Energy Recovery (ERII) 10-Q 6 Aug 21 2021 Q2 Quarterly report Financial data

Cover Page

Cover Page - shares	6 Months Ended
	Jun. 30, 2021	Jul. 30, 2021
Cover [Abstract]
Document Type	10-Q
Document Quarterly Report	true
Current Fiscal Year End Date	--12-31
Document Period End Date	Jun. 30, 2021
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
Trading Symbol	ERII
Security Exchange Name	NASDAQ
Entity Current Reporting Status	Yes
Entity Interactive Data Current	Yes
Entity Filer Category	Non-accelerated Filer
Entity Small Business	true
Entity Emerging Growth Company	false
Entity Shell Company	false
Entity Common Stock, Shares Outstanding (in shares)		57,152,300
Entity Central Index Key	0001421517
Document Fiscal Year Focus	2021
Document Fiscal Period Focus	Q2
Amendment Flag	false

CONDENSED CONSOLIDATED BALANCE

CONDENSED CONSOLIDATED BALANCE SHEETS - USD ($) $ in Thousands	Jun. 30, 2021	Dec. 31, 2020
Current assets:
Cash and cash equivalents	$ 103,302	$ 94,255
Short-term investments	17,394	20,446
Accounts receivable, net	7,599	11,792
Inventories, net	15,289	11,748
Prepaid expenses and other assets, current	4,265	4,950
Total current assets	147,849	143,191
Deferred tax assets, net	12,471	11,030
Property and equipment, net	20,443	20,176
Operating lease, right of use asset	15,383	16,090
Goodwill and other intangible assets	12,833	12,839
Other assets, non-current	365	988
Total assets	209,344	204,314
Current liabilities:
Accounts payable	2,278	1,118
Accrued expenses and other liabilities, current	8,397	11,816
Lease liabilities, current	1,473	1,243
Contract liabilities, current	1,117	1,552
Total current liabilities	13,265	15,729
Lease liabilities, non-current	15,682	16,443
Other liabilities, non-current	571	518
Total liabilities	29,518	32,690
Commitments and contingencies (Note 7)
Stockholders’ equity:
Common stock	63	62
Additional paid-in capital	191,087	179,161
Accumulated other comprehensive (loss) income	(53)	53
Treasury stock	(42,040)	(30,486)
Retained earnings	30,769	22,834
Total stockholders’ equity	179,826	171,624
Total liabilities and stockholders’ equity	$ 209,344	$ 204,314

CONDENSED CONSOLIDATED STATEMEN

CONDENSED CONSOLIDATED STATEMENTS OF OPERATIONS - USD ($) shares in Thousands, $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020
Revenue, Product and Service [Extensible List]	Product	Product	Product	Product
Cost, Product and Service [Extensible List]	Product	Product	Product	Product
Revenue	$ 20,607	$ 43,608	$ 49,547	$ 65,152
Operating expenses:
General and administrative	6,175	5,599	12,781	12,480
Sales and marketing	2,537	1,497	5,240	3,635
Research and development	4,424	6,352	8,926	13,061
Amortization of intangible assets	3	4	7	8
Impairment of long-lived assets	0	2,332	0	2,332
Total operating expenses	13,139	15,784	26,954	31,516
Income from operations	287	21,275	6,431	21,403
Other Nonoperating Income (Expense) [Abstract]
Interest income	51	255	143	675
Other non-operating expense, net	(12)	(18)	(22)	(30)
Total other income, net	39	237	121	645
Income before income taxes	326	21,512	6,552	22,048
(Benefit from) provision for income taxes	(743)	4,586	(1,383)	4,501
Net income	$ 1,069	$ 16,926	$ 7,935	$ 17,547
Net income per share:
Basic (in dollars per share)	$ 0.02	$ 0.30	$ 0.14	$ 0.32
Diluted (in dollars per share)	$ 0.02	$ 0.30	$ 0.13	$ 0.31
Number of shares used in per share calculations:
Basic (in shares)	57,253	55,614	57,066	55,513
Diluted (in shares)	58,999	56,371	58,822	56,438
Product
Revenue	$ 20,607	$ 19,256	$ 49,547	$ 38,257
Product cost of revenue	7,181	6,549	16,162	12,233
Product gross profit	13,426	12,707	33,385	26,024
License and development
Revenue	$ 0	$ 24,352	$ 0	$ 26,895

CONDENSED CONSOLIDATED STATEM_2

CONDENSED CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME (LOSS) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020
Statement of Comprehensive Income [Abstract]
Net income	$ 1,069	$ 16,926	$ 7,935	$ 17,547
Other comprehensive (loss) income, net of tax
Foreign currency translation adjustments	5	10	(20)	(15)
Unrealized (loss) gain on investments	(38)	441	(86)	171
Total other comprehensive (loss) income, net of tax	(33)	451	(106)	156
Comprehensive income	$ 1,036	$ 17,377	$ 7,829	$ 17,703

CONDENSED CONSOLIDATED STATEM_3

CONDENSED CONSOLIDATED STATEMENTS OF STOCKHOLDERS' EQUITY - USD ($) $ in Thousands	Total	Common stock	Additional paid-in capital	Accumulated other comprehensive (loss) income	Treasury stock	Retained earnings
Beginning balance at Dec. 31, 2019		$ 61	$ 170,028	$ (37)	$ (30,486)	$ (3,553)
Increase (Decrease) in Stockholders' Equity
Issuance of common stock, net		0	1,105
Stock-based compensation			2,596
Foreign currency translation adjustments				(15)
Unrealized (loss) gain on investments				171
Common stock repurchased					0
Total other comprehensive (loss) income, net of tax	$ 156			156
Net income	17,547					17,547
Ending balance at Jun. 30, 2020	$ 157,417	$ 61	173,729	119	$ (30,486)	13,994
Beginning balance (in shares) at Dec. 31, 2019		60,717,702			5,455,935
Increase (Decrease) in Stockholders' Equity
Issuance of common stock (in shares)		415,615
Common stock repurchased (in shares)					0
Ending balance (in shares) at Jun. 30, 2020	55,677,382	61,133,317			5,455,935
Beginning balance at Mar. 31, 2020		$ 61	171,954	(332)	$ (30,486)	(2,932)
Increase (Decrease) in Stockholders' Equity
Issuance of common stock, net		0	687
Stock-based compensation			1,088
Foreign currency translation adjustments				10
Unrealized (loss) gain on investments				441
Common stock repurchased					0
Total other comprehensive (loss) income, net of tax	$ 451			451
Net income	16,926					16,926
Ending balance at Jun. 30, 2020	$ 157,417	$ 61	173,729	119	$ (30,486)	13,994
Beginning balance (in shares) at Mar. 31, 2020		60,999,233			5,455,935
Increase (Decrease) in Stockholders' Equity
Issuance of common stock (in shares)		134,084
Common stock repurchased (in shares)					0
Ending balance (in shares) at Jun. 30, 2020	55,677,382	61,133,317			5,455,935
Beginning balance at Dec. 31, 2020	$ 171,624	$ 62	179,161	53	$ (30,486)	22,834
Increase (Decrease) in Stockholders' Equity
Issuance of common stock, net		1	8,696
Stock-based compensation			3,230
Foreign currency translation adjustments				(20)
Unrealized (loss) gain on investments				(86)
Common stock repurchased					(11,554)
Total other comprehensive (loss) income, net of tax	(106)			(106)
Net income	7,935					7,935
Ending balance at Jun. 30, 2021	$ 179,826	$ 63	191,087	(53)	$ (42,040)	30,769
Beginning balance (in shares) at Dec. 31, 2020		61,798,004			5,455,935
Increase (Decrease) in Stockholders' Equity
Issuance of common stock (in shares)		1,469,289
Common stock repurchased (in shares)					656,938
Ending balance (in shares) at Jun. 30, 2021	57,154,420	63,267,293			6,112,873
Beginning balance at Mar. 31, 2021		$ 63	187,083	(20)	$ (30,486)	29,700
Increase (Decrease) in Stockholders' Equity
Issuance of common stock, net		0	2,638
Stock-based compensation			1,366
Foreign currency translation adjustments				5
Unrealized (loss) gain on investments				(38)
Common stock repurchased					(11,554)
Total other comprehensive (loss) income, net of tax	$ (33)			(33)
Net income	1,069					1,069
Ending balance at Jun. 30, 2021	$ 179,826	$ 63	$ 191,087	$ (53)	$ (42,040)	$ 30,769
Beginning balance (in shares) at Mar. 31, 2021		62,877,567			5,455,935
Increase (Decrease) in Stockholders' Equity
Issuance of common stock (in shares)		389,726
Common stock repurchased (in shares)					656,938
Ending balance (in shares) at Jun. 30, 2021	57,154,420	63,267,293			6,112,873

CONDENSED CONSOLIDATED STATEM_4

CONDENSED CONSOLIDATED STATEMENTS OF CASH FLOWS - USD ($) $ in Thousands	6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020
Cash flows from operating activities:
Net income	$ 7,935	$ 17,547
Adjustments to reconcile net income to cash provided by (used in) operating activities
Stock-based compensation	3,341	2,595
Depreciation and amortization	2,733	2,751
Amortization of premiums and discounts on investments	139	215
Deferred income taxes	(1,441)	4,666
Impairment of long-lived assets	0	2,332
Other non-cash adjustments	149	228
Changes in operating assets and liabilities:
Accounts receivable, net	4,193	101
Contract assets	1,356	(198)
Inventories, net	(3,621)	260
Prepaid and other assets	(47)	(278)
Accounts payable	1,237	1,285
Accrued expenses and other liabilities	(3,999)	(4,009)
Contract liabilities	(434)	(27,789)
Net cash provided by (used in) operating activities	11,541	(294)
Cash flows from investing activities:
Sales of marketable securities	0	9,767
Maturities of marketable securities	14,861	43,286
Purchases of marketable securities	(12,034)	(12,855)
Capital expenditures	(2,449)	(4,410)
Other	5	0
Net cash provided by investing activities	383	35,788
Cash flows from financing activities:
Net proceeds from issuance of common stock	8,697	1,128
Tax payment for employee shares withheld	0	(23)
Repurchase of common stock	(11,554)	0
Net cash (used in) provided by financing activities	(2,857)	1,105
Effect of exchange rate differences on cash and cash equivalents	(20)	(15)
Net change in cash, cash equivalents and restricted cash	9,047	36,584
Cash, cash equivalents and restricted cash, beginning of year	94,358	26,488
Cash, cash equivalents and restricted cash, end of period	$ 103,405	$ 63,072

