current — 10,706 Settlement and Royalty Indemnification, long-term — 5,382 Total legal settlements and accruals $ — $ 16,088
Schedule of Future Minimum Rental Payments for Operating Leases	Annual minimum commitments under the leases as of December 31, 2017 are as follows: Years Ending December 31, Operating Lease Commitments (in thousands) 2018 $ 298 2019 205 2020 82 2021 — Thereafter — Total $ 585
Schedule of Rent Expense	Rent expense incurred for the years ended is as follows: Years Ended December 31, (in thousands) 2017 2016 2015 Rent expense (1) $ (60 ) $ 847 $ 1,838 (1) During the year ended December 31, 2017 , the Company accelerated deferred rent and tenant improvement allowances in connection with the termination of the lease agreement of its former corporate office.

Stockholders' Equity (Tables)

Stockholders' Equity (Tables)	12 Months Ended
	Dec. 31, 2017
Equity [Abstract]
Schedule of Dividends Declared	Dividends declared and paid quarterly per share on all outstanding shares of common stock during the year ended December 31, 2017 were as follows: 2017 Per share Date paid Dividends declared during quarter ended: June 30 $ 0.25 July 17, 2017 September 30 0.25 September 7, 2017 December 31 0.25 December 6, 2017 $ 0.75

Stock-Based Compensation (Table

Stock-Based Compensation (Tables)	12 Months Ended
	Dec. 31, 2017
Disclosure of Compensation Related Costs, Share-based Payments [Abstract]
Stock Option Valuation Assumptions	The following table indicates the weighted-average assumptions that were used related to the stock options granted for the years ended December 31, 2016 and 2015 , respectively. No stock options were granted during the year ended December 31, 2017 . Years Ended December 31, 2016 2015 Stock options granted: Risk-free interest rate 1.3 % 1.8 % Dividend yield — % — % Volatility 78.8 % 74.5 % Expected term (in years) 2.6 5.0
Equity Instruments, Other than Options, Valuation Assumptions	The following table indicates the weighted-average assumptions that were used related to the awards granted for the year ended December 31, 2015 . No SAR's were granted during the year ended December 31, 2017 or 2016 . Year ended December 31, 2015 SAR's granted: Risk-free interest rate 1.8 % Dividend yield — % Volatility 74.5 % Expected term (in years) 5.0 The following table indicates the weighted-average assumptions that were used related to the awards granted for the year ended December 31, 2015 . No PSU's were granted during the years ended December 31, 2017 or 2016 . Year Ended December 31, 2015 PSUs granted: Risk-free interest rate 1.0 % Dividend yield — % Volatility 64.3 % Performance period (in years) 3.0
Allocation of Compensation Expense	The Company recorded the following compensation expense related to the Stock Plans and the 2007 Plan: Years Ended December 31, (in thousands) 2017 2016 2015 RSA expense $ 1,400 $ 2,021 $ 2,909 Stock option expense 672 285 658 SAR expense — 106 742 PSU expense 137 456 2,895 Total stock-based compensation expense $ 2,209 $ 2,868 $ 7,204
Schedule of Unrecognized Compensation Cost	The amount of unrecognized compensation cost as of December 31, 2017 , and the expected weighted-average period over which the cost will be recognized is as follows: As of December 31, 2017 (in thousands) Unrecognized Compensation Cost Expected Weighted-Average Period of Recognition (in years) RSA expense $ 1,735 1.93 Stock option expense 58 0.25 PSU expense — 0 Total unrecognized stock-based compensation expense $ 1,793 1.88
Summary of Restricted Stock Activity	A summary of the status and activity of non-vested RSA's is presented in the following table: For the Years Ended December 31. 2017 2016 2015 (in thousands, except for share and per share amounts) Shares Weighted- Shares Weighted-Average Shares Weighted-Average Non-vested at beginning of year 297,347 $ 8.03 134,708 $ 8.49 209,921 $ 13.59 Granted 191,076 $ 9.50 363,758 $ 7.46 127,943 $ 14.97 Vested (210,129 ) $ 8.03 (175,956 ) $ 11.96 (165,796 ) $ 17.51 Forfeited (1) (1,687 ) $ 9.17 (25,163 ) $ 15.58 (37,360 ) $ 19.30 Non-vested at end of year 276,607 $ 9.03 297,347 $ 8.03 134,708 $ 8.49 (1) Included within the 2015 forfeited / canceled units are RSA's related to a former executive that were clawed back. The Company recognized $0.1 million within Other Income line item on the Consolidated Statement of Operations related to these awards.
Summary of Option Activity	A summary of option activity under the Plans is presented below: (in thousands, except for share and per share amounts) Number of Weighted- Aggregate Intrinsic Value Weighted- For the year ended December 31, 2015 Options outstanding, January 1, 2015 74,200 $ 13.76 Options granted 56,250 $ 13.87 Options exercised — $ — Options expired / forfeited (24,200 ) $ 7.59 Options outstanding, December 31, 2015 106,250 $ 15.22 $ — 3.8 Options vested and exercisable, December 31, 2015 82,915 $ 14.04 $ — 3.9 For the year ended December 31, 2016 Options outstanding, January 1, 2016 106,250 $ 15.22 Options granted (1) 546,196 $ 11.10 Options exercised — $ — Options expired / forfeited (20,000 ) $ 16.90 Options outstanding, December 31, 2016 632,446 $ 11.61 $ 183 4.0 Options vested and exercisable, December 31, 2016 247,780 $ 13.30 $ 69 3.4 For the year ended December 31, 2017 Options outstanding, January 1, 2017 632,446 $ 11.61 Options granted — $ — Options exercised — $ — Options expired / forfeited (10,000 ) $ 9.77 Options outstanding, December 31, 2017 622,446 $ 11.64 $ 119 2.24 Options vested and exercisable, December 31, 2017 429,780 $ 11.47 $ 119 2.03 (1) Included in options granted are 243,750 awards granted that were initially granted on a contingent basis and became exercisable as a result of the automatic expiration of the same number of SAR's, as a result of stockholder approval of Amendment No. 4 of the 2007 Plan. See "SAR's" section below for a discussion of the provisions of the exchange and incremental expense recognized.
Schedule of Equity Instruments, Other than Options Activity	A summary of the status and activity of non-vested PSU's is presented in the following table: For the Years Ended December 31. 2017 2016 2015 (in thousands, except for unit and per unit amounts) Units Weighted-Average Units Weighted-Average Units Weighted-Average Non-vested at beginning of year 49,516 $ 25.20 169,334 $ 26.38 142,357 $ 30.65 Granted (1) — $ — — $ — 69,218 $ 20.10 Vested (1) (30,110 ) $ 26.87 (119,818 ) $ 26.87 (13,763 ) $ 30.52 Forfeited / Canceled (1) (2) — $ — — $ — (28,478 ) $ 30.44 Non-vested at end of year 19,406 $ 19.95 49,516 $ 25.20 169,334 $ 26.38 (1) The number of units shown in the table above are based on target performance. The final number of shares of common stock issued may vary depending on the achievement of market conditions established within the awards, which could result in the actual number of shares issued ranging from zero to a maximum of two times the number of units shown in the above table. (2) Included within the 2015 forfeited / canceled units are PSU's related to a former executive that were clawed back. The Company recognized $0.2 million within Other Income line item on the Consolidated Statement of Operations related to these awards . A summary of SAR activity under the Plans is presented below: (in thousands, except for share and per share amounts) Number of Weighted- Aggregate Intrinsic Value Weighted- For the year ended December 31, 2015 SAR's outstanding, January 1, 2015 — $ — Granted 243,750 $ 13.87 Exercised — $ — Expired / forfeited — $ — SAR's outstanding, December 31, 2015 243,750 $ 13.87 $ — 4.5 SAR's vested and exercisable, December 31, 2015 43,750 $ 13.87 $ — — For the year ended December 31, 2016 SAR's outstanding, January 1, 2016 243,750 $ 13.87 Granted — $ — Exercised — $ — Expired / forfeited (243,750 ) $ 13.87 SAR's outstanding, December 31, 2016 — $ — $ — — SAR's vested and exercisable, December 31, 2016 — $ — $ — —
Schedule of Performance-Based Units, Settled	The following table shows the PSUs that were settled by issuing the Company's common stock relative to a peer group performance index and broad stock index. Year of Grant Net Number of Issued Shares upon Vesting Shares Withheld to Settle Tax Withholding Obligations TSR Multiple Range Russell 3000 Multiple Low High Low High For the year ended December 31, 2017 2014 6,476 3,573 0.75 1.00 — — 2015 3,869 2,310 0.60 0.60 — — For the year ended December 31, 2016 2013 38,706 1,572 0.63 1.00 — — 2014 11,487 — 0.63 0.63 — — 2015 13,529 — 0.50 0.50 — — For the year ended December 31, 2015 2013 8,768 3,954 1.75 1.75 2.00 2.00 2014 2,506 1,145 0.63 0.75 — 0.75

Property and Equipment (Tables)

Property and Equipment (Tables)	12 Months Ended
	Dec. 31, 2017
Property, Plant and Equipment [Abstract]
Schedule of Property and Equipment	The carrying basis and accumulated depreciation of property and equipment at December 31, 2017 and 2016 are: Life in Years As of December 31, (in thousands) 2017 2016 Machinery and equipment 2-7 $ 1,429 $ 1,634 Leasehold improvements 3 205 1,244 Furniture and fixtures 3-7 262 777 1,896 3,655 Less accumulated depreciation and amortization (1,486 ) (2,920 ) Total property and equipment, net $ 410 $ 735

Costs and Billings on Uncompl35

Costs and Billings on Uncompleted Contracts (Tables)	12 Months Ended
	Dec. 31, 2017
Costs and Billings on Uncompleted Contracts [Abstract]
Schedule of Deferred Project Costs and Revenue	The below table shows the components of these items: As of December 31, (in thousands) 2017 2016 Costs incurred on uncompleted contracts (gross) $ 15,945 $ 42,993 Billings on uncompleted contracts (gross) (17,775 ) (47,915 ) $ (1,830 ) $ (4,922 ) Included in the accompanying balance sheets under the following captions (1) : Costs in excess of billings on uncompleted contracts (2) $ — $ 25 Billings in excess of costs on uncompleted contracts (1,830 ) (4,947 ) $ (1,830 ) $ (4,922 ) (1) Amounts presented after netting of costs and billings on an individual contract basis. (2) Costs in excess of billings on uncompleted contracts is included in the Prepaid expenses and other assets caption on the Consolidated Balance Sheets.

