Energy Recovery (ERII) 10-K 6 Mar 20 2019 FY Annual report Financial data

Cover Page

Cover Page - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2019	Feb. 27, 2020	Jun. 30, 2019
Cover page.
Document Type	10-K
Document Annual Report	true
Document Period End Date	Dec. 31, 2019
Document Transition Report	false
Entity File Number	001-34112
Entity Registrant Name	Energy Recovery, Inc.
Entity Incorporation, State or Country Code	DE
Entity Tax Identification Number	01-0616867
Entity Address, Address Line One	1717 Doolittle Drive
Entity Address, City or Town	San Leandro
Entity Address, State or Province	CA
Entity Address, Postal Zip Code	94577
City Area Code	510
Local Phone Number	483-7370
Title of 12(b) Security	Common Stock, $0.001 par value per share
Trading Symbol	ERII
Security Exchange Name	NASDAQ
Entity Well-known Seasoned Issuer	No
Entity Voluntary Filers	No
Entity Current Reporting Status	Yes
Entity Interactive Data Current	Yes
Entity Filer Category	Accelerated Filer
Entity Small Business	false
Entity Emerging Growth Company	false
Entity Shell Company	false
Entity Public Float			$ 389
Entity Common Stock, Shares Outstanding		55,492,350
Entity Central Index Key	0001421517
Current Fiscal Year End Date	--12-31
Document Fiscal Year Focus	2019
Document Fiscal Period Focus	FY
Amendment Flag	false
Documents Incorporated by Reference	DOCUMENTS INCORPORATED BY REFERENCE As noted herein, the information called for by Part III is incorporated by reference to specified portions of the registrant’s definitive proxy statement to be filed in conjunction with the registrant’s 2020 Annual Meeting of Stockholders, which is expected to be filed not later than 120 days after the registrant’s fiscal year ended December 31, 2019 .

Consolidated Balance Sheets

Consolidated Balance Sheets - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018
Current assets:
Cash, cash equivalents and restricted cash	$ 26,387	$ 22,052
Short-term investments	58,736	73,338
Accounts receivable, net of allowance for doubtful accounts of $308 and $396 at December 31, 2019 and December 31, 2018, respectively	12,979	10,212
Contract assets	501	4,083
Inventories, net	10,317	7,138
Prepaid expenses and other current assets	4,047	2,825
Total current assets	112,967	119,648
Contract assets, non-current	191	0
Long-term investments	15,419	1,269
Deferred tax assets, non-current	16,897	18,318
Property and equipment, net	18,843	14,619
Operating lease, right of use asset	11,195	12,189
Goodwill	12,790	12,790
Other intangible assets, net	65	640
Other assets, non-current	407	368
Total assets	188,774	179,841
Current liabilities:
Accounts payable	1,192	1,439
Accrued expenses and other current liabilities	9,869	8,497
Lease liabilities	1,023	926
Contract liabilities	15,746	16,270
Total current liabilities	27,830	27,132
Lease liabilities, non-current	11,533	12,556
Contract liabilities, non-current	13,120	26,539
Other non-current liabilities	278	236
Total liabilities	52,761	66,463
Commitments and contingencies (Note 8)
Stockholders’ equity:
Preferred stock, $0.001 par value; 10,000,000 shares authorized; no shares issued or outstanding at December 31, 2019 and December 31, 2018	0	0
Common stock, $0.001 par value; 200,000,000 shares authorized; 60,717,702 shares issued and 55,261,767 shares outstanding at December 31, 2019 and 59,396,020 shares issued and 53,940,085 shares outstanding at December 31, 2018	61	59
Additional paid-in capital	170,028	158,404
Accumulated other comprehensive loss	(37)	(133)
Treasury stock, at cost, 5,455,935 shares repurchased at December 31, 2019 and 2018	(30,486)	(30,486)
Accumulated deficit	(3,553)	(14,466)
Total stockholders’ equity	136,013	113,378
Total liabilities and stockholders’ equity	$ 188,774	$ 179,841

Condensed Consolidated Balance

Condensed Consolidated Balance Sheets (Parentheticals) - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018
Statement of Financial Position [Abstract]
Allowance for doubtful accounts	$ 308	$ 396
Preferred stock, par value (in dollars per share)	$ 0.001	$ 0.001
Preferred stock, shares authorized (in shares)	10,000,000	10,000,000
Preferred stock, shares issued (in shares)	0	0
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)	200,000,000	200,000,000
Common stock, shares issued (in shares)	60,717,702	59,396,020
Common stock, shares outstanding (in shares)	55,261,767	53,940,085
Treasury stock, at cost, shares (in shares)	5,455,935	5,455,935

Consolidated Statements of Oper

Consolidated Statements of Operations - USD ($) shares in Thousands, $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Revenue	$ 86,942	$ 74,515	$ 69,129
Operating expenses:
General and administrative	22,832	21,476	17,354
Sales and marketing	9,434	7,546	9,391
Research and development	23,402	17,012	13,443
Amortization of intangible assets	575	630	631
Total operating expenses	56,243	46,664	40,819
Income from operations	10,364	9,978	9,249
Other income (expense):
Interest income	2,010	1,543	870
Interest expense	0	(1)	(2)
Other non-operating expense, net	(118)	(80)	(188)
Total other income, net	1,892	1,462	680
Income before income taxes	12,256	11,440	9,929
Provision for (benefit from) income taxes	1,343	(10,653)	(8,425)
Net income	$ 10,913	$ 22,093	$ 18,354
Earnings per share:
Basic (in dollars per share)	$ 0.20	$ 0.41	$ 0.34
Diluted (in dollars per share)	$ 0.19	$ 0.40	$ 0.33
Number of shares used in per share calculations:
Basic (in shares)	54,740	53,764	53,701
Diluted (in shares)	56,067	55,338	55,612
Product
Revenue	$ 72,834	$ 61,025	$ 58,023
Product cost of revenue	20,335	17,873	19,061
Product gross profit	52,499	43,152	38,962
License and development revenue
Revenue	$ 14,108	$ 13,490	$ 11,106

Consolidated Statements of Comp

Consolidated Statements of Comprehensive Income - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Statement of Comprehensive Income [Abstract]
Net income	$ 10,913	$ 22,093	$ 18,354
Other comprehensive income (loss), net of tax
Foreign currency translation adjustments	(23)	(12)	57
Unrealized gain (loss) on investments	119	4	(64)
Other comprehensive income (loss), net of tax	96	(8)	(7)
Comprehensive income	$ 11,009	$ 22,085	$ 18,347

Consolidated Statements of Cash

Consolidated Statements of Cash Flows - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Cash flows from operating activities:
Net income	$ 10,913	$ 22,093	$ 18,354
Adjustments to reconcile net income to cash provided by operating activities
Stock-based compensation	5,676	5,240	4,087
Depreciation and amortization	4,395	3,869	3,666
Amortization of premiums and discounts on investments	65	362	460
Foreign currency transactions	(27)	(10)	144
Realized gain on sale of investments	(10)	0	0
Provision for warranty claims	402	326	246
Reversal of accruals related to expired warranties	(193)	(180)	(200)
Change in allowance for doubtful accounts	(88)	336	55
Adjustments for excess or obsolete inventory	21	197	201
Deferred income taxes	1,421	(10,385)	(8,865)
Loss on disposal of fixed assets	389	408	0
Other non-cash adjustments	0	0	(196)
Changes in operating assets and liabilities:
Accounts receivable, net	(2,679)	1,917	(761)
Contract assets	3,391	2,196	(4,263)
Inventories, net	(3,256)	(1,872)	(1,250)
Prepaid and other assets	(263)	(682)	(39)
Accounts payable	(373)	(2,274)	2,118
Accrued expenses and other liabilities	(600)	87	611
Income taxes	27	(447)	385
Contract liabilities	(13,943)	(13,616)	(11,858)
Net cash provided by operating activities	5,268	7,565	2,895
Cash flows from investing activities:
Sales of marketable securities	7,608	0	0
Maturities of marketable securities	78,100	81,268	49,106
Purchases of marketable securities	(85,207)	(86,192)	(80,641)
Capital expenditures	(7,382)	(5,235)	(7,376)
Net cash used in investing activities	(6,881)	(10,159)	(38,911)
Cash flows from financing activities:
Net proceeds from issuance of common stock	6,073	4,291	5,508
Tax payment for employee shares withheld	(110)	(150)	(270)
Repayment of long-term debt	0	(27)	(11)
Repurchase of common stock	0	(10,000)	(4,276)
Net cash provided by (used in) financing activities	5,963	(5,886)	951
Effect of exchange rate differences on cash and cash equivalents	0	(8)	(57)
Net change in cash, cash equivalents and restricted cash	4,350	(8,488)	(35,122)
Cash, cash equivalents and restricted cash, beginning of year	22,138	30,626	65,748
Cash, cash equivalents and restricted cash, end of year	26,488	22,138	30,626
Supplemental disclosure of cash flow information:
Cash paid for interest	0	1	2
Cash received for income tax refunds	438	13	16
Cash paid for income taxes	52	610	57
Supplemental disclosure on non-cash transactions:
Purchases of property and equipment in trade accounts payable, and accrued expenses and other liabilities	1,080	30	475
Non-cash lease liabilities arising from obtaining right of use assets	$ 0	$ 10,411	$ 0

Consolidated Statements of Stoc

Consolidated Statements of Stockholders' Equity - USD ($) $ in Thousands		Total	Common stock	Additional paid-in capital	Accumulated other comprehensive loss	Treasury stock	Accumulated deficit
Beginning Balance at Dec. 31, 2016			$ 57	$ 139,676	$ (118)	$ (16,210)	$ (54,913)
Beginning balance (in shares) at Dec. 31, 2016			56,884,000			(3,722,000)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Issuance of common stock, net			$ 1	5,237
Stock-based compensation				4,093
Foreign currency translation adjustments					57
Unrealized gain (loss) on investments					(64)
Total other comprehensive income (loss), net		$ (7)			(7)
Repurchase of common stock for treasury						$ (4,276)
Net income		18,354					18,354
Issuance of common stock (in shares)			1,284,000
Repurchase of common stock for treasury (in shares)	[1]					(541,000)
Ending balance (in shares) at Dec. 31, 2017			58,168,000			(4,263,000)
Ending Balance at Dec. 31, 2017		91,894	$ 58	149,006	(125)	$ (20,486)	(36,559)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Issuance of common stock, net			$ 1	4,138
Stock-based compensation				5,260
Foreign currency translation adjustments					(12)
Unrealized gain (loss) on investments					4
Total other comprehensive income (loss), net		(8)			(8)
Repurchase of common stock for treasury						$ (10,000)
Net income		$ 22,093					22,093
Issuance of common stock (in shares)			1,228,000
Repurchase of common stock for treasury (in shares)	[1]					(1,193,000)
Ending balance (in shares) at Dec. 31, 2018		53,940,085	59,396,000			(5,456,000)
Ending Balance at Dec. 31, 2018		$ 113,378	$ 59	158,404	(133)	$ (30,486)	(14,466)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Issuance of common stock, net			$ 2	5,960
Stock-based compensation				5,664
Foreign currency translation adjustments					(23)
Unrealized gain (loss) on investments					119
Total other comprehensive income (loss), net		96			96
Repurchase of common stock for treasury						$ 0
Net income		$ 10,913					10,913
Issuance of common stock (in shares)			1,322,000
Repurchase of common stock for treasury (in shares)	[1]					0
Ending balance (in shares) at Dec. 31, 2019		55,261,767	60,718,000			(5,456,000)
Ending Balance at Dec. 31, 2019		$ 136,013	$ 61	$ 170,028	$ (37)	$ (30,486)	$ (3,553)
[1]	The March 2018 stock repurchase authorization expired in September 2018

Description of Business and Sig

Description of Business and Significant Accounting Policies	12 Months Ended
	Dec. 31, 2019
Accounting Policies [Abstract]
Description of Business and Significant Accounting Policies	Description of Business and Significant Accounting Policies Energy Recovery, Inc. and its wholly-owned subsidiaries (the “Company” or “Energy Recovery”) has, for more than 20 years, created technologies that solve complex challenges for industrial fluid flow markets worldwide . The Company design and manufacture solutions that reduce waste, improve operational efficiency, and lower the production costs of clean water and oil & gas . The Company’s solutions are marketed and sold in fluid flow markets such as water, oil & gas and chemical processing under the trademarks ERI ® , PX ® , Pressure Exchanger ® , PX Pressure Exchanger ® , VorTeq ™ , MTeq ™ , IsoBoost ® , IsoGen ® , AT ™ and AquaBold ™ . The Company owns, manufactures and/or develops its solutions, in whole or in part, in the United States of America (“U.S.”). Basis of Presentation The Company’s Consolidated Financial Statements include the accounts of the Company and its wholly-owned subsidiaries. All significant inter-company accounts and transactions have been eliminated in consolidation. Reclassifications The accompanying Consolidated Financial Statements have been prepared by the Company pursuant to the rules and regulations of the Securities and Exchange Commission (“SEC”). Certain prior period amounts have been reclassified in the balance sheet, statement of cash flows and footnotes to conform to the current period presentation. Use of Estimates The preparation of Consolidated Financial Statements, in conformity with the U.S. generally accepted accounting principles (“U.S. GAAP”), requires the Company’s management to make judgments, assumptions and estimates that affect the amounts reported in the Consolidated Financial Statements and accompanying notes. The accounting policies that reflect the Company’s more significant estimates and judgments and that the Company believes are the most critical to aid in fully understanding and evaluating its reported financial results are revenue recognition; capitalization of research and development (“R&D”) assets; allowance for doubtful accounts; allowance for product warranty; valuation of stock options; valuation and impairment of goodwill and acquired intangible assets; valuation adjustments for excess and obsolete inventory; deferred taxes and valuation allowances on deferred tax assets; and evaluation and measurement of contingencies. Those estimates could change, and as a result, actual results could differ materially from those estimates. Significant Accounting Policies Cash and Cash Equivalents The Company considers all highly liquid investments with an original or remaining maturity of three months or less at the time of purchase to be cash equivalents. Cash equivalents are stated at cost, which approximates fair value. The Company’s cash and cash equivalents are maintained primarily in demand deposit accounts with large financial institutions, institutional money market funds, U.S. treasury securities, and corporate notes and bonds. The Company monitors the creditworthiness of the financial institutions, institutional money market funds, and corporations in which the Company invests its surplus funds. The Company has experienced no credit losses from its cash investments. Allowances for Doubtful Accounts The Company records a provision for doubtful accounts based on historical experience and a detailed assessment of the collectability of its accounts receivable. In estimating the allowance for doubtful accounts, the Company considers, among other factors, the aging of the accounts receivable, its historical write-offs, the credit worthiness of each customer, and general economic conditions. Account balances are charged off against the allowance when the Company believes that it is probable that the receivable will not be recovered. Actual write-offs may be in excess of the Company’s estimated allowance. Short-Term and Long-Term Investments The Company’s short-term and long-term investments consist primarily of investment-grade debt securities, all of which are classified as available-for-sale. Available-for-sale securities are carried at fair value. Amortization or accretion of premium or discount is included in other income (expense) on the Consolidated Statements of Operations. Changes in the fair value of available-for-sale securities are reported as a component of accumulated other comprehensive loss within stockholders’ equity on the Consolidated Balance Sheet. Realized gains and losses on the sale of available-for-sale securities are determined by specific identification of the cost basis of each security. Short-term investments mature within 12 months and long-term investments mature in greater than 12 months . Inventories Inventories are stated at the lower of cost (using the first-in, first-out “FIFO” method) or net realizable value. The Company calculates inventory valuation adjustments for excess and obsolete inventory based on current inventory levels, movement, expected useful lives, and estimated future demand of the products and spare parts. Property and Equipment Property and equipment is recorded at cost and reduced by accumulated depreciation. Depreciation expense is recognized over the estimated useful lives of the assets using the straight-line method. Estimated useful lives are three to ten years . Certain equipment used in the development and manufacturing of ceramic components is depreciated over estimated useful lives of up to ten years . Leasehold improvements represent remodeling and retrofitting costs for leased office and manufacturing space and are depreciated over the shorter of either the estimated useful lives or the term of the lease. Software purchased for internal use consists primarily of amounts paid for perpetual licenses to third-party software providers and installation costs. Software is depreciated over the estimated useful lives of three to five years . Tangible assets acquired for R&D activities and have alternative use are capitalized over the useful life of the acquired asset. Estimated useful lives are periodically reviewed, and when appropriate, changes are made prospectively. When certain events or changes in operating conditions occur, asset lives may be adjusted and an impairment assessment may be performed on the recoverability of the carrying amounts. Maintenance and repairs are charged directly to expense as incurred. Goodwill and Other Intangible Assets The purchase price of an acquired company is allocated between intangible assets and the net tangible assets of the acquired business with the residual purchase price recorded as goodwill. The determination of the value of the intangible assets acquired involves certain judgments and estimates. These judgments can include, but are not limited to, the cash flows that an asset is expected to generate in the future and the appropriate weighted average cost of capital. Acquired intangible assets with determinable useful lives are amortized on a straight-line or accelerated basis over the estimated periods benefited, ranging from one to 20 years . Acquired intangible assets with contractual terms are amortized over their respective legal or contractual lives. Customer relationships and other non-contractual intangible assets with determinable lives are amortized over periods ranging from five to 20 years . The Company evaluates the recoverability of long-lived assets by comparing the carrying amount of an asset to estimated future net undiscounted cash flows generated by the asset. If such assets are considered to be impaired, the impairment recognized is measured as the amount by which the carrying amount of the assets exceeds the fair value of the assets. The evaluation of recoverability involves estimates of future operating cash flows based upon certain forecasted assumptions, including, but not limited to, revenue growth rates, gross profit margins, and operating expenses over the expected remaining useful life of the related asset. A shortfall in these estimated operating cash flows could result in an impairment charge in the future. Goodwill is not amortized but is evaluated annually for impairment at the reporting unit level or when indicators of a potential impairment are present. The Company estimates the fair value of the reporting unit using the discounted cash flow and market approaches. Forecast of future cash flows are based on the Company’s best estimate of future net sales and operating expenses, based primarily on expected category expansion, pricing, market segment, and general economic conditions. Fair Value of Financial Instruments The Company’s financial instruments include cash and cash equivalents, restricted cash, investments in marketable securities, accounts receivable, accounts payable, and debt. The carrying amounts for these financial instruments reported in the Consolidated Balance Sheets approximate their fair values. See Note 5 , “ Investments and Fair Value Measurements ,” for further discussion of fair value. Revenue Recognition Revenues are recognized when control of the promised goods or services is transferred to the Company’s customers, in an amount that reflects the consideration the Company expects to be entitled to in exchange for those goods or services. At the inception of each contract, performance obligations are identified and the total transaction price is allocated to the performance obligations. The Company’s payment terms vary based on the credit risk of its customer. For certain customer types, the Company requires payment before the products or services are delivered to the customer. The Company performs an evaluation of customer credit worthiness on an individual contract basis to assess whether collectability is reasonably assured at the inception of the contract. As part of this evaluation, the Company considers many factors about the individual customer, including the underlying financial strength of the customer and/or partnership consortium and the Company’s prior history or industry-specific knowledge about the customer and its supplier relationships. For smaller projects, the Company requires the customer to remit payment generally within 30 to 60 days after product delivery. In some cases, if credit worthiness cannot be determined, prepayment or other security is required. Sales commissions are expensed as incurred when product revenue is earned. These costs are recorded within sales and marketing expenses. Arrangements with Multiple Performance Obligations and Termination for Convenience The Company’s contracts with customers may include multiple performance obligations. For such arrangements, the Company allocates revenue to each performance obligation based on its relative stand-alone selling price. The Company generally determines stand-alone selling prices based on the prices charged to customers. With respect to termination, the Company does not have the ability to cancel the contract for convenience. In general, customers can cancel for convenience upon the payment of a termination fee that covers costs and profit. It is rare for customers to cancel contracts. Practical Expedients and Exemptions In the Water segment, the time period between when the Company transfers control of products to the customer and the payment for the products is, in general, less than one year and, therefore, the practical expedient with respect to a financing component has been adopted by the Company. With respect to taxes, the Company has made the policy election to exclude taxes from the measurement of the transaction price. The Company does not disclose the value of unsatisfied performance obligations for (i) contracts with an original expected length of one year or less and (ii) contracts for which the Company recognizes revenue at the amount to which the Company has the right to invoice for services performed. Contract Costs The Company recognizes the incremental cost of obtaining contracts as an expense when incurred if the amortization period of the assets that the Company otherwise would have recognized is one year or less. The costs of obtaining contracts are included in sales and marketing expenses. Product and Service Revenue Recognition - Water Segment In the Water segment, a contract is established by a written agreement (executed sales order, executed purchase order or stand-alone contract) with the customer with fixed pricing, and a credit risk assessment is completed prior to the signing of the agreement to ensure that collectability is reasonably assured. The Company adheres to consistent pricing in the stand-alone sale of products and services. The Company does not bundle performance obligations in the Water segment. Performance obligations consist of delivery of products, such as the Company’s PX Pressure Exchangers, Turbochargers, pumps, and spare parts, and services. Service obligation, such as commissioning, which are not material, are deferred as contract liabilities until the services are performed. The transfer of control for the Company’s products follows transfer of title which typically occurs upon shipment of the equipment in accordance with International Commercial Terms (commonly referred to as “incoterms”). The specified product performance criteria for the Company’s products pertain to the ability of the Company’s product to meet its published performance specifications and warranty provisions, which the Company’s products have demonstrated on a consistent basis. This factor, combined with historical performance metrics, provides the Company’s management with a reasonable basis to conclude that the products will perform satisfactorily upon commissioning of the plant. Installation is relatively simple, requires no customization, and is performed by the customer under the supervision of the Company’s personnel. Based on these factors, the Company concluded that performance has been completed upon shipment when title transfers based on the shipping terms, and that product revenue is recognized at a point in time. The Company does not provide its customers with a right of product return; however, the Company will accept returns of products that are deemed to be damaged or defective when delivered that are covered by the terms and conditions of the product warranty. Product warranty is provided consistent with the industry and is considered to be an assurance warranty, not a separate performance obligation. Product returns and warranty charges have not been significant. For large projects, stand-alone contracts are utilized. For these contracts, consistent with industry practice, the Company’s customers typically require their suppliers, including the Company, to accept contractual holdback provisions (also referred to as a retention payment) whereby the final amounts due under the sales contract are remitted over extended periods of time or alternatively, stand-by letters of credit are issued. These retention payments are generally 10% or less of the total contract amount and are due and payable upon the passage of time, generally up to 24 to 36 months from the date of product delivery. These retention payments are generally replaced by bank guarantees which have had no history of being exercised, and they align with the product warranty period. The retention payments with no performance conditions are recorded as unbilled trade receivables. Given that they are not material in the context of the contract, they are not considered to be a financing component. Shipping and handling charges billed to customers is a pass-through from the freight forwarder and is included in product revenue. The cost of shipping to customers is included in product cost of revenue. Cost-to-Total Cost (“CTC”) Revenue Recognition - Oil & Gas Segment IsoBoost and IsoGen systems are highly engineered, customized solutions that are designed and manufactured over an extended period of time and are built specifically to meet a customer’s specifications. Given the facts and circumstances of these projects, the Company concluded that the CTC method of accounting is appropriate for IsoBoost and IsoGen systems. In the event that a purchase order for an IsoBoost or IsoGen system does not meet these facts and circumstances, then the CTC method of accounting does not apply. The Company had one CTC contract for IsoBoost turbochargers in fiscal years 2017 through 2018, which was completed in 2018, and last units were shipped in the first quarter of 2019. A standard assurance type warranty was provided. Revenue from fixed price contracts is recognized with progress measured in the ratio of costs incurred to estimated final costs. Contract costs include all direct material and labor costs related to contract performance. Pre-contract costs with no future benefit were expensed in the period in which they were incurred. Since the financial reporting of these contracts depends on estimates, which are assessed continually during the term of the contract, recognized revenues and profit are subject to revisions as the contract progresses to completion. Revisions in profit estimates are reflected in the period in which the facts that give rise to the revisions become known, using the cumulative catchup method. If material, the effects of any changes in estimates are disclosed in the notes to the consolidated financial statements. When estimates indicate that a loss will be incurred on a contract, a provision for the expected loss is recorded in the period in which the loss becomes evident. No loss has been incurred to date. Revenue is recognized only to the extent costs have been recognized in the same period. Unbilled project costs, and cost and estimated earnings in excess of billings, are included in contract assets and contract liabilities, respectively, on the Consolidated Balance Sheets. License and Development Revenue Recognition - Oil & Gas Segment License and development revenue is comprised of revenue recognition over time of the upfront non-refundable $75.0 million exclusivity fee received in connection with the VorTeq License Agreement, as well as the revenue recognition over time of the two milestone payments of $25.0 million each when uncertainty of receipt is resolved and receipt of each milestone payment is considered probable. The VorTeq License Agreement is comprised of a 15 ‑year exclusive license for the Company’s VorTeq technology (“VorTeq”). In performing the obligations under the license, the Company provides research and development services to commercialize the technology in accordance with the Key Performance Indicators (“KPIs”), defined in the VorTeq License Agreement. After commercialization is achieved, payments will be received for the supply and servicing of certain components of the VorTeq. All payments are non-refundable. See Note 14 , “ VorTeq Partnership and License Agreement .” Revenue is recognized when control of the promised goods or services is transferred to customers. Stand-alone selling price was established at the inception of the VorTeq License Agreement by taking the transaction to market on a non-exclusive basis, and pricing in an exclusivity premium. Since the VorTeq License Agreement included an up-front non-refundable payment at the inception of the VorTeq License Agreement and future products and services are provided after initial commercialization, the Company completed an analysis and concluded that there was no material right included in the pricing of the VorTeq License Agreement. Performance obligations, such as the exclusive license to the Missile technology and upgrades prior to and subsequent to the date of full commercial launch, have been identified. Value has been allocated to the performance obligations and revenue is recognized over time based on the input measure of progress of the cost of salaries, wages and travel costs related to the project prior to full commercialization, and ratably for the unspecified upgrades for the period subsequent to full commercialization until the expiration of the VorTeq License Agreement. Once commercial launch is achieved and cartridges are provided under the contract, revenue from those royalty payments will be recognized in accordance with Accounting Standards Codification (“ASC”) 842, Lease Accounting , with the Company as the lessor. It is expected that the cartridge leases will be classified as operating leases, and lease revenue will be recognized as earned. Research and Development (“R&D”) Expense and Capitalization of R&D Assets R&D expense consists of costs incurred for internal projects and for technology licensed to third parties. These costs include the Company’s direct and research-related overhead expenses, which include salaries and other personnel-related expenses (including stock-based compensation), occupancy-related costs, depreciation of facilities, as well as external costs for equipment and supplies. Costs to acquire technologies that are utilized in research and development and that have no alternative future use are expensed when incurred. All R&D costs are expensed as incurred and are included in operating expenses. The costs of materials that are acquired for R&D activities and have no alternative future uses (in R&D projects or otherwise) are expensed as incurred. With respect to tangible assets acquired or constructed for R&D activities, if the costs of materials that are acquired or constructed for a particular R&D project have alternative future uses (in other R&D projects or otherwise), they are capitalized as an asset and the cost of depreciation is charged to expense. Warranty Costs The Company sells products with a limited warranty for a period ranging from 18 months to five years . The Company accrues for warranty costs based on estimated product failure rates, historical activity, and expectations of future costs. Periodically, the Company evaluates and adjusts the warranty costs to the extent that actual warranty costs vary from the original estimates. Stock-based Compensation The Company measures and recognizes stock-based compensation expense based on the fair value measurement for all stock-based awards made to its employees and directors, including restricted stock units (“RSUs”), and employee stock options over the requisite service period (typically the vesting period of the awards). The fair value of RSUs are based on the Company’s stock price on the date of grant. The fair value of stock options is calculated on the date of grant using the Black-Scholes option pricing model, which requires a number of complex assumptions including the expected life to exercise a vested award, expected volatility based upon the Company’s historical stock prices, risk-free interest rate based upon the U.S. Treasury rates, and the Company’s dividend yield. The estimation of awards that will ultimately vest requires judgment, and to the extent that actual results or updated estimates differ from the Company’s current estimates, such amounts are recorded as a cumulative adjustment in the period in which the estimates are revised. See Note 11 , “ Stock-based Compensation ,” for further discussion of stock-based compensation. Foreign Currency The Company’s reporting currency is the U.S. dollar. The functional currency of the Company’s Irish subsidiary is the U.S. dollar, while the functional currency of the Company’s other foreign subsidiaries is their respective local currencies. The asset and liability accounts of the Company’s foreign subsidiaries are translated from their local currencies at the rates in effect on the balance sheet date. Revenue and expenses are translated at average rates of exchange prevailing during the period. Gains and losses resulting from the translation of the Company’s subsidiary balance sheets are recorded as a component of accumulated other comprehensive income (loss). Gains and losses from foreign currency transactions are recorded in other income (expense) in the Consolidated Statements of Operations. Income Taxes Current and non-current tax assets and liabilities are based upon an estimate of taxes refundable or payable for each of the jurisdictions in which the Company is subject to tax. In the ordinary course of business, there is inherent uncertainty in quantifying income tax positions. The Company assesses income tax positions and records tax benefits for all years subject to examination based upon the Company’s evaluation of the facts, circumstances, and information available at the reporting dates. For those tax positions where it is more likely than not that a tax benefit will be sustained, the Company records the largest amount of tax benefit with a greater than 50% likelihood of being realized upon ultimate settlement with a taxing authority that has full knowledge of all relevant information. For those income tax positions where it is not more likely than not that a tax benefit will be sustained, no tax benefit is recognized in the financial statements. When applicable, associated interest and penalties are recognized as a component of income tax expense. Accrued interest and penalties are included within the related tax asset or liability on the Consolidated Balance Sheets. Deferred income taxes are provided for temporary differences arising from differences in bases of assets and liabilities for tax and financial reporting purposes. Deferred income taxes are recorded on temporary differences using enacted tax rates in effect for the year in which the temporary differences are expected to reverse. The effect of a change in tax rates on deferred tax assets and liabilities is recognized in income in the period that includes the enactment date. Deferred tax assets are reduced by a valuation allowance when, in the opinion of management, it is more likely than not that some portion or all of the deferred tax assets will not be realized. Significant judgment is required in determining whether and to what extent any valuation allowance is needed on the Company’s deferred tax assets. In making such a determination, the Company considers all available positive and negative evidence including recent results of operations, scheduled reversals of deferred tax liabilities, projected future income, and available tax planning strategies. See Note 9 , “ Income Taxes ,” for further discussion of tax valuation allowances. The Company’s operations are subject to income and transaction taxes in the U.S. and in foreign jurisdictions. Significant estimates and judgments are required in determining the Company’s worldwide provision for income taxes. Some of these estimates are based on interpretations of existing tax laws or regulations. The ultimate amount of tax liability may be uncertain as a result. Recent Accounting Pronouncements Recently Adopted Accounting Pronouncements In August 2018, the Financial Accounting Standards Board (“FASB”) issued Accounting Standards Update (“ASU”) 2018-15 (“ ASU 2018-15 ”), Intangibles - Goodwill and Other - Internal-Use Software (Topic 350-40): Customer’s Accounting for Implementation Costs Incurred in a Cloud Computing Arrangement That Is a Service Contract . ASU 2018-15 aligns the requirements for capitalizing implementation costs incurred in a hosting arrangement that is a service contract with the requirements for capitalizing implementation costs incurred to develop or obtain internal-use software. The updated guidance is effective for annual periods beginning after December 15, 2019 and interim periods within those fiscal years. Early adoption is permitted. The Company elected to early adopt ASU 2018-15 for the period beginning in the second quarter of 2019 , applying the guidance under ASU 2018-15 prospectively. During the year ended December 31, 2019 , the Company deferred related implementation costs of $1.0 million . Prior Year Adopted Pronouncements In May 2014, the FASB issued ASU No. 2014-09 (“ASU 2014-09”), Revenue from Contracts with Customers (Topic 606) , referred to as Accounting Standards Codification (“ASC”) 606 (“ASC 606”) or the “New Revenue Standard.” ASC 606 supersedes the revenue recognition requirements of ASC 605, Revenue Recognition , and requires entities to recognize revenue when control of promised goods or services is transferred to customers at an amount that reflects the consideration to which the entity expects to be entitled to in exchange for those goods and services. The Company adopted ASC 606 as of January 1, 2018 using the full retrospective transition method. The Company has implemented changes to its current policies and practices, and internal controls over financial reporting to address the requirements of the standard. Amounts presented for the year-ending December 31, 2017 have been restated. In February 2016, the FASB issued ASU No. 2016-02 (“ASU 2016-02”), Leases (Topic 842) : which supersedes ASC 840, Leases (Topic 840) , and provides principles for the recognition, measurement, presentation and disclosure of leases for both lessees and lessors. The Company early adopted ASU 2016-02 on January 1, 2018 concurrent with the Company’s adoption of the New Revenue Standard and elected the available practical expedients. Adoption of the standard required the Company to recast certain previously reported results, including the recognition of additional operating lease right of use assets and liabilities. In November 2016, the FASB issued ASU 2016-18 (“ASU 2016-18”), Statement of Cash Flows (Topic 230): Restricted Cash , also referred to as “New Cash Flow Presentation Standard.” ASU 2016-18 is intended to reduce diversity in practice in the classification and presentation of changes in restricted cash on the Consolidated Statement of Cash Flows. ASU 2016-18 requires that the Consolidated Statement of Cash Flows explain the change in total cash and equivalents and amounts generally described as restricted cash or restricted cash equivalents when reconciling the beginning-of-period and end-of-period total amounts. The Company adopted ASU 2016-18 on January 1, 2018 and has recast its Consolidated Statement of Cash Flow for the year ended December 31, 2017, based on the restricted cash balance on the Company’s Balance Sheet as of December 31, 2017. Impact of Recently Adopted Accounting Pronouncements The following table illustrates changes in the Consolidated Balance Sheets as previously reported prior to, and as adjusted subsequent to, the adoption of the New Revenue Standard and New Lease Standard at January 1, 2018. December 31, 2017 As Previously Reported Adoption of New Revenue Standard Adoption of New Lease Standard As Adjusted (In thousands) Assets Current assets: Contract assets $ 6,411 $ (133 ) $ — $ 6,278 Total current assets 126,196 (133 ) — 126,063 Non-current assets Deferred tax assets, non-current 7,902 31 — 7,933 Operating lease, right of use asset — — 2,843 2,843 Total assets 161,744 (102 ) 2,843 164,485 Liabilities and Stockholders’ Equity Current liabilities: Accrued expenses and other current liabilities 8,517 (469 ) (100 ) 7,948 Lease liabilities — — 1,603 1,603 Contract liabilities 6,416 9,493 — 15,909 Total current liabilities 19,833 9,024 1,503 30,360 Non-current liabilities Lease liabilities, non-current — — 1,698 1,698 Contract liabilities, non-current 59,006 (18,489 ) — 40,517 Other non-current liabilities 358 — (358 ) — Total liabilities 79,213 (9,465 ) 2,843 72,591 Stockholders’ equity: Accumulated deficit (45,922 ) 9,363 — (36,559 ) Total stockholders’ equity 82,531 9,363 — 91,894 Total liabilities and stockholders’ equity 161,744 (102 ) 2,843 164,485 The following table illustrates changes in the Consolidated Statement of Operations as previously reported prior to, and as adjusted subsequent to, the adoption of the New Revenue Standard effective January 1, 2018. Year Ended December 31, 2017 As Previously Reported Adoption of New Revenue Standard As Adjusted (In thousands, except for per share data) Product revenue $ 58,156 $ (133 ) $ 58,023 Product gross profit 39,095 (133 ) 38,962 License and development revenue 5,000 6,106 11,106 Income from operations 3,276 5,973 9,249 Income before income taxes 3,956 5,973 9,929 (Benefit from) provision for income taxes (8,394 ) (31 ) (8,425 ) Net income 12,350 6,004 18,354 Income per share: Basic $ 0.23 $ 0.11 $ 0.34 Diluted $ 0.22 $ 0.11 $ 0.33 Number of shares used in per share calculations: Basic 53,701 — 53,701 Diluted 55,612 — 55,612 The following table illustrates changes in the Company’s segment activities as previously reported prior to, and as adjusted subsequent to, the adoption of the New Revenue Standard effective January 1, 2018. Year Ended December 31, 2017 As Previously Reported Adoption of New R

