Zix (ZIXI) 10-Q 9 Nov 20 2020 Q3 Quarterly report Financial data

Document and Entity Information

Document and Entity Information - shares	9 Months Ended
	Sep. 30, 2020	Nov. 05, 2020
Document And Entity Information [Abstract]
Document Type	10-Q
Amendment Flag	false
Document Period End Date	Sep. 30, 2020
Document Fiscal Year Focus	2020
Document Fiscal Period Focus	Q3
Trading Symbol	ZIXI
Entity Registrant Name	ZIX CORP
Entity Central Index Key	0000855612
Current Fiscal Year End Date	--12-31
Entity Filer Category	Accelerated Filer
Entity Small Business	false
Entity Emerging Growth Company	false
Entity Common Stock, Shares Outstanding		56,991,250
Entity Current Reporting Status	Yes
Entity Shell Company	false
Entity Interactive Data Current	Yes
Security Exchange Name	NASDAQ
Entity File Number	0-17995
Entity Tax Identification Number	75-2216818
Entity Address, Address Line One	2711 North Haskell Avenue
Entity Address, Address Line Two	Suite 2300, LB 36
Entity Address, City or Town	Dallas
Entity Address, State or Province	TX
Entity Address, Postal Zip Code	75204-2960
City Area Code	214
Local Phone Number	370-2000
Title of 12(b) Security	Common Stock, par value $0.01 per share
Entity Incorporation, State or Country Code	TX
Document Quarterly Report	true
Document Transition Report	false

Condensed Consolidated Balance

Condensed Consolidated Balance Sheets - USD ($) $ in Thousands	Sep. 30, 2020	Dec. 31, 2019
Current assets:
Cash and cash equivalents	$ 23,662	$ 13,349
Receivables, net	15,328	10,081
Prepaid and other current assets	3,966	4,984
Total current assets	42,956	28,414
Property and equipment, net	7,852	8,591
Operating lease assets	8,332	10,128
Intangible assets, net	137,367	145,876
Goodwill	170,930	171,209
Deferred tax assets	36,689	36,535
Deferred costs and other assets	12,461	11,968
Total assets	416,587	412,721
Current liabilities:
Accounts payable	17,717	14,400
Accrued expenses	11,473	13,732
Deferred revenue	41,095	40,757
Current portion of long-term debt	1,850	1,850
Operating lease liabilities, current	2,195	2,947
Finance lease liabilities, current	780	1,338
Total current liabilities	75,110	75,024
Long-term liabilities:
Deferred revenue	1,263	2,524
Noncurrent operating lease liabilities	7,113	8,389
Noncurrent finance lease liabilities	188	716
Long-term debt	183,830	178,250
Total long-term liabilities	192,394	189,879
Total liabilities	267,504	264,903
Commitments and contingencies (see Note 11)
Preferred stock:
Convertible preferred stock	113,241	106,527
Stockholders’ equity:
Preferred stock, $1 par value, 10,000,000 shares authorized; none issued and outstanding
Common stock, $0.01 par value, 175,000,000 shares authorized; 85,127,484 issued and 56,992,265 outstanding in 2020 and 83,393,514 issued and 55,640,397 outstanding in 2019	782	780
Additional paid-in capital	399,285	391,605
Treasury stock, at cost; 28,135,219 common shares in 2020 and 27,753,117 common shares in 2019	(113,015)	(110,298)
Accumulated deficit	(251,291)	(240,995)
Accumulated other comprehensive income (loss)	81	199
Total stockholders’ equity	35,842	41,291
Total liabilities, preferred stock and stockholders’ equity	416,587	412,721
Series A Convertible Preferred Stock [Member]
Preferred stock:
Convertible preferred stock	$ 113,241	$ 106,527

Condensed Consolidated Balanc_2

Condensed Consolidated Balance Sheets (Parenthetical) - $ / shares	Sep. 30, 2020	Dec. 31, 2019
Preferred stock, par value	$ 1	$ 1
Preferred stock, shares authorized	10,000,000	10,000,000
Preferred stock, shares issued	0	0
Preferred stock, shares outstanding	0	0
Common stock, par value	$ 0.01	$ 0.01
Common stock, shares authorized	175,000,000	175,000,000
Common stock, shares issued	85,127,484	83,393,514
Common stock, shares outstanding	56,992,265	55,640,397
Treasury stock, shares	28,135,219	27,753,117
Series A Convertible Preferred Stock [Member]
Convertible Preferred stock, par value	$ 1	$ 1
Convertible Preferred stock, shares designated	100,206	100,206
Convertible Preferred stock, shares issued	100,206	100,206
Convertible Preferred stock, shares outstanding	100,206	100,206

Condensed Consolidated Statemen

Condensed Consolidated Statements of Comprehensive Income (Loss) (Unaudited) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Income Statement [Abstract]
Revenue	$ 54,840	$ 47,833	$ 160,611	$ 123,049
Cost of revenue	27,928	21,422	82,265	52,865
Gross margin	26,912	26,411	78,346	70,184
Operating expenses:
Research and development	5,720	5,590	16,926	15,048
Selling, general and administrative	18,813	19,592	58,058	61,729
Total operating expenses	24,533	25,182	74,984	76,777
Operating income (loss)	2,379	1,229	3,362	(6,593)
Other income (expense):
Investment and other income	127	14	104	115
Interest expense	(2,035)	(2,973)	(7,190)	(7,398)
Total other expense	(1,908)	(2,959)	(7,086)	(7,283)
Income (loss) before income taxes	471	(1,730)	(3,724)	(13,876)
Income tax (expense) benefit	(1,196)	133	244	2,308
Net loss	(725)	(1,597)	(3,480)	(11,568)
Deemed and accrued dividends on preferred stock	2,267	2,090	6,714	7,894
Net loss attributable to common stockholders	$ (2,992)	$ (3,687)	$ (10,194)	$ (19,462)
Basic loss per share attributable to common stockholders	$ (50)	$ (70)	$ (190)	$ (370)
Diluted loss per common share attributable to common stockholders	$ (50)	$ (70)	$ (190)	$ (370)
Basic weighted average common shares outstanding	54,999,114	53,148,078	53,933,721	52,965,163
Diluted weighted average common shares outstanding	54,999,114	53,148,078	53,933,721	52,965,163
Other comprehensive income (loss), net of tax
Foreign currency translation adjustments	$ 493	$ 35	$ (118)	$ (52)
Comprehensive loss	$ (232)	$ (1,562)	$ (3,598)	$ (11,620)

Condensed Consolidated Statem_2

Condensed Consolidated Statement of Preferred Stock and Stockholders' Equity (Unaudited) - USD ($) $ in Thousands	Total	Cumulative Effect, Period of Adoption, Adjustment [Member]	Series A Convertible Preferred Stock [Member]	Series B Convertible Preferred Stock [Member]	Preferred Stock [Member]	Preferred Stock [Member]Series A Convertible Preferred Stock [Member]	Preferred Stock [Member]Series B Convertible Preferred Stock [Member]	Common Stock [Member]	Additional Paid-In Capital [Member]	Treasury Stock [Member]	Accumulated Deficit [Member]	Accumulated Deficit [Member]Cumulative Effect, Period of Adoption, Adjustment [Member]	Accumulated Deficit [Member]Series A Convertible Preferred Stock [Member]	Accumulated Deficit [Member]Series B Convertible Preferred Stock [Member]	Accumulated Other Comprehensive Income (Loss) [Member]
Beginning balances at Dec. 31, 2018	$ 60,947							$ 779	$ 384,940	$ (108,392)	$ (216,364)				$ (16)
Beginning balances, shares at Dec. 31, 2018								81,715,330
Issuance of preferred stock in connection with private placement						$ 62,662	$ 33,881
Issuance of preferred stock in connection with private placement, shares						64,914	35,086
Beneficial conversion feature of preferred stock			$ (1,407)			$ 1,407							$ (1,407)
Accretion of beneficial conversion feature of Preferred Shares (Participating)			(12)			12							(12)
Accrued dividend on preferred stock			(563)	$ (380)		563	$ 380						(563)	$ (380)
Redemption accretion of preferred stock				(71)			71							(71)
Net issuance of common stock upon exercise of stock options	36								36
Net issuance of common stock upon exercise of stock options, shares								17,438
Net issuance of common stock upon vesting of restricted stock units								40,334
Net issuance of common stock upon vesting of performance stock units								5,777
Net issuance of restricted common stock								1,116,724
Net issuance of restricted performance common stock								392,500
Employee stock-based compensation costs	(111)								1,229	(1,340)
Adjustment from foreign currency translation	(32)														(32)
Net loss	(6,265)										(6,265)
Ending balances at Mar. 31, 2019	52,142							$ 779	386,205	(109,732)	(225,062)				(48)
Ending balances, shares at Mar. 31, 2019					100,000
Ending balances at Mar. 31, 2019					$ 98,976
Ending balances, shares at Mar. 31, 2019								83,288,103
Beginning balances at Dec. 31, 2018	60,947							$ 779	384,940	(108,392)	(216,364)				(16)
Beginning balances, shares at Dec. 31, 2018								81,715,330
Adjustment from foreign currency translation	(52)
Net loss	(11,568)
Ending balances at Sep. 30, 2019	44,629							$ 780	390,016	(110,273)	(235,826)				(68)
Ending balances, shares at Sep. 30, 2019					100,206
Ending balances at Sep. 30, 2019					$ 104,437
Ending balances, shares at Sep. 30, 2019								83,493,659
Beginning balances at Mar. 31, 2019	52,142							$ 779	386,205	(109,732)	(225,062)				(48)
Beginning balances, shares at Mar. 31, 2019					100,000
Beginning balances at Mar. 31, 2019					$ 98,976
Beginning balances, shares at Mar. 31, 2019								83,288,103
Issuance of Series A preferred stock for dividend on Series B preferred stock upon conversion to Series A preferred, shares					206
Beneficial conversion feature of preferred stock				(1,067)			1,067							(1,067)
Accretion of beneficial conversion feature of Preferred Shares (Participating)			(33)			33							(33)
Accrued dividend on preferred stock			(1,505)	(650)		1,505	650						(1,505)	(650)
Redemption accretion of preferred stock				$ (116)			$ 116							$ (116)
Net issuance of common stock upon exercise of stock options	144								144
Net issuance of common stock upon exercise of stock options, shares								40,000
Net issuance of common stock upon vesting of restricted stock units								3,333
Net issuance of common stock upon vesting of performance stock units								1,223
Net issuance of restricted common stock								16,000
Employee stock-based compensation costs	1,490								1,964	(474)
Adjustment from foreign currency translation	(56)														(56)
Net loss	(3,706)										(3,706)
Ending balances at Jun. 30, 2019	46,643							$ 779	388,313	(110,206)	(232,139)				(104)
Ending balances, shares at Jun. 30, 2019					100,206
Ending balances at Jun. 30, 2019					$ 102,347
Ending balances, shares at Jun. 30, 2019								83,348,659
Accretion of beneficial conversion feature of Preferred Shares (Participating)			(44)			44							(44)
Accrued dividend on preferred stock			$ (2,046)			2,046							(2,046)
Net issuance of common stock upon exercise of stock options	71							$ 1	70
Net issuance of common stock upon exercise of stock options, shares								30,000
Net issuance of restricted common stock								115,000
Employee stock-based compensation costs	1,566								1,633	(67)
Adjustment from foreign currency translation	35
Net loss	(1,597)										(1,597)
Ending balances at Sep. 30, 2019	44,629							$ 780	390,016	(110,273)	(235,826)				(68)
Ending balances, shares at Sep. 30, 2019					100,206
Ending balances at Sep. 30, 2019					$ 104,437
Ending balances, shares at Sep. 30, 2019								83,493,659
Adjustment from foreign currency translation	36														36
Beginning balances at Dec. 31, 2019	41,291							$ 780	391,605	(110,298)	(240,995)				199
Beginning balances, shares at Dec. 31, 2019			100,206		100,206
Beginning balances at Dec. 31, 2019	106,527		$ 106,527		$ 106,527
Beginning balances, shares at Dec. 31, 2019								83,393,514
Cumulative effect adjustment from changes in accounting standard (Note 2) at Dec. 31, 2019		$ (103)										$ (103)
Beginning balances, as adjusted at Dec. 31, 2019	41,188				$ 106,527			$ 780	391,605	(110,298)	(241,098)				199
Accretion of beneficial conversion feature of Preferred Shares (Participating)			(48)			48							(48)
Accrued dividend on preferred stock			$ (2,181)			2,181							(2,181)
Net issuance of common stock upon exercise of stock options	117							$ 1	116
Net issuance of common stock upon exercise of stock options, shares								46,875
Net issuance of common stock upon vesting of restricted stock units								30,084
Net issuance of common stock upon vesting of performance stock units								16,062
Net issuance of restricted common stock								1,062,683
Net issuance of restricted performance common stock								404,746
Employee stock-based compensation costs	204								1,989	(1,785)
Adjustment from foreign currency translation	(905)														(905)
Net loss	(853)										(853)
Ending balances at Mar. 31, 2020	37,522							$ 781	393,710	(112,083)	(244,180)				(706)
Ending balances, shares at Mar. 31, 2020					100,206
Ending balances at Mar. 31, 2020					$ 108,756
Ending balances, shares at Mar. 31, 2020								84,953,964
Beginning balances at Dec. 31, 2019	41,291							$ 780	391,605	(110,298)	(240,995)				199
Beginning balances, shares at Dec. 31, 2019			100,206		100,206
Beginning balances at Dec. 31, 2019	106,527		$ 106,527		$ 106,527
Beginning balances, shares at Dec. 31, 2019								83,393,514
Cumulative effect adjustment from changes in accounting standard (Note 2) at Dec. 31, 2019		$ (103)										$ (103)
Beginning balances, as adjusted at Dec. 31, 2019	41,188				$ 106,527			$ 780	391,605	(110,298)	(241,098)				199
Adjustment from foreign currency translation	(118)
Net loss	(3,480)
Ending balances at Sep. 30, 2020	35,842							$ 782	399,285	(113,015)	(251,291)				81
Ending balances, shares at Sep. 30, 2020			100,206		100,206
Ending balances at Sep. 30, 2020	113,241		$ 113,241		$ 113,241
Ending balances, shares at Sep. 30, 2020								85,127,484
Beginning balances at Mar. 31, 2020	37,522							$ 781	393,710	(112,083)	(244,180)				(706)
Beginning balances, shares at Mar. 31, 2020					100,206
Beginning balances at Mar. 31, 2020					$ 108,756
Beginning balances, shares at Mar. 31, 2020								84,953,964
Accretion of beneficial conversion feature of Preferred Shares (Participating)			(47)			47							(47)
Accrued dividend on preferred stock			(2,171)			2,171							(2,171)
Net issuance of common stock upon exercise of stock options	217							$ 1	216
Net issuance of common stock upon exercise of stock options, shares								67,500
Net issuance of common stock upon vesting of restricted stock units								75,631
Net issuance of common stock upon vesting of performance stock units								32,848
Net issuance of restricted common stock								6,590
Net issuance of restricted performance common stock								(26,666)
Employee stock-based compensation costs	2,454								3,251	(797)
Adjustment from foreign currency translation	294														294
Net loss	(1,902)										(1,902)
Ending balances at Jun. 30, 2020	$ 36,368							$ 782	397,177	(112,880)	(248,299)				(412)
Ending balances, shares at Jun. 30, 2020					100,206
Ending balances at Jun. 30, 2020					$ 110,974
Ending balances, shares at Jun. 30, 2020								85,109,867
Accretion of beneficial conversion feature of Preferred Shares (Participating)			(48)			48							(48)
Accrued dividend on preferred stock			$ (2,219)			$ 2,219							$ (2,219)
Net issuance of common stock upon exercise of stock options, shares	0
Net issuance of common stock upon vesting of restricted stock units								7,084
Net issuance of restricted common stock								10,533
Employee stock-based compensation costs	$ 1,973								2,108	(135)
Adjustment from foreign currency translation	493														493
Net loss	(725)										(725)
Ending balances at Sep. 30, 2020	35,842							$ 782	$ 399,285	$ (113,015)	$ (251,291)				$ 81
Ending balances, shares at Sep. 30, 2020			100,206		100,206
Ending balances at Sep. 30, 2020	$ 113,241		$ 113,241		$ 113,241
Ending balances, shares at Sep. 30, 2020								85,127,484

