Zix (ZIXI) 10-K 8 Mar 19 2018 FY Annual report Financial data

Document and Entity Information

Document and Entity Information - USD ($)	12 Months Ended
	Dec. 31, 2018	Mar. 06, 2019	Jun. 30, 2018
Document And Entity Information [Abstract]
Document Type	10-K
Amendment Flag	false
Document Period End Date	Dec. 31, 2018
Document Fiscal Year Focus	2,018
Document Fiscal Period Focus	FY
Trading Symbol	ZIXI
Entity Registrant Name	ZIX CORP
Entity Central Index Key	855,612
Current Fiscal Year End Date	--12-31
Entity Well-known Seasoned Issuer	No
Entity Current Reporting Status	Yes
Entity Voluntary Filers	No
Entity Filer Category	Accelerated Filer
Entity Small Business	false
Entity Emerging Growth Company	false
Entity Shell Company	false
Entity Common Stock, Shares Outstanding		54,089,273
Entity Public Float			$ 289,258,242

Consolidated Balance Sheets

Consolidated Balance Sheets - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017
Current assets:
Cash and cash equivalents	$ 27,109	$ 33,009
Receivables, net	3,188	1,389
Prepaid and other current assets	3,176	3,222
Total current assets	33,473	37,620
Property and equipment, net	3,924	4,048
Other assets and deferred costs	9,424
Intangible assets, net	15,251	5,524
Goodwill	13,783	8,469
Deferred tax assets	28,785	25,647
Total assets	104,640	81,308
Current liabilities:
Accounts payable	769	1,053
Accrued expenses	9,747	6,101
Deferred revenue	30,622	28,362
Total current liabilities	41,138	35,516
Long-term liabilities:
Deferred revenue	1,539	1,087
Deferred rent	1,016	1,185
Total long-term liabilities	2,555	2,272
Total liabilities	43,693	37,788
Commitments and contingencies (Note 15)
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; 81,715,330 issued and 54,186,180 outstanding in 2018 and 80,709,970 issued and 54,542,612 outstanding in 2017	779	778
Additional paid-in capital	384,940	381,457
Treasury stock, at cost; 27,529,150 common shares in 2018 and 26,167,358 common shares in 2017	(108,392)	(102,343)
Accumulated deficit	(216,364)	(236,372)
Accumulated other comprehensive (loss) income	(16)
Total stockholders’ equity	60,947	43,520
Total liabilities and stockholders’ equity	$ 104,640	$ 81,308

Consolidated Balance Sheets (Pa

Consolidated Balance Sheets (Parenthetical) - $ / shares	Dec. 31, 2018	Dec. 31, 2017
Statement Of Financial Position [Abstract]
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	81,715,330	80,709,970
Common stock, shares outstanding	54,186,180	54,542,612
Treasury stock, shares	27,529,150	26,167,358

Consolidated Statements of Comp

Consolidated Statements of Comprehensive Income - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Income Statement [Abstract]
Revenues	$ 70,478	$ 65,663	$ 60,144
Cost of revenue	15,186	12,602	10,533
Gross margin	55,292	53,061	49,611
Research and development expenses	11,323	10,980	9,553
Selling, general and administrative expenses	33,999	31,871	30,742
Operating income	9,970	10,210	9,316
Other income (expense):
Investment and other income	754	339	246
Interest expense			33
Total other income	754	339	213
Income before income taxes	10,724	10,549	9,529
Income tax benefit (expense)	4,720	(18,606)	(3,692)
Net income (loss)	$ 15,444	$ (8,057)	$ 5,837
Basic income (loss) per common share	$ 0.29	$ (0.15)	$ 0.11
Diluted income (loss) per common share	$ 0.29	$ (0.15)	$ 0.11
Weighted average shares outstanding
Basic common shares outstanding	52,591,714	53,430,492	53,819,772
Diluted common shares outstanding	53,481,295	53,430,492	54,395,145
Other comprehensive income, net of tax:
Foreign currency translation adjustments	$ (16)
Comprehensive income (loss)	$ 15,428	$ (8,057)	$ 5,837

Consolidated Statements of Stoc

Consolidated Statements of Stockholders' Equity - USD ($) $ in Thousands	Total	Under ASC 605 [Member]	Cumulative Effect Adjustment [Member]	Common Stock [Member]	Common Stock [Member]Under ASC 605 [Member]	Additional Paid-In Capital [Member]	Additional Paid-In Capital [Member]Under ASC 605 [Member]	Treasury Stock [Member]	Treasury Stock [Member]Under ASC 605 [Member]	Accumulated Deficit [Member]	Accumulated Deficit [Member]Under ASC 605 [Member]	Accumulated Deficit [Member]Cumulative Effect Adjustment [Member]	Accumulated Other Comprehensive Income (Loss) [Member]
Beginning balance at Dec. 31, 2015	$ 56,772			$ 767		$ 372,400		$ (82,243)		$ (234,152)
Beginning balance, shares at Dec. 31, 2015				77,852,453
Issuance of common stock upon exercise of stock options	$ 205			$ 2		203
Issuance of common stock upon exercise of stock options, shares	123,760			123,760
Issuance of common stock upon vesting of restricted stock units, net, shares				179,914
Issuance of common stock upon vesting of performance stock units, net, shares				97,428
Issuance of restricted common stock, net, shares				518,211
Issuance of restricted performance common stock, net, shares				141,500
Employee stock-based compensation costs	$ 1,256					1,783		(527)
Treasury repurchase program	(15,000)							(15,000)
Net income (loss)	5,837									5,837
Ending balance at Dec. 31, 2016	49,070			$ 769		374,386		(97,770)		(228,315)
Ending balance, shares at Dec. 31, 2016				78,913,266
Issuance of common stock upon exercise of stock options	$ 4,206			$ 9		4,197
Issuance of common stock upon exercise of stock options, shares	932,303			932,303
Issuance of common stock upon vesting of restricted stock units, net, shares				126,167
Issuance of common stock upon vesting of performance stock units, net, shares				20,999
Issuance of restricted common stock, net, shares				645,623
Issuance of restricted performance common stock, net, shares				71,612
Employee stock-based compensation costs	$ 2,112					2,874		(762)
Treasury repurchase program	(3,811)							(3,811)
Net income (loss)	(8,057)									(8,057)
Ending balance at Dec. 31, 2017	43,520	$ 43,520			$ 778		$ 381,457		$ (102,343)		$ (236,372)
Ending balance, shares at Dec. 31, 2017					80,709,970
Cumulative effect adjustment from changes in accounting standards at Dec. 31, 2017			$ 4,564									$ 4,564
Ending balances, as adjusted at Dec. 31, 2017	48,084			$ 778		381,457		(102,343)		(231,808)
Issuance of common stock upon exercise of stock options	$ 166			$ 1		165
Issuance of common stock upon exercise of stock options, shares	90,011			90,011
Issuance of common stock upon vesting of restricted stock units, net, shares				50,751
Issuance of common stock upon vesting of performance stock units, net, shares				32,665
Issuance of restricted common stock, net, shares				735,987
Issuance of restricted performance common stock, net, shares				95,946
Employee stock-based compensation costs	$ 2,662					3,318		(656)
Treasury repurchase program	(5,393)							(5,393)
Adjustment from foreign currency translation	(16)												$ (16)
Net income (loss)	15,444									15,444
Ending balance at Dec. 31, 2018	$ 60,947			$ 779		$ 384,940		$ (108,392)		$ (216,364)			$ (16)
Ending balance, shares at Dec. 31, 2018				81,715,330

Consolidated Statements of Cash

Consolidated Statements of Cash Flows - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Operating activities:
Net income (loss)	$ 15,444	$ (8,057)	$ 5,837
Non-cash items in net income (loss):
Depreciation and amortization	3,706	2,741	2,303
Employee stock-based compensation expense	3,318	2,874	1,783
Changes in deferred taxes	(4,754)	18,470	3,186
Changes in operating assets and liabilities:
Receivables	(1,376)	64	(711)
Prepaid and other assets	108	(386)	79
Other assets and deferred costs	(3,139)
Accounts payable	(325)	645	(15)
Deferred revenue	1,892	1,370	3,200
Earn-out payment	(195)
Accrued and other liabilities	1,992	483	(411)
Net cash provided by operating activities	16,671	18,204	15,251
Investing activities:
Purchases of property, equipment and internal-use software	(4,179)	(3,041)	(2,136)
Acquisition of business, net of cash acquired	(11,773)	(8,244)
Net cash used in investing activities	(15,952)	(11,285)	(2,136)
Financing activities:
Proceeds from exercise of stock options	166	4,206	205
Deferred debt financing costs	60
Stock issuance costs	(45)
Earn-out payment	(605)
Treasury stock	(6,049)	(4,573)	(15,527)
Net cash used in financing activities	(6,593)	(367)	(15,322)
Effect of exchange rate changes on cash	(26)
Increase (decrease) in cash and cash equivalents	(5,900)	6,552	(2,207)
Cash and cash equivalents, beginning of year	33,009	26,457	28,664
Cash and cash equivalents, end of year	$ 27,109	$ 33,009	$ 26,457

Company Overview

Company Overview	12 Months Ended
	Dec. 31, 2018
Accounting Policies [Abstract]
Company Overview	1. Company Overview Zix Corporation (“Zix,” the “Company,” “we,” “our,” “us”) provides email encryption, advanced threat protection, email archiving, data loss prevention (“DLP”) and Bring-Your-Own-Device (“BYOD”) solutions to meet the data protection and compliance needs of organizations primarily in the healthcare, financial services, and government sectors.