Revenue

Revenue	12 Months Ended
	Dec. 31, 2019
Revenue from Contract with Customer [Abstract]
Revenue	Revenue Disaggregation of Revenue The following tables present the Company’s revenues disaggregated by geography based on the “shipped to” addresses of the Company’s customers and by major product/service line. Sales and usage-based taxes are excluded from revenues. Year Ended December 31, 2019 Year Ended December 31, 2018 Year Ended December 31, 2017 Water Oil & Gas Total Water Oil & Gas Total Water Oil & Gas Total (In thousands) Primary geographical market Middle East and Africa $ 46,574 $ 104 $ 46,678 $ 35,593 $ 514 $ 36,107 $ 26,190 $ 3,708 $ 29,898 Americas 9,018 14,108 23,126 6,388 13,490 19,878 7,023 11,120 18,143 Asia 11,952 — 11,952 11,955 — 11,955 12,974 — 12,974 Europe 5,186 — 5,186 6,575 — 6,575 8,114 — 8,114 Total $ 72,730 $ 14,212 $ 86,942 $ 60,511 $ 14,004 $ 74,515 $ 54,301 $ 14,828 $ 69,129 Major product/service line PX Pressure Exchangers, pumps and turbo devices $ 72,730 $ 104 $ 72,834 $ 60,511 $ 514 $ 61,025 $ 54,301 $ 3,722 $ 58,023 License and development — 14,108 14,108 — 13,490 13,490 — 11,106 11,106 Total $ 72,730 $ 14,212 $ 86,942 $ 60,511 $ 14,004 $ 74,515 $ 54,301 $ 14,828 $ 69,129 Contract Balances The following table presents contract balances by category. December 31, December 31, (In thousands) Accounts receivable, net $ 12,979 $ 10,212 Contract assets: Contract assets, current $ 501 $ 4,083 Contract assets, non-current 191 — Total contract assets $ 692 $ 4,083 Current contract liabilities: Customer deposits $ 1,506 $ 706 Deferred revenue: Cost and estimated earnings in excess of billings — 264 License and development 13,846 14,518 Product 78 548 Service 316 234 Total current contract liability 15,746 16,270 Non-current contract liabilities, deferred revenue License and development 13,048 26,485 Product 72 54 Total non-current contract liability 13,120 26,539 Total contract liability $ 28,866 $ 42,809 The Company records unbilled receivables as contract assets. The following table presents significant changes in contract assets during the period. December 31, December 31, (In thousands) Contract assets balance, beginning of year $ 4,083 $ 6,278 Transferred to trade receivables (13,155 ) (8,865 ) Additions to contract assets 9,764 6,670 Contract assets balance, end of year $ 692 $ 4,083 The Company records contract liabilities when cash payments are received in advance of the Company’s performance. The following table presents significant changes in contract liabilities during the period. December 31, December 31, (In thousands) Contract liabilities balance, beginning of year $ 42,809 $ 56,426 Revenue recognized (15,247 ) (13,493 ) Increases (decreases) due to cash received, excluding amounts recognized as revenue during the period 1,304 (124 ) Contract liabilities balance, end of year $ 28,866 $ 42,809 The following table presents the estimated revenue expected to be recognized in the future related to performance obligations that are unsatisfied or partially unsatisfied. December 31, (In thousands) Year: 2020 $ 23,514 2021 17,753 2022 661 2023 646 2024 and thereafter 4,385 Total performance obligation $ 46,959

Earnings per Share

Earnings per Share	12 Months Ended
	Dec. 31, 2019
Earnings Per Share [Abstract]
Earnings per Share	Earnings per Share Net income for the reported period is divided by the weighted average number of common shares outstanding during the reported period to calculate basic earnings per common share . Basic earnings per share exclude any dilutive effects of stock options and RSUs. Diluted earnings per common share reflects the potential dilution that would occur if outstanding stock options to purchase common stock were exercised for shares of common stock (using the treasury stock method) and the shares of common stock underlying each outstanding RSU were issued (collectively referred to as “stock awards”). Certain shares of common stock issuable under stock options and RSUs have been omitted from the diluted earnings per share calculations because their inclusion is considered anti-dilutive. The following table presents the computation of basic and diluted earnings per share . Years Ended December 31, 2019 2018 2017 (In thousands, except per share amounts) Numerator: Net income $ 10,913 $ 22,093 $ 18,354 Denominator (weighted average shares): Basic common shares outstanding 54,740 53,764 53,701 Dilutive stock awards 1,327 1,574 1,911 Diluted common shares outstanding 56,067 55,338 55,612 Earnings per share: Basic $ 0.20 $ 0.41 $ 0.34 Diluted $ 0.19 $ 0.40 $ 0.33 The following table presents the potential common shares issuable under stock awards that were excluded from the computation of diluted earnings per share , as their effect would have been anti-dilutive. Years Ended December 31, 2019 2018 2017 (In thousands) Anti-dilutive stock awards 1,898 2,176 1,810

Other Financial Information

Other Financial Information	12 Months Ended
	Dec. 31, 2019
Other Financial Information [Abstract]
Other Financial Information	Other Financial Information Cash, Cash Equivalents and Restricted Cash The Company’s Consolidated Statement of Cash Flows explains the change in the total of cash, cash equivalents and restricted cash. The following table presents a reconciliation of cash, cash equivalents and restricted cash reported within the Consolidated Balance Sheets that sum to the total of such amounts presented. December 31, December 31, (In thousands) Cash and cash equivalents $ 26,387 $ 21,955 Restricted cash, current (included in cash, cash equivalents and restricted cash) — 97 Restricted cash, non-current (included in other assets, non-current) 101 86 Total cash, cash equivalents and restricted cash $ 26,488 $ 22,138 The Company pledged cash in connection with certain stand-by letters of credit and Company credit cards. The Company deposited corresponding amounts into restricted accounts at several financial institutions. Accounts Receivable, net December 31, December 31, (In thousands) Accounts receivable, gross $ 13,287 $ 10,608 Less: Allowance for doubtful accounts (308 ) (396 ) Accounts receivable, net $ 12,979 $ 10,212 Allowance for Doubtful Accounts The following table presents the allowance for doubtful accounts activities. December 31, December 31, December 31, (In thousands) Balance, beginning of year $ 396 $ 103 $ 130 Additions 17 336 55 Changes in estimates (1) (105 ) (43 ) (77 ) Deductions (2) — — (5 ) Balance, end of year $ 308 $ 396 $ 103 (1) Collections of previously reserved accounts (2) Uncollectible accounts written off, net of recoveries Property and Equipment December 31, December 31, (In thousands) Machinery and equipment $ 27,664 $ 23,675 Leasehold improvements 10,485 10,458 Software 3,210 3,013 Office equipment, furniture, and fixtures 3,011 2,970 Automobiles 199 199 Construction in progress 3,910 945 Total property and equipment 48,479 41,260 Less: Accumulated depreciation and amortization (29,636 ) (26,641 ) Property and equipment, net $ 18,843 $ 14,619 Construction in progress costs at December 31, 2019 primarily relates to R&D equipment received and leasehold improvements not placed in service. Construction in progress costs at December 31, 2018 primarily relates to software and system upgrades. Year Ended December 31, 2019 2018 2017 (In thousands) Depreciation and amortization expense $ 3,820 $ 3,228 $ 3,035 Accrued Expenses and Other Current Liabilities December 31, December 31, (In thousands) Payroll and commissions payable $ 6,040 $ 5,843 Accrued warranty reserve 631 478 Other accrued expenses and current liabilities 3,198 2,176 Total accrued expenses and other current liabilities $ 9,869 $ 8,497 Accumulated Other Comprehensive Loss There were no reclassifications of amounts out of accumulated other comprehensive loss for the years ended December 31, 2019 and 2018 , as there have been no sales of securities or translation adjustments that impacted other comprehensive income (loss) during these periods. The tax impact of the changes in accumulated other comprehensive loss for the years ended December 31, 2019 and 2018 was not material. Advertising Expense Advertising expense is charged to operations during the year in which it is incurred. Total advertising expense was not material for the years ended December 31, 2019 , 2018 and 2017 .

Investments and Fair Value Meas

Investments and Fair Value Measurements	12 Months Ended
	Dec. 31, 2019
Investments, Fair Value Disclosure [Abstract]
Investments and Fair Value Measurements	Investments and Fair Value Measurements The following table presents the Company’s cash, cash equivalents, and marketable securities in the form of short-term investments and long-term investments. December 31, December 31, (In thousands) Cash and cash equivalents $ 26,387 $ 21,955 Short-term investments 58,736 73,338 Long-term investments 15,419 1,269 Total cash, cash equivalents and marketable securities $ 100,542 $ 96,562 As of December 31, 2019 and 2018 , there were no available-for-sale investments reported in cash and cash equivalents on the Consolidated Balance Sheets. Available-for-Sale Investments The Company’s short-term and long-term investments are all classified as available-for-sale. As of December 31, 2019 and 2018 , all available-for-sale investments were either classified as short-term with maturities less than 12 months or long-term with maturities over 12 months. The Company generally holds available-for-sale investments until maturity; however, from time-to-time, the Company may elect to sell certain available-for-sale investments prior to maturity. During the year ended December 31, 2019 , sales of available-for-sale investments were $7.6 million . During the year ended December 31, 2018 , there were no sales of available-for-sale investments. The following tables present available-for-sale investments as of December 31, 2019 and 2018 . December 31, 2019 Amortized Gross Gross Fair Value (In thousands) Short-term investments U.S. Treasury securities $ 2,746 $ 1 $ — $ 2,747 Corporate notes and bonds 55,951 49 (11 ) 55,989 Total short-term investments 58,697 50 (11 ) 58,736 Long-term investments Corporate notes and bonds 15,415 9 (5 ) 15,419 Total long-term investments 15,415 9 (5 ) 15,419 Total available-for-sale investments $ 74,112 $ 59 $ (16 ) $ 74,155 December 31, 2018 Amortized Gross Gross Fair Value (In thousands) Short-term investments U.S. treasury securities $ 8,102 $ 1 $ (2 ) $ 8,101 Corporate notes and bonds 65,324 1 (88 ) 65,237 Total short-term investments 73,426 2 (90 ) 73,338 Long-term investments Corporate notes and bonds 1,269 — — 1,269 Total long-term investments 1,269 — — 1,269 Total available-for-sale investments $ 74,695 $ 2 $ (90 ) $ 74,607 The Company monitors investments for other-than-temporary impairment. It was determined that unrealized gains and losses at December 31, 2019 and 2018 , are temporary in nature, because the changes in market value for these securities resulted from fluctuating interest rates, rather than a deterioration of the credit worthiness of the issuers. The Company is unlikely to experience gains or losses if these securities are held to maturity. In the event that the Company disposes of these securities before maturity, it is expected that the realized gains or losses, if any, will be immaterial. Expected maturities can differ from contractual maturities because borrowers may have the right to prepay obligations without prepayment penalties. The following table presents the amortized cost and the related fair value of available-for-sale securities with stated maturities shown by contractual maturity. December 31, 2019 Amortized Cost Fair Value (In thousands) Due in one year or less $ 58,697 $ 58,736 Due in greater than one year 15,415 15,419 Total available-for-sale investments $ 74,112 $ 74,155 Fair Value of Financial Instruments The Company follows the authoritative guidance for fair value measurements and disclosures that, among other things, defines fair value, establishes a consistent framework for measuring fair value, and expands disclosure for each major asset and liability category measured at fair value on either a recurring or nonrecurring basis. Fair value is defined as an exit price that would be received to sell an asset or paid to transfer a liability in an orderly transaction between market participants. As such, fair value is a market-based measurement that should be determined based on assumptions that market participants would use in pricing an asset or liability. Financial assets and liabilities that are remeasured and reported at fair value at each reporting period are classified and disclosed in one of the following three levels: Level 1 — Quoted prices (unadjusted) in active markets for identical assets or liabilities; Level 2 — Inputs other than quoted prices included within Level 1 that are either directly or indirectly observable; and Level 3 — Unobservable inputs in which little or no market activity exists, therefore requiring an entity to develop its own assumptions that market participants would use in pricing. The carrying values of cash and cash equivalents, restricted cash, accounts receivable, un-billed receivables, cost and estimated earnings in excess of billings, accounts payable, and other accrued expenses approximate fair value due to the short-term maturity of those instruments. For the Company’s investments in available-for-sale securities, if quoted prices in active markets for identical investments are not available to determine fair value (Level 1), then the Company uses quoted prices for similar assets or inputs other than quoted prices that are observable either directly or indirectly (Level 2). The investments included in Level 2 consist of corporate notes and bonds and U.S. treasury securities. The following tables present the fair value of financial assets measured on a recurring basis. As of December 31, 2019 and 2018 , the Company had no financial liabilities. December 31, 2019 Total Level 1 Level 2 Level 3 (In thousands) Cash equivalents Money market securities $ 86 $ 86 $ — $ — U.S. treasury securities 11,582 — 11,582 — Total cash equivalents 11,668 86 11,582 — Short-term investments U.S. treasury securities 2,747 — 2,747 — Corporate notes and bonds 55,989 — 55,989 — Total short-term investments 58,736 — 58,736 — Long-term investments Corporate notes and bonds 15,419 — 15,419 — Total long-term investments 15,419 — 15,419 — Total fair value of financial assets $ 85,823 $ 86 $ 85,737 $ — December 31, 2018 Total Level 1 Level 2 Level 3 (In thousands) Cash equivalents Money market securities $ 6,661 $ 6,661 $ — $ — Total cash equivalents 6,661 6,661 — — Short-term investments U.S. treasury securities 8,101 — 8,101 — Corporate notes and bonds 65,237 — 65,237 — Total short-term investments 73,338 — 73,338 — Long-term investments Corporate notes and bonds 1,269 — 1,269 — Total long-term investments 1,269 — 1,269 — Total fair value of financial assets $ 81,268 $ 6,661 $ 74,607 $ — During the years ended December 31, 2019 and 2018 , the Company had no transfers of financial assets between Level 1 and Level 2. The following table presents a summary of the fair value and gross unrealized losses on the available-for-sale securities that have been in a continuous unrealized loss position, aggregated by type of investment instrument as of December 31, 2019 and 2018 . The available-for-sale for investments that were in an unrealized gain position have been excluded from the table. December 31, 2019 December 31, 2018 Fair Value Gross Unrealized Losses Fair Value Gross Unrealized Losses (In thousands) U.S. Treasury securities $ 2,027 $ — $ 8,101 $ (2 ) Corporate notes and bonds 18,754 (16 ) 61,809 (88 ) Total available-for-sale investments with unrealized loss positions $ 20,781 $ (16 ) $ 69,910 $ (90 )

Goodwill and Intangible Assets

Goodwill and Intangible Assets	12 Months Ended
	Dec. 31, 2019
Goodwill and Intangible Assets Disclosure [Abstract]
Goodwill and Intangible Assets	Goodwill and Intangible Assets Goodwill Goodwill resulted from the Company’s acquisition of Pump Engineering, LLC in December 2009 . The net carrying amount of goodwill as of December 31, 2019 and 2018 was $12.8 million . There was no impairment of goodwill recorded during the years ended December 31, 2019 and 2018 . Other Intangible Assets The following table presents the components of active identifiable intangible assets, all of which are finite-lived, at the beginning of each respective year and their related accumulated amortization and carrying value at the end of each respective year. All intangible assets are amortized on a straight-line basis over their useful life. Weighted Average Useful Life December 31, 2019 December 31, 2018 Gross Carrying Amount Accumulated Amortization Net Carrying Amount Gross Carrying Amount Accumulated Amortization Net Carrying Amount (In thousands, except for weighted average useful life) Developed technology 10 years $ 6,100 $ (6,100 ) $ — $ 6,100 $ (5,541 ) $ 559 Patents 18 years 286 (221 ) 65 543 (462 ) 81 Total $ 6,386 $ (6,321 ) $ 65 $ 6,643 $ (6,003 ) $ 640 There were no impairment of intangible assets recorded during the years ended December 31, 2019 , 2018 and 2017 . The following table presents the intangible asset amortization expense recognized during the years ended December 31, 2019 , 2018 and 2017 . Years Ended December 31, 2019 2018 2017 (In thousands) Amortization of intangible assets $ 575 $ 630 $ 631 The following table presents the future estimated amortization expense on intangible assets as of December 31, 2019 . Estimated Future Amortization (In thousands) Year: 2020 $ 16 2021 12 2022 11 2023 11 2024 11 2025 4 Total $ 65

Lines of Credit

Lines of Credit	12 Months Ended
	Dec. 31, 2019
Debt Disclosure [Abstract]
Lines of Credit	Lines of Credit Loan and Pledge Agreement The Company entered into a loan and pledge agreement with a financial institution on January 27, 2017 . Since inception, this loan and pledge agreement has been amended multiple times to accommodate the growth of the Company (the amended loan and pledge agreement is hereinafter referred to as the “ Loan and Pledge Agreement ”). The Loan and Pledge Agreement , as amended, will expire on June 30, 2022 , provides for a committed revolving credit line of $16.0 million and an uncommitted revolving credit line of $4.0 million . The covenants of the Loan and Pledge Agreement allows the Company to incur indebtedness owed to a foreign subsidiary in an aggregate amount not to exceed $66.0 million , which amount is subordinated to any amounts outstanding under the Loan and Pledge Agreement . Revolving Loans Revolving loans under the Loan and Pledge Agreement incur interest per annum at a base rate equal to the London Inter-bank Offered Rate (commonly referred to “LIBOR”) plus 1.5% . Any default bears the aforementioned interest rate plus an additional 2% . The unused portion of the credit line is subject to a fee equal to the product of 0.2% per annum multiplied by the difference, if positive, between $16.0 million and the average daily balance of all advances under the committed facility plus aggregate average daily undrawn amounts of all letters of credit issued under the committed facility during the immediately preceding month or portion thereof. As of December 31, 2019 and 2018 , there were no debt outstanding under the Loan and Pledge Agreement . Letters of Credit Under the Loan and Pledge Agreement , the Company is allowed to borrow and request letters of credit, which are limited to a term of three years , against the eligible assets held from time to time in the pledged account maintained with the financial institution. As of December 31, 2019 and 2018 , there were no letters of credit outstanding under the Loan and Pledge Agreement . Stand-By Letters of Credit Under the Loan and Pledge Agreement , the Company is allowed to issue stand-by letters of credit (“ SBLCs ”) up to one year past the expiration date of the Loan and Pledge Agreement and to hold SBLCs with other financial institutions up to $5.1 million . SBLCs have a term limit of three years , are secured by pledged U.S. investments, and does not have any cash collateral balance requirement. SBLCs are deducted from the total revolving credit line under the Loan and Pledge Agreement , and are subject to a non-refundable quarterly fee that is in an amount equal to 0.7% per annum of the face amount of the outstanding SBLCs . As of December 31, 2019 and 2018 , there were $11.8 million and $8.8 million , respectively, of outstanding SBLCs .