Condensed Consolidated Statem_3

Condensed Consolidated Statement of Preferred Stock and Stockholders' Equity (Parenthetical) (Unaudited) - USD ($) $ in Thousands	Feb. 20, 2019	Mar. 31, 2019
Series A Convertible Preferred Stock [Member]
Preferred stock, net of issuance costs	$ 2,300	$ 2,253
Series B Convertible Preferred Stock [Member]
Preferred stock, net of issuance costs	$ 1,200	$ 1,204

Condensed Consolidated Statem_4

Condensed Consolidated Statements of Cash Flows (Unaudited) - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019
Operating activities:
Net income (loss)	$ (3,480)	$ (11,568)
Non-cash items in net income (loss):
Depreciation and amortization	23,604	16,301
Amortization of debt issuance costs	970	661
Employee stock-based compensation costs	7,349	4,826
Noncash lease costs	2,189	(468)
Changes in deferred taxes	(154)	(2,150)
Changes in operating assets and liabilities:
Receivables	(5,239)	(394)
Prepaid and other current assets	1,014	(713)
Deferred costs and other assets	(681)	(1,998)
Accounts payable	3,321	4,247
Deferred revenue	(922)	1,017
Payment of acquisition related contingent consideration		(582)
Accrued and other liabilities	(3,726)	(1,228)
Net cash provided by operating activities	24,245	7,951
Investing activities:
Purchases of property, equipment and internal-use software	(13,992)	(7,860)
Acquisition of business, net of cash acquired		(284,590)
Net cash used in investing activities	(13,992)	(292,450)
Financing activities:
Proceeds of long-term debt	6,000	185,000
Debt issuance cost		(6,443)
Repayment of long term debt	(1,388)	(900)
Repayment of finance lease liabilities	(1,086)	(1,277)
Proceeds from exercise of stock options	334	251
Purchase of treasury shares	(2,717)	(1,881)
Payment of acquisition related contingent consideration	(1,125)	(3,843)
Net cash provided by financing activities	18	267,495
Effect of exchange rate on cash	42	(39)
Increase (decrease) in cash and cash equivalents	10,313	(17,043)
Cash and cash equivalents, beginning of period	13,349	27,109
Cash and cash equivalents, end of period	$ 23,662	10,066
Series A Convertible Preferred Stock [Member]
Financing activities:
Proceeds from issuance of preferred stock, net of offering costs		$ 96,588

Basis of Presentation

Basis of Presentation	9 Months Ended
	Sep. 30, 2020
Organization Consolidation And Presentation Of Financial Statements [Abstract]
Basis of Presentation	1. Basis of Presentation The accompanying condensed consolidated financial statements of Zix Corporation (“Zix,” the “Company,” “we,” “our” or “us”) should be read in conjunction with the audited consolidated financial statements included in the Company’s 2019 Annual Report on Form 10-K. These financial statements are unaudited, but have been prepared in the ordinary course of business for the purpose of providing information with respect to the covered interim periods. Management of the Company believes that all adjustments necessary for a fair presentation for such periods have been included and are of a normal recurring nature. The results of operations for the three- and nine-month periods ended September 30, 2020, are not necessarily indicative of the results to be expected for any future periods or for the full fiscal year. The preparation of financial statements and related disclosures in accordance with accounting principles generally accepted in the United States requires the Company’s management to make estimates and assumptions that affect reported amounts and disclosures. These estimates and assumptions take into account historical and forward-looking factors that the Company believes are reasonable, including but not limited to the potential impacts arising from the recent coronavirus (COVID-19) and public and private sector policies and initiatives aimed at reducing its transmission. As the extent and duration of the impacts of the COVID-19 remain unclear, the Company’s estimates and assumptions may evolve as conditions change. Actual results could differ significantly from those estimates.

Recent Accounting Standards and

Recent Accounting Standards and Pronouncements	9 Months Ended
	Sep. 30, 2020
Accounting Changes And Error Corrections [Abstract]
Recent Accounting Standards and Pronouncements	2. Recent Accounting Standards and Pronouncements Credit Losses On January 1, 2020, we adopted Accounting Standard Update No. 2016-13, Financial Instruments-Credit Losses (Topic 326): Measurement of Credit Losses on Financial Instruments with a net increase of our receivables allowance and a related cumulative adjustment to our retained earnings recorded at the beginning of adoption. Upon adoption, we changed our impairment model to utilize a forward-looking current expected credit losses (CECL) model in place of the incurred loss impairment model for our accounting receivable balance. The cumulative effect adjustment from adoption was immaterial to our condensed consolidated financial statements. Intangibles – Goodwill and Other In January 2017, the FASB issued Accounting Standards Update No. 2017-04, Intangibles—Goodwill and Other (Topic 350): Simplifying the Test for Goodwill Impairment (ASU 2017-04) to simplify the subsequent measurement of goodwill. The guidance removes Step 2 of the goodwill impairment test, which requires a hypothetical purchase price allocation. A goodwill impairment will now be the amount by which a reporting unit's carrying value exceeds its fair value, not to exceed the carrying amount of goodwill. The accounting standard became effective for us beginning January 1, 2020, and did not have a material impact on the Company's consolidated financial position, results of operations or cash flows. Income Taxes In December 2019, the FASB issued Accounting Standard Update No. 2019-12, Income Taxes (Topic 740): Simplifying the Accounting for Income Taxes (ASU 2019-12), which simplifies the accounting for income taxes. This guidance will be effective for us in the first quarter of 2021 on a prospective basis, and early adoption is permitted. We are currently evaluating the impact of the new guidance on our consolidated financial statements.

Stock- Based Awards and Stock-B

Stock- Based Awards and Stock-Based Employee Compensation Expense	9 Months Ended
	Sep. 30, 2020
Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]
Stock- Based Awards and Stock-Based Employee Compensation Expense	3. Stock- Based Awards and Stock-Based Employee Compensation Expense Our stock-based awards include (i) stock options, (ii) restricted stock awards, some of which are subject to time-based vesting (“Restricted Stock”) and some of which are subject to performance-based vesting (“Performance Stock”), and (iii) restricted stock units, some of which are subject to time-based vesting (“RSUs”) and some of which are subject to performance-based vesting (“Performance RSUs”). As of September 30, 2020, the Company had 742,010 stock options outstanding, 2,020,704 non-vested Restricted Stock awards; 691,852 non-vested Performance Stock awards; 136,103 non-vested RSUs; 44,349 non-vested Performance RSUs and 2,377,521 shares of common stock available for grant. Stock Option Activity The following is a summary of all stock option transactions during the three months ended September 30, 2020: Options Weighted Average Exercise Price Weighted Average Remaining Contractual Term (Yrs) Outstanding at June 30, 2020 742,010 $ 4.09 5.01 Granted at market price — — Cancelled or expired — — Exercised — — Outstanding at September 30, 2020 742,010 $ 4.09 4.76 Options exercisable at September 30, 2020 654,510 $ 3.57 4.13 At September30, 2020, 742,010 stock options outstanding and 642,010 stock options exercisable had an exercise price lower than the market price of the Company’s common stock on that date. The aggregate intrinsic value of these stock options was $1.5 million and $1.5 million, respectively. Restricted Stock Activity The following is a summary of Restricted Stock activity during the three months ended September 30, 2020: Restricted Shares Weighted Average Fair Value Non-vested restricted stock at June 30, 2020 2,090,745 $ 7.36 Granted at market price 30,500 6.12 Vested (80,574 ) 6.85 Cancelled (19,967 ) 7.53 Non-vested restricted stock at September 30, 2020 2,020,704 $ 7.36 Restricted Stock Unit Activity The following is a summary of all RSU activity during the three months ended September 30, 2020: Restricted Stock Units Weighted Average Fair Value Non-vested restricted stock units at June 30, 2020 153,099 $ 8.62 Granted at market price — — Vested (16,996 ) 9.13 Cancelled — — Non-vested restricted stock units at September 30, 2020 136,103 $ 8.56 Performance RSU Activity The following is a summary of all Performance RSU activity during the three months ended September 30, 2020: Performance RSUs Weighted Average Fair Value Non-vested performance RSUs at June 30, 2020 44,349 $ 8.84 Granted at market price — — Vested — — Forfeited — — Non-vested performance RSUs at September 30, 2020 44,349 $ 8.84 Performance Stock Activity The following is a summary of all Performance Stock activity during the three months ended September 30, 2020: Performance Stock Weighted Average Fair Value Non-vested performance stock at June 30, 2020 691,852 $ 7.52 Granted at market price — — Vested — — Forfeited — — Non-vested performance stock at September 30, 2020 691,852 $ 7.52 The weighted average grant-date fair value of awards of Restricted Stock, RSUs, Performance RSUs and Performance Stock is based on the quoted market price of the Company’s common stock on the date of grant. Stock-Based Compensation Expense For the three- and nine-month periods ended September 30, 2020, the total stock-based employee compensation expense resulting from stock options, Restricted Stock, RSUs, Performance RSUs and Performance Stock was recorded to the following line items of the Company’s condensed consolidated statements of income: (In thousands) Three Months Ended September 30, 2020 Nine Months Ended September 30, 2020 Cost of revenues $ 97 $ 1,105 Research and development 433 1,184 Selling, general and administrative 1,578 5,060 Stock-based compensation expense $ 2,108 $ 7,349 A deferred tax asset totaling $1.4 million and $775 thousand, resulting from stock-based compensation expense associated with awards relating to the Company’s U.S. operations, was recorded for the nine-month periods ended September 30, 2020 and 2019, respectively. As of September 30, 2020, there was $16.4 million of total unrecognized stock-based compensation expense related to non-vested stock-based compensation awards granted under the incentive plans. This expense is expected to be recognized over a weighted average period of 1.99 years. For additional information regarding the Company’s Equity Awards and Stock-based Employee Compensation, see Note 3, Stock Options and Stock-Based Employee Compensation