Research and Development and 36

Research and Development and Government and Industry Funded Contracts (Tables)	12 Months Ended
	Dec. 31, 2017
Government and Industry Funded Contracts [Abstract]
Schedule of Government and Industry Funded Contracts	The following table shows the impact to Research and development expense amounts recognized in the Consolidated Statement of Operations: Years Ended December 31, (in thousands) 2017 2016 2015 Research and development expense $ 979 $ 173 $ 6,737 Less: Changes due to amount and timing of ARO reclamation 822 — — DOE funding — 821 1,375 Research and development expense, net $ 157 $ (648 ) $ 5,362

Supplemental Financial Inform37

Supplemental Financial Information (Tables)	12 Months Ended
	Dec. 31, 2017
Deferred Costs, Capitalized, Prepaid, and Other Assets Disclosure [Abstract]
Schedule of Prepaid Expenses and Other Assets and Other assets	The following table summarizes the components of Prepaid expenses and other assets and Other assets as presented in the Consolidated Balance Sheets : As of December 31, (in thousands) 2017 2016 Other current assets: Prepaid expenses $ 1,678 $ 1,169 Inventory 74 16 Costs in excess of billings — 25 Other 83 172 $ 1,835 $ 1,382 Other long-term assets: Deposits $ 223 $ 263 Intangibles 805 696 Cost method investment 552 1,016 Other long-term assets 728 323 $ 2,308 $ 2,298
Schedule of Finite-Lived Intangible Assets	The following table details the components of the Company's intangible assets: As of December 31, 2017 2016 (in thousands, except years) Initial Cost Net of Accumulated Amortization Initial Cost Net of Accumulated Amortization Patents $ 1,079 $ 805 $ 913 $ 696 Licensed technology — — 1,525 — Total $ 1,079 $ 805 $ 2,438 $ 696
Schedule of Other Liabilities	The following table details the components of Other current liabilities and Other long-term liabilities as presented in the Consolidated Balance Sheets : As of December 31, (in thousands) 2017 2016 Other current liabilities: Estimated Company contribution to 401(k) Plan $ 1,000 $ — Accrued interest — 618 Accrued losses on equipment contracts 69 183 Taxes payable 207 244 Deferred revenue — 76 Warranty liabilities 316 287 Deferred rent — 369 Asset retirement obligation — 1,312 Other 1,072 928 $ 2,664 $ 4,017 Other long-term liabilities: Deferred revenue, related party $ 2,000 $ 2,000 Deferred rent 192 38 Other long-term liabilities 93 — $ 2,285 $ 2,038
Schedule of Warranty Obligations	The changes in the carrying amount of the Company’s warranty obligations were as follows: As of December 31, (in thousands) 2017 2016 Balance, beginning of year $ 287 $ 1,197 Warranties accrued, net 580 89 Warranty claims (635 ) (899 ) Change in estimate related to previous warranties accrued 84 (100 ) Balance, end of year $ 316 $ 287
Schedule of Change in Asset Retirement Obligation	Included within Other current liabilities is the Company's asset retirement obligation. Changes in the Company's asset retirement obligation were as follows: As of December 31, (in thousands) 2017 2016 Asset retirement obligation, beginning of year $ 1,312 $ 1,248 Accretion 37 64 Liabilities settled (527 ) — Changes due to scope and timing of reclamation (822 ) — Asset retirement obligations, end of year $ — $ 1,312
Schedule of Statement of Operations, Supplemental Disclosures	The following table details the components of Interest expense in the Consolidated Statements of Operations : Years Ended December 31, (in thousands) 2017 2016 2015 453A interest $ 2,555 $ 2,490 $ 4,639 Line of Credit interest and letters of credit fees 417 89 49 Credit Agreement interest — 2,112 1,180 Interest on RCM6 Note Payable, related party — 263 2,468 Other 52 112 66 $ 3,024 $ 5,066 $ 8,402 The following table details the components of Other in the Consolidated Statements of Operations : Years Ended December 31, (in thousands) 2017 2016 2015 Impairment of cost method investment $ (464 ) $ (1,760 ) $ — Settlement agreement (1) 3,500 — — Estimate of Company contribution to 401(k) Plan (1,000 ) — — Gain on sale of equity method investment — 2,078 — Gain on settlement of note payable and licensed technology — 1,019 — Gain on termination of sales-type lease — 891 — Other (11 ) 235 494 $ 2,025 $ 2,463 $ 494 (1) On November 6, 2017, the Company entered into a settlement agreement with a former third-party service provider and as part of the settlement the Company received cash in the amount of $ 3.5 million . This amount was paid to the Company during the fourth quarter of 2017.

Fair Value Measurements (Tables

Fair Value Measurements (Tables)	12 Months Ended
	Dec. 31, 2017
Fair Value Disclosures [Abstract]
Schedule of Estimated Fair Values of Remaining Financial Instruments	The following table provides the estimated fair values of the remaining financial instruments: As of December 31, 2017 As of December 31, 2016 (in thousands) Carrying Value Fair Value Carrying Value Fair Value Financial Instruments: Highview Investment $ 552 $ 552 $ 1,016 $ 1,016 Highview Obligation $ 210 $ 210 $ 207 $ 207

Income Taxes (Tables)

Income Taxes (Tables)	12 Months Ended
	Dec. 31, 2017
Income Tax Disclosure [Abstract]
Income Tax Benefit (Expense) from Continuing Operations	The provision for income taxes consists of the following: Years Ended December 31, (in thousands, except for rate) 2017 2016 2015 Current portion of income tax expense: Federal $ 519 $ — $ — State 894 458 20 1,413 458 20 Deferred portion of income tax (benefit) expense: Federal 23,003 (61,396 ) — State (264 ) — — 22,739 (61,396 ) — Total income tax (benefit) expense $ 24,152 $ (60,938 ) $ 20 Effective tax rate 46 % (166 )% — %
Reconciliation of Expected Federal Income Taxes at Statutory Rates	A reconciliation of expected federal income taxes on income from operations at statutory rates with the expense (benefit) for income taxes is as follows: Years Ended December 31, (in thousands) 2017 2016 2015 Federal statutory rate $ 18,209 $ 12,859 $ (10,542 ) State income taxes, net of federal benefit 1,721 987 (781 ) Permanent differences 777 84 35 Tax credits (1,949 ) (2,419 ) (38,998 ) Valuation allowances (474 ) (72,359 ) 50,066 Changes in tax rates 5,818 (125 ) (243 ) Stock-based compensation 303 36 487 Other (253 ) (1 ) (4 ) Expense (benefit) for the provision for income taxes $ 24,152 $ (60,938 ) $ 20
Deferred Tax Assets And Liabilities	Details of the Company’s deferred tax assets and liabilities are summarized as follows: As of December 31, (in thousands) 2017 2016 Deferred tax assets Tax credits $ 100,367 $ 99,903 Deferred revenues and loss contract provisions 906 268 Employee related liabilities 393 3,796 Intangible assets 914 1,518 Equity method investments 8,457 12,326 Net operating loss carryforwards 2,004 13,341 Settlement and Royalty Indemnification — 4,264 Other investments 563 680 Other 648 1,429 Total deferred tax assets 114,252 137,525 Less valuation allowance (75,436 ) (75,910 ) Deferred tax assets 38,816 61,615 Less: Deferred tax liabilities Property and equipment and other (155 ) (219 ) Total deferred tax liabilities (155 ) (219 ) Net deferred tax assets $ 38,661 $ 61,396
Summary of Operating Loss Carryforwards and Tax Credit Carryforwards	The following table presents the approximate amount of state net operating loss carryforwards and federal tax credit carryforwards available to reduce future taxable income, along with the respective range of years that the net operating loss and tax credit carryforwards would expire if not utilized: As of December 31, (in thousands) 2017 Beginning expiration year Ending expiration year State net operating loss carryforwards $ 41,071 2021 2037 Federal tax credit carryforwards $ 100,367 2031 2037
Schedule of Unrecognized Tax Benefits	The following table sets forth a reconciliation of the beginning and ending unrecognized tax benefits on a gross basis for the years ended December 31, 2017 , 2016 and 2015 : Years Ended December 31, (in thousands) 2017 2016 2015 Balance as of January 1 $ 54 $ — $ — Increases for tax positions of current year — 54 — Balance as of December 31 $ 54 $ 54 $ —

Business Segment Information (T

Business Segment Information (Tables)	12 Months Ended
	Dec. 31, 2017
Segment Reporting [Abstract]
Segment Operating Results	Years Ended December 31, (in thousands) 2017 2016 2015 Revenues: Refined Coal: Earnings in equity method investments $ 53,843 $ 45,584 $ 8,921 Consulting services — — 55 Royalties, related party 9,672 6,125 10,642 63,515 51,709 19,618 Emissions Control: Equipment sales 31,401 46,949 60,099 Chemicals 4,246 3,025 888 Consulting services 45 648 1,697 35,692 50,622 62,684 Total segment reporting revenues 99,207 102,331 82,302 Adjustments to reconcile to reported revenues: Refined Coal: Earnings in equity method investments (53,843 ) (45,584 ) (8,921 ) Royalties, related party (9,672 ) (6,125 ) (10,642 ) (63,515 ) (51,709 ) (19,563 ) Total reported revenues $ 35,692 $ 50,622 $ 62,739 Segment operating income (loss) Refined Coal (1) $ 59,908 $ 51,264 $ 12,131 Emissions Control (2) 379 7,334 (7,583 ) Total segment operating income $ 60,287 $ 58,598 $ 4,548 (1) Included within the RC segment operating income for the year ended December 31, 2016 is a $2.1 million gain on the sale of RCM6 and for the years ended December 31, 2017 , 2016 and 2015 , 453A interest expense of $2.6 million , $2.5 million and $4.6 million , respectively. Also included within the RC segment operating income for the years ended December 31, 2016 and 2015 is interest expense related to the RCM6 Note Payable of $0.3 million and $2.5 million , respectively. (2) Included within the EC segment operating income for the year ended December 31, 2016 is a $0.9 million gain related to a termination of a sales-type lease.
Reconciliation of Reportable Segment Amounts to Consolidated Balances	A reconciliation of reportable segment operating income to the Company's consolidated net income is as follows: Years Ended December 31, (in thousands) 2017 2016 2015 Segment operating income Total reported segment operating income $ 60,287 $ 58,598 $ 4,548 Adjustments to reconcile to net income (loss) attributable to the Company Corporate payroll and benefits (5,565 ) (9,415 ) (14,842 ) Corporate rent and occupancy (293 ) (1,187 ) (707 ) Corporate legal and professional fees (4,010 ) (8,230 ) (15,199 ) Corporate general and administrative (3,400 ) (3,811 ) (3,640 ) Corporate depreciation and amortization (342 ) (608 ) (578 ) Corporate interest (expense) income, net (432 ) (2,334 ) 24 Other income (expense), net 5,780 3,727 273 Income tax (expense) benefit (24,152 ) 60,938 (20 ) Net income (loss) $ 27,873 $ 97,678 $ (30,141 )
Reconciliation of Assets from Segment to Consolidated	A reconciliation of reportable segment assets to the Company's consolidated assets is as follows: As of December 31, (in thousands) 2017 2016 Assets: Refined Coal (1) $ 8,092 $ 6,310 Emissions Control 3,755 24,551 Total segment assets 11,847 30,861 All Other and Corporate (2) 70,771 76,435 Consolidated $ 82,618 $ 107,296 (1) Includes $4.4 million of investments in equity method investees. (2) Included within All Other and Corporate are the Company's deferred tax assets.

Major Customers (Tables)

Major Customers (Tables)	12 Months Ended
	Dec. 31, 2017
Major Customers Disclosure [Abstract]
Schedule of Sales by Major Customers	Revenues from unaffiliated customers who represent 10% or more of the Company’s revenues in for the years ended December 31, 2017 , 2016 and 2015 were as follows: Years Ended December 31, Customer Revenue Type Segment(s) 2017 2016 2015 A Equipment sales EC 62% 21% 3% B Equipment sales, Consulting services EC —% 14% 16% C Consulting services EC —% —% 11% D Equipment sales EC —% —% 15%

Related Party Transactions (Tab

Related Party Transactions (Tables)	12 Months Ended
	Dec. 31, 2017
Related Party Transactions [Abstract]
Schedule of Related Party Transactions	The following table shows the other income recognized with related parties during the years ended December 31, 2017 , 2016 and 2015 : Years Ended December 31, (in thousands) 2017 2016 2015 Royalties, related party - Tinuum Group $ 9,672 $ 6,125 $ 10,642 The following table shows the Company's receivable balance associated with related parties as of December 31, 2017 and 2016 : As of December 31, (in thousands) 2017 2016 Receivable from related party - Tinuum Group $ 3,247 $ 1,934

Defined Contributions Savings43

Defined Contributions Savings Plan (Tables)	12 Months Ended
	Dec. 31, 2017
Retirement Benefits [Abstract]
Schedule of Contributions and Recognized Expense	The following table presents the amount of the Company' contributions made to the 401(k) Plan, which is reflected within the Payroll and benefits line item in the Consolidated Statements of Operations : Years Ended December 31, (in thousands) 2017 2016 2015 401(k) Plan employer contributions $ 56 $ 172 $ 439

Acquisition (Tables)