Commitments and Contingencies

Commitments and Contingencies	12 Months Ended
	Dec. 31, 2019
Leases [Abstract]
Commitments and Contingencies	Commitments and Contingencies Operating Lease Obligations The Company leases office facilities and equipment under operating leases that expire on various dates through 2028 . On January 10, 2019 , the Company entered into an industrial lease agreement, which commenced on January 1, 2020 . This new lease for a commercial development center for oil & gas field testing, manufacturing, and training, located in Katy, Texas (the “ Katy Lease ”), includes an office and warehouse space of approximately 25,200 square feet (“sq.ft.”) and land of approximately 4.5 acres. The Company’s annual base rent obligation, paid monthly, will be approximately $0.3 million with an increase of approximately 3% annually thereafter, totaling $3.6 million , over the term of the lease. The initial term of the Katy Lease is 120 months after the commencement date, and the Company has two options to extend the lease by an additional five -year term per option, which must be exercised by written notice at least six months prior to the end of the relevant term. On February 10, 2020 , the Company entered into a lease agreement, that commenced on March 1, 2020 , for an additional office and warehouse space of approximately 54,429 sq.ft., located in Tracy, California (the “ Tracy Lease ”). The new lease will supplement the existing manufacturing, warehouse and distribution of the Company’s energy recovery devices (“ ERDs ”). The Company’s annual base rent obligation, paid monthly, will be approximately $0.4 million , with an increase of approximately 3% annually thereafter, totaling $5.0 million , over the term of the lease. The initial term of the Tracy Lease is 122 months after the commencement date, and the Company has one option to extend the lease by an additional five -year term, which must be exercised by written notice at least nine months prior to the end of the original lease term. The following table presents operating lease expense related to all of the Company’s leased property. Years Ended December 31, 2019 2018 2017 (In thousands) Operating lease cost $ 1,894 $ 1,888 $ 1,699 The following table presents other information related to the operating leases. Years Ended December 31, 2019 2018 2017 (In thousands) Cash payments $ 1,824 $ 964 $ 1,395 The following table presents the weighted average remaining lease term and discount rate related to the operating leases. Years Ended December 31, 2019 2018 Weighted average remaining lease term 8.9 years 9.8 years Weighted average discount rate 6.97 % 6.95 % The following table presents the minimum lease payments under noncancelable operating leases, exclusive of executory costs as of December 31, 2019 . Lease Amounts (1) (In thousands) Year: 2020 $ 1,855 2021 1,653 2022 1,812 2023 1,714 2024 1,922 2025 and thereafter 8,121 Total 17,077 Less imputed lease interest (4,521 ) Total lease liabilities $ 12,556 (1) Excluded from the above table are the aforementioned executed Katy Lease and Tracy Lease . Warranty The following table presents the changes in the Company’s accrued product warranty reserve. Years Ended December 31, 2019 2018 2017 (In thousands) Warranty reserve balance, beginning of year $ 478 $ 366 $ 406 Warranty costs charged to cost of revenue 402 340 246 Utilization charges against reserve (56 ) (48 ) (86 ) Release of accrual related to expired warranties (193 ) (180 ) (200 ) Warranty reserve balance, end of year $ 631 $ 478 $ 366 Purchase Obligations The Company has purchase order arrangements with its vendors for which the Company has not received the related goods or services as of December 31, 2019 . These arrangements are subject to change based on the Company’s sales demand forecasts. The Company has the right to cancel the arrangements prior to the date of delivery. The purchase order arrangements are related to various raw materials and components parts, as well as for capital equipment. As of December 31, 2019 , the Company had approximately $10.4 million of such open cancellable purchase order arrangements. Guarantees The Company enters into indemnification provisions under its agreements with other companies in the ordinary course of business, typically with its customers. Under these provisions, the Company generally indemnifies and holds harmless the indemnified party for losses suffered or incurred by the indemnified party as a result of the Company’s activities, generally limited to personal injury and property damage caused by the Company’s employees at a customer’s plant, and in proportion to the employee’s percentage of fault for the accident. Damages incurred for these indemnifications would be covered by the Company’s general liability insurance to the extent provided by the policy limitations. The Company has not incurred material costs to defend lawsuits or settle claims related to these indemnification agreements. As a result, the estimated valuation of the potential liability arising from these agreements is not material. Accordingly, the Company recorded no liabilities for these agreements as of December 31, 2019 and 2018 . In certain cases, the Company issues warranty and product performance guarantees to its customers for amounts generally equal to 10% or less of the total sales agreement to endorse the execution of product delivery and to the warranty of design work, fabrication and operating performance of our devices. These guarantees are generally SBLCs that typically remain in place for periods of 24 to 36 months . See Note 7 , “ Lines of Credit – Stand-By Letters of Credit ,” for information related to SBLCs. Litigation The Company is named in and subject to various proceedings and claims in connection with its business. The Company is contesting the allegations in these claims, and the Company believes that there are meritorious defenses in each of these matters. The outcome of matters the Company has been, and currently is, involved in cannot be determined at this time, and the results cannot be predicted with certainty. There can be no assurance that these matters will not have a material adverse effect on the Company’s results of operations in any future period and a significant judgment could have a material adverse impact on our financial condition, results of operations and cash flows. The Company may in the future become involved in additional litigation in the ordinary course of its business, including litigation that could be material to its business. The Company considers all claims on a quarterly basis and based on known facts assesses whether potential losses are considered reasonably possible, probable and estimable. Based upon this assessment, the Company then evaluates disclosure requirements and whether to accrue for such claims in its consolidated financial statements. The Company records a provision for a liability when it is both probable that a liability has been incurred and the amount of the loss can be reasonably estimated. These provisions are reviewed at least quarterly and adjusted to reflect the impacts of negotiations, settlements, rulings, advice of legal counsel and other information and events pertaining to a particular case. On September 10, 2014, the Company terminated the employment of its Senior Vice President, Sales, Borja Blanco, on the basis of breach of duty of trust and conduct leading to conflict of interest. On October 24, 2014, Mr. Blanco filed a labor claim against ERI Iberia in Madrid, Spain, challenging the fairness of his dismissal and seeking compensation (“Case 1”). A hearing was held on November 13, 2015, after which the labor court ruled that it did not have jurisdiction over the matter. Mr. Blanco appealed and the appeals court reversed the labor court’s finding and instructed the labor court to make a ruling on the merits on November 21, 2017. On February 14, 2018, the Company received notice that the labor court issued a ruling in favor of Mr. Blanco declaring the termination to be an unjustified dismissal and ordered the Company to pay a dismissed severance. The Company appealed the decision on February 21, 2018 and received notice on March 18, 2019 that the appeals court had partially reversed the labor court’s order. The Company further appealed the decision on March 25, 2019. The Company denies any allegations of wrongdoing and intends to continue to vigorously defend against this lawsuit. Based on currently available information and review with outside counsel, the Company has estimated and accrued a potential loss. On November 24, 2014, Mr. Blanco filed a second action based on breach of contract theories in the same court as Case 1 (“Case 2”), but the cases are separate. In Case 2, Mr. Blanco seeks payment of an unpaid bonus, stock options, and non-compete compensation. The court closed Case 2 in June 2018, and the 1-year period to reinitiate the case elapsed in June 2019.

Income Taxes

Income Taxes	12 Months Ended
	Dec. 31, 2019
Income Tax Disclosure [Abstract]
Income Taxes	Income Taxes The following table presents the Company’s U.S. and foreign components of consolidated income before income taxes and the provision for (benefit from) income taxes . Years Ended December 31, 2019 2018 2017 (1) (In thousands) Income before income taxes: U.S. $ 12,180 $ 12,139 $ 11,549 Foreign 76 (699 ) (1,620 ) Total income before income taxes $ 12,256 $ 11,440 $ 9,929 Current tax provision (benefit): Federal $ (120 ) $ (297 ) $ 441 State 3 (2 ) 12 Foreign 66 25 18 Current tax provision (benefit) (51 ) (274 ) 471 Deferred tax provision (benefit): Federal 949 (9,773 ) (9,025 ) State 445 (606 ) (1,141 ) Foreign — — 1,270 Total deferred tax provision (benefit) 1,394 (10,379 ) (8,896 ) Total provision for (benefit from) income taxes $ 1,343 $ (10,653 ) $ (8,425 ) (1) Due to the full retrospective adoption of ASC 606, the balance for the year ended December 31, 2017 has been recast. For the year ended December 31, 2019 , the Company recognized an income tax expense of $1.3 million , which included a tax benefit of $1.1 million . The tax benefit included a deferred tax benefit of $1.0 million related to an increase in prior year U.S. federal research and development credits and a tax benefit of $0.5 million related to tax deductions from stock-based compensation, partially offset by deferred tax expense of $0.4 million due primarily to a remeasurement of the Company’s state deferred tax assets due to an adjustment to the Company’s estimated blended state effective tax rate. For the year ended December 31, 2018 , the Company recognized an income tax benefit of $10.7 million , which included a tax benefit of $13.5 million . The tax benefit primarily included a tax benefit of $12.3 million related to the income tax effects of a tax election related to a change to the Company’s international tax structure in Ireland that was effective in the second quarter of 2018. This resulted in a deferred tax asset related to tax expense recorded on earnings and profits under the U.S. Tax Cut and Jobs Act (“ Tax Act ”) on deferred revenue not yet recognized under U.S. GAAP. In addition, the tax benefit also included a $0.8 million discrete tax benefit related to tax deductions from stock-based compensation. The Company has evaluated the impact of the global intangible low taxed income (“GILTI”) and has concluded that the impact to the Company of the GILTI is immaterial. For the year ended December 31, 2017 , the Company recognized a tax benefit of $8.4 million , which consisted of a net $10.1 million U.S. federal and state deferred tax benefit after taking into consideration a valuation allowance release on all but $1.4 million of the Company’s U.S. federal and state deferred tax assets, less a valuation allowance for the Irish deferred tax assets of $1.3 million less U.S. federal, state and foreign current tax expense of $0.4 million . In addition, as a result of enactment of the legislation, during the fourth quarter of 2017, the Company incurred a one-time income tax expense of $7.0 million related to the deemed repatriation tax on accumulated foreign earnings (of which $0.3 million is a cash charge and the remaining $6.7 million represents a non-cash discrete tax expense largely from the utilization of net operating loss carryovers). The Company also incurred a non-cash income tax expense of $2.5 million related to the re-measurement of certain deferred tax assets and liabilities based on the tax rates from the Tax Act . For more details on the impact of tax credits and other factors that impact the Company’s annual income tax expense, please see the reconciliation of the statutory federal income tax rate to the effective tax rate table below. The following table presents a reconciliation of income taxes computed at the statutory federal income tax rate to the effective tax rate implied by the accompanying Statements of Operations. Years Ended December 31, 2019 2018 2017 (1) U.S. federal taxes at statutory rate 21 % 21 % 34 % State income tax, net of federal benefit 4 (6 ) 1 Deemed repatriation transition tax — — 71 Deferred tax re-measurement - Change in tax rates — 1 24 Foreign rate differential — (1 ) (10 ) Change in tax status of foreign operations — (102 ) — Stock-based compensation (1 ) (3 ) (6 ) Non-deductible expenses 2 1 1 Federal research credits (16 ) (6 ) (4 ) Valuation allowance — 3 (197 ) Other 1 (1 ) 1 Effective tax rate 11 % (93 %) (85 %) (1) Due to the full retrospective adoption of ASC 606, the tax rate for the year ended December 31, 2017 has been recast. The following table presents the Company’s total deferred tax assets and liabilities. December 31, December 31, (In thousands) Deferred tax assets: Net operating loss carry forwards $ 6,488 $ 5,636 Accruals and reserves 8,922 12,157 Operating lease liabilities 2,750 — Research and development credit carry forwards 7,533 4,609 Acquired intangibles 804 859 Charitable contributions 26 24 Total deferred tax assets 26,523 23,285 Valuation allowance (3,933 ) (2,850 ) Net deferred tax assets 22,590 20,435 Deferred tax liabilities: Depreciation on property and equipment (1,854 ) (937 ) Right of use asset (2,443 ) — Unrecognized gain on translation of foreign currency (33 ) (9 ) Goodwill (1,363 ) (1,171 ) Total deferred tax liabilities (5,693 ) (2,117 ) Net deferred tax asset $ 16,897 $ 18,318 As reported on the balance sheet: Other assets, non-current $ 16,897 $ 18,318 Net deferred tax asset $ 16,897 $ 18,318 The Company had gross deferred tax assets of approximately $26.5 million and $23.3 million at December 31, 2019 and 2018 , respectively. In asserting the recoverability of deferred tax assets, management considers whether it is more likely than not that the assets will be realized. The ultimate realization of deferred tax assets is dependent upon the generation of future taxable income during the periods in which those temporary differences become deductible. The Company assesses the available positive and negative evidence to estimate if sufficient future taxable income will be generated to use the existing deferred tax assets. In making such a determination, the Company considers all available positive and negative evidence, including recent results of operations, scheduled reversals of deferred tax liabilities, projected future income, and available tax planning strategies. A significant piece of objective positive evidence evaluated was the cumulative profit incurred in the U.S. and the cumulative losses incurred in Ireland over the three-year period ended December 31, 2019 . On the basis of this evaluation, as of December 31, 2019 , the Company recognized all of its U.S. federal and state deferred tax assets with the exception that the Company continues to maintain a valuation allowance on its California R&D credit carryovers of approximately $2.8 million . The Company will maintain a valuation allowance on its California R&D credit carryovers because it is more likely than not that the Company will continue to annually generate more California R&D tax credits than it utilizes, resulting in no net reduction of credits. The Company’s policy with respect to California R&D credits is that they are utilized on a last-in, first-out basis. In addition, as of December 31, 2019 , the Company is reporting a full valuation allowance on its Irish entity’s deferred tax assets totaling $1.2 million . The valuation allowance represents a provision for uncertainty as to the realization of tax benefits from these deferred income tax assets. The Company will continue to evaluate the tax benefit uncertainty and will adjust, if warranted, the valuation allowance in future periods to the extent that the Company’s deferred income tax assets become more likely than not to be realizable. The Company continues to assert that the accumulated foreign earnings of its subsidiaries in Spain and Canada are permanently reinvested. Due to the Tax Act, any future repatriation of the earnings of its subsidiaries in Spain and Canada would not be subject to U.S. federal income tax. The Company has estimated that the foreign withholding taxes and U.S. state income taxes related to a potential future repatriation of these earnings would be immaterial. The following table presents the Company’s net operating loss carryforwards by taxing authority. December 31, December 31, (In thousands) Federal $ 21,153 $ 16,838 California 11,840 12,681 Ireland 9,363 9,363 Total net operating loss carryforwards $ 42,356 $ 38,882 The net operating loss carryforwards, if not utilized, will begin to expire in years 2020 and 2031 for Federal and California, respectively. Utilization of the net operating loss carryforward may be subject to a substantial annual limitation due to the ownership change limitations provided by the U.S. Internal Revenue Code (“IRC”) and similar California provisions. The annual limitation will result in the expiration of the net operating loss carryforwards before utilization. The Company has estimated the amount which may ultimately be realized and recorded deferred tax assets accordingly. The Ireland net operating loss carryforwards do not have an expiration date . The following table presents the Company’s R&D credit by taxing authority, minimum tax credit and foreign tax credit carryforwards. December 31, December 31, (In thousands) Federal $ 4,761 $ 2,925 California 3,509 2,132 Total credit carryforwards $ 8,270 $ 5,057 The federal R&D credit carryforwards, if not utilized, will start to expire in year 2030 . The foreign tax credit carryforwards will begin to expire in year 2026 . The federal minimum tax credit carryforward will be refunded, if not utilized, no later than year 2021 . The California credit carryforwards do not expire. Utilization of the credit carryforwards may be subject to a substantial annual limitation due to the ownership change limitations provided by the IRC and similar California provisions. Accounting for uncertain tax positions is based on judgment regarding the largest amount that is greater than 50% likely of being realized upon the ultimate settlement with a taxing authority. The following table presents the aggregate changes in the balance of the gross unrecognized tax benefits. December 31, December 31, December 31, (In thousands) Gross unrecognized tax benefits, beginning of year $ 1,162 $ 911 $ 603 Additions: Prior year tax position 27 — 117 Current year tax position 163 251 191 Reductions: Prior year tax position (389 ) — — Gross unrecognized tax benefits, end of year $ 963 $ 1,162 $ 911 As of December 31, 2019 , the Company had unrecognized tax benefits of $1.0 million , of which $0.5 million , if recognized, would affect the Company’s effective tax rate. The Company adopted the accounting policy that interest and penalties are classified as part of its income taxes. As of December 31, 2019 , there were no accrued interest or penalties associated with any unrecognized tax benefits. There are currently no examinations by Federal, California, and foreign tax authorities. The Company believes that, as of December 31, 2019 , the gross unrecognized tax benefits will not materially change in the next twelve months. The Company believes that it has adequately provided for any reasonably foreseeable outcomes related to any tax audits and that any settlement will not have a material adverse effect on the consolidated financial position or results of operations. However, there can be no assurances as to the possible outcomes.

Stockholders' Equity

Stockholders' Equity	12 Months Ended
	Dec. 31, 2019
Stockholders' Equity Note [Abstract]
Stockholders' Equity	Stockholder’s Equity Preferred Stock The Company has the authority to issue 10,000,000 shares of preferred stock with a par value of $0.001 per share. The Board of Directors has the authority, without action by the Company’s stockholders, to designate and issue shares of preferred stock in one or more series. The Board of Directors is also authorized to designate the rights, preferences, and voting powers of each series of preferred stock, any or all of which may be greater than the rights of the common stock including restrictions of dividends on the common stock, dilution of the voting power of the common stock, reduction of the liquidation rights of the common stock, and delaying or preventing a change in control of the Company without further action by the Company’s stockholders. To date, the Board of Directors has not designated any rights, preferences, or powers of any preferred stock, and as of December 31, 2019 and 2018 , no shares of preferred stock were issued or outstanding. Common Stock The Company has the authority to issue 200,000,000 shares of common stock with a par value of $0.001 per share. Subject to the preferred rights of the holders of shares of any class or series of preferred stock as provided by the Board of Directors with respect to any such class or series of preferred stock, the holders of the common stock shall be entitled to receive dividends, as and when declared by the Board of Directors. In the event of any liquidation, dissolution, or winding up of the Company, whether voluntary or involuntary, after the distribution or payment to the holders of shares of any class or series of preferred stock as provided by the Board of Directors with respect to any such class or series of preferred stock, the remaining assets of the Company available for distribution to stockholders shall be distributed among and paid to the holders of common stock ratably in proportion to the number of shares common stock held by them. The follow table presents the Company’s common shares issued and outstanding as of December 31, 2019 and 2018 . December 31, December 31, Issued 60,717,702 59,396,020 Outstanding 55,261,767 53,940,085 Stock Repurchase Program On March 7, 2018 , the Board of Directors authorized a stock repurchase program under which the Company, at the discretion of management, may repurchase up to $10.0 million in aggregate cost of the Company’s outstanding common stock (the “ March 2018 Authorization ”). Under the March 2018 Authorization , purchases of shares of common stock may be made through September 30, 2018, from time to time in the open market, or in privately negotiated transactions, in compliance with applicable state and federal securities laws. The timing and amounts of any purchases will be based on market conditions and other factors including price, regulatory requirements, and capital availability. The March 2018 Authorization does not obligate the Company to acquire any specific number of shares in any period, and may be expanded, extended, modified or discontinued at any time without prior notice. Under the March 2018 Authorization , as of September 30, 2018, the Company repurchased 1,193,102 shares at an aggregate cost of $10.0 million

Stock-based Compensation

Stock-based Compensation	12 Months Ended
	Dec. 31, 2019
Share-based Payment Arrangement [Abstract]
Stock-based Compensation	Stock-based Compensation Stock Option Plans In June 2016, the stockholders approved the 2016 Incentive Plan (the “ 2016 Plan ”), that permits the grant of stock options, stock appreciation rights (“SARs”), restricted stock (“RS”), restricted stock awards (RSAs”), or RSUs, performance units, performance shares, and other stock-based awards to employees, officers, directors, and consultants. Prior to the approval of the 2016 Plan , the Company maintained the Amended and Restated 2008 Equity Incentive Plan (the “ 2008 Plan ”). Subject to adjustments, as provided in the 2016 Plan , the number of shares of common stock initially authorized for issuance under the 2016 Plan was 4,441,083 shares (which consist of 3,830,000 new share awards plus 611,083 share awards that were authorized and unissued under the 2008 Plan) plus up to 7,635,410 shares that were set aside for awards granted under the 2008 Plan that are subsequently forfeited. The 2016 Plan supersedes all previously issued stock incentive plans (including the 2008 Plan ) and is currently the only available plan from which awards may be granted. Shares available for grant under the 2016 Plan were 2,250,197 shares and 2,603,183 shares at December 31, 2019 and 2018 , respectively. Stock Options Stock options granted under the 2016 Plan and the 2008 Plan , generally vest over 4 years and expire no more than 10 years after the date of grant. Restricted Stock Awards There were no RSAs outstanding as of December 31, 2019 . Restricted Stock Units RSUs awarded in fiscal year 2016 vest 25% on the first anniversary of the grant date and 1/48 th monthly thereafter dependent upon continued employment. RSUs awarded in fiscal year 2017 and thereafter generally vest 25% annually over the 4 years from date of grant and are dependent upon continued employment. As RSUs vest, the units will be settled in shares of common stock based on a one -to-one ratio. The units were valued based on the market price on the date of grant. Fair Value Assumptions Stock Options The fair value of stock options granted to employees is based on the Black-Scholes option pricing model. To determine the inputs for the Black-Scholes option pricing model, the Company is required to develop several assumptions, which are highly subjective. The Company determines these assumptions as follows: Expected Term: The Company uses its historical data to determine the expected term of options based on historical exercise data. As there was no historical exercise data for non-employee directors, the Company determines the expected term based on the simplified method. Expected Volatility: The Company determines expected volatility based on its historical data and the corresponding expected term that was determined using the Company’s historical exercise data. Risk-Free Interest Rate: The risk-free rate is based on U.S. Treasury issues with remaining terms similar to the expected term on the stock options granted. Dividend Yield: The Company has never declared or paid any cash dividends and does not plan to pay cash dividends in the foreseeable future; therefore, the Company uses an expected dividend yield of zero in the valuation model. The following table presents assumptions used in the Black-Scholes option pricing model to determine the estimated grant date fair values of stock options granted to employees. For years ended December 31, 2019 2018 2017 Weighted average expected life (years) 4.58 4.19 4.50 Weighted average expected volatility 75.9% 67.4% 80.2% Risk-free interest rate 1.55% – 2.57% 2.48% – 3.01% 1.64% – 1.99% Weighted average dividend yield —% —% —% Restricted Stock Units The fair value of RSUs granted to employees is based on the Company’s common stock price on the date of grant. Stock-based Compensation Expense The following table presents the stock-based compensation expense related to the fair value measurement of awards granted to employees by expense category and by type of award. All stock-based payment awards are amortized on a straight-line basis over the requisite service periods of the awards, generally the vesting periods. Years Ended December 31, 2019 2018 2017 (In thousands) Stock-based compensation expense charged to: Product cost of revenue $ 130 $ 87 $ 158 General and administrative (1) 3,090 3,266 2,218 Sales and marketing 836 694 821 Research and development 1,625 1,193 890 Total stock-based compensation expense $ 5,681 $ 5,240 $ 4,087 Stock-based compensation expense by type of award: Options (1) $ 3,940 $ 3,873 $ 3,331 RSUs (1) 1,741 1,367 756 Total stock-based compensation expense $ 5,681 $ 5,240 $ 4,087 (1) Includes modification of equity awards. See “ Modifications of Equity Awards ” below. Forfeitures The Company estimates forfeitures at the time of grant and revises those estimates periodically in subsequent periods if actual forfeitures differ from those estimates. The Company uses historical data to estimate pre-vesting option forfeitures and records stock-based compensation expense only for those awards that are expected to vest. If the Company’s actual forfeiture rate is materially different from its estimate, the stock-based compensation expense could be significantly different from what the Company has recorded in the current period. The following table presents the estimated forfeiture rates used in determining the expense in the stock-based compensation expense table above. For years ended December 31, 2019 2018 2017 Stock options and RSUs vested over 4-years 11.6% 14.9% 16.3% Unamortized Stock-Based Compensation Costs Stock-based compensation costs related to unvested stock options and RSUs will generally be amortized on a straight-line basis over the remaining average service period of each award. The following table presents the unamortized compensation costs and weighted average service period of all unvested outstanding awards as of December 31, 2019 . Unamortized Compensation Costs Weighted Average Service Period (In thousands) (In years) Stock options $ 4,031 2.3 RSUs 2,952 2.7 Total unamortized compensation costs, net of adjusted forfeitures $ 6,983 Modifications of Equity Awards During the year ended December 31, 2019 , the Company recorded additional stock-based compensation expense of $0.6 million related to the modification of certain equity awards resulting from the Company’s former Chairman of the Board’s retirement from service, on June 13, 2019 , in consideration for his entering into a Settlement Agreement and Release, and the Company’s former President and Chief Executive Officer’s resignation, on November 1, 2019 , in consideration for his entering into a Settlement Agreement and Release. During the year ended December 31, 2018 , the Company recorded additional stock-based compensation expense of $0.9 million primarily related to the modification of certain equity awards resulting from the Company’s former President and Chief Executive Officer’s resignation, on February 24, 2018 , in consideration for his entering into a Settlement Agreement and Release. Stock Option Activities The following table presents the stock option activities under the Company’s 2016 Incentive Plan (“2016 Plan”) and Amended and Restated 2008 Equity Incentive Plan. Number Weighted Average Exercise Price Weighted Average Remaining Contractual Life Aggregate Intrinsic Value (1) (In thousands) (Per share) (In years) (In thousands) Balance, December 31, 2016 5,883 $ 4.81 Granted 677 9.57 Exercised (1,226 ) 4.49 $ 6,798 Forfeited (242 ) 6.60 Balance, December 31, 2017 5,092 5.43 Granted 1,232 7.96 Exercised (1,160 ) 3.73 4,735 Forfeited (182 ) 3.98 Balance, December 31, 2018 4,982 6.36 Granted 568 8.31 Exercised (1,133 ) 5.36 4,781 Forfeited (490 ) 8.49 Balance, December 31, 2019 3,927 $ 6.66 6.0 $ 12,497 Vested and exercisable as of December 31, 2019 2,866 $ 6.01 5.1 $ 10,955 Vested and exercisable as of December 31, 2019 and expected to vest thereafter 3,807 $ 6.61 5.9 $ 12,303 (1) The aggregate intrinsic value of an exercised option is calculated as the difference between the exercise price of the underlying option and the fair value of the Company’s common stock at the time of exercise. The aggregate intrinsic value at December 31, 2019 is calculated as the difference between the exercise price of the underlying outstanding options and the fair value of the Company’s common stock as of December 31, 2019 or the last trading day prior to December 31, 2019 . Restricted Stock Unit Activities The following table presents the RSU activities under the 2016 Plan and includes the RSUs granted under previous plans. Number Weighted (In thousands) (Per share) Balance, December 31, 2016 214 $ 8.65 Awarded 162 10.14 Vested (91 ) 8.65 Forfeited (11 ) 8.52 Balance, December 31, 2017 274 9.54 Awarded 279 7.74 Vested (90 ) 9.33 Balance, December 31, 2018 463 8.49 Awarded 415 7.80 Vested (201 ) 8.62 Forfeited (133 ) 8.37 Balance, December 31, 2019 544 7.95 Vested Stock Options and RSUs The following table presents the total grant date fair value of stock options and RSUs vested during the period. Years Ended December 31, 2019 2018 2017 (In thousands) Stock options $ 4,025 $ 3,607 $ 3,375 RSUs 1,733 841 783 Total grant date fair value of stock options and RSUs vested during the period $ 5,758 $ 4,448 $ 4,158