Summary of Significant Accounti

Summary of Significant Accounting Policies	12 Months Ended
	Dec. 31, 2018
Accounting Policies [Abstract]
Summary of Significant Accounting Policies	2. Summary of Significant Accounting Policies Basis of Presentation — The accompanying consolidated financial statements include the accounts of all our wholly-owned subsidiaries and are prepared in accordance with accounting principles generally accepted in the United States of America (“U.S. GAAP”). All inter-company accounts and transactions have been eliminated in consolidation. Use of Estimates — The preparation of consolidated financial statements in conformity with accounting principles generally accepted in the United States of America requires management to make estimates and assumptions that affect the reported amount of assets and liabilities and disclosure of contingent assets and liabilities at the date of the consolidated financial statements and the reported amounts of revenue and expenses during the reported period. Our significant estimates include primarily those required in the valuation or impairment analysis of goodwill and intangibles, property and equipment, revenue recognition, amortization period of our commission amortization, allowances for doubtful accounts, stock-based compensation, litigation accruals, valuation allowances for deferred tax assets and tax accruals. Although we believe that adequate accruals have been made for unsettled issues, additional gains or losses could occur in future years from resolutions of outstanding matters. Actual results could differ materially from original estimates. Cash Equivalents — Cash investments with maturities of three months or less when purchased are considered cash equivalents Fair Value of Financial Instruments —The Company does not measure the fair value of any financial instrument other than cash equivalents, options, and other equity awards. The carrying values of other financial instruments (receivables and accounts payable) are not recorded at fair value but approximate fair values primarily due to their short-term nature. 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. Valuation of Property and Equipment — The accounting policies and estimates relating to property and equipment are considered significant because of the potential impact that impairment, obsolescence, or change in an asset’s useful life could have on the Company’s operating results. We record an impairment charge on the assets to be held and used when we determine based upon certain triggering events that the carrying value of property and equipment may not be recoverable based on expected undiscounted cash flows attributable to such assets. The amount of a potential impairment is determined by comparing the carrying amount of the asset to either the value determined from a projected discounted cash flow method, using a discount rate that is considered to be commensurate with the risk inherent in the Company’s current business model or the estimated fair market value. Assumptions are made with respect to future net cash flows expected to be generated by the related asset. An impairment charge would be recorded for an amount by which the carrying value of the asset exceeded the discounted projected net cash flows or estimated fair market value. Also, even where a current impairment charge is not necessary, the remaining useful lives are evaluated. No impairment was recorded for any of the periods presented. Property and equipment are recorded at cost and depreciated or amortized using the straight-line method over their estimated useful lives as follows: computer and office equipment and software — three years; leasehold improvements — the shorter of five years or the lease term; and furniture and fixtures — five years. We recorded a depreciation expense of $2.4 million for the year ended December 31, 2018. We allocated $1.7 million of the expense to cost of revenue, $426 thousand to research and development expense, and $314 thousand to selling, marketing, and general and administrative expenses. Goodwill and Other Intangible Assets — We account for the valuation of goodwill and other intangible assets after classifying intangible assets into three categories: (1) intangible assets with finite lives subject to amortization; (2) intangible assets with indefinite lives not subject to amortization; and (3) goodwill. For intangible assets with finite lives, tests for impairment must be performed if conditions exist that indicate the carrying value may not be recoverable. For intangible assets with indefinite lives and goodwill, tests for impairment must be performed at least annually or more frequently if events or circumstances indicate that assets might be impaired. Goodwill was $13.8 million, or 13%, and $8.5 million, or 10%, of total assets as of December 31, 2018 and 2017, respectively. We evaluate the goodwill for impairment annually in the fourth quarter, or when there is reason to believe that the value has been diminished or impaired. Evaluations for possible impairment are based upon a comparison of the estimated fair value of the reporting unit to which the goodwill has been assigned, versus the sum of the carrying value of the assets and liabilities of that unit including the assigned goodwill value. We include our entire Company as the reporting unit. The fair values used in this evaluation are estimated based on the Company’s market capitalization, which is based on the outstanding stock and market price of the stock. Impairment is deemed to exist if the net book value of the unit exceeds its estimated fair value. No impairment was recorded for any of the periods presented. Our intangible assets with finite lives are amortized using a straight line basis over their economic useful lives. Deferred Tax Assets — Deferred tax assets are recognized if it is “more likely than not” that the benefit of our deferred tax assets will be realized on future federal or state income tax returns. At December 31, 2018, we provided a valuation allowance against a significant portion, $22.7 million, of our accumulated U.S. deferred tax assets, reflecting our historical losses and the uncertainty of future taxable income sufficient to utilize net operating loss carryforwards prior to their expiration. Our total deferred tax assets not subject to a valuation allowance are valued at $28.8 million, and consist of $27.0 million for federal net operating loss carryforwards , $2.1 million relating to U.S. state income tax credits, $678 thousand related to Alternative Minimum Tax credits and $114 thousand related to foreign tax credits. These credits are offset by ($1.2) million relating to temporary timing differences between U.S. GAAP and tax-related expense. If our U.S. taxable income increases from its current level in a future period or if the facts and circumstances on which our estimates and assumptions are based were to change, thereby impacting the likelihood of realizing our deferred tax assets, judgment would have to be applied in determining the amount of valuation allowance no longer required. Reversal of all or a part of this valuation allowance could have a significant positive impact on operating results in the period that it becomes more likely than not that certain of the Company’s deferred tax assets will be realized. Alternatively, should our future income decrease from current levels, a resulting increase to all or a part of this valuation allowance could have a significant negative impact on our operating results Uncertain Tax Positions — Our Company recognizes and measures uncertain tax positions using a two-step approach. The first step is to evaluate the tax position for recognition by determining if the weight of available evidence indicates that it is more likely than not that the position will be sustained on audit, including resolution of related appeals or litigation processes, if any. The second step is to measure the tax benefit as the largest amount that is more than 50% likely of being realized upon settlement. Leases — A leased asset whose lease terms meet the criteria for capitalization is recorded as an asset and depreciated. If a lease does not meet the criteria for capitalization, it is classified as an operating lease and payments are recorded as rent expense. For 2018 and 2017 we had no leases that qualified as capital leases. Lease renewal options which we are “reasonably assured” of using and the related payments are taken into account when initially classifying and recording the lease as a capital lease obligation or as straight-line rent if an operating lease. Funds provided by the lessor for leasehold improvements are recorded as a deferred lease incentive and amortized as a reduction of rent expense over the lease term. Revenue Recognition — In May 2014, The Financial Accounting Standards Board (“FASB”) issued ASC 606 which requires revenue recognition when promised goods or services are transferred to customers in an amount that reflects the consideration to which an entity expects to be entitled to those goods and services. The standard became effective for us in 2018, but did not have a material impact to our revenue recognition process. For additional information regarding our adoption of ASC 606 please see “New Accounting Standards.” We earn our revenue from subscription fees for rights related to the use of our software. Our revenue contracts include multiple performance obligations that are highly interdependent and consists of software at the customer’s site, ongoing customer support, and cloud-based access to the hosted Zix encryption network. As our Company has expanded its portfolio of message security offerings in recent years, we have increased our revenue obtained from hosted service solutions. Approximately 38% of our revenue in 2018 was derived from hosted email protection solutions. Our subscription terms typically range from one to five years. Revenue is recognized by applying the following steps: • Step 1: Identify the contract(s) with a customer, • Step 2: Identify the performance obligations in the contract, • Step 3: determine the transaction price • Step 4: allocate the transaction price to the performance obligations in the contract, and • Step 5: recognize revenue when (or as) the performance obligation is satisfied. • Step 1: Identify the contract(s) with a customer: We consider the terms and conditions of the contract and our customary business practice in identifying our contracts. We determine we have a contract with a customer when the contract is approved, we can identify each party’s rights regarding the services and products transferred, we can identify the payment terms for the services and products, the contract has commercial substance, and it is probable we will be paid. • Step 2: Identifying the performance obligations: ASC 606 requires identification and disclosure of performance obligations within a revenue contract. A good or service is considered distinct if the customer can both benefit from the good or service on its own or with other resources that are readily available to the customer, and the promise to transfer the good or service is separately identifiable from other promises in the contract. As of December 31, 2018, revenue from our email protection services represent 100% of our revenue, of which approximately 88% is specific to email encryption. To provide this service, our software at the customer site includes functionality to create a private encryption key that works in conjunction with the public encryption key provided via cloud-based access to our hosted Zix encryption network. Both keys are required to enable our asymmetrical encryption service. In our assessment of the factors listed in ASC 606-10-25-21, we have determined that because our software at the customer’s site and the access to our hosted Zix encryption network are highly interrelated, these items are not regarded as distinct components. Based on this assessment, these elements are combined as a single performance obligation. • Step 3: Determine the transaction price: The transaction price is determined based on the consideration we expect to be entitled to receive in exchange for transferring goods and services to the customer. We include variable consideration in the transaction price if we view it as probable that a significant future reduction of cumulative revenue under the contract will not occur. • Step 4: Allocate the transaction price to the performance obligations in the contract: We allocate transaction prices to each performance obligation based on the stand-alone selling price of our component services. • Step 5: Recognize revenue when (or as) the performance obligation is satisfied: We recognize revenue when the customer obtains control of the product or services, at the amount allocated to the satisfied performance obligation. Our performance obligations are generally satisfied over time. While some contracts include one or more performance obligations (including the combined elements noted above along with additional ongoing customer support and other hosted services), the revenue recognition pattern generally is not impacted by the separate allocations of these obligations because the services are generally satisfied over the same period of time and revenue is recognized over the contract period. Discounts provided to customers are recorded as reductions in revenue. Commission Amortization — We amortize our commission costs to expense on a systemic basis over the period of expected benefit to the customer. Determination of the amortization period requires significant judgement. We apply the practical expedient noted in ASC 606-10-10-4 to account for our commission costs and related amortizations at the portfolio level. Additionally, the Company has evaluated commissions earned upon contract renewal as compared to initial commissions paid and determined that because commissions paid were not reasonably proportional to their respective contract values, our renewal commissions could not be considered commensurate with the initial commissions paid. We considered our average contract term length and historical customer retention rates to determine an average length of our customer relationships. We also concluded our add-on sales generally occur halfway into our customer relationships, and evaluated our average customer renewal terms. Based on these factors we have determined that 8 years, 4 years and 18 months are the appropriate amortization periods to our new, add-on, and renewal sales commission expenses, respectively. We also perform subsequent assessments for impairment of the related deferred cost asset when indicators present. Software Development Costs —Costs incurred in the development and testing of subscription software products related to research, project planning, training, maintenance and general and administrative activities, and overhead costs are expensed as incurred. The costs of relatively minor upgrades and enhancements to the software are also expensed as incurred. Costs for the development of new software solutions and substantial enhancements to existing software solutions are expensed as incurred until technological feasibility has been established, at which time any additional costs would be capitalized. Historically, we have not capitalized standard research and development costs because we believe that technological feasibility is established concurrent with general release to customers. Research and development costs associated with software developed for internal use on behalf of our customers are capitalized. As we increasingly moved to a multi-tenant environment to keep up with the industry trend requiring transition to a cloud based solution for our existing services, certain research and development expenditures associated with hosting arrangements began to meet the accounting guidance requirement for capitalizing development costs under ASC 350-40, Internal-Use Software, as it applies to hosting arrangements. These capitalized costs are classified as intangible assets in our consolidated balance sheet. In 2018, we capitalized $1.5 million of research and development costs related to hosted software development for our customers. The Company expects our capitalization of these research and development expenditures to increase in the future. Advertising Expense — Advertising costs are expensed as incurred. Our operations include advertising expense of $1.3 million, $1.5 million, and $1.9 million in 2018, 2017, and 2016, respectively Stock-Based Compensation — We currently use the straight-line amortization method for recognizing stock option and restricted stock compensation costs. The measurement and recognition of compensation expense for all share-based payment awards made to our employees and directors are based on the estimated fair value of the awards on the grant dates. The grant date fair value is estimated using either an option-pricing model which is consistent with the terms of the award or a market observed price, if such a price exists. Such cost is recognized over the period during which an employee or director is required to provide service in exchange for the award, i.e., “the requisite service period” (which is usually the vesting period). We also estimate the number of instruments that will ultimately be earned, rather than accounting for forfeitures as they occur. Earnings Per Share (“EPS”) — Basic EPS is based on the weighted average number of common shares outstanding during each period. Diluted EPS adjusts Basic EPS for the effects of dilutive common stock equivalents outstanding during each period using the treasury stock method. New Accounting Standards Revenue Recognition In May 2014, the FASB issued ASC 606, which supersedes most prior revenue recognition guidance under U.S. Generally Accepted Accounting Principles (“GAAP”). The core principle of ASC 606 is to recognize revenues when promised goods or services are transferred to customers in an amount that reflects the consideration to which an entity expects to be entitled for those goods or services. ASC 606 defines a five step process to achieve this core principle and, in doing so, more judgment and estimates may be required within the revenue recognition process than were required under prior U.S. GAAP. The standard became effective for us beginning in 2018. Our Company provides primarily email encryption and advanced threat protection security solutions as subscription services in which we recognize revenue as our services are rendered. We determined our revenue was not materially impacted by the new guidance. However, the guidance did require us to increase the amortization period of our commission expense. We applied the guidance to commissions earned on all contracts that were not complete as of January 1, 2018. Prior period amounts were not adjusted and continue to be reported in accordance with the previous guidance. Our Company elected to use a portfolio approach, applying 8 year, 4 year, and 18 month amortization periods for our new, add-on, and renewal sales commission expenses, respectively. Determination of the amortization period and the subsequent assessments for impairment of the related deferred cost asset requires significant judgement. We applied a modified retrospective approach to our implementation of ASC 606 in which we recognized a $4.6 million cumulative effect adjustment to our 2018 retained earnings opening balance related to our increased amortization period. This adjustment includes a $1.6 million impact to our deferred tax asset. The table below presents the cumulative effect of the changes made to our consolidated balance sheet due to the adoption of ASC 606: (In thousands) January 1, 2018 Beginning Balance Cumulative Effect Adjustment Beginning Balance, as Adjusted Assets: Prepaid and other current assets $ 3,222 $ (415 ) $ 2,807 Other assets and deferred costs — 6,595 6,595 Deferred tax assets 25,647 (1,616 ) 24,031 Stockholders’ equity: Accumulated deficit $ (236,372 ) $ 4,564 $ (231,808 ) Financial statement results as reported under the new revenue standard as compared to the previous standard for the twelve months ended and as of December 31, 2018, are as follows: Twelve Months Ended December 31, 2018 (In thousands, except per share data) Under ASC 605 Under ASC 606 Variance Revenues $ 70,478 $ 70,478 $ — Cost of revenues 15,186 15,186 — Gross margin 55,292 55,292 — Operating expenses: Research and development 11,323 11,323 — Selling, general and administrative 36,554 33,999 (2,555 ) Total operating expenses 47,877 45,322 (2,555 ) Operating income 7,415 9,970 2,555 Other income, net 754 754 — Income before income taxes 8,169 10,724 2,555 Income tax expense 5,257 4,720 (537 ) Net income $ 13,426 $ 15,444 $ 2,018 Basic income per common share $ 0.26 $ 0.29 0.04 Diluted income per common share $ 0.25 $ 0.29 0.04 (1) (In thousands) December 31, 2018 Under ASC 605 Under ASC 606 Variance Assets: Prepaid and other current assets $ 3,760 $ 3,176 $ (584 ) Other assets and deferred costs — 9,424 9,424 Deferred tax assets 30,401 28,785 (1,616 ) Stockholders’ equity: Accumulated deficit $ (222,946 ) $ (216,364 ) $ 6,582 Cash Flow Statement In August 2016, the FASB issued ASU No. 2016-15, Statement of Cash Flows (Topic 230), which amends guidance on the classification of certain cash receipts and payments in the statement of cash flows. This ASU was issued with the intent to reduce diversity in practice with respect to eight types of cash flows. The new guidance addressed debt prepayment or extinguishment of costs, settlement of zero-coupon bonds, contingent consideration made after a business combination, proceeds from the settlement of insurance claims, proceeds from the settlement of corporate-owned life insurance policies and bank-owned life insurance policies, distributions received from equity method investees, beneficial interests in securitization transactions, and separately identifiable cash flows and application of the predominance principle. The standard became effective for us beginning in 2018. We applied the new guidance within our consolidated statements of cash flows classification to an $800 thousand earn-out payment associated with our Greenview (as defined herein) acquisition. Because this consideration payment was not made soon after the consummation date, as required by the guidance, we classified $605 thousand of the payment as a financing activity. This reflects the portion of the payment recognized a contingent liability as of the acquisition date. The $195 thousand balance of the payment was in excess of the original contingent consideration liability and was classified as an operating activity. The standard had no other impact on our consolidated financial statements. Leases In February 2016, the FASB issued ASU 2016-02, Leases (Topic 842). Topic 842 requires companies to generally recognize on the balance sheet operating and financing lease liabilities and corresponding right-of-use assets. The new lease standard becomes effective for us beginning 2019. We expect to adopt Topic 842 using the effective date as the date of our initial application of the standard. Consequently, financial information for the comparative periods will not be updated. We currently expect that most of our operating lease commitments will be subject to the new standard and recognized as operating lease liabilities and right-of-use assets upon our adoption of Topic 842. We are evaluating the potential impact of this new guidance on our consolidated financial statements, and currently estimate the recognition of our outstanding lease obligations as of December 31, 2018, will result in the recognition of right-to-use-assets and lease liabilities of $4.5 million to $6.5 million.

Stock Options and Stock-Based E

Stock Options and Stock-Based Employee Compensation	12 Months Ended
	Dec. 31, 2018
Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]
Stock Options and Stock-based Employee Compensation	3. Stock Options and Stock-Based Employee Compensation Below is a summary of common stock options outstanding at December 31, 2018: Authorized Shares Options Outstanding Options Vested Available for Grant Employee and Director Stock Option Plans: 2004 Stock Option Plan 5,000,000 230,000 230,000 — 2006 Director’s Stock Option Plan 1,100,000 55,000 55,000 — 2012 Incentive Plan 6,300,000 638,823 532,573 — 2018 Omnibus Incentive Plan 6,000,000 — — 5,875,000 Total 18,400,000 923,823 817,573 5,875,000 Under all of our stock option plans, new shares are issued when options are exercised. Employee and Director Stock- Based Plans We have non-qualified stock options outstanding to employees and directors under various stock option plans. The plans require the exercise price of options granted under these plans to equal or exceed the fair market value of the Company’s common stock on the date of grant. The options, subject to termination of employment, generally expire ten years from the date of grant. Historically, our employee options and equity awards typically vested pro-rata and quarterly over three years. Stock-based grants to employees, officers and directors frequently contain accelerated vesting provisions upon the occurrence of a change of control, as defined in the applicable option agreements. Under the terms of the 2018 Omnibus Incentive Plan approved by our shareholders during our annual meeting held on June 6, 2018, (the “2018 Plan”), 6,000,000 shares are available for issuance. Awards issued under the 2018 Plan typically vest pro-rata and quarterly over four years. Under the terms of the 2012 Incentive Plan adopted by our Board of Directors on April 13, 2012 (the “2012 Plan”), 2,700,000 shares are available for issuance, plus a number of additional shares (not to exceed 1,327,000) underlying options outstanding under certain of the Company’s prior equity plans that thereafter terminate or expire unexercised, or are cancelled, forfeited, or lapse for any reason. Our shareholders approved an Amended and Restated 2012 Incentive Plan during our annual meeting held June 24, 2015, increasing the number of shares available for grant by 3,600,000. Awards issued under the 2012 Plan typically vest pro-rata and quarterly over four years. Accounting Treatment We use the straight-line amortization method for recognizing stock option compensation costs. Our share-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”). For the twelve months ended December 31, 2018, 2017, and 2016, respectively, the total stock-based compensation expense resulting from stock options, Restricted Stock, RSUs, Performance RSUs, and Performance Stock was recorded to the following line items of our consolidated statements of operations: Year Ended December 31, (In thousands) 2018 2017 2016 Cost of revenue $ 327 $ 304 $ 186 Research and development expenses 469 374 246 Selling, general and administrative expenses 2,522 2,196 1,351 Stock-based compensation expense $ 3,318 $ 2,874 $ 1,783 Our stock-based compensation expense has increased yearly due to program expansion associated with our Company growth. Our 2017 stock-based compensation expense includes $292 thousand related to accelerated vesting of awards associated with executive departures. Our 2016 stock-based compensation expense includes $280 thousand related to the accelerated vesting of awards related to our CFO transition. A deferred tax asset of $673 thousand, $824 thousand, and $506 thousand, resulting from stock-based compensation expense associated with awards relating to the Company’s U.S. operations, was recorded for the twelve months ended December 31, 2018, 2017, and 2016, respectively. As of December 31, 2018, there was $5.2 million of total unrecognized stock-based compensation related to non-vested share-based compensation awards granted under the stock award plans. This cost is expected to be recognized over a weighted average period of 1.5 years. We use the Black-Scholes Option Pricing Model (“BSOPM”) to determine the fair value of option grants. The Company uses the “historical” method to calculate the estimated life of any options that may be granted. The expected stock price volatility is calculated by averaging the historical volatility of the Company’s common stock over a term equal to the expected life of the options. We did not grant options in 2018. We granted 30,750 options in 2017 and 373,187 options in 2016. The following weighted average assumptions were applied in determining the fair value of options granted during the respective periods: Year Ended December 31, 2018 2017 2016 Risk-free interest rate — 2.02 % 1.21 % Expected option life (years) — 5.7 5.3 Expected stock price volatility — 42 % 44 % Expected dividend yield — — — Fair value of options granted $ — $ 2.06 $ 1.51 The assumptions used in the BSOPM valuation are critical as a change in any given factor could have a material impact on the financial results of the Company. The weighted average grant-date fair value of awards of restricted stock and restricted stock units is based on quoted market price of the Company’s common stock on the date of grant. Stock Option Activity The following is a summary of all stock option transactions for the three years ended December 31, 2018: Shares Weighted Average Exercise Price Weighted Average Remaining Contractual Term (Yrs) Outstanding at January 1, 2016 1,774,552 $ 3.65 Granted at market price 373,187 $ 3.70 Cancelled or expired (63,700 ) $ 3.95 Exercised (123,760 ) $ 1.66 Outstanding at December 31, 2016 1,960,279 $ 3.78 Granted at market price 30,750 $ 4.96 Cancelled or expired (37,412 ) $ 4.71 Exercised (932,303 ) $ 4.51 Outstanding at December 31, 2017 1,021,314 $ 3.11 Granted at market price — $ 0.00 Cancelled or expired (7,480 ) $ 4.04 Exercised (90,011 ) $ 1.83 Outstanding at December 31, 2018 923,823 $ 3.23 4.76 Options exercisable at December 31, 2018 817,573 $ 3.16 4.43 At December 31, 2018, all 923,823 options outstanding and all 817,573 options exercisable had an exercise price lower than the market value of the Company’s common stock. The aggregate intrinsic value of these options was $2.3 million and $2.1 million, respectively. At December 31, 2017, 983,564 options outstanding and 802,314 options exercisable had an exercise price lower than the market value of the Company’s common stock. The aggregate intrinsic value of these options was $1.3 million and $1.2 million, respectively. The total intrinsic value of options exercised during the years ended December 31, 2018 and 2017, was $334 thousand and $914 thousand , respectively. Summarized information about stock options outstanding at December 31, 2018, is as follows: Options Outstanding Options Exercisable Range of Exercise Prices Number Outstanding Weighted Average Remaining Contractual Life Weighted Average Exercise Price Number Exercisable Weighted Average Exercise Price $2.00 - $3.49 431,813 2.90 $ 2.58 431,813 $ 2.58 $3.50 - $4.99 492,010 6.40 $ 3.80 385,760 $ 3.82 923,823 4.76 $ 3.23 817,573 $ 3.16 There were 832,376 and 1,685,732 exercisable options at December 31, 2017 and 2016, respectively. Restricted Stock Activity The following is a summary of all Restricted Stock activity during the three years ended December 31, 2018: Restricted Shares Weighted Average Fair Value Non-vested restricted stock at January 1, 2016 423,250 $ 3.91 Granted at market price 573,461 $ 3.75 Vested (292,469 ) $ 3.50 Cancelled (15,000 ) $ 4.11 Non-vested restricted stock at December 31, 2016 689,242 $ 3.94 Granted at market price 665,623 $ 5.02 Vested (251,956 ) $ 4.00 Cancelled (20,000 ) $ 4.96 Non-vested restricted stock at December 31, 2017 1,082,909 $ 4.57 Granted at market price 842,546 $ 4.53 Vested (419,452 ) $ 4.44 Cancelled (151,003 ) $ 4.77 Non-vested restricted stock at December 31, 2018 1,355,000 $ 4.71 Restricted Stock Unit Activity The following is a summary of all RSU activity during the three years ended December 31, 2018: Restricted Stock Units Weighted Average Fair Value Non-vested restricted stock units at January 1, 2016 299,500 $ 3.79 Granted at market price 38,500 $ 3.74 Vested (179,914 ) $ 3.66 Cancelled — $ — Non-vested restricted stock units at December 31, 2016 158,086 $ 3.92 Granted at market price 54,500 $ 4.96 Vested (126,167 ) $ 4.07 Cancelled — $ — Non-vested restricted stock units at December 31, 2017 86,419 $ 4.36 Granted at market price 36,500 $ 4.57 Vested (50,751 ) $ 4.18 Cancelled — $ — Non-vested restricted stock units at December 31, 2018 72,168 $ 4.59 Performance RSU Activity The following is a summary of all Performance RSU activity during the three years ended December 31, 2018: Restricted Stock Units Weighted Average Fair Value Non-vested performance RSUs at January 1, 2016 182,500 $ 3.88 Granted at market price 22,500 $ 3.61 Vested (97,428 ) $ 3.88 Forfeited (16,741 ) $ 3.88 Non-vested performance RSUs at December 31, 2016 90,831 $ 3.81 Granted at market price 11,500 $ 4.96 Vested (20,999 ) $ 4.08 Forfeited (41,668 ) $ 3.83 Non-vested performance RSUs at December 31, 2017 39,664 $ 3.98 Granted at market price 5,500 $ 4.04 Vested (32,665 ) $ 3.91 Forfeited — $ 0.00 Non-vested performance RSUs at December 31, 2018 12,499 $ 4.20 Performance Stock Activity The following is a summary of all Performance Stock activity during the three years ended December 31, 2018: Restricted Stock Units Weighted Average Fair Value Non-vested performance stock at January 1, 2016 — — Granted at market price 141,500 $ 3.61 Vested (20,000 ) $ 3.61 Forfeited — — Non-vested performance stock at December 31, 2016 121,500 $ 3.61 Granted at market price 112,112 $ 4.96 Vested — — Forfeited (40,502 ) $ 3.61 Non-vested performance stock at December 31, 2017 193,110 $ 4.39 Granted at market price 153,723 $ 4.04 Vested (77,874 ) $ 4.26 Forfeited (13,333 ) $ 4.50 Non-vested performance stock at December 31, 2018 255,626 $ 4.22 The weighted average grant-date fair value of awards of Restricted Stock, RSUs, Performance RSU’s, and Performance Stock is based on the quoted market price of the Company’s common stock on the date of grant.