Description of Business and Sig

Description of Business and Significant Accounting Policies	6 Months Ended
	Jun. 30, 2021
Accounting Policies [Abstract]
Description of Business and Significant Accounting Policies	Note 1 — Description of Business and Significant Accounting Policies Energy Recovery, Inc. and its wholly-owned subsidiaries (the “Company” or “Energy Recovery”) create technologies that solve complex challenges for industrial fluid-flow markets worldwide. Building on the Company’s pressure exchanger technology platform, the Company designs and manufactures solutions that improve operational efficiency by reducing waste, energy consumption and costs across a range of industrial processes. What began as a game-changing invention for desalination has grown into a global business advancing the environmental sustainability of the Company’s customers’ operations in multiple industries. The Company’s solutions are marketed, sold in, or developed for, the fluid-flow and gas markets, such as water, industrial waste, oil & gas, chemical processing and refrigeration, under the trademarks ERI ® , Ultra PX ™ , PX ® , Pressure Exchanger ® , PX Pressure Exchanger ® (“PX”), PX PowerTrain ™ , VorTeq ™ , IsoBoost ® , AT ™ , AquaBold ™ , and PX G1300 ™ . 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 Condensed Consolidated Financial Statements include the accounts of Energy Recovery, Inc. and its wholly-owned subsidiaries. All intercompany accounts and transactions have been eliminated in consolidation. The accompanying Condensed Consolidated Financial Statements have been prepared pursuant to the rules and regulations of the Securities and Exchange Commission (the “SEC”). Certain information and footnote disclosures normally included in the financial statements prepared in accordance with U.S. generally accepted accounting principles (“GAAP”) have been condensed or omitted pursuant to such rules and regulations. The December 31, 2020 Condensed Consolidated Balance Sheet was derived from audited financial statements and may not include all disclosures required by GAAP; however, the Company believes that the disclosures are adequate to make the information presented not misleading. The June 30, 2021 unaudited Condensed Consolidated Financial Statements should be read in conjunction with the audited Consolidated Financial Statements and the notes thereto for the fiscal year ended December 31, 2020 included in the Company’s Annual Report on Form 10-K filed with the SEC on March 12, 2021 (the “2020 Annual Report”). All adjustments consisting of normal recurring adjustments that are necessary to present fairly the financial position, results of operations and cash flows for the interim periods have been made. The results of operations for the interim periods are not necessarily indicative of the operating results for the full fiscal year or any future periods. Reclassifications Certain prior period amounts have been reclassified in the Condensed Consolidated Balance Sheets, Condensed Consolidated Statements of Cash Flows, and certain notes to the Condensed Consolidated Financial Statements, to conform to the current period presentation. Use of Estimates The preparation of Condensed Consolidated Financial Statements, in conformity with GAAP, requires the Company’s management to make judgments, assumptions and estimates that affect the amounts reported in the Condensed 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; valuation of stock options; valuation and impairment of goodwill; 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. In December 2019, the Financial Accounting Standards Board (“FASB”) issued Accounting Standards Update (“ASU”) No. 2019-12, Income Taxes (Topic 740): Simplifying the Accounting for Income Taxes (“ASU 2019-12”), which simplifies the accounting for income taxes by removing certain exceptions to the general principles in Topic 740 and also clarifies and amends existing guidance to improve consistent application. The new standard is effective for interim and annual periods beginning after December 15, 2020. The Company adopted ASU 2019-12 on January 1, 2021. The adoption of ASU 2019-12 did not have a material impact on the Company’s consolidated financial condition, results of operations, and cash flows. In March 2020, the FASB issued ASU No. 2020-04, Reference Rate Reform (Topic 848) (“ASU 2020-04”), which provided optional expedients and exceptions for applying GAAP to contracts, hedging relationships, and other transactions affected by the discontinuation of the London Interbank Offered Rate (“LIBOR”) or by another reference rate expected to be discontinued. The FASB later issued ASU No. 2021-01, Reference Rate Reform (Topic 848): Scope, to clarify the scope of Topic 848 so that derivatives affected by the discounting transition are explicitly eligible for certain optional expedients and exceptions in Topic 848 (“ASU 2021-01”). Entities may apply the provisions of the new standards as of the beginning of the reporting period when the election is made (i.e., as early as the first quarter of 2020). Unlike other topics, the provisions of this update are only available until December 31, 2022, when the reference rate replacement activity is expected to have been completed. An entity may elect to apply amendments prospectively through December 31, 2022. The optional expedients were available to be used upon issuance of this guidance but the Company has not yet applied the guidance because the Company has not yet modified its existing contract for reference rate reform. The Company does not expect the provisions of ASU 2020-04 or ASU 2021-01 to have a material impact on its financial condition, results of operation, and cash flows.

Revenue

Revenue	6 Months Ended
	Jun. 30, 2021
Revenue from Contract with Customer [Abstract]
Revenue	Revenue Disaggregation of Revenue The following tables present the disaggregated revenues by product and service line, product revenue by geography based on the “shipped to” addresses of the Company’s customers, product revenue by channel, and product revenue by segment (Water and Emerging Technologies segment). Sales and usage-based taxes are excluded from revenues. See Note 10, “Segment Reporting,” for further discussion related to the Company’s segments. Three Months Ended June 30, 2021 Six Months Ended June 30, 2021 Water Emerging Technologies Total Water Emerging Technologies Total (In thousands) Revenue by product and service line PXs, pumps and turbo devices, and other $ 20,568 $ 39 $ 20,607 $ 49,508 $ 39 $ 49,547 Revenue by primary geographical markets Middle East and Africa $ 16,401 $ 39 $ 16,440 $ 37,361 $ 39 $ 37,400 Asia 2,325 — 2,325 9,503 — 9,503 Americas 945 — 945 1,368 — 1,368 Europe 897 — 897 1,276 — 1,276 Total revenue $ 20,568 $ 39 $ 20,607 $ 49,508 $ 39 $ 49,547 Product revenue by channel Megaproject $ 13,236 $ 39 $ 13,275 $ 36,993 $ 39 $ 37,032 Original equipment manufacturer 4,274 — 4,274 7,065 — 7,065 Aftermarket 3,058 — 3,058 5,450 — 5,450 Total product revenue $ 20,568 $ 39 $ 20,607 $ 49,508 $ 39 $ 49,547 Three Months Ended June 30, 2020 Six Months Ended June 30, 2020 Water Emerging Technologies Total Water Emerging Technologies Total (In thousands) Revenue by product and service line PXs, pumps and turbo devices, and other $ 19,256 $ — $ 19,256 $ 38,257 $ — $ 38,257 License and development — 24,352 24,352 — 26,895 26,895 Total revenue $ 19,256 $ 24,352 $ 43,608 $ 38,257 $ 26,895 $ 65,152 Revenue by primary geographical markets Middle East and Africa $ 16,504 $ — $ 16,504 $ 32,735 $ — $ 32,735 Asia 617 — 617 1,392 — 1,392 Americas 1,161 24,352 25,513 2,362 26,895 29,257 Europe 974 — 974 1,768 — 1,768 Total product revenue $ 19,256 $ 24,352 $ 43,608 $ 38,257 $ 26,895 $ 65,152 Product revenue by channel Megaproject $ 11,965 $ — $ 11,965 $ 26,422 $ — $ 26,422 Original equipment manufacturer 4,050 — 4,050 7,606 — 7,606 Aftermarket 3,241 — 3,241 4,229 — 4,229 Total product revenue $ 19,256 $ — $ 19,256 $ 38,257 $ — $ 38,257 Contract Balances The following table presents contract balances by category. June 30, December 31, (In thousands) Accounts receivable, net $ 7,599 $ 11,792 Contract assets: Contract assets, current (included in prepaid expenses and other assets, current) $ 536 $ 1,309 Contract assets, non-current (included in other assets, non-current) — 583 Total contract assets $ 536 $ 1,892 Contract liabilities: Contract liabilities, current $ 1,117 $ 1,552 Contract liabilities, non-current (included in other liabilities, non-current) 89 88 Total contract liabilities $ 1,206 $ 1,640 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. June 30, December 31, (In thousands) Contract liabilities balance, beginning of year $ 1,640 $ 28,866 Revenue recognized (1,232) (28,414) Cash received, excluding amounts recognized as revenue during the period 798 1,188 Contract liabilities balance, end of period $ 1,206 $ 1,640 Transaction Price Allocated to the Remaining Performance Obligations The following table presents the estimated revenue expected to be recognized in the future related to performance obligations that are unsatisfied or partially unsatisfied. June 30, (In thousands) Future performance obligations by year 2021 (remaining six months) $ 4,036 2022 12,191 Total future performance obligations $ 16,227

Net Income Per Share

Net Income Per Share	6 Months Ended
	Jun. 30, 2021
Earnings Per Share [Abstract]
Net Income Per Share	Note 3 — Net Income 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 net income per common share. Basic net income per share excludes any dilutive effect of stock options and restricted stock units ("RSU"). Diluted net income 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 (outstanding stock options to purchase common stock and RSUs collectively referred to as, “stock awards”). The following table presents the computation of basic and diluted net income per share. Three Months Ended June 30, Six Months Ended June 30, 2021 2020 2021 2020 (In thousands, except per share amounts) Numerator Net income $ 1,069 $ 16,926 $ 7,935 $ 17,547 Denominator (weighted average shares) Basic common shares outstanding 57,253 55,614 57,066 55,513 Dilutive stock awards 1,746 757 1,756 925 Diluted common shares outstanding 58,999 56,371 58,822 56,438 Net income per share Basic $ 0.02 $ 0.30 $ 0.14 $ 0.32 Diluted $ 0.02 $ 0.30 $ 0.13 $ 0.31 Certain shares of common stock issuable under stock awards have been omitted from the diluted net income per share calculations because their inclusion is considered anti-dilutive. The following table presents the weighted potential common shares issuable under stock awards that were excluded from the computation of diluted net income per share. Three Months Ended June 30, Six Months Ended June 30, 2021 2020 2021 2020 (In thousands) Anti-dilutive stock awards 6 2,893 457 1,989