Business Segment

Business Segment	12 Months Ended
	Dec. 31, 2019
Segment Reporting [Abstract]
Business Segment	Business Segment Business Segments The Company’s chief operating decision-maker (“CODM”) is the chief executive officer. The Company’s reportable segments consist of the Water segment and the Oil & Gas segment. These segments are based on the industries in which the products are sold, the type of products sold and the related products and services. The Water segment consists of revenue associated with products sold for use in reverse osmosis desalination as well as the related identifiable expenses. The Oil & Gas segment consists of revenue associated with products sold for use in gas processing, chemical processing and hydraulic fracturing as well as license and development revenue associated therewith. Operating income (loss) for each segment excludes other income and expenses and certain corporate expenses managed outside the operating segment such as income taxes and other separately managed general and administrative expenses not related to the identified segments. Assets and liabilities are reviewed at the consolidated level by the CODM and are not accounted for by segment. The CODM allocates resources to and assesses the performance of each operating segment using information about its revenue and operating income (loss) . The following table presents a summary of the Company’s financial information by segment. Year Ended December 31, 2019 Year Ended December 31, 2018 Year Ended December 31, 2017 Water Oil & Gas Total Water Oil & Gas Total Water Oil & Gas Total (In thousands) Product revenue $ 72,730 $ 104 $ 72,834 $ 60,512 $ 513 $ 61,025 $ 54,301 $ 3,722 $ 58,023 Product cost of revenue 20,148 187 20,335 17,211 662 17,873 16,032 3,029 19,061 Product gross profit (loss) 52,582 (83 ) 52,499 43,301 (149 ) 43,152 38,269 693 38,962 License and development revenue — 14,108 14,108 — 13,490 13,490 — 11,106 11,106 Operating expenses General and administrative 1,501 1,576 3,077 2,078 1,771 3,849 1,401 1,565 2,966 Sales and marketing 7,072 741 7,813 5,783 1,264 7,047 5,787 2,228 8,015 Research and development 3,825 19,085 22,910 1,711 15,276 16,987 1,064 12,217 13,281 Amortization of intangibles 575 — 575 629 — 629 631 — 631 Total operating expenses 12,973 21,402 34,375 10,201 18,311 28,512 8,883 16,010 24,893 Operating income (loss) $ 39,609 $ (7,377 ) 32,232 $ 33,100 $ (4,970 ) 28,130 $ 29,386 $ (4,211 ) 25,175 Less: Corporate operating expenses 21,868 18,152 15,926 Income from operations 10,364 9,978 9,249 Other income, net 1,892 1,462 680 Income before income taxes $ 12,256 $ 11,440 $ 9,929 The following table presents depreciation and amortization expense by segment. Years Ended December 31, 2019 2018 2017 (In thousands) Water $ 1,824 $ 2,060 $ 2,723 Oil & Gas 2,251 1,377 448 Corporate 320 432 495 Total depreciation and amortization $ 4,395 $ 3,869 $ 3,666

Concentrations

Concentrations	12 Months Ended
	Dec. 31, 2019
Risks and Uncertainties [Abstract]
Concentrations	Concentrations Product Revenue by Geographic Location The following table presents the Company’s product revenue by geographic locations. The geographic information includes product revenue from our domestic and international customers based on the customers’ requested delivery locations, except for certain cases in which the customer directed the Company to deliver its products to a location that differs from the known ultimate location of use. In such cases, the ultimate location of use rather than the delivery location is reflected in the table. Years Ended December 31, 2019 2018 2017 Product revenue by geographic location: United States 2 % 3 % 3 % International 98 % 97 % 97 % Total product revenue 100 % 100 % 100 % Product revenue by country: (1) Saudi Arabia 29 % 31 % 13 % United Arab Emirates 10 % ** ** Egypt ** 17 % 15 % Others (2) 61 % 52 % 72 % Total 100 % 100 % 100 % (1) Countries representing more than 10% of product revenues for the periods presented. (2) Countries in the aggregate, individually representing less than 10% of product revenues for the periods presented. ** Zero or less than 10%. Product Revenue The following table presents customers accounting for 10% or more of the Company’s product revenue by segment. Years Ended December 31, Segment 2019 2018 2017 Customer A Water 19% ** ** Customer B Water ** 15% ** Customer C Water ** 11% ** ** Zero or less than 10%. License and Development Revenue One international Oil & Gas segment customer accounted for 100% of the Company’s license and development revenue for each of the years ended December 31, 2019 , 2018 and 2017 . Accounts Receivable The following table presents customers accounting for 10% or more of the Company’s combined accounts receivable by segment. Segment December 31, December 31, Customer A Water 30% ** Customer F Oil & Gas ** 26% Customer E Water ** 20% Customer D Water ** 11% ** Zero or less than 10%. Long-lived Assets All of the Company’s long-lived assets were located in the United States at December 31, 2019 and 2018 . Major Supply Vendors The following table presents the major supply vendors accounting for 10% or more of the Company’s consolidated supply and manufacturing costs purchases during the years ended December 31, 2019 and 2018 . Years Ended December 31, 2019 2018 Vendor A 22% 18% Vendor B 13% 10%

VorTeq Partnership and License

VorTeq Partnership and License Agreement	12 Months Ended
	Dec. 31, 2019
Organization, Consolidation and Presentation of Financial Statements [Abstract]
VorTeq Partnership and License Agreement	VorTeq Partnership and License Agreement The Company’s VorTeq technology enables oilfield service hydraulic fracturing operators to isolate their high-pressure hydraulic fracturing pumps from fracturing fluid thereby reducing operating and capital costs. In 2014, the Company entered into a strategic partnership with Liberty Oil Field Services (“Liberty”) to pilot and conduct field trials with the VorTeq. Through this agreement, Liberty has the rights to lease up to twenty VorTeq Missiles (defined below) for a period of up to five years following commercialization. On October 14, 2015, the Company and the VorTeq Licensee entered into the VorTeq License Agreement , which provides the VorTeq Licensee with exclusive worldwide rights to the Company’s VorTeq technology for use in hydraulic fracturing onshore applications. The VorTeq License Agreement provides an exception for Liberty’s contractual rights to utilize the VorTeq. In performing the obligations under the agreement, the Company provides research and development services to commercialize the technology in accordance with the KPIs, defined in the VorTeq License Agreement. After commercialization is achieved, royalty payments will be received for the supply and servicing of cartridges. All payments are non-refundable. The VorTeq is made up of Pressure Exchanger cartridges, housed in a high-pressure manifold (the “Missile”) though which a motive fluid is used to pressurize hydraulic fracturing fluid, which is processed and sent down the well bore. The VorTeq License Agreement includes up to $125.0 million in upfront consideration paid in stages: (i) a $75.0 million non-refundable upfront exclusivity payment; and (ii) two milestone payments of $25.0 million each upon achievement of successful tests in accord with KPIs specified in the VorTeq License Agreement (“Milestone Payment 1 and 2”). Milestone Payment 1 of $25.0 million is payable upon a successful five stage yard test at the VorTeq Licensee’s test facility. The Milestone Payment 2 of $25.0 million is payable upon a successful twenty stage hydraulic fracturing at one of the VorTeq Licensee’s customer’s live wells. The achievement of each milestone and the receipt of each of the related payments are subject to a high degree of uncertainty. After initial commercialization, the VorTeq Licensee will begin paying ongoing recurring royalty fees to the Company for supply and service of the cartridges based on the number of VorTeqs in operation which is subject to the greater of a minimum adoption curve or the adoption rate of the technology. During the period, from initial commercialization to full commercialization, the technology will be deployed commercially; and through continuous improvement and cost refinement, the efficiency and effectiveness of the product will fully stabilize. The exclusive nature of the agreement terminates if the VorTeq Licensee does not meet the specified minimum adoption curves. In the event the Company is not able to achieve full commercialization under the terms of the VorTeq License Agreement , the exclusivity right of the VorTeq Licensee under the VorTeq License Agreement continues throughout the term.

Supplementary Data _ Quarterly

Supplementary Data — Quarterly Financial Data (unaudited)	12 Months Ended
	Dec. 31, 2019
Quarterly Financial Information Disclosure [Abstract]
Supplementary Data — Quarterly Financial Data (unaudited)	Supplementary Data – Quarterly Financial Data (unaudited) The following tables present certain unaudited consolidated quarterly financial information for each of the four fiscal quarters in the periods ended December 31, 2019 and 2018 . This quarterly information has been prepared on the same basis as the audited Consolidated Financial Statements and includes all adjustments, consisting only of normal recurring adjustments, necessary for a fair presentation of the information for the periods presented. The results for these quarterly periods are not necessarily indicative of the operating results for a full year or any future period. 2019 QUARTERLY FINANCIAL DATA (1) (unaudited) Three Months Ended March 31, June 30, September 30, December 31, (In thousands, except per share amounts) Product revenue $ 16,072 $ 19,226 $ 21,752 $ 15,784 Product cost of revenue 4,935 5,483 5,425 4,492 Product gross profit 11,137 13,743 16,327 11,292 License and development revenue 3,723 3,570 3,098 3,717 Operating expenses: General and administrative 5,579 5,500 5,711 6,042 Sales and marketing 2,162 2,181 2,367 2,724 Research and development 4,254 5,480 6,620 7,048 Amortization of intangible assets 156 157 156 106 Total operating expenses 12,151 13,318 14,854 15,920 Income (loss) from operations $ 2,709 $ 3,995 $ 4,571 $ (911 ) Provision for (benefit from) income taxes $ 554 $ 756 $ (83 ) $ 116 Net income (loss) $ 2,654 $ 3,719 $ 5,149 $ (609 ) Earnings (deficit) per share: Basic $ 0.05 $ 0.07 $ 0.09 $ (0.01 ) Diluted $ 0.05 $ 0.07 $ 0.09 $ (0.01 ) (1) Quarterly results may not add up to annual results due to rounding. 2018 QUARTERLY FINANCIAL DATA (1) (unaudited) Three Months Ended March 31, June 30, September 30, December 31, (In thousands, except per share amounts) Product revenue $ 11,058 $ 17,406 $ 18,578 $ 13,983 Product cost of revenue 3,314 5,976 5,022 3,561 Product gross profit 7,744 11,430 13,556 10,422 License and development revenue 2,749 3,358 3,661 3,723 Operating expenses: General and administrative 5,837 4,927 5,266 5,446 Sales and marketing 1,912 1,858 1,873 1,903 Research and development 3,917 3,605 4,270 5,220 Amortization of intangible assets 158 158 158 156 Total operating expenses 11,824 10,548 11,567 12,725 Income (loss) from operations $ (1,331 ) $ 4,240 $ 5,650 $ 1,420 Provision for (benefit from) income taxes (2) $ (357 ) $ (11,122 ) $ 1,339 $ (516 ) Net income (loss) $ (726 ) $ 15,743 $ 4,658 $ 2,421 Earnings (deficit) per share: Basic $ (0.01 ) $ 0.29 $ 0.09 $ 0.04 Diluted $ (0.01 ) $ 0.28 $ 0.08 $ 0.04 (1) Quarterly results may not add up to annual results due to rounding. (2) During second quarter of 2018, the Company recognized an income tax benefit of $11.1 million , which included a $12.1 million discrete tax benefit. This discrete tax benefit includes an $11.9 million

Description of Business and S_2

Description of Business and Significant Accounting Policies (Policies)	12 Months Ended
	Dec. 31, 2019
Accounting Policies [Abstract]
Basis of Presentation	Basis of Presentation The Company’s Consolidated Financial Statements include the accounts of the Company and its wholly-owned subsidiaries. All significant inter-company accounts and transactions have been eliminated in consolidation. Reclassifications The accompanying Consolidated Financial Statements have been prepared by the Company pursuant to the rules and regulations of the Securities and Exchange Commission (“SEC”). Certain prior period amounts have been reclassified in the balance sheet, statement of cash flows and footnotes to conform to the current period presentation.
Use of Estimates	Use of Estimates The preparation of Consolidated Financial Statements, in conformity with the U.S. generally accepted accounting principles (“U.S. GAAP”), requires the Company’s management to make judgments, assumptions and estimates that affect the amounts reported in the Consolidated Financial Statements and accompanying notes. The accounting policies that reflect the Company’s more significant estimates and judgments and that the Company believes are the most critical to aid in fully understanding and evaluating its reported financial results are revenue recognition; capitalization of research and development (“R&D”) assets; allowance for doubtful accounts; allowance for product warranty; valuation of stock options; valuation and impairment of goodwill and acquired intangible assets; valuation adjustments for excess and obsolete inventory; deferred taxes and valuation allowances on deferred tax assets; and evaluation and measurement of contingencies. Those estimates could change, and as a result, actual results could differ materially from those estimates.
Cash and Cash Equivalents	Cash and Cash Equivalents The Company considers all highly liquid investments with an original or remaining maturity of three months or less at the time of purchase to be cash equivalents. Cash equivalents are stated at cost, which approximates fair value. The Company’s cash and cash equivalents are maintained primarily in demand deposit accounts with large financial institutions, institutional money market funds, U.S. treasury securities, and corporate notes and bonds. The Company monitors the creditworthiness of the financial institutions, institutional money market funds, and corporations in which the Company invests its surplus funds. The Company has experienced no credit losses from its cash investments.
Allowances for Doubtful Accounts	Allowances for Doubtful Accounts The Company records a provision for doubtful accounts based on historical experience and a detailed assessment of the collectability of its accounts receivable. In estimating the allowance for doubtful accounts, the Company considers, among other factors, the aging of the accounts receivable, its historical write-offs, the credit worthiness of each customer, and general economic conditions. Account balances are charged off against the allowance when the Company believes that it is probable that the receivable will not be recovered. Actual write-offs may be in excess of the Company’s estimated allowance.
Short-Term and Long-Term Investments	Short-Term and Long-Term Investments The Company’s short-term and long-term investments consist primarily of investment-grade debt securities, all of which are classified as available-for-sale. Available-for-sale securities are carried at fair value. Amortization or accretion of premium or discount is included in other income (expense) on the Consolidated Statements of Operations. Changes in the fair value of available-for-sale securities are reported as a component of accumulated other comprehensive loss within stockholders’ equity on the Consolidated Balance Sheet. Realized gains and losses on the sale of available-for-sale securities are determined by specific identification of the cost basis of each security. Short-term investments mature within 12 months and long-term investments mature in greater than 12 months .
Inventories	Inventories Inventories are stated at the lower of cost (using the first-in, first-out “FIFO” method) or net realizable value. The Company calculates inventory valuation adjustments for excess and obsolete inventory based on current inventory levels, movement, expected useful lives, and estimated future demand of the products and spare parts.
Property and Equipment	Property and Equipment Property and equipment is recorded at cost and reduced by accumulated depreciation. Depreciation expense is recognized over the estimated useful lives of the assets using the straight-line method. Estimated useful lives are three to ten years . Certain equipment used in the development and manufacturing of ceramic components is depreciated over estimated useful lives of up to ten years . Leasehold improvements represent remodeling and retrofitting costs for leased office and manufacturing space and are depreciated over the shorter of either the estimated useful lives or the term of the lease. Software purchased for internal use consists primarily of amounts paid for perpetual licenses to third-party software providers and installation costs. Software is depreciated over the estimated useful lives of three to five years . Tangible assets acquired for R&D activities and have alternative use are capitalized over the useful life of the acquired asset. Estimated useful lives are periodically reviewed, and when appropriate, changes are made prospectively. When certain events or changes in operating conditions occur, asset lives may be adjusted and an impairment assessment may be performed on the recoverability of the carrying amounts. Maintenance and repairs are charged directly to expense as incurred.
Goodwill and Other Intangible Assets	Goodwill and Other Intangible Assets The purchase price of an acquired company is allocated between intangible assets and the net tangible assets of the acquired business with the residual purchase price recorded as goodwill. The determination of the value of the intangible assets acquired involves certain judgments and estimates. These judgments can include, but are not limited to, the cash flows that an asset is expected to generate in the future and the appropriate weighted average cost of capital. Acquired intangible assets with determinable useful lives are amortized on a straight-line or accelerated basis over the estimated periods benefited, ranging from one to 20 years . Acquired intangible assets with contractual terms are amortized over their respective legal or contractual lives. Customer relationships and other non-contractual intangible assets with determinable lives are amortized over periods ranging from five to 20 years . The Company evaluates the recoverability of long-lived assets by comparing the carrying amount of an asset to estimated future net undiscounted cash flows generated by the asset. If such assets are considered to be impaired, the impairment recognized is measured as the amount by which the carrying amount of the assets exceeds the fair value of the assets. The evaluation of recoverability involves estimates of future operating cash flows based upon certain forecasted assumptions, including, but not limited to, revenue growth rates, gross profit margins, and operating expenses over the expected remaining useful life of the related asset. A shortfall in these estimated operating cash flows could result in an impairment charge in the future. Goodwill is not amortized but is evaluated annually for impairment at the reporting unit level or when indicators of a potential impairment are present. The Company estimates the fair value of the reporting unit using the discounted cash flow and market approaches. Forecast of future cash flows are based on the Company’s best estimate of future net sales and operating expenses, based primarily on expected category expansion, pricing, market segment, and general economic conditions.
Fair Value of Financial Instruments	Fair Value of Financial Instruments Fair Value of Financial Instruments The Company follows the authoritative guidance for fair value measurements and disclosures that, among other things, defines fair value, establishes a consistent framework for measuring fair value, and expands disclosure for each major asset and liability category measured at fair value on either a recurring or nonrecurring basis. Fair value is defined as an exit price that would be received to sell an asset or paid to transfer a liability in an orderly transaction between market participants. As such, fair value is a market-based measurement that should be determined based on assumptions that market participants would use in pricing an asset or liability. Financial assets and liabilities that are remeasured and reported at fair value at each reporting period are classified and disclosed in one of the following three levels: Level 1 — Quoted prices (unadjusted) in active markets for identical assets or liabilities; Level 2 — Inputs other than quoted prices included within Level 1 that are either directly or indirectly observable; and Level 3 — Unobservable inputs in which little or no market activity exists, therefore requiring an entity to develop its own assumptions that market participants would use in pricing. The carrying values of cash and cash equivalents, restricted cash, accounts receivable, un-billed receivables, cost and estimated earnings in excess of billings, accounts payable, and other accrued expenses approximate fair value due to the short-term maturity of those instruments. For the Company’s investments in available-for-sale securities, if quoted prices in active markets for identical investments are not available to determine fair value (Level 1), then the Company uses quoted prices for similar assets or inputs other than quoted prices that are observable either directly or indirectly (Level 2). The investments included in Level 2 consist of corporate notes and bonds and U.S. treasury securities.
Revenue Recognition	Revenue Recognition Revenues are recognized when control of the promised goods or services is transferred to the Company’s customers, in an amount that reflects the consideration the Company expects to be entitled to in exchange for those goods or services. At the inception of each contract, performance obligations are identified and the total transaction price is allocated to the performance obligations. The Company’s payment terms vary based on the credit risk of its customer. For certain customer types, the Company requires payment before the products or services are delivered to the customer. The Company performs an evaluation of customer credit worthiness on an individual contract basis to assess whether collectability is reasonably assured at the inception of the contract. As part of this evaluation, the Company considers many factors about the individual customer, including the underlying financial strength of the customer and/or partnership consortium and the Company’s prior history or industry-specific knowledge about the customer and its supplier relationships. For smaller projects, the Company requires the customer to remit payment generally within 30 to 60 days after product delivery. In some cases, if credit worthiness cannot be determined, prepayment or other security is required. Sales commissions are expensed as incurred when product revenue is earned. These costs are recorded within sales and marketing expenses. Arrangements with Multiple Performance Obligations and Termination for Convenience The Company’s contracts with customers may include multiple performance obligations. For such arrangements, the Company allocates revenue to each performance obligation based on its relative stand-alone selling price. The Company generally determines stand-alone selling prices based on the prices charged to customers. With respect to termination, the Company does not have the ability to cancel the contract for convenience. In general, customers can cancel for convenience upon the payment of a termination fee that covers costs and profit. It is rare for customers to cancel contracts. Practical Expedients and Exemptions In the Water segment, the time period between when the Company transfers control of products to the customer and the payment for the products is, in general, less than one year and, therefore, the practical expedient with respect to a financing component has been adopted by the Company. With respect to taxes, the Company has made the policy election to exclude taxes from the measurement of the transaction price. The Company does not disclose the value of unsatisfied performance obligations for (i) contracts with an original expected length of one year or less and (ii) contracts for which the Company recognizes revenue at the amount to which the Company has the right to invoice for services performed. Contract Costs The Company recognizes the incremental cost of obtaining contracts as an expense when incurred if the amortization period of the assets that the Company otherwise would have recognized is one year or less. The costs of obtaining contracts are included in sales and marketing expenses. Product and Service Revenue Recognition - Water Segment In the Water segment, a contract is established by a written agreement (executed sales order, executed purchase order or stand-alone contract) with the customer with fixed pricing, and a credit risk assessment is completed prior to the signing of the agreement to ensure that collectability is reasonably assured. The Company adheres to consistent pricing in the stand-alone sale of products and services. The Company does not bundle performance obligations in the Water segment. Performance obligations consist of delivery of products, such as the Company’s PX Pressure Exchangers, Turbochargers, pumps, and spare parts, and services. Service obligation, such as commissioning, which are not material, are deferred as contract liabilities until the services are performed. The transfer of control for the Company’s products follows transfer of title which typically occurs upon shipment of the equipment in accordance with International Commercial Terms (commonly referred to as “incoterms”). The specified product performance criteria for the Company’s products pertain to the ability of the Company’s product to meet its published performance specifications and warranty provisions, which the Company’s products have demonstrated on a consistent basis. This factor, combined with historical performance metrics, provides the Company’s management with a reasonable basis to conclude that the products will perform satisfactorily upon commissioning of the plant. Installation is relatively simple, requires no customization, and is performed by the customer under the supervision of the Company’s personnel. Based on these factors, the Company concluded that performance has been completed upon shipment when title transfers based on the shipping terms, and that product revenue is recognized at a point in time. The Company does not provide its customers with a right of product return; however, the Company will accept returns of products that are deemed to be damaged or defective when delivered that are covered by the terms and conditions of the product warranty. Product warranty is provided consistent with the industry and is considered to be an assurance warranty, not a separate performance obligation. Product returns and warranty charges have not been significant. For large projects, stand-alone contracts are utilized. For these contracts, consistent with industry practice, the Company’s customers typically require their suppliers, including the Company, to accept contractual holdback provisions (also referred to as a retention payment) whereby the final amounts due under the sales contract are remitted over extended periods of time or alternatively, stand-by letters of credit are issued. These retention payments are generally 10% or less of the total contract amount and are due and payable upon the passage of time, generally up to 24 to 36 months from the date of product delivery. These retention payments are generally replaced by bank guarantees which have had no history of being exercised, and they align with the product warranty period. The retention payments with no performance conditions are recorded as unbilled trade receivables. Given that they are not material in the context of the contract, they are not considered to be a financing component. Shipping and handling charges billed to customers is a pass-through from the freight forwarder and is included in product revenue. The cost of shipping to customers is included in product cost of revenue. Cost-to-Total Cost (“CTC”) Revenue Recognition - Oil & Gas Segment IsoBoost and IsoGen systems are highly engineered, customized solutions that are designed and manufactured over an extended period of time and are built specifically to meet a customer’s specifications. Given the facts and circumstances of these projects, the Company concluded that the CTC method of accounting is appropriate for IsoBoost and IsoGen systems. In the event that a purchase order for an IsoBoost or IsoGen system does not meet these facts and circumstances, then the CTC method of accounting does not apply. The Company had one CTC contract for IsoBoost turbochargers in fiscal years 2017 through 2018, which was completed in 2018, and last units were shipped in the first quarter of 2019. A standard assurance type warranty was provided. Revenue from fixed price contracts is recognized with progress measured in the ratio of costs incurred to estimated final costs. Contract costs include all direct material and labor costs related to contract performance. Pre-contract costs with no future benefit were expensed in the period in which they were incurred. Since the financial reporting of these contracts depends on estimates, which are assessed continually during the term of the contract, recognized revenues and profit are subject to revisions as the contract progresses to completion. Revisions in profit estimates are reflected in the period in which the facts that give rise to the revisions become known, using the cumulative catchup method. If material, the effects of any changes in estimates are disclosed in the notes to the consolidated financial statements. When estimates indicate that a loss will be incurred on a contract, a provision for the expected loss is recorded in the period in which the loss becomes evident. No loss has been incurred to date. Revenue is recognized only to the extent costs have been recognized in the same period. Unbilled project costs, and cost and estimated earnings in excess of billings, are included in contract assets and contract liabilities, respectively, on the Consolidated Balance Sheets. License and Development Revenue Recognition - Oil & Gas Segment License and development revenue is comprised of revenue recognition over time of the upfront non-refundable $75.0 million exclusivity fee received in connection with the VorTeq License Agreement, as well as the revenue recognition over time of the two milestone payments of $25.0 million each when uncertainty of receipt is resolved and receipt of each milestone payment is considered probable. The VorTeq License Agreement is comprised of a 15 ‑year exclusive license for the Company’s VorTeq technology (“VorTeq”). In performing the obligations under the license, the Company provides research and development services to commercialize the technology in accordance with the Key Performance Indicators (“KPIs”), defined in the VorTeq License Agreement. After commercialization is achieved, payments will be received for the supply and servicing of certain components of the VorTeq. All payments are non-refundable. See Note 14 , “ VorTeq Partnership and License Agreement .” Revenue is recognized when control of the promised goods or services is transferred to customers. Stand-alone selling price was established at the inception of the VorTeq License Agreement by taking the transaction to market on a non-exclusive basis, and pricing in an exclusivity premium. Since the VorTeq License Agreement included an up-front non-refundable payment at the inception of the VorTeq License Agreement and future products and services are provided after initial commercialization, the Company completed an analysis and concluded that there was no material right included in the pricing of the VorTeq License Agreement. Performance obligations, such as the exclusive license to the Missile technology and upgrades prior to and subsequent to the date of full commercial launch, have been identified. Value has been allocated to the performance obligations and revenue is recognized over time based on the input measure of progress of the cost of salaries, wages and travel costs related to the project prior to full commercialization, and ratably for the unspecified upgrades for the period subsequent to full commercialization until the expiration of the VorTeq License Agreement. Once commercial launch is achieved and cartridges are provided under the contract, revenue from those royalty payments will be recognized in accordance with Accounting Standards Codification (“ASC”) 842, Lease Accounting , with the Company as the lessor. It is expected that the cartridge leases will be classified as operating leases, and lease revenue will be recognized as earned.
Research and Development Expense	Research and Development (“R&D”) Expense and Capitalization of R&D Assets R&D expense consists of costs incurred for internal projects and for technology licensed to third parties. These costs include the Company’s direct and research-related overhead expenses, which include salaries and other personnel-related expenses (including stock-based compensation), occupancy-related costs, depreciation of facilities, as well as external costs for equipment and supplies. Costs to acquire technologies that are utilized in research and development and that have no alternative future use are expensed when incurred. All R&D costs are expensed as incurred and are included in operating expenses. The costs of materials that are acquired for R&D activities and have no alternative future uses (in R&D projects or otherwise) are expensed as incurred. With respect to tangible assets acquired or constructed for R&D activities, if the costs of materials that are acquired or constructed for a particular R&D project have alternative future uses (in other R&D projects or otherwise), they are capitalized as an asset and the cost of depreciation is charged to expense.
Warranty Costs	Warranty Costs The Company sells products with a limited warranty for a period ranging from 18 months to five years . The Company accrues for warranty costs based on estimated product failure rates, historical activity, and expectations of future costs. Periodically, the Company evaluates and adjusts the warranty costs to the extent that actual warranty costs vary from the original estimates.
Stock-based Compensation	Stock-based Compensation
Foreign Currency	Foreign Currency The Company’s reporting currency is the U.S. dollar. The functional currency of the Company’s Irish subsidiary is the U.S. dollar, while the functional currency of the Company’s other foreign subsidiaries is their respective local currencies. The asset and liability accounts of the Company’s foreign subsidiaries are translated from their local currencies at the rates in effect on the balance sheet date. Revenue and expenses are translated at average rates of exchange prevailing during the period. Gains and losses resulting from the translation of the Company’s subsidiary balance sheets are recorded as a component of accumulated other comprehensive income (loss). Gains and losses from foreign currency transactions are recorded in other income (expense) in the Consolidated Statements of Operations.
Income Taxes	Income Taxes Current and non-current tax assets and liabilities are based upon an estimate of taxes refundable or payable for each of the jurisdictions in which the Company is subject to tax. In the ordinary course of business, there is inherent uncertainty in quantifying income tax positions. The Company assesses income tax positions and records tax benefits for all years subject to examination based upon the Company’s evaluation of the facts, circumstances, and information available at the reporting dates. For those tax positions where it is more likely than not that a tax benefit will be sustained, the Company records the largest amount of tax benefit with a greater than 50% likelihood of being realized upon ultimate settlement with a taxing authority that has full knowledge of all relevant information. For those income tax positions where it is not more likely than not that a tax benefit will be sustained, no tax benefit is recognized in the financial statements. When applicable, associated interest and penalties are recognized as a component of income tax expense. Accrued interest and penalties are included within the related tax asset or liability on the Consolidated Balance Sheets. Deferred income taxes are provided for temporary differences arising from differences in bases of assets and liabilities for tax and financial reporting purposes. Deferred income taxes are recorded on temporary differences using enacted tax rates in effect for the year in which the temporary differences are expected to reverse. The effect of a change in tax rates on deferred tax assets and liabilities is recognized in income in the period that includes the enactment date. Deferred tax assets are reduced by a valuation allowance when, in the opinion of management, it is more likely than not that some portion or all of the deferred tax assets will not be realized. Significant judgment is required in determining whether and to what extent any valuation allowance is needed on the Company’s deferred tax assets. In making such a determination, the Company considers all available positive and negative evidence including recent results of operations, scheduled reversals of deferred tax liabilities, projected future income, and available tax planning strategies. See Note 9 , “ Income Taxes ,” for further discussion of tax valuation allowances. The Company’s operations are subject to income and transaction taxes in the U.S. and in foreign jurisdictions. Significant estimates and judgments are required in determining the Company’s worldwide provision for income taxes. Some of these estimates are based on interpretations of existing tax laws or regulations. The ultimate amount of tax liability may be uncertain as a result.
New Accounting Pronouncements	Recent Accounting Pronouncements Recently Adopted Accounting Pronouncements In August 2018, the Financial Accounting Standards Board (“FASB”) issued Accounting Standards Update (“ASU”) 2018-15 (“ ASU 2018-15 ”), Intangibles - Goodwill and Other - Internal-Use Software (Topic 350-40): Customer’s Accounting for Implementation Costs Incurred in a Cloud Computing Arrangement That Is a Service Contract . ASU 2018-15 aligns the requirements for capitalizing implementation costs incurred in a hosting arrangement that is a service contract with the requirements for capitalizing implementation costs incurred to develop or obtain internal-use software. The updated guidance is effective for annual periods beginning after December 15, 2019 and interim periods within those fiscal years. Early adoption is permitted. The Company elected to early adopt ASU 2018-15 for the period beginning in the second quarter of 2019 , applying the guidance under ASU 2018-15 prospectively. During the year ended December 31, 2019 , the Company deferred related implementation costs of $1.0 million . Prior Year Adopted Pronouncements In May 2014, the FASB issued ASU No. 2014-09 (“ASU 2014-09”), Revenue from Contracts with Customers (Topic 606) , referred to as Accounting Standards Codification (“ASC”) 606 (“ASC 606”) or the “New Revenue Standard.” ASC 606 supersedes the revenue recognition requirements of ASC 605, Revenue Recognition , and requires entities to recognize revenue when control of promised goods or services is transferred to customers at an amount that reflects the consideration to which the entity expects to be entitled to in exchange for those goods and services. The Company adopted ASC 606 as of January 1, 2018 using the full retrospective transition method. The Company has implemented changes to its current policies and practices, and internal controls over financial reporting to address the requirements of the standard. Amounts presented for the year-ending December 31, 2017 have been restated. In February 2016, the FASB issued ASU No. 2016-02 (“ASU 2016-02”), Leases (Topic 842) : which supersedes ASC 840, Leases (Topic 840) , and provides principles for the recognition, measurement, presentation and disclosure of leases for both lessees and lessors. The Company early adopted ASU 2016-02 on January 1, 2018 concurrent with the Company’s adoption of the New Revenue Standard and elected the available practical expedients. Adoption of the standard required the Company to recast certain previously reported results, including the recognition of additional operating lease right of use assets and liabilities. In November 2016, the FASB issued ASU 2016-18 (“ASU 2016-18”), Statement of Cash Flows (Topic 230): Restricted Cash , also referred to as “New Cash Flow Presentation Standard.” ASU 2016-18 is intended to reduce diversity in practice in the classification and presentation of changes in restricted cash on the Consolidated Statement of Cash Flows. ASU 2016-18 requires that the Consolidated Statement of Cash Flows explain the change in total cash and equivalents and amounts generally described as restricted cash or restricted cash equivalents when reconciling the beginning-of-period and end-of-period total amounts. The Company adopted ASU 2016-18 on January 1, 2018 and has recast its Consolidated Statement of Cash Flow for the year ended December 31, 2017, based on the restricted cash balance on the Company’s Balance Sheet as of December 31, 2017.
Advertising Expense	Advertising Expense
Fair Value Assumptions	Restricted Stock Units The fair value of RSUs granted to employees is based on the Company’s common stock price on the date of grant. Fair Value Assumptions Stock Options The fair value of stock options granted to employees is based on the Black-Scholes option pricing model. To determine the inputs for the Black-Scholes option pricing model, the Company is required to develop several assumptions, which are highly subjective. The Company determines these assumptions as follows: Expected Term: The Company uses its historical data to determine the expected term of options based on historical exercise data. As there was no historical exercise data for non-employee directors, the Company determines the expected term based on the simplified method. Expected Volatility: The Company determines expected volatility based on its historical data and the corresponding expected term that was determined using the Company’s historical exercise data. Risk-Free Interest Rate: The risk-free rate is based on U.S. Treasury issues with remaining terms similar to the expected term on the stock options granted. Dividend Yield: The Company has never declared or paid any cash dividends and does not plan to pay cash dividends in the foreseeable future; therefore, the Company uses an expected dividend yield of zero in the valuation model.