Supplemental Cash Flow Informat

Supplemental Cash Flow Information	12 Months Ended
	Dec. 31, 2018
Supplemental Cash Flow Elements [Abstract]
Supplemental Cash Flow Information	4. Supplemental Cash Flow Information Supplemental information relating to interest and taxes: Year Ended December 31, (In thousands) 2018 2017 2016 Interest payments $ — $ — $ 33 Income tax payments $ 1,115 $ 636 $ 670

Receivables, Net

Receivables, Net	12 Months Ended
	Dec. 31, 2018
Receivables [Abstract]
Receivables, Net	5. Receivables, net (In thousands) December 31, 2018 2017 Gross accounts receivables $ 14,135 $ 9,307 Allowance for returns and doubtful accounts (277 ) (270 ) Unpaid portion of deferred revenue (10,670 ) (7,648 ) Note receivable 458 458 Allowance for note receivable (458 ) (458 ) Receivables, net $ 3,188 $ 1,389 The allowance for doubtful accounts includes all specific accounts receivable which we believe are likely not collectable based on known information. In addition, we record 2.5% of all accounts receivable greater than 90 days past due, net of those accounts specifically reserved, as a general allowance against accounts that could potentially become uncollectible. The reduction for deferred revenue represents future customer service or maintenance obligations which 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 which 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 December 31, 2018 and 2017.

Prepaid and other current asset

Prepaid and other current assets	12 Months Ended
	Dec. 31, 2018
Deferred Costs Capitalized Prepaid And Other Assets Disclosure [Abstract]
Prepaid and other current assets	6. Prepaid and other current assets (In thousands) December 31, 2018 2017 Prepaid insurance, maintenance, software licenses and other $ 2,460 $ 2,386 Deferred commissions — 415 Tax-related 716 421 Prepaid and other current assets $ 3,176 $ 3,222

Property and Equipment

Property and Equipment	12 Months Ended
	Dec. 31, 2018
Property Plant And Equipment [Abstract]
Property and Equipment	7. Property and Equipment (In thousands) December 31, 2018 2017 Computer and office equipment and software $ 26,762 $ 25,379 Leasehold improvements 6,834 6,763 Furniture and fixtures 2,181 2,136 35,777 34,278 Less accumulated depreciation (31,853 ) (30,230 ) Property and equipment, net $ 3,924 $ 4,048 Our operations include depreciation expense related to property and equipment of $2.4 million, $2.4 million, and $2.3 million in 2018, 2017, and 2016, respectfully.

Other Assets and Deferred Costs

Other Assets and Deferred Costs	12 Months Ended
	Dec. 31, 2018
Deferred Costs Capitalized Prepaid And Other Assets Disclosure [Abstract]
Other Assets and Deferred Costs	8. Other Assets and Deferred Costs As of December 31, 2018, our other assets and deferred costs balance primarily consists of $9.3 million in unamortized contract acquisition costs related to our adoption of ASC 606 as discussed above in Note 2 to the consolidated financial statements.

Goodwill and Other Intangible A

Goodwill and Other Intangible Assets	12 Months Ended
	Dec. 31, 2018
Goodwill And Intangible Assets Disclosure [Abstract]
Goodwill and Other Intangible Assets	9. Goodwill and Other Intangible Assets The changes in the carrying amount of goodwill for the years ended December 31, 2018 and 2017, are as follows: Year Ended December 31, (In thousands) 2018 2017 Opening balance $ 8,469 $ 2,161 Additions 6,215 6,308 Acquisition adjustments (901 ) — Goodwill $ 13,783 $ 8,469 Our 2018 acquisition of Erado (as defined herein) resulted in the addition to our goodwill the increase to our goodwill in 2018. Our acquisition adjustments to goodwill reflect the appropriate reallocation of excess purchase price from goodwill to acquired assets and liabilities related to our 2017 Greenview and EMS (as defined herein) purchases. We evaluate goodwill for impairment annually in the fourth quarter, or when there is reason to believe that the value has been diminished or impaired. There were no impairment indicators to the goodwill recorded as of December 31, 2018. Our other intangible assets consist of the following: December 31, 2018 (In thousands) Gross Carrying Amount Accumulated Amortization Net Carrying Amount Internal use software $ 1,189 $ (162 ) $ 1,027 Internally-developed hosting arrangement 1,520 (77 ) 1,443 Trademarks and other 691 (113 ) 578 Technology 7,604 (2,678 ) 4,926 Customer relationships 7,870 (593 ) 7,277 Intangible assets, net $ 18,874 $ (3,623 ) $ 15,251 For the twelve months ended December 31, 2018, amortization of intangible assets was recorded to the following line items of our consolidated statements of operations: Year Ended December 31, (In thousands) 2018 Cost of revenue $ 368 Research and development expenses 203 Selling, general and administrative expenses 699 Amortization of intangible assets $ 1,270 The following table summarizes our estimated future amortization expense: (In thousands) 2019 2020 2021 2022 2023 Thereafter Total Amortization expense $ 1,670 1,690 $ 1,690 $ 1,481 $ 1,310 $ 7,410 $ 15,251

Accrued Expenses

Accrued Expenses	12 Months Ended
	Dec. 31, 2018
Payables And Accruals [Abstract]
Accrued Expenses	10. Accrued Expenses December 31, (In thousands) 2018 2017 Employee compensation and benefits $ 5,122 $ 4,452 Professional fees 1,289 356 Taxes 113 154 Other 3,223 1,139 Total accrued expenses $ 9,747 $ 6,101

Revenue from Contracts with Cus

Revenue from Contracts with Customers	12 Months Ended
	Dec. 31, 2018
Revenue From Contract With Customer [Abstract]
Revenue from Contracts with Customers	11. 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. Our customer contracts are typically one to three year contracts billed annually. 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 In 2018, we recorded revenue for our services in the following core industry verticals: 49% healthcare, 29% financial services, 7% government sector, and 15% as other. The disaggregation of revenue by industry verticals does not include our revenue from Greenview and Erado. We operate as a single operating segment. Revenue generated from our email protection services represented 100% of our revenue in 2018 and 2017. Further, we sell our solutions as a bundle, applying significant judgement to allocate transaction prices of our services based on the standalone selling price of our component services. Contract balances Our contract assets include our accounts receivable, discussed in Footnote 5 above, and the deferred cost associated with commissions earned by our sales team on securing new, add-on, and renewal contract orders. Upon our adoption of ASC 606, we recorded a cumulative effect adjustment, establishing a $6.6 million noncurrent deferred contract asset in recognition of the lengthened amortization period required by the new guidance. The Company simultaneously released the previously existing current deferred commission asset balance of $415 thousand. During the twelve months ended December 31, 2018, we increased our noncurrent deferred contract asset by $4.9 million, resulting from commissions earned by our sales team during the twelve months ended December 31, 2018. We also amortized $2.2 million of deferred cost, 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 twelve months ended December 31, 2018. Our contract liabilities consist of deferred revenue representing future customer services which have been billed and collected. The $2.7 million increase to our net deferred revenue in the twelve months ended December 31, 2018, is related to the timing of orders and payments as well as growth of revenue. Performance obligations As of December 31, 2018, 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 $73.0 million. We expect to recognize approximately $47.3 million of revenue related to this backlog in 2019, and $25.7 million in periods thereafter. Approximately $45.1 million of our $70.5 million revenue recognized in the twelve months ended December 31, 2018, was included in our performance obligation balance at the beginning of the period.

Fair Value Measurements

Fair Value Measurements	12 Months Ended
	Dec. 31, 2018
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 value 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 value due to their short-term nature. The Company recorded a contingent liability for the estimated fair value of earn-out consideration payments in our Greenview acquisition. The Company determined the fair value of this earn-out liability based on the probability of attainment of certain sales milestones. Any changes to the variables and assumptions could significantly impact the estimated fair values recorded for the liability, resulting in significant changes to the Consolidated Statements of Operations. The fair value measurements are based on significant inputs not observable in the market and thus represent Level 3 measurements, which reflect the Company’s own assumptions concerning the achievement of the sales milestones in measuring the fair value of the acquisition-related contingent earn-out lability. The following table represents a reconciliation of our acquisition-related contingent earn-out liability measured at fair value on a recurring basis, using Level 3 inputs for the year ended December 31, 2018: (In thousands) Fair Value Measurements Using Significant Unobservable Inputs (Level 3) Balance at December 31, 2017 $ 1,488 Additions during the period — Payments during the period (800 ) Adjustments to fair value during the period recorded in General and Administrative expenses 476 Balance at December 31, 2018 $ 1,164

Earnings Per Share and Potentia

Earnings Per Share and Potential Dilution	12 Months Ended
	Dec. 31, 2018
Earnings Per Share [Abstract]
Earnings Per Share and Potential Dilution	13. Earnings Per Share and Potential Dilution Basic earnings per share are computed using the weighted average number of common shares outstanding for the period under the Treasury Stock method. The dilutive effect of potential common shares outstanding is included in diluted earnings per share. The computations for basic and diluted earnings per share for the years ended December 31, 2018, 2017, and 2016, are as follows: Year Ended December 31, 2018 2017 2016 Basic weighted average shares 52,591,714 53,430,492 53,819,772 Effect of dilutive securities: Employee and director stock options 347,167 — 317,329 Restricted Stock 409,871 — 149,817 RSUs 24,369 — 63,484 Performance RSUs 9,367 — 24,449 Performance Stock 98,807 — 20,294 Potential dilutive common shares 53,481,295 53,430,492 54,395,145 For the year ended December 31, 2018, weighted average shares related to 73,313 stock options; 131,774 shares of Restricted Stock, 6,084 RSUs, 917 Performance RSUs, and 18,536 shares of Performance Stock were excluded from the calculation of diluted earnings per share because these awards were anti-dilutive. For the year ended December 31, 2017, potential common shares of all securities were excluded from the calculation of diluted earnings per share because the awards were anti- dilutive. For the year ended December 31, 2016, weighted average shares related to 1,079,474 stock options; 109,293 shares of Restricted Stock, 20,600 RSUs, 886 Performance RSUs, and 5,572 shares of Performance Stock, respectively were excluded from the calculation of diluted earnings per share because these awards were anti-dilutive .

Significant Customers

Significant Customers	12 Months Ended
	Dec. 31, 2018
Text Block [Abstract]
Significant Customers	14. Significant Customers In 2018, 2017, and 2016, no single customer accounted for 10% or more of our revenues.

Commitments and Contingencies

Commitments and Contingencies	12 Months Ended
	Dec. 31, 2018
Commitments And Contingencies Disclosure [Abstract]
Commitments and Contingencies	15. Commitments and Contingencies Leases We lease office facilities under non-cancelable operating lease agreements. Our operations include rent expense for these operating leases of $1.6 million, $1.4 million, and $1.4 million in 2018, 2017, and 2016 respectively. The lease of our headquarters facility in Dallas expires in 2024. A summary of our fixed contractual obligations and commitments at December 31, 2018, is as follows: (In thousands) 2019 2020 2021 2022 2023 Thereafter Total Operating leases $ 1,625 $ 1,220 $ 1,072 $ 1,089 $ 1,116 $ 861 $ 6,983 Claims and Proceedings We are subject to legal proceedings, claims, and litigation against our business. While the outcome of these matters is currently not determinable and the costs and expenses of defending these matters may be significant, we currently do not expect that the ultimate costs to resolve these matters will have a material adverse effect on our consolidated financial statements.

Other Comprehensive Loss

Other Comprehensive Loss	12 Months Ended
	Dec. 31, 2018
Other Comprehensive Income Loss Tax [Abstract]
Other Comprehensive Loss	16. 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. Related translation adjustments are recorded as a component of the accumulated other comprehensive loss. Our Consolidated Statement of Comprehensive Income of international subsidiaries are translated from the local currency to the U.S. dollar using average exchange rates for the period covered by the income statements. We are exposed to fluctuations in the foreign currency exchange rates as a result of our net investments and operations in Canada. For fiscal 2018, movements in currency exchange rates and the related impact on the translation of the balance sheets of our subsidiary in Canada was the primary cause of our foreign currency translation loss of $16 thousand, net of $26 thousand in income taxes.

Income Taxes

Income Taxes	12 Months Ended
	Dec. 31, 2018
Income Tax Disclosure [Abstract]
Income Taxes	17. Income Taxes Components of the income taxes are as follows: (In thousands) 2018 2017 2016 Current: U.S. $ (794 ) $ 183 $ 100 State 725 (196 ) 329 Foreign 71 156 75 Deferred Federal (4,722 ) 18,461 3,185 Foreign — 2 3 Income tax (benefit) expense $ (4,720 ) $ 18,606 $ 3,692 On December 22, 2017, the U.S. enacted the Tax Cuts and Jobs Act of 2017 (the “Tax Act”) which significantly changed U.S. tax law. The Tax Act, among other things, lowered the federal statutory corporate income tax rate from 34% to 21% effective January 1, 2018. The Company completed its assessment of the impact to 2018 noting no changes from what it disclosed in 2017. The Company’s income tax expense (benefit) for 2018, 2017 and 2016, respectively, reflect tax expense (benefit) based on statutory rates in 2018, 2017, and 2016. A reconciliation of the expected U.S. tax expense (benefit) to income taxes related to continuing operations is as follows: (In thousands) 2018 2017 2016 Expected tax expense at U.S. statutory rate $ 2,260 $ 3,587 $ 3,250 Change in corporate tax rate- deferreds — 12,473 — Increase (decrease) in valuations allowance (7,841 ) — — Increase (decrease) in valuations allowance- other — 2,064 — Nondeductible expense and nontaxable income 111 890 114 State income taxes, net of federal benefits 815 (129 ) 217 Foreign income taxes 68 159 78 Other (133 ) (438 ) 33 Income tax (benefit) expense $ (4,720 ) $ 18,606 $ 3,692 $7.8 million of the valuation allowance was reversed in 2018 based on current and expected future profitability. Deferred income taxes reflect the net tax effects of temporary differences between the carrying amounts of assets and liabilities for financial reporting purposes and the amounts used for income tax purposes. Components of our U.S. deferred income taxes as of December 31, 2018 and 2017 are as follows: (In thousands) 2018 2017 Deferred tax assets: Nondeductible $ 113 $ 112 U.S. net operating loss carryforwards 46,826 48,769 State net operating loss carryforwards 71 321 Tax credit carryforwards 5,703 6,450 Stock-based compensation 976 750 Depreciable assets 822 851 Other assets 938 1,039 Total deferred tax assets 55,449 58,292 Deferred tax liabilities: Intangible assets (3,428 ) (1,342 ) Prepaid expenses (572 ) (532 ) Total deferred tax assets 51,449 56,418 Less valuation allowance (22,667 ) (30,773 ) Net deferred tax assets $ 28,782 $ 25,645 The Company has partially reserved its U.S. net deferred tax assets in 2018 and 2017 due to the uncertainty of future taxable income. The Company has U.S. net operating loss carryforwards of approximately $223 million which begin to expire in 2021. The Company has state credits totaling $2.0 million which can be utilized through 2027 and state net operating losses that have various expiration dates. The Company also has tax credit carryforwards of approximately $3.7 million consisting of business tax credits that began to expire in 2018 and alternative minimum tax credits which will be refunded through 2021 in accordance with the new tax law effective 2018. We have determined that utilization of existing net operating losses against future taxable income is not limited by Section 382 of the Internal Revenue Code. Future ownership changes, however, may limit the Company's ability to fully utilize its existing net operating loss carryforwards against any future taxable income. The Company or one of our subsidiaries files income tax returns in the U.S. federal jurisdiction and various states and in the Canadian federal and provincial jurisdictions. We have not taken a tax position that, if challenged, would have a material effect on the financial statements or the effective tax rate for the twelve-months ended December 31, 2018, or during the prior three years. We have determined it is not reasonably possible for the amounts of unrecognized tax benefits to significantly increase or decrease within the next twelve months. We are currently subject to a three-year statute of limitations by major tax jurisdictions.

Employee Benefit Plan

Employee Benefit Plan	12 Months Ended
	Dec. 31, 2018
Postemployment Benefits [Abstract]
Employee Benefit Plan	18. Employee Benefit Plan 401(k) Plan — We have a retirement savings plan structured under Section 401(k) of the Internal Revenue Code covering substantially all of our U.S. employees. Under the plan, contributions are voluntarily made by employees, and we may provide contributions based on the employees’ contributions. Our operating income includes $611 thousand, $512 thousand, and $448 thousand in 2018, 2017, and 2016, respectively, for net contributions from operations to this plan.

Zix Repurchase Program

Zix Repurchase Program	12 Months Ended
	Dec. 31, 2018
Equity [Abstract]
Zix Repurchase Program	19. Zix Repurchase Program On April 24, 2017, the Company’s Board of Directors approved a share repurchase program that enables the Company to purchase up to $10 million of its shares of common stock. The shares repurchase program expired on May 31, 2018. During the year ended December 31, 2018, the Company repurchased 1,206,994 shares at an aggregate cost of $5.4 million. During the year ended December 31, 2017, the Company repurchased 750,000 shares at an aggregate cost of $3.8 million.