Supplemental Cash Flow Informat

Supplemental Cash Flow Information	9 Months Ended
	Sep. 30, 2020
Supplemental Cash Flow Elements [Abstract]
Supplemental Cash Flow Information	4. Supplemental Cash Flow Information Supplemental cash flow information relating to taxes and non-cash activities: Nine Months Ended September 30, (In thousands) 2020 2019 Cash income tax payments $ 217 $ 338 Cash paid for interest 5,812 6,696 Non-cash investing and financing activities: Accrued and deemed dividends on Series A preferred stock 6,714 5,610 Accrued and deemed dividends on Series B preferred stock — 2,284

Receivables, Net

Receivables, Net	9 Months Ended
	Sep. 30, 2020
Receivables [Abstract]
Receivables, Net	5. Receivables, net (In thousands) September 30, 2020 December 31, 2019 Gross accounts receivables $ 28,245 $ 21,193 Allowance for credit losses $ (304 ) $ — Allowance for returns and doubtful accounts — (265 ) Unpaid portion of deferred revenue (12,613 ) (10,847 ) Note receivable 458 458 Allowance for note receivable (458 ) (458 ) Receivables, net $ 15,328 $ 10,081 Prior to January 1, 2020, accounts receivable were recorded at cost less an allowance for doubtful accounts. We maintained an allowance for uncollectible accounts receivable for estimated losses resulting from the failure or inability of our customers to make required payments. Subsequent to January 1, 2020, accounts receivable are recorded at cost less an allowance for credit losses. We estimate losses on receivables at the reporting date based on expected losses resulting from the inability of our customers to make required payments, including our historical experience of actual losses and the aging of such receivables. These receivables have been pooled by shared risk characteristics. Based on known information we may also establish specific reserves for customers in an adverse financial condition or adjust our expectations of changes in conditions that may impact the collectability of outstanding receivables. As of September 30, 2020, based on available information to date, the Company assessed no material impact related to potential losses caused by COVID-19. The reduction for the unpaid portion of deferred revenue represents future customer service or maintenance obligations that have been billed to customers, but remain unpaid as of the respective balance sheet dates. Deferred revenue on our consolidated balance sheets represents future customer service or maintenance obligations that have been billed and collected as of the respective balance sheet dates. The note receivable represents the remaining outstanding balance of an original note related to the sale of a product line in 2005 in the amount of $540 thousand. This was fully reserved at the time of the sale, as the note’s collectability was not assured. The note receivable is fully reserved at September 30, 2020.

Leases

Leases	9 Months Ended
	Sep. 30, 2020
Leases [Abstract]
Leases	6. Leases Effective January 1, 2019, the Company adopted ASC 842, which requires recognition of a right-of-use asset and lease liability for all leases at the commencement date based on the present value of lease payments over the lease term. Additional qualitative and quantitative disclosures regarding the Company's leasing arrangements are also required. The Company adopted ASC 842 prospectively and elected the package of transition practical expedients that does not require reassessment of (1) whether any existing or expired contracts are or contain leases, (2) lease classification and (3) initial direct costs. In addition, the Company has elected other available practical expedients to not separate lease and nonlease components, which consist principally of common area maintenance charges, for all classes of underlying assets and to exclude leases with an initial term of 12 months or less. The Company determines if a contract is or contains a lease at inception. The Company has operating leases for office spaces and data centers and finance leases for equipment. The Company has entered into lease contracts ranging from 1 to 13 years with the majority of leases having terms one to seven years, many of which include options to extend in various increments. Variable lease costs consist primarily of variable common area maintenance, taxes, insurance, parking and utilities. The Company’s leases do not have any residual value guarantees or restrictive covenants. As the implicit rate is not readily determinable for most of the Company’s lease agreements, the Company uses an estimated incremental borrowing rate to determine the initial present value of lease payments. These discount rates for leases are calculated using the Company's weighted average interest rate of the term loan and delayed draw term loan. The components of lease costs are as follows: Three Months Ended September 30, Nine Months Ended September 30, (In thousands) 2020 2020 Finance lease costs: Amortization of right-of-use asset $ 261 $ 949 Interest on lease liabilities 18 71 Operating lease costs 785 2,658 Short-term lease costs 493 1,490 Variable lease costs 165 649 Total lease costs $ 1,722 $ 5,817 Supplemental cash flow information related to leases are as follows: Nine Months Ended September 30, (In thousands) 2020 Cash paid for amounts included in the measurement of lease liabilities: Operating cash flows from operating leases $ 2,897 Operating cash flows from finance leases 71 Financing cash flows from finance leases 1,086 Right-of-use assets obtained in exchange for lease obligations: Operating leases 523 Finance leases — Supplemental balance sheet information related to lease are as follows: September 30, (In thousands) Balance Sheet Classification 2020 Operating Leases Operating lease right-of-use assets Operating lease assets $ 8,332 Total operating lease assets $ 8,332 September 30, (In thousands) Balance Sheet Classification 2020 Finance Leases Finance lease right-of-use assets $ 3,362 Accumulated depreciation - finance leases (2,261 ) Finance lease right-of-use assets, net Property and equipment, net $ 1,101 Weighted average remaining lease term and weighted average discount rate are as follows: Weighted Average Remaining Lease Term (Years) Operating leases 4.06 Finance leases 1.53 Weighted Average Discount Rate Operating leases 4.95 % Finance leases 6.14 % Maturities of lease liabilities are as follows: Payments Due by Period - Year Ending December 31, 2020 (In thousands) Total Year 1 (1) Years 2 & 3 Years 4 & 5 Beyond 5 Years Operating leases $ 10,282 $ 735 $ 4,904 $ 3,870 $ 773 Less imputed interest (974 ) Total $ 9,308 Finance leases $ 1,008 $ 266 $ 736 $ 6 $ — Less imputed interest (40 ) Total $ 968 (1) During the nine months ended September 30, 2020, we entered into an operating lease for an additional data center, which has not yet commenced and is expected to be added as a lease liability at a value of approximately $109 thousand. This operating lease is expected to commence in the fourth quarter of 2020 with a lease term of 3 years. Additionally, we modified one of our office leases which resulted a write-off of right-of-use assets and lease liability at a value of approximately $438 thousand and $570 thousand, respectively, and a gain of $132 thousand recognized as other income for the three month period ended September 30, 2020.

Long-term Debt

Long-term Debt	9 Months Ended
	Sep. 30, 2020
Debt Disclosure [Abstract]
Long-term Debt	7. Long-term Debt On February 20, 2019, the Company entered into a credit agreement (the “Credit Agreement”) with a syndicate of lenders and SunTrust Bank as administrative agent, which (1) provides for borrowing in the form of a senior secured term loan facility in an aggregate principal amount of $175 million (the “Term Loan”), (2) provides for a senior secured delayed draw term loan facility in an aggregate principal amount of $10 million (the “Delayed Draw Term Loan Facility”), and (3) provides for a senior secured revolving credit facility in an aggregate principal amount of $25 million, up to $5 million of which is available for letters of credit (the “Revolving Facility” and, together with the Term Loan and the Delayed Draw Term Loan Facility, the “Credit Facilities”). On February 20, 2019, the Term Loan was borrowed in full to pay a portion of the purchase price in connection with the AppRiver acquisition (described below in Note 16 “Acquisitions”) (including certain fees, costs and expenses related thereto). On May 2, 2019, the Delayed Draw Term Loan Facility was borrowed in full to pay a portion of the purchase price in connection with the DeliverySlip acquisition (described below in Note 16 “Acquisitions”) (including certain fees, costs and expenses related thereto). As of September 30, 2020, the Company had an outstanding debt balance of $8.0 million attributable to the Revolving Facility. The Credit Facilities are secured by substantially all the assets of Zix and its wholly-owned domestic subsidiaries and guaranteed by substantially all of Zix’s wholly-owned domestic subsidiaries. Borrowings under the Credit Agreement bear interest, at the Company’s option, at either (1) the adjusted LIBO rate (as defined in the Credit Agreement) plus a margin ranging from 2.50% to 3.50% or (2) the alternate base rate (as defined in the Credit Agreement) plus a margin ranging from 1.50% to 2.50%. The applicable margin varies depending on the Company’s total net leverage ratio. The Credit Facilities are scheduled to mature on February 20, 2024, unless extended in accordance with the terms of the Credit Agreement. The Credit Agreement includes procedures for additional financial institutions to become lenders, or for any existing lender to increase its commitments thereunder, subject to the limits and conditions set forth in the Credit Agreement. Optional prepayments of borrowings under the Credit Facilities are permitted at any time and do not require any prepayment premium (other than reimbursement of the lenders’ breakage and redeployment costs in the case of a prepayment of LIBO rate borrowings). The Credit Agreement contains various financial, operational, and legal covenants. The financial covenant is tested on a quarterly basis, based on the rolling four-quarter period that ends on the last day of each fiscal quarter. The financial covenant requires the Company to maintain a maximum total net leverage ratio of: • 4.75:1.00 for the fiscal quarters ending September 30, 2020 through March 31, 2021; • 4.50:1.00 for the fiscal quarters ending June 30, 2021 through December 31, 2021; and • 4.25:1.00 for the fiscal quarter ending March 31, 2022 and each fiscal quarter thereafter. The non-financial covenants restrict the Company’s ability and the ability of the Company’s restricted subsidiaries to, among other things, incur indebtedness, incur liens, merge with or acquire other entities, make investments, dispose of assets, enter into sale and leaseback transactions, make dividends, distributions or stock repurchases, prepay junior indebtedness, enter into transactions with affiliates, enter into restrictive agreements, and amend organizational documents or the terms of junior indebtedness. The Credit Agreement contains events of default that Zix believes are customary for a secured credit facility. If an event of default relating to bankruptcy or other insolvency events occurs, all obligations under the Credit Agreement will immediately become due and payable. If any other event of default exists under the Credit Agreement, the lenders may accelerate the maturity of the Credit Facilities and exercise other rights and remedies, including foreclosure or other actions against the collateral. If any default exists under the Credit Agreement, or if the Company is unable to make any of the representations and warranties in the Credit Agreement at the applicable time, Zix will be unable to borrow additional funds or have letters of credit issued under the Credit Agreement. On November 5, 2020, the Company amended its Credit Agreement to, among other things, borrow an incremental $35.0 million term loan. See Note 17 – Subsequent Events for more information. Term Loan As of September 30, 2020, the Company had $172.4 million in principal outstanding under the Term Loan. The Term Loan was fully drawn on February 20, 2019 in the amount of $175 million and requires quarterly payments of principal of $437.5 thousand beginning on June 30, 2019. In addition to other customary mandatory prepayment requirements, the Term Loan requires annual prepayments based on a percentage of Zix’s excess cash flow, which percentage will reduce if Zix’s total net leverage ratio decreases. Based on the calculation of excess cash flow and total net leverage ratio and for the year ended December 31, 2019, the Company is not required to make prepayment in addition to the quarterly installment. At September 30, 2020, the Company had an outstanding debt balance of $167.8 million attributable to the Term Loan based on the 4.39% interest rate in effect during the three-month period ended on September 30, 2020. Included in the balance at September 30, 2020 is $4.6 million of unamortized debt issuance costs. Future principal payments under the Term Loan as of September 30, 2020, are as follows: (In thousands) Year Ending December 31, Amount 2020 $ 438 2021 1,750 2022 1,750 2023 1,750 2024 166,688 Total $ 172,376 Delayed Draw Term Loan Facility At September 30, 2020, the Company had $9.9 million in principal outstanding under the Delayed Draw Term Loan Facility. The Delayed Draw Term Loan Facility was fully drawn on May 2, 2019 in the amount of $10 million to fund the DeliverySlip acquisition. The Delayed Draw Term Loan Facility requires 1.00% per annum amortization of the original principal amount borrowed, payable in equal quarterly installments of $25 thousand starting September 30, 2019. In addition to other customary mandatory prepayment requirements, the Delayed Draw Term Loan Facility requires annual prepayments based on a percentage of Zix’s excess cash flow, which percentage reduces if Zix’s total net leverage ratio decreases. Based on the calculation of excess cash flow and total net leverage ratio and for the year ended December 31, 2019, the Company is not required to make prepayment in addition to the quarterly installment. At September 30, 2020, the Company had an outstanding debt balance of $9.8 million attributable to the Delayed Draw Term Loan Facility based on the 3.76% interest rate in effect during the three-months ended on September 30, 2020. Included in the balance at September 30, 2020 is $37 thousand of unamortized debt issuance costs. Future principal payments under the Delayed Draw Term Loan Facility as of September 30, 2020 are as follows: (In thousands) Year Ending December 31, Amount 2020 $ 25 2021 100 2022 100 2023 100 2024 9,550 Total $ 9,875 Revolving Facility The Company also has a Revolving Facility with the lenders, pursuant to which the lenders agreed to make a Revolving Facility available to the Company in an aggregate amount of up to $25 million. Proceeds from the Revolving Facility may be used for working capital and general business purposes, including the financing of permitted acquisitions, investments and restricted payments, subject to the conditions contained in the Credit Agreement. Zix is charged a commitment fee ranging from 0.25% to 0.50% per year on the daily amount of the unused portions of the commitments under the Revolving Facility. As of September 30, 2020, the Company had an outstanding debt balance of $8.0 million attributable to the Revolving Facility. The undrawn balance of $17 million is available to fund working capital and for other general corporate purposes, including the financing of permitted acquisitions, investments and restricted payments, subject to the conditions contained in the Credit Agreement. As of September 30, 2020, the Company has incurred $19 thousand and $62 thousand of commitment fees, and $72 thousand and $214 thousand of interest expense, for the three- and nine-month periods ended on September 30, 2020, respectively. As of September 30, 2020, the estimated fair value of the Credit Facilities approximated their carrying value and the Company was in compliance with all covenants in the Credit Agreement.