Description of Business and S_3

Description of Business and Significant Accounting Policies (Tables)	12 Months Ended
	Dec. 31, 2019
Accounting Policies [Abstract]
Schedule of New Accounting Pronouncements and Changes in Accounting Principles [Table Text Block]	The following table illustrates changes in the Consolidated Balance Sheets as previously reported prior to, and as adjusted subsequent to, the adoption of the New Revenue Standard and New Lease Standard at January 1, 2018. December 31, 2017 As Previously Reported Adoption of New Revenue Standard Adoption of New Lease Standard As Adjusted (In thousands) Assets Current assets: Contract assets $ 6,411 $ (133 ) $ — $ 6,278 Total current assets 126,196 (133 ) — 126,063 Non-current assets Deferred tax assets, non-current 7,902 31 — 7,933 Operating lease, right of use asset — — 2,843 2,843 Total assets 161,744 (102 ) 2,843 164,485 Liabilities and Stockholders’ Equity Current liabilities: Accrued expenses and other current liabilities 8,517 (469 ) (100 ) 7,948 Lease liabilities — — 1,603 1,603 Contract liabilities 6,416 9,493 — 15,909 Total current liabilities 19,833 9,024 1,503 30,360 Non-current liabilities Lease liabilities, non-current — — 1,698 1,698 Contract liabilities, non-current 59,006 (18,489 ) — 40,517 Other non-current liabilities 358 — (358 ) — Total liabilities 79,213 (9,465 ) 2,843 72,591 Stockholders’ equity: Accumulated deficit (45,922 ) 9,363 — (36,559 ) Total stockholders’ equity 82,531 9,363 — 91,894 Total liabilities and stockholders’ equity 161,744 (102 ) 2,843 164,485 The following table illustrates changes in the Consolidated Statement of Operations as previously reported prior to, and as adjusted subsequent to, the adoption of the New Revenue Standard effective January 1, 2018. Year Ended December 31, 2017 As Previously Reported Adoption of New Revenue Standard As Adjusted (In thousands, except for per share data) Product revenue $ 58,156 $ (133 ) $ 58,023 Product gross profit 39,095 (133 ) 38,962 License and development revenue 5,000 6,106 11,106 Income from operations 3,276 5,973 9,249 Income before income taxes 3,956 5,973 9,929 (Benefit from) provision for income taxes (8,394 ) (31 ) (8,425 ) Net income 12,350 6,004 18,354 Income per share: Basic $ 0.23 $ 0.11 $ 0.34 Diluted $ 0.22 $ 0.11 $ 0.33 Number of shares used in per share calculations: Basic 53,701 — 53,701 Diluted 55,612 — 55,612 The following table illustrates changes in the Company’s segment activities as previously reported prior to, and as adjusted subsequent to, the adoption of the New Revenue Standard effective January 1, 2018. Year Ended December 31, 2017 As Previously Reported Adoption of New Revenue Standard As Adjusted (In thousands) Oil & Gas Product revenue $ 3,855 $ (133 ) $ 3,722 Product gross profit 826 (133 ) 693 License and development revenue 5,000 6,106 11,106 Income (loss) from operations (10,184 ) 5,973 (4,211 ) The following table illustrates changes in the Consolidated Statement of Comprehensive Income as previously reported prior to, and as adjusted subsequent to, the adoption of the New Revenue Standard effective January 1, 2018. Year Ended December 31, 2017 As Previously Reported Adoption of New Revenue Standard As Adjusted (In thousands) Net income $ 12,350 $ 6,004 $ 18,354 Comprehensive income 12,343 6,004 18,347 The following tables illustrate changes in the Consolidated Statement of Cash Flows as previously reported prior to, and as adjusted subsequent to, the adoption of the New Revenue Standard and New Cash Flow Presentation effective January 1, 2018. Year Ended December 31, 2017 As Previously Reported Adoption of New Revenue Standard Adoption of New Cash Flow Presentation Standard As Adjusted (In thousands) Net income $ 12,350 $ 6,004 $ — $ 18,354 Changes in operating assets and liabilities: Contract assets (4,396 ) 133 — (4,263 ) Accrued expenses and other liabilities 364 247 — 611 Income taxes 416 (31 ) — 385 Contract liabilities (5,505 ) (6,353 ) — (11,858 ) Net cash used in operating activities 2,895 — — 2,895 Restricted cash 1,538 — (1,538 ) — Net cash used in investing activities (37,373 ) — (1,538 ) (38,911 ) Net change in cash, cash equivalents and restricted cash (33,584 ) — (1,538 ) (35,122 ) Cash, cash equivalents and restricted cash, beginning of year 61,364 — 4,384 65,748 Cash, cash equivalents and restricted cash, end of period 27,780 — 2,846 30,626

Revenue (Tables)

Revenue (Tables)	12 Months Ended
	Dec. 31, 2019
Revenue from Contract with Customer [Abstract]
Disaggregation of Revenue	The following tables present the Company’s revenues disaggregated by geography based on the “shipped to” addresses of the Company’s customers and by major product/service line. Sales and usage-based taxes are excluded from revenues. Year Ended December 31, 2019 Year Ended December 31, 2018 Year Ended December 31, 2017 Water Oil & Gas Total Water Oil & Gas Total Water Oil & Gas Total (In thousands) Primary geographical market Middle East and Africa $ 46,574 $ 104 $ 46,678 $ 35,593 $ 514 $ 36,107 $ 26,190 $ 3,708 $ 29,898 Americas 9,018 14,108 23,126 6,388 13,490 19,878 7,023 11,120 18,143 Asia 11,952 — 11,952 11,955 — 11,955 12,974 — 12,974 Europe 5,186 — 5,186 6,575 — 6,575 8,114 — 8,114 Total $ 72,730 $ 14,212 $ 86,942 $ 60,511 $ 14,004 $ 74,515 $ 54,301 $ 14,828 $ 69,129 Major product/service line PX Pressure Exchangers, pumps and turbo devices $ 72,730 $ 104 $ 72,834 $ 60,511 $ 514 $ 61,025 $ 54,301 $ 3,722 $ 58,023 License and development — 14,108 14,108 — 13,490 13,490 — 11,106 11,106 Total $ 72,730 $ 14,212 $ 86,942 $ 60,511 $ 14,004 $ 74,515 $ 54,301 $ 14,828 $ 69,129
Contract with Customer, Asset and Liability	The following table presents contract balances by category. December 31, December 31, (In thousands) Accounts receivable, net $ 12,979 $ 10,212 Contract assets: Contract assets, current $ 501 $ 4,083 Contract assets, non-current 191 — Total contract assets $ 692 $ 4,083 Current contract liabilities: Customer deposits $ 1,506 $ 706 Deferred revenue: Cost and estimated earnings in excess of billings — 264 License and development 13,846 14,518 Product 78 548 Service 316 234 Total current contract liability 15,746 16,270 Non-current contract liabilities, deferred revenue License and development 13,048 26,485 Product 72 54 Total non-current contract liability 13,120 26,539 Total contract liability $ 28,866 $ 42,809 The Company records unbilled receivables as contract assets. The following table presents significant changes in contract assets during the period. December 31, December 31, (In thousands) Contract assets balance, beginning of year $ 4,083 $ 6,278 Transferred to trade receivables (13,155 ) (8,865 ) Additions to contract assets 9,764 6,670 Contract assets balance, end of year $ 692 $ 4,083 The Company records contract liabilities when cash payments are received in advance of the Company’s performance. The following table presents significant changes in contract liabilities during the period. December 31, December 31, (In thousands) Contract liabilities balance, beginning of year $ 42,809 $ 56,426 Revenue recognized (15,247 ) (13,493 ) Increases (decreases) due to cash received, excluding amounts recognized as revenue during the period 1,304 (124 ) Contract liabilities balance, end of year $ 28,866 $ 42,809
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction	The following table presents the estimated revenue expected to be recognized in the future related to performance obligations that are unsatisfied or partially unsatisfied. December 31, (In thousands) Year: 2020 $ 23,514 2021 17,753 2022 661 2023 646 2024 and thereafter 4,385 Total performance obligation $ 46,959

Earnings per Share (Tables)

Earnings per Share (Tables)	12 Months Ended
	Dec. 31, 2019
Earnings Per Share [Abstract]
Schedule of Earnings Per Share, Basic and Diluted	The following table presents the computation of basic and diluted earnings per share . Years Ended December 31, 2019 2018 2017 (In thousands, except per share amounts) Numerator: Net income $ 10,913 $ 22,093 $ 18,354 Denominator (weighted average shares): Basic common shares outstanding 54,740 53,764 53,701 Dilutive stock awards 1,327 1,574 1,911 Diluted common shares outstanding 56,067 55,338 55,612 Earnings per share: Basic $ 0.20 $ 0.41 $ 0.34 Diluted $ 0.19 $ 0.40 $ 0.33
Schedule of Antidilutive Securities Excluded from Computation of Earnings Per Share	The following table presents the potential common shares issuable under stock awards that were excluded from the computation of diluted earnings per share , as their effect would have been anti-dilutive. Years Ended December 31, 2019 2018 2017 (In thousands) Anti-dilutive stock awards 1,898 2,176 1,810

Other Financial Information (Ta

Other Financial Information (Tables)	12 Months Ended
	Dec. 31, 2019
Other Financial Information [Abstract]
Restrictions on Cash and Cash Equivalents	The Company’s Consolidated Statement of Cash Flows explains the change in the total of cash, cash equivalents and restricted cash. The following table presents a reconciliation of cash, cash equivalents and restricted cash reported within the Consolidated Balance Sheets that sum to the total of such amounts presented. December 31, December 31, (In thousands) Cash and cash equivalents $ 26,387 $ 21,955 Restricted cash, current (included in cash, cash equivalents and restricted cash) — 97 Restricted cash, non-current (included in other assets, non-current) 101 86 Total cash, cash equivalents and restricted cash $ 26,488 $ 22,138
Schedule of Accounts, Notes, Loans and Financing Receivable	Accounts Receivable, net December 31, December 31, (In thousands) Accounts receivable, gross $ 13,287 $ 10,608 Less: Allowance for doubtful accounts (308 ) (396 ) Accounts receivable, net $ 12,979 $ 10,212
Schedule Of Allowance For Doubtful Accounts	The following table presents the allowance for doubtful accounts activities. December 31, December 31, December 31, (In thousands) Balance, beginning of year $ 396 $ 103 $ 130 Additions 17 336 55 Changes in estimates (1) (105 ) (43 ) (77 ) Deductions (2) — — (5 ) Balance, end of year $ 308 $ 396 $ 103 (1) Collections of previously reserved accounts (2) Uncollectible accounts written off, net of recoveries
Schedule of Inventory, Current	Inventories December 31, December 31, (In thousands) Raw materials $ 3,742 $ 2,238 Work in process 2,141 2,689 Finished goods 4,434 2,211 Inventories, net $ 10,317 $ 7,138
Property, Plant and Equipment	Property and Equipment December 31, December 31, (In thousands) Machinery and equipment $ 27,664 $ 23,675 Leasehold improvements 10,485 10,458 Software 3,210 3,013 Office equipment, furniture, and fixtures 3,011 2,970 Automobiles 199 199 Construction in progress 3,910 945 Total property and equipment 48,479 41,260 Less: Accumulated depreciation and amortization (29,636 ) (26,641 ) Property and equipment, net $ 18,843 $ 14,619
Schedule Of Depreciation Expense	Year Ended December 31, 2019 2018 2017 (In thousands) Depreciation and amortization expense $ 3,820 $ 3,228 $ 3,035
Schedule of Accrued Liabilities	Accrued Expenses and Other Current Liabilities December 31, December 31, (In thousands) Payroll and commissions payable $ 6,040 $ 5,843 Accrued warranty reserve 631 478 Other accrued expenses and current liabilities 3,198 2,176 Total accrued expenses and other current liabilities $ 9,869 $ 8,497

Investments and Fair Value Me_2

Investments and Fair Value Measurements (Tables)	12 Months Ended
	Dec. 31, 2019
Investments, Fair Value Disclosure [Abstract]
Cash, Cash Equivalents and Investments	The following table presents the Company’s cash, cash equivalents, and marketable securities in the form of short-term investments and long-term investments. December 31, December 31, (In thousands) Cash and cash equivalents $ 26,387 $ 21,955 Short-term investments 58,736 73,338 Long-term investments 15,419 1,269 Total cash, cash equivalents and marketable securities $ 100,542 $ 96,562
Available-for-sale Securities	The following tables present available-for-sale investments as of December 31, 2019 and 2018 . December 31, 2019 Amortized Gross Gross Fair Value (In thousands) Short-term investments U.S. Treasury securities $ 2,746 $ 1 $ — $ 2,747 Corporate notes and bonds 55,951 49 (11 ) 55,989 Total short-term investments 58,697 50 (11 ) 58,736 Long-term investments Corporate notes and bonds 15,415 9 (5 ) 15,419 Total long-term investments 15,415 9 (5 ) 15,419 Total available-for-sale investments $ 74,112 $ 59 $ (16 ) $ 74,155 December 31, 2018 Amortized Gross Gross Fair Value (In thousands) Short-term investments U.S. treasury securities $ 8,102 $ 1 $ (2 ) $ 8,101 Corporate notes and bonds 65,324 1 (88 ) 65,237 Total short-term investments 73,426 2 (90 ) 73,338 Long-term investments Corporate notes and bonds 1,269 — — 1,269 Total long-term investments 1,269 — — 1,269 Total available-for-sale investments $ 74,695 $ 2 $ (90 ) $ 74,607
Schedule Of Amortized Cost And Fair Value Of Available For Sale Securities	The following table presents the amortized cost and the related fair value of available-for-sale securities with stated maturities shown by contractual maturity. December 31, 2019 Amortized Cost Fair Value (In thousands) Due in one year or less $ 58,697 $ 58,736 Due in greater than one year 15,415 15,419 Total available-for-sale investments $ 74,112 $ 74,155
Schedule of Fair Value, Assets and Liabilities Measured on Recurring Basis	The following tables present the fair value of financial assets measured on a recurring basis. As of December 31, 2019 and 2018 , the Company had no financial liabilities. December 31, 2019 Total Level 1 Level 2 Level 3 (In thousands) Cash equivalents Money market securities $ 86 $ 86 $ — $ — U.S. treasury securities 11,582 — 11,582 — Total cash equivalents 11,668 86 11,582 — Short-term investments U.S. treasury securities 2,747 — 2,747 — Corporate notes and bonds 55,989 — 55,989 — Total short-term investments 58,736 — 58,736 — Long-term investments Corporate notes and bonds 15,419 — 15,419 — Total long-term investments 15,419 — 15,419 — Total fair value of financial assets $ 85,823 $ 86 $ 85,737 $ — December 31, 2018 Total Level 1 Level 2 Level 3 (In thousands) Cash equivalents Money market securities $ 6,661 $ 6,661 $ — $ — Total cash equivalents 6,661 6,661 — — Short-term investments U.S. treasury securities 8,101 — 8,101 — Corporate notes and bonds 65,237 — 65,237 — Total short-term investments 73,338 — 73,338 — Long-term investments Corporate notes and bonds 1,269 — 1,269 — Total long-term investments 1,269 — 1,269 — Total fair value of financial assets $ 81,268 $ 6,661 $ 74,607 $ —
Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value	The available-for-sale for investments that were in an unrealized gain position have been excluded from the table. December 31, 2019 December 31, 2018 Fair Value Gross Unrealized Losses Fair Value Gross Unrealized Losses (In thousands) U.S. Treasury securities $ 2,027 $ — $ 8,101 $ (2 ) Corporate notes and bonds 18,754 (16 ) 61,809 (88 ) Total available-for-sale investments with unrealized loss positions $ 20,781 $ (16 ) $ 69,910 $ (90 )