Acquisitions

Acquisitions	12 Months Ended
	Dec. 31, 2018
Business Combinations [Abstract]
Acquisitions	20. Acquisitions Greenview Data, Inc. On March 15, 2017, the Company acquired all of the outstanding capital stock of Greenview Data, Inc. (“Greenview”), a provider of antivirus, anti-spam, and archiving products, for a total purchase price of $7.7 million, including cash consideration of $6.7 million, subject to a customary post-closing adjustment for working capital. Our acquisition of Greenview addresses increasing buyer demand for email security bundles by adding these capabilities to our existing portfolio of encryption services. Of the cash consideration paid, $650 thousand was deposited into an escrow account for the satisfaction of certain indemnification claims of the Company, if any, during the two year period following the closing of the acquisition, after which the balance, if any, will be distributed to the selling shareholders. Because sales of Greenview products met certain sales milestones by December 31, 2017, the Company was contractually obligated to pay earn-out consideration in cash of $800 thousand in the first quarter 2018. The Company is also required to pay a further $800 thousand of earn-out consideration in cash in the first quarter of 2019 because sales of the Greenview products achieved a separate target by December 31, 2018. Contingent consideration is considered a Level 3 fair value measurement. We accounted for the acquisition as the purchase of a business and recorded the excess purchase price as goodwill. The goodwill from this transaction is not deductible for tax purposes. The intangible assets we acquired from Greenview consist of trademarks, internally developed software, and customer relationships, which we are amortizing over an estimated useful life of 5 years, 10 years, and 15 years, respectively. The results of operations and the estimated fair values of the acquired assets and liabilities assumed have been included in the accompanying consolidated financial statements since our March 15, 2017, acquisition date. The Company incurred $476 thousand and $427 thousand in acquisition-related costs in which was recorded within operating expenses for the year ended December 31, 2018 and 2017, respectively. Revenue from Greenview was $3.4 million and $2.4 million for the year ended December 31, 2018 and 2017, respectively, and due to the continued integration of the combined businesses, it was impracticable to determine the earnings. The following table summarizes the estimated fair value of acquired assets and liabilities: (In thousands) Estimated Fair Value Assets: Current assets $ 334 Property and equipment 249 Trademark/names 170 Technology 1,990 Customer relationships 2,880 Goodwill 4,343 Total assets 9,966 Liabilities: Deferred revenue $ 537 Other current liabilities 124 Deferred tax liability 1,609 Total liabilities 2,270 Net assets recorded $ 7,696 Entelligence Messaging Server On September 13, 2017, the Company acquired Entelligence Messaging Server (“EMS”) technology, an email encryption solution, and the related business from Entrust Datacard Corporation for a cash purchase price of $1.7 million. Our acquisition of EMS strengthens our email encryption suite by offering enterprise-centric capabilities, such as advanced message tracking, PDF statement delivery, high availability on-premises architecture and standards-based end-to-end encryption. The Company incurred $58 thousand and $59 thousand in acquisition-related costs which were recorded within operating expenses for the year ended December 31, 2018 and 2017, respectively. We accounted for the acquisition as the purchase of a business and recorded the excess purchase price as goodwill. The goodwill from this transaction is deductible for tax purposes. The results of operations and the estimated fair values of the acquired assets and liabilities assumed have been included in the accompanying consolidated financial statements since our September 13, 2017, acquisition date. Revenue from EMS was not material for the year ended December 31, 2018 and 2017, respectively, and due to the continued integration of the combined businesses, it was impracticable to determine the earnings. The following table summarizes the estimated fair value of acquired assets and liabilities: (In thousands) Estimated Fair Value Assets: Trademark/names $ 140 Technology 550 Customer relationships 230 Goodwill 1,063 Total assets 1,983 Liabilities: Deferred revenue $ 333 Total liabilities 333 Net assets recorded $ 1,650 Erado On April 2, 2018, the Company acquired all the outstanding capital stock of CM2.COM, Inc., d/b/a Erado (“Erado”) for a total purchase price of $14.4 million, including cash consideration of $11.8 million, net of cash acquired. The purchase of Erado strengthens Zix’s comprehensive archiving solutions with unified archiving, supervision, security, and messaging solutions for customers that demand bundled services. Erado’s long standing focus on helping its customers comply with FINRA and SEC regulations will help further strengthen Zix’s offering for customers with compliance requirements. This acquisition also expands Zix’s cloud-based email archiving capabilities into more than 50 content channels, including social medial, instant message, mobile, web, audio, and video. The purchase price includes a holdback of $2.3 million for the satisfaction of certain indemnification claims by the Company, if any, during the two-year period following the closing of the acquisition. An amount equal to $1.1 million of the holdback amount, less any amounts paid or otherwise subject to an outstanding claim for indemnification, will be released to the selling shareholders upon the one year anniversary of the closing of the acquisition, and the balance of the holdback amount, if any, will be distributed to the Selling Shareholders following the two year anniversary of the closing of the acquisition. The Company incurred $334 thousand in acquisition-related costs which were recorded within operating expenses during twelve months ended December 30, 2018. We accounted for the acquisition as the purchase of a business and recorded the excess purchase price as goodwill. The goodwill from this transaction is deductible for tax purpose. The intangible assets we acquired from Erado consist of trademarks, internally developed software, and customer relationships, which we are amortizing over an estimated useful life of 5 years, 10 years, and 15 years, respectively. The results of operations and the estimated fair values of the acquired assets and liabilities have been included in the accompanying consolidated financial statements since our April 2, 2018, acquisition date. Revenue from Erado was $2.1 million for the twelve months ended December 31, 2018, since the acquisition date. Due to the continued integration of the combined businesses, it was impracticable to determine the earnings. The following table summarizes the estimated fair value of acquired assets and liabilities: (In thousands) Estimated Fair Value Assets: Current assets $ 848 Property and equipment 169 Trademark/names 260 Technology 3,030 Customer relationships 4,760 Goodwill 6,215 Total assets 15,282 Liabilities: Deferred revenue $ 809 Other current liabilities 93 Total liabilities 902 Net assets recorded $ 14,380 Pro Forma Financial Information (Unaudited) The following unaudited pro forma financial information presents the combined results of operations for the twelve month periods ending December 31, 2018, and 2017, respectively, as though the Erado, EMS and Greenview acquisitions that occurred during the reporting period had occurred as of the beginning of the earliest period presented, with adjustments to give effect to pro forma events that are directly attributable to the acquisition, such as amortization expense of intangible assets and acquisition-related transaction costs. 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 acquisition had occurred at the beginning of the earliest period presented, nor are they indicative of future results of operations: Twelve Months Ended December 31, (In thousands, except per share data) 2018 2017 Revenues $ 71,762 $ 69,587 Net income (loss) 18,330 (6,981 ) Basic income (loss) per common share $ 0.35 $ (0.13 ) Diluted income (loss) per common share $ 0.34 $ (0.13 )

Quarterly Results of Operations

Quarterly Results of Operations (Unaudited)	12 Months Ended
	Dec. 31, 2018
Quarterly Financial Information Disclosure [Abstract]
Quarterly Results of Operations (Unaudited)	21. Quarterly Results of Operations (Unaudited) The following is a summary of the quarterly results of operations for the years ended December 31, 2018 and 2017: Quarter Ended (In thousands except per share data) March 31 June 30 September 30 December 31 2018 Revenues $ 16,654 $ 17,500 $ 17,876 $ 18,448 Gross margin 13,140 13,694 14,006 14,451 Net income (loss) 1,892 1,840 2,455 9,240 Basic net income (loss) per common share* 0.04 0.04 0.05 0.18 Diluted net income (loss) per common share* 0.04 0.03 0.05 0.17 Comprehensive Income — — — 9,224 2017 Revenues $ 15,893 $ 16,378 $ 16,592 $ 16,800 Gross margin 13,070 13,131 13,320 13,540 Net income (loss) 1,775 1,139 1,905 (12,877 ) Basic net income (loss) per common share* 0.03 0.02 0.04 (0.24 ) Diluted net income (loss) per common share* 0.03 0.02 0.03 (0.24 ) Comprehensive Income — — — — * Net income (loss) per share is calculated independently for each quarter. The sum of Net income (loss) per share for each quarter may not equal the total Net income (loss) per share for the year due to rounding differences.

Subsequent Events

Subsequent Events	12 Months Ended
	Dec. 31, 2018
Subsequent Events [Abstract]
Subsequent Events	22. Subsequent Events 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”). Zix paid $275 million in cash, less outstanding indebtedness of the AppRiver Companies retired at closing and certain accrued items and unpaid transaction expenses, and subject to a customary working capital adjustment. The Company is currently in the process of determining the fair value of the assets and liabilities acquired in the AppRiver purchase. Also on February 20, 2019, Zix entered into a credit agreement with a syndicate of lenders and SunTrust Bank, as administrative agent, providing Zix with (1) a senior secured term loan facility in an aggregate principal amount of $175 million (the “Term Loan”), (2) a senior secured delayed draw term loan facility in an aggregate principal amount of $10 million, and (3) 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. 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. The AppRiver acquisition was further funded by the February 20, 2019 private placement of preferred stock with an investment fund managed by True Wind Capital. Zix issued shares of its Series A Convertible Preferred Stock, $1.00 par value per share, and its Series B Convertible Preferred Stock, $1.00 par value per share, at a price of $1,000 per share for an aggregate purchase price of $100 million. 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 the company’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.

Summary of Significant Accoun_2

Summary of Significant Accounting Policies (Policies)	12 Months Ended
	Dec. 31, 2018
Accounting Policies [Abstract]
Basis of Presentation	Basis of Presentation — The accompanying consolidated financial statements include the accounts of all our wholly-owned subsidiaries and are prepared in accordance with accounting principles generally accepted in the United States of America (“U.S. GAAP”). All inter-company accounts and transactions have been eliminated in consolidation.
Use of Estimates	Use of Estimates — The preparation of consolidated financial statements in conformity with accounting principles generally accepted in the United States of America requires management to make estimates and assumptions that affect the reported amount of assets and liabilities and disclosure of contingent assets and liabilities at the date of the consolidated financial statements and the reported amounts of revenue and expenses during the reported period. Our significant estimates include primarily those required in the valuation or impairment analysis of goodwill and intangibles, property and equipment, revenue recognition, amortization period of our commission amortization, allowances for doubtful accounts, stock-based compensation, litigation accruals, valuation allowances for deferred tax assets and tax accruals. Although we believe that adequate accruals have been made for unsettled issues, additional gains or losses could occur in future years from resolutions of outstanding matters. Actual results could differ materially from original estimates.
Cash Equivalents	Cash Equivalents — Cash investments with maturities of three months or less when purchased are considered cash equivalents
Fair Value of Financial Instruments	Fair Value of Financial Instruments —The Company does not measure the fair value of any financial instrument other than cash equivalents, options, and other equity awards. The carrying values of other financial instruments (receivables and accounts payable) are not recorded at fair value but approximate fair values primarily due to their short-term nature. 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.
Valuation of Property and Equipment	Valuation of Property and Equipment — The accounting policies and estimates relating to property and equipment are considered significant because of the potential impact that impairment, obsolescence, or change in an asset’s useful life could have on the Company’s operating results. We record an impairment charge on the assets to be held and used when we determine based upon certain triggering events that the carrying value of property and equipment may not be recoverable based on expected undiscounted cash flows attributable to such assets. The amount of a potential impairment is determined by comparing the carrying amount of the asset to either the value determined from a projected discounted cash flow method, using a discount rate that is considered to be commensurate with the risk inherent in the Company’s current business model or the estimated fair market value. Assumptions are made with respect to future net cash flows expected to be generated by the related asset. An impairment charge would be recorded for an amount by which the carrying value of the asset exceeded the discounted projected net cash flows or estimated fair market value. Also, even where a current impairment charge is not necessary, the remaining useful lives are evaluated. No impairment was recorded for any of the periods presented. Property and equipment are recorded at cost and depreciated or amortized using the straight-line method over their estimated useful lives as follows: computer and office equipment and software — three years; leasehold improvements — the shorter of five years or the lease term; and furniture and fixtures — five years. We recorded a depreciation expense of $2.4 million for the year ended December 31, 2018. We allocated $1.7 million of the expense to cost of revenue, $426 thousand to research and development expense, and $314 thousand to selling, marketing, and general and administrative expenses.
Goodwill and Other Intangible Assets	Goodwill and Other Intangible Assets — We account for the valuation of goodwill and other intangible assets after classifying intangible assets into three categories: (1) intangible assets with finite lives subject to amortization; (2) intangible assets with indefinite lives not subject to amortization; and (3) goodwill. For intangible assets with finite lives, tests for impairment must be performed if conditions exist that indicate the carrying value may not be recoverable. For intangible assets with indefinite lives and goodwill, tests for impairment must be performed at least annually or more frequently if events or circumstances indicate that assets might be impaired. Goodwill was $13.8 million, or 13%, and $8.5 million, or 10%, of total assets as of December 31, 2018 and 2017, respectively. We evaluate the goodwill for impairment annually in the fourth quarter, or when there is reason to believe that the value has been diminished or impaired. Evaluations for possible impairment are based upon a comparison of the estimated fair value of the reporting unit to which the goodwill has been assigned, versus the sum of the carrying value of the assets and liabilities of that unit including the assigned goodwill value. We include our entire Company as the reporting unit. The fair values used in this evaluation are estimated based on the Company’s market capitalization, which is based on the outstanding stock and market price of the stock. Impairment is deemed to exist if the net book value of the unit exceeds its estimated fair value. No impairment was recorded for any of the periods presented. Our intangible assets with finite lives are amortized using a straight line basis over their economic useful lives.
Deferred Tax Assets	Deferred Tax Assets — Deferred tax assets are recognized if it is “more likely than not” that the benefit of our deferred tax assets will be realized on future federal or state income tax returns. At December 31, 2018, we provided a valuation allowance against a significant portion, $22.7 million, of our accumulated U.S. deferred tax assets, reflecting our historical losses and the uncertainty of future taxable income sufficient to utilize net operating loss carryforwards prior to their expiration. Our total deferred tax assets not subject to a valuation allowance are valued at $28.8 million, and consist of $27.0 million for federal net operating loss carryforwards , $2.1 million relating to U.S. state income tax credits, $678 thousand related to Alternative Minimum Tax credits and $114 thousand related to foreign tax credits. These credits are offset by ($1.2) million relating to temporary timing differences between U.S. GAAP and tax-related expense. If our U.S. taxable income increases from its current level in a future period or if the facts and circumstances on which our estimates and assumptions are based were to change, thereby impacting the likelihood of realizing our deferred tax assets, judgment would have to be applied in determining the amount of valuation allowance no longer required. Reversal of all or a part of this valuation allowance could have a significant positive impact on operating results in the period that it becomes more likely than not that certain of the Company’s deferred tax assets will be realized. Alternatively, should our future income decrease from current levels, a resulting increase to all or a part of this valuation allowance could have a significant negative impact on our operating results
Uncertain Tax Positions	Uncertain Tax Positions — Our Company recognizes and measures uncertain tax positions using a two-step approach. The first step is to evaluate the tax position for recognition by determining if the weight of available evidence indicates that it is more likely than not that the position will be sustained on audit, including resolution of related appeals or litigation processes, if any. The second step is to measure the tax benefit as the largest amount that is more than 50% likely of being realized upon settlement.
Leases	Leases — A leased asset whose lease terms meet the criteria for capitalization is recorded as an asset and depreciated. If a lease does not meet the criteria for capitalization, it is classified as an operating lease and payments are recorded as rent expense. For 2018 and 2017 we had no leases that qualified as capital leases. Lease renewal options which we are “reasonably assured” of using and the related payments are taken into account when initially classifying and recording the lease as a capital lease obligation or as straight-line rent if an operating lease. Funds provided by the lessor for leasehold improvements are recorded as a deferred lease incentive and amortized as a reduction of rent expense over the lease term. Leases In February 2016, the FASB issued ASU 2016-02, Leases (Topic 842). Topic 842 requires companies to generally recognize on the balance sheet operating and financing lease liabilities and corresponding right-of-use assets. The new lease standard becomes effective for us beginning 2019. We expect to adopt Topic 842 using the effective date as the date of our initial application of the standard. Consequently, financial information for the comparative periods will not be updated. We currently expect that most of our operating lease commitments will be subject to the new standard and recognized as operating lease liabilities and right-of-use assets upon our adoption of Topic 842. We are evaluating the potential impact of this new guidance on our consolidated financial statements, and currently estimate the recognition of our outstanding lease obligations as of December 31, 2018, will result in the recognition of right-to-use-assets and lease liabilities of $4.5 million to $6.5 million.
Revenue Recognition	Revenue Recognition — In May 2014, The Financial Accounting Standards Board (“FASB”) issued ASC 606 which requires revenue recognition when promised goods or services are transferred to customers in an amount that reflects the consideration to which an entity expects to be entitled to those goods and services. The standard became effective for us in 2018, but did not have a material impact to our revenue recognition process. For additional information regarding our adoption of ASC 606 please see “New Accounting Standards.” We earn our revenue from subscription fees for rights related to the use of our software. Our revenue contracts include multiple performance obligations that are highly interdependent and consists of software at the customer’s site, ongoing customer support, and cloud-based access to the hosted Zix encryption network. As our Company has expanded its portfolio of message security offerings in recent years, we have increased our revenue obtained from hosted service solutions. Approximately 38% of our revenue in 2018 was derived from hosted email protection solutions. Our subscription terms typically range from one to five years. Revenue is recognized by applying the following steps: • Step 1: Identify the contract(s) with a customer, • Step 2: Identify the performance obligations in the contract, • Step 3: determine the transaction price • Step 4: allocate the transaction price to the performance obligations in the contract, and • Step 5: recognize revenue when (or as) the performance obligation is satisfied. • Step 1: Identify the contract(s) with a customer: We consider the terms and conditions of the contract and our customary business practice in identifying our contracts. We determine we have a contract with a customer when the contract is approved, we can identify each party’s rights regarding the services and products transferred, we can identify the payment terms for the services and products, the contract has commercial substance, and it is probable we will be paid. • Step 2: Identifying the performance obligations: ASC 606 requires identification and disclosure of performance obligations within a revenue contract. A good or service is considered distinct if the customer can both benefit from the good or service on its own or with other resources that are readily available to the customer, and the promise to transfer the good or service is separately identifiable from other promises in the contract. As of December 31, 2018, revenue from our email protection services represent 100% of our revenue, of which approximately 88% is specific to email encryption. To provide this service, our software at the customer site includes functionality to create a private encryption key that works in conjunction with the public encryption key provided via cloud-based access to our hosted Zix encryption network. Both keys are required to enable our asymmetrical encryption service. In our assessment of the factors listed in ASC 606-10-25-21, we have determined that because our software at the customer’s site and the access to our hosted Zix encryption network are highly interrelated, these items are not regarded as distinct components. Based on this assessment, these elements are combined as a single performance obligation. • Step 3: Determine the transaction price: The transaction price is determined based on the consideration we expect to be entitled to receive in exchange for transferring goods and services to the customer. We include variable consideration in the transaction price if we view it as probable that a significant future reduction of cumulative revenue under the contract will not occur. • Step 4: Allocate the transaction price to the performance obligations in the contract: We allocate transaction prices to each performance obligation based on the stand-alone selling price of our component services. • Step 5: Recognize revenue when (or as) the performance obligation is satisfied: We recognize revenue when the customer obtains control of the product or services, at the amount allocated to the satisfied performance obligation. Our performance obligations are generally satisfied over time. While some contracts include one or more performance obligations (including the combined elements noted above along with additional ongoing customer support and other hosted services), the revenue recognition pattern generally is not impacted by the separate allocations of these obligations because the services are generally satisfied over the same period of time and revenue is recognized over the contract period. Discounts provided to customers are recorded as reductions in revenue. Revenue Recognition In May 2014, the FASB issued ASC 606, which supersedes most prior revenue recognition guidance under U.S. Generally Accepted Accounting Principles (“GAAP”). The core principle of ASC 606 is to recognize revenues when promised goods or services are transferred to customers in an amount that reflects the consideration to which an entity expects to be entitled for those goods or services. ASC 606 defines a five step process to achieve this core principle and, in doing so, more judgment and estimates may be required within the revenue recognition process than were required under prior U.S. GAAP. The standard became effective for us beginning in 2018. Our Company provides primarily email encryption and advanced threat protection security solutions as subscription services in which we recognize revenue as our services are rendered. We determined our revenue was not materially impacted by the new guidance. However, the guidance did require us to increase the amortization period of our commission expense. We applied the guidance to commissions earned on all contracts that were not complete as of January 1, 2018. Prior period amounts were not adjusted and continue to be reported in accordance with the previous guidance. Our Company elected to use a portfolio approach, applying 8 year, 4 year, and 18 month amortization periods for our new, add-on, and renewal sales commission expenses, respectively. Determination of the amortization period and the subsequent assessments for impairment of the related deferred cost asset requires significant judgement. We applied a modified retrospective approach to our implementation of ASC 606 in which we recognized a $4.6 million cumulative effect adjustment to our 2018 retained earnings opening balance related to our increased amortization period. This adjustment includes a $1.6 million impact to our deferred tax asset. The table below presents the cumulative effect of the changes made to our consolidated balance sheet due to the adoption of ASC 606: (In thousands) January 1, 2018 Beginning Balance Cumulative Effect Adjustment Beginning Balance, as Adjusted Assets: Prepaid and other current assets $ 3,222 $ (415 ) $ 2,807 Other assets and deferred costs — 6,595 6,595 Deferred tax assets 25,647 (1,616 ) 24,031 Stockholders’ equity: Accumulated deficit $ (236,372 ) $ 4,564 $ (231,808 ) Financial statement results as reported under the new revenue standard as compared to the previous standard for the twelve months ended and as of December 31, 2018, are as follows: Twelve Months Ended December 31, 2018 (In thousands, except per share data) Under ASC 605 Under ASC 606 Variance Revenues $ 70,478 $ 70,478 $ — Cost of revenues 15,186 15,186 — Gross margin 55,292 55,292 — Operating expenses: Research and development 11,323 11,323 — Selling, general and administrative 36,554 33,999 (2,555 ) Total operating expenses 47,877 45,322 (2,555 ) Operating income 7,415 9,970 2,555 Other income, net 754 754 — Income before income taxes 8,169 10,724 2,555 Income tax expense 5,257 4,720 (537 ) Net income $ 13,426 $ 15,444 $ 2,018 Basic income per common share $ 0.26 $ 0.29 0.04 Diluted income per common share $ 0.25 $ 0.29 0.04 (1) (In thousands) December 31, 2018 Under ASC 605 Under ASC 606 Variance Assets: Prepaid and other current assets $ 3,760 $ 3,176 $ (584 ) Other assets and deferred costs — 9,424 9,424 Deferred tax assets 30,401 28,785 (1,616 ) Stockholders’ equity: Accumulated deficit $ (222,946 ) $ (216,364 ) $ 6,582
Commission Amortization	Commission Amortization — We amortize our commission costs to expense on a systemic basis over the period of expected benefit to the customer. Determination of the amortization period requires significant judgement. We apply the practical expedient noted in ASC 606-10-10-4 to account for our commission costs and related amortizations at the portfolio level. Additionally, the Company has evaluated commissions earned upon contract renewal as compared to initial commissions paid and determined that because commissions paid were not reasonably proportional to their respective contract values, our renewal commissions could not be considered commensurate with the initial commissions paid. We considered our average contract term length and historical customer retention rates to determine an average length of our customer relationships. We also concluded our add-on sales generally occur halfway into our customer relationships, and evaluated our average customer renewal terms. Based on these factors we have determined that 8 years, 4 years and 18 months are the appropriate amortization periods to our new, add-on, and renewal sales commission expenses, respectively. We also perform subsequent assessments for impairment of the related deferred cost asset when indicators present.
Software Development Costs	Software Development Costs —Costs incurred in the development and testing of subscription software products related to research, project planning, training, maintenance and general and administrative activities, and overhead costs are expensed as incurred. The costs of relatively minor upgrades and enhancements to the software are also expensed as incurred. Costs for the development of new software solutions and substantial enhancements to existing software solutions are expensed as incurred until technological feasibility has been established, at which time any additional costs would be capitalized. Historically, we have not capitalized standard research and development costs because we believe that technological feasibility is established concurrent with general release to customers. Research and development costs associated with software developed for internal use on behalf of our customers are capitalized. As we increasingly moved to a multi-tenant environment to keep up with the industry trend requiring transition to a cloud based solution for our existing services, certain research and development expenditures associated with hosting arrangements began to meet the accounting guidance requirement for capitalizing development costs under ASC 350-40, Internal-Use Software, as it applies to hosting arrangements. These capitalized costs are classified as intangible assets in our consolidated balance sheet. In 2018, we capitalized $1.5 million of research and development costs related to hosted software development for our customers. The Company expects our capitalization of these research and development expenditures to increase in the future.
Advertising Expense	Advertising Expense — Advertising costs are expensed as incurred. Our operations include advertising expense of $1.3 million, $1.5 million, and $1.9 million in 2018, 2017, and 2016, respectively
Stock-Based Compensation	Stock-Based Compensation — We currently use the straight-line amortization method for recognizing stock option and restricted stock compensation costs. The measurement and recognition of compensation expense for all share-based payment awards made to our employees and directors are based on the estimated fair value of the awards on the grant dates. The grant date fair value is estimated using either an option-pricing model which is consistent with the terms of the award or a market observed price, if such a price exists. Such cost is recognized over the period during which an employee or director is required to provide service in exchange for the award, i.e., “the requisite service period” (which is usually the vesting period). We also estimate the number of instruments that will ultimately be earned, rather than accounting for forfeitures as they occur.
Earnings Per Share ("EPS")	Earnings Per Share (“EPS”) — Basic EPS is based on the weighted average number of common shares outstanding during each period. Diluted EPS adjusts Basic EPS for the effects of dilutive common stock equivalents outstanding during each period using the treasury stock method.
Cash Flow Statement	Cash Flow Statement In August 2016, the FASB issued ASU No. 2016-15, Statement of Cash Flows (Topic 230), which amends guidance on the classification of certain cash receipts and payments in the statement of cash flows. This ASU was issued with the intent to reduce diversity in practice with respect to eight types of cash flows. The new guidance addressed debt prepayment or extinguishment of costs, settlement of zero-coupon bonds, contingent consideration made after a business combination, proceeds from the settlement of insurance claims, proceeds from the settlement of corporate-owned life insurance policies and bank-owned life insurance policies, distributions received from equity method investees, beneficial interests in securitization transactions, and separately identifiable cash flows and application of the predominance principle. The standard became effective for us beginning in 2018. We applied the new guidance within our consolidated statements of cash flows classification to an $800 thousand earn-out payment associated with our Greenview (as defined herein) acquisition. Because this consideration payment was not made soon after the consummation date, as required by the guidance, we classified $605 thousand of the payment as a financing activity. This reflects the portion of the payment recognized a contingent liability as of the acquisition date. The $195 thousand balance of the payment was in excess of the original contingent consideration liability and was classified as an operating activity. The standard had no other impact on our consolidated financial statements.
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 value 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 value due to their short-term nature.