Preferred Stock

Preferred Stock	9 Months Ended
	Sep. 30, 2020
Equity [Abstract]
Preferred Stock	8. Preferred Stock On February 20, 2019, (the “Original Issuance Date” or “Closing Date”), Zix consummated a private placement pursuant to an investment agreement with an investment fund managed by True Wind Capital and issued an aggregate of $100 million of shares of convertible Preferred Stock (as defined below) at a price of $1,000 per share (the “Stated Value”). 64,914 shares of Series A Convertible Preferred Stock (the “Series A Preferred Stock”) were issued for proceeds of $62.7 million, net of issuance costs of $2.3 million, and 35,086 shares of Series B Convertible Preferred Stock (the “Series B Preferred Stock” and, together with the Series A Preferred Stock, the “Preferred Stock”) were issued for proceeds of $33.9 million, net of issuance costs of $1.2 million. The Preferred Stock is classified outside of stockholders’ equity in temporary equity because the shares contain certain redemption features that require redemption upon a change in control. The Series A Preferred Stock can be immediately converted to common stock. On June 5, 2019, Shareholders approved the conversion of the outstanding shares of Series B Preferred Stock into shares of Series A Preferred Stock. Each share of Series B Preferred Stock was converted into the number of shares of Series A Preferred Stock equal to the liquidation preference of such share of Series B Preferred Stock divided by the accreted value of a share of Series A Preferred Stock on the date of conversion plus cash in lieu of fractional shares. On June 6, 2019, all the outstanding shares of Series B Preferred Stock were converted into 35,292 shares of Series A Preferred Stock. As of September 30, 2020, no shares of Series B Preferred Stock are outstanding. The conversion option of the Series A Preferred Stock was determined to have a beneficial conversion feature valued at $2.5 million, excluding the additional beneficial conversion feature accrued for the deemed dividend and was recorded to additional paid-in capital and as a discount to the Series A Preferred Stock. This resulting discount was immediately amortized as the Series A Preferred Stock has no set redemption date but is currently convertible. Dividends The Stated Value of the Series A Preferred Stock accretes at a fixed rate of 8% per annum, compounded quarterly (“Series A Preferred Dividend”). Apart from the Series A Preferred Dividend, the holders of Series A Preferred Stock are also entitled to receive any dividends paid on our common stock on an "as converted" basis. No dividend may be paid on our common stock until such dividend is paid on the Series A Preferred Stock. All calculations of the Accreted Value (as defined below) of Series A Preferred Stock will be computed on the basis of a 360-day year of twelve 30-day months. As of September 30, 2020, the accretion of the Stated Value of Series A Preferred Stock is valued at $12.7 million. Voting Rights Holders of Series A Preferred Stock are entitled to vote, together with the holders of common stock on all matters submitted to a vote of the holders of our common stock. Each holder of Series A Preferred Stock shall be entitled to the number of votes equal to the largest number of whole shares of common stock into which all shares of Series A Preferred Stock held by such holder could be converted. The vote or consent of the holders of at least a majority of the shares of Series A Preferred Stock outstanding will be necessary for effecting or validating any of the following actions: (i) any amendment, alteration or repeal of Zix’s Articles of Incorporation or Series A Certification of Designations that would adversely affect the rights, preferences, privileges or power of the Series A Preferred Stock; (ii) any amendment or alteration to Zix’s Articles of Incorporation or any other action to authorize or create, or increase the number of authorized or issued shares of capital stock of the Company convertible into shares of, or ranking senior to, or on a parity basis with, the Series A Preferred Stock as to dividend rights or liquidation rights; (iii) the issuance of shares of Series A Preferred Stock after the Original Issuance Date other than in connection with the conversion of Series B Preferred Stock that was issued on the Original Issuance Date; (iv) any action that would cause the Company to cease to be treated as a domestic corporation for U.S. federal income tax purposes; and (v) the incurrence of any indebtedness of the Company that would cause Zix to exceed a specified leverage ratio. Liquidation Preference The Series A Preferred Stock has a liquidation preference equal to the greater of (i) the Stated Value per share as it has accreted as of such date (the “Accreted Value”) and (ii) the amount such holder would have received if the Series A Preferred Stock had converted into common stock immediately prior to such liquidation. Conversion At any time, each Series A Preferred Stock holder may elect to convert each share of such holders’ then-outstanding Series A Preferred Stock into (i) the number of shares of common stock equal to the product of (a) the Accreted Value with respect to such share on the conversion date multiplied by (b) the conversion rate (currently166.11) as of the applicable conversion date divided by (c) 1,000 plus (ii) cash in lieu of fractional shares. Optional Redemption by Zix At any time after the fourth anniversary of the Closing Date, Zix may redeem the Series A Preferred Stock for an amount per share of Series A Preferred Stock equal to the Accreted Value per share of the Series A Preferred Stock to be redeemed as of the applicable redemption date multiplied by 1.50.

Revenue from Contracts with Cus

Revenue from Contracts with Customers	9 Months Ended
	Sep. 30, 2020
Revenue From Contract With Customer [Abstract]
Revenue from Contracts with Customers	9. Revenue from Contracts with Customers Accounting policies Our Company provides message security solutions as subscription services in which we recognize revenue as our services are rendered. Historically, our contracts have typically been one to three year contracts billed annually. We are increasingly moving toward a monthly billing model. This shift has been largely driven by our recent acquisition activity, including AppRiver. We exclude from the measurement of the transaction price all taxes assessed by a governmental authority that are both imposed on and concurrent with a specific revenue-producing transaction and collected by our Company from a customer (e.g., sales, use, value added, and some excise taxes). Disaggregation of Revenue We operate as a single In the nine months ended 30, 2020, we recorded revenue for our services Contract balances Our contract assets include our accounts receivables, discussed above in Footnote 5 “Receivables, net”, and the deferred cost associated with commissions earned by our sales team on securing new, add-on, and renewal contract orders. During the three and nine months ended September 30, 2020, we increased our noncurrent deferred contract asset by $1.3 million and $3.4 million, respectively, resulting from commissions earned by our sales team during the three and nine months ended September 30, 2020. We also amortized $944 thousand and $2.7 million of deferred cost, respectively as a selling and marketing expense in the related periods. Our deferred cost asset is assessed for impairment on a periodic basis. There were no impairment losses recognized on deferred contract cost assets for the three and nine months ended September 30, 2020. Our contract liabilities consist of deferred revenue representing future customer services that have been billed and collected. The $923 thousand decrease to our net deferred revenue in the nine months ended 30, 2020, is related to the timing of orders and payments in the normal course of business and our continued trend toward monthly subscriptions. Performance obligations As of September 30, 2020, the aggregate amount of the transaction prices allocated to remaining service performance obligations, which represents the transaction price of firm orders less inception to date revenue, was $85.0 million. We expect to recognize approximately $26.7 million of revenue related to this backlog during the remainder of 2020, $41.7 million in 2021, and $16.5 million in periods thereafter. Approximately $26.6 million of our $54.8 million revenue recognized in the three months ended September 30, 2020, was included in our performance obligation balance at the beginning of the period. Approximately $54.1 million of our $160.6 million recognized in the nine months ended September 30, 2020, was included in our performance obligation balance at the beginning of the period.

Earnings (Loss) Per Share and P

Earnings (Loss) Per Share and Potential Dilution	9 Months Ended
	Sep. 30, 2020
Earnings Per Share [Abstract]
Earnings (Loss) Per Share and Potential Dilution	10. Earnings (Loss) Per Share and Potential Dilution Basic earnings (loss) per share are computed using the weighted average number of common shares outstanding for the applicable period under the Treasury Stock method. The dilutive effect of potential common shares outstanding is included in diluted earnings (loss) per share. The computations for basic and diluted earnings (loss) per share for the three and nine months ended September 30, 2020 and 2019, respectively, are as follows: Three Months Ended September 30, Nine Months Ended September 30, 2020 2019 2020 2019 Basic weighted average common shares 54,999,114 53,148,078 53,933,721 52,965,163 Effect of dilutive securities: Employee and director stock options — — — — Restricted Stock — — — — RSUs — — — — Performance RSUs — — — — Performance Stock — — — — Series A Preferred Shares — — — — Series B Preferred Shares — — — — Dilutive weighted average common shares 54,999,114 53,148,078 53,933,721 52,965,163 During each of the three and nine months ended September 30, 2019 and 2020, potential common shares of all securities were excluded from the calculation of diluted loss per share because the awards were anti-dilutive.

Commitments and Contingencies

Commitments and Contingencies	9 Months Ended
	Sep. 30, 2020
Commitments And Contingencies Disclosure [Abstract]
Commitments and Contingencies	11. Commitments and Contingencies We have not entered into any material, non-cancelable purchase commitments at September 30, 2020. Claims and Proceedings We are from time to time involved in legal claims, litigation, and other legal proceedings. Although we may incur significant expenses in those matters, we expect no material adverse effect on our operations or financial results from current or concluded legal proceedings.

Fair Value Measurements

Fair Value Measurements	9 Months Ended
	Sep. 30, 2020
Fair Value Disclosures [Abstract]
Fair Value Measurements	12. Fair Value Measurements FASB guidance regarding fair value measurement establishes a three-tier fair value hierarchy, which prioritizes the inputs used in measuring fair value. These tiers include: Level 1, defined as observable inputs such as quoted prices in active markets for identical assets or liabilities; Level 2, defined as inputs other than quoted prices for similar assets and liabilities in active markets that are either directly or indirectly observable; and Level 3, defined as unobservable inputs for which little or no market data exists, therefore requiring an entity to develop its own assumptions. For certain of the Company’s financial instruments, including cash and cash equivalents, trade receivables, and accounts payable, the fair values approximate the carrying values due to the short-term maturities of these instruments. The carrying values of other current assets and accrued expenses are also not recorded at fair value, but approximate fair values primarily due to their short-term nature.

Goodwill

Goodwill	9 Months Ended
	Sep. 30, 2020
Goodwill And Intangible Assets Disclosure [Abstract]
Goodwill	13. Goodwill The following is a summary of the changes in the carrying amount of goodwill for the nine-month period ended September 30, 2020 and 2019: Nine Months Ended September 30, (In thousands) 2020 2019 Opening balance $ 171,209 $ 13,783 Additions — 160,574 Acquisition adjustments — — Effect of currency translation adjustment (279 ) — Goodwill $ 170,930 $ 174,357 Our 2019 acquisitions of AppRiver and DeliverySlip resulted in the increase to our goodwill in the nine months ended September 30, 2019. S . We evaluate goodwill for impairment annually in the fourth quarter, or when there is a reason to believe that the value has been diminished or impaired. There were no impairments to goodwill during the periods presented above.