Other Financial Information

Other Financial Information	6 Months Ended
	Jun. 30, 2021
Other Financial Information [Abstract]
Other Financial Information	Other Financial Information Cash, Cash Equivalents and Restricted Cash The Condensed Consolidated Statements of Cash Flows explain the changes in the total of cash, cash equivalents and restricted cash. The following table presents a reconciliation of cash, cash equivalents and restricted cash (1) reported within the Condensed Consolidated Balance Sheets that sum to the total of such amounts presented. June 30, December 31, June 30, (In thousands) Cash and cash equivalents $ 103,302 $ 94,255 $ 62,970 Restricted cash, non-current (included in other assets, non-current) 103 103 102 Total cash, cash equivalents and restricted cash $ 103,405 $ 94,358 $ 63,072 (1) The Company pledged and deposited cash amounts into restricted cash accounts in connection with the Company’s credit cards. Accounts Receivable, net The following table presents the components of accounts receivable, net. June 30, December 31, (In thousands) Accounts receivable, gross $ 7,716 $ 12,189 Allowance for doubtful accounts (1) (117) (397) Accounts receivable, net $ 7,599 $ 11,792 (1) The Company wrote-off $0.3 million of uncollectible receivables, which had been previously reserved as of December 31, 2020, during the second quarter of 2021. Inventories Inventories are stated at the lower of cost or net realizable value, using the first-in, first-out method. The following table presents inventory by category. June 30, December 31, (In thousands) Raw materials $ 5,161 $ 4,260 Work in process 2,740 2,360 Finished goods 7,388 5,128 Inventories, net $ 15,289 $ 11,748 Valuation adjustments for excess and obsolete inventory reflected as a reduction of inventory was $0.6 million and $0.5 million at June 30, 2021 and December 31, 2020, respectively. Prepaid and Other Current Assets June 30, December 31, (In thousands) Contract assets, current $ 536 $ 1,309 Cloud computing arrangement implementation costs 1,095 1,087 Other prepaid expenses and current assets 2,634 2,554 Total prepaid and other current assets $ 4,265 $ 4,950 Goodwill and Other Intangible Assets June 30, December 31, (In thousands) Goodwill $ 12,790 $ 12,790 Other intangible assets 43 49 Total goodwill and other intangible assets $ 12,833 $ 12,839 Accrued Expenses and Other Current Liabilities June 30, December 31, (In thousands) Payroll, incentives and commissions payable $ 5,614 $ 8,400 Warranty reserve 809 760 Other accrued expenses and current liabilities 1,974 2,656 Total accrued expenses and other current liabilities $ 8,397 $ 11,816

Investments and Fair Value Meas

Investments and Fair Value Measurements	6 Months Ended
	Jun. 30, 2021
Investments, Fair Value Disclosure [Abstract]
Investments and Fair Value Measurements	Investments and Fair Value Measurements Available-for-Sale Investments The Company’s investments in investment-grade short-term high-quality marketable debt instruments, such as U.S. treasury securities, and corporate notes and bonds, are classified as available-for-sale. As of June 30, 2021 and December 31, 2020, available-for-sale investments were classified on the Condensed Consolidated Balance Sheet as short-term investments. The classification of available-for-sale investments on the Condensed Consolidated Balance Sheet and definition of each of these classifications are provided in Note 1, “Description of Business and Significant Accounting Policies - Significant Accounting Policies,” subsections “Cash and Cash Equivalents” and “Short-term and Long-term Investments,” of the Notes to Consolidated Financial Statements included in Item 8, “Financial Statements and Supplementary Data,” in the 2020 Annual Report. Expected maturities can differ from contractual maturities because borrowers may have the right to prepay obligations without prepayment penalties. 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 contractual maturity. All of the Company’s financial assets and liabilities are remeasured and reported at fair value at each reporting period; and are classified and disclosed in one of the following three pricing category 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, thereby requiring an entity to develop its own assumptions that market participants would use in pricing. The following table presents the Company’s financial assets measured on a recurring basis by contractual maturity, including their pricing category, amortized cost, gross unrealized holding gains and losses, and fair value. June 30, 2021 December 31, 2020 Pricing Category Amortized Gross Gross Fair Amortized Gross Gross Fair (In thousands) Cash equivalents Money market securities Level 1 $ 62,224 $ — $ — $ 62,224 $ 59,132 $ — $ — $ 59,132 Total cash equivalents 62,224 — — 62,224 59,132 — — 59,132 Short-term investments U.S. treasury securities Level 2 — — — — 1,614 7 — 1,621 Corporate notes and bonds Level 2 17,387 21 (14) 17,394 18,708 117 — 18,825 Total short-term investments 17,387 21 (14) 17,394 20,322 124 — 20,446 Total $ 79,611 $ 21 $ (14) $ 79,618 $ 79,454 $ 124 $ — $ 79,578 As of June 30, 2021 and December 31, 2020, the Company had no financial liabilities and no Level 3 financial assets. During the six months ended June 30, 2021, the Company had no transfers of financial assets between any levels. June 30, 2021 December 31, 2020 Fair Gross Fair Gross (In thousands) Corporate notes and bonds $ 13,246 $ (14) $ — $ — Sales of Available-for-Sale Investments The following table presents the sales of available-for-sale investments. Three Months Ended June 30, Six Months Ended June 30, 2021 2020 2021 2020 (In thousands) Corporate notes and bonds $ — $ 4,793 $ — $ 9,767 Realized gains on sales of securities were immaterial during the three and six months ended June 30, 2020.

Lines of Credit

Lines of Credit	6 Months Ended
	Jun. 30, 2021
Debt Disclosure [Abstract]
Lines of Credit	Lines of Credit Stand-By Letters of Credit The Company entered into a loan and pledge agreement with a financial institution during January 2017, which has been amended multiple times to accommodate the growth of the Company (the original loan and pledge agreement and its subsequent amendments are hereinafter referred to as the “Loan and Pledge Agreement”). 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 an aggregate amount of $5.1 million. SBLCs have a term limit of three years, are secured by pledged U.S. investments, and do not have any cash collateral balance requirements. 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 June 30, 2021 and December 31, 2020, there were outstanding SBLCs of $12.2 million and $13.3 million, respectively.

Commitments and Contingencies

Commitments and Contingencies	6 Months Ended
	Jun. 30, 2021
Commitments and Contingencies Disclosure [Abstract]
Commitments and Contingencies	Commitments and Contingencies Operating Lease Obligations The following table presents a summary of operating lease, right of use assets and lease liabilities. June 30, December 31, (In thousands) Operating lease, right of use asset $ 15,383 $ 16,090 Lease liabilities, current $ 1,473 $ 1,243 Lease liabilities, non-current 15,682 16,443 Total lease liability $ 17,155 $ 17,686 The following table presents operating lease activities related to all leased properties. Three Months Ended June 30, Six Months Ended June 30, 2021 2020 2021 2020 (In thousands) Operating lease expense $ 642 $ 668 $ 1,285 $ 1,271 Cash payments 647 618 1,136 1,108 Non-cash lease liabilities arising from obtaining right-of-use assets — — — 6,384 The following table presents other information related to outstanding operating leases as of June 30, 2021. Weighted average remaining lease term 7.9 years Weighted average discount rate 7.0% The following table presents the minimum lease payments under noncancelable operating leases, exclusive of executory costs as of June 30, 2021. Lease Amounts (In thousands) Future minimum lease payments by year 2021 (remaining six months) $ 1,295 2022 2,650 2023 2,580 2024 2,812 2025 2,736 2026 and thereafter 10,461 Total future minimum lease payments 22,534 Less imputed lease interest (5,379) Total lease liabilities $ 17,155 Warranty The following table presents the changes in the Company’s accrued product warranty reserve. Three Months Ended June 30, Six Months Ended June 30, 2021 2020 2021 2020 (In thousands) Warranty reserve balance, beginning of period $ 811 $ 665 $ 760 $ 631 Warranty costs charged to cost of revenue 81 75 208 173 Utilization charges against reserve (13) (1) (13) (2) Release of accrual related to expired warranties (70) (66) (146) (129) Warranty reserve balance, end of period $ 809 $ 673 $ 809 $ 673 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 June 30, 2021. 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 component parts, as well as capital equipment. As of June 30, 2021, the Company had approximately $6.7 million of such open cancellable purchase order arrangements. Litigation The Company is named in and subject to various proceedings and claims in connection with its business. 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 effect on the Company’s results of operations in any future period, and a significant judgment could have a material impact on the Company’s financial condition, results of operations and cash flows. The Company may in the future become involved in additional litigation in the ordinary course of 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 are adjusted to reflect the impacts of negotiations, settlements, rulings, advice of legal counsel and other information and events pertaining to a particular case. As of June 30, 2021, there were no material losses which were probable or reasonably possible.

Income Taxes

Income Taxes	6 Months Ended
	Jun. 30, 2021
Income Tax Disclosure [Abstract]
Income Taxes	Income Taxes Three Months Ended June 30, Six Months Ended June 30, 2021 2020 2021 2020 (In thousands, except percentages) (Benefit from) provision for income taxes $ (743) $ 4,586 $ (1,383) $ 4,501 Discrete items 728 (272) 2,355 (82) Provision for (benefit from) income taxes, excluding discrete items $ (15) $ 4,314 $ 972 $ 4,419 Effective tax rate (227.9 %) 21.3 % (21.1 %) 20.4 % Effective tax rate, excluding discrete items (5.1 %) 20.1 % 14.8 % 20.0 % The Company’s tax provision for interim periods is determined using an estimate of its annual effective tax rate, adjusted for discrete items, if any, that arise during the period. Each quarter, the Company updates its estimate of the annual effective tax rate, and if the estimated annual effective tax rate changes, the Company makes a cumulative adjustment in such period. The Company’s quarterly tax provision and estimate of its annual effective tax rate are subject to variation due to several factors, including variability in accurately predicting its pre-tax income or loss and the mix of jurisdictions to which they relate, intercompany transactions, the applicability of special tax regimes, and changes in how the Company does business.