Summary of Significant Accoun_3

Summary of Significant Accounting Policies (Tables)	12 Months Ended
	Dec. 31, 2018
ASC 606 [Member]
Summary of Impact on Financial Statements Due to Adoption of ASC 606	The table below presents the cumulative effect of the changes made to our consolidated balance sheet due to the adoption of ASC 606: (In thousands) January 1, 2018 Beginning Balance Cumulative Effect Adjustment Beginning Balance, as Adjusted Assets: Prepaid and other current assets $ 3,222 $ (415 ) $ 2,807 Other assets and deferred costs — 6,595 6,595 Deferred tax assets 25,647 (1,616 ) 24,031 Stockholders’ equity: Accumulated deficit $ (236,372 ) $ 4,564 $ (231,808 ) Financial statement results as reported under the new revenue standard as compared to the previous standard for the twelve months ended and as of December 31, 2018, are as follows: Twelve Months Ended December 31, 2018 (In thousands, except per share data) Under ASC 605 Under ASC 606 Variance Revenues $ 70,478 $ 70,478 $ — Cost of revenues 15,186 15,186 — Gross margin 55,292 55,292 — Operating expenses: Research and development 11,323 11,323 — Selling, general and administrative 36,554 33,999 (2,555 ) Total operating expenses 47,877 45,322 (2,555 ) Operating income 7,415 9,970 2,555 Other income, net 754 754 — Income before income taxes 8,169 10,724 2,555 Income tax expense 5,257 4,720 (537 ) Net income $ 13,426 $ 15,444 $ 2,018 Basic income per common share $ 0.26 $ 0.29 0.04 Diluted income per common share $ 0.25 $ 0.29 0.04 (1) (In thousands) December 31, 2018 Under ASC 605 Under ASC 606 Variance Assets: Prepaid and other current assets $ 3,760 $ 3,176 $ (584 ) Other assets and deferred costs — 9,424 9,424 Deferred tax assets 30,401 28,785 (1,616 ) Stockholders’ equity: Accumulated deficit $ (222,946 ) $ (216,364 ) $ 6,582

Stock Options and Stock-Based_2

Stock Options and Stock-Based Employee Compensation (Tables)	12 Months Ended
	Dec. 31, 2018
Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]
Summary of Common Stock Options Outstanding	Below is a summary of common stock options outstanding at December 31, 2018: Authorized Shares Options Outstanding Options Vested Available for Grant Employee and Director Stock Option Plans: 2004 Stock Option Plan 5,000,000 230,000 230,000 — 2006 Director’s Stock Option Plan 1,100,000 55,000 55,000 — 2012 Incentive Plan 6,300,000 638,823 532,573 — 2018 Omnibus Incentive Plan 6,000,000 — — 5,875,000 Total 18,400,000 923,823 817,573 5,875,000
Summary of Total Stock-based Compensation Expense Resulting from Stock Options, Restricted Stock, RSUs, Performance RSUs, and Performance Stock	For the twelve months ended December 31, 2018, 2017, and 2016, respectively, the total stock-based compensation expense resulting from stock options, Restricted Stock, RSUs, Performance RSUs, and Performance Stock was recorded to the following line items of our consolidated statements of operations: Year Ended December 31, (In thousands) 2018 2017 2016 Cost of revenue $ 327 $ 304 $ 186 Research and development expenses 469 374 246 Selling, general and administrative expenses 2,522 2,196 1,351 Stock-based compensation expense $ 3,318 $ 2,874 $ 1,783
Weighted Average Assumptions Applied in Determining Fair Value of Options Granted	The following weighted average assumptions were applied in determining the fair value of options granted during the respective periods: Year Ended December 31, 2018 2017 2016 Risk-free interest rate — 2.02 % 1.21 % Expected option life (years) — 5.7 5.3 Expected stock price volatility — 42 % 44 % Expected dividend yield — — — Fair value of options granted $ — $ 2.06 $ 1.51
Summary of All Stock Option Transactions	The following is a summary of all stock option transactions for the three years ended December 31, 2018: Shares Weighted Average Exercise Price Weighted Average Remaining Contractual Term (Yrs) Outstanding at January 1, 2016 1,774,552 $ 3.65 Granted at market price 373,187 $ 3.70 Cancelled or expired (63,700 ) $ 3.95 Exercised (123,760 ) $ 1.66 Outstanding at December 31, 2016 1,960,279 $ 3.78 Granted at market price 30,750 $ 4.96 Cancelled or expired (37,412 ) $ 4.71 Exercised (932,303 ) $ 4.51 Outstanding at December 31, 2017 1,021,314 $ 3.11 Granted at market price — $ 0.00 Cancelled or expired (7,480 ) $ 4.04 Exercised (90,011 ) $ 1.83 Outstanding at December 31, 2018 923,823 $ 3.23 4.76 Options exercisable at December 31, 2018 817,573 $ 3.16 4.43
Summarized Information about Stock Options Outstanding by Range of Exercise Prices	Summarized information about stock options outstanding at December 31, 2018, is as follows: Options Outstanding Options Exercisable Range of Exercise Prices Number Outstanding Weighted Average Remaining Contractual Life Weighted Average Exercise Price Number Exercisable Weighted Average Exercise Price $2.00 - $3.49 431,813 2.90 $ 2.58 431,813 $ 2.58 $3.50 - $4.99 492,010 6.40 $ 3.80 385,760 $ 3.82 923,823 4.76 $ 3.23 817,573 $ 3.16
Summary of All Restricted Stock Activity	The following is a summary of all Restricted Stock activity during the three years ended December 31, 2018: Restricted Shares Weighted Average Fair Value Non-vested restricted stock at January 1, 2016 423,250 $ 3.91 Granted at market price 573,461 $ 3.75 Vested (292,469 ) $ 3.50 Cancelled (15,000 ) $ 4.11 Non-vested restricted stock at December 31, 2016 689,242 $ 3.94 Granted at market price 665,623 $ 5.02 Vested (251,956 ) $ 4.00 Cancelled (20,000 ) $ 4.96 Non-vested restricted stock at December 31, 2017 1,082,909 $ 4.57 Granted at market price 842,546 $ 4.53 Vested (419,452 ) $ 4.44 Cancelled (151,003 ) $ 4.77 Non-vested restricted stock at December 31, 2018 1,355,000 $ 4.71
Summary of All Restricted Stock Unit Activity	The following is a summary of all RSU activity during the three years ended December 31, 2018: Restricted Stock Units Weighted Average Fair Value Non-vested restricted stock units at January 1, 2016 299,500 $ 3.79 Granted at market price 38,500 $ 3.74 Vested (179,914 ) $ 3.66 Cancelled — $ — Non-vested restricted stock units at December 31, 2016 158,086 $ 3.92 Granted at market price 54,500 $ 4.96 Vested (126,167 ) $ 4.07 Cancelled — $ — Non-vested restricted stock units at December 31, 2017 86,419 $ 4.36 Granted at market price 36,500 $ 4.57 Vested (50,751 ) $ 4.18 Cancelled — $ — Non-vested restricted stock units at December 31, 2018 72,168 $ 4.59
Summary of All Performance RSU Activity	The following is a summary of all Performance RSU activity during the three years ended December 31, 2018: Restricted Stock Units Weighted Average Fair Value Non-vested performance RSUs at January 1, 2016 182,500 $ 3.88 Granted at market price 22,500 $ 3.61 Vested (97,428 ) $ 3.88 Forfeited (16,741 ) $ 3.88 Non-vested performance RSUs at December 31, 2016 90,831 $ 3.81 Granted at market price 11,500 $ 4.96 Vested (20,999 ) $ 4.08 Forfeited (41,668 ) $ 3.83 Non-vested performance RSUs at December 31, 2017 39,664 $ 3.98 Granted at market price 5,500 $ 4.04 Vested (32,665 ) $ 3.91 Forfeited — $ 0.00 Non-vested performance RSUs at December 31, 2018 12,499 $ 4.20
Summary of All Performance Stock Activity	The following is a summary of all Performance Stock activity during the three years ended December 31, 2018: Restricted Stock Units Weighted Average Fair Value Non-vested performance stock at January 1, 2016 — — Granted at market price 141,500 $ 3.61 Vested (20,000 ) $ 3.61 Forfeited — — Non-vested performance stock at December 31, 2016 121,500 $ 3.61 Granted at market price 112,112 $ 4.96 Vested — — Forfeited (40,502 ) $ 3.61 Non-vested performance stock at December 31, 2017 193,110 $ 4.39 Granted at market price 153,723 $ 4.04 Vested (77,874 ) $ 4.26 Forfeited (13,333 ) $ 4.50 Non-vested performance stock at December 31, 2018 255,626 $ 4.22

Supplemental Cash Flow Inform_2

Supplemental Cash Flow Information (Tables)	12 Months Ended
	Dec. 31, 2018
Supplemental Cash Flow Elements [Abstract]
Supplemental Cash Flow Information Relating to Interest and Taxes	Supplemental information relating to interest and taxes: Year Ended December 31, (In thousands) 2018 2017 2016 Interest payments $ — $ — $ 33 Income tax payments $ 1,115 $ 636 $ 670

Receivables, Net (Tables)

Receivables, Net (Tables)	12 Months Ended
	Dec. 31, 2018
Receivables [Abstract]
Summary of Net Receivables	(In thousands) December 31, 2018 2017 Gross accounts receivables $ 14,135 $ 9,307 Allowance for returns and doubtful accounts (277 ) (270 ) Unpaid portion of deferred revenue (10,670 ) (7,648 ) Note receivable 458 458 Allowance for note receivable (458 ) (458 ) Receivables, net $ 3,188 $ 1,389

Prepaid and other current ass_2

Prepaid and other current assets (Tables)	12 Months Ended
	Dec. 31, 2018
Deferred Costs Capitalized Prepaid And Other Assets Disclosure [Abstract]
Schedule of Prepaid and Other Current Assets	(In thousands) December 31, 2018 2017 Prepaid insurance, maintenance, software licenses and other $ 2,460 $ 2,386 Deferred commissions — 415 Tax-related 716 421 Prepaid and other current assets $ 3,176 $ 3,222