Other Comprehensive Loss

Other Comprehensive Loss	9 Months Ended
	Sep. 30, 2020
Other Comprehensive Income Loss Tax [Abstract]
Other Comprehensive Loss	14. Other Comprehensive Loss The assets and liabilities of international subsidiaries are translated from the respective local currency to the U.S. dollar using exchange rates at the balance sheet date. Our Consolidated Statement of Comprehensive Loss of international subsidiaries are translated from the local currency to the U.S. dollar using average exchange rates for the period. Related translation adjustments are recorded as a component of the accumulated other comprehensive income (loss). We are exposed to fluctuations in the foreign currency exchange rates as a result of our net investments and operations in Canada, United Kingdom, Switzerland and Spain. For the three and nine months ended September 30, 2020, movements in currency exchange rates and the related impact on the translation of the balance sheets of our foreign subsidiaries was the primary cause of our foreign currency translation gain of $493 thousand and loss of $118 thousand, respectively.

Income Taxes

Income Taxes	9 Months Ended
	Sep. 30, 2020
Income Tax Disclosure [Abstract]
Income Taxes	15. Income Taxes The operating losses incurred by the Company’s U.S. operations in past years and the resulting net operating losses for U.S. Federal tax purposes are subject to a $23.0 million reserve. Any reduction to this $23.0 million valuation allowance is based on an assessment of future utilization following accounting guidance, which relies largely on historical earnings. Using this methodology, and updating the future taxable earnings estimates based on first, second and third quarter 2020 actual earnings, the Company believes the deferred tax asset allowance as of December 31, 2019, will remain unchanged at December 31, 2020. For this reason, the Company has recognized its first, second and third quarter 2020 federal deferred tax provision in full. If in prospective periods we conclude our future U.S. federal taxable estimate established at the end of the year will exceed the prior year estimate, the Company will offset its federal deferred tax provision by reducing its valuation allowance by an equal amount, thereby eliminating from its deferred tax provision federal taxes from the Company’s financial statements. The Company will continue to reevaluate the need for its valuation allowance each quarter, following the same assessment methodology described above. An increase or decrease to our valuation allowance could have a significant impact on operating results for each period that it becomes more likely than not that an additional portion of our deferred tax assets will or will not be realized.

Acquisitions

Acquisitions	9 Months Ended
	Sep. 30, 2020
Business Combinations [Abstract]
Acquisitions	16. Acquisitions Acquisition of DeliverySlip On May 7, 2019, the Company acquired certain assets of Cirius Messaging Inc. (“Seller”) and its wholly owned subsidiary DeliverySlip Inc.(“DeliverySlip”), related to the DeliverySlip product for a total purchase price of $13.8 million, including cash consideration of $11.4 million and a contingent consideration with an estimated fair value of $2.3 million at the acquisition date. The contingent consideration was paid in full upon the completion of certain agreed upon requirements and a related $0.2 million loss on the contingent consideration was recognized in the year ended December 31, 2019. Included in the cash consideration, a holdback amount of $1.5 million was transferred to an escrow agent for the satisfaction of the Seller’s indemnity and other obligations under the purchase agreement. The acquisition was partially financed with proceeds of $10 million from the Delayed Draw Term Loan Facility. The purchase of DeliverySlip expanded the Company’s product offering including email encryption, e-signatures and secure file solutions. The Company incurred $1.2 million in acquisition-related costs with respect to the DeliverySlip acquisition, which were recorded within operating expenses during the twelve months ended December 31, 2019. Prior to the acquisition, approximately 90% of DeliverySlip’s revenue was generated from AppRiver Canada Inc, which became a subsidiary of the Company upon closing of the AppRiver acquisition (as described below). Revenue from additional acquired customers of DeliverySlip for the three and nine months ended September 30, 2020 were immaterial. We accounted for the acquisition as the purchase of a business and recorded the excess purchase price as goodwill. The majority of the goodwill balance is expected to be deductible for tax purposes. The intangible asset we acquired from DeliverySlip is technology which we are amortizing over 6 years. The results of operations and the provisional fair values of the acquired assets and liabilities have been included in the accompanying condensed consolidated financial statements since our DeliverySlip acquisition on May 7, 2019. The following table summarizes the estimated fair value of acquired assets and liabilities: (In thousands) Estimated Fair Value Assets: Technology $ 4,200 Goodwill 9,603 Total assets 13,803 Liabilities: Deferred revenue $ 52 Total liabilities 52 Net assets recorded $ 13,751 Acquisition of AppRiver Companies On February 20, 2019, Zix acquired 100% of the equity interest of AR Topco, LLC and its subsidiaries, including AppRiver LLC (“AppRiver” and collectively, the “AppRiver Companies”), for a total purchase price of $276.4 million, including cash consideration of $271.8 million, net of cash acquired , and subject to a customary working capital adjustment. This acquisition complements our strategy to accelerate our offerings into the cloud at the point of initial cloud application purchase and expand our customer base. We financed the acquisition with proceeds from (1) cash on hand, (2) the proceeds from the Term Loan, and (3) a private placement with an investment fund managed by True Wind Capital consisting of (i) 64,914 newly issued shares of Series A Convertible Preferred Stock, $1.00 par value per share, and (ii) 35,086 newly issued shares of Series B Convertible Preferred Stock, $1.00 par value per share in exchange for cash consideration in an aggregate amount of $100 million (which was reduced by $3 million in True Wind Capital’s costs that were reimbursed by the Company). AppRiver is a channel-first provider of cloud-based cyber security and productivity services, offering web protection, email encryption, secure archiving, and email continuity solutions. AppRiver also provides Microsoft Office 365 and Secure Hosted Exchange services, which serve as an effective lead generation tool for AppRiver’s solutions. The acquisition of AppRiver can accelerate our offerings into the cloud at the point of initial cloud application purchase. Because AppRiver currently services over 60,000 worldwide customers using a network of 4,500 Managed Service Providers, this acquisition can help us expand our customer base. The Company incurred $10.8 million in acquisition-related costs which included $1.1 million, $9.6 million and $41 thousand recorded within the operating expenses for the twelve months ended December 31, 2018, December 31, 2019 and the nine months ended September 30, 2020, respectively. Revenue from AppRiver was $35.2 and $101.8 million for the three and nine months ended September 30, 2020, respectively, and due to the continued integration of the combined businesses, it was impracticable to determine earnings attributable to AppRiver. We accounted for the acquisition as the purchase of a business and recorded the excess purchase price as goodwill. The majority of the goodwill balance is expected to be deductible for tax purposes. The intangible assets we acquired from AppRiver consist of customer relationships, vendor relationships, trademarks/names, and internally developed software, which we are amortizing over 8 years, 3 years, 10 years, and 5-6 years, respectively. The results of operations and the provisional fair values of the acquired assets and liabilities have been included in the accompanying condensed consolidated financial statements since our AppRiver acquisition on February 20, 2019. The following table summarizes the estimated fair value of acquired assets and liabilities: (In thousands) Estimated Fair Value Assets: Current assets $ 12,200 Property and equipment 3,235 ROU assets 8,778 Customer relationships 91,000 Vendor relationships 1,000 Trademark/Names 4,400 Deferred tax assets 3,453 Internally developed software 41,100 Goodwill 147,518 Total assets 312,684 Liabilities: Current liabilities $ 13,378 Deferred revenue 12,424 Operating lease liabilities 5,738 Finance lease liabilities 3,440 Total liabilities 34,980 Net assets recorded $ 277,704 Pro Forma Financial Information (Unaudited) The following unaudited pro forma financial information presents the combined results of operations for the three and nine month periods ending September 30, 2020 and 2019, respectively, as though the DeliverySlip and AppRiver acquisitions that occurred during the reporting period had occurred as of the beginning of the period presented, with adjustments, such as amortization expense of intangible assets and acquisition-related transaction costs, to give effect to pro forma events that are directly attributable to the acquisitions. These unaudited pro forma results are presented for information purposes only and are not necessarily indicative of what the actual results of operations of the combined company would have been if the respective acquisitions had occurred at the beginning of the period presented, nor are they indicative of future results of operations: Three Months Ended September 30, Nine Months Ended September 30, (In thousands, except per share data) 2020 2019 2020 2019 Revenues $ 54,925 $ 48,899 $ 160,865 $ 143,146 Net income (624 ) 624 (2,960 ) 1,328 Basic income (loss) per share attributed to common shareholders $ (0.05 ) $ (0.03 ) $ (0.14 ) $ (0.15 ) Diluted income (loss) per share attributed to common shareholders $ (0.05 ) $ (0.03 ) $ (0.14 ) $ (0.15 )

Subsequent Events

Subsequent Events	9 Months Ended
	Sep. 30, 2020
Subsequent Events [Abstract]
Subsequent Events	17. Subsequent Events Acquisition of CloudAlly On November 5, 2020, Zix acquired 100% of the equity interest of CloudAlly Ltd. (“CloudAlly”) and its parent holding company. The aggregate purchase price is up to $30 million in cash, subject to certain amounts to be held in escrow for indemnification obligations, outstanding indebtedness of CloudAlly retired at closing, certain accrued items and unpaid transaction expenses, and subject to a customary working capital adjustment. Also on November 5, 2020, the Company amended its Credit Agreement to, among other things, borrow an incremental $35.0 million term loan (the “Incremental Term Loan”). The Incremental Term Loan has the same interest rate, maturity date, amortization schedule, collateral and other terms as the existing Term Loan and Delayed Draw Term Loan. The Company used the proceeds of the Incremental Term Loan to fund the acquisition of CloudAlly and to repay all existing borrowings under the Revolving Facility. Founded in 2011, CloudAlly, based in Israel, is a pioneer of enterprise-grade, software-as-a-service (SaaS) cloud backup and recovery solutions. The company offers a robust suite of award-winning, ISO 27001 certified and GDPR/HIPAA compliant solutions for Microsoft Office 365, Google Workspace (formerly G Suite), SharePoint, OneDrive, Salesforce, Box and Dropbox. CloudAlly is a channel-first provider, serving more than 5,000 customers, 500,000 users and supported by 300 Managed Service Provider (MSP) partners.

Recent Accounting Standards a_2

Recent Accounting Standards and Pronouncements (Policies)	9 Months Ended
	Sep. 30, 2020
Accounting Changes And Error Corrections [Abstract]
Income Taxes	Income Taxes In December 2019, the FASB issued Accounting Standard Update No. 2019-12, Income Taxes (Topic 740): Simplifying the Accounting for Income Taxes (ASU 2019-12), which simplifies the accounting for income taxes. This guidance will be effective for us in the first quarter of 2021 on a prospective basis, and early adoption is permitted. We are currently evaluating the impact of the new guidance on our consolidated financial statements.

Stock- Based Awards and Stock_2

Stock- Based Awards and Stock-Based Employee Compensation Expense (Tables)	9 Months Ended
	Sep. 30, 2020
Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]
Summary of All Stock Option Transactions	The following is a summary of all stock option transactions during the three months ended September 30, 2020: Options Weighted Average Exercise Price Weighted Average Remaining Contractual Term (Yrs) Outstanding at June 30, 2020 742,010 $ 4.09 5.01 Granted at market price — — Cancelled or expired — — Exercised — — Outstanding at September 30, 2020 742,010 $ 4.09 4.76 Options exercisable at September 30, 2020 654,510 $ 3.57 4.13
Summary of Restricted Stock Activity	The following is a summary of Restricted Stock activity during the three months ended September 30, 2020: Restricted Shares Weighted Average Fair Value Non-vested restricted stock at June 30, 2020 2,090,745 $ 7.36 Granted at market price 30,500 6.12 Vested (80,574 ) 6.85 Cancelled (19,967 ) 7.53 Non-vested restricted stock at September 30, 2020 2,020,704 $ 7.36
Summary of All Restricted Stock Unit Activity	The following is a summary of all RSU activity during the three months ended September 30, 2020: Restricted Stock Units Weighted Average Fair Value Non-vested restricted stock units at June 30, 2020 153,099 $ 8.62 Granted at market price — — Vested (16,996 ) 9.13 Cancelled — — Non-vested restricted stock units at September 30, 2020 136,103 $ 8.56
Summary of All Performance RSU Activity	The following is a summary of all Performance RSU activity during the three months ended September 30, 2020: Performance RSUs Weighted Average Fair Value Non-vested performance RSUs at June 30, 2020 44,349 $ 8.84 Granted at market price — — Vested — — Forfeited — — Non-vested performance RSUs at September 30, 2020 44,349 $ 8.84
Summary of All Performance Stock Activity	The following is a summary of all Performance Stock activity during the three months ended September 30, 2020: Performance Stock Weighted Average Fair Value Non-vested performance stock at June 30, 2020 691,852 $ 7.52 Granted at market price — — Vested — — Forfeited — — Non-vested performance stock at September 30, 2020 691,852 $ 7.52
Summary of Total Stock-based Employee Compensation Expense Resulting from Stock Options, Restricted Stock, RSUs, Performance RSUs, and Performance Stock	For the three- and nine-month periods ended September 30, 2020, the total stock-based employee compensation expense resulting from stock options, Restricted Stock, RSUs, Performance RSUs and Performance Stock was recorded to the following line items of the Company’s condensed consolidated statements of income: (In thousands) Three Months Ended September 30, 2020 Nine Months Ended September 30, 2020 Cost of revenues $ 97 $ 1,105 Research and development 433 1,184 Selling, general and administrative 1,578 5,060 Stock-based compensation expense $ 2,108 $ 7,349