Stockholders' Equity

Stockholders' Equity	6 Months Ended
	Jun. 30, 2021
Stockholders' Equity Note [Abstract]
Stockholders' Equity	Stockholders’ Equity Stock Repurchase Program On March 9, 2021, the Board of Directors authorized a stock repurchase program under which the Company may repurchase, at the discretion of management, up to $50.0 million in aggregate cost of the Company’s outstanding common stock (the “March 2021 Authorization”). Under the March 2021 Authorization, purchases of shares of common stock may be made 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 2021 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. The Company accounts for stock repurchases using the cost method. The aggregate cost includes fees charged in connection with acquiring the shares. As of June 30, 2021, 656,938 shares at an aggregate cost of $11.6 million had been repurchased under the March 2021 Authorization.

Segment Reporting

Segment Reporting	6 Months Ended
	Jun. 30, 2021
Segment Reporting [Abstract]
Segment Reporting	Segment ReportingThe Company’s chief operating decision-maker (“CODM”) is its chief executive officer. The Company continues to monitor and review its segment reporting structure in accordance with authoritative guidance to determine whether any changes have occurred that would impact its reportable segments. As a result of the evolution of the Company’s products, operations and research and development (“R&D”) efforts in new product development, and the way in which the CODM manages and assesses the performance of the business, starting in the first quarter of fiscal year 2021, the Company realigned its segment reporting and has recast the prior year amounts for comparability. In addition, to better align the activities of the segments, the Company has re-allocated certain corporate resources to the segments’ operations. Income and type of expense activities that are included in the Water and Emerging Technologies segments and corporate operating expenses are as follows: Water segment: The continued development, sales and support of the PX, hydraulic turbochargers and pumps used in our seawater desalination and industrial wastewater activities. Emerging Technologies segment: The continued development, sales and support of activities related to emerging technologies, such as the VorTeq used in the oil and gas market, the ISOBoost used in natural gas processing, the PX G1300 used in industrial and commercial refrigeration applications, and certain other new products. Corporate operating expenses: Corporate activities outside of the operating segments, such as audit and accounting expenses, general legal costs, board of director fees and expenses, and other separately managed general expenses not related to the identified segments. Segment Financial Information For each of the periods presented in the following tables, operating income (loss) for each segment excludes other income and expenses, and corporate operating expenses not included in how the CODM assesses the performance of the operating segments, such as income taxes and other separately managed general and administrative expenses not attributed to the operating segments. Assets and liabilities are reviewed at the consolidated level by the CODM and are not attributed to the segments. The CODM allocates resources to, and assesses the performance of, each operating segment using information about its revenue and operating income. Three Months Ended June 30, 2021 Six Months Ended June 30, 2021 Water Emerging Technologies Total Water Emerging Technologies Total (In thousands) Product revenue $ 20,568 $ 39 $ 20,607 $ 49,508 $ 39 $ 49,547 Product cost of revenue 7,181 — 7,181 16,162 — 16,162 Product gross profit 13,387 39 13,426 33,346 39 33,385 Operating expenses General and administrative 1,776 1,315 3,091 3,333 2,481 5,814 Sales and marketing 2,121 229 2,350 4,285 408 4,693 Research and development 595 3,829 4,424 1,096 7,830 8,926 Amortization of intangible assets 3 — 3 7 — 7 Total operating expenses 4,495 5,373 9,868 8,721 10,719 19,440 Operating income (loss) $ 8,892 $ (5,334) 3,558 $ 24,625 $ (10,680) 13,945 Less: Corporate operating expenses 3,271 7,514 Income from operations 287 6,431 Other income, net 39 121 Income before income taxes $ 326 $ 6,552 Three Months Ended June 30, 2020 (Recast) Six Months Ended June 30, 2020 (Recast) Water Emerging Technologies Total Water Emerging Technologies Total (In thousands) Product revenue $ 19,256 $ — $ 19,256 $ 38,257 $ — $ 38,257 Product cost of revenue 6,549 — 6,549 12,233 — 12,233 Product gross profit 12,707 — 12,707 26,024 — 26,024 License and development revenue (1) — 24,352 24,352 — 26,895 26,895 Operating expenses General and administrative 1,967 1,150 3,117 4,046 2,642 6,688 Sales and marketing 1,124 262 1,386 2,800 574 3,374 Research and development 960 5,392 6,352 1,862 11,199 13,061 Amortization of intangible assets 4 — 4 8 — 8 Impairment of long-lived assets — 2,332 2,332 — 2,332 2,332 Total operating expenses 4,055 9,136 13,191 8,716 16,747 25,463 Operating income $ 8,652 $ 15,216 23,868 $ 17,308 $ 10,148 27,456 Less: Corporate operating expenses 2,593 6,053 Income from operations 21,275 21,403 Other income, net 237 645 Income before income taxes $ 21,512 $ 22,048 (1) In June 2020, the Company and Schlumberger entered into an agreement to terminate the VorTeq License Agreement. The termination of the VorTeq License Agreement was effective June 1, 2020. As there were no future performance obligations to be recognized under the VorTeq License Agreement after the effective date, the Company recognized in full the remaining deferred revenue balance of $24.4 million in the second quarter of fiscal year 2020. In addition, no future license and development revenue was recognized under the VorTeq License Agreement after the second quarter of fiscal year 2020.

Concentrations

Concentrations	6 Months Ended
	Jun. 30, 2021
Risks and Uncertainties [Abstract]
Concentrations	Concentrations Product Revenue The following table presents customers accounting for 10% or more of product revenue by segment. Although certain customers might account for greater than 10% of product revenue at any one point in time, the concentration of product revenue between a limited number of customers shifts regularly, depending on contract negotiations. The percentages by customer reflect specific relationships or contracts that would concentrate product revenue for the periods presented and does not indicate a trend specific to any one customer. Three Months Ended June 30, Six Months Ended June 30, Segment 2021 2020 2021 2020 Customer A Water 30% 22% 22% 15% Customer B Water 22% 19% 19% 24% Customer C Water ** ** 12% ** Customer D Water ** 22% 11% 21% ** Zero or less than 10%.

Description of Business and S_2

Description of Business and Significant Accounting Policies (Policies)	6 Months Ended
	Jun. 30, 2021
Accounting Policies [Abstract]
Basis of Presentation	Basis of Presentation The Condensed Consolidated Financial Statements include the accounts of Energy Recovery, Inc. and its wholly-owned subsidiaries. All intercompany accounts and transactions have been eliminated in consolidation. The accompanying Condensed Consolidated Financial Statements have been prepared pursuant to the rules and regulations of the Securities and Exchange Commission (the “SEC”). Certain information and footnote disclosures normally included in the financial statements prepared in accordance with U.S. generally accepted accounting principles (“GAAP”) have been condensed or omitted pursuant to such rules and regulations. The December 31, 2020 Condensed Consolidated Balance Sheet was derived from audited financial statements and may not include all disclosures required by GAAP; however, the Company believes that the disclosures are adequate to make the information presented not misleading. The June 30, 2021 unaudited Condensed Consolidated Financial Statements should be read in conjunction with the audited Consolidated Financial Statements and the notes thereto for the fiscal year ended December 31, 2020 included in the Company’s Annual Report on Form 10-K filed with the SEC on March 12, 2021 (the “2020 Annual Report”). All adjustments consisting of normal recurring adjustments that are necessary to present fairly the financial position, results of operations and cash flows for the interim periods have been made. The results of operations for the interim periods are not necessarily indicative of the operating results for the full fiscal year or any future periods.
Reclassifications	Reclassifications Certain prior period amounts have been reclassified in the Condensed Consolidated Balance Sheets, Condensed Consolidated Statements of Cash Flows, and certain notes to the Condensed Consolidated Financial Statements, to conform to the current period presentation.
Use of Estimates	Use of Estimates The preparation of Condensed Consolidated Financial Statements, in conformity with GAAP, requires the Company’s management to make judgments, assumptions and estimates that affect the amounts reported in the Condensed 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; valuation of stock options; valuation and impairment of goodwill; 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.
Recently Adopted Accounting Pronouncements and Recently Issued Accounting Pronouncements Not Yet Adopted	Recently Adopted Accounting Pronouncements In December 2019, the Financial Accounting Standards Board (“FASB”) issued Accounting Standards Update (“ASU”) No. 2019-12, Income Taxes (Topic 740): Simplifying the Accounting for Income Taxes (“ASU 2019-12”), which simplifies the accounting for income taxes by removing certain exceptions to the general principles in Topic 740 and also clarifies and amends existing guidance to improve consistent application. The new standard is effective for interim and annual periods beginning after December 15, 2020. The Company adopted ASU 2019-12 on January 1, 2021. The adoption of ASU 2019-12 did not have a material impact on the Company’s consolidated financial condition, results of operations, and cash flows. In March 2020, the FASB issued ASU No. 2020-04, Reference Rate Reform (Topic 848) (“ASU 2020-04”), which provided optional expedients and exceptions for applying GAAP to contracts, hedging relationships, and other transactions affected by the discontinuation of the London Interbank Offered Rate (“LIBOR”) or by another reference rate expected to be discontinued. The FASB later issued ASU No. 2021-01, Reference Rate Reform (Topic 848): Scope, to clarify the scope of Topic 848 so that derivatives affected by the discounting transition are explicitly eligible for certain optional expedients and exceptions in Topic 848 (“ASU 2021-01”). Entities may apply the provisions of the new standards as of the beginning of the reporting period when the election is made (i.e., as early as the first quarter of 2020). Unlike other topics, the provisions of this update are only available until December 31, 2022, when the reference rate replacement activity is expected to have been completed. An entity may elect to apply amendments prospectively through December 31, 2022. The optional expedients were available to be used upon issuance of this guidance but the Company has not yet applied the guidance because the Company has not yet modified its existing contract for reference rate reform. The Company does not expect the provisions of ASU 2020-04 or ASU 2021-01 to have a material impact on its financial condition, results of operation, and cash flows.
Income Taxes	The Company’s tax provision for interim periods is determined using an estimate of its annual effective tax rate, adjusted for discrete items, if any, that arise during the period. Each quarter, the Company updates its estimate of the annual effective tax rate, and if the estimated annual effective tax rate changes, the Company makes a cumulative adjustment in such period. The Company’s quarterly tax provision and estimate of its annual effective tax rate are subject to variation due to several factors, including variability in accurately predicting its pre-tax income or loss and the mix of jurisdictions to which they relate, intercompany transactions, the applicability of special tax regimes, and changes in how the Company does business.
Litigation	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 are adjusted to reflect the impacts of negotiations, settlements, rulings, advice of legal counsel and other information and events pertaining to a particular case.