Property and Equipment (Tables)

Property and Equipment (Tables)	12 Months Ended
	Dec. 31, 2018
Property Plant And Equipment [Abstract]
Summary of Property and Equipment	(In thousands) December 31, 2018 2017 Computer and office equipment and software $ 26,762 $ 25,379 Leasehold improvements 6,834 6,763 Furniture and fixtures 2,181 2,136 35,777 34,278 Less accumulated depreciation (31,853 ) (30,230 ) Property and equipment, net $ 3,924 $ 4,048

Goodwill and Other Intangible_2

Goodwill and Other Intangible Assets (Tables)	12 Months Ended
	Dec. 31, 2018
Goodwill And Intangible Assets Disclosure [Abstract]
Schedule of Changes in Carrying Amount of Goodwill	The changes in the carrying amount of goodwill for the years ended December 31, 2018 and 2017, are as follows: Year Ended December 31, (In thousands) 2018 2017 Opening balance $ 8,469 $ 2,161 Additions 6,215 6,308 Acquisition adjustments (901 ) — Goodwill $ 13,783 $ 8,469
Schedule of Other Intangible Assets	Our other intangible assets consist of the following: December 31, 2018 (In thousands) Gross Carrying Amount Accumulated Amortization Net Carrying Amount Internal use software $ 1,189 $ (162 ) $ 1,027 Internally-developed hosting arrangement 1,520 (77 ) 1,443 Trademarks and other 691 (113 ) 578 Technology 7,604 (2,678 ) 4,926 Customer relationships 7,870 (593 ) 7,277 Intangible assets, net $ 18,874 $ (3,623 ) $ 15,251
Schedule of Amortization of Intangible Assets	For the twelve months ended December 31, 2018, amortization of intangible assets was recorded to the following line items of our consolidated statements of operations: Year Ended December 31, (In thousands) 2018 Cost of revenue $ 368 Research and development expenses 203 Selling, general and administrative expenses 699 Amortization of intangible assets $ 1,270
Summary of Estimated Future Amortization Expense	The following table summarizes our estimated future amortization expense: (In thousands) 2019 2020 2021 2022 2023 Thereafter Total Amortization expense $ 1,670 1,690 $ 1,690 $ 1,481 $ 1,310 $ 7,410 $ 15,251

Accrued Expenses (Tables)

Accrued Expenses (Tables)	12 Months Ended
	Dec. 31, 2018
Payables And Accruals [Abstract]
Summary of Accrued Expenses	December 31, (In thousands) 2018 2017 Employee compensation and benefits $ 5,122 $ 4,452 Professional fees 1,289 356 Taxes 113 154 Other 3,223 1,139 Total accrued expenses $ 9,747 $ 6,101

Fair Value Measurements (Tables

Fair Value Measurements (Tables)	12 Months Ended
	Dec. 31, 2018
Fair Value Disclosures [Abstract]
Schedule of Reconciliation of Contingent Earn-out Liability Measured at Fair Value on Recurring Basis	The following table represents a reconciliation of our acquisition-related contingent earn-out liability measured at fair value on a recurring basis, using Level 3 inputs for the year ended December 31, 2018: (In thousands) Fair Value Measurements Using Significant Unobservable Inputs (Level 3) Balance at December 31, 2017 $ 1,488 Additions during the period — Payments during the period (800 ) Adjustments to fair value during the period recorded in General and Administrative expenses 476 Balance at December 31, 2018 $ 1,164

Earnings Per Share and Potent_2

Earnings Per Share and Potential Dilution (Tables)	12 Months Ended
	Dec. 31, 2018
Earnings Per Share [Abstract]
Computations of Basic and Diluted Earnings Per Share	The computations for basic and diluted earnings per share for the years ended December 31, 2018, 2017, and 2016, are as follows: Year Ended December 31, 2018 2017 2016 Basic weighted average shares 52,591,714 53,430,492 53,819,772 Effect of dilutive securities: Employee and director stock options 347,167 — 317,329 Restricted Stock 409,871 — 149,817 RSUs 24,369 — 63,484 Performance RSUs 9,367 — 24,449 Performance Stock 98,807 — 20,294 Potential dilutive common shares 53,481,295 53,430,492 54,395,145

Commitments and Contingencies (

Commitments and Contingencies (Tables)	12 Months Ended
	Dec. 31, 2018
Commitments And Contingencies Disclosure [Abstract]
Summary of Fixed Contractual Obligations and Commitments	A summary of our fixed contractual obligations and commitments at December 31, 2018, is as follows: (In thousands) 2019 2020 2021 2022 2023 Thereafter Total Operating leases $ 1,625 $ 1,220 $ 1,072 $ 1,089 $ 1,116 $ 861 $ 6,983

Income Taxes (Tables)

Income Taxes (Tables)	12 Months Ended
	Dec. 31, 2018
Income Tax Disclosure [Abstract]
Components of Income Taxes	Components of the income taxes are as follows: (In thousands) 2018 2017 2016 Current: U.S. $ (794 ) $ 183 $ 100 State 725 (196 ) 329 Foreign 71 156 75 Deferred Federal (4,722 ) 18,461 3,185 Foreign — 2 3 Income tax (benefit) expense $ (4,720 ) $ 18,606 $ 3,692
Schedule of Reconciliation of Tax Expense Benefit to Income Taxes Related to Continuing Operations	On December 22, 2017, the U.S. enacted the Tax Cuts and Jobs Act of 2017 (the “Tax Act”) which significantly changed U.S. tax law. The Tax Act, among other things, lowered the federal statutory corporate income tax rate from 34% to 21% effective January 1, 2018. The Company completed its assessment of the impact to 2018 noting no changes from what it disclosed in 2017. The Company’s income tax expense (benefit) for 2018, 2017 and 2016, respectively, reflect tax expense (benefit) based on statutory rates in 2018, 2017, and 2016. A reconciliation of the expected U.S. tax expense (benefit) to income taxes related to continuing operations is as follows: (In thousands) 2018 2017 2016 Expected tax expense at U.S. statutory rate $ 2,260 $ 3,587 $ 3,250 Change in corporate tax rate- deferreds — 12,473 — Increase (decrease) in valuations allowance (7,841 ) — — Increase (decrease) in valuations allowance- other — 2,064 — Nondeductible expense and nontaxable income 111 890 114 State income taxes, net of federal benefits 815 (129 ) 217 Foreign income taxes 68 159 78 Other (133 ) (438 ) 33 Income tax (benefit) expense $ (4,720 ) $ 18,606 $ 3,692
Components of Deferred Income Taxes	Components of our U.S. deferred income taxes as of December 31, 2018 and 2017 are as follows: (In thousands) 2018 2017 Deferred tax assets: Nondeductible $ 113 $ 112 U.S. net operating loss carryforwards 46,826 48,769 State net operating loss carryforwards 71 321 Tax credit carryforwards 5,703 6,450 Stock-based compensation 976 750 Depreciable assets 822 851 Other assets 938 1,039 Total deferred tax assets 55,449 58,292 Deferred tax liabilities: Intangible assets (3,428 ) (1,342 ) Prepaid expenses (572 ) (532 ) Total deferred tax assets 51,449 56,418 Less valuation allowance (22,667 ) (30,773 ) Net deferred tax assets $ 28,782 $ 25,645

Acquisitions (Tables)

Acquisitions (Tables)	12 Months Ended
	Dec. 31, 2018
Unaudited Pro Forma Financial Information	The following unaudited pro forma financial information presents the combined results of operations for the twelve month periods ending December 31, 2018, and 2017, respectively, as though the Erado, EMS and Greenview acquisitions that occurred during the reporting period had occurred as of the beginning of the earliest period presented, with adjustments to give effect to pro forma events that are directly attributable to the acquisition, such as amortization expense of intangible assets and acquisition-related transaction costs. 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 acquisition had occurred at the beginning of the earliest period presented, nor are they indicative of future results of operations: Twelve Months Ended December 31, (In thousands, except per share data) 2018 2017 Revenues $ 71,762 $ 69,587 Net income (loss) 18,330 (6,981 ) Basic income (loss) per common share $ 0.35 $ (0.13 ) Diluted income (loss) per common share $ 0.34 $ (0.13 )
Greenview Data, 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: Current assets $ 334 Property and equipment 249 Trademark/names 170 Technology 1,990 Customer relationships 2,880 Goodwill 4,343 Total assets 9,966 Liabilities: Deferred revenue $ 537 Other current liabilities 124 Deferred tax liability 1,609 Total liabilities 2,270 Net assets recorded $ 7,696
Entelligence Messaging Server [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: Trademark/names $ 140 Technology 550 Customer relationships 230 Goodwill 1,063 Total assets 1,983 Liabilities: Deferred revenue $ 333 Total liabilities 333 Net assets recorded $ 1,650
Erado [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 $ 848 Property and equipment 169 Trademark/names 260 Technology 3,030 Customer relationships 4,760 Goodwill 6,215 Total assets 15,282 Liabilities: Deferred revenue $ 809 Other current liabilities 93 Total liabilities 902 Net assets recorded $ 14,380

Quarterly Results of Operatio_2

Quarterly Results of Operations (Unaudited) (Tables)	12 Months Ended
	Dec. 31, 2018
Quarterly Financial Information Disclosure [Abstract]
Summary of Quarterly Results of Operations	The following is a summary of the quarterly results of operations for the years ended December 31, 2018 and 2017: Quarter Ended (In thousands except per share data) March 31 June 30 September 30 December 31 2018 Revenues $ 16,654 $ 17,500 $ 17,876 $ 18,448 Gross margin 13,140 13,694 14,006 14,451 Net income (loss) 1,892 1,840 2,455 9,240 Basic net income (loss) per common share* 0.04 0.04 0.05 0.18 Diluted net income (loss) per common share* 0.04 0.03 0.05 0.17 Comprehensive Income — — — 9,224 2017 Revenues $ 15,893 $ 16,378 $ 16,592 $ 16,800 Gross margin 13,070 13,131 13,320 13,540 Net income (loss) 1,775 1,139 1,905 (12,877 ) Basic net income (loss) per common share* 0.03 0.02 0.04 (0.24 ) Diluted net income (loss) per common share* 0.03 0.02 0.03 (0.24 ) Comprehensive Income — — — — * Net income (loss) per share is calculated independently for each quarter. The sum of Net income (loss) per share for each quarter may not equal the total Net income (loss) per share for the year due to rounding differences.

Summary of Significant Accoun_4

Summary of Significant Accounting Policies - Additional Information (Detail) - USD ($)	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016	Jan. 01, 2018	Mar. 15, 2017
Schedule Of Significant Accounting Policies [Line Items]
Cash investments maturities	3 months
Depreciation expense	$ 2,400,000	$ 2,400,000	$ 2,300,000
Goodwill	$ 13,783,000	$ 8,469,000	2,161,000
Goodwill to total asset	13.00%	10.00%
Impairment	$ 0	$ 0	0
Accumulated deferred tax assets	22,667,000	30,773,000
Total deferred tax asset not subject to a valuation allowance	28,782,000	25,645,000
Temporary timing differences between U.S. GAAP and tax-related expense	(1,200,000)
Income tax credits	5,703,000	$ 6,450,000
Alternative Minimum Tax credits	$ 678,000
Percentage of revenue generated from email protection services	100.00%	100.00%
Research and development expenses	$ 11,323,000	$ 10,980,000	9,553,000
Advertising expense	$ 1,300,000	1,500,000	$ 1,900,000
Revenue from contract with customer, description	Our Company elected to use a portfolio approach, applying 8 year, 4 year, and 18 month amortization periods for our new, add-on, and renewal sales commission expenses, respectively. Determination of the amortization period and the subsequent assessments for impairment of the related deferred cost asset requires significant judgement.
Retained earnings	$ (216,364,000)	(236,372,000)
Deferred tax assets	28,785,000	$ 25,647,000
Contingent consideration liability, financing activities	605,000
Contingent consideration liability, operating activities	195,000
Greenview Data, Inc [Member]
Schedule Of Significant Accounting Policies [Line Items]
Goodwill					$ 4,343,000
Contingent consideration liability, earn-out payment	800,000
Contingent consideration liability, financing activities	605,000
Contingent consideration liability, operating activities	195,000
ASC 606 [Member]
Schedule Of Significant Accounting Policies [Line Items]
Retained earnings				$ (231,808,000)
Deferred tax assets				24,031,000
ASC 606 [Member] | Cumulative Effect Adjustment [Member]
Schedule Of Significant Accounting Policies [Line Items]
Retained earnings	6,582,000			4,564,000
Deferred tax assets	(1,616,000)			$ (1,616,000)
ASU 2016-02
Schedule Of Significant Accounting Policies [Line Items]
Right-to-use-assets	4,500,000
Lease liabilities	$ 6,500,000
Email Encryption [Member]
Schedule Of Significant Accounting Policies [Line Items]
Percentage of revenue generated from email protection services	88.00%
Minimum [Member]
Schedule Of Significant Accounting Policies [Line Items]
Software subscription term	1 year
Maximum [Member]
Schedule Of Significant Accounting Policies [Line Items]
Software subscription term	5 years
Customer Concentration Risk [Member] | Sales Revenue Net [Member]
Schedule Of Significant Accounting Policies [Line Items]
Revenue in percentage	38.00%
Federal [Member]
Schedule Of Significant Accounting Policies [Line Items]
Federal net operating loss carryforwards	$ 27,000,000
State [Member]
Schedule Of Significant Accounting Policies [Line Items]
Income tax credits	2,100,000
Foreign [Member]
Schedule Of Significant Accounting Policies [Line Items]
Income tax credits	114,000
Cost of Revenue [Member]
Schedule Of Significant Accounting Policies [Line Items]
Depreciation expense	1,700,000
Research and Development Expense [Member]
Schedule Of Significant Accounting Policies [Line Items]
Depreciation expense	426,000
Selling, Marketing, and General and Administrative Expenses [Member]
Schedule Of Significant Accounting Policies [Line Items]
Depreciation expense	$ 314,000
New Sales Commission Expenses [Member]
Schedule Of Significant Accounting Policies [Line Items]
Amortization period	8 years
Add-on Sales Commission Expenses [Member]
Schedule Of Significant Accounting Policies [Line Items]
Amortization period	4 years
Renewal Sales Commission Expenses [Member]
Schedule Of Significant Accounting Policies [Line Items]
Amortization period	18 months
Computer [Member]
Schedule Of Significant Accounting Policies [Line Items]
Estimated useful lives of depreciated or amortized Property and equipment	3 years
Office Equipment [Member]
Schedule Of Significant Accounting Policies [Line Items]
Estimated useful lives of depreciated or amortized Property and equipment	3 years
Software [Member]
Schedule Of Significant Accounting Policies [Line Items]
Estimated useful lives of depreciated or amortized Property and equipment	3 years
Research and development expenses	$ 1,500,000
Leasehold Improvements [Member]
Schedule Of Significant Accounting Policies [Line Items]
Estimated useful lives of depreciated or amortized Property and equipment	5 years
Furniture and Fixtures [Member]
Schedule Of Significant Accounting Policies [Line Items]
Estimated useful lives of depreciated or amortized Property and equipment	5 years

Summary of Significant Accoun_5

Summary of Significant Accounting Policies - Cumulative Effect of Changes in Condensed Consolidated Balance Sheet Due to Adoption of ASC 606 (Detail) - USD ($) $ in Thousands	Dec. 31, 2018	Jan. 01, 2018	Dec. 31, 2017
ASSETS
Prepaid and other current assets	$ 3,176		$ 3,222
Other assets and deferred costs	9,424
Deferred tax assets	28,785		25,647
Stockholders’ equity:
Accumulated deficit	(216,364)		$ (236,372)
ASC 606 [Member]
ASSETS
Prepaid and other current assets		$ 2,807
Other assets and deferred costs	9,300	6,595
Deferred tax assets		24,031
Stockholders’ equity:
Accumulated deficit		(231,808)
ASC 606 [Member] | Cumulative Effect Adjustment [Member]
ASSETS
Prepaid and other current assets	(584)	(415)
Other assets and deferred costs	9,424	6,595
Deferred tax assets	(1,616)	(1,616)
Stockholders’ equity:
Accumulated deficit	$ 6,582	$ 4,564

Summary of Significant Accoun_6

Summary of Significant Accounting Policies - Summary of Statements of Income Reported under New Revenue Standard Compared to Previous Standard (Detail) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Disaggregation Of Revenue [Line Items]
Revenues	$ 18,448	$ 17,876	$ 17,500	$ 16,654	$ 16,800	$ 16,592	$ 16,378	$ 15,893	$ 70,478	$ 65,663	$ 60,144
Cost of revenues									15,186	12,602	10,533
Gross margin	14,451	14,006	13,694	13,140	13,540	13,320	13,131	13,070	55,292	53,061	49,611
Operating expenses:
Research and development									11,323	10,980	9,553
Selling, general and administrative									33,999	31,871	30,742
Total operating expenses									45,322
Operating income									9,970	10,210	9,316
Other income, net									754	339	213
Income before income taxes									10,724	10,549	9,529
Income tax benefit (expense)									4,720	(18,606)	(3,692)
Net income (loss)	$ 9,240	$ 2,455	$ 1,840	$ 1,892	$ (12,877)	$ 1,905	$ 1,139	$ 1,775	$ 15,444	$ (8,057)	$ 5,837
Basic income (loss) per common share	$ 0.18	$ 0.05	$ 0.04	$ 0.04	$ (0.24)	$ 0.04	$ 0.02	$ 0.03	$ 0.29	$ (0.15)	$ 0.11
Diluted income (loss) per common share	$ 0.17	$ 0.05	$ 0.03	$ 0.04	$ (0.24)	$ 0.03	$ 0.02	$ 0.03	$ 0.29	$ (0.15)	$ 0.11
ASC 606 [Member] | Under ASC 605 [Member]
Disaggregation Of Revenue [Line Items]
Revenues									$ 70,478
Cost of revenues									15,186
Gross margin									55,292
Operating expenses:
Research and development									11,323
Selling, general and administrative									36,554
Total operating expenses									47,877
Operating income									7,415
Other income, net									754
Income before income taxes									8,169
Income tax benefit (expense)									5,257
Net income (loss)									$ 13,426
Basic income (loss) per common share									$ 0.26
Diluted income (loss) per common share									$ 0.25
ASC 606 [Member] | Variance [Member]
Operating expenses:
Selling, general and administrative									$ (2,555)
Total operating expenses									(2,555)
Operating income									2,555
Income before income taxes									2,555
Income tax benefit (expense)									(537)
Net income (loss)									$ 2,018
Basic income (loss) per common share									$ 0.04
Diluted income (loss) per common share									$ 0.04