Supplemental Cash Flow Inform_2

Supplemental Cash Flow Information (Tables)	9 Months Ended
	Sep. 30, 2020
Supplemental Cash Flow Elements [Abstract]
Supplemental Cash Flow Information Relating to Taxes and Non-Cash Activities	Supplemental cash flow information relating to taxes and non-cash activities: Nine Months Ended September 30, (In thousands) 2020 2019 Cash income tax payments $ 217 $ 338 Cash paid for interest 5,812 6,696 Non-cash investing and financing activities: Accrued and deemed dividends on Series A preferred stock 6,714 5,610 Accrued and deemed dividends on Series B preferred stock — 2,284

Receivables, Net (Tables)

Receivables, Net (Tables)	9 Months Ended
	Sep. 30, 2020
Receivables [Abstract]
Summary of Net Receivables	(In thousands) September 30, 2020 December 31, 2019 Gross accounts receivables $ 28,245 $ 21,193 Allowance for credit losses $ (304 ) $ — Allowance for returns and doubtful accounts — (265 ) Unpaid portion of deferred revenue (12,613 ) (10,847 ) Note receivable 458 458 Allowance for note receivable (458 ) (458 ) Receivables, net $ 15,328 $ 10,081

Leases (Tables)

Leases (Tables)	9 Months Ended
	Sep. 30, 2020
Leases [Abstract]
Schedule of Components of Lease Costs	The components of lease costs are as follows: Three Months Ended September 30, Nine Months Ended September 30, (In thousands) 2020 2020 Finance lease costs: Amortization of right-of-use asset $ 261 $ 949 Interest on lease liabilities 18 71 Operating lease costs 785 2,658 Short-term lease costs 493 1,490 Variable lease costs 165 649 Total lease costs $ 1,722 $ 5,817
Schedule of Supplemental Cash Flow Information Related to Leases	Supplemental cash flow information related to leases are as follows: Nine Months Ended September 30, (In thousands) 2020 Cash paid for amounts included in the measurement of lease liabilities: Operating cash flows from operating leases $ 2,897 Operating cash flows from finance leases 71 Financing cash flows from finance leases 1,086 Right-of-use assets obtained in exchange for lease obligations: Operating leases 523 Finance leases —
Schedule of Supplemental Balance Sheet Information Related to Lease	Supplemental balance sheet information related to lease are as follows: September 30, (In thousands) Balance Sheet Classification 2020 Operating Leases Operating lease right-of-use assets Operating lease assets $ 8,332 Total operating lease assets $ 8,332 September 30, (In thousands) Balance Sheet Classification 2020 Finance Leases Finance lease right-of-use assets $ 3,362 Accumulated depreciation - finance leases (2,261 ) Finance lease right-of-use assets, net Property and equipment, net $ 1,101
Schedule of Weighted Average Remaining Lease Term and Weighted Average Discount Rate	Weighted average remaining lease term and weighted average discount rate are as follows: Weighted Average Remaining Lease Term (Years) Operating leases 4.06 Finance leases 1.53 Weighted Average Discount Rate Operating leases 4.95 % Finance leases 6.14 %
Schedule of Maturities of Lease Liabilities	Maturities of lease liabilities are as follows: Payments Due by Period - Year Ending December 31, 2020 (In thousands) Total Year 1 (1) Years 2 & 3 Years 4 & 5 Beyond 5 Years Operating leases $ 10,282 $ 735 $ 4,904 $ 3,870 $ 773 Less imputed interest (974 ) Total $ 9,308 Finance leases $ 1,008 $ 266 $ 736 $ 6 $ — Less imputed interest (40 ) Total $ 968 (1)

Long-term Debt (Tables)

Long-term Debt (Tables)	9 Months Ended
	Sep. 30, 2020
Term Loan [Member]
Schedule of Future Scheduled Principal Payments	Future principal payments under the Term Loan as of September 30, 2020, are as follows: (In thousands) Year Ending December 31, Amount 2020 $ 438 2021 1,750 2022 1,750 2023 1,750 2024 166,688 Total $ 172,376
Senior Secured Delayed Draw Term Loan Facility [Member]
Schedule of Future Scheduled Principal Payments	Future principal payments under the Delayed Draw Term Loan Facility as of September 30, 2020 are as follows: (In thousands) Year Ending December 31, Amount 2020 $ 25 2021 100 2022 100 2023 100 2024 9,550 Total $ 9,875

Earnings (Loss) Per Share and_2

Earnings (Loss) Per Share and Potential Dilution (Tables)	9 Months Ended
	Sep. 30, 2020
Earnings Per Share [Abstract]
Computations of Basic and Diluted Earnings (Loss) Per Share	The computations for basic and diluted earnings (loss) per share for the three and nine months ended September 30, 2020 and 2019, respectively, are as follows: Three Months Ended September 30, Nine Months Ended September 30, 2020 2019 2020 2019 Basic weighted average common shares 54,999,114 53,148,078 53,933,721 52,965,163 Effect of dilutive securities: Employee and director stock options — — — — Restricted Stock — — — — RSUs — — — — Performance RSUs — — — — Performance Stock — — — — Series A Preferred Shares — — — — Series B Preferred Shares — — — — Dilutive weighted average common shares 54,999,114 53,148,078 53,933,721 52,965,163

Goodwill (Tables)

Goodwill (Tables)	9 Months Ended
	Sep. 30, 2020
Goodwill And Intangible Assets Disclosure [Abstract]
Schedule of Changes in Carrying Amount of Goodwill	The following is a summary of the changes in the carrying amount of goodwill for the nine-month period ended September 30, 2020 and 2019: Nine Months Ended September 30, (In thousands) 2020 2019 Opening balance $ 171,209 $ 13,783 Additions — 160,574 Acquisition adjustments — — Effect of currency translation adjustment (279 ) — Goodwill $ 170,930 $ 174,357

Acquisitions (Tables)

Acquisitions (Tables)	9 Months Ended
	Sep. 30, 2020
Unaudited Pro Forma Financial Information	The following unaudited pro forma financial information presents the combined results of operations for the three and nine month periods ending September 30, 2020 and 2019, respectively, as though the DeliverySlip and AppRiver acquisitions that occurred during the reporting period had occurred as of the beginning of the period presented, with adjustments, such as amortization expense of intangible assets and acquisition-related transaction costs, to give effect to pro forma events that are directly attributable to the acquisitions. These unaudited pro forma results are presented for information purposes only and are not necessarily indicative of what the actual results of operations of the combined company would have been if the respective acquisitions had occurred at the beginning of the period presented, nor are they indicative of future results of operations: Three Months Ended September 30, Nine Months Ended September 30, (In thousands, except per share data) 2020 2019 2020 2019 Revenues $ 54,925 $ 48,899 $ 160,865 $ 143,146 Net income (624 ) 624 (2,960 ) 1,328 Basic income (loss) per share attributed to common shareholders $ (0.05 ) $ (0.03 ) $ (0.14 ) $ (0.15 ) Diluted income (loss) per share attributed to common shareholders $ (0.05 ) $ (0.03 ) $ (0.14 ) $ (0.15 )
Delivery Slip Inc. [Member]
Summary of Estimated Fair Value of Acquired Assets and Liabilities	The following table summarizes the estimated fair value of acquired assets and liabilities: (In thousands) Estimated Fair Value Assets: Technology $ 4,200 Goodwill 9,603 Total assets 13,803 Liabilities: Deferred revenue $ 52 Total liabilities 52 Net assets recorded $ 13,751
AppRiver Companies [Member]
Summary of Estimated Fair Value of Acquired Assets and Liabilities	The following table summarizes the estimated fair value of acquired assets and liabilities: (In thousands) Estimated Fair Value Assets: Current assets $ 12,200 Property and equipment 3,235 ROU assets 8,778 Customer relationships 91,000 Vendor relationships 1,000 Trademark/Names 4,400 Deferred tax assets 3,453 Internally developed software 41,100 Goodwill 147,518 Total assets 312,684 Liabilities: Current liabilities $ 13,378 Deferred revenue 12,424 Operating lease liabilities 5,738 Finance lease liabilities 3,440 Total liabilities 34,980 Net assets recorded $ 277,704

Stock- Based Awards and Stock_3

Stock- Based Awards and Stock-Based Employee Compensation Expense - Additional Information (Detail) - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2020	Jun. 30, 2020	Sep. 30, 2019
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Options outstanding	742,010	742,010
Shares of common stock available for grant	2,377,521
Options, options exercisable	654,510
Deferred tax assets, tax deferred expense compensation and benefits employee compensation	$ 1,400		$ 775
Total unrecognized stock-based compensation related to non-vested stock-based compensation awards	$ 16,400
The number of years over which expense is expected to be recognized	1 year 11 months 26 days
Restricted Stock [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Non-vested stock	2,020,704	2,090,745
Restricted Stock Units (RSUs) [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Non-vested stock	136,103	153,099
Non-vested Performance Stock Awards [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Non-vested stock	691,852	691,852
Non-vested Performance RSUs [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Non-vested stock	44,349	44,349
Employee and Director Stock Options [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Options outstanding	742,010
Options, options exercisable	642,010
Aggregate intrinsic value of options outstanding	$ 1,500
Aggregate intrinsic value of options exercisable	$ 1,500

Stock- Based Awards and Stock_4

Stock- Based Awards and Stock-Based Employee Compensation Expense - Summary of All Stock Option Transactions (Detail) - $ / shares	3 Months Ended
	Sep. 30, 2020	Jun. 30, 2020
Share Based Compensation Arrangement By Share Based Payment Award Options Outstanding Roll Forward
Options, Outstanding, Beginning Balance	742,010
Options, Granted at market price	0
Options, Cancelled or expired	0
Options, Exercised	0
Options, Outstanding Ending Balance	742,010	742,010
Options, Options Exercisable	654,510
Weighted Average Exercise Price, Outstanding, Beginning Balance	$ 4.09
Weighted Average Exercise Price, Granted at market price	0
Weighted Average Exercise Price, Cancelled or expired	0
Weighted Average Exercise Price, Exercised	0
Weighted Average Exercise Price, Outstanding, Ending Balance	4.09	$ 4.09
Weighted Average Exercise Price, Options Exercisable	$ 3.57
Weighted Average Remaining Contractual Term, Outstanding	4 years 9 months 3 days	5 years 3 days
Weighted Average Remaining Contractual Term, Options exercisable	4 years 1 month 17 days

Stock- Based Awards and Stock_5

Stock- Based Awards and Stock-Based Employee Compensation Expense - Summary of Restricted Stock Activity (Detail) - Restricted Stock [Member]	3 Months Ended
	Sep. 30, 2020$ / sharesshares
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Shares, Non-vested, Beginning balance | shares	2,090,745
Shares, Granted at market price | shares	30,500
Shares, Vested | shares	(80,574)
Shares, Cancelled | shares	(19,967)
Shares, Non-vested, Ending balance | shares	2,020,704
Weighted Average Fair Value, Non-vested, Beginning balance | $ / shares	$ 7.36
Weighted Average Fair Value, Granted at market price | $ / shares	6.12
Weighted Average Fair Value, Vested | $ / shares	6.85
Weighted Average Fair Value, Cancelled | $ / shares	7.53
Weighted Average Fair Value, Non-vested, Ending balance | $ / shares	$ 7.36

Stock- Based Awards and Stock_6

Stock- Based Awards and Stock-Based Employee Compensation Expense - Summary of All Restricted Stock Unit Activity (Detail) - Restricted Stock Units (RSUs) [Member]	3 Months Ended
	Sep. 30, 2020$ / sharesshares
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Shares, Non-vested, Beginning balance | shares	153,099
Shares, Granted at market price | shares	0
Shares, Vested | shares	(16,996)
Shares, Cancelled | shares	0
Shares, Non-vested, Ending balance | shares	136,103
Weighted Average Fair Value, Non-vested, Beginning balance | $ / shares	$ 8.62
Weighted Average Fair Value, Granted at market price | $ / shares	0
Weighted Average Fair Value, Vested | $ / shares	9.13
Weighted Average Fair Value, Cancelled | $ / shares	0
Weighted Average Fair Value, Non-vested, Ending balance | $ / shares	$ 8.56