Revenue (Tables)

Revenue (Tables)	6 Months Ended
	Jun. 30, 2021
Revenue from Contract with Customer [Abstract]
Disaggregation of Revenue	Three Months Ended June 30, 2021 Six Months Ended June 30, 2021 Water Emerging Technologies Total Water Emerging Technologies Total (In thousands) Revenue by product and service line PXs, pumps and turbo devices, and other $ 20,568 $ 39 $ 20,607 $ 49,508 $ 39 $ 49,547 Revenue by primary geographical markets Middle East and Africa $ 16,401 $ 39 $ 16,440 $ 37,361 $ 39 $ 37,400 Asia 2,325 — 2,325 9,503 — 9,503 Americas 945 — 945 1,368 — 1,368 Europe 897 — 897 1,276 — 1,276 Total revenue $ 20,568 $ 39 $ 20,607 $ 49,508 $ 39 $ 49,547 Product revenue by channel Megaproject $ 13,236 $ 39 $ 13,275 $ 36,993 $ 39 $ 37,032 Original equipment manufacturer 4,274 — 4,274 7,065 — 7,065 Aftermarket 3,058 — 3,058 5,450 — 5,450 Total product revenue $ 20,568 $ 39 $ 20,607 $ 49,508 $ 39 $ 49,547 Three Months Ended June 30, 2020 Six Months Ended June 30, 2020 Water Emerging Technologies Total Water Emerging Technologies Total (In thousands) Revenue by product and service line PXs, pumps and turbo devices, and other $ 19,256 $ — $ 19,256 $ 38,257 $ — $ 38,257 License and development — 24,352 24,352 — 26,895 26,895 Total revenue $ 19,256 $ 24,352 $ 43,608 $ 38,257 $ 26,895 $ 65,152 Revenue by primary geographical markets Middle East and Africa $ 16,504 $ — $ 16,504 $ 32,735 $ — $ 32,735 Asia 617 — 617 1,392 — 1,392 Americas 1,161 24,352 25,513 2,362 26,895 29,257 Europe 974 — 974 1,768 — 1,768 Total product revenue $ 19,256 $ 24,352 $ 43,608 $ 38,257 $ 26,895 $ 65,152 Product revenue by channel Megaproject $ 11,965 $ — $ 11,965 $ 26,422 $ — $ 26,422 Original equipment manufacturer 4,050 — 4,050 7,606 — 7,606 Aftermarket 3,241 — 3,241 4,229 — 4,229 Total product revenue $ 19,256 $ — $ 19,256 $ 38,257 $ — $ 38,257
Contract with Customer, Asset and Liability	The following table presents contract balances by category. June 30, December 31, (In thousands) Accounts receivable, net $ 7,599 $ 11,792 Contract assets: Contract assets, current (included in prepaid expenses and other assets, current) $ 536 $ 1,309 Contract assets, non-current (included in other assets, non-current) — 583 Total contract assets $ 536 $ 1,892 Contract liabilities: Contract liabilities, current $ 1,117 $ 1,552 Contract liabilities, non-current (included in other liabilities, non-current) 89 88 Total contract liabilities $ 1,206 $ 1,640
Contract With Customer, Contract Liability, Activity	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. June 30, December 31, (In thousands) Contract liabilities balance, beginning of year $ 1,640 $ 28,866 Revenue recognized (1,232) (28,414) Cash received, excluding amounts recognized as revenue during the period 798 1,188 Contract liabilities balance, end of period $ 1,206 $ 1,640
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. June 30, (In thousands) Future performance obligations by year 2021 (remaining six months) $ 4,036 2022 12,191 Total future performance obligations $ 16,227

Net Income Per Share - (Tables)

Net Income Per Share - (Tables)	6 Months Ended
	Jun. 30, 2021
Earnings Per Share [Abstract]
Schedule of Earnings Per Share, Basic and Diluted	The following table presents the computation of basic and diluted net income per share. Three Months Ended June 30, Six Months Ended June 30, 2021 2020 2021 2020 (In thousands, except per share amounts) Numerator Net income $ 1,069 $ 16,926 $ 7,935 $ 17,547 Denominator (weighted average shares) Basic common shares outstanding 57,253 55,614 57,066 55,513 Dilutive stock awards 1,746 757 1,756 925 Diluted common shares outstanding 58,999 56,371 58,822 56,438 Net income per share Basic $ 0.02 $ 0.30 $ 0.14 $ 0.32 Diluted $ 0.02 $ 0.30 $ 0.13 $ 0.31
Schedule of Antidilutive Securities Excluded from Computation of Earnings Per Share	The following table presents the weighted potential common shares issuable under stock awards that were excluded from the computation of diluted net income per share. Three Months Ended June 30, Six Months Ended June 30, 2021 2020 2021 2020 (In thousands) Anti-dilutive stock awards 6 2,893 457 1,989

Other Financial Information (Ta

Other Financial Information (Tables)	6 Months Ended
	Jun. 30, 2021
Other Financial Information [Abstract]
Restrictions on Cash and Cash Equivalents	The Condensed Consolidated Statements of Cash Flows explain the changes in the total of cash, cash equivalents and restricted cash. The following table presents a reconciliation of cash, cash equivalents and restricted cash (1) reported within the Condensed Consolidated Balance Sheets that sum to the total of such amounts presented. June 30, December 31, June 30, (In thousands) Cash and cash equivalents $ 103,302 $ 94,255 $ 62,970 Restricted cash, non-current (included in other assets, non-current) 103 103 102 Total cash, cash equivalents and restricted cash $ 103,405 $ 94,358 $ 63,072 (1) The Company pledged and deposited cash amounts into restricted cash accounts in connection with the Company’s credit cards.
Schedule of Accounts, Notes, Loans and Financing Receivable	The following table presents the components of accounts receivable, net. June 30, December 31, (In thousands) Accounts receivable, gross $ 7,716 $ 12,189 Allowance for doubtful accounts (1) (117) (397) Accounts receivable, net $ 7,599 $ 11,792 (1) The Company wrote-off $0.3 million of uncollectible receivables, which had been previously reserved as of December 31, 2020, during the second quarter of 2021.
Schedule of Inventory, Current	The following table presents inventory by category. June 30, December 31, (In thousands) Raw materials $ 5,161 $ 4,260 Work in process 2,740 2,360 Finished goods 7,388 5,128 Inventories, net $ 15,289 $ 11,748
Schedule Of Prepaid And Other Current Assets	Prepaid and Other Current Assets June 30, December 31, (In thousands) Contract assets, current $ 536 $ 1,309 Cloud computing arrangement implementation costs 1,095 1,087 Other prepaid expenses and current assets 2,634 2,554 Total prepaid and other current assets $ 4,265 $ 4,950
Schedule of Intangible Assets and Goodwill	June 30, December 31, (In thousands) Goodwill $ 12,790 $ 12,790 Other intangible assets 43 49 Total goodwill and other intangible assets $ 12,833 $ 12,839
Schedule of Accrued Liabilities	Accrued Expenses and Other Current Liabilities June 30, December 31, (In thousands) Payroll, incentives and commissions payable $ 5,614 $ 8,400 Warranty reserve 809 760 Other accrued expenses and current liabilities 1,974 2,656 Total accrued expenses and other current liabilities $ 8,397 $ 11,816

Investments and Fair Value Me_2

Investments and Fair Value Measurements (Tables)	6 Months Ended
	Jun. 30, 2021
Investments, Fair Value Disclosure [Abstract]
Schedule of Amortized Cost and Fair Value of Available for Sale Securities	The following table presents the Company’s financial assets measured on a recurring basis by contractual maturity, including their pricing category, amortized cost, gross unrealized holding gains and losses, and fair value. June 30, 2021 December 31, 2020 Pricing Category Amortized Gross Gross Fair Amortized Gross Gross Fair (In thousands) Cash equivalents Money market securities Level 1 $ 62,224 $ — $ — $ 62,224 $ 59,132 $ — $ — $ 59,132 Total cash equivalents 62,224 — — 62,224 59,132 — — 59,132 Short-term investments U.S. treasury securities Level 2 — — — — 1,614 7 — 1,621 Corporate notes and bonds Level 2 17,387 21 (14) 17,394 18,708 117 — 18,825 Total short-term investments 17,387 21 (14) 17,394 20,322 124 — 20,446 Total $ 79,611 $ 21 $ (14) $ 79,618 $ 79,454 $ 124 $ — $ 79,578
Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value	The following table presents a summary of the fair value and gross unrealized holding losses on the available-for-sale securities that have been in a continuous unrealized loss position, aggregated by type of investment instrument. The available-for-sale securities that were in an unrealized gain position have been excluded from the table. June 30, 2021 December 31, 2020 Fair Gross Fair Gross (In thousands) Corporate notes and bonds $ 13,246 $ (14) $ — $ —
Debt Securities, Available-for-Sale, Proceeds From Sale	The following table presents the sales of available-for-sale investments. Three Months Ended June 30, Six Months Ended June 30, 2021 2020 2021 2020 (In thousands) Corporate notes and bonds $ — $ 4,793 $ — $ 9,767