Acquisition (Tables)	12 Months Ended
	Dec. 31, 2017
Business Combinations [Abstract]
Summary of Purchase Consideration and Allocation	A summary of the purchase consideration and allocation of the purchase consideration is as follows: (in thousands) Purchase consideration: Cash paid $ 2,360 Fair value of liabilities assumed: Accrued liabilities 10 Contingent consideration 451 Total fair value of liabilities assumed 461 Total purchase consideration $ 2,821 Allocation of purchase consideration Receivables $ 360 Property and equipment and other 82 Intangibles - in process research and development 2,379 Total $ 2,821

Restructuring (Tables)

Restructuring (Tables)	12 Months Ended
	Dec. 31, 2017
Restructuring and Related Activities [Abstract]
Restructuring and Related Costs	A summary of the net pretax charges incurred by segment is as follows: Pretax Charge (in thousands, except employee data) Approximate Number of Employees Refined Coal Emissions Control All Other and Corporate Total Year ended December 31, 2016 Restructuring charges 40 $ — $ 1,164 $ 881 $ 2,045 Changes in estimates — (210 ) (276 ) (486 ) Total pretax charge, net of reversals $ — $ 954 $ 605 $ 1,559 Year ended December 31, 2015 Restructuring charges 162 $ — $ 5,108 $ 5,264 $ 10,372 Changes in estimates $ — $ (10 ) $ (2 ) $ (12 ) Total pretax charge, net of reversals $ — $ 5,098 $ 5,262 $ 10,360
Schedule of Restructuring Reserve by Type of Cost	The following table summarizes the Company's utilization of restructuring accruals for the years ended December 31, 2017 , 2016 and 2015 : (in thousands) Employee Severance Facility Closures Beginning accrual as of January 1, 2015 $ 1,690 $ — Expense provision (1) 8,498 2,650 Cash payments and other (1) (7,595 ) (1,873 ) Change in estimates (1) (12 ) — Accrual as of December 31, 2015 2,581 777 Expense provision (1) 2,045 — Cash payments and other (1) (3,898 ) (320 ) Change in estimates (1) (276 ) (210 ) Accrual as of December 31, 2016 452 247 Expense provision (1) 56 — Cash payments and other (1) (508 ) (250 ) Change in estimates (1) — 3 Accrual as of December 31, 2017 $ — $ — (1) Included within the Expense provision and Cash payments and other line items in the above table is stock-based compensation of zero , $0.4 million and $3.4 million for the years ended December 31, 2017 , 2016 and 2015 , respectively, resulting from the accelerated vesting of modified equity-based compensation awards for certain terminated employees. Additionally, as discussed in Note 17 , due to restructuring activities the Company fully impaired the carrying value of certain assets, thereby recognizing net impairment expense in the amount of $1.9 million during the year ended December 31, 2015.

Quarterly Financial Results (46

Quarterly Financial Results (unaudited) (Tables)	12 Months Ended
	Dec. 31, 2017
Quarterly Financial Information Disclosure [Abstract]
Schedule of Quarterly Financial Information	Summarized quarterly results for the two years ended December 31, 2017 and December 31, 2016 are as follows: For the Quarter Ended (in thousands, except per share data) December 31, 2017 September 30, 2017 June 30, 2017 March 31, 2017 Revenues $ 544 $ 2,294 $ 25,465 $ 7,389 Cost of revenues, exclusive of operating expenses shown below 648 2,041 23,295 5,901 Other operating expenses 4,205 4,197 4,020 5,199 Operating loss (4,309 ) (3,944 ) (1,850 ) (3,711 ) Earnings from equity method investments 17,754 12,120 10,155 13,814 Royalties, related party 3,247 2,804 1,866 1,755 Other income (expenses), net 1,831 (1,602 ) (121 ) 2,216 Income before income tax expense 18,523 9,378 10,050 14,074 Income tax expense 11,538 (1) 3,586 3,642 5,386 Net income $ 6,985 $ 5,792 $ 6,408 $ 8,688 Earnings per common share – basic $ 0.34 $ 0.28 $ 0.29 $ 0.39 Earnings per common share – diluted $ 0.33 $ 0.28 $ 0.29 $ 0.39 Weighted-average number of common shares outstanding Basic 20,767 20,808 21,866 22,056 Diluted 20,864 20,854 21,880 22,243 For the Quarter Ended (in thousands, except per share data) December 31, 2016 September 30, 2016 June 30, 2016 March 31, 2016 Revenues $ 3,604 $ 15,710 $ 8,951 $ 22,357 Cost of revenues, exclusive of operating expenses shown below 3,478 13,259 5,769 17,311 Other operating expenses 5,388 5,364 7,794 8,357 Operating loss (5,262 ) (2,913 ) (4,612 ) (3,311 ) Earnings from equity method investments 15,518 10,735 13,754 5,577 Royalties, related party 2,203 2,064 669 1,189 Other expenses, net 1,698 (2) 309 (1,852 ) 974 Income before income tax expense 14,157 10,195 7,959 4,429 Income tax (benefit) expense (61,673 ) (3) 583 99 53 Net income $ 75,830 $ 9,612 $ 7,860 $ 4,376 Loss per common share – basic $ 3.45 $ 0.44 $ 0.36 $ 0.20 Loss per common share – diluted $ 3.39 $ 0.43 $ 0.35 $ 0.20 Weighted-average number of common shares outstanding Basic 21,693 21,740 21,875 21,849 Diluted 22,061 22,098 22,187 22,177 (1) During the fourth quarter of 2017, the Company recorded an income tax expense of $11.5 million primarily related to statutory federal and state taxes of $5.7 million at the statutory rates, and the impact of the Tax Act, which increased the Company's income tax expense by $ 5.8 million . (2) During the fourth quarter of 2016, the Company revised its estimate for future Royalty Award payments based on an updated forecast provided to the Company from Carbon Solutions. Based primarily on the updated forecast, the Company recorded a $4.0 million reduction to its Royalty Award accrual. (3) During the fourth quarter of 2016, the Company released $ 61.4 million of the valuation allowance related to the deferred tax assets that resulted in an income tax benefit of $61.7 million . See further discussion in Note 12 .

Summary of Operations and Sig47

Summary of Operations and Significant Accounting Policies - Additional Information (Details) - USD ($) shares in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015	Jul. 27, 2017	Jan. 20, 2010
Accounting Policies [Line Items]
Provision for debt expense	$ 15,000	$ 13,000	$ 100,000
Notes receivable	1,000,000	1,000,000
Inventory	74,000	16,000
Asset retirement obligation	0	1,312,000	$ 1,248,000
Total shares excluded from diluted shares outstanding (in shares)			0.4
Accumulated deficit	(15,478,000)	$ (43,351,000)
Accounting Standards Update 2014-09 | Uncompleted Equipment Sales Projects
Accounting Policies [Line Items]
Accumulated deficit	(1,700,000)
Accounting Standards Update 2014-09 | Licensing Agreements
Accounting Policies [Line Items]
Accumulated deficit	$ (1,300,000)
Stock options
Accounting Policies [Line Items]
Total shares excluded from diluted shares outstanding (in shares)	0.3	0.2
Performance share units
Accounting Policies [Line Items]
Total shares excluded from diluted shares outstanding (in shares)	0.2	0.2	0.1
Patents
Accounting Policies [Line Items]
Weighted-average amortization period (in years)	16 years
Minimum
Accounting Policies [Line Items]
Accounts receivable payment terms	30 days
Property and equipment estimated useful lives	2 years
Warranty term	12 months
Maximum
Accounting Policies [Line Items]
Accounts receivable payment terms	45 days
Property and equipment estimated useful lives	7 years
Warranty term	24 months
Tinuum Group
Accounting Policies [Line Items]
Ownership interest, percent	42.50%	42.50%
Tinuum Services
Accounting Policies [Line Items]
Ownership interest, percent	50.00%				50.00%
GWN Manager
Accounting Policies [Line Items]
Ownership interest, percent	50.00%			50.00%

Summary of Operations and Sig48

Summary of Operations and Significant Accounting Policies - Receivables (Details) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Accounts Receivable, Net, Current [Abstract]
Trade receivables	$ 1,240	$ 4,289
Less: Allowance for doubtful accounts	(127)	(200)
Trade receivables, net	1,113	4,089
Other receivables	0	4,559
Total	$ 1,113	$ 8,648

Summary of Operations and Sig49

Summary of Operations and Significant Accounting Policies - Net Income (Loss) Per Share (Details) - USD ($) $ / shares in Units, shares in Thousands, $ 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
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Net income	$ 6,985	$ 5,792	$ 6,408	$ 8,688	$ 75,830	$ 9,612	$ 7,860	$ 4,376	$ 27,873	$ 97,678	$ (30,141)
Less: Dividends and undistributed income (loss) allocated to participating securities									171	1,105	(275)
Income (loss) attributable to common stockholders									$ 27,702	$ 96,573	$ (29,866)
Basic weighted-average number of common shares outstanding (in shares)	20,767	20,808	21,866	22,056	21,693	21,740	21,875	21,849	21,367	21,931	21,773
Add: dilutive effect of equity instruments (in shares)									46	303	0
Diluted weighted-average number of common shares outstanding (in shares)	20,864	20,854	21,880	22,243	22,061	22,098	22,187	22,177	21,413	22,234	21,773
Earnings (loss) per share - basic (in dollars per share)	$ 0.34	$ 0.28	$ 0.29	$ 0.39	$ 3.45	$ 0.44	$ 0.36	$ 0.20	$ 1.30	$ 4.40	$ (1.37)
Earnings (loss) per share - diluted (in dollars per share)	$ 0.33	$ 0.28	$ 0.29	$ 0.39	$ 3.39	$ 0.43	$ 0.35	$ 0.20	$ 1.29	$ 4.34	$ (1.37)

Summary of Operations and Sig50

Summary of Operations and Significant Accounting Policies - Risks and Uncertainties (Details) - Tinuum Group	Dec. 31, 2017debt_instrument
Concentration Risk [Line Items]
Debt Instruments, Number of Instruments Held	17
Single Customer
Concentration Risk [Line Items]
Debt Instruments, Number of Instruments Held	11

Equity Method Investments - Add

Equity Method Investments - Additional Information (Details) - USD ($)	Jul. 27, 2017	Mar. 03, 2016	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	Jan. 20, 2010
Schedule of Equity Method Investments [Line Items]
Earnings from equity method investments			$ 17,754,000	$ 12,120,000	$ 10,155,000	$ 13,814,000	$ 15,518,000	$ 10,735,000	$ 13,754,000	$ 5,577,000	$ 53,843,000	$ 45,584,000	$ 8,921,000
Equity method investments			$ 4,351,000				$ 3,959,000				4,351,000	3,959,000
Gain on sale of equity method investment											0	2,078,000	0
Purchase, contributions and advances to equity method investees											61,000	223,000	2,128,000
Impairment of equity method investments											0	0	0
Purchase of and contributions to equity method investments											$ 100,000	$ 200,000	2,400,000
Disposed of by Sale | RCM6, LLC (RCM6)
Schedule of Equity Method Investments [Line Items]
Net sales proceeds, including proceeds received by third parties		$ 1,800,000
Tinuum Group
Schedule of Equity Method Investments [Line Items]
Ownership interest, percent			42.50%				42.50%				42.50%	42.50%
Preferred return to third party unitholders											15.00%
Preferred unitholder, redemption period											10 years
Preferred unitholder, redemption notice period											180 days
Voting interest			50.00%								50.00%
Earnings from equity method investments											$ 48,875,000	$ 41,650,000	8,651,000
Equity method investments			$ 0				$ 0				0	0	0	$ 0
Losses related to VIEs, attributable to noncontrolling interest											43,474,000	27,234,000	10,675,000
Tinuum Group | Cash distributions
Schedule of Equity Method Investments [Line Items]
Earnings from equity method investments											(48,875,000)	(41,650,000)	(8,651,000)
Equity method investments			$ 48,875,000				41,650,000				$ 48,875,000	41,650,000	$ 8,651,000	$ 0
NexGen Refined Coal, LLC (NexGen)
Schedule of Equity Method Investments [Line Items]
Ownership interest, percent			42.50%								42.50%
GSFS Investments I Corp. (GSFS)
Schedule of Equity Method Investments [Line Items]
Ownership interest, percent			15.00%								15.00%
RCM6, LLC (RCM6)
Schedule of Equity Method Investments [Line Items]
Ownership interest, percent													24.95%
Earnings from equity method investments										$ (600,000)
RCM6, LLC (RCM6) | Refined Coal
Schedule of Equity Method Investments [Line Items]
Gain on sale of equity method investment												2,100,000
RCM6, LLC (RCM6) | Disposed of by Sale | RCM6, LLC (RCM6)
Schedule of Equity Method Investments [Line Items]
Ownership interest, percent		24.95%
Tinuum Services
Schedule of Equity Method Investments [Line Items]
Ownership interest, percent			50.00%								50.00%				50.00%
Earnings from equity method investments											$ 4,963,000	4,491,000	$ 4,838,000
Equity method investments			$ 4,284,000				$ 3,959,000				4,284,000	3,959,000
Losses related to VIEs, attributable to noncontrolling interest											$ 222,707,000	$ 198,464,000	$ 213,746,000
Percent of Losses Removed from Net Income, Attributable to Noncontrolling Interest			100.00%								100.00%
GWN Manager
Schedule of Equity Method Investments [Line Items]
Ownership interest, percent	50.00%		50.00%								50.00%
Equity method investments			$ 100,000								$ 100,000
Purchase, contributions and advances to equity method investees	$ 100,000
Tinuum Group | RC Facility
Schedule of Equity Method Investments [Line Items]
Ownership interest, percent	49.90%
Tinuum Group | RC Facility | Disposed of by Sale
Schedule of Equity Method Investments [Line Items]
Ownership interest, percent	49.90%
GWN Manager | Tinuum Group
Schedule of Equity Method Investments [Line Items]
Ownership interest, percent	0.20%