Stock- Based Awards and Stock_7

Stock- Based Awards and Stock-Based Employee Compensation Expense - Summary of All Performance RSU Activity (Detail) - Non-vested Performance RSUs [Member]	3 Months Ended
	Sep. 30, 2020$ / sharesshares
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Shares, Non-vested, Beginning balance | shares	44,349
Shares, Granted at market price | shares	0
Shares, Vested | shares	0
Shares, Cancelled | shares	0
Shares, Non-vested, Ending balance | shares	44,349
Weighted Average Fair Value, Non-vested, Beginning balance | $ / shares	$ 8.84
Weighted Average Fair Value, Granted at market price | $ / shares	0
Weighted Average Fair Value, Vested | $ / shares	0
Weighted Average Fair Value, Cancelled | $ / shares	0
Weighted Average Fair Value, Non-vested, Ending balance | $ / shares	$ 8.84

Stock- Based Awards and Stock_8

Stock- Based Awards and Stock-Based Employee Compensation Expense - Summary of All Performance Stock Activity (Details) - Performance Stock [Member]	3 Months Ended
	Sep. 30, 2020$ / sharesshares
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Shares, Non-vested, Beginning balance | shares	691,852
Shares, Granted at market price | shares	0
Shares, Vested | shares	0
Shares, Cancelled | shares	0
Shares, Non-vested, Ending balance | shares	691,852
Weighted Average Fair Value, Non-vested, Beginning balance | $ / shares	$ 7.52
Weighted Average Fair Value, Granted at market price | $ / shares	0
Weighted Average Fair Value, Vested | $ / shares	0
Weighted Average Fair Value, Cancelled | $ / shares	0
Weighted Average Fair Value, Non-vested, Ending balance | $ / shares	$ 7.52

Stock- Based Awards and Stock_9

Stock- Based Awards and Stock-Based Employee Compensation Expense - Summary of Total Stock-based Employee Compensation Expense Resulting from Stock Options, Restricted Stock, RSUs, Performance RSUs, and Performance Stock (Detail) - USD ($) $ in Thousands	3 Months Ended	9 Months Ended
	Sep. 30, 2020	Sep. 30, 2020
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]
Stock-based compensation expense	$ 2,108	$ 7,349
Cost of Revenues [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]
Stock-based compensation expense	97	1,105
Research and Development [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]
Stock-based compensation expense	433	1,184
Selling, General and Administrative [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]
Stock-based compensation expense	$ 1,578	$ 5,060

Supplemental Cash Flow Inform_3

Supplemental Cash Flow Information - Supplemental Cash Flow Information Relating to Taxes and Non-Cash Activities (Detail) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Supplemental Cash Flow [Line Items]
Cash income tax payments			$ 217	$ 338
Cash paid for interest			5,812	6,696
Non-cash investing and financing activities:
Accrued and deemed dividends on preferred stock	$ 2,267	$ 2,090	6,714	7,894
Series A Convertible Preferred Stock [Member]
Non-cash investing and financing activities:
Accrued and deemed dividends on preferred stock			$ 6,714	5,610
Series B Convertible Preferred Stock [Member]
Non-cash investing and financing activities:
Accrued and deemed dividends on preferred stock				$ 2,284

Receivables, Net - Summary of N

Receivables, Net - Summary of Net Receivables (Detail) - USD ($) $ in Thousands	Sep. 30, 2020	Dec. 31, 2019
Accounts Notes And Loans Receivable Net Current [Abstract]
Gross accounts receivables	$ 28,245	$ 21,193
Allowance for credit losses	(304)
Allowance for returns and doubtful accounts		(265)
Unpaid portion of deferred revenue	(12,613)	(10,847)
Note receivable	458	458
Allowance for note receivable	(458)	(458)
Receivables, net	$ 15,328	$ 10,081

Receivables, Net - Additional I

Receivables, Net - Additional Information (Detail) $ in Thousands	9 Months Ended
	Sep. 30, 2020USD ($)
Receivables [Abstract]
Note receivable on a product line	$ 540
Date of note receivable, reserved	Sep. 30, 2020

Leases - Additional Information

Leases - Additional Information (Detail) $ in Thousands	3 Months Ended	9 Months Ended
	Sep. 30, 2020USD ($)	Sep. 30, 2020USD ($)
Lessee Lease Description [Line Items]
Lessee, operating lease, variable lease payment, terms and conditions		Variable lease costs consist primarily of variable common area maintenance, taxes, insurance, parking and utilities.
Lessee, operating lease, existence of option to extend		true
Operating lease liability	$ 109	$ 109
Lessee, operating lease, lease not yet commenced, term of contract	3 years	3 years
Write-off of right-of-use assets	$ 438
Write-off of right-of-use lease liability	570
other income	$ 132
Minimum [Member]
Lessee Lease Description [Line Items]
Lessee, operating lease, term of contract	1 year	1 year
Lessee, majority operating lease, term of contract		1 year
Maximum [Member]
Lessee Lease Description [Line Items]
Lessee, operating lease, term of contract	13 years	13 years
Lessee, majority operating lease, term of contract		7 years

Leases - Schedule of Components

Leases - Schedule of Components of Lease Costs (Detail) - USD ($) $ in Thousands	3 Months Ended	9 Months Ended
	Sep. 30, 2020	Sep. 30, 2020
Finance lease costs:
Amortization of right-of-use asset	$ 261	$ 949
Interest on lease liabilities	18	71
Operating lease costs	785	2,658
Short-term lease costs	493	1,490
Variable lease costs	165	649
Total lease costs	$ 1,722	$ 5,817

Leases - Schedule of Supplement

Leases - Schedule of Supplemental Cash Flow Information Related to Leases (Detail) - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019
Cash paid for amounts included in the measurement of lease liabilities:
Operating cash flows from operating leases	$ 2,897
Operating cash flows from finance leases	71
Financing cash flows from finance leases	1,086	$ 1,277
Right-of-use assets obtained in exchange for lease obligations:
Operating leases	$ 523

Leases - Schedule of Suppleme_2

Leases - Schedule of Supplemental Balance Sheet Information Related to Lease (Detail) - USD ($) $ in Thousands	Sep. 30, 2020	Dec. 31, 2019
Assets And Liabilities Lessee [Abstract]
Operating lease right-of-use assets	$ 8,332	$ 10,128
Operating Lease, Right-of-Use Asset, Statement of Financial Position [Extensible List]	zixi:OperatingLeaseAssetMember
Operating lease assets	$ 8,332	$ 10,128
Finance lease right-of-use assets	3,362
Accumulated depreciation - finance leases	(2,261)
Finance lease right-of-use assets, net	$ 1,101
Finance Lease, Right-of-Use Asset, Statement of Financial Position [Extensible List]	us-gaap:PropertyPlantAndEquipmentMember

Leases - Schedule of Weighted A

Leases - Schedule of Weighted Average Remaining Lease Term and Weighted Average Discount Rate (Detail)	Sep. 30, 2020
Lease Cost [Abstract]
Operating leases, weighted average remaining lease term (years)	4 years 21 days
Finance leases, weighted average remaining lease term (years)	1 year 6 months 10 days
Operating leases, weighted average discount rate	4.95%
Finance leases, weighted average discount rate	6.14%

Leases - Schedule of Maturities

Leases - Schedule of Maturities of Lease Liabilities (Detail) $ in Thousands	Sep. 30, 2020USD ($)
Operating Lease Liabilities Payments Due [Abstract]
Operating leases	$ 10,282
Less imputed interest	(974)
Total	9,308
Finance leases	1,008
Less imputed interest	(40)
Total	968
Operating lease payments due, Year 1	735
Operating lease payments due, Years 2 & 3	4,904
Operating lease payments due, Years 4 & 5	3,870
Operating lease payments due, beyond 5 years	773
Finance lease payments due, Year 1	266
Finance lease payments due, Years 2 & 3	736
Finance lease payments due, Years 4 & 5	$ 6

Long-term Debt - Additional Inf

Long-term Debt - Additional Information (Detail)	May 02, 2019USD ($)	Feb. 20, 2019USD ($)	Sep. 30, 2020USD ($)	Sep. 30, 2020USD ($)	Nov. 05, 2020USD ($)
Debt Instrument [Line Items]
Outstanding debt balance			$ 167,800,000	$ 167,800,000
Interest rate			4.39%
Unamortized debt issuance costs			$ 4,600,000	4,600,000
interest expense			72,000	214,000
Subsequent Event
Debt Instrument [Line Items]
Term loan					$ 35,000,000
Revolving Facility [Member]
Debt Instrument [Line Items]
Outstanding debt balance			8,000,000	$ 8,000,000
Senior Secured Delayed Draw Term Loan Facility [Member]
Debt Instrument [Line Items]
Delayed draw term loan facility fully drawn date				May 2, 2019
Principal outstanding			9,875,000	$ 9,875,000
Lines of credit, drawn amount	$ 10,000,000
Senior Secured Delayed Draw Term Loan Facility [Member] | 6.04% Interest Rate Effect From May 2, 2019 Through June 30, 2019 [Member]
Debt Instrument [Line Items]
Outstanding debt balance			9,800,000	$ 9,800,000
Interest rate				3.76%
Unamortized debt issuance costs			37,000	$ 37,000
Term Loan [Member]
Debt Instrument [Line Items]
Principal outstanding			172,376,000	172,376,000
Lines of credit, drawn amount		$ 175,000,000
Debt instrument quarterly payment, principal amount				437,500
Credit Agreement [Member]
Debt Instrument [Line Items]
Credit facility maturity date		Feb. 20, 2024
Credit Agreement [Member] | Revolving Facility [Member]
Debt Instrument [Line Items]
Outstanding debt balance			8,000,000	8,000,000
Undrawn balance				17,000,000
Commitment fees			19,000	$ 62,000
Credit Agreement [Member] | Maximum [Member] | September 30, 2020 through March 31, 2021 [Member]
Debt Instrument [Line Items]
Maximum total net leverage ratio		4.75
Credit Agreement [Member] | Maximum [Member] | June 30, 2021 through December 31, 2021 [Member]
Debt Instrument [Line Items]
Maximum total net leverage ratio		4.50
Credit Agreement [Member] | Maximum [Member] | March 31, 2022 and Each Fiscal Quarter Thereafter [Member]
Debt Instrument [Line Items]
Maximum total net leverage ratio		4.25
Credit Agreement [Member] | Maximum [Member] | LIBO Rate [Member]
Debt Instrument [Line Items]
Debt instrument bear interest rate		3.50%
Credit Agreement [Member] | Maximum [Member] | Alternate Base Rate [Member]
Debt Instrument [Line Items]
Debt instrument bear interest rate		2.50%
Credit Agreement [Member] | Maximum [Member] | Revolving Facility [Member]
Debt Instrument [Line Items]
Percentage of commitment fee unused portions				0.50%
Credit Agreement [Member] | Minimum [Member] | LIBO Rate [Member]
Debt Instrument [Line Items]
Debt instrument bear interest rate		2.50%
Credit Agreement [Member] | Minimum [Member] | Alternate Base Rate [Member]
Debt Instrument [Line Items]
Debt instrument bear interest rate		1.50%
Credit Agreement [Member] | Minimum [Member] | Revolving Facility [Member]
Debt Instrument [Line Items]
Percentage of commitment fee unused portions				0.25%
Credit Agreement [Member] | Senior Secured Delayed Draw Term Loan Facility [Member]
Debt Instrument [Line Items]
Debt instrument quarterly payment, principal amount				$ 25,000
Amortization payments percentage of original aggregate principal amount				1.00%
Credit Agreement [Member] | Syndicate of Lenders and SunTrust Bank [Member] | Senior Secured Revolving Credit Facility [Member] | Maximum [Member]
Debt Instrument [Line Items]
Aggregate principal amount			$ 25,000,000	$ 25,000,000
AppRiver Companies [Member] | Credit Agreement [Member] | Syndicate of Lenders and SunTrust Bank [Member] | Senior Secured Term Loan Facility [Member]
Debt Instrument [Line Items]
Aggregate principal amount		$ 175,000,000
AppRiver Companies [Member] | Credit Agreement [Member] | Syndicate of Lenders and SunTrust Bank [Member] | Senior Secured Delayed Draw Term Loan Facility [Member]
Debt Instrument [Line Items]
Aggregate principal amount		10,000,000
AppRiver Companies [Member] | Credit Agreement [Member] | Syndicate of Lenders and SunTrust Bank [Member] | Senior Secured Revolving Credit Facility [Member]
Debt Instrument [Line Items]
Aggregate principal amount		25,000,000
AppRiver Companies [Member] | Credit Agreement [Member] | Syndicate of Lenders and SunTrust Bank [Member] | Senior Secured Revolving Credit Facility [Member] | Maximum [Member]
Debt Instrument [Line Items]
Aggregate principal amount		$ 5,000,000
Delivery Slip Acquisition [Member] | Credit Agreement [Member] | Senior Secured Delayed Draw Term Loan Facility [Member]
Debt Instrument [Line Items]
Delayed draw term loan facility fully drawn date		May 2, 2019