Goodwill and Intangible Assets

Goodwill and Intangible Assets (Tables)	12 Months Ended
	Dec. 31, 2019
Goodwill and Intangible Assets Disclosure [Abstract]
Schedule of Finite-Lived Intangible Assets	The following table presents the components of active identifiable intangible assets, all of which are finite-lived, at the beginning of each respective year and their related accumulated amortization and carrying value at the end of each respective year. All intangible assets are amortized on a straight-line basis over their useful life. Weighted Average Useful Life December 31, 2019 December 31, 2018 Gross Carrying Amount Accumulated Amortization Net Carrying Amount Gross Carrying Amount Accumulated Amortization Net Carrying Amount (In thousands, except for weighted average useful life) Developed technology 10 years $ 6,100 $ (6,100 ) $ — $ 6,100 $ (5,541 ) $ 559 Patents 18 years 286 (221 ) 65 543 (462 ) 81 Total $ 6,386 $ (6,321 ) $ 65 $ 6,643 $ (6,003 ) $ 640
Finite-lived Intangible Assets Amortization Expense	The following table presents the intangible asset amortization expense recognized during the years ended December 31, 2019 , 2018 and 2017 . Years Ended December 31, 2019 2018 2017 (In thousands) Amortization of intangible assets $ 575 $ 630 $ 631
Schedule of Finite-Lived Intangible Assets, Future Amortization Expense	The following table presents the future estimated amortization expense on intangible assets as of December 31, 2019 . Estimated Future Amortization (In thousands) Year: 2020 $ 16 2021 12 2022 11 2023 11 2024 11 2025 4 Total $ 65

Commitments and Contingencies (

Commitments and Contingencies (Tables)	12 Months Ended
	Dec. 31, 2019
Leases [Abstract]
Lease, Cost	The following table presents operating lease expense related to all of the Company’s leased property. Years Ended December 31, 2019 2018 2017 (In thousands) Operating lease cost $ 1,894 $ 1,888 $ 1,699 The following table presents other information related to the operating leases. Years Ended December 31, 2019 2018 2017 (In thousands) Cash payments $ 1,824 $ 964 $ 1,395
Lease, Term And Discount Rate	The following table presents the weighted average remaining lease term and discount rate related to the operating leases. Years Ended December 31, 2019 2018 Weighted average remaining lease term 8.9 years 9.8 years Weighted average discount rate 6.97 % 6.95 %
Lessee, Operating Lease, Liability, Maturity	Lease Amounts (1) (In thousands) Year: 2020 $ 1,855 2021 1,653 2022 1,812 2023 1,714 2024 1,922 2025 and thereafter 8,121 Total 17,077 Less imputed lease interest (4,521 ) Total lease liabilities $ 12,556 (1) Excluded from the above table are the aforementioned executed Katy Lease and Tracy Lease .
Schedule of Product Warranty Liability	The following table presents the changes in the Company’s accrued product warranty reserve. Years Ended December 31, 2019 2018 2017 (In thousands) Warranty reserve balance, beginning of year $ 478 $ 366 $ 406 Warranty costs charged to cost of revenue 402 340 246 Utilization charges against reserve (56 ) (48 ) (86 ) Release of accrual related to expired warranties (193 ) (180 ) (200 ) Warranty reserve balance, end of year $ 631 $ 478 $ 366

Income Taxes (Tables)

Income Taxes (Tables)	12 Months Ended
	Dec. 31, 2019
Income Tax Disclosure [Abstract]
Schedule of Components of Income Tax Expense (Benefit)	The following table presents the Company’s U.S. and foreign components of consolidated income before income taxes and the provision for (benefit from) income taxes . Years Ended December 31, 2019 2018 2017 (1) (In thousands) Income before income taxes: U.S. $ 12,180 $ 12,139 $ 11,549 Foreign 76 (699 ) (1,620 ) Total income before income taxes $ 12,256 $ 11,440 $ 9,929 Current tax provision (benefit): Federal $ (120 ) $ (297 ) $ 441 State 3 (2 ) 12 Foreign 66 25 18 Current tax provision (benefit) (51 ) (274 ) 471 Deferred tax provision (benefit): Federal 949 (9,773 ) (9,025 ) State 445 (606 ) (1,141 ) Foreign — — 1,270 Total deferred tax provision (benefit) 1,394 (10,379 ) (8,896 ) Total provision for (benefit from) income taxes $ 1,343 $ (10,653 ) $ (8,425 ) (1) Due to the full retrospective adoption of ASC 606, the balance for the year ended December 31, 2017 has been recast.
Schedule of Effective Income Tax Rate Reconciliation	The following table presents a reconciliation of income taxes computed at the statutory federal income tax rate to the effective tax rate implied by the accompanying Statements of Operations. Years Ended December 31, 2019 2018 2017 (1) U.S. federal taxes at statutory rate 21 % 21 % 34 % State income tax, net of federal benefit 4 (6 ) 1 Deemed repatriation transition tax — — 71 Deferred tax re-measurement - Change in tax rates — 1 24 Foreign rate differential — (1 ) (10 ) Change in tax status of foreign operations — (102 ) — Stock-based compensation (1 ) (3 ) (6 ) Non-deductible expenses 2 1 1 Federal research credits (16 ) (6 ) (4 ) Valuation allowance — 3 (197 ) Other 1 (1 ) 1 Effective tax rate 11 % (93 %) (85 %) (1) Due to the full retrospective adoption of ASC 606, the tax rate for the year ended December 31, 2017 has been recast.
Schedule of Deferred Tax Assets and Liabilities	The following table presents the Company’s total deferred tax assets and liabilities. December 31, December 31, (In thousands) Deferred tax assets: Net operating loss carry forwards $ 6,488 $ 5,636 Accruals and reserves 8,922 12,157 Operating lease liabilities 2,750 — Research and development credit carry forwards 7,533 4,609 Acquired intangibles 804 859 Charitable contributions 26 24 Total deferred tax assets 26,523 23,285 Valuation allowance (3,933 ) (2,850 ) Net deferred tax assets 22,590 20,435 Deferred tax liabilities: Depreciation on property and equipment (1,854 ) (937 ) Right of use asset (2,443 ) — Unrecognized gain on translation of foreign currency (33 ) (9 ) Goodwill (1,363 ) (1,171 ) Total deferred tax liabilities (5,693 ) (2,117 ) Net deferred tax asset $ 16,897 $ 18,318 As reported on the balance sheet: Other assets, non-current $ 16,897 $ 18,318 Net deferred tax asset $ 16,897 $ 18,318
Summary of Operating Loss Carryforwards	The following table presents the Company’s net operating loss carryforwards by taxing authority. December 31, December 31, (In thousands) Federal $ 21,153 $ 16,838 California 11,840 12,681 Ireland 9,363 9,363 Total net operating loss carryforwards $ 42,356 $ 38,882
Summary of Tax Credit Carryforwards	The following table presents the Company’s R&D credit by taxing authority, minimum tax credit and foreign tax credit carryforwards. December 31, December 31, (In thousands) Federal $ 4,761 $ 2,925 California 3,509 2,132 Total credit carryforwards $ 8,270 $ 5,057
Schedule of Unrecognized Tax Benefits Roll Forward	The following table presents the aggregate changes in the balance of the gross unrecognized tax benefits. December 31, December 31, December 31, (In thousands) Gross unrecognized tax benefits, beginning of year $ 1,162 $ 911 $ 603 Additions: Prior year tax position 27 — 117 Current year tax position 163 251 191 Reductions: Prior year tax position (389 ) — — Gross unrecognized tax benefits, end of year $ 963 $ 1,162 $ 911

Stockholders' Equity (Tables)

Stockholders' Equity (Tables)	12 Months Ended
	Dec. 31, 2019
Stockholders' Equity Note [Abstract]
Schedule of Stock by Class	The follow table presents the Company’s common shares issued and outstanding as of December 31, 2019 and 2018 . December 31, December 31, Issued 60,717,702 59,396,020 Outstanding 55,261,767 53,940,085

Stock-based Compensation (Table

Stock-based Compensation (Tables)	12 Months Ended
	Dec. 31, 2019
Share-based Payment Arrangement [Abstract]
Schedule of Share-based Payment Award, Stock Options, Valuation Assumptions	The following table presents assumptions used in the Black-Scholes option pricing model to determine the estimated grant date fair values of stock options granted to employees. For years ended December 31, 2019 2018 2017 Weighted average expected life (years) 4.58 4.19 4.50 Weighted average expected volatility 75.9% 67.4% 80.2% Risk-free interest rate 1.55% – 2.57% 2.48% – 3.01% 1.64% – 1.99% Weighted average dividend yield —% —% —%
Schedule of Employee Service Share-based Compensation, Allocation of Recognized Period Costs	The following table presents the stock-based compensation expense related to the fair value measurement of awards granted to employees by expense category and by type of award. All stock-based payment awards are amortized on a straight-line basis over the requisite service periods of the awards, generally the vesting periods. Years Ended December 31, 2019 2018 2017 (In thousands) Stock-based compensation expense charged to: Product cost of revenue $ 130 $ 87 $ 158 General and administrative (1) 3,090 3,266 2,218 Sales and marketing 836 694 821 Research and development 1,625 1,193 890 Total stock-based compensation expense $ 5,681 $ 5,240 $ 4,087 Stock-based compensation expense by type of award: Options (1) $ 3,940 $ 3,873 $ 3,331 RSUs (1) 1,741 1,367 756 Total stock-based compensation expense $ 5,681 $ 5,240 $ 4,087 (1) Includes modification of equity awards. See “ Modifications of Equity Awards ” below.
Schedule Of Forfeiture Rates	The following table presents the estimated forfeiture rates used in determining the expense in the stock-based compensation expense table above. For years ended December 31, 2019 2018 2017 Stock options and RSUs vested over 4-years 11.6% 14.9% 16.3%
Schedule of Unamortized Compensation Cost and Weighted Average Service Period	The following table presents the unamortized compensation costs and weighted average service period of all unvested outstanding awards as of December 31, 2019 . Unamortized Compensation Costs Weighted Average Service Period (In thousands) (In years) Stock options $ 4,031 2.3 RSUs 2,952 2.7 Total unamortized compensation costs, net of adjusted forfeitures $ 6,983
Schedule of Grant Date Fair Value of Equity Instruments Vested	Vested Stock Options and RSUs The following table presents the total grant date fair value of stock options and RSUs vested during the period. Years Ended December 31, 2019 2018 2017 (In thousands) Stock options $ 4,025 $ 3,607 $ 3,375 RSUs 1,733 841 783 Total grant date fair value of stock options and RSUs vested during the period $ 5,758 $ 4,448 $ 4,158
Share-based Compensation, Stock Options, Activity	The following table presents the stock option activities under the Company’s 2016 Incentive Plan (“2016 Plan”) and Amended and Restated 2008 Equity Incentive Plan. Number Weighted Average Exercise Price Weighted Average Remaining Contractual Life Aggregate Intrinsic Value (1) (In thousands) (Per share) (In years) (In thousands) Balance, December 31, 2016 5,883 $ 4.81 Granted 677 9.57 Exercised (1,226 ) 4.49 $ 6,798 Forfeited (242 ) 6.60 Balance, December 31, 2017 5,092 5.43 Granted 1,232 7.96 Exercised (1,160 ) 3.73 4,735 Forfeited (182 ) 3.98 Balance, December 31, 2018 4,982 6.36 Granted 568 8.31 Exercised (1,133 ) 5.36 4,781 Forfeited (490 ) 8.49 Balance, December 31, 2019 3,927 $ 6.66 6.0 $ 12,497 Vested and exercisable as of December 31, 2019 2,866 $ 6.01 5.1 $ 10,955 Vested and exercisable as of December 31, 2019 and expected to vest thereafter 3,807 $ 6.61 5.9 $ 12,303 (1) The aggregate intrinsic value of an exercised option is calculated as the difference between the exercise price of the underlying option and the fair value of the Company’s common stock at the time of exercise. The aggregate intrinsic value at December 31, 2019 is calculated as the difference between the exercise price of the underlying outstanding options and the fair value of the Company’s common stock as of December 31, 2019 or the last trading day prior to December 31, 2019 .
Schedule of Share-based Compensation, Restricted Stock and Restricted Stock Units Activity	The following table presents the RSU activities under the 2016 Plan and includes the RSUs granted under previous plans. Number Weighted (In thousands) (Per share) Balance, December 31, 2016 214 $ 8.65 Awarded 162 10.14 Vested (91 ) 8.65 Forfeited (11 ) 8.52 Balance, December 31, 2017 274 9.54 Awarded 279 7.74 Vested (90 ) 9.33 Balance, December 31, 2018 463 8.49 Awarded 415 7.80 Vested (201 ) 8.62 Forfeited (133 ) 8.37 Balance, December 31, 2019 544 7.95

Business Segment (Tables)

Business Segment (Tables)	12 Months Ended
	Dec. 31, 2019
Segment Reporting [Abstract]
Reconciliation of Operating Profit (Loss) from Segments to Consolidated	The following table presents a summary of the Company’s financial information by segment. Year Ended December 31, 2019 Year Ended December 31, 2018 Year Ended December 31, 2017 Water Oil & Gas Total Water Oil & Gas Total Water Oil & Gas Total (In thousands) Product revenue $ 72,730 $ 104 $ 72,834 $ 60,512 $ 513 $ 61,025 $ 54,301 $ 3,722 $ 58,023 Product cost of revenue 20,148 187 20,335 17,211 662 17,873 16,032 3,029 19,061 Product gross profit (loss) 52,582 (83 ) 52,499 43,301 (149 ) 43,152 38,269 693 38,962 License and development revenue — 14,108 14,108 — 13,490 13,490 — 11,106 11,106 Operating expenses General and administrative 1,501 1,576 3,077 2,078 1,771 3,849 1,401 1,565 2,966 Sales and marketing 7,072 741 7,813 5,783 1,264 7,047 5,787 2,228 8,015 Research and development 3,825 19,085 22,910 1,711 15,276 16,987 1,064 12,217 13,281 Amortization of intangibles 575 — 575 629 — 629 631 — 631 Total operating expenses 12,973 21,402 34,375 10,201 18,311 28,512 8,883 16,010 24,893 Operating income (loss) $ 39,609 $ (7,377 ) 32,232 $ 33,100 $ (4,970 ) 28,130 $ 29,386 $ (4,211 ) 25,175 Less: Corporate operating expenses 21,868 18,152 15,926 Income from operations 10,364 9,978 9,249 Other income, net 1,892 1,462 680 Income before income taxes $ 12,256 $ 11,440 $ 9,929
Schedule of Segment Reporting Information, by Segment	The following table presents depreciation and amortization expense by segment. Years Ended December 31, 2019 2018 2017 (In thousands) Water $ 1,824 $ 2,060 $ 2,723 Oil & Gas 2,251 1,377 448 Corporate 320 432 495 Total depreciation and amortization $ 4,395 $ 3,869 $ 3,666

Concentrations (Tables)

Concentrations (Tables)	12 Months Ended
	Dec. 31, 2019
Concentration Risk [Line Items]
Schedules of Concentration of Risk, by Risk Factor	The following table presents the Company’s product revenue by geographic locations. The geographic information includes product revenue from our domestic and international customers based on the customers’ requested delivery locations, except for certain cases in which the customer directed the Company to deliver its products to a location that differs from the known ultimate location of use. In such cases, the ultimate location of use rather than the delivery location is reflected in the table. Years Ended December 31, 2019 2018 2017 Product revenue by geographic location: United States 2 % 3 % 3 % International 98 % 97 % 97 % Total product revenue 100 % 100 % 100 % Product revenue by country: (1) Saudi Arabia 29 % 31 % 13 % United Arab Emirates 10 % ** ** Egypt ** 17 % 15 % Others (2) 61 % 52 % 72 % Total 100 % 100 % 100 % (1) Countries representing more than 10% of product revenues for the periods presented. (2) Countries in the aggregate, individually representing less than 10% of product revenues for the periods presented. ** Zero or less than 10%.
Product Revenue | Customer Concentration Risk
Concentration Risk [Line Items]
Schedules of Concentration of Risk, by Risk Factor	The following table presents customers accounting for 10% or more of the Company’s product revenue by segment. Years Ended December 31, Segment 2019 2018 2017 Customer A Water 19% ** ** Customer B Water ** 15% ** Customer C Water ** 11% ** ** Zero or less than 10%.
Accounts Receivable | Customer Concentration Risk
Concentration Risk [Line Items]
Schedules of Concentration of Risk, by Risk Factor	The following table presents customers accounting for 10% or more of the Company’s combined accounts receivable by segment. Segment December 31, December 31, Customer A Water 30% ** Customer F Oil & Gas ** 26% Customer E Water ** 20% Customer D Water ** 11% ** Zero or less than 10%.
Major Supply Vendors | Customer Concentration Risk
Concentration Risk [Line Items]
Schedules of Concentration of Risk, by Risk Factor	The following table presents the major supply vendors accounting for 10% or more of the Company’s consolidated supply and manufacturing costs purchases during the years ended December 31, 2019 and 2018 . Years Ended December 31, 2019 2018 Vendor A 22% 18% Vendor B 13% 10%

Supplementary Data _ Quarterl_2

Supplementary Data — Quarterly Financial Data (unaudited) (Tables)	12 Months Ended
	Dec. 31, 2019
Quarterly Financial Information Disclosure [Abstract]
Quarterly Financial Information	2019 QUARTERLY FINANCIAL DATA (1) (unaudited) Three Months Ended March 31, June 30, September 30, December 31, (In thousands, except per share amounts) Product revenue $ 16,072 $ 19,226 $ 21,752 $ 15,784 Product cost of revenue 4,935 5,483 5,425 4,492 Product gross profit 11,137 13,743 16,327 11,292 License and development revenue 3,723 3,570 3,098 3,717 Operating expenses: General and administrative 5,579 5,500 5,711 6,042 Sales and marketing 2,162 2,181 2,367 2,724 Research and development 4,254 5,480 6,620 7,048 Amortization of intangible assets 156 157 156 106 Total operating expenses 12,151 13,318 14,854 15,920 Income (loss) from operations $ 2,709 $ 3,995 $ 4,571 $ (911 ) Provision for (benefit from) income taxes $ 554 $ 756 $ (83 ) $ 116 Net income (loss) $ 2,654 $ 3,719 $ 5,149 $ (609 ) Earnings (deficit) per share: Basic $ 0.05 $ 0.07 $ 0.09 $ (0.01 ) Diluted $ 0.05 $ 0.07 $ 0.09 $ (0.01 ) (1) Quarterly results may not add up to annual results due to rounding. 2018 QUARTERLY FINANCIAL DATA (1) (unaudited) Three Months Ended March 31, June 30, September 30, December 31, (In thousands, except per share amounts) Product revenue $ 11,058 $ 17,406 $ 18,578 $ 13,983 Product cost of revenue 3,314 5,976 5,022 3,561 Product gross profit 7,744 11,430 13,556 10,422 License and development revenue 2,749 3,358 3,661 3,723 Operating expenses: General and administrative 5,837 4,927 5,266 5,446 Sales and marketing 1,912 1,858 1,873 1,903 Research and development 3,917 3,605 4,270 5,220 Amortization of intangible assets 158 158 158 156 Total operating expenses 11,824 10,548 11,567 12,725 Income (loss) from operations $ (1,331 ) $ 4,240 $ 5,650 $ 1,420 Provision for (benefit from) income taxes (2) $ (357 ) $ (11,122 ) $ 1,339 $ (516 ) Net income (loss) $ (726 ) $ 15,743 $ 4,658 $ 2,421 Earnings (deficit) per share: Basic $ (0.01 ) $ 0.29 $ 0.09 $ 0.04 Diluted $ (0.01 ) $ 0.28 $ 0.08 $ 0.04 (1) Quarterly results may not add up to annual results due to rounding. (2) During second quarter of 2018, the Company recognized an income tax benefit of $11.1 million , which included a $12.1 million discrete tax benefit. This discrete tax benefit includes an $11.9 million tax benefit related to the income tax effects of a tax election related to a change to the Company’s international tax structure in Ireland.

Description of Business and S_4

Description of Business and Significant Accounting Policies (Details)	Oct. 14, 2015USD ($)payment	Dec. 31, 2019USD ($)payment
Accounting Policies [Line Items]
Retention payments, percentage		10.00%
Deferred related implementation costs		$ 1,000,000
VorTeq License Agreement
Accounting Policies [Line Items]
Up front non-refundable payment	$ 75,000,000	$ 75,000,000
Number of milestone payments | payment	2	2
License agreement term		15 years
VorTeq License Agreement | Milestone Payment When Uncertainty Of Receipt Is Resolved
Accounting Policies [Line Items]
VorTeq milestone payment to be received		$ 25,000,000
Minimum
Accounting Policies [Line Items]
Property, plant and equipment, useful life		3 years
Weighted average useful life		1 year
Customer payment period after product delivery		30 days
Retention payments, payment period after product delivery		24 months
Product warranty term		18 months
Minimum | Customer Relationships and Other Non-contractual Intangible Assets
Accounting Policies [Line Items]
Weighted average useful life		5 years
Maximum
Accounting Policies [Line Items]
Property, plant and equipment, useful life		10 years
Weighted average useful life		20 years
Customer payment period after product delivery		60 days
Retention payments, payment period after product delivery		36 months
Product warranty term		5 years
Maximum | Customer Relationships and Other Non-contractual Intangible Assets
Accounting Policies [Line Items]
Weighted average useful life		20 years
Equipment Used in Manufacture of Ceramic Components
Accounting Policies [Line Items]
Property, plant and equipment, useful life		10 years
Software | Minimum
Accounting Policies [Line Items]
Property, plant and equipment, useful life		3 years
Software | Maximum
Accounting Policies [Line Items]
Property, plant and equipment, useful life		5 years

Description of Business and S_5

Description of Business and Significant Accounting Policies - Balance Sheet (Details) - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Contract assets	$ 501	$ 4,083	$ 6,278
Total current assets	112,967	119,648	126,063
Deferred tax assets, non-current	16,897	18,318	7,933
Operating lease, right of use asset	11,195	12,189	2,843
Total assets	188,774	179,841	164,485
Accrued expenses and other current liabilities	9,869	8,497	7,948
Lease liabilities	1,023	926	1,603
Contract liabilities	15,746	16,270	15,909
Total current liabilities	27,830	27,132	30,360
Lease liabilities, non-current	11,533	12,556	1,698
Contract liabilities, non-current	13,120	26,539	40,517
Other non-current liabilities	278	236	0
Total liabilities	52,761	66,463	72,591
Accumulated deficit	(3,553)	(14,466)	(36,559)
Total stockholders’ equity	136,013	113,378	91,894
Total liabilities and stockholders’ equity	$ 188,774	$ 179,841	164,485
As Previously Reported
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Contract assets			6,411
Total current assets			126,196
Deferred tax assets, non-current			7,902
Operating lease, right of use asset			0
Total assets			161,744
Accrued expenses and other current liabilities			8,517
Lease liabilities			0
Contract liabilities			6,416
Total current liabilities			19,833
Lease liabilities, non-current			0
Contract liabilities, non-current			59,006
Other non-current liabilities			358
Total liabilities			79,213
Accumulated deficit			(45,922)
Total stockholders’ equity			82,531
Total liabilities and stockholders’ equity			161,744
Restatement Adjustment | Accounting Standards Update 2014-09
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Contract assets			(133)
Total current assets			(133)
Deferred tax assets, non-current			31
Operating lease, right of use asset			0
Total assets			(102)
Accrued expenses and other current liabilities			(469)
Lease liabilities			0
Contract liabilities			9,493
Total current liabilities			9,024
Lease liabilities, non-current			0
Contract liabilities, non-current			(18,489)
Other non-current liabilities			0
Total liabilities			(9,465)
Accumulated deficit			9,363
Total stockholders’ equity			9,363
Total liabilities and stockholders’ equity			(102)
Restatement Adjustment | Accounting Standards Update 2016-02
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Contract assets			0
Total current assets			0
Deferred tax assets, non-current			0
Operating lease, right of use asset			2,843
Total assets			2,843
Accrued expenses and other current liabilities			(100)
Lease liabilities			1,603
Contract liabilities			0
Total current liabilities			1,503
Lease liabilities, non-current			1,698
Contract liabilities, non-current			0
Other non-current liabilities			(358)
Total liabilities			2,843
Accumulated deficit			0
Total stockholders’ equity			0
Total liabilities and stockholders’ equity			$ 2,843

Description of Business and S_6

Description of Business and Significant Accounting Policies - Income Statement (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Income (loss) from operations	$ (911)	$ 4,571	$ 3,995	$ 2,709	$ 1,420	$ 5,650	$ 4,240	$ (1,331)	$ 10,364	$ 9,978	$ 9,249
(Loss) income before income taxes									12,256	11,440	9,929
Provision for (benefit from) income taxes	116	(83)	756	554	(516)	1,339	(11,122)	(357)	1,343	(10,653)	(8,425)
Net income	$ (609)	$ 5,149	$ 3,719	$ 2,654	$ 2,421	$ 4,658	$ 15,743	$ (726)	$ 10,913	$ 22,093	$ 18,354
Basic (in dollars per share)	$ (0.01)	$ 0.09	$ 0.07	$ 0.05	$ 0.04	$ 0.09	$ 0.29	$ (0.01)	$ 0.20	$ 0.41	$ 0.34
Diluted (in dollars per share)	$ (0.01)	$ 0.09	$ 0.07	$ 0.05	$ 0.04	$ 0.08	$ 0.28	$ (0.01)	$ 0.19	$ 0.40	$ 0.33
Basic (in shares)									54,740	53,764	53,701
Diluted (in shares)									56,067	55,338	55,612
Operating Segments
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Income (loss) from operations									$ 32,232	$ 28,130	$ 25,175
Operating Segments | Oil & Gas
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Income (loss) from operations									(7,377)	(4,970)	(4,211)
Product
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Product revenue	$ 15,784	$ 21,752	$ 19,226	$ 16,072	$ 13,983	$ 18,578	$ 17,406	$ 11,058			58,023
Product gross profit	11,292	16,327	13,743	11,137	10,422	13,556	11,430	7,744	52,499	43,152	38,962
Product | Operating Segments
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Product gross profit									52,499	43,152	38,962
Product | Operating Segments | Oil & Gas
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Product revenue											3,722
Product gross profit									$ (83)	$ (149)	693
License and development revenue
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Product revenue	$ 3,717	$ 3,098	$ 3,570	$ 3,723	$ 3,723	$ 3,661	$ 3,358	$ 2,749			11,106
License and development revenue | Operating Segments | Oil & Gas
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Product revenue											11,106
As Previously Reported
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Income (loss) from operations											3,276
(Loss) income before income taxes											3,956
Provision for (benefit from) income taxes											(8,394)
Net income											$ 12,350
Basic (in dollars per share)											$ 0.23
Diluted (in dollars per share)											$ 0.22
Basic (in shares)											53,701
Diluted (in shares)											55,612
As Previously Reported | Operating Segments | Oil & Gas
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Income (loss) from operations											$ (10,184)
As Previously Reported | Product
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Product revenue											58,156
Product gross profit											39,095
As Previously Reported | Product | Operating Segments | Oil & Gas
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Product revenue											3,855
Product gross profit											826
As Previously Reported | License and development revenue
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Product revenue											5,000
As Previously Reported | License and development revenue | Operating Segments | Oil & Gas
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Product revenue											5,000
Restatement Adjustment | Accounting Standards Update 2014-09
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Income (loss) from operations											5,973
(Loss) income before income taxes											5,973
Provision for (benefit from) income taxes											(31)
Net income											$ 6,004
Basic (in dollars per share)											$ 0.11
Diluted (in dollars per share)											$ 0.11
Basic (in shares)											0
Diluted (in shares)											0
Restatement Adjustment | Operating Segments | Oil & Gas | Accounting Standards Update 2014-09
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Income (loss) from operations											$ 5,973
Restatement Adjustment | Product | Accounting Standards Update 2014-09
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Product revenue											(133)
Product gross profit											(133)
Restatement Adjustment | Product | Operating Segments | Oil & Gas | Accounting Standards Update 2014-09
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Product revenue											(133)
Product gross profit											(133)
Restatement Adjustment | License and development revenue | Accounting Standards Update 2014-09
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Product revenue											6,106
Restatement Adjustment | License and development revenue | Operating Segments | Oil & Gas | Accounting Standards Update 2014-09
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Product revenue											$ 6,106