Equity Method Investments - Equ

Equity Method Investments - Equity Method Investments (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
Equity Method Investment, Summarized Financial Information, Income Statement [Abstract]
ADES equity earnings (loss)	$ 17,754,000	$ 12,120,000	$ 10,155,000	$ 13,814,000	$ 15,518,000	$ 10,735,000	$ 13,754,000	$ 5,577,000	$ 53,843,000	$ 45,584,000	$ 8,921,000
Equity Method Investment, Financial Statement, Reported Amounts [Abstract]
Equity method investments	4,351,000				3,959,000				4,351,000	3,959,000
Earnings from equity method investments	17,754,000	$ 12,120,000	$ 10,155,000	$ 13,814,000	15,518,000	$ 10,735,000	$ 13,754,000	5,577,000	53,843,000	45,584,000	8,921,000
Purchase of and contributions to equity method investments									100,000	200,000	2,400,000
Distributions from equity method investees, return on investment									4,638,000	7,900,000	5,019,000
Included in Investing Cash Flows									48,875,000	38,250,000	8,651,000
Tinuum Group
Equity Method Investment, Summarized Financial Information [Abstract]
Current assets	31,068,000				24,584,000				31,068,000	24,584,000
Non-current assets	75,592,000				83,621,000				75,592,000	83,621,000
Current liabilities	48,280,000				43,117,000				48,280,000	43,117,000
Non-current liabilities	8,350,000				11,456,000				8,350,000	11,456,000
Redeemable Class B equity	821,000				18,250,000				821,000	18,250,000
Members equity attributable to Class A members	40,452,000				26,475,000				40,452,000	26,475,000
Noncontrolling interests	8,757,000				8,907,000				8,757,000	8,907,000
Equity Method Investment, Summarized Financial Information, Income Statement [Abstract]
Gross profit									95,552,000	92,305,000	108,416,000
Operating, selling, general and administrative expenses									22,958,000	23,662,000	23,405,000
Income (loss) from operations									72,594,000	68,643,000	85,011,000
Other expenses									(4,520,000)	(8,775,000)	(2,203,000)
Class B preferred return									(1,712,000)	(3,901,000)	(6,157,000)
Loss attributable to noncontrolling interest									43,474,000	27,234,000	10,675,000
Net income (loss)									109,836,000	83,201,000	87,326,000
ADES equity earnings (loss)									48,875,000	41,650,000	8,651,000
Equity Method Investment, Financial Statement, Reported Amounts [Abstract]
Equity method investments	0				0				0	0	0	$ 0
Earnings from equity method investments									48,875,000	41,650,000	8,651,000
Distributions from equity method investees, return on investment								$ 3,400,000	0	3,400,000	0
Distributions from equity method investees in excess of cumulative earnings									48,875,000	38,250,000	8,651,000
Included in Investing Cash Flows									12,218,000	9,894,000	3,263,000
Tinuum Services
Equity Method Investment, Summarized Financial Information [Abstract]
Current assets	546,681,000				278,001,000				546,681,000	278,001,000
Non-current assets	98,640,000				3,426,000				98,640,000	3,426,000
Current liabilities	178,376,000				97,093,000				178,376,000	97,093,000
Non-current liabilities	75,717,000				1,488,000				75,717,000	1,488,000
Equity	8,569,000				7,918,000				8,569,000	7,918,000
Noncontrolling interests	382,659,000				174,928,000				382,659,000	174,928,000
Equity Method Investment, Summarized Financial Information, Income Statement [Abstract]
Gross profit									(64,796,000)	(54,644,000)	(42,496,000)
Operating, selling, general and administrative expenses									147,917,000	134,782,000	161,456,000
Income (loss) from operations									(212,713,000)	(189,426,000)	(203,952,000)
Other expenses									(68,000)	(56,000)	(118,000)
Loss attributable to noncontrolling interest									222,707,000	198,464,000	213,746,000
Net income (loss)									9,926,000	8,982,000	9,676,000
ADES equity earnings (loss)									4,963,000	4,491,000	4,838,000
Equity Method Investment, Financial Statement, Reported Amounts [Abstract]
Equity method investments	4,284,000				3,959,000				4,284,000	3,959,000
Earnings from equity method investments									4,963,000	4,491,000	4,838,000
Distributions from equity method investees, return on investment									4,638,000	4,500,000	5,019,000
Other
Equity Method Investment, Summarized Financial Information, Income Statement [Abstract]
ADES equity earnings (loss)									5,000	(557,000)	(4,568,000)
Equity Method Investment, Financial Statement, Reported Amounts [Abstract]
Equity method investments	$ 67,000				$ 0				67,000	0
Earnings from equity method investments									$ 5,000	$ (557,000)	$ (4,568,000)

Equity Method Investments - Rol

Equity Method Investments - Rollforward of CCS Investment (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
Equity Method Investments [Roll Forward]
Beginning balance				$ 3,959,000					$ 3,959,000
Cash distributions from Tinuum Group	$ (17,754,000)	$ (12,120,000)	$ (10,155,000)	(13,814,000)	$ (15,518,000)	$ (10,735,000)	$ (13,754,000)	$ (5,577,000)	(53,843,000)	$ (45,584,000)	$ (8,921,000)
Adjustment for current year cash distributions in excess of investment balance									48,875,000	38,250,000	8,651,000
Total investment balance, equity earnings (loss) and cash distributions	4,351,000				3,959,000				4,351,000	3,959,000
Tinuum Group
Equity Method Investments [Roll Forward]
Beginning balance				0				0	0	0	0
ADES proportionate share of income from CCS									46,551,000	35,019,000	35,265,000
Recovery of cash distributions in excess of investment balance (prior to cash distributions)									(9,894,000)	(3,263,000)	(29,877,000)
Cash distributions from Tinuum Group									(48,875,000)	(41,650,000)	(8,651,000)
Adjustment for current year cash distributions in excess of investment balance									12,218,000	9,894,000	3,263,000
Total investment balance, equity earnings (loss) and cash distributions	$ 0				$ 0				$ 0	$ 0	0
Ownership interest, percent	42.50%				42.50%				42.50%	42.50%
Ownership interest multiplied by net income available to members, percent	42.50%								42.50%
Tinuum Group | ADES equity earnings (loss)
Equity Method Investments [Roll Forward]
Beginning balance				41,650,000				8,651,000	$ 41,650,000	$ 8,651,000	0
ADES proportionate share of income from CCS									46,551,000	35,019,000	35,265,000
Recovery of cash distributions in excess of investment balance (prior to cash distributions)									(9,894,000)	(3,263,000)	(29,877,000)
Cash distributions from Tinuum Group									0	0	0
Adjustment for current year cash distributions in excess of investment balance									12,218,000	9,894,000	3,263,000
Total investment balance, equity earnings (loss) and cash distributions	$ 48,875,000				$ 41,650,000				48,875,000	41,650,000	8,651,000
Tinuum Group | Cash distributions
Equity Method Investments [Roll Forward]
Beginning balance				41,650,000				8,651,000	41,650,000	8,651,000	0
ADES proportionate share of income from CCS									0	0	0
Recovery of cash distributions in excess of investment balance (prior to cash distributions)									0	0	0
Cash distributions from Tinuum Group									48,875,000	41,650,000	8,651,000
Adjustment for current year cash distributions in excess of investment balance									0	0	0
Total investment balance, equity earnings (loss) and cash distributions	48,875,000				41,650,000				48,875,000	41,650,000	8,651,000
Tinuum Group | Memo Account: Cash distributions and equity loss in (excess) of investment balance
Equity Method Investments [Roll Forward]
Beginning balance				$ (9,894,000)				(3,263,000)	(9,894,000)	(3,263,000)	(29,877,000)
ADES proportionate share of income from CCS									0	0	0
Recovery of cash distributions in excess of investment balance (prior to cash distributions)									(9,894,000)	(3,263,000)	(29,877,000)
Cash distributions from Tinuum Group									0	0	0
Adjustment for current year cash distributions in excess of investment balance									12,218,000	9,894,000	3,263,000
Total investment balance, equity earnings (loss) and cash distributions	$ 12,218,000				$ (9,894,000)				$ 12,218,000	$ (9,894,000)	$ (3,263,000)
RCM6, LLC (RCM6)
Equity Method Investments [Roll Forward]
Cash distributions from Tinuum Group								$ 600,000
Ownership interest, percent											24.95%

Borrowings - Line of Credit (De

Borrowings - Line of Credit (Details) - USD ($)	Nov. 29, 2016	Dec. 31, 2017	Sep. 30, 2017	Dec. 31, 2016	Nov. 30, 2016	Sep. 30, 2013
Debt Instrument [Line Items]
Line of credit facility, maximum borrowing capacity			$ 10,000,000		$ 15,000,000	$ 10,000,000
Outstanding amount	$ 0	$ 0
Deposit account balance requirement					6,000,000
Requirements for EBITDA					24,000,000
Letters of credit		(3,500,000)		$ (15,505,000)
Remaining borrowing capacity		6,500,000
Secured
Debt Instrument [Line Items]
Letters of credit		(3,500,000)
Maximum
Debt Instrument [Line Items]
Line of credit facility, used as collateral			$ 8,000,000
After certain conditions are met
Debt Instrument [Line Items]
Deposit account balance requirement					$ 3,000,000
Line of Credit
Debt Instrument [Line Items]
Interest rate, stated percentage	5.00%
Line of Credit | Prime Rate
Debt Instrument [Line Items]
Basis spread on variable rate	1.00%
Letter of Credit
Debt Instrument [Line Items]
Outstanding amount		3,500,000		$ 1,776,000
Remaining borrowing capacity		$ 4,500,000