Commitments and Contingencies (

Commitments and Contingencies (Tables)	6 Months Ended
	Jun. 30, 2021
Commitments and Contingencies Disclosure [Abstract]
Schedule of Summary of Operating Lease, Right of Use Assets and Lease Liabilities	The following table presents a summary of operating lease, right of use assets and lease liabilities. June 30, December 31, (In thousands) Operating lease, right of use asset $ 15,383 $ 16,090 Lease liabilities, current $ 1,473 $ 1,243 Lease liabilities, non-current 15,682 16,443 Total lease liability $ 17,155 $ 17,686
Lease, Cost	The following table presents operating lease activities related to all leased properties. Three Months Ended June 30, Six Months Ended June 30, 2021 2020 2021 2020 (In thousands) Operating lease expense $ 642 $ 668 $ 1,285 $ 1,271 Cash payments 647 618 1,136 1,108 Non-cash lease liabilities arising from obtaining right-of-use assets — — — 6,384
Lease, Term And Discount Rate	The following table presents other information related to outstanding operating leases as of June 30, 2021. Weighted average remaining lease term 7.9 years Weighted average discount rate 7.0%
Lessee, Operating Lease, Liability, Maturity	The following table presents the minimum lease payments under noncancelable operating leases, exclusive of executory costs as of June 30, 2021. Lease Amounts (In thousands) Future minimum lease payments by year 2021 (remaining six months) $ 1,295 2022 2,650 2023 2,580 2024 2,812 2025 2,736 2026 and thereafter 10,461 Total future minimum lease payments 22,534 Less imputed lease interest (5,379) Total lease liabilities $ 17,155
Schedule of Product Warranty Liability	The following table presents the changes in the Company’s accrued product warranty reserve. Three Months Ended June 30, Six Months Ended June 30, 2021 2020 2021 2020 (In thousands) Warranty reserve balance, beginning of period $ 811 $ 665 $ 760 $ 631 Warranty costs charged to cost of revenue 81 75 208 173 Utilization charges against reserve (13) (1) (13) (2) Release of accrual related to expired warranties (70) (66) (146) (129) Warranty reserve balance, end of period $ 809 $ 673 $ 809 $ 673

Income Taxes (Tables)

Income Taxes (Tables)	6 Months Ended
	Jun. 30, 2021
Income Tax Disclosure [Abstract]
Schedule of Components of Income Tax Expense (Benefit)	Three Months Ended June 30, Six Months Ended June 30, 2021 2020 2021 2020 (In thousands, except percentages) (Benefit from) provision for income taxes $ (743) $ 4,586 $ (1,383) $ 4,501 Discrete items 728 (272) 2,355 (82) Provision for (benefit from) income taxes, excluding discrete items $ (15) $ 4,314 $ 972 $ 4,419 Effective tax rate (227.9 %) 21.3 % (21.1 %) 20.4 % Effective tax rate, excluding discrete items (5.1 %) 20.1 % 14.8 % 20.0 %

Segment Reporting (Tables)

Segment Reporting (Tables)	6 Months Ended
	Jun. 30, 2021
Segment Reporting [Abstract]
Reconciliation of Operating Profit (Loss) from Segments to Consolidated	Three Months Ended June 30, 2021 Six Months Ended June 30, 2021 Water Emerging Technologies Total Water Emerging Technologies Total (In thousands) Product revenue $ 20,568 $ 39 $ 20,607 $ 49,508 $ 39 $ 49,547 Product cost of revenue 7,181 — 7,181 16,162 — 16,162 Product gross profit 13,387 39 13,426 33,346 39 33,385 Operating expenses General and administrative 1,776 1,315 3,091 3,333 2,481 5,814 Sales and marketing 2,121 229 2,350 4,285 408 4,693 Research and development 595 3,829 4,424 1,096 7,830 8,926 Amortization of intangible assets 3 — 3 7 — 7 Total operating expenses 4,495 5,373 9,868 8,721 10,719 19,440 Operating income (loss) $ 8,892 $ (5,334) 3,558 $ 24,625 $ (10,680) 13,945 Less: Corporate operating expenses 3,271 7,514 Income from operations 287 6,431 Other income, net 39 121 Income before income taxes $ 326 $ 6,552 Three Months Ended June 30, 2020 (Recast) Six Months Ended June 30, 2020 (Recast) Water Emerging Technologies Total Water Emerging Technologies Total (In thousands) Product revenue $ 19,256 $ — $ 19,256 $ 38,257 $ — $ 38,257 Product cost of revenue 6,549 — 6,549 12,233 — 12,233 Product gross profit 12,707 — 12,707 26,024 — 26,024 License and development revenue (1) — 24,352 24,352 — 26,895 26,895 Operating expenses General and administrative 1,967 1,150 3,117 4,046 2,642 6,688 Sales and marketing 1,124 262 1,386 2,800 574 3,374 Research and development 960 5,392 6,352 1,862 11,199 13,061 Amortization of intangible assets 4 — 4 8 — 8 Impairment of long-lived assets — 2,332 2,332 — 2,332 2,332 Total operating expenses 4,055 9,136 13,191 8,716 16,747 25,463 Operating income $ 8,652 $ 15,216 23,868 $ 17,308 $ 10,148 27,456 Less: Corporate operating expenses 2,593 6,053 Income from operations 21,275 21,403 Other income, net 237 645 Income before income taxes $ 21,512 $ 22,048 (1) In June 2020, the Company and Schlumberger entered into an agreement to terminate the VorTeq License Agreement. The termination of the VorTeq License Agreement was effective June 1, 2020. As there were no future performance obligations to be recognized under the VorTeq License Agreement after the effective date, the Company recognized in full the remaining deferred revenue balance of $24.4 million in the second quarter of fiscal year 2020. In addition, no future license and development revenue was recognized under the VorTeq License Agreement after the second quarter of fiscal year 2020.

Concentrations (Tables)

Concentrations (Tables)	6 Months Ended
	Jun. 30, 2021
Risks and Uncertainties [Abstract]
Schedules of Concentration of Risk, by Risk Factor	The following table presents customers accounting for 10% or more of product revenue by segment. Although certain customers might account for greater than 10% of product revenue at any one point in time, the concentration of product revenue between a limited number of customers shifts regularly, depending on contract negotiations. The percentages by customer reflect specific relationships or contracts that would concentrate product revenue for the periods presented and does not indicate a trend specific to any one customer. Three Months Ended June 30, Six Months Ended June 30, Segment 2021 2020 2021 2020 Customer A Water 30% 22% 22% 15% Customer B Water 22% 19% 19% 24% Customer C Water ** ** 12% ** Customer D Water ** 22% 11% 21% ** Zero or less than 10%.

Revenue - Disaggregation of Rev

Revenue - Disaggregation of Revenue (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020
Disaggregation of Revenue [Line Items]
Revenue	$ 20,607	$ 43,608	$ 49,547	$ 65,152
Water
Disaggregation of Revenue [Line Items]
Revenue	20,568	19,256	49,508	38,257
Emerging Technologies
Disaggregation of Revenue [Line Items]
Revenue	39	24,352	39	26,895
PX Pressure Exchangers, pumps and turbo devices, and other
Disaggregation of Revenue [Line Items]
Revenue	20,607	19,256	49,547	38,257
PX Pressure Exchangers, pumps and turbo devices, and other | Water
Disaggregation of Revenue [Line Items]
Revenue	20,568	19,256	49,508	38,257
PX Pressure Exchangers, pumps and turbo devices, and other | Emerging Technologies
Disaggregation of Revenue [Line Items]
Revenue	39	0	39	0
PX Pressure Exchangers, pumps and turbo devices, and other | Megaproject
Disaggregation of Revenue [Line Items]
Revenue	13,275	11,965	37,032	26,422
PX Pressure Exchangers, pumps and turbo devices, and other | Megaproject | Water
Disaggregation of Revenue [Line Items]
Revenue	13,236	11,965	36,993	26,422
PX Pressure Exchangers, pumps and turbo devices, and other | Megaproject | Emerging Technologies
Disaggregation of Revenue [Line Items]
Revenue	39	0	39	0
PX Pressure Exchangers, pumps and turbo devices, and other | Original equipment manufacturer
Disaggregation of Revenue [Line Items]
Revenue	4,274	4,050	7,065	7,606
PX Pressure Exchangers, pumps and turbo devices, and other | Original equipment manufacturer | Water
Disaggregation of Revenue [Line Items]
Revenue	4,274	4,050	7,065	7,606
PX Pressure Exchangers, pumps and turbo devices, and other | Original equipment manufacturer | Emerging Technologies
Disaggregation of Revenue [Line Items]
Revenue	0	0	0	0
PX Pressure Exchangers, pumps and turbo devices, and other | Aftermarket
Disaggregation of Revenue [Line Items]
Revenue	3,058	3,241	5,450	4,229
PX Pressure Exchangers, pumps and turbo devices, and other | Aftermarket | Water
Disaggregation of Revenue [Line Items]
Revenue	3,058	3,241	5,450	4,229
PX Pressure Exchangers, pumps and turbo devices, and other | Aftermarket | Emerging Technologies
Disaggregation of Revenue [Line Items]
Revenue	0	0	0	0
License and development
Disaggregation of Revenue [Line Items]
Revenue	0	24,352	0	26,895
License and development | Water
Disaggregation of Revenue [Line Items]
Revenue		0		0
License and development | Emerging Technologies
Disaggregation of Revenue [Line Items]
Revenue		24,352		26,895
Middle East and Africa
Disaggregation of Revenue [Line Items]
Revenue	16,440	16,504	37,400	32,735
Middle East and Africa | Water
Disaggregation of Revenue [Line Items]
Revenue	16,401	16,504	37,361	32,735
Middle East and Africa | Emerging Technologies
Disaggregation of Revenue [Line Items]
Revenue	39	0	39	0
Asia
Disaggregation of Revenue [Line Items]
Revenue	2,325	617	9,503	1,392
Asia | Water
Disaggregation of Revenue [Line Items]
Revenue	2,325	617	9,503	1,392
Asia | Emerging Technologies
Disaggregation of Revenue [Line Items]
Revenue	0	0	0	0
Americas
Disaggregation of Revenue [Line Items]
Revenue	945	25,513	1,368	29,257
Americas | Water
Disaggregation of Revenue [Line Items]
Revenue	945	1,161	1,368	2,362
Americas | Emerging Technologies
Disaggregation of Revenue [Line Items]
Revenue	0	24,352	0	26,895
Europe
Disaggregation of Revenue [Line Items]
Revenue	897	974	1,276	1,768
Europe | Water
Disaggregation of Revenue [Line Items]
Revenue	897	974	1,276	1,768
Europe | Emerging Technologies
Disaggregation of Revenue [Line Items]
Revenue	$ 0	$ 0	$ 0	$ 0