Summary of Significant Accoun_7

Summary of Significant Accounting Policies - Summary of Balance Sheet Reported under New Revenue Standard Compared to Previous Standard (Detail) - USD ($) $ in Thousands	Dec. 31, 2018	Jan. 01, 2018	Dec. 31, 2017
ASSETS
Prepaid and other current assets	$ 3,176		$ 3,222
Other assets and deferred costs	9,424
Deferred tax assets	28,785		25,647
Stockholders’ equity:
Accumulated deficit	(216,364)		$ (236,372)
ASC 606 [Member]
ASSETS
Prepaid and other current assets		$ 2,807
Other assets and deferred costs	9,300	6,595
Deferred tax assets		24,031
Stockholders’ equity:
Accumulated deficit		(231,808)
ASC 606 [Member] | Under ASC 605 [Member]
ASSETS
Prepaid and other current assets	3,760
Deferred tax assets	30,401
Stockholders’ equity:
Accumulated deficit	(222,946)
ASC 606 [Member] | Variance [Member]
ASSETS
Prepaid and other current assets	(584)	(415)
Other assets and deferred costs	9,424	6,595
Deferred tax assets	(1,616)	(1,616)
Stockholders’ equity:
Accumulated deficit	$ 6,582	$ 4,564

Stock Options and Stock-Based_3

Stock Options and Stock-Based Employee Compensation - Summary of Common Stock Options Outstanding (Detail) - shares	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015	Apr. 13, 2012
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Authorized Shares	18,400,000
Options Outstanding	923,823	1,021,314	1,960,279	1,774,552
Options Vested	817,573
Available for Grant	5,875,000
2004 Stock Option Plan [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Authorized Shares	5,000,000
Options Outstanding	230,000
Options Vested	230,000
Available for Grant	0
2006 Director's Stock Option Plan [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Authorized Shares	1,100,000
Options Outstanding	55,000
Options Vested	55,000
Available for Grant	0
2018 Omnibus Incentive Plan [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Authorized Shares	6,000,000				2,700,000
Options Outstanding	0
Options Vested	0
Available for Grant	5,875,000
2012 Incentive Plan [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Authorized Shares	6,300,000
Options Outstanding	638,823
Options Vested	532,573
Available for Grant	0

Stock Options and Stock-Based_4

Stock Options and Stock-Based Employee Compensation - Additional Information (Detail) - USD ($) $ in Thousands	Jun. 24, 2015	Apr. 13, 2012	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Expiry of option			10 years
Vesting period of options			3 years
Shares available for issuance			18,400,000
Total unrecognized stock-based compensation related to non-vested stock-based compensation awards			$ 5,200
The number of years over which cost is expected to be recognized			1 year 6 months
Deferred tax assets, tax deferred expense compensation and benefits employee compensation			$ 673	$ 824	$ 506
Options granted during period			0	30,750	373,187
Options outstanding			923,823	1,021,314	1,960,279	1,774,552
Options, options exercisable			817,573
Number Exercisable			817,573	832,376	1,685,732
Stock Options [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Aggregate intrinsic value of options exercised			$ 334	$ 914
Employee and Director Stock Options [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Options outstanding			923,823	983,564
Options, options exercisable			817,573	802,314
Aggregate intrinsic value of options outstanding			$ 2,300	$ 1,300
Aggregate intrinsic value of options exercisable			$ 2,100	1,200
CFO [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Stock-based compensation expense related to accelerated vesting of awards					$ 280
Executive Departures [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Stock-based compensation expense related to accelerated vesting of awards				$ 292
2018 Omnibus Incentive Plan [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Vesting period of options		4 years	4 years
Shares available for issuance		2,700,000	6,000,000
Additional shares underlying options outstanding	3,600,000	1,327,000
Options outstanding			0

Stock Options and Stock-Based_5

Stock Options and Stock-Based Employee Compensation - Summary of Total Stock-based Compensation Expense Resulting from Stock Options, Restricted Stock, RSUs, Performance RSUs, and Performance Stock (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]
Stock-based compensation expense	$ 3,318	$ 2,874	$ 1,783
Cost of Revenue [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]
Stock-based compensation expense	327	304	186
Research and Development Expenses [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]
Stock-based compensation expense	469	374	246
Selling, General and Administrative Expenses [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]
Stock-based compensation expense	$ 2,522	$ 2,196	$ 1,351

Stock Options and Stock-Based_6

Stock Options and Stock-Based Employee Compensation - Weighted Average Assumptions Applied in Determining Fair Value of Options Granted (Detail) - $ / shares	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]
Risk-free interest rate	0.00%	2.02%	1.21%
Expected option life (years)	0 years	5 years 8 months 12 days	5 years 3 months 18 days
Expected stock price volatility	0.00%	42.00%	44.00%
Expected dividend yield	0.00%	0.00%	0.00%
Fair value of options granted	$ 0	$ 2.06	$ 1.51

Stock Options and Stock-Based_7

Stock Options and Stock-Based Employee Compensation - Summary of All Stock Option Transactions (Detail) - $ / shares	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Share Based Compensation Arrangement By Share Based Payment Award Options Outstanding Roll Forward
Shares, Outstanding, Beginning Balance	1,021,314	1,960,279	1,774,552
Shares, Granted at market price	0	30,750	373,187
Shares, Cancelled or expired	(7,480)	(37,412)	(63,700)
Shares, Exercised	(90,011)	(932,303)	(123,760)
Shares, Outstanding Ending Balance	923,823	1,021,314	1,960,279
Shares, Options Exercisable	817,573
Weighted Average Exercise Price, Outstanding, Beginning Balance	$ 3.11	$ 3.78	$ 3.65
Weighted Average Exercise Price, Granted at market price	0	4.96	3.70
Weighted Average Exercise Price, Cancelled or expired	4.04	4.71	3.95
Weighted Average Exercise Price, Exercised	1.83	4.51	1.66
Weighted Average Exercise Price, Outstanding, Ending Balance	3.23	$ 3.11	$ 3.78
Weighted Average Exercise Price, Options Exercisable	$ 3.16
Weighted Average Remaining Contractual Term, Outstanding	4 years 9 months 3 days
Weighted Average Remaining Contractual Term, Options exercisable	4 years 5 months 4 days

Stock Options and Stock-Based_8

Stock Options and Stock-Based Employee Compensation - Summarized Information about Stock Options Outstanding by Range of Exercise Prices (Detail) - $ / shares	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Schedule Of Stock Options [Line Items]
Number Outstanding	923,823	1,021,314	1,960,279	1,774,552
Weighted Average Remaining Contractual Life, Options Outstanding	4 years 9 months 3 days
Weighted Average Exercise Price, Options Outstanding	$ 3.23
Number Exercisable	817,573	832,376	1,685,732
Weighted Average Exercise Price, Options Exercisable	$ 3.16
$2.00 - $3.49 [Member]
Schedule Of Stock Options [Line Items]
Range of Exercise Prices, Lower range	2
Range of Exercise Prices, Upper range	$ 3.49
Number Outstanding	431,813
Weighted Average Remaining Contractual Life, Options Outstanding	2 years 10 months 24 days
Weighted Average Exercise Price, Options Outstanding	$ 2.58
Number Exercisable	431,813
Weighted Average Exercise Price, Options Exercisable	$ 2.58
$3.50 - $4.99 [Member]
Schedule Of Stock Options [Line Items]
Range of Exercise Prices, Lower range	3.50
Range of Exercise Prices, Upper range	$ 4.99
Number Outstanding	492,010
Weighted Average Remaining Contractual Life, Options Outstanding	6 years 4 months 24 days
Weighted Average Exercise Price, Options Outstanding	$ 3.80
Number Exercisable	385,760
Weighted Average Exercise Price, Options Exercisable	$ 3.82

Stock Options and Stock-Based_9

Stock Options and Stock-Based Employee Compensation - Summary of All Restricted Stock Activity (Detail) - Restricted Stock [Member] - $ / shares	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Shares, Non-vested, Beginning balance	1,082,909	689,242	423,250
Shares, Granted at market price	842,546	665,623	573,461
Shares, Vested	(419,452)	(251,956)	(292,469)
Shares, Cancelled	(151,003)	(20,000)	(15,000)
Shares, Non-vested, Ending balance	1,355,000	1,082,909	689,242
Weighted Average Fair Value, Non-vested, Beginning balance	$ 4.57	$ 3.94	$ 3.91
Weighted Average Fair Value, Granted at market price	4.53	5.02	3.75
Weighted Average Fair Value, Vested	4.44	4	3.50
Weighted Average Fair Value, Cancelled	4.77	4.96	4.11
Weighted Average Fair Value, Non-vested, Ending balance	$ 4.71	$ 4.57	$ 3.94

Stock Options and Stock-Base_10

Stock Options and Stock-Based Employee Compensation - Summary of All Restricted Stock Unit Activity (Detail) - Restricted Stock Units (RSUs) [Member] - $ / shares	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Shares, Non-vested, Beginning balance	86,419	158,086	299,500
Shares, Granted at market price	36,500	54,500	38,500
Shares, Vested	(50,751)	(126,167)	(179,914)
Shares, Cancelled	0	0	0
Shares, Non-vested, Ending balance	72,168	86,419	158,086
Weighted Average Fair Value, Non-vested, Beginning balance	$ 4.36	$ 3.92	$ 3.79
Weighted Average Fair Value, Granted at market price	4.57	4.96	3.74
Weighted Average Fair Value, Vested	4.18	4.07	3.66
Weighted Average Fair Value, Cancelled	0	0	0
Weighted Average Fair Value, Non-vested, Ending balance	$ 4.59	$ 4.36	$ 3.92

Stock Options and Stock-Base_11

Stock Options and Stock-Based Employee Compensation - Summary of All Performance RSU Activity (Detail) - Non-vested Performance RSUs [Member] - $ / shares	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Shares, Non-vested, Beginning balance	39,664	90,831	182,500
Shares, Granted at market price	5,500	11,500	22,500
Shares, Vested	(32,665)	(20,999)	(97,428)
Shares, Cancelled	0	(41,668)	(16,741)
Shares, Non-vested, Ending balance	12,499	39,664	90,831
Weighted Average Fair Value, Non-vested, Beginning balance	$ 3.98	$ 3.81	$ 3.88
Weighted Average Fair Value, Granted at market price	4.04	4.96	3.61
Weighted Average Fair Value, Vested	3.91	4.08	3.88
Weighted Average Fair Value, Cancelled	0	3.83	3.88
Weighted Average Fair Value, Non-vested, Ending balance	$ 4.20	$ 3.98	$ 3.81

Stock Options and Stock-Base_12

Stock Options and Stock-Based Employee Compensation - Summary of All Performance Stock Activity (Details) - Performance Stock [Member] - $ / shares	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Shares, Non-vested, Beginning balance	193,110	121,500	0
Shares, Granted at market price	153,723	112,112	141,500
Shares, Vested	(77,874)	0	(20,000)
Shares, Cancelled	(13,333)	(40,502)	0
Shares, Non-vested, Ending balance	255,626	193,110	121,500
Weighted Average Fair Value, Non-vested, Beginning balance	$ 4.39	$ 3.61	$ 0
Weighted Average Fair Value, Granted at market price	4.04	4.96	3.61
Weighted Average Fair Value, Vested	4.26	0	3.61
Weighted Average Fair Value, Cancelled	4.50	3.61	0
Weighted Average Fair Value, Non-vested, Ending balance	$ 4.22	$ 4.39	$ 3.61

Supplemental Cash Flow Inform_3

Supplemental Cash Flow Information - Supplemental Cash Flow Information Relating to Interest and Taxes (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Supplemental Cash Flow Elements [Abstract]
Interest payments			$ 33
Income tax payments	$ 1,115	$ 636	$ 670

Receivables, Net - Summary of N

Receivables, Net - Summary of Net Receivables (Detail) - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017
Accounts Notes And Loans Receivable Net Current [Abstract]
Gross accounts receivables	$ 14,135	$ 9,307
Allowance for returns and doubtful accounts	(277)	(270)
Unpaid portion of deferred revenue	(10,670)	(7,648)
Note receivable	458	458
Allowance for note receivable	(458)	(458)
Receivables, net	$ 3,188	$ 1,389

Receivables, Net - Additional I

Receivables, Net - Additional Information (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017
Receivables [Abstract]
Percentage of doubtful debts on accounts receivable	2.50%
Note receivable on a product line	$ 540	$ 540
Date of note receivable, reserved	Dec. 31, 2018	Dec. 31, 2017

Prepaid and Other Current Ass_3

Prepaid and Other Current Assets - Schedule of Prepaid and Other Current Assets (Detail) - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017
Prepaid Expense And Other Assets Current [Abstract]
Prepaid insurance, maintenance, software licenses and other	$ 2,460	$ 2,386
Deferred commissions		415
Tax-related	716	421
Prepaid and other current assets	$ 3,176	$ 3,222

Property and Equipment - Summar

Property and Equipment - Summary of Property and Equipment (Detail) - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017
Property, Plant and Equipment [Line Items]
Property and equipment gross	$ 35,777	$ 34,278
Less accumulated depreciation	(31,853)	(30,230)
Property and equipment, net	3,924	4,048
Computer and Office Equipment and Software [Member]
Property, Plant and Equipment [Line Items]
Property and equipment gross	26,762	25,379
Leasehold Improvements [Member]
Property, Plant and Equipment [Line Items]
Property and equipment gross	6,834	6,763
Furniture and Fixtures [Member]
Property, Plant and Equipment [Line Items]
Property and equipment gross	$ 2,181	$ 2,136

Property and Equipment - Additi

Property and Equipment - Additional information (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Property Plant And Equipment [Abstract]
Depreciation expense	$ 2.4	$ 2.4	$ 2.3

Other Assets and Deferred Cos_2

Other Assets and Deferred Costs - Additional Information (Detail) - USD ($) $ in Thousands	Dec. 31, 2018	Jan. 01, 2018
Other Assets And Deferred Costs [Line Items]
Other assets and deferred costs	$ 9,424
ASC 606 [Member]
Other Assets And Deferred Costs [Line Items]
Other assets and deferred costs	$ 9,300	$ 6,595

Goodwill and Other Intangible_3

Goodwill and Other Intangible Assets - Schedule of Changes in Carrying Amount of Goodwill (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017
Goodwill Roll Forward
Opening balance	$ 8,469	$ 2,161
Additions	6,215	6,308
Acquisition adjustments	(901)
Goodwill	$ 13,783	$ 8,469

Goodwill and Other Intangible_4

Goodwill and Other Intangible Assets - Additional Information (Detail)	12 Months Ended
	Dec. 31, 2018USD ($)
Goodwill And Intangible Assets Disclosure [Abstract]
Goodwill impairment	$ 0

Goodwill and Other Intangible_5

Goodwill and Other Intangible Assets - Schedule of Other Intangible Assets (Detail) $ in Thousands	Dec. 31, 2018USD ($)
Finite Lived Intangible Assets [Line Items]
Gross Carrying Amount	$ 18,874
Accumulated Amortization	(3,623)
Net Carrying Amount	15,251
Internal Use Software [Member]
Finite Lived Intangible Assets [Line Items]
Gross Carrying Amount	1,189
Accumulated Amortization	(162)
Net Carrying Amount	1,027
Internally-Developed Hosting Arrangement [Member]
Finite Lived Intangible Assets [Line Items]
Gross Carrying Amount	1,520
Accumulated Amortization	(77)
Net Carrying Amount	1,443
Trademarks and Other [Member]
Finite Lived Intangible Assets [Line Items]
Gross Carrying Amount	691
Accumulated Amortization	(113)
Net Carrying Amount	578
Technology [Member]
Finite Lived Intangible Assets [Line Items]
Gross Carrying Amount	7,604
Accumulated Amortization	(2,678)
Net Carrying Amount	4,926
Customer Relationships [Member]
Finite Lived Intangible Assets [Line Items]
Gross Carrying Amount	7,870
Accumulated Amortization	(593)
Net Carrying Amount	$ 7,277

Goodwill and Other Intangible_6

Goodwill and Other Intangible Assets - Schedule of Amortization of Intangible Assets (Detail) $ in Thousands	12 Months Ended
	Dec. 31, 2018USD ($)
Finite Lived Intangible Assets [Line Items]
Amortization of intangible assets	$ 1,270
Cost of Revenue [Member]
Finite Lived Intangible Assets [Line Items]
Amortization of intangible assets	368
Research and Development Expense [Member]
Finite Lived Intangible Assets [Line Items]
Amortization of intangible assets	203
Selling, General and Administrative Expenses [Member]
Finite Lived Intangible Assets [Line Items]
Amortization of intangible assets	$ 699

Goodwill and Other Intangible_7

Goodwill and Other Intangible Assets - Summary of Estimated Future Amortization Expense (Detail) $ in Thousands	Dec. 31, 2018USD ($)
Goodwill And Intangible Assets Disclosure [Abstract]
2,019	$ 1,670
2,020	1,690
2,021	1,690
2,022	1,481
2,023	1,310
Thereafter	7,410
Net Carrying Amount	$ 15,251

Accrued Expenses - Summary of A

Accrued Expenses - Summary of Accrued Expenses (Detail) - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017
Accounts Payable And Accrued Liabilities Current [Abstract]
Employee compensation and benefits	$ 5,122	$ 4,452
Professional fees	1,289	356
Taxes	113	154
Other	3,223	1,139
Total accrued expenses	$ 9,747	$ 6,101