Borrowings - Letters of Credit

Borrowings - Letters of Credit (Details) - USD ($)	Dec. 31, 2017	Mar. 31, 2017	Dec. 31, 2016	Nov. 29, 2016
Debt Instrument [Line Items]
LOC Outstanding	$ 3,500,000		$ 15,505,000
Utilization of LOC Availability	0			$ 0
Expiration of Letters of Credit
Letters of credit, expire in less than 1 year	3,500,000
Letters of credit, expire in 1-3 years	0
Letters of credit, expire in 4-5 years	0
Letters of credit, expire after 5 years	0
Letter of Credit
Debt Instrument [Line Items]
Allowance		$ (400,000)
Utilization of LOC Availability	3,500,000		1,776,000
Restricted Cash	0		13,736,000
Equipment Systems, ACI
Debt Instrument [Line Items]
LOC Outstanding		$ 800,000
Contract performance - equipment systems
Debt Instrument [Line Items]
LOC Outstanding			1,855,000
Contract performance - equipment systems | Letter of Credit
Debt Instrument [Line Items]
Utilization of LOC Availability			1,776,000
Restricted Cash			86,000
Royalty Award
Debt Instrument [Line Items]
LOC Outstanding	3,500,000		7,150,000
Royalty Award | Letter of Credit
Debt Instrument [Line Items]
Utilization of LOC Availability	3,500,000		0
Restricted Cash	$ 0		7,150,000
Other
Debt Instrument [Line Items]
LOC Outstanding			6,500,000
Other | Letter of Credit
Debt Instrument [Line Items]
Utilization of LOC Availability			0
Restricted Cash			$ 6,500,000

Borrowings - Credit Agreement (

Borrowings - Credit Agreement (Details) - Term Loan $ in Millions	Jun. 30, 2016USD ($)
Debt Instrument [Line Items]
Short-term note payable	$ 15
Extinguishment of debt, amount	$ 9.9

Borrowings - Tinuum Group (Deta

Borrowings - Tinuum Group (Details) - RCM6, LLC (RCM6)	Mar. 03, 2016	Dec. 31, 2015	Feb. 10, 2014
Debt Instrument [Line Items]
Ownership interest, percent		24.95%
Interest rate, stated percentage			1.65%
Interest rate, effective percentage			20.00%
RCM6, LLC (RCM6) | Disposed of by Sale
Debt Instrument [Line Items]
Ownership interest, percent	24.95%

Borrowings - DSI Business Owner

Borrowings - DSI Business Owner (Details) - USD ($) $ in Thousands	1 Months Ended	3 Months Ended	12 Months Ended
	Feb. 29, 2016	Mar. 31, 2016	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Debt Instrument [Line Items]
Gain on settlement of note payable and licensed technology			$ 0	$ 1,019	$ 0
Affiliated Entity
Debt Instrument [Line Items]
Payable to related party	$ 1,100
Extinguishment of debt, amount	$ 300	$ 300
Gain on settlement of note payable and licensed technology				$ 900

Commitments and Contingencies -

Commitments and Contingencies - Legal Proceedings (Details) - Monetary Damages $ in Millions	Dec. 31, 2016USD ($)
Denver Settlement
Loss Contingencies [Line Items]
Loss contingency accrual	$ 4
Derivative Settlement
Loss Contingencies [Line Items]
Loss contingency accrual	$ 0.6

Commitments and Contingencies60

Commitments and Contingencies - SEC Inquiry (Details) $ in Millions	Jun. 30, 2016USD ($)
SEC Inquiry | Monetary Damages
Loss Contingencies [Line Items]
Loss contingency accrual	$ 0.5

Commitments and Contingencies61

Commitments and Contingencies - Settlement and Royalty Indemnity, Narrative (Details) - USD ($)	Dec. 29, 2017	Nov. 30, 2011	Dec. 31, 2016	Dec. 31, 2017	Dec. 31, 2016
Loss Contingencies [Line Items]
Reduction to royalty award accrual			$ 4,000,000
Letters of credit			15,505,000	$ 3,500,000	$ 15,505,000
Settlement and royalty indemnification			5,656,000	0	5,656,000
Settlement and royalty indemnification, long-term			5,382,000	0	5,382,000
Royalty Award
Loss Contingencies [Line Items]
Letters of credit			$ 7,150,000	3,500,000	7,150,000
Norit Litigation
Loss Contingencies [Line Items]
Benchmark for earnings for increase in letters of credit		$ 20,000,000
Increase in letters of credit as collateral		$ 5,000,000
Ability to pay dividends, percent of market fair value		50.00%
Reduction to royalty award accrual				$ 3,400,000	$ 4,000,000
Payments for legal settlements	$ 3,300,000

Commitments and Contingencies62

Commitments and Contingencies - Settlement and Royalty Indemnity (Details) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Commitments and Contingencies Disclosure [Abstract]
Settlement and Royalty Indemnification	$ 0	$ 5,656
Legal settlements	0	5,050
Legal settlements and accruals, current	0	10,706
Settlement and Royalty Indemnification, long-term	0	5,382
Legal settlements and accruals, long-term	$ 0	$ 16,088

Commitments and Contingencies63

Commitments and Contingencies - Profit Sharing Retirement Plan (Details) $ in Millions	Dec. 31, 2017USD ($)
Other current liabilities
Loss Contingencies [Line Items]
Liability, defined benefit plan	$ 1

Commitments and Contingencies64

Commitments and Contingencies - Tinuum Group and Consultant Obligation (Details)	Dec. 31, 2017
Tinuum Group
Related Party Transaction [Line Items]
Limited guarantees, percent	50.00%

Commitments and Contingencies65

Commitments and Contingencies - Performance Guarantee on Equipment Systems (Details)	3 Months Ended								12 Months Ended
	Dec. 31, 2017USD ($)	Sep. 30, 2017USD ($)	Jun. 30, 2017USD ($)	Mar. 31, 2017USD ($)	Dec. 31, 2016USD ($)	Sep. 30, 2016USD ($)	Jun. 30, 2016USD ($)	Mar. 31, 2016USD ($)	Dec. 31, 2017USD ($)	Dec. 31, 2016USD ($)	Dec. 31, 2015USD ($)guarantee
Loss Contingencies [Line Items]
Revenues	$ 544,000	$ 2,294,000	$ 25,465,000	$ 7,389,000	$ 3,604,000	$ 15,710,000	$ 8,951,000	$ 22,357,000	$ 35,692,000	$ 50,622,000	$ 62,739,000
Equipment Systems, ACI
Loss Contingencies [Line Items]
Number of performance guarantee being modified and corrected | guarantee											2
Revenues											$ 0
Performance guarantees testing, cost incurred											$ 900,000

Commitments and Contingencies66

Commitments and Contingencies - Operating Lease Obligations (Details) $ in Thousands	12 Months Ended
	Dec. 31, 2017USD ($)ft²lease	Dec. 31, 2016USD ($)	Dec. 31, 2015USD ($)
Commitments and Contingencies Disclosure [Abstract]
Square feet under lease | ft²	17,344
Number of leases | lease	2
Termination fee		$ 300
Operating Leases, Future Minimum Payments Due, Fiscal Year Maturity [Abstract]
2,018	$ 298
2,019	205
2,020	82
2,021	0
Thereafter	0
Total	585
Rent expense (1)	$ (60)	$ 847	$ 1,838
Minimum
Lease And Rental Expense [Line Items]
Operating leases, term of contract	4 years
Maximum
Lease And Rental Expense [Line Items]
Operating leases, term of contract	7 years

Stockholders' Equity - Addition

Stockholders' Equity - Additional Information (Details) - USD ($)	1 Months Ended		12 Months Ended
	Dec. 31, 2017	Jun. 06, 2017	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015	May 05, 2017	May 04, 2017
Class of Stock [Line Items]
Preferred stock, shares outstanding (in shares)	0		0	0
Number of shares tendered and not properly withdrawn (in shares)		2,858,425
Tendered shares as percent of shares outstanding							6.20%
Dividends paid			$ 15,700,000	$ 0	$ 0
Common Stock
Class of Stock [Line Items]
Shares acquired (in shares)	342,875	1,370,891
Treasury stock acquired	$ 3,400,000	$ 12,900,000
Additional tendered shares acquires (in shares)		445,891
Common Stock | Manager of a Financial Institution
Class of Stock [Line Items]
Shares acquired (in shares)		70,178
Maximum
Class of Stock [Line Items]
Number of shares authorized to be repurchased (in shares)						925,000
Share price (amount per shares)						$ 10.8
Authorized amount						$ 10,000,000
Additional authorized amount (percent)						2.00%
Requirement to own shares outstanding as percent		4.99%
Maximum | Common Stock
Class of Stock [Line Items]
Number of shares authorized to be repurchased (in shares)	10,000,000		10,000,000
Minimum
Class of Stock [Line Items]
Share price (amount per shares)						$ 9.4

Stockholders' Equity - Dividend

Stockholders' Equity - Dividends (Details) - $ / shares	3 Months Ended			12 Months Ended
	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Equity [Abstract]
Dividends declared (in dollars per share)	$ 0.25	$ 0.25	$ 0.25	$ 0.75	$ 0	$ 0

Stock-Based Compensation - Addi

Stock-Based Compensation - Additional Information (Details) $ / shares in Units, $ in Thousands	12 Months Ended
	Dec. 31, 2017USD ($)$ / sharesshares	Dec. 31, 2016USD ($)employee$ / sharesshares	Dec. 31, 2015USD ($)employee$ / sharesshares
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of employees affected | employee		27	37
Net increase in share-based compensation		$ 400	$ 3,400
Stock-based compensation	$ 2,209	2,762	6,462
Stock-based compensation expense	2,209	2,868	7,204
Reclassification and settlement of equity awards		899
Additional Paid-in Capital
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock-based compensation	$ 2,209	2,762	$ 6,462
Reclassification and settlement of equity awards		$ 899
Restricted stock awards
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Granted (in shares) | shares	191,076	363,758	127,943
Aggregate weighted average grant-date fair value of share granted	$ 1,800	$ 2,700	$ 1,900
Fair value of shares vested	1,700	2,100	2,900
Stock-based compensation expense	$ 1,400	$ 2,021	$ 2,909
Exercise price (in usd per share) | $ / shares	$ 8.03	$ 11.96	$ 17.51
Restricted stock awards | Minimum
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Vesting period	3 years
Restricted stock awards | Maximum
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Vesting period	5 years
Stock options
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Vesting period	3 years
Contractual term	5 years
Options granted (in shares) | shares	0	546,196	56,250
Expected term (in years)		2 years 7 months 6 days	5 years
Expiration period	5 years
Weighted-average grant-date fair value	$ 0	$ 500	$ 800
Options exercised (in shares) | shares	0	0	0
Stock-based compensation expense	$ 672	$ 285	$ 658
Shares issued as a result of options exercised	$ 700	$ 500	$ 700
Stock appreciation rights
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Vesting period	3 years
Expected term (in years)	5 years		5 years
Granted (in shares) | shares	0	243,750
Net increase in share-based compensation	$ 100
Aggregate weighted average grant-date fair value of share granted	0	$ 0
Stock-based compensation expense	$ 0	$ 106	$ 742
Exercise price (in usd per share) | $ / shares	$ 0	$ 0
Stock appreciation rights | Additional Paid-in Capital
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Reclassification and settlement of equity awards	$ 900
Stock appreciation rights | Executive Officer
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock-based compensation expense			$ 500
Exercise price (in usd per share) | $ / shares			$ 13.87
Performance share units
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Expected term (in years)			3 years
Granted (in shares) | shares	0	0	69,218
Maximum number of common shares to be received by participant, percent	200.00%
Maximum reduction in number of common shares to be received by participants, percent	0.00%
Percent of award based on performance of total stockholder return	75.00%
Service period	3 years
Aggregate weighted average grant-date fair value of share granted	$ 0	$ 0	$ 1,400
Stock-based compensation expense	$ 137	$ 456	$ 2,895
Exercise price (in usd per share) | $ / shares	$ 26.87	$ 26.87	$ 30.52
2010 Plan
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares reserved for issuance (in shares) | shares	600,000
2017 Plan
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares reserved for issuance (in shares) | shares	2,000,000

Stock-Based Compensation - Fair

Stock-Based Compensation - Fair Value Assumptions for Stock Options (Details) - Stock options	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Risk-free interest rate	1.30%	1.80%
Dividend yield	0.00%	0.00%
Volatility	78.80%	74.50%
Expected term (in years)	2 years 7 months 6 days	5 years

Stock-Based Compensation - Fa71

Stock-Based Compensation - Fair Value Assumptions for SAR (Details) - Stock appreciation rights	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2015
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Risk-free interest rate		1.80%
Dividend yield		0.00%
Volatility		74.50%
Expected term (in years)	5 years	5 years