Revenue - Schlumberger Technolo

Revenue - Schlumberger Technology Corporation - Narrative (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020
Revenue from External Customer [Line Items]
Revenue	$ 20,607	$ 43,608	$ 49,547	$ 65,152
License and development
Revenue from External Customer [Line Items]
Revenue	$ 0	24,352	$ 0	$ 26,895
VorTeq License Agreement | Affiliated Entity | License and development | Schlumberger Technology Corporation | Emerging Tech
Revenue from External Customer [Line Items]
Revenue		$ 24,400

Revenue - Contract Assets and L

Revenue - Contract Assets and Liabilities (Details) - USD ($) $ in Thousands	Jun. 30, 2021	Dec. 31, 2020	Dec. 31, 2019
Revenue from Contract with Customer [Abstract]
Accounts receivable, net	$ 7,599	$ 11,792
Contract assets:
Contract assets, current (included in prepaid expenses and other assets, current)	536	1,309
Contract assets, non-current (included in other assets, non-current)	0	583
Total contract assets	536	1,892
Contract liabilities:
Contract liabilities, current	1,117	1,552
Contract liabilities, non-current	89	88
Total contract liabilities	$ 1,206	$ 1,640	$ 28,866

Revenue - Significant Changes i

Revenue - Significant Changes in Contract Liabilities (Details) - USD ($) $ in Thousands	6 Months Ended	12 Months Ended
	Jun. 30, 2021	Dec. 31, 2020
Revenue from Contract with Customer [Abstract]
Contract liabilities balance, beginning of year	$ 1,640	$ 28,866
Revenue recognized	(1,232)	(28,414)
Increase due to cash received, excluding amounts recognized as revenue during the period	798	1,188
Contract liabilities balance, end of period	$ 1,206	$ 1,640

Revenue - Remaining Performance

Revenue - Remaining Performance Obligation (Details) $ in Thousands	Jun. 30, 2021USD ($)
Revenue from Contract with Customer [Abstract]
Performance obligations expected to be satisfied	$ 16,227
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2021-07-01
Revenue from Contract with Customer [Abstract]
Performance obligations expected to be satisfied	$ 4,036
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Performance obligations expected to be satisfied, expected timing	6 months
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2022-01-01
Revenue from Contract with Customer [Abstract]
Performance obligations expected to be satisfied	$ 12,191
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Performance obligations expected to be satisfied, expected timing	1 year

Net Income Per Share - Computat

Net Income Per Share - Computation of Basic and Diluted Earnings Per Share (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020
Numerator
Net income	$ 1,069	$ 16,926	$ 7,935	$ 17,547
Denominator (weighted average shares)
Basic common shares outstanding (in shares)	57,253	55,614	57,066	55,513
Dilutive stock awards (in shares)	1,746	757	1,756	925
Diluted common shares outstanding (in shares)	58,999	56,371	58,822	56,438
Net income per share - Basic (in dollars per share)	$ 0.02	$ 0.30	$ 0.14	$ 0.32
Net income per share - Diluted (in dollars per share)	$ 0.02	$ 0.30	$ 0.13	$ 0.31

Net Income Per Share - Antidilu

Net Income Per Share - Antidilutive Securities Excluded From Computation of Diluted Earnings Per Share (Details) - shares shares in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020
Earnings Per Share [Abstract]
Anti-dilutive stock awards (in shares)	6	2,893	457	1,989

Other Financial Information - C

Other Financial Information - Cash, Cash Equivalents and Restricted Cash (Details) - USD ($) $ in Thousands	Jun. 30, 2021	Dec. 31, 2020	Jun. 30, 2020	Dec. 31, 2019
Other Financial Information [Abstract]
Cash and cash equivalents	$ 103,302	$ 94,255	$ 62,970
Restricted cash, non-current (included in other assets, non-current)	103	103	102
Total cash, cash equivalents and restricted cash	$ 103,405	$ 94,358	$ 63,072	$ 26,488

Other Financial Information - A

Other Financial Information - Accounts Receivable (Details) - USD ($) $ in Thousands	Jun. 30, 2021	Dec. 31, 2020
Other Financial Information [Abstract]
Accounts receivable, gross	$ 7,716	$ 12,189
Allowance for doubtful accounts	(117)	(397)
Accounts receivable, net	$ 7,599	$ 11,792

Other Financial Information - R

Other Financial Information - Reserved Amounts Write-Off (Details) $ in Millions	6 Months Ended
	Jun. 30, 2021USD ($)
Other Financial Information [Abstract]
Accounts receivable, write off	$ (0.3)

Other Financial Information - I

Other Financial Information - Inventories (Details) - USD ($) $ in Thousands	Jun. 30, 2021	Dec. 31, 2020
Other Financial Information [Abstract]
Raw materials	$ 5,161	$ 4,260
Work in process	2,740	2,360
Finished goods	7,388	5,128
Inventories, net	$ 15,289	$ 11,748

Other Financial Information -_2

Other Financial Information - Inventory Valuation Reserves - Narrative (Details) - USD ($) $ in Millions	Jun. 30, 2021	Dec. 31, 2020
Other Financial Information [Abstract]
Inventory valuation reserves	$ 0.6	$ 0.5

Other Financial Information - P

Other Financial Information - Prepaid and Other Current Assets (Details) - USD ($) $ in Thousands	Jun. 30, 2021	Dec. 31, 2020
Other Financial Information [Abstract]
Contract assets, current	$ 536	$ 1,309
Cloud computing arrangement implementation costs	1,095	1,087
Other prepaid expenses and current assets	2,634	2,554
Total prepaid and other current assets	$ 4,265	$ 4,950

Other Financial Information - G

Other Financial Information - Goodwill and Other Intangible Assets (Details) - USD ($) $ in Thousands	Jun. 30, 2021	Dec. 31, 2020
Other Financial Information [Abstract]
Goodwill	$ 12,790	$ 12,790
Other intangible assets	43	49
Goodwill and other intangible assets	$ 12,833	$ 12,839

Other Financial Information -_3

Other Financial Information - Accrued Expenses and Other Current Liabilities (Details) - USD ($) $ in Thousands	Jun. 30, 2021	Mar. 31, 2021	Dec. 31, 2020	Jun. 30, 2020	Mar. 31, 2020	Dec. 31, 2019
Other Financial Information [Abstract]
Payroll, incentives and commissions payable	$ 5,614		$ 8,400
Warranty reserve	809	$ 811	760	$ 673	$ 665	$ 631
Other accrued expenses and current liabilities	1,974		2,656
Total accrued expenses and other current liabilities	$ 8,397		$ 11,816

Investments and Fair Value Me_3

Investments and Fair Value Measurements - Financial Assets Measured on Recurring Basis (Details) - USD ($)	Jun. 30, 2021	Dec. 31, 2020
Debt Securities, Available-for-sale, Unrealized Gain (Loss) [Abstract]
Amortized Cost	$ 79,611,000	$ 79,454,000
Gross Unrealized Gains	21,000	124,000
Gross Unrealized Losses	(14,000)	0
Fair Value	79,618,000	79,578,000
Transfer between Level 1 and Level 2	0
Cash equivalents
Debt Securities, Available-for-sale, Unrealized Gain (Loss) [Abstract]
Amortized Cost	62,224,000	59,132,000
Gross Unrealized Gains	0	0
Gross Unrealized Losses	0	0
Fair Value	62,224,000	59,132,000
Short-term investments
Debt Securities, Available-for-sale, Unrealized Gain (Loss) [Abstract]
Amortized Cost	17,387,000	20,322,000
Gross Unrealized Gains	21,000	124,000
Gross Unrealized Losses	(14,000)	0
Fair Value	17,394,000	20,446,000
Level 1 | Cash equivalents | Money market securities
Debt Securities, Available-for-sale, Unrealized Gain (Loss) [Abstract]
Amortized Cost	62,224,000	59,132,000
Gross Unrealized Gains	0	0
Gross Unrealized Losses	0	0
Fair Value	62,224,000	59,132,000
Level 2 | Short-term investments | U.S. treasury securities
Debt Securities, Available-for-sale, Unrealized Gain (Loss) [Abstract]
Amortized Cost	0	1,614,000
Gross Unrealized Gains	0	7,000
Gross Unrealized Losses	0	0
Fair Value	0	1,621,000
Level 2 | Short-term investments | Corporate notes and bonds
Debt Securities, Available-for-sale, Unrealized Gain (Loss) [Abstract]
Amortized Cost	17,387,000	18,708,000
Gross Unrealized Gains	21,000	117,000
Gross Unrealized Losses	(14,000)	0
Fair Value	17,394,000	18,825,000
Measured On Recurring Basis
Debt Securities, Available-for-sale, Unrealized Gain (Loss) [Abstract]
Total fair value of financial liabilities	0	0
Measured On Recurring Basis | Level 3
Debt Securities, Available-for-sale, Unrealized Gain (Loss) [Abstract]
Total fair value of financial assets	$ 0	$ 0

Investments and Fair Value Me_4

Investments and Fair Value Measurements - Gross Unrealized Losses and Fair Values of Investments (Details) - Corporate notes and bonds - USD ($) $ in Thousands	Jun. 30, 2021	Dec. 31, 2020
Debt Securities, Available-for-sale [Line Items]
Available-for-sale securities in a continuous unrealized loss position	$ 13,246	$ 0
Gross Unrealized Losses	$ (14)	$ 0