Description of Business and S_7

Description of Business and Significant Accounting Policies - Comprehensive Income (Details) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Net income	$ (609)	$ 5,149	$ 3,719	$ 2,654	$ 2,421	$ 4,658	$ 15,743	$ (726)	$ 10,913	$ 22,093	$ 18,354
Comprehensive (loss) income									$ 11,009	$ 22,085	18,347
As Previously Reported
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Net income											12,350
Comprehensive (loss) income											12,343
Restatement Adjustment | Accounting Standards Update 2014-09
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Net income											6,004
Comprehensive (loss) income											$ 6,004

Description of Business and S_8

Description of Business and Significant Accounting Policies - Cash Flows (Details) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Net income	$ (609)	$ 5,149	$ 3,719	$ 2,654	$ 2,421	$ 4,658	$ 15,743	$ (726)	$ 10,913	$ 22,093	$ 18,354
Contract assets, costs and estimated earnings in excess of billings											(4,263)
Accrued expenses and other liabilities									(600)	87	611
Income taxes									27	(447)	385
Contract liabilities									(13,943)	(13,616)	(11,858)
Net cash used in operating activities									5,268	7,565	2,895
Restricted cash											0
Net cash used in investing activities									(6,881)	(10,159)	(38,911)
Net change in cash, cash equivalents and restricted cash									4,350	(8,488)	(35,122)
Cash, cash equivalents and restricted cash, beginning of year				$ 22,138				30,626	22,138	30,626	65,748
Cash, cash equivalents and restricted cash, end of year	$ 26,488				$ 22,138				$ 26,488	22,138	30,626
As Previously Reported
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Net income											12,350
Contract assets, costs and estimated earnings in excess of billings											(4,396)
Accrued expenses and other liabilities											364
Income taxes											416
Contract liabilities											(5,505)
Net cash used in operating activities											2,895
Restricted cash											1,538
Net cash used in investing activities											(37,373)
Net change in cash, cash equivalents and restricted cash											(33,584)
Cash, cash equivalents and restricted cash, beginning of year								27,780		27,780	61,364
Cash, cash equivalents and restricted cash, end of year											27,780
Restatement Adjustment | Accounting Standards Update 2014-09
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Net income											6,004
Contract assets, costs and estimated earnings in excess of billings											133
Accrued expenses and other liabilities											247
Income taxes											(31)
Contract liabilities											(6,353)
Net cash used in operating activities											0
Restricted cash											0
Net cash used in investing activities											0
Net change in cash, cash equivalents and restricted cash											0
Cash, cash equivalents and restricted cash, beginning of year								0		0	0
Cash, cash equivalents and restricted cash, end of year											0
Restatement Adjustment | Accounting Standards Update 2016-18
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Net income											0
Contract assets, costs and estimated earnings in excess of billings											0
Accrued expenses and other liabilities											0
Income taxes											0
Contract liabilities											0
Net cash used in operating activities											0
Restricted cash											(1,538)
Net cash used in investing activities											(1,538)
Net change in cash, cash equivalents and restricted cash											(1,538)
Cash, cash equivalents and restricted cash, beginning of year								$ 2,846		$ 2,846	4,384
Cash, cash equivalents and restricted cash, end of year											$ 2,846

Revenue - Disaggregation of Rev

Revenue - Disaggregation of Revenue (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Disaggregation of Revenue [Line Items]
Revenue	$ 86,942	$ 74,515	$ 69,129
Product
Disaggregation of Revenue [Line Items]
Revenue	72,834	61,025	58,023
PX Pressure Exchangers, pumps and turbo devices
Disaggregation of Revenue [Line Items]
Revenue	72,834	61,025	58,023
License and development revenue
Disaggregation of Revenue [Line Items]
Revenue	14,108	13,490	11,106
Middle East and Africa
Disaggregation of Revenue [Line Items]
Revenue	46,678	36,107	29,898
Americas
Disaggregation of Revenue [Line Items]
Revenue	23,126	19,878	18,143
Asia
Disaggregation of Revenue [Line Items]
Revenue	11,952	11,955	12,974
Europe
Disaggregation of Revenue [Line Items]
Revenue	5,186	6,575	8,114
Water
Disaggregation of Revenue [Line Items]
Revenue	72,730	60,511	54,301
Water | PX Pressure Exchangers, pumps and turbo devices
Disaggregation of Revenue [Line Items]
Revenue	72,730	60,511	54,301
Water | License and development revenue
Disaggregation of Revenue [Line Items]
Revenue	0	0	0
Water | Middle East and Africa
Disaggregation of Revenue [Line Items]
Revenue	46,574	35,593	26,190
Water | Americas
Disaggregation of Revenue [Line Items]
Revenue	9,018	6,388	7,023
Water | Asia
Disaggregation of Revenue [Line Items]
Revenue	11,952	11,955	12,974
Water | Europe
Disaggregation of Revenue [Line Items]
Revenue	5,186	6,575	8,114
Oil and Gas
Disaggregation of Revenue [Line Items]
Revenue	14,212	14,004	14,828
Oil and Gas | PX Pressure Exchangers, pumps and turbo devices
Disaggregation of Revenue [Line Items]
Revenue	104	514	3,722
Oil and Gas | License and development revenue
Disaggregation of Revenue [Line Items]
Revenue	14,108	13,490	11,106
Oil and Gas | Middle East and Africa
Disaggregation of Revenue [Line Items]
Revenue	104	514	3,708
Oil and Gas | Americas
Disaggregation of Revenue [Line Items]
Revenue	14,108	13,490	11,120
Oil and Gas | Asia
Disaggregation of Revenue [Line Items]
Revenue	0	0	0
Oil and Gas | Europe
Disaggregation of Revenue [Line Items]
Revenue	$ 0	$ 0	$ 0

- Contract Assets and Liabiliti

- Contract Assets and Liabilities (Details) - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Revenue from Contract with Customer [Abstract]
Accounts receivable, net	$ 12,979	$ 10,212
Contract assets	501	4,083	$ 6,278
Contract assets, non-current	191	0
Total contract assets	692	4,083	6,278
Current contract liabilities:
Customer deposits	1,506	706
Deferred revenue:
Cost and estimated earnings in excess of billings	0	264
License and development	13,846	14,518
Product	78	548
Service	316	234
Total current contract liability	15,746	16,270	15,909
Non-current contract liabilities, deferred revenue
License and development	13,048	26,485
Product	72	54
Total non-current contract liability	13,120	26,539	40,517
Total contract liability	$ 28,866	$ 42,809	$ 56,426

Revenue - Significant Changes i

Revenue - Significant Changes in Contract Assets and Liabilities (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018
Change In Contract With Customer, Asset [Roll Forward]
Contract assets balance, beginning of year	$ 4,083	$ 6,278
Transferred to receivables	(13,155)	(8,865)
Additional unbilled receivables	9,764	6,670
Contract assets balance, end of period	692	4,083
Change In Contract With Customer, Liability [Roll Forward]
Contract liabilities balance, beginning of year	42,809	56,426
Revenue recognized	(15,247)	(13,493)
Increases (decreases) due to cash received, excluding amounts recognized as revenue during the period	1,304	(124)
Contract liabilities balance, end of period	$ 28,866	$ 42,809

Revenue - Remaining Performance

Revenue - Remaining Performance Obligation (Details) $ in Thousands	Dec. 31, 2019USD ($)
Revenue from Contract with Customer [Abstract]
Performance obligations expected to be satisfied	$ 46,959
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2020-01-01
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Performance obligations expected to be satisfied, expected timing	1 year
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2020-12-31
Revenue from Contract with Customer [Abstract]
Performance obligations expected to be satisfied	$ 23,514
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2021-01-01
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Performance obligations expected to be satisfied, expected timing	1 year
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2021-12-31
Revenue from Contract with Customer [Abstract]
Performance obligations expected to be satisfied	$ 17,753
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2022-01-01
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Performance obligations expected to be satisfied, expected timing	1 year
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2022-12-31
Revenue from Contract with Customer [Abstract]
Performance obligations expected to be satisfied	$ 661
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2023-01-01
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Performance obligations expected to be satisfied, expected timing	1 year
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2023-12-31
Revenue from Contract with Customer [Abstract]
Performance obligations expected to be satisfied	$ 646
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2024-01-01
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Performance obligations expected to be satisfied, expected timing	7 years
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2024-12-31
Revenue from Contract with Customer [Abstract]
Performance obligations expected to be satisfied	$ 4,385

Earnings per Share - Computatio

Earnings per Share - Computation of Basic and Diluted Earnings Per Share (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Numerator:
Net income	$ (609)	$ 5,149	$ 3,719	$ 2,654	$ 2,421	$ 4,658	$ 15,743	$ (726)	$ 10,913	$ 22,093	$ 18,354
Denominator (weighted average shares):
Basic weighted average common shares outstanding (in shares)									54,740	53,764	53,701
Weighted average effect of dilutive stock awards (in shares)									1,327	1,574	1,911
Diluted weighted average common shares outstanding (in shares)									56,067	55,338	55,612
Net income (loss) per share - basic (in dollars per share)	$ (0.01)	$ 0.09	$ 0.07	$ 0.05	$ 0.04	$ 0.09	$ 0.29	$ (0.01)	$ 0.20	$ 0.41	$ 0.34
Net income (loss) per share - diluted (in dollars per share)	$ (0.01)	$ 0.09	$ 0.07	$ 0.05	$ 0.04	$ 0.08	$ 0.28	$ (0.01)	$ 0.19	$ 0.40	$ 0.33

Earnings per Share - Antidiluti

Earnings per Share - Antidilutive Securities Excluded From Computation of Diluted Earnings Per Share (Details) - shares shares in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Earnings Per Share [Abstract]
Anti-dilutive shares excluded from net income per share calculation (in shares)	1,898	2,176	1,810

Other Financial Information - C

Other Financial Information - Cash and Restricted Cash (Details) - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Other Financial Information [Abstract]
Cash and cash equivalents	$ 26,387	$ 21,955
Restricted cash, current	0	97
Restricted cash, non-current	101	86
Total cash, cash equivalents and restricted cash	$ 26,488	$ 22,138	$ 30,626	$ 65,748

Other Financial Information - A

Other Financial Information - Accounts Receivable (Details) - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018
Other Financial Information [Abstract]
Accounts receivable, gross	$ 13,287	$ 10,608
Less: Allowance for doubtful accounts	(308)	(396)
Accounts receivable, net	$ 12,979	$ 10,212

Other Financial Information -_2

Other Financial Information - Allowance for Doubtful Accounts (Details) - Allowance for doubtful accounts - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
SEC Schedule, 12-09, Valuation and Qualifying Accounts Disclosure [Line Items]
Balance at Beginning of Period	$ 396	$ 103	$ 130
Additions	17	336	55
Changes in Estimates	(105)	(43)	(77)
Deductions	0	0	(5)
Balance at End of Years	$ 308	$ 396	$ 103

Other Financial Information - I

Other Financial Information - Inventories (Details) - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018
Other Financial Information [Abstract]
Raw materials	$ 3,742	$ 2,238
Work in process	2,141	2,689
Finished goods	4,434	2,211
Inventories, net	$ 10,317	$ 7,138

Other Financial Information -_3

Other Financial Information - Inventory Valuation Reserves (Details) - USD ($) $ in Millions	Dec. 31, 2019	Dec. 31, 2018
Other Financial Information [Abstract]
Inventory valuation reserves	$ 0.4	$ 0.7

Other Financial Information - P

Other Financial Information - Property Plant and Equipment (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Property, Plant and Equipment [Line Items]
Total property and equipment	$ 48,479	$ 41,260
Less: Accumulated depreciation and amortization	(29,636)	(26,641)
Property and equipment, net	18,843	14,619
Depreciation and amortization expense	3,820	3,228	$ 3,035
Machinery and equipment
Property, Plant and Equipment [Line Items]
Total property and equipment	27,664	23,675
Leasehold improvements
Property, Plant and Equipment [Line Items]
Total property and equipment	10,485	10,458
Software
Property, Plant and Equipment [Line Items]
Total property and equipment	3,210	3,013
Office equipment, furniture, and fixtures
Property, Plant and Equipment [Line Items]
Total property and equipment	3,011	2,970
Automobiles
Property, Plant and Equipment [Line Items]
Total property and equipment	199	199
Construction in progress
Property, Plant and Equipment [Line Items]
Total property and equipment	$ 3,910	$ 945

Other Financial Information -_4

Other Financial Information - Accrued Expenses and Other Current Liabilities (Details) - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Other Financial Information [Abstract]
Payroll and commissions payable	$ 6,040	$ 5,843
Accrued warranty reserve	631	478	$ 366	$ 406
Other accrued expenses and current liabilities	3,198	2,176
Total accrued expenses and other current liabilities	$ 9,869	$ 8,497	$ 7,948

Investments and Fair Value Me_3

Investments and Fair Value Measurements - Cash, Cash Equivalents and Investments (Details) - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018
Debt Securities, Available-for-sale [Line Items]
Cash and cash equivalents	$ 26,387	$ 21,955
Short-term investments	58,736	73,338
Long-term investments	15,419	1,269
Total cash, cash equivalents and marketable securities	100,542	96,562
Available-for-sale Securities
Debt Securities, Available-for-sale [Line Items]
Available-for-sale investments reported in cash and cash equivalents	$ 0	$ 0

Investments and Fair Value Me_4

Investments and Fair Value Measurements - Available-for-sale Securities (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	$ 74,112	$ 74,695
Gross Unrealized Holding Gains	59	2
Gross Unrealized Holding Losses	(16)	(90)
Fair Value	74,155	74,607
Sales of marketable securities	7,608	0	$ 0
Short-term Investments
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	58,697	73,426
Gross Unrealized Holding Gains	50	2
Gross Unrealized Holding Losses	(11)	(90)
Fair Value	58,736	73,338
Short-term Investments | U.S. Treasury securities
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	2,746	8,102
Gross Unrealized Holding Gains	1	1
Gross Unrealized Holding Losses	0	(2)
Fair Value	2,747	8,101
Short-term Investments | Corporate notes and bonds
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	55,951	65,324
Gross Unrealized Holding Gains	49	1
Gross Unrealized Holding Losses	(11)	(88)
Fair Value	55,989	65,237
Long-term Investments
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	15,415	1,269
Gross Unrealized Holding Gains	9	0
Gross Unrealized Holding Losses	(5)	0
Fair Value	15,419	1,269
Long-term Investments | Corporate notes and bonds
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	15,415	1,269
Gross Unrealized Holding Gains	9	0
Gross Unrealized Holding Losses	(5)	0
Fair Value	$ 15,419	$ 1,269

Investments and Fair Value Me_5

Investments and Fair Value Measurements - Amortized Cost and Fair Value of Available-for-sale Securities (Details) - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018
Investments, Fair Value Disclosure [Abstract]
Due in one year or less, amortized cost	$ 58,697
Due in one year or less, fair value	58,736
Due in greater than one year, amortized cost	15,415
Due in greater than one year, fair value	15,419
Amortized Cost	74,112	$ 74,695
Fair Value	$ 74,155	$ 74,607

Investments and Fair Value Me_6

Investments and Fair Value Measurements - Fair Value of Financial Assets and Liabilities Measured on a Recurring Basis (Details) - USD ($)	Dec. 31, 2019	Dec. 31, 2018
Assets:
Short-term investments	$ 58,736,000	$ 73,338,000
Long-term investments	15,419,000	1,269,000
Total fair value of financial liabilities	0	0
Transfer between Level 1 and Level 2	0	0
Transfers between Level 2 and Level 1	0	0
Fair Value, Measurements, Recurring
Assets:
Cash equivalents	11,668,000	6,661,000
Short-term investments	58,736,000	73,338,000
Long-term investments	15,419,000	1,269,000
Total fair value of financial assets	85,823,000	81,268,000
Fair Value, Measurements, Recurring | Level 1 Inputs
Assets:
Cash equivalents	86,000	6,661,000
Short-term investments	0	0
Long-term investments	0	0
Total fair value of financial assets	86,000	6,661,000
Fair Value, Measurements, Recurring | Level 2 Inputs
Assets:
Cash equivalents	11,582,000	0
Short-term investments	58,736,000	73,338,000
Long-term investments	15,419,000	1,269,000
Total fair value of financial assets	85,737,000	74,607,000
Fair Value, Measurements, Recurring | Level 3 Inputs
Assets:
Cash equivalents	0	0
Short-term investments	0	0
Long-term investments	0	0
Total fair value of financial assets	0	0
Corporate notes and bonds | Fair Value, Measurements, Recurring
Assets:
Short-term investments	55,989,000	65,237,000
Long-term investments	15,419,000	1,269,000
Corporate notes and bonds | Fair Value, Measurements, Recurring | Level 1 Inputs
Assets:
Short-term investments	0	0
Long-term investments	0	0
Corporate notes and bonds | Fair Value, Measurements, Recurring | Level 2 Inputs
Assets:
Short-term investments	55,989,000	65,237,000
Long-term investments	15,419,000	1,269,000
Corporate notes and bonds | Fair Value, Measurements, Recurring | Level 3 Inputs
Assets:
Short-term investments	0	0
Long-term investments	0	0
U.S. Treasury securities | Fair Value, Measurements, Recurring
Assets:
Short-term investments	2,747,000	8,101,000
U.S. Treasury securities | Fair Value, Measurements, Recurring | Level 1 Inputs
Assets:
Short-term investments	0	0
U.S. Treasury securities | Fair Value, Measurements, Recurring | Level 2 Inputs
Assets:
Short-term investments	2,747,000	8,101,000
U.S. Treasury securities | Fair Value, Measurements, Recurring | Level 3 Inputs
Assets:
Short-term investments	0	0
Money Market Funds | Fair Value, Measurements, Recurring
Assets:
Cash equivalents	86,000	6,661,000
Money Market Funds | Fair Value, Measurements, Recurring | Level 1 Inputs
Assets:
Cash equivalents	86,000	6,661,000
Money Market Funds | Fair Value, Measurements, Recurring | Level 2 Inputs
Assets:
Cash equivalents	0	0
Money Market Funds | Fair Value, Measurements, Recurring | Level 3 Inputs
Assets:
Cash equivalents	0	$ 0
U.S. Treasury securities | Fair Value, Measurements, Recurring
Assets:
Cash equivalents	11,582,000
U.S. Treasury securities | Fair Value, Measurements, Recurring | Level 1 Inputs
Assets:
Cash equivalents	0
U.S. Treasury securities | Fair Value, Measurements, Recurring | Level 2 Inputs
Assets:
Cash equivalents	11,582,000
U.S. Treasury securities | Fair Value, Measurements, Recurring | Level 3 Inputs
Assets:
Cash equivalents	$ 0

Investments and Fair Value Me_7

Investments and Fair Value Measurements - Gross Unrealized Losses and Fair Values of Investments (Details) - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018
Debt Securities, Available-for-sale [Line Items]
Fair Value	$ 20,781	$ 69,910
Gross Unrealized Losses	(16)	(90)
U.S. Treasury securities
Debt Securities, Available-for-sale [Line Items]
Fair Value	2,027	8,101
Gross Unrealized Losses	0	(2)
Corporate notes and bonds
Debt Securities, Available-for-sale [Line Items]
Fair Value	18,754	61,809
Gross Unrealized Losses	$ (16)	$ (88)

Goodwill and Intangible Asset_2

Goodwill and Intangible Assets - Goodwill (Details) - USD ($)	Dec. 31, 2019	Dec. 31, 2018
Goodwill and Intangible Assets Disclosure [Abstract]
Goodwill	$ 12,790,000	$ 12,790,000
Accumulated impairment loss	$ 0	$ 0

Goodwill and Intangible Asset_3

Goodwill and Intangible Assets - Identifiable Intangible Assets (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018
Finite-Lived Intangible Assets [Line Items]
Gross Carrying Amount	$ 6,386	$ 6,643
Accumulated Amortization	(6,321)	(6,003)
Net Carrying Amount	65	640
Developed technology
Finite-Lived Intangible Assets [Line Items]
Gross Carrying Amount	6,100	6,100
Accumulated Amortization	(6,100)	(5,541)
Net Carrying Amount	$ 0	559
Finite-live Intangible Asset, Other Info [Abstract]
Weighted Average Useful Life	10 years
Patents
Finite-Lived Intangible Assets [Line Items]
Gross Carrying Amount	$ 286	543
Accumulated Amortization	(221)	(462)
Net Carrying Amount	$ 65	$ 81
Finite-live Intangible Asset, Other Info [Abstract]
Weighted Average Useful Life	18 years

Goodwill and Intangible Asset_4

Goodwill and Intangible Assets - Intangible Asset Amortization Expense (Details) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Goodwill and Intangible Assets Disclosure [Abstract]
Amortization of intangible assets	$ 106	$ 156	$ 157	$ 156	$ 156	$ 158	$ 158	$ 158	$ 575	$ 630	$ 631

Goodwill and Intangible Asset_5

Goodwill and Intangible Assets - Intangible Asset Future Amortization (Details) - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018
Goodwill and Intangible Assets Disclosure [Abstract]
2020	$ 16
2021	12
2022	11
2023	11
2024	11
2025	4
Net Carrying Amount	$ 65	$ 640

Lines of Credit - Loan Agreemen

Lines of Credit - Loan Agreements and Stand-by Letters of Credit (Details) - USD ($)	Jan. 27, 2017	Dec. 31, 2019	Dec. 31, 2018	Aug. 24, 2018
Standby Letters of Credit
Line of Credit Facility [Line Items]
Letters of credit outstanding, amount		$ 11,800,000	$ 8,800,000
Loan and Pledge Agreement
Line of Credit Facility [Line Items]
Long-term debt		0	0
Letters of credit outstanding, amount		$ 0	$ 0
Loan and Pledge Agreement | Standby Letters of Credit
Line of Credit Facility [Line Items]
Term past expiration of agreement		1 year
Debt instrument, term		3 years
Line of Credit | Loan and Pledge Agreement | Committed Revolving Credit Line
Line of Credit Facility [Line Items]
Maximum borrowing capacity	$ 16,000,000
Line of Credit | Loan and Pledge Agreement | Uncommitted Revolving Credit Line
Line of Credit Facility [Line Items]
Maximum borrowing capacity	$ 4,000,000
Line of Credit | Loan and Pledge Agreement | Standby Letters of Credit
Line of Credit Facility [Line Items]
Basis spread on variable rate	1.50%
Commitment fee percentage		0.70%
Basis spread on variable rate, event of default	2.00%
Unused capacity, commitment fee percentage	0.20%
Line of Credit | Foreign Subsidiary | Loan and Pledge Agreement
Line of Credit Facility [Line Items]
Maximum borrowing capacity				$ 66,000,000
Other Financial Institution | Line of Credit | Loan and Pledge Agreement
Line of Credit Facility [Line Items]
Maximum borrowing capacity		$ 5,100,000

- Operating Lease Obligations (

- Operating Lease Obligations (Details) $ in Thousands	Mar. 01, 2020USD ($)ft²term	Jan. 20, 2020USD ($)ft²aterm	Dec. 31, 2019USD ($)
Operating Leases, Future Minimum Payments Due, Fiscal Year Maturity [Abstract]
2020			$ 1,855
2021			1,653
2022			1,812
2023			1,714
2024			1,922
2025 and thereafter			8,121
Total			17,077
Less imputed lease interest			(4,521)
Total lease liabilities			$ 12,556
Subsequent Event | Office And Warehouse, Katy, TX
Loss Contingencies [Line Items]
Area of leased space | ft²		25,200
Area of land | a		4.5
Operating leases, rent expense (per month)		$ 300
Operating leases, rent expense, annual increase, percent		3.00%
Operating leases, rent expense, term of contract		$ 3,600
Lease initial term		120 months
Operating lease, number of renewal terms | term		2
Operating lease, renewal term		5 years
Operating lease, renewal to extend lease, written notice period		6 months
Subsequent Event | Tracy, California | Office And Warehouse Space, Tracy Lease
Loss Contingencies [Line Items]
Area of leased space | ft²	54,429
Operating leases, rent expense (per month)	$ 400
Operating leases, rent expense, annual increase, percent	3.00%
Operating leases, rent expense, term of contract	$ 5,000
Lease initial term	122 months
Operating lease, number of renewal terms | term	1
Operating lease, renewal term	5 years
Operating lease, renewal to extend lease, written notice period	9 months

Commitments and Contingencies -

Commitments and Contingencies - Lease Cost and Terms (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Leases [Abstract]
Operating lease cost	$ 1,894	$ 1,888	$ 1,699
Cash payments	$ 1,824	$ 964	$ 1,395
Weighted average remaining lease term	8 months 27 days	9 years 9 months 18 days
Weighted average discount rate	6.97%	6.95%

Commitments and Contingencies_2

Commitments and Contingencies - Product Warranty Liability (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Movement in Standard Product Warranty Accrual [Roll Forward]
Warranty reserve balance, beginning of year	$ 478	$ 366	$ 406
Warranty costs charged to cost of revenue	402	340	246
Utilization charges against reserve	(56)	(48)	(86)
Release of accrual related to expired warranties	(193)	(180)	(200)
Warranty reserve balance, end of year	$ 631	$ 478	$ 366

Commitments and Contingencies_3

Commitments and Contingencies - Additional Information (Details) - USD ($)	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018
Loss Contingencies [Line Items]
Long-term purchase commitment	$ 10,400,000
Retention payments, percentage	10.00%
Indemnification Agreement
Loss Contingencies [Line Items]
Guarantor obligations, current carrying value	$ 0	$ 0
Minimum
Loss Contingencies [Line Items]
Retention payments, payment period after product delivery	24 months
Maximum
Loss Contingencies [Line Items]
Retention payments, payment period after product delivery	36 months