Long-term Debt - Schedule of Fu

Long-term Debt - Schedule of Future Scheduled Principal Payments Under Term Loan (Detail) $ in Thousands	Sep. 30, 2020USD ($)
Term Loan [Member]
Debt Instrument [Line Items]
2020	$ 438
2021	1,750
2022	1,750
2023	1,750
2024	166,688
Total	172,376
Senior Secured Delayed Draw Term Loan Facility [Member]
Debt Instrument [Line Items]
2020	25
2021	100
2022	100
2023	100
2024	9,550
Total	$ 9,875

Preferred Stock - Additional In

Preferred Stock - Additional Information (Detail) - USD ($) $ / shares in Units, $ in Thousands	Feb. 20, 2019	Mar. 31, 2019	Sep. 30, 2020	Dec. 31, 2019	Jun. 06, 2019
Temporary Equity [Line Items]
Preferred stock, shares outstanding			0	0
Beneficial conversion feature, valued			$ 2,500
Series A Convertible Preferred Stock [Member]
Temporary Equity [Line Items]
Convertible Preferred stock, par value			$ 1	$ 1
Convertible Preferred stock, shares issued	64,914		100,206	100,206
Issuance of preferred stock in connection with private placement	$ 62,700
Preferred stock, net of issuance costs	$ 2,300	$ 2,253
Preferred stock, number of shares converted					35,292
Series B Convertible Preferred Stock [Member]
Temporary Equity [Line Items]
Convertible Preferred stock, shares issued	35,086
Issuance of preferred stock in connection with private placement	$ 33,900
Preferred stock, net of issuance costs	1,200	$ 1,204
Preferred stock, shares outstanding			0
Series A Preferred Stock [Member]
Temporary Equity [Line Items]
Preferred stock accretion percentage			8.00%
Accretion of stated value of preferred stock			$ 12,700
Preferred stock conversion description			At any time, each Series A Preferred Stock holder may elect to convert each share of such holders’ then-outstanding Series A Preferred Stock into (i) the number of shares of common stock equal to the product of (a) the Accreted Value with respect to such share on the conversion date multiplied by (b) the conversion rate (currently166.11) as of the applicable conversion date divided by (c) 1,000 plus (ii) cash in lieu of fractional shares.
True Wind Capital [Member]
Temporary Equity [Line Items]
Aggregate purchase price of preferred stock issued in private placement	$ 100,000
Convertible Preferred stock, par value	$ 1,000

Revenue from Contracts with C_2

Revenue from Contracts with Customers - Additional Information (Detail)	3 Months Ended		9 Months Ended
	Sep. 30, 2020USD ($)	Sep. 30, 2019USD ($)	Sep. 30, 2020USD ($)Segment	Sep. 30, 2019USD ($)
Disaggregation Of Revenue [Line Items]
Number of operating segment | Segment			1
Increased noncurrent deferred contract asset	$ 1,300,000		$ 3,400,000
Impairment losses recognized on deferred contract cost assets	0		0
Amortization of deferred cost	944,000		2,700,000
Revenue remaining service performance obligations	85,000,000		85,000,000
Revenue recognized performance obligation	26,600,000		54,100,000
Revenue recognized	$ 54,840,000	$ 47,833,000	160,611,000	$ 123,049,000
AppRiver Companies [Member]
Disaggregation Of Revenue [Line Items]
Increase to net deferred revenue			$ 923,000
Healthcare [Member]
Disaggregation Of Revenue [Line Items]
Revenue in precentage			21.00%
Financial Services [Member]
Disaggregation Of Revenue [Line Items]
Revenue in precentage			17.00%
Government Sector [Member]
Disaggregation Of Revenue [Line Items]
Revenue in precentage			3.00%
Other [Member]
Disaggregation Of Revenue [Line Items]
Revenue in precentage			59.00%
Minimum [Member]
Disaggregation Of Revenue [Line Items]
Subscription services contracts period			1 year
Maximum [Member]
Disaggregation Of Revenue [Line Items]
Subscription services contracts period			3 years

Revenue from Contracts with C_3

Revenue from Contracts with Customers - Additional Information (Detail 1) $ in Millions	Sep. 30, 2020USD ($)
Disaggregation Of Revenue [Line Items]
Revenue remaining service performance obligations	$ 85
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date: 2020-10-01
Disaggregation Of Revenue [Line Items]
Revenue, remaining performance obligation expected timing of satisfaction period	3 months
Revenue remaining service performance obligations	$ 26.7
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date: 2021-01-01
Disaggregation Of Revenue [Line Items]
Revenue, remaining performance obligation expected timing of satisfaction period	1 year
Revenue remaining service performance obligations	$ 41.7
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date: 2022-01-01
Disaggregation Of Revenue [Line Items]
Revenue, remaining performance obligation expected timing of satisfaction period	0 years
Revenue remaining service performance obligations	$ 16.5

Earnings (Loss) Per Share and_3

Earnings (Loss) Per Share and Potential Dilution - Computations of Basic and Diluted Earnings (Loss) Per Share (Detail) - shares	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Weighted Average Number of Shares [Line Items]
Basic weighted average common shares	54,999,114	53,148,078	53,933,721	52,965,163
Dilutive weighted average common shares	54,999,114	53,148,078	53,933,721	52,965,163

Goodwill - Schedule of Changes

Goodwill - Schedule of Changes in Carrying Amount of Goodwill (Detail) - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019
Goodwill Roll Forward
Opening balance	$ 171,209	$ 13,783
Additions		160,574
Effect of currency translation adjustment	(279)
Goodwill	$ 170,930	$ 174,357

Goodwill - Additional Informati

Goodwill - Additional Information (Detail) - USD ($)	9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018
Goodwill And Intangible Assets Disclosure [Abstract]
Goodwill impairment	$ 0	$ 0

Other Comprehensive Loss - Addi

Other Comprehensive Loss - Additional Information (Detail) - USD ($) $ in Thousands	3 Months Ended						9 Months Ended
	Sep. 30, 2020	Jun. 30, 2020	Mar. 31, 2020	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Sep. 30, 2020	Sep. 30, 2019
Accumulated Other Comprehensive Income Loss [Line Items]
Foreign currency translation loss, net of tax	$ (493)	$ (294)	$ 905	$ (35)	$ 56	$ 32	$ 118	$ 52
Canada [Member]
Accumulated Other Comprehensive Income Loss [Line Items]
Foreign currency translation loss, net of tax	$ 493						$ 118

Income Taxes - Additional Infor

Income Taxes - Additional Information (Detail) $ in Millions	Sep. 30, 2020USD ($)
Income Tax Disclosure [Abstract]
Operating loss carryforwards	$ 23

Acquisitions - Additional Infor

Acquisitions - Additional Information (Detail)	May 07, 2019USD ($)	May 06, 2019	Feb. 20, 2019USD ($)CustomerServiceProvider$ / sharesshares	Sep. 30, 2020USD ($)$ / shares	Sep. 30, 2020USD ($)$ / shares	Sep. 30, 2019USD ($)	Dec. 31, 2019USD ($)$ / shares	Dec. 31, 2018USD ($)
Business Acquisition [Line Items]
Cash consideration						$ 284,590,000
Series A Convertible Preferred Stock [Member]
Business Acquisition [Line Items]
Preferred stock, par value | $ / shares				$ 1	$ 1		$ 1
True Wind Capital [Member]
Business Acquisition [Line Items]
Preferred stock, par value | $ / shares			$ 1,000
Investment agreement aggregate cash consideration			$ 100,000,000
Delivery Slip Inc. [Member] | AppRiver Companies [Member]
Business Acquisition [Line Items]
Revenue generated from AppRiver Canada Inc		90.00%
Delivery Slip Inc. [Member]
Business Acquisition [Line Items]
Cash consideration	$ 11,400,000
Total purchase price	13,800,000
Contingent consideration liability	2,300,000
Loss on business combination contingent consideration							$ 200,000
Cash consideration paid through escrow deposit	1,500,000
Business combination, acquisition related costs							1,200
Intangible assets, estimated useful live					6 years
Delivery Slip Inc. [Member] | Senior Secured Delayed Draw Term Loan Facility [Member]
Business Acquisition [Line Items]
Aggregate principal amount	$ 10,000,000
AppRiver Companies [Member]
Business Acquisition [Line Items]
Total purchase price			$ 276,400,000
Business combination, acquisition related costs					$ 10,800,000
Percentage of equity interest acquired			100.00%
Cash consideration			$ 271,800,000
Number of customers | Customer			60,000
Number of managed service providers | ServiceProvider			4,500
Business combination, revenue				$ 35,200,000	101,800,000
AppRiver Companies [Member] | Customer Relationships [Member]
Business Acquisition [Line Items]
Intangible assets, estimated useful live			8 years
AppRiver Companies [Member] | Vendor Relationships [Member]
Business Acquisition [Line Items]
Intangible assets, estimated useful live			3 years
AppRiver Companies [Member] | Trademark/names [Member]
Business Acquisition [Line Items]
Intangible assets, estimated useful live			10 years
AppRiver Companies [Member] | Internally Developed Software [Member] | Minimum [Member]
Business Acquisition [Line Items]
Intangible assets, estimated useful live			5 years
AppRiver Companies [Member] | Internally Developed Software [Member] | Maximum [Member]
Business Acquisition [Line Items]
Intangible assets, estimated useful live			6 years
AppRiver Companies [Member] | Operating Expenses [Member]
Business Acquisition [Line Items]
Business combination, acquisition related costs					$ 41,000,000		$ 9,600,000	$ 1,100,000
AppRiver Companies [Member] | True Wind Capital [Member] | Series A Convertible Preferred Stock [Member] | Private Placement [Member]
Business Acquisition [Line Items]
Preferred stock, shares, new issue | shares			64,914
Preferred stock, par value | $ / shares			$ 1
AppRiver Companies [Member] | True Wind Capital [Member] | Series B Convertible Preferred Stock [Member] | Private Placement [Member]
Business Acquisition [Line Items]
Preferred stock, shares, new issue | shares			35,086
Preferred stock, par value | $ / shares			$ 1
AppRiver Companies [Member] | True Wind Capital [Member] | Series A and B Convertible Preferred Stock [Member] | Private Placement [Member]
Business Acquisition [Line Items]
Investment agreement aggregate cash consideration			$ 100,000,000
Reduction in costs, that were reimbursed			$ 3,000,000

Acquisitions - Summary of Estim

Acquisitions - Summary of Estimated Fair Value of Acquired Assets and Liabilities (Detail) - USD ($) $ in Thousands	Sep. 30, 2020	Dec. 31, 2019	Sep. 30, 2019	May 07, 2019	Feb. 20, 2019	Dec. 31, 2018
Assets:
Goodwill	$ 170,930	$ 171,209	$ 174,357			$ 13,783
Delivery Slip Acquisition [Member]
Assets:
Goodwill				$ 9,603
Total assets				13,803
Liabilities:
Deferred revenue				52
Total liabilities				52
Net assets recorded				13,751
Delivery Slip Acquisition [Member] | Technology [Member]
Assets:
Intangible assets				$ 4,200
AppRiver Companies [Member]
Assets:
Current assets					$ 12,200
Property and equipment					3,235
ROU assets					8,778
Goodwill					147,518
Total assets					312,684
Deferred tax assets					3,453
Liabilities:
Current liabilities					13,378
Deferred revenue					12,424
Operating lease liabilities					5,738
Total liabilities					34,980
Finance lease liabilities					3,440
Net assets recorded					277,704
AppRiver Companies [Member] | Trademark/names [Member]
Assets:
Intangible assets					4,400
AppRiver Companies [Member] | Customer Relationships [Member]
Assets:
Intangible assets					91,000
AppRiver Companies [Member] | Vendor Relationships [Member]
Assets:
Intangible assets					1,000
AppRiver Companies [Member] | Internally Developed Software [Member]
Assets:
Intangible assets					$ 41,100

Acquisitions - Unaudited Pro Fo

Acquisitions - Unaudited Pro Forma Financial Information (Detail) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Business Acquisition Pro Forma Information [Abstract]
Revenues	$ 54,925	$ 48,899	$ 160,865	$ 143,146
Net income	$ (624)	$ 624	$ (2,960)	$ 1,328
Basic income (loss) per share attributed to common shareholders	$ (0.05)	$ (0.03)	$ (0.14)	$ (0.15)
Diluted income (loss) per share attributed to common shareholders	$ (0.05)	$ (0.03)	$ (0.14)	$ (0.15)

Subsequent Events - Additional

Subsequent Events - Additional Information (Detail) - Subsequent Event $ in Millions	Nov. 05, 2020USD ($)CustomerServiceProviderUser
Subsequent Event [Line Items]
Term loan	$ 35
CloudAlly Ltd
Subsequent Event [Line Items]
Percentage of equity interest acquired	100.00%
Cash consideration	$ 30
Number of customers | Customer	5,000
Number of users | User	500,000
Number of managed service providers | ServiceProvider	300