Stock-Based Compensation - Fa72

Stock-Based Compensation - Fair Value Assumptions for PSU (Details) - Performance share units	12 Months Ended
	Dec. 31, 2015
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Risk-free interest rate	1.00%
Dividend yield	0.00%
Volatility	64.30%
Performance period (in years)	3 years

Stock-Based Compensation - Allo

Stock-Based Compensation - Allocation of Compensation Expense (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Total stock-based compensation expense	$ 2,209	$ 2,868	$ 7,204
Restricted stock awards
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Total stock-based compensation expense	1,400	2,021	2,909
Stock options
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Total stock-based compensation expense	672	285	658
Stock appreciation rights
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Total stock-based compensation expense	0	106	742
Performance share units
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Total stock-based compensation expense	$ 137	$ 456	$ 2,895

Stock-Based Compensation - Summ

Stock-Based Compensation - Summary of Unrecognized Compensation Cost (Details) $ in Thousands	12 Months Ended
	Dec. 31, 2017USD ($)
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Total unrecognized stock-based compensation expense	$ 1,793
Expected Weighted-Average Period of Recognition (in years)	1 year 10 months 17 days
Restricted stock awards
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Unrecognized compensation costs, equity instruments other than options	$ 1,735
Expected Weighted-Average Period of Recognition (in years)	1 year 11 months 5 days
Stock options
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Unrecognized compensation costs, options	$ 58
Expected Weighted-Average Period of Recognition (in years)	3 months
Performance share units
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Unrecognized compensation costs, equity instruments other than options	$ 0

Stock-Based Compensation - Su75

Stock-Based Compensation - Summary of Non-vested Restricted Stock Activity (Details) - USD ($) $ / shares in Units, $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Weighted Average Grant Date Fair Value
Total stock-based compensation expense	$ 2,209	$ 2,868	$ 7,204
Restricted stock awards
Shares
Non-vested shares, Beginning balance (in shares)	297,347	134,708	209,921
Granted (in shares)	191,076	363,758	127,943
Vested (in shares)	(210,129)	(175,956)	(165,796)
Forfeited (in shares)	(1,687)	(25,163)	(37,360)
Non-vested shares, Ending balance (in shares)	276,607	297,347	134,708
Weighted Average Grant Date Fair Value
Nonvested shares, Weighted Average Grant Date Fair Value, Beginning Balance (in usd per share)	$ 8.03	$ 8.49	$ 13.59
Non vested shares granted, Weighted Average Grant Date Fair Value (in usd per share)	9.50	7.46	14.97
Vested in period, Weighted Average Grant Date Fair Value (in usd per share)	8.03	11.96	17.51
Forfeited, Weighted Average Grant Date Fair Value (in usd per share)	9.17	15.58	19.30
Non-vested shares, Weighted Average Grant Date Fair Value, Ending Balance (in usd per share)	$ 9.03	$ 8.03	$ 8.49
Total stock-based compensation expense	$ 1,400	$ 2,021	$ 2,909
Restricted stock awards | Other
Weighted Average Grant Date Fair Value
Total stock-based compensation expense	$ 100

Stock-Based Compensation - Su76

Stock-Based Compensation - Summary of Option Activity (Details) - Stock options - USD ($) $ / shares in Units, $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Number of Options Outstanding and Exercisable
Options outstanding, beginning of year (in shares)	632,446	106,250	74,200
Options granted (in shares)	0	546,196	56,250
Options exercised (in shares)	0	0	0
Options expired / forfeited (in shares)	(10,000)	(20,000)	(24,200)
Options outstanding, end of year (in shares)	622,446	632,446	106,250
Options vested and exercisable (in shares)	429,780	247,780	82,915
Weighted Average Exercise Price
Options outstanding, end of year (in usd per shares)	$ 11.61	$ 15.22	$ 13.76
Options granted (in usd per shares)	0	11.10	13.87
Options exercised (in usd per shares)	0	0	0
Options expired / forfeited (in usd per shares)	9.77	16.90	7.59
Options outstanding, end of year (in usd per shares)	11.64	11.61	15.22
Options vested and exercisable,Weighted Average Exercise Price (in usd per shares)	$ 11.47	$ 13.30	$ 14.04
Options outstanding, end of year, Aggregate Intrinsic Value	$ 119	$ 183	$ 0
Options outstanding, end of year, Weighted Average Remaining Contractual Term (in years)	2 years 2 months 27 days	4 years	3 years 9 months 18 days
Options vested and exercisable, Aggregate Intrinsic Value	$ 119	$ 69	$ 0
Options vested and exercisable, Weighted Average Remaining Contractual Term (in years)	2 years 11 days	3 years 4 months 24 days	3 years 10 months 24 days
2007 Equity Incentive Plan
Number of Options Outstanding and Exercisable
Options granted (in shares)	243,750

Stock-Based Compensation - Su77

Stock-Based Compensation - Summary of SARs (Details) - Stock appreciation rights - USD ($) $ / shares in Units, $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016
Shares
Non-vested shares, Beginning balance (in shares)	243,750	0
Granted (in shares)	0	243,750
Vested (in shares)	0	0
Forfeited/Canceled (in shares)	(243,750)	0
Non-vested shares, Ending balance (in shares)	0	243,750
Weighted Average Grant Date Fair Value
Nonvested shares, Weighted Average Grant Date Fair Value, Beginning Balance (in usd per share)	$ 13.87	$ 0
Non vested shares granted, Weighted Average Grant Date Fair Value (in usd per share)	0	13.87
Vested in period, Weighted Average Grant Date Fair Value (in usd per share)	0	0
Forfeited, Weighted Average Grant Date Fair Value (in usd per share)	13.87	0
Non-vested shares, Weighted Average Grant Date Fair Value, Ending Balance (in usd per share)	$ 0	$ 13.87
Aggregate weighted average grant-date fair value of share granted	$ 0	$ 0
SARs outstanding, weighted average remaining contractual term		4 years 6 months
SARs vested and exercisable (in shares)	0	43,750
SARs vested and exercisable, weighted average exercise price (in usd per share)	$ 0	$ 13.87
SARs exercisable, intrinsic value	$ 0	$ 0

Stock-Based Compensation - Su78

Stock-Based Compensation - Summary of Non-vested PSUs (Details) - USD ($) $ / shares in Units, $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Weighted Average Grant Date Fair Value
Stock-based compensation expense	$ 2,209	$ 2,868	$ 7,204
Performance share units
Shares
Non-vested shares, Beginning balance (in shares)	49,516	169,334	142,357
Granted (in shares)	0	0	69,218
Vested (in shares)	(30,110)	(119,818)	(13,763)
Forfeited/Canceled (in shares)	0	0	(28,478)
Non-vested shares, Ending balance (in shares)	19,406	49,516	169,334
Weighted Average Grant Date Fair Value
Nonvested shares, Weighted Average Grant Date Fair Value, Beginning Balance (in usd per share)	$ 25.20	$ 26.38	$ 30.65
Non vested shares granted, Weighted Average Grant Date Fair Value (in usd per share)	0	0	20.10
Vested in period, Weighted Average Grant Date Fair Value (in usd per share)	26.87	26.87	30.52
Forfeited, Weighted Average Grant Date Fair Value (in usd per share)	0	0	30.44
Non-vested shares, Weighted Average Grant Date Fair Value, Ending Balance (in usd per share)	$ 19.95	$ 25.20	$ 26.38
Stock-based compensation expense	$ 137	$ 456	$ 2,895
Performance share units | Other
Weighted Average Grant Date Fair Value
Stock-based compensation expense			$ 200

Stock-Based Compensation Stock-

Stock-Based Compensation Stock-Based Compensation - PSUs Settled (Details) - Performance share units	12 Months Ended
	Dec. 31, 2017shares	Dec. 31, 2016shares	Dec. 31, 2015shares
2,013
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Net Number of Issued Shares upon Vesting (in shares)		38,706	8,768
Shares Withheld to Settle Tax Withholding Obligations (in shares)		1,572	3,954
2013 | Minimum
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
TSR Multiple Range		0.63	1.75
Russell 3000 Multiple		0	2
2013 | Maximum
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
TSR Multiple Range		1	1.75
Russell 3000 Multiple		0	2
2,014
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Net Number of Issued Shares upon Vesting (in shares)	6,476	11,487	2,506
Shares Withheld to Settle Tax Withholding Obligations (in shares)	3,573	0	1,145
2014 | Minimum
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
TSR Multiple Range	0.75	0.63	0.63
Russell 3000 Multiple	0	0	0
2014 | Maximum
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
TSR Multiple Range	1	0.63	0.75
Russell 3000 Multiple	0	0	0.75
2,015
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Net Number of Issued Shares upon Vesting (in shares)	3,869	13,529
Shares Withheld to Settle Tax Withholding Obligations (in shares)	2,310	0
2015 | Minimum
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
TSR Multiple Range	0.60	0.50
Russell 3000 Multiple	0	0
2015 | Maximum
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
TSR Multiple Range	0.60	0.50
Russell 3000 Multiple	0	0

Property and Equipment - Accumu

Property and Equipment - Accumulated Depreciation (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016
Property, Plant and Equipment [Line Items]
Total property and equipment, gross	$ 1,896	$ 3,655
Less accumulated depreciation and amortization	(1,486)	(2,920)
Total property and equipment, net	$ 410	735
Minimum
Property, Plant and Equipment [Line Items]
Life in Years	2 years
Maximum
Property, Plant and Equipment [Line Items]
Life in Years	7 years
Machinery and equipment
Property, Plant and Equipment [Line Items]
Total property and equipment, gross	$ 1,429	1,634
Machinery and equipment | Minimum
Property, Plant and Equipment [Line Items]
Life in Years	2 years
Machinery and equipment | Maximum
Property, Plant and Equipment [Line Items]
Life in Years	7 years
Leasehold improvements
Property, Plant and Equipment [Line Items]
Life in Years	3 years
Total property and equipment, gross	$ 205	1,244
Furniture and fixtures
Property, Plant and Equipment [Line Items]
Total property and equipment, gross	$ 262	$ 777
Furniture and fixtures | Minimum
Property, Plant and Equipment [Line Items]
Life in Years	3 years
Furniture and fixtures | Maximum
Property, Plant and Equipment [Line Items]
Life in Years	7 years

Property and Equipment - Additi

Property and Equipment - Additional Information (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Property, Plant and Equipment [Line Items]
Depreciation expense	$ 0.7	$ 0.9	$ 1.7
Depreciation		0.2
Disposed of by Sale | General and Administrative Expense
Property, Plant and Equipment [Line Items]
Impairment charges		$ 0.5

Costs and Billings on Uncompl82

Costs and Billings on Uncompleted Contracts (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Cost and Billings on Uncompleted Contracts [Line Items]
Costs incurred on uncompleted contracts (gross)	$ 15,945	$ 42,993
Billings on uncompleted contracts (gross)	(17,775)	(47,915)
Total deferred revenue	(1,830)	(4,922)
Costs in excess of billings on uncompleted contracts	0	25
Billings in excess of costs on uncompleted contracts	(1,830)	(4,947)
Provision for loss on uncompleted contracts	100	200
Other current liabilities
Cost and Billings on Uncompleted Contracts [Line Items]
Loss on contracts provisions	$ 100	$ 400	$ 300

Research and Development and 83

Research and Development and Government and Industry Funded Contracts (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Government and Industry Funded Contracts [Abstract]
Research and development expense	$ 979	$ 173	$ 6,737
Changes due to amount and timing of ARO reclamation	822	0	0
DOE funding	0	821	1,375
Research and development expense, net	157	(648)	5,362
Business Acquisition [Line Items]
Asset impairment charges	$ 464	$ 2,280	2,087
ADA Analytics Israel, LLC
Business Acquisition [Line Items]
Asset impairment charges			$ 1,900