Revenue from Contracts with C_2

Revenue from Contracts with Customers - Additional Information (Detail)	3 Months Ended								12 Months Ended
	Dec. 31, 2018USD ($)	Sep. 30, 2018USD ($)	Jun. 30, 2018USD ($)	Mar. 31, 2018USD ($)	Dec. 31, 2017USD ($)	Sep. 30, 2017USD ($)	Jun. 30, 2017USD ($)	Mar. 31, 2017USD ($)	Dec. 31, 2018USD ($)Segment	Dec. 31, 2017USD ($)	Dec. 31, 2016USD ($)
Disaggregation Of Revenue [Line Items]
Number of operating segment | Segment									1
Percentage of revenue generated from email protection services									100.00%	100.00%
Cumulative effect adjustment establishing on noncurrent deferred contract asset									$ 6,600,000
Current deferred commission asset	$ 415,000								415,000
Increased noncurrent deferred contract asset									4,900,000
Amortization of deferred cost									2,200,000
Impairment losses recognized on deferred contract cost assets									0
Increase to net deferred revenue									2,700,000
Revenue remaining service performance obligations	73,000,000								73,000,000
Revenue recognized performance obligation									45,100,000
Revenues	$ 18,448,000	$ 17,876,000	$ 17,500,000	$ 16,654,000	$ 16,800,000	$ 16,592,000	$ 16,378,000	$ 15,893,000	$ 70,478,000	$ 65,663,000	$ 60,144,000
Healthcare [Member]
Disaggregation Of Revenue [Line Items]
Revenue in precentage									49.00%
Financial Services [Member]
Disaggregation Of Revenue [Line Items]
Revenue in precentage									29.00%
Government Sector [Member]
Disaggregation Of Revenue [Line Items]
Revenue in precentage									7.00%
Other [Member]
Disaggregation Of Revenue [Line Items]
Revenue in precentage									15.00%
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	Dec. 31, 2018USD ($)
Disaggregation Of Revenue [Line Items]
Revenue remaining service performance obligations	$ 73
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date: 2019-01-01
Disaggregation Of Revenue [Line Items]
Revenue, remaining performance obligation expected timing of satisfaction period	1 year
Revenue remaining service performance obligations	$ 47.3
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date: 2020-01-01
Disaggregation Of Revenue [Line Items]
Revenue, remaining performance obligation expected timing of satisfaction period
Revenue remaining service performance obligations	$ 25.7

Fair Value Measures - Schedule

Fair Value Measures - Schedule of Reconciliation of Contingent Earn-out Liability Measured at Fair Value on Recurring Basis (Detail) - Level 3 [Member] $ in Thousands	12 Months Ended
	Dec. 31, 2018USD ($)
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Balance at December 31, 2017	$ 1,488
Payments during the period	(800)
Adjustments to fair value during the period recorded in General and Administrative expenses	476
Balance at December 31, 2018	$ 1,164

Earnings Per Share and Potent_3

Earnings Per Share and Potential Dilution - Computations of Basic and Diluted Earnings Per Share (Detail) - shares	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Weighted Average Number of Shares [Line Items]
Basic weighted average shares	52,591,714	53,430,492	53,819,772
Potential dilutive common shares	53,481,295	53,430,492	54,395,145
Employee and Director Stock Options [Member]
Weighted Average Number of Shares [Line Items]
Effect of dilutive securities	347,167		317,329
Restricted Stock [Member]
Weighted Average Number of Shares [Line Items]
Effect of dilutive securities	409,871		149,817
RSUs [Member]
Weighted Average Number of Shares [Line Items]
Effect of dilutive securities	24,369		63,484
Performance RSUs [Member]
Weighted Average Number of Shares [Line Items]
Effect of dilutive securities	9,367		24,449
Performance Stock [Member]
Weighted Average Number of Shares [Line Items]
Effect of dilutive securities	98,807		20,294

Earnings Per Share and Potent_4

Earnings Per Share and Potential Dilution - Additional Information (Detail) - shares	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2016
Employee and Director Stock Options [Member]
Weighted Average Number of Shares [Line Items]
Antidilutive securities excluded from computation of earnings per share amount	73,313	1,079,474
Restricted Stock [Member]
Weighted Average Number of Shares [Line Items]
Antidilutive securities excluded from computation of earnings per share amount	131,774	109,293
RSUs [Member]
Weighted Average Number of Shares [Line Items]
Antidilutive securities excluded from computation of earnings per share amount	6,084	20,600
Performance RSUs [Member]
Weighted Average Number of Shares [Line Items]
Antidilutive securities excluded from computation of earnings per share amount	917	886
Performance Stock [Member]
Weighted Average Number of Shares [Line Items]
Antidilutive securities excluded from computation of earnings per share amount	18,536	5,572

Significant Customers - Additio

Significant Customers - Additional Information (Detail) - Customer	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Related Party Transactions [Abstract]
Customer accounted for revenue	0	0	0

Commitments and Contingencies -

Commitments and Contingencies - Additional Information (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Commitments And Contingencies Disclosure [Abstract]
Rental expense on operating lease	$ 1.6	$ 1.4	$ 1.4
Operating leases, expiration year	2,024

Commitments and Contingencies_2

Commitments and Contingencies - Summary of Fixed Contractual Obligations and Commitments (Detail) $ in Thousands	Dec. 31, 2018USD ($)
Operating Leases Future Minimum Payments Due [Abstract]
2,019	$ 1,625
2,020	1,220
2,021	1,072
2,022	1,089
2,023	1,116
Thereafter	861
Total	$ 6,983

Other Comprehensive Loss - Addi

Other Comprehensive Loss - Additional Information (Detail) $ in Thousands	12 Months Ended
	Dec. 31, 2018USD ($)
Accumulated Other Comprehensive Income Loss [Line Items]
Foreign currency translation loss, net of tax	$ 16
Canada [Member]
Accumulated Other Comprehensive Income Loss [Line Items]
Foreign currency translation loss, net of tax	16
Foreign currency translation loss, tax amount	$ 26

Income Taxes - Components of In

Income Taxes - Components of Income Taxes (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Current:
U.S.	$ (794)	$ 183	$ 100
State	725	(196)	329
Foreign	71	156	75
Deferred
Federal	(4,722)	18,461	3,185
Foreign		2	3
Income tax (benefit) expense	$ (4,720)	$ 18,606	$ 3,692

Income Taxes - Additional Infor

Income Taxes - Additional Information (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017
Income Taxes [Line Items]
Federal statutory corporate income tax rate	21.00%	34.00%
Reversed in valuation allowance	$ 7,841
Operating loss carryforwards	$ 46,826	$ 48,769
Unrecognized tax benefits to significantly increase or decrease	12 months
Statute of limitations by major tax jurisdictions	3 years
Internal Revenue Service (IRS) [Member]
Income Taxes [Line Items]
Operating loss carryforwards	$ 223,000
U.S. net operating loss carryforwards expire	2,021
State [Member]
Income Taxes [Line Items]
State tax credit carryforwards	$ 2,000
Operating loss carryforwards, expiration dates	2,027
General Business Tax Credit Carry Forward [Member]
Income Taxes [Line Items]
State tax credit carryforwards	$ 3,700
Tax credit carry forward began to expiration	2,018
Tax credit carry forward refunded through	2,021

Income Taxes - Schedule of Reco

Income Taxes - Schedule of Reconciliation of Tax Expense Benefit to Income Taxes Related to Continuing Operations (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Income Tax Disclosure [Abstract]
Expected tax expense at U.S. statutory rate	$ 2,260	$ 3,587	$ 3,250
Change in corporate tax rate- deferreds		12,473
Increase (decrease) in valuations allowance	(7,841)
Increase (decrease) in valuations allowance- other		2,064
Nondeductible expense and nontaxable income	111	890	114
State income taxes, net of federal benefits	815	(129)	217
Foreign income taxes	68	159	78
Other	(133)	(438)	33
Income tax (benefit) expense	$ (4,720)	$ 18,606	$ 3,692

Income Taxes - Components of De

Income Taxes - Components of Deferred Income Taxes (Detail) - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017
Deferred tax assets:
Nondeductible	$ 113	$ 112
U.S. net operating loss carryforwards	46,826	48,769
State net operating loss carryforwards	71	321
Tax credit carryforwards	5,703	6,450
Stock-based compensation	976	750
Depreciable assets	822	851
Other assets	938	1,039
Total deferred tax assets	55,449	58,292
Deferred tax liabilities:
Intangible assets	(3,428)	(1,342)
Prepaid expenses	(572)	(532)
Total deferred tax assets	51,449	56,418
Less valuation allowance	(22,667)	(30,773)
Net deferred tax assets	$ 28,782	$ 25,645

Employee Benefit Plan - Additio

Employee Benefit Plan - Additional Information (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Compensation And Retirement Disclosure [Abstract]
Net contribution from operations to employee benefit plan	$ 611	$ 512	$ 448

Zix Repurchase Program - Additi

Zix Repurchase Program - Additional Information (Detail) - USD ($)	Apr. 24, 2017	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Equity, Class of Treasury Stock [Line Items]
Share repurchase program authorized amount	$ 10,000,000
Share repurchase program expiration date	May 31, 2018
Treasury repurchase program		$ 5,393,000	$ 3,811,000	$ 15,000,000
January 2016 Stock Repurchase Program [Member]
Equity, Class of Treasury Stock [Line Items]
Shares repurchased		1,206,994	750,000
Treasury repurchase program		$ 5,400,000	$ 3,800,000

Acquisitions - Additional Infor

Acquisitions - Additional Information (Detail) $ in Thousands	Apr. 02, 2018USD ($)Channel	Sep. 13, 2017USD ($)	Mar. 15, 2017USD ($)	Dec. 31, 2018USD ($)	Dec. 30, 2018USD ($)	Dec. 31, 2017USD ($)	Mar. 31, 2019USD ($)	Mar. 31, 2018USD ($)
Business Acquisition [Line Items]
Cash consideration				$ 11,773		$ 8,244
Greenview Data, Inc [Member]
Business Acquisition [Line Items]
Total purchase price			$ 7,700
Cash consideration			6,700
Cash consideration paid through escrow deposit			$ 650
Escrow account certain indemnification claims, period			2 years
Business combination, pay earnout consideration in cash on achievement of certain sale milestones								$ 800
Business combination, revenue				3,400		2,400
Business combination, acquisition related costs				476		427
Greenview Data, Inc [Member] | Trademarks [Member]
Business Acquisition [Line Items]
Intangible assets, estimated useful live			5 years
Greenview Data, Inc [Member] | Internally Developed Software [Member]
Business Acquisition [Line Items]
Intangible assets, estimated useful live			10 years
Greenview Data, Inc [Member] | Customer Relationships [Member]
Business Acquisition [Line Items]
Intangible assets, estimated useful live			15 years
Greenview Data, Inc [Member] | Scenario, Forecast
Business Acquisition [Line Items]
Business combination, pay earnout consideration in cash on achievement of certain sale milestones							$ 800
Entelligence Messaging Server [Member]
Business Acquisition [Line Items]
Business combination, acquisition related costs				58		$ 59
Cash purchase price		$ 1,700
Erado [Member]
Business Acquisition [Line Items]
Total purchase price	$ 14,400
Cash consideration	11,800
Cash consideration paid through escrow deposit	$ 2,300
Escrow account certain indemnification claims, period	2 years
Business combination, revenue				$ 2,100
Business combination, acquisition related costs					$ 334
Number of channels | Channel	50
Holdback amount released to selling shareholders upon one year anniversary of closing acquisition	$ 1,100
Holdback released to selling shareholders, description				An amount equal to $1.1 million of the holdback amount, less any amounts paid or otherwise subject to an outstanding claim for indemnification, will be released to the selling shareholders upon the one year anniversary of the closing of the acquisition, and the balance of the holdback amount, if any, will be distributed to the Selling Shareholders following the two year anniversary of the closing of the acquisition.
Erado [Member] | Trademarks [Member]
Business Acquisition [Line Items]
Intangible assets, estimated useful live	5 years
Erado [Member] | Internally Developed Software [Member]
Business Acquisition [Line Items]
Intangible assets, estimated useful live	10 years
Erado [Member] | Customer Relationships [Member]
Business Acquisition [Line Items]
Intangible assets, estimated useful live	15 years

Acquisitions - Summary of Estim

Acquisitions - Summary of Estimated Fair Value of Acquired Assets and Liabilities (Detail) - USD ($) $ in Thousands	Dec. 31, 2018	Apr. 02, 2018	Dec. 31, 2017	Sep. 13, 2017	Mar. 15, 2017	Dec. 31, 2016
Assets:
Goodwill	$ 13,783		$ 8,469			$ 2,161
Greenview Data, Inc [Member]
Assets:
Current assets					$ 334
Property and equipment					249
Goodwill					4,343
Total assets					9,966
Liabilities:
Deferred revenue					537
Other current liabilities					124
Deferred tax liability					1,609
Total liabilities					2,270
Net assets recorded					7,696
Entelligence Messaging Server [Member]
Assets:
Goodwill				$ 1,063
Total assets				1,983
Liabilities:
Deferred revenue				333
Total liabilities				333
Net assets recorded				1,650
Erado [Member]
Assets:
Current assets		$ 848
Property and equipment		169
Goodwill		6,215
Total assets		15,282
Liabilities:
Deferred revenue		809
Other current liabilities		93
Total liabilities		902
Net assets recorded		14,380
Trademark/names [Member] | Greenview Data, Inc [Member]
Assets:
Intangible assets					170
Trademark/names [Member] | Entelligence Messaging Server [Member]
Assets:
Intangible assets				140
Trademark/names [Member] | Erado [Member]
Assets:
Intangible assets		260
Technology [Member] | Greenview Data, Inc [Member]
Assets:
Intangible assets					1,990
Technology [Member] | Entelligence Messaging Server [Member]
Assets:
Intangible assets				550
Technology [Member] | Erado [Member]
Assets:
Intangible assets		3,030
Customer Relationships [Member] | Greenview Data, Inc [Member]
Assets:
Intangible assets					$ 2,880
Customer Relationships [Member] | Entelligence Messaging Server [Member]
Assets:
Intangible assets				$ 230
Customer Relationships [Member] | Erado [Member]
Assets:
Intangible assets		$ 4,760

Acquisitions - Unaudited Pro Fo

Acquisitions - Unaudited Pro Forma Financial Information (Detail) - Greenview Data, Inc and Entelligence Messaging Server [Member] - USD ($) $ / shares in Units, $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017
Business Acquisition [Line Items]
Revenues	$ 71,762	$ 69,587
Net income (loss)	$ 18,330	$ (6,981)
Basic income (loss) per common share	$ 0.35	$ (0.13)
Diluted income (loss) per common share	$ 0.34	$ (0.13)

Quarterly Results of Operatio_3

Quarterly Results of Operations (Unaudited) - Summary of Quarterly Results of Operations (Detail) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Quarterly Financial Information Disclosure [Abstract]
Revenues	$ 18,448	$ 17,876	$ 17,500	$ 16,654	$ 16,800	$ 16,592	$ 16,378	$ 15,893	$ 70,478	$ 65,663	$ 60,144
Gross margin	14,451	14,006	13,694	13,140	13,540	13,320	13,131	13,070	55,292	53,061	49,611
Net income (loss)	$ 9,240	$ 2,455	$ 1,840	$ 1,892	$ (12,877)	$ 1,905	$ 1,139	$ 1,775	$ 15,444	$ (8,057)	$ 5,837
Basic net income (loss) per common share	$ 0.18	$ 0.05	$ 0.04	$ 0.04	$ (0.24)	$ 0.04	$ 0.02	$ 0.03	$ 0.29	$ (0.15)	$ 0.11
Diluted net income (loss) per common share	$ 0.17	$ 0.05	$ 0.03	$ 0.04	$ (0.24)	$ 0.03	$ 0.02	$ 0.03	$ 0.29	$ (0.15)	$ 0.11
Comprehensive Income	$ 9,224								$ 15,428	$ (8,057)	$ 5,837

Subsequent Events - Additional

Subsequent Events - Additional Information (Detail)	Feb. 20, 2019USD ($)CustomerServiceProvider$ / shares	Dec. 31, 2018$ / shares	Dec. 31, 2017$ / shares
Subsequent Event [Line Items]
Preferred stock, par value | $ / shares		$ 1	$ 1
Subsequent Event [Member] | AppRiver Companies [Member]
Subsequent Event [Line Items]
Percentage of equity interest acquired	100.00%
Cash purchase price	$ 275,000,000
Number of customers | Customer	60,000
Number of managed service providers | ServiceProvider	4,500
Subsequent Event [Member] | AppRiver Companies [Member] | True Wind Capital [Member] | Series A Convertible Preferred Stock [Member] | Private Placement [Member]
Subsequent Event [Line Items]
Preferred stock, par value | $ / shares	$ 1
Share price | $ / shares	1,000
Subsequent Event [Member] | AppRiver Companies [Member] | True Wind Capital [Member] | Series B Convertible Preferred Stock [Member] | Private Placement [Member]
Subsequent Event [Line Items]
Preferred stock, par value | $ / shares	1
Share price | $ / shares	$ 1,000
Subsequent Event [Member] | AppRiver Companies [Member] | True Wind Capital [Member] | Series A and B Convertible Preferred Stock [Member] | Private Placement [Member]
Subsequent Event [Line Items]
Aggregate purchase price of preferred stock issued in private placement	$ 100,000,000
Subsequent Event [Member] | AppRiver Companies [Member] | Credit Agreement [Member] | Syndicate of Lenders and SunTrust Bank [Member] | Senior Secured Term Loan Facility [Member]
Subsequent Event [Line Items]
Aggregate principal amount	175,000,000
Subsequent Event [Member] | AppRiver Companies [Member] | Credit Agreement [Member] | Syndicate of Lenders and SunTrust Bank [Member] | Senior Secured Delayed Draw Term Loan Facility [Member]
Subsequent Event [Line Items]
Aggregate principal amount	10,000,000
Subsequent Event [Member] | AppRiver Companies [Member] | Credit Agreement [Member] | Syndicate of Lenders and SunTrust Bank [Member] | Senior Secured Revolving Credit Facility [Member]
Subsequent Event [Line Items]
Aggregate principal amount	25,000,000
Subsequent Event [Member] | AppRiver Companies [Member] | Credit Agreement [Member] | Syndicate of Lenders and SunTrust Bank [Member] | Senior Secured Revolving Credit Facility [Member] | Maximum [Member]
Subsequent Event [Line Items]
Letters of credit	$ 5,000,000