Investments and Fair Value Me_5

Investments and Fair Value Measurements - Sales of Available-for-Sale Investments (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020
Debt Securities, Available-for-sale [Line Items]
Proceeds from sale of available-for sale securities			$ 0	$ 9,767
Corporate notes and bonds
Debt Securities, Available-for-sale [Line Items]
Proceeds from sale of available-for sale securities	$ 0	$ 4,793	$ 0	$ 9,767

Lines of Credit - Loan Agreemen

Lines of Credit - Loan Agreements and Stand-by Letters of Credit (Details) - USD ($)	6 Months Ended
	Jun. 30, 2021	Dec. 31, 2020
Standby Letters of Credit
Line of Credit Facility [Line Items]
Letters of credit outstanding, amount	$ 12,200,000	$ 13,300,000
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 | Standby Letters of Credit
Line of Credit Facility [Line Items]
Commitment fee percentage	0.70%
Other Financial Institution | Line of Credit | Loan and Pledge Agreement
Line of Credit Facility [Line Items]
Maximum borrowing capacity	$ 5,100,000

Commitments and Contingencies -

Commitments and Contingencies - Right Of Use Asset and Lease Liability (Details) - USD ($) $ in Thousands	Jun. 30, 2021	Dec. 31, 2020
Leases [Abstract]
Operating lease, right of use asset	$ 15,383	$ 16,090
Lease liabilities, current	1,473	1,243
Lease liabilities, non-current	15,682	16,443
Total lease liability	$ 17,155	$ 17,686

Commitments and Contingencies_2

Commitments and Contingencies - Operating Lease Obligations (Details) - USD ($) $ in Thousands	Jun. 30, 2021	Dec. 31, 2020
Commitments and Contingencies Disclosure [Abstract]
Operating lease, right of use asset	$ 15,383	$ 16,090
Lease liabilities, current	1,473	1,243
Lease liabilities, non-current	15,682	16,443
Total lease liability	$ 17,155	$ 17,686

Commitments and Contingencies_3

Commitments and Contingencies - Lease Cost (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020
Commitments and Contingencies Disclosure [Abstract]
Operating lease expense	$ 642	$ 668	$ 1,285	$ 1,271
Cash payments	647	618	1,136	1,108
Non-cash lease liabilities arising from obtaining right-of-use assets	$ 0	$ 0	$ 0	$ 6,384

Commitments and Contingencies_4

Commitments and Contingencies - Weighted Average Lease Term and Discount Rate (Details)	Jun. 30, 2021
Leases [Abstract]
Weighted average remaining lease term	7 years 10 months 24 days
Weighted average discount rate	7.00%

Commitments and Contingencies_5

Commitments and Contingencies - Maturities of Lease Liabilities (Details) - USD ($) $ in Thousands	Jun. 30, 2021	Dec. 31, 2020
Operating Leases, Future Minimum Payments Due, Fiscal Year Maturity [Abstract]
2021 (remaining six months)	$ 1,295
2022	2,650
2023	2,580
2024	2,812
2025	2,736
2026 and thereafter	10,461
Total future minimum lease payments	22,534
Less imputed lease interest	(5,379)
Total lease liabilities	$ 17,155	$ 17,686

Commitments and Contingencies_6

Commitments and Contingencies - Product Warranty Liability (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020
Movement in Standard Product Warranty Accrual
Warranty reserve balance, beginning of period	$ 811	$ 665	$ 760	$ 631
Warranty costs charged to cost of revenue	81	75	208	173
Utilization charges against reserve	(13)	(1)	(13)	(2)
Release of accrual related to expired warranties	(70)	(66)	(146)	(129)
Warranty reserve balance, end of period	$ 809	$ 673	$ 809	$ 673

Commitments and Contingencies_7

Commitments and Contingencies - Purchase Obligations (Details) $ in Millions	6 Months Ended
	Jun. 30, 2021USD ($)
Commitments and Contingencies Disclosure [Abstract]
Long-term purchase commitment	$ 6.7

Income Taxes (Details)

Income Taxes (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020
Income Tax Disclosure [Abstract]
(Benefit from) provision for income taxes	$ (743)	$ 4,586	$ (1,383)	$ 4,501
Discrete items	728	(272)	2,355	(82)
Provision for (benefit from) income taxes, excluding discrete items	$ (15)	$ 4,314	$ 972	$ 4,419
Effective tax rate	(227.90%)	21.30%	(21.10%)	20.40%
Effective tax rate, excluding discrete items	(5.10%)	20.10%	14.80%	20.00%

Stockholders' Equity - Stock Re

Stockholders' Equity - Stock Repurchase Program (Details) - March 2021 Authorization - USD ($)	6 Months Ended
	Jun. 30, 2021	Mar. 09, 2021
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock repurchase program, authorized amount		$ 50,000,000
Treasury stock, shares, acquired (in shares)	656,938
Treasury stock, value, acquired, cost method	$ 11,600,000

Segment Reporting - Summary of

Segment Reporting - Summary of Financial Information by Segment (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020
Segment Reporting Information [Line Items]
Revenue	$ 20,607	$ 43,608	$ 49,547	$ 65,152
General and administrative	6,175	5,599	12,781	12,480
Sales and marketing	2,537	1,497	5,240	3,635
Research and development	4,424	6,352	8,926	13,061
Amortization of intangible assets	3	4	7	8
Impairment of long-lived assets	0	2,332	0	2,332
Total operating expenses	13,139	15,784	26,954	31,516
Income from operations	287	21,275	6,431	21,403
Other income, net	39	237	121	645
Income before income taxes	326	21,512	6,552	22,048
Water
Segment Reporting Information [Line Items]
Revenue	20,568	19,256	49,508	38,257
Emerging Technologies
Segment Reporting Information [Line Items]
Revenue	39	24,352	39	26,895
Operating Segments
Segment Reporting Information [Line Items]
General and administrative	3,091	3,117	5,814	6,688
Sales and marketing	2,350	1,386	4,693	3,374
Research and development	4,424	6,352	8,926	13,061
Amortization of intangible assets	3	4	7	8
Impairment of long-lived assets		2,332		2,332
Total operating expenses	9,868	13,191	19,440	25,463
Income from operations	3,558	23,868	13,945	27,456
Operating Segments | Water
Segment Reporting Information [Line Items]
General and administrative	1,776	1,967	3,333	4,046
Sales and marketing	2,121	1,124	4,285	2,800
Research and development	595	960	1,096	1,862
Amortization of intangible assets	3	4	7	8
Impairment of long-lived assets		0		0
Total operating expenses	4,495	4,055	8,721	8,716
Income from operations	8,892	8,652	24,625	17,308
Operating Segments | Emerging Tech
Segment Reporting Information [Line Items]
General and administrative	1,315	1,150	2,481	2,642
Sales and marketing	229	262	408	574
Research and development	3,829	5,392	7,830	11,199
Amortization of intangible assets	0	0	0	0
Impairment of long-lived assets		2,332		2,332
Total operating expenses	5,373	9,136	10,719	16,747
Income from operations	(5,334)	15,216	(10,680)	10,148
Corporate
Segment Reporting Information [Line Items]
Total operating expenses	3,271	2,593	7,514	6,053
Product
Segment Reporting Information [Line Items]
Revenue	20,607	19,256	49,547	38,257
Product cost of revenue	7,181	6,549	16,162	12,233
Product gross profit	13,426	12,707	33,385	26,024
Product | Operating Segments
Segment Reporting Information [Line Items]
Revenue	20,607	19,256	49,547	38,257
Product cost of revenue	7,181	6,549	16,162	12,233
Product gross profit	13,426	12,707	33,385	26,024
Product | Operating Segments | Water
Segment Reporting Information [Line Items]
Revenue	20,568	19,256	49,508	38,257
Product cost of revenue	7,181	6,549	16,162	12,233
Product gross profit	13,387	12,707	33,346	26,024
Product | Operating Segments | Emerging Tech
Segment Reporting Information [Line Items]
Revenue	39	0	39	0
Product cost of revenue	0	0	0	0
Product gross profit	39	0	39	0
License and development
Segment Reporting Information [Line Items]
Revenue	$ 0	24,352	$ 0	26,895
License and development | Schlumberger Technology Corporation | Affiliated Entity | VorTeq License Agreement | Emerging Tech
Segment Reporting Information [Line Items]
Revenue		24,400
License and development | Water
Segment Reporting Information [Line Items]
Revenue		0		0
License and development | Emerging Technologies
Segment Reporting Information [Line Items]
Revenue		24,352		26,895
License and development | Operating Segments
Segment Reporting Information [Line Items]
Revenue		24,352		26,895
License and development | Operating Segments | Water
Segment Reporting Information [Line Items]
Revenue		0		0
License and development | Operating Segments | Emerging Tech
Segment Reporting Information [Line Items]
Revenue		$ 24,352		$ 26,895

Concentrations - Product Revenu

Concentrations - Product Revenue Concentrations (Details) - Water - Product Revenue - Customer Concentration Risk	3 Months Ended		6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020
Customer A
Concentration Risk [Line Items]
Percentage of product revenue	30.00%	22.00%	22.00%	15.00%
Customer B
Concentration Risk [Line Items]
Percentage of product revenue	22.00%	19.00%	19.00%	24.00%
Customer C
Concentration Risk [Line Items]
Percentage of product revenue			12.00%
Customer D
Concentration Risk [Line Items]
Percentage of product revenue		22.00%	11.00%	21.00%

Concentrations - License and De

Concentrations - License and Development (Detail) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020
Concentration Risk [Line Items]
Revenue	$ 20,607	$ 43,608	$ 49,547	$ 65,152
License and development
Concentration Risk [Line Items]
Revenue	$ 0	$ 24,352	$ 0	$ 26,895
License and development | Revenue from Contract with Customer Benchmark | Customer Concentration Risk
Concentration Risk [Line Items]
Concentration risk, percentage				100.00%