Supplemental Financial Inform84

Supplemental Financial Information - Prepaid expenses and other assets and Other assets (Details) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Other current assets:
Prepaid expenses	$ 1,678	$ 1,169
Inventory	74	16
Costs in excess of billings	0	25
Other	83	172
Other current assets	1,835	1,382
Other long-term assets:
Deposits	223	263
Intangibles	805	696
Cost method investment	552	1,016
Other long-term assets	728	323
Total	$ 2,308	$ 2,298

Supplemental Financial Inform85

Supplemental Financial Information - Additional Information (Details) $ in Thousands	1 Months Ended	12 Months Ended
	Nov. 30, 2014USD ($)	Dec. 31, 2017USD ($)	Dec. 31, 2016USD ($)	Dec. 31, 2015USD ($)	Dec. 31, 2017£ / shares	Dec. 31, 2016£ / shares
Investment [Line Items]
Asset impairment charges		$ 464	$ 2,280	$ 2,087
Highview Enterprises Limited
Investment [Line Items]
Ownership interest, percent	8.00%
Payments to acquire investments	$ 2,800
Highview Enterprises Limited | Cost method investment
Investment [Line Items]
Asset impairment charges		$ 500	$ 1,800
Share price, estimated fair value (amount per share) | £ / shares					£ 1	£ 2
Share price (amount per shares) | £ / shares						£ 4.25

Supplemental Financial Inform86

Supplemental Financial Information - Schedule of Intangible Assets (Details) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Finite-Lived Intangible Assets [Line Items]
Initial Cost	$ 1,079	$ 2,438
Net of Accumulated Amortization	805	696
Patents
Finite-Lived Intangible Assets [Line Items]
Initial Cost	1,079	913
Net of Accumulated Amortization	805	696
Licensed technology
Finite-Lived Intangible Assets [Line Items]
Initial Cost	0	1,525
Net of Accumulated Amortization	$ 0	$ 0

Supplemental Financial Inform87

Supplemental Financial Information - Intangible Assets (Details) $ in Thousands, £ in Millions	12 Months Ended
	Dec. 31, 2017USD ($)	Dec. 31, 2016USD ($)	Dec. 31, 2015USD ($)	Dec. 31, 2016GBP (£)
Finite-Lived Intangible Assets [Line Items]
Amortization expense	$ 100	$ 100	$ 400
Estimated future amortization, year one	100
Estimated future amortization, year two	100
Estimated future amortization, year three	100
Estimated future amortization, year four	100
Estimated future amortization, year five	100
Gain on contract termination	$ 0	891	$ 0
Highview Enterprises Limited | Licensed technology
Finite-Lived Intangible Assets [Line Items]
Long-term licensing agreement, termination fee		$ 200		£ 0.2

Supplemental Financial Inform88

Supplemental Financial Information - Other Liabilities (Details) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Other current liabilities:
Estimated Company contribution to 401(k) Plan	$ 1,000	$ 0
Accrued interest	0	618
Accrued losses on equipment contracts	69	183
Taxes payable	207	244
Deferred revenue	0	76
Warranty liabilities	316	287
Deferred rent	0	369
Asset retirement obligation	0	1,312
Other	1,072	928
Other current liabilities	2,664	4,017
Other long-term liabilities:
Deferred revenue, related party	2,000	2,000
Deferred rent	192	38
Other long-term liabilities	93	0
Total other long-term liabilities	$ 2,285	$ 2,038

Supplemental Financial Inform89

Supplemental Financial Information - Warranty Obligations (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016
Movement in Standard Product Warranty Accrual [Roll Forward]
Beginning balance	$ 287	$ 1,197
Warranties accrued, net	580	89
Warranty claims	(635)	(899)
Change in estimate related to previous warranties accrued	84	(100)
Ending balance	$ 316	$ 287

Supplemental Financial Inform90

Supplemental Financial Information - Asset Retirement Obligation (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016
Asset Retirement Obligation, Roll Forward Analysis [Roll Forward]
Asset retirement obligation, beginning of year	$ 1,312	$ 1,248
Accretion	37	64
Liabilities settled	(527)	0
Changes due to scope and timing of reclamation	(822)	0
Asset retirement obligations, end of year	$ 0	$ 1,312

Supplemental Financial Inform91

Supplemental Financial Information - Supplemental Income Statement - Interest Expense (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Deferred Costs, Capitalized, Prepaid, and Other Assets Disclosure [Abstract]
453A interest	$ 2,555	$ 2,490	$ 4,639
Line of Credit interest and letters of credit fees	417	89	49
Credit Agreement interest	0	2,112	1,180
Interest on RCM6 Note Payable, related party	0	263	2,468
Other	52	112	66
Interest expense	$ 3,024	$ 5,066	$ 8,402

Supplemental Financial Inform92

Supplemental Financial Information Supplemental Financial Information - Supplemental Income Statement - Other (Details) - USD ($) $ in Thousands	Nov. 06, 2017	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Deferred Costs, Capitalized, Prepaid, and Other Assets Disclosure [Abstract]
Impairment of cost method investment		$ (464)	$ (1,760)	$ 0
Settlement agreement	$ 3,500	3,500	0	0
Estimate of Company contribution to 401(k) Plan		(1,000)	0	0
Gain on sale of equity method investment		0	2,078	0
Gain on settlement of note payable and licensed technology		0	1,019	0
Gain on termination of sales-type lease		0	891	0
Other		(11)	235	494
Other nonoperating income (expense)		$ 2,025	$ 2,463	$ 494

Fair Value Measurements - Addit

Fair Value Measurements - Additional Information (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015	Mar. 31, 2015
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Time deposits, $250,000 or more	$ 250
Asset impairment charges	464	$ 2,280	$ 2,087
Note receivable				$ 1,000
Interest rate				8.00%
Highview Enterprises Limited | Cost method investment
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Asset impairment charges	$ 500	1,800
Equipment sales cost of revenue
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Asset impairment charges		800
Disposed of by Sale
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Proceeds from sale of impaired assets		100
Disposed of by Sale | General and Administrative Expense
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Impairment charges		$ 500

Fair Value Measurements - Estim

Fair Value Measurements - Estimated Fair Value of Financial Instruments (Details) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Carrying Value
Financial Instruments:
Highview Investment	$ 552	$ 1,016
Highview Obligation	210	207
Fair Value
Financial Instruments:
Highview Investment	552	1,016
Highview Obligation	$ 210	$ 207

Income Taxes - Additional Infor

Income Taxes - Additional Information (Details) - USD ($) $ in Thousands	Dec. 22, 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
Operating Loss Carryforwards [Line Items]
Tax Cuts and Jobs Act of 2017, limitations on net operating losses to percent of taxable income		80.00%								80.00%
Tax Cuts and Jobs Act of 2017, change in deferred tax assets	$ 5,800
Effective tax rate										46.00%	(166.00%)	0.00%
Income tax expense (benefit)		$ 11,538	$ 3,586	$ 3,642	$ 5,386	$ (61,673)	$ 583	$ 99	$ 53	$ 24,152	$ (60,938)	$ 20
Tax Cuts and Jobs Act of 2017, income tax expense		5,800								5,800
Changes in tax rates										5,818	(125)	$ (243)
Valuation allowance adjustments											61,400
Net deferred tax assets		$ 38,661				61,396				38,661	61,396
Release of valuation allowance						$ 61,400				500	61,400
Period increase (decrease)											$ (11,000)
Domestic Tax Authority
Operating Loss Carryforwards [Line Items]
Income tax expense (benefit)										$ 19,900

Income Taxes - Income Tax Benef

Income Taxes - Income Tax Benefit (Expense) from Continuing Operations (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
Current portion of income tax expense:
Federal									$ 519	$ 0	$ 0
State									894	458	20
Current portion of income tax expense	$ 5,700								1,413	458	20
Deferred portion of income tax (benefit) expense:
Federal									23,003	(61,396)	0
State									(264)	0	0
Deferred portion of income tax (benefit) expense									22,739	(61,396)	0
Total income tax (benefit) expense	$ 11,538	$ 3,586	$ 3,642	$ 5,386	$ (61,673)	$ 583	$ 99	$ 53	$ 24,152	$ (60,938)	$ 20
Effective tax rate									46.00%	(166.00%)	0.00%

Income Taxes - Reconciliation o

Income Taxes - Reconciliation of Expected Federal Income Taxes at Statutory Rates (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
Amount
Federal statutory rate									$ 18,209	$ 12,859	$ (10,542)
State income taxes, net of federal benefit									1,721	987	(781)
Permanent differences									777	84	35
Tax credits									(1,949)	(2,419)	(38,998)
Valuation allowances									(474)	(72,359)	50,066
Changes in tax rates									5,818	(125)	(243)
Stock-based compensation									303	36	487
Other									(253)	(1)	(4)
Total income tax (benefit) expense	$ 11,538	$ 3,586	$ 3,642	$ 5,386	$ (61,673)	$ 583	$ 99	$ 53	$ 24,152	$ (60,938)	$ 20
Effective tax rate									46.00%	(166.00%)	0.00%

Income Taxes - Deferred Tax Ass

Income Taxes - Deferred Tax Assets And Liabilities (Details) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Deferred tax assets
Tax credits	$ 100,367	$ 99,903
Deferred revenues and loss contract provisions	906	268
Employee related liabilities	393	3,796
Intangible assets	914	1,518
Equity method investments	8,457	12,326
Net operating loss carryforwards	2,004	13,341
Settlement and Royalty Indemnification	0	4,264
Other investments	563	680
Other	648	1,429
Total deferred tax assets	114,252	137,525
Less valuation allowance	(75,436)	(75,910)
Deferred tax assets	38,816	61,615
Less: Deferred tax liabilities
Property and equipment and other	(155)	(219)
Total deferred tax liabilities	(155)	(219)
Net deferred tax assets	$ 38,661	$ 61,396

Income Taxes - Net Operating Lo

Income Taxes - Net Operating Loss Carryforwards and Tax Credit Carryforwards (Details) $ in Thousands	Dec. 31, 2017USD ($)
State
Income Taxes [Line Items]
Net operating loss carryforwards	$ 41,071
Federal
Income Taxes [Line Items]
Tax credit carryforwards	$ 100,367

Income Taxes - Unrecognized Tax

Income Taxes - Unrecognized Tax Benefits (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Reconciliation of Unrecognized Tax Benefits, Excluding Amounts Pertaining to Examined Tax Returns [Roll Forward]
Balance as of January 1	$ 54	$ 0	$ 0
Increases for tax positions of current year	0	54	0
Balance as of December 31	$ 54	$ 54	$ 0

Business Segment Information -

Business Segment Information - Segment Operating Results (Details) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2017USD ($)	Sep. 30, 2017USD ($)	Jun. 30, 2017USD ($)	Mar. 31, 2017USD ($)	Dec. 31, 2016USD ($)	Sep. 30, 2016USD ($)	Jun. 30, 2016USD ($)	Mar. 31, 2016USD ($)	Dec. 31, 2017USD ($)segment	Dec. 31, 2016USD ($)	Dec. 31, 2015USD ($)
Segment Reporting Information [Line Items]
Number of reportable segments | segment									2
Revenues:
Earnings from equity method investments	$ 17,754	$ 12,120	$ 10,155	$ 13,814	$ 15,518	$ 10,735	$ 13,754	$ 5,577	$ 53,843	$ 45,584	$ 8,921
Equipment sales									31,401	46,949	60,099
Consulting services									45	648	1,752
Royalties, related party	3,247	2,804	1,866	1,755	2,203	2,064	669	1,189	9,672	6,125	10,642
Chemicals									4,246	3,025	888
Total reported revenues	544	2,294	25,465	7,389	3,604	15,710	8,951	22,357	35,692	50,622	62,739
Segment reporting operating income (loss)
Segment operating income (loss)	$ (4,309)	$ (3,944)	$ (1,850)	$ (3,711)	$ (5,262)	$ (2,913)	$ (4,612)	(3,311)	(13,814)	(16,098)	(41,800)
Gain on sale of equity method investment									0	2,078	0
453A interest									2,555	2,490	4,639
Interest on RCM6 Note Payable, related party									0	263	2,468
Gain on contract termination									0	891	0
RCM6, LLC (RCM6)
Revenues:
Earnings from equity method investments								$ (600)
Operating Segments
Revenues:
Total reported revenues									99,207	102,331	82,302
Segment reporting operating income (loss)
Segment operating income (loss)									60,287	58,598	4,548
Refined Coal | RCM6, LLC (RCM6)
Segment reporting operating income (loss)
Gain on sale of equity method investment										2,100
Interest on RCM6 Note Payable, related party										300	2,500
Refined Coal | Operating Segments
Revenues:
Earnings from equity method investments									53,843	45,584	8,921
Consulting services									0	0	55
Royalties, related party									9,672	6,125	10,642
Total reported revenues									63,515	51,709	19,618
Segment reporting operating income (loss)
Segment operating income (loss)									59,908	51,264	12,131
Refined Coal | Intersegment Eliminations
Revenues:
Earnings from equity method investments									(53,843)	(45,584)	(8,921)
Royalties, related party									(9,672)	(6,125)	(10,642)
Total reported revenues									(63,515)	(51,709)	(19,563)
Emissions Control | Operating Segments
Revenues:
Equipment sales									31,401	46,949	60,099
Consulting services									45	648	1,697
Chemicals									4,246	3,025	888
Total reported revenues									35,692	50,622	62,684
Segment reporting operating income (loss)
Segment operating income (loss)									$ 379	7,334	$ (7,583)
Gain on contract termination										$ 900