Income Taxes - Additional Infor

Income Taxes - Additional Information (Detail) - USD ($)	3 Months Ended									12 Months Ended
	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2017	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Income Tax Examination [Line Items]
Current income tax expense (benefit)										$ (51,000)	$ (274,000)	$ 471,000
Provision for (benefit from) income taxes	$ 116,000	$ (83,000)	$ 756,000	$ 554,000	$ (516,000)	$ 1,339,000	$ (11,122,000)	$ (357,000)		1,343,000	(10,653,000)	(8,425,000)
Discrete tax benefit										(1,100,000)	(13,500,000)
U.S. federal research credits										(1,000,000)
Tax deductions from stock-based compensation										(500,000)	(800,000)
Deferred tax expense	400,000									400,000
Tax Cuts And Jobs Act of 2017, transition tax for accumulated foreign earnings, provisional income tax expense (benefit)									$ 7,000,000		(12,300,000)
Tax Cuts And Jobs Act Of 2017, incomplete accounting, provisional income tax expense (benefit), cash portion									300,000
Tax Cuts And Jobs Act Of 2017, incomplete accounting, net operating loss carryovers, provisional income tax expense (benefit)									6,700,000
Tax Cuts and Jobs Act, incomplete accounting, change in tax rate, provisional income tax expense (benefit)							$ (12,100,000)					2,500,000
Deferred income tax expense (benefit)										1,394,000	(10,379,000)	(8,896,000)
Deferred tax assets, gross	26,523,000				23,285,000					26,523,000	23,285,000
Valuation allowance	3,933,000				2,850,000					3,933,000	2,850,000
Unrecognized tax benefits	963,000				$ 1,162,000				911,000	963,000	$ 1,162,000	$ 911,000	$ 603,000
Unrecognized tax benefits that would impact effective tax rate	500,000									500,000
Unrecognized tax benefits, income tax penalties and interest accrued	0									$ 0
Effective tax rate										11.00%	(93.00%)	(85.00%)
Domestic Tax Authority
Income Tax Examination [Line Items]
Deferred income tax expense (benefit)												$ (10,100,000)
Deferred tax assets, gross									1,400,000			1,400,000
Revenue Commissioners, Ireland
Income Tax Examination [Line Items]
Valuation allowance	1,200,000								$ 1,300,000	$ 1,200,000		1,300,000
Domestic And Foreign Tax Authority
Income Tax Examination [Line Items]
Current income tax expense (benefit)												$ 400,000
California Franchise Tax Board
Income Tax Examination [Line Items]
Tax credit carryforward, valuation allowance	$ 2,800,000									$ 2,800,000

Income Taxes - Provision (Benef

Income Taxes - Provision (Benefit) for Income Taxes (Details) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Income Tax Disclosure [Abstract]
U.S.									$ 12,180	$ 12,139	$ 11,549
Foreign									76	(699)	(1,620)
Total income (loss) before income taxes									12,256	11,440	9,929
Federal									(120)	(297)	441
State									3	(2)	12
Foreign									66	25	18
Current tax provision									(51)	(274)	471
Federal									949	(9,773)	(9,025)
State									445	(606)	(1,141)
Foreign									0	0	1,270
Total deferred tax benefit									1,394	(10,379)	(8,896)
Total benefit for income taxes	$ 116	$ (83)	$ 756	$ 554	$ (516)	$ 1,339	$ (11,122)	$ (357)	$ 1,343	$ (10,653)	$ (8,425)

Income Taxes - Reconciliation o

Income Taxes - Reconciliation of Income Taxes (Details)	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Income Tax Disclosure [Abstract]
U.S. federal taxes at statutory rate	21.00%	21.00%	34.00%
State income tax, net of federal benefit	4.00%	(6.00%)	1.00%
Deemed repatriation transition tax	0.00%	0.00%	71.00%
Deferred tax remeasurement - Change in tax rates	0.00%	1.00%	24.00%
Foreign rate differential	0.00%	(1.00%)	(10.00%)
Change in tax status of foreign operations	0.00%	(102.00%)	0.00%
Stock-based compensation	(1.00%)	(3.00%)	(6.00%)
Non-deductible expenses	2.00%	1.00%	1.00%
Federal research credits	(16.00%)	(6.00%)	(4.00%)
Valuation allowance	0.00%	3.00%	(197.00%)
Other	1.00%	(1.00%)	1.00%
Effective tax rate	11.00%	(93.00%)	(85.00%)

Income Taxes - Deferred Tax Ass

Income Taxes - Deferred Tax Assets and Liabilities (Details) - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Deferred tax assets:
Net operating loss carry forwards	$ 6,488	$ 5,636
Accruals and reserves	8,922	12,157
Operating lease liabilities	2,750	0
Research and development credit carry forwards	7,533	4,609
Acquired intangibles	804	859
Charitable contributions	26	24
Total deferred tax assets	26,523	23,285
Valuation allowance	(3,933)	(2,850)
Net deferred tax assets	22,590	20,435
Deferred Tax Liabilities, Net [Abstract]
Depreciation on property and equipment	(1,854)	(937)
Right of use asset	(2,443)	0
Unrecognized gain on translation of foreign currency	(33)	(9)
Goodwill	(1,363)	(1,171)
Total deferred tax liabilities	(5,693)	(2,117)
Other assets, non-current	16,897	18,318	$ 7,933
Net deferred tax asset	$ 16,897	$ 18,318

Income Taxes - Net Operating Lo

Income Taxes - Net Operating Loss Carryforwards (Details) - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018
Operating Loss Carryforwards [Line Items]
Operating loss carryforwards	$ 42,356	$ 38,882
Internal Revenue Service (IRS)
Operating Loss Carryforwards [Line Items]
Operating loss carryforwards	21,153	16,838
California Franchise Tax Board
Operating Loss Carryforwards [Line Items]
Operating loss carryforwards	11,840	12,681
Revenue Commissioners, Ireland
Operating Loss Carryforwards [Line Items]
Operating loss carryforwards	$ 9,363	$ 9,363

Income Taxes - Tax Credit Carry

Income Taxes - Tax Credit Carryforwards (Details) - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018
Tax Credit Carryforward [Line Items]
Tax credit carryforwards	$ 7,533	$ 4,609
Research And Development, Minimum Tax and Foreign Tax Credit Carryforward
Tax Credit Carryforward [Line Items]
Tax credit carryforwards	8,270	5,057
Internal Revenue Service (IRS) | Research And Development, Minimum Tax and Foreign Tax Credit Carryforward
Tax Credit Carryforward [Line Items]
Tax credit carryforwards	4,761	2,925
California Franchise Tax Board | Research And Development, Minimum Tax and Foreign Tax Credit Carryforward
Tax Credit Carryforward [Line Items]
Tax credit carryforwards	$ 3,509	$ 2,132

Income Taxes - Changes in Gross

Income Taxes - Changes in Gross Unrecognized Tax Benefit (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Income Tax Disclosure [Abstract]
Gross unrecognized tax benefits, beginning of year	$ 1,162	$ 911	$ 603
Prior year tax position	27	0	117
Current year tax position	163	251	191
Prior year tax position	(389)	0	0
Gross unrecognized tax benefits, end of year	$ 963	$ 1,162	$ 911

Stockholders' Equity - Preferre

Stockholders' Equity - Preferred and Common Stock (Details) - $ / shares	Dec. 31, 2019	Dec. 31, 2018
Stockholders' Equity Note [Abstract]
Preferred stock, shares authorized (in shares)	10,000,000	10,000,000
Preferred stock, par value (in dollars per share)	$ 0.001	$ 0.001
Preferred stock, shares outstanding (in shares)	0	0
Common stock, shares authorized (in shares)	200,000,000	200,000,000
Common stock, par value (in dollars per share)	$ 0.001	$ 0.001
Common stock, shares issued (in shares)	60,717,702	59,396,020
Common stock, shares outstanding (in shares)	55,261,767	53,940,085

Stockholders' Equity - Stock Re

Stockholders' Equity - Stock Repurchase Program (Details) - March 2018 Authorization - USD ($)	7 Months Ended	9 Months Ended
	Sep. 30, 2018	Sep. 30, 2018	Mar. 07, 2018
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock repurchase program, authorized amount			$ 10,000,000
Treasury stock, shares, acquired (in shares)	1,193,102
Treasury stock, value, acquired, cost method		$ 10,000,000

Stock-based Compensation - Plan

Stock-based Compensation - Plan Information (Details) $ / shares in Units, $ in Thousands	12 Months Ended
	Dec. 31, 2019USD ($)$ / sharesshares	Dec. 31, 2018USD ($)$ / sharesshares	Dec. 31, 2017USD ($)$ / sharesshares	Dec. 31, 2016shares
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Award vesting period	4 years
Expiration period	10 years
Compensation cost not yet recognized | $	$ 6,983
Options granted in period (in shares)	568,000	1,232,000	677,000
Granted, weighted average exercise price (in dollars per share) | $ / shares	$ 8.31	$ 7.96	$ 9.57
Awarded (in shares)	415,000	279,000	162,000
Shares outstanding (in shares)	544,000	463,000	274,000	214,000
Allocated share-based compensation expense | $	$ 5,681	$ 5,240	$ 4,087
Restricted Stock Award
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares outstanding (in shares)	0
Employee Stock Option
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Compensation cost not yet recognized | $	$ 4,031
Period for recognition	2 years 3 months 18 days
Allocated share-based compensation expense | $	$ 3,940	$ 3,873	$ 3,331
Expected dividend rate	0.00%	0.00%	0.00%
Restricted Stock Units
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Award vesting period			4 years
Compensation cost not yet recognized | $	$ 2,952
Period for recognition	2 years 8 months 12 days
Conversion ratio	1
Allocated share-based compensation expense | $	$ 1,741	$ 1,367	$ 756
The 2016 Incentive Plan
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of shares authorized (in shares)	4,441,083
Common stock, capital shares reserved for future issuance (in shares)	3,830,000
Number of shares available for grant (in shares)	2,250,197	2,603,183
The 2016 Incentive Plan | Employee Stock Options Created under New Plan
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Common stock, capital shares reserved for future issuance (in shares)	611,083
The 2016 Incentive Plan | Employee Stock Options Unissued under Prior Plan
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Common stock, capital shares reserved for future issuance (in shares)	7,635,410
Vesting Thereafter Monthly, Dependent Upon Continued Employment, Before 2017 | Restricted Stock Units
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Award vesting rights percentage				2.10%
Vesting on The First Anniversary of Grant Date, Before 2017 | Restricted Stock Units
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Award vesting rights percentage				25.00%
Vesting Annually, After 2016 | Restricted Stock Units
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Award vesting rights percentage			25.00%

Stock-based Compensation - Blac

Stock-based Compensation - Black-Scholes Option Pricing Model Assumptions (Details) - Employee Stock Option	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Weighted average expected life (years)	4 years 6 months 29 days	4 years 2 months 8 days	4 years 6 months
Weighted average expected volatility	75.90%	67.40%	80.20%
Weighted average dividend yield	0.00%	0.00%	0.00%
Minimum
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Risk-free interest rate	1.55%	2.48%	1.64%
Maximum
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Risk-free interest rate	2.57%	3.01%	1.99%

Stock-based Compensation - Shar

Stock-based Compensation - Share-based Compensation Expense (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Allocated share-based compensation expense	$ 5,681	$ 5,240	$ 4,087
Former Chairman Of Board Of Directors And President And CEO
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Additional stock-based compensation	600
Former President and Chief Executive Officer
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Additional stock-based compensation		900
Employee Stock Option
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Allocated share-based compensation expense	3,940	3,873	3,331
Restricted Stock Units
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Allocated share-based compensation expense	1,741	1,367	756
Product cost of revenue
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Allocated share-based compensation expense	130	87	158
General and administrative
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Allocated share-based compensation expense	3,090	3,266	2,218
Sales and marketing
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Allocated share-based compensation expense	836	694	821
Research and development
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Allocated share-based compensation expense	$ 1,625	$ 1,193	$ 890

Stock-based Compensation - Forf

Stock-based Compensation - Forfeiture Rate (Details)	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Stock options and RSUs vested over 4-years
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Forfeiture rate	11.60%	14.90%	16.30%

Stock-based Compensation - Unam

Stock-based Compensation - Unamortized Compensation Cost and Grant Date Fair Value (Details) $ in Thousands	12 Months Ended
	Dec. 31, 2019USD ($)
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Unamortized Compensation Costs	$ 6,983
Employee Stock Option
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Unamortized Compensation Costs	$ 4,031
Weighted Average Service Period	2 years 3 months 18 days
Restricted Stock Units
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Unamortized Compensation Costs	$ 2,952
Weighted Average Service Period	2 years 8 months 12 days

Stock-based Compensation - Stoc

Stock-based Compensation - Stock Option Activity (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding [Roll Forward]
Beginning balance (in shares)	4,982	5,092	5,883
Granted (in shares)	568	1,232	677
Exercised (in shares)	(1,133)	(1,160)	(1,226)
Forfeited (in shares)	(490)	(182)	(242)
Ending balance (in shares)	3,927	4,982	5,092
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding, Weighted Average Exercise Price [Abstract]
Beginning balance, Weighted Average Exercise Price (in dollars per share)	$ 6.36	$ 5.43	$ 4.81
Granted, weighted average exercise price (in dollars per share)	8.31	7.96	9.57
Exercised, weighted average exercise price (in dollars per share)	5.36	3.73	4.49
Forfeited, weighted average exercise price (in dollars per share)	8.49	3.98	6.60
Ending balance, Weighted average exercise price (in dollars per share)	$ 6.66	$ 6.36	$ 5.43
Weighted Average Remaining Contractual Life	6 years
Aggregate Intrinsic Value	$ 12,497
Aggregate intrinsic value, exercised	$ 4,781	$ 4,735	$ 6,798
Vested and exercisable options (in shares)	2,866
Vested and exercisable options, weighted average exercise price (in dollars per share)	$ 6.01
Vested and exercisable options, weighted average remaining contractual term	5 years 1 month 6 days
Vested and exercisable options, Aggregate Intrinsic Value	$ 10,955
Vested and exercisable, and expected to vest options (in shares)	3,807
Vested and exercisable, and expected to vest options, weighted average exercise price (in dollars per share)	$ 6.61
Vested and exercisable, and expected to vest options, weighted average remaining contractual life	5 years 10 months 24 days
Vested and exercisable, and expected to vest options, aggregate intrinsic value	$ 12,303

Stock-based Compensation - Rest

Stock-based Compensation - Restricted Stock Units Activity (Details) - $ / shares shares in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Number of Shares [Roll Forward]
Beginning balance (in shares)	463	274	214
Awarded (in shares)	415	279	162
Vested (in shares)	(201)	(90)	(91)
Forfeited (in shares)	(133)		(11)
Ending balance (in shares)	544	463	274
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Weighted Average Grant Date Fair Value [Abstract]
Beginning balance, Weighted average grant-date fair value (in dollars per share)	$ 8.49	$ 9.54	$ 8.65
Awarded, Weighted average grant-date fair value (in dollars per share)	7.80	7.74	10.14
Vested, Weighted average grant-date fair value, (in dollars per share)	8.62	9.33	8.65
Forfeited, Weighted average grant-date fair value (in dollars per share)	8.37		8.52
Ending balance, Weighted average grant-date fair value (in dollars per share)	$ 7.95	$ 8.49	$ 9.54

Stock-based Compensation - Vest

Stock-based Compensation - Vested Stock Options and RSUs (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Total grant date fair value of stock options and RSUs vested during the period	$ 5,758	$ 4,448	$ 4,158
Employee Stock Option
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Total grant date fair value of stock options and RSUs vested during the period	4,025	3,607	3,375
Restricted Stock Units
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Total grant date fair value of stock options and RSUs vested during the period	$ 1,733	$ 841	$ 783

Business Segment - Summary of F

Business Segment - Summary of Financial Information by Segment (Details) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Segment Reporting Information [Line Items]
Revenue									$ 86,942	$ 74,515	$ 69,129
General and administrative	$ 6,042	$ 5,711	$ 5,500	$ 5,579	$ 5,446	$ 5,266	$ 4,927	$ 5,837	22,832	21,476	17,354
Sales and marketing	2,724	2,367	2,181	2,162	1,903	1,873	1,858	1,912	9,434	7,546	9,391
Research and development	7,048	6,620	5,480	4,254	5,220	4,270	3,605	3,917	23,402	17,012	13,443
Amortization of intangibles	106	156	157	156	156	158	158	158	575	630	631
Total operating expenses	15,920	14,854	13,318	12,151	12,725	11,567	10,548	11,824	56,243	46,664	40,819
Income from operations	(911)	4,571	3,995	2,709	1,420	5,650	4,240	(1,331)	10,364	9,978	9,249
Other income									1,892	1,462	680
Income before income taxes									12,256	11,440	9,929
Water
Segment Reporting Information [Line Items]
Revenue									72,730	60,511	54,301
Oil & Gas
Segment Reporting Information [Line Items]
Revenue									14,212	14,004	14,828
Operating Segments
Segment Reporting Information [Line Items]
General and administrative									3,077	3,849	2,966
Sales and marketing									7,813	7,047	8,015
Research and development									22,910	16,987	13,281
Amortization of intangibles									575	629	631
Total operating expenses									34,375	28,512	24,893
Income from operations									32,232	28,130	25,175
Operating Segments | Water
Segment Reporting Information [Line Items]
General and administrative									1,501	2,078	1,401
Sales and marketing									7,072	5,783	5,787
Research and development									3,825	1,711	1,064
Amortization of intangibles									575	629	631
Total operating expenses									12,973	10,201	8,883
Income from operations									39,609	33,100	29,386
Operating Segments | Oil & Gas
Segment Reporting Information [Line Items]
General and administrative									1,576	1,771	1,565
Sales and marketing									741	1,264	2,228
Research and development									19,085	15,276	12,217
Amortization of intangibles									0	0	0
Total operating expenses									21,402	18,311	16,010
Income from operations									(7,377)	(4,970)	(4,211)
Corporate
Segment Reporting Information [Line Items]
Total operating expenses									21,868	18,152	15,926
Product
Segment Reporting Information [Line Items]
Revenue									72,834	61,025	58,023
Product cost of revenue	4,492	5,425	5,483	4,935	3,561	5,022	5,976	3,314	20,335	17,873	19,061
Product gross profit	$ 11,292	$ 16,327	$ 13,743	$ 11,137	$ 10,422	$ 13,556	$ 11,430	$ 7,744	52,499	43,152	38,962
Product | Operating Segments
Segment Reporting Information [Line Items]
Revenue									72,834	61,025	58,023
Product cost of revenue									20,335	17,873	19,061
Product gross profit									52,499	43,152	38,962
Product | Operating Segments | Water
Segment Reporting Information [Line Items]
Revenue									72,730	60,512	54,301
Product cost of revenue									20,148	17,211	16,032
Product gross profit									52,582	43,301	38,269
Product | Operating Segments | Oil & Gas
Segment Reporting Information [Line Items]
Revenue									104	513	3,722
Product cost of revenue									187	662	3,029
Product gross profit									(83)	(149)	693
License and development revenue
Segment Reporting Information [Line Items]
Revenue									14,108	13,490	11,106
License and development revenue | Water
Segment Reporting Information [Line Items]
Revenue									0	0	0
License and development revenue | Oil & Gas
Segment Reporting Information [Line Items]
Revenue									14,108	13,490	11,106
License and development revenue | Operating Segments
Segment Reporting Information [Line Items]
Revenue									14,108	13,490	11,106
License and development revenue | Operating Segments | Water
Segment Reporting Information [Line Items]
Revenue									0	0	0
License and development revenue | Operating Segments | Oil & Gas
Segment Reporting Information [Line Items]
Revenue									$ 14,108	$ 13,490	$ 11,106

Business Segment - Depreciation

Business Segment - Depreciation and Amortization Expense by Segment (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Segment Reporting Information [Line Items]
Depreciation and amortization expense	$ 4,395	$ 3,869	$ 3,666
Operating Segments | Water
Segment Reporting Information [Line Items]
Depreciation and amortization expense	1,824	2,060	2,723
Operating Segments | Oil & Gas
Segment Reporting Information [Line Items]
Depreciation and amortization expense	2,251	1,377	448
Corporate
Segment Reporting Information [Line Items]
Depreciation and amortization expense	$ 320	$ 432	$ 495

Concentrations - Product Revenu

Concentrations - Product Revenue by Geographic Locations (Details) - Product Revenue	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Segment Reporting Information [Line Items]
Concentration risk, percentage	100.00%	100.00%	100.00%
United States
Segment Reporting Information [Line Items]
Concentration risk, percentage	2.00%	3.00%	3.00%
International
Segment Reporting Information [Line Items]
Concentration risk, percentage	98.00%	97.00%	97.00%
Saudi Arabia
Segment Reporting Information [Line Items]
Concentration risk, percentage	29.00%	31.00%	13.00%
United Arab Emirates
Segment Reporting Information [Line Items]
Concentration risk, percentage	10.00%
Egypt
Segment Reporting Information [Line Items]
Concentration risk, percentage		17.00%	15.00%
Others
Segment Reporting Information [Line Items]
Concentration risk, percentage	61.00%	52.00%	72.00%

Concentrations - Product Reve_2

Concentrations - Product Revenue Concentrations (Details)	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Product Revenue
Concentration Risk [Line Items]
Percentage of product revenue	100.00%	100.00%	100.00%
Water | Customer A
Concentration Risk [Line Items]
Percentage of product revenue	19.00%
Water | Customer B
Concentration Risk [Line Items]
Percentage of product revenue		15.00%
Water | Customer F
Concentration Risk [Line Items]
Percentage of product revenue		11.00%

Concentrations - License and De

Concentrations - License and Development (Detail) - Product Revenue	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Concentration Risk [Line Items]
Concentration risk, percentage	100.00%	100.00%	100.00%
License and Development Revenue | One Customer | Customer Concentration Risk
Concentration Risk [Line Items]
Concentration risk, percentage	100.00%	100.00%	100.00%

Concentrations - Accounts Recei

Concentrations - Accounts Receivable Concentrations (Details)	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018
Water | Customer A
Concentration Risk [Line Items]
Concentration risk, percentage	19.00%
Water | Customer A | Accounts Receivable | Customer Concentration Risk
Concentration Risk [Line Items]
Concentration risk, percentage	30.00%
Water | Customer F
Concentration Risk [Line Items]
Concentration risk, percentage		11.00%
Water | Customer D | Accounts Receivable | Customer Concentration Risk
Concentration Risk [Line Items]
Concentration risk, percentage		11.00%
Oil and Gas | Customer A | Accounts Receivable | Customer Concentration Risk
Concentration Risk [Line Items]
Concentration risk, percentage		26.00%
Oil and Gas | Customer D | Accounts Receivable | Customer Concentration Risk
Concentration Risk [Line Items]
Concentration risk, percentage		20.00%

Concentrations - Major Supply V

Concentrations - Major Supply Vendors (Details) - Major Supply Vendors - Customer Concentration Risk	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018
Vendor A
Concentration Risk [Line Items]
Concentration risk, percentage	22.00%	18.00%
Vendor B
Concentration Risk [Line Items]
Concentration risk, percentage	13.00%	10.00%

VorTeq Partnership and Licens_2

VorTeq Partnership and License Agreement (Details) - VorTeq License Agreement	Oct. 14, 2015USD ($)payment	Dec. 31, 2019USD ($)payment	Dec. 31, 2014missile
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
License agreement term		15 years
VorTeq license agreement payments	$ 125,000,000
Up front non-refundable payment	$ 75,000,000	$ 75,000,000
Number of milestone payments | payment	2	2
Milestone Payment One Upon Successful Yard Test
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
VorTeq milestone payment to be received	$ 25,000,000
Milestone Payment Two Upon Successful Fracing of ALive Well
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
VorTeq milestone payment to be received		$ 25,000,000
Affiliated Entity | Liberty Oil Field Services
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Number of missiles available for lease | missile			20
License agreement term			5 years

Supplementary Data _ Quarterl_3

Supplementary Data — Quarterly Financial Data (unaudited) (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
General and administrative	$ 6,042	$ 5,711	$ 5,500	$ 5,579	$ 5,446	$ 5,266	$ 4,927	$ 5,837	$ 22,832	$ 21,476	$ 17,354
Sales and marketing	2,724	2,367	2,181	2,162	1,903	1,873	1,858	1,912	9,434	7,546	9,391
Research and development	7,048	6,620	5,480	4,254	5,220	4,270	3,605	3,917	23,402	17,012	13,443
Amortization of intangible assets	106	156	157	156	156	158	158	158	575	630	631
Operating Expenses	15,920	14,854	13,318	12,151	12,725	11,567	10,548	11,824	56,243	46,664	40,819
Total operating expenses	(911)	4,571	3,995	2,709	1,420	5,650	4,240	(1,331)	10,364	9,978	9,249
Provision for (benefit from) income taxes	116	(83)	756	554	(516)	1,339	(11,122)	(357)	1,343	(10,653)	(8,425)
Income (loss) from operations	$ (609)	$ 5,149	$ 3,719	$ 2,654	$ 2,421	$ 4,658	$ 15,743	$ (726)	$ 10,913	$ 22,093	$ 18,354
Basic (in dollars per share)	$ (0.01)	$ 0.09	$ 0.07	$ 0.05	$ 0.04	$ 0.09	$ 0.29	$ (0.01)	$ 0.20	$ 0.41	$ 0.34
Diluted (in dollars per share)	$ (0.01)	$ 0.09	$ 0.07	$ 0.05	$ 0.04	$ 0.08	$ 0.28	$ (0.01)	$ 0.19	$ 0.40	$ 0.33
Tax Cuts and Jobs Act, incomplete accounting, change in tax rate, provisional income tax expense (benefit)							$ (12,100)				$ 2,500
Tax Cuts And Jobs Act Of 2017, incomplete accounting, change in tax rate, deferred tax asset, provisional income tax expense (benefit)							(11,900)
License and development revenue
Revenue	$ 3,717	$ 3,098	$ 3,570	$ 3,723	$ 3,723	$ 3,661	3,358	$ 2,749			11,106
Product
Revenue	15,784	21,752	19,226	16,072	13,983	18,578	17,406	11,058			58,023
Product cost of revenue	4,492	5,425	5,483	4,935	3,561	5,022	5,976	3,314	$ 20,335	$ 17,873	19,061
Product gross profit	$ 11,292	$ 16,327	$ 13,743	$ 11,137	$ 10,422	$ 13,556	$ 11,430	$ 7,744	$ 52,499	$ 43,152	$ 38,962