Business Segment Information102

Business Segment Information - Reconciliation of Reportable Segment Amounts (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
Segment Reporting Information [Line Items]
Total reported segment operating income	$ (4,309)	$ (3,944)	$ (1,850)	$ (3,711)	$ (5,262)	$ (2,913)	$ (4,612)	$ (3,311)	$ (13,814)	$ (16,098)	$ (41,800)
Corporate payroll and benefits									(7,669)	(12,390)	(23,589)
Corporate rent and occupancy									(795)	(2,168)	(3,309)
Corporate legal and professional fees									(4,354)	(8,293)	(16,604)
Corporate general and administrative									(3,857)	(3,721)	(6,104)
Corporate depreciation and amortization									(789)	(979)	(2,019)
Corporate interest (expense) income, net									54	268	24
Other income (expense), net									2,025	2,463	494
Income tax (expense) benefit	(11,538)	(3,586)	(3,642)	(5,386)	61,673	(583)	(99)	(53)	(24,152)	60,938	(20)
Net income (loss)	$ 6,985	$ 5,792	$ 6,408	$ 8,688	$ 75,830	$ 9,612	$ 7,860	$ 4,376	27,873	97,678	(30,141)
Operating Segments
Segment Reporting Information [Line Items]
Total reported segment operating income									60,287	58,598	4,548
Segment Reconciling Items
Segment Reporting Information [Line Items]
Corporate payroll and benefits									(5,565)	(9,415)	(14,842)
Corporate rent and occupancy									(293)	(1,187)	(707)
Corporate legal and professional fees									(4,010)	(8,230)	(15,199)
Corporate general and administrative									(3,400)	(3,811)	(3,640)
Corporate depreciation and amortization									(342)	(608)	(578)
Corporate interest (expense) income, net									(432)	(2,334)	24
Other income (expense), net									5,780	3,727	273
Income tax (expense) benefit									$ (24,152)	$ 60,938	$ (20)

Business Segment Information103

Business Segment Information - Segment Assets (Details) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Segment Reporting Information [Line Items]
Assets	$ 82,618	$ 107,296
Equity method investments	4,351	3,959
Operating Segments
Segment Reporting Information [Line Items]
Assets	11,847	30,861
Operating Segments | Refined Coal
Segment Reporting Information [Line Items]
Assets	8,092	6,310
Operating Segments | Emissions Control
Segment Reporting Information [Line Items]
Assets	3,755	24,551
All Other and Corporate
Segment Reporting Information [Line Items]
Assets	$ 70,771	$ 76,435

Major Customers (Details)

Major Customers (Details) - Sales	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Customer A
Revenue, Major Customer [Line Items]
Major customer percentage	62.00%	21.00%	3.00%
Customer B
Revenue, Major Customer [Line Items]
Major customer percentage	0.00%	14.00%	16.00%
Customer C
Revenue, Major Customer [Line Items]
Major customer percentage	0.00%	0.00%	11.00%
Customer D
Revenue, Major Customer [Line Items]
Major customer percentage	0.00%	0.00%	15.00%

Related Party Transactions - Ad

Related Party Transactions - Additional Information (Details) $ in Thousands, £ in Millions	1 Months Ended	3 Months Ended
	Feb. 29, 2016USD ($)	Mar. 31, 2016USD ($)	Dec. 31, 2017USD ($)	Dec. 31, 2016USD ($)	Dec. 31, 2016GBP (£)
Related Party Transaction [Line Items]
Deferred revenue, related party			$ 2,000	$ 2,000
Licensed technology | Highview Enterprises Limited
Related Party Transaction [Line Items]
Long-term licensing agreement, termination fee				$ 200	£ 0.2
Affiliated Entity
Related Party Transaction [Line Items]
Payable to related party	$ 1,100
Extinguishment of debt, amount	$ 300	$ 300
Arch
Related Party Transaction [Line Items]
Deferred revenue, related party			2,000
Fees related to related party agreement			$ 300

Related Party Transactions - Am

Related Party Transactions - Amounts Recorded to Related Party (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
Related Party Transaction [Line Items]
Royalties, related party	$ 3,247	$ 2,804	$ 1,866	$ 1,755	$ 2,203	$ 2,064	$ 669	$ 1,189	$ 9,672	$ 6,125	$ 10,642
Tinuum Group
Related Party Transaction [Line Items]
Receivable from related party	$ 3,247				$ 1,934				3,247	1,934
Royalties, related party									$ 9,672	$ 6,125	$ 10,642

Defined Contributions Saving107

Defined Contributions Savings Plan (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
401(k) Plan employer contributions
Defined Benefit Plan Disclosure [Line Items]
Employer expense	$ 56	$ 172	$ 439

Acquisition - Additional Inform

Acquisition - Additional Information (Details) - USD ($) $ in Thousands	Mar. 06, 2015	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Business Acquisition [Line Items]
Asset impairment charges		$ 464	$ 2,280	$ 2,087
ADA Analytics Israel, LLC
Business Acquisition [Line Items]
Cash paid	$ 2,360
Cash paid to acquire business, VAT tax	$ 400
Asset impairment charges				$ 1,900

Acquisition - Consideration and

Acquisition - Consideration and Allocation (Details) - ADA Analytics Israel, LLC $ in Thousands	Mar. 06, 2015USD ($)
Business Acquisition [Line Items]
Cash paid	$ 2,360
Accrued liabilities	10
Contingent consideration	451
Total fair value of liabilities assumed	461
Total purchase consideration	2,821
Receivables	360
Property and equipment and other	82
Intangibles - in process research and development	2,379
Total	$ 2,821

Restructuring - Net Pretax Bene

Restructuring - Net Pretax Benefits (Charges), Incurred by Segment (Details) $ in Thousands	12 Months Ended
	Dec. 31, 2016USD ($)employee	Dec. 31, 2015USD ($)employee
Restructuring Cost and Reserve [Line Items]
Approximate Number of Employees | employee	40	162
Restructuring charges	$ 2,045	$ 10,372
Changes in estimates	(486)	(12)
Total pretax charge, net of reversals	1,559	10,360
All Other and Corporate
Restructuring Cost and Reserve [Line Items]
Restructuring charges	881	5,264
Changes in estimates	(276)	(2)
Total pretax charge, net of reversals	605	5,262
Refined Coal | Operating Segments
Restructuring Cost and Reserve [Line Items]
Restructuring charges	0	0
Changes in estimates	0	0
Total pretax charge, net of reversals	0	0
Emissions Control | Operating Segments
Restructuring Cost and Reserve [Line Items]
Restructuring charges	1,164	5,108
Changes in estimates	(210)	(10)
Total pretax charge, net of reversals	$ 954	$ 5,098

Restructuring - Utilization of

Restructuring - Utilization of Restructuring Accruals (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Restructuring Reserve [Roll Forward]
Share-based compensation	$ 0	$ 400	$ 3,400
Asset impairment charges	464	2,280	2,087
ADA Analytics Israel, LLC
Restructuring Reserve [Roll Forward]
Asset impairment charges			1,900
Employee Severance
Restructuring Reserve [Roll Forward]
Accrual, Beginning balance	452	2,581	1,690
Expense provision	56	2,045	8,498
Cash payments and other	(508)	(3,898)	(7,595)
Change in estimates	0	(276)	(12)
Accrual, Ending balance	0	452	2,581
Facility Closures
Restructuring Reserve [Roll Forward]
Accrual, Beginning balance	247	777	0
Expense provision	0	0	2,650
Cash payments and other	(250)	(320)	(1,873)
Change in estimates	3	(210)	0
Accrual, Ending balance	$ 0	$ 247	$ 777

Quarterly Financial Results 112

Quarterly Financial Results (unaudited) (Details) - USD ($) $ / shares in Units, shares in Thousands, $ 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
Quarterly Financial Information Disclosure [Abstract]
Revenues	$ 544	$ 2,294	$ 25,465	$ 7,389	$ 3,604	$ 15,710	$ 8,951	$ 22,357	$ 35,692	$ 50,622	$ 62,739
Cost of revenues, exclusive of operating expenses shown below	648	2,041	23,295	5,901	3,478	13,259	5,769	17,311
Other operating expenses	4,205	4,197	4,020	5,199	5,388	5,364	7,794	8,357
Operating loss	(4,309)	(3,944)	(1,850)	(3,711)	(5,262)	(2,913)	(4,612)	(3,311)	(13,814)	(16,098)	(41,800)
Earnings from equity method investments	17,754	12,120	10,155	13,814	15,518	10,735	13,754	5,577	53,843	45,584	8,921
Royalties, related party	3,247	2,804	1,866	1,755	2,203	2,064	669	1,189	9,672	6,125	10,642
Other income (expenses), net	1,831	(1,602)	(121)	2,216	1,698	309	(1,852)	974
Income before income tax expense	18,523	9,378	10,050	14,074	14,157	10,195	7,959	4,429	52,025	36,740	(30,121)
Income tax (benefit) expense	11,538	3,586	3,642	5,386	(61,673)	583	99	53	24,152	(60,938)	20
Net income (loss)	$ 6,985	$ 5,792	$ 6,408	$ 8,688	$ 75,830	$ 9,612	$ 7,860	$ 4,376	$ 27,873	$ 97,678	$ (30,141)
Net income (loss) per common share – basic (in dollars per share)	$ 0.34	$ 0.28	$ 0.29	$ 0.39	$ 3.45	$ 0.44	$ 0.36	$ 0.20	$ 1.30	$ 4.40	$ (1.37)
Net income (loss) per common share – diluted (in dollars per share)	$ 0.33	$ 0.28	$ 0.29	$ 0.39	$ 3.39	$ 0.43	$ 0.35	$ 0.20	$ 1.29	$ 4.34	$ (1.37)
Weighted-average number of common shares outstanding:
Basic (in shares)	20,767	20,808	21,866	22,056	21,693	21,740	21,875	21,849	21,367	21,931	21,773
Diluted (in shares)	20,864	20,854	21,880	22,243	22,061	22,098	22,187	22,177	21,413	22,234	21,773
Current portion of income tax expense	$ 5,700								$ 1,413	$ 458	$ 20
Tax Cuts and Jobs Act of 2017, income tax expense	$ 5,800								5,800
Reduction to royalty award accrual					$ 4,000
Release of valuation allowance					$ 61,400				$ 500	$ 61,400

Subsequent Events (Details)

Subsequent Events (Details) - $ / shares	Feb. 08, 2018	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Subsequent Event [Line Items]
Dividends declared (in dollars per share)		$ 0.25	$ 0.25	$ 0.25	$ 0.75	$ 0	$ 0
Subsequent Event
Subsequent Event [Line Items]
Dividends declared (in dollars per share)	$ 0.25