SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES	12 Months Ended
Mar. 31, 2019
Accounting Policies [Abstract]
SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES	SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES Principles of Consolidation The consolidated financial statements include the accounts of NetScout and its wholly owned subsidiaries. Inter-company transactions and balances have been eliminated in consolidation. Certain amounts for the twelve months ended March 31, 2018 and March 31, 2017, respectively, have been reclassified to conform to the current period presentation. These reclassifications had no effect on the reported results of operations. Segment Reporting The Company's operating segments are determined based on the units that constitute a business for which financial information is available and for which operating results are regularly reviewed by the Chief Operating Decision Maker (CODM). The Company reports revenue and income in one reportable segment. Use of Estimates The preparation of financial statements in conformity with generally accepted accounting principles (GAAP) requires management to make estimates and assumptions that affect the reported amounts of assets and liabilities and disclosures of contingent assets and liabilities at the date of the consolidated financial statements and the reported amounts of revenues and expenses during the reporting period. Significant estimates in these financial statements include those involving revenue recognition, valuation of goodwill and acquired assets and liabilities, valuation of the pension obligation, valuation of contingent consideration and share-based compensation. These items are continuously monitored and analyzed by management for changes in facts and circumstances and material changes in these estimates could occur in the future. Cash and Cash Equivalents and Marketable Securities Under current authoritative guidance, NetScout has classified its investments as "available-for-sale" which are carried at fair value based on quoted market prices and associated unrealized gains or losses are recorded as a separate component of stockholders’ equity until realized. NetScout considers all highly liquid investments purchased with an original maturity of three months or less to be cash equivalents and those investments with original maturities greater than three months to be marketable securities. At March 31, 2019 and periodically throughout the year, NetScout has maintained cash balances in various operating accounts in excess of federally insured limits. NetScout limits the amount of credit exposure by investing only with credit worthy institutions which the Company believes are those institutions with an investment grade rating for deposits. Revenue Recognition The Company accounts for revenue in accordance with ASU No. 2014-09, Revenue from Contracts with Customers (Topic 606), which was adopted on April 1, 2018 using the modified retrospective transition method. For further discussion of the Company's accounting policies related to revenue see Note 3, "Revenue Recognition." Commission Expense Sales commissions are recorded as an asset when the initial contract's duration is longer than 12 months and amortized to expense ratably over the remaining performance periods of the related contracts. Uncollected Deferred Revenue Because of NetScout's revenue recognition policies, there are circumstances for which the Company does not recognize revenue relating to sales transactions that have been billed, but the related account receivable has not been collected. While the receivable represents an enforceable obligation, for balance sheet presentation purposes, the Company has not recognized the deferred revenue or the related account receivable and no amounts appear in the consolidated balance sheets for such transactions because control of the underlying deliverable has not transferred. The aggregate amount of unrecognized accounts receivable and deferred revenue was $23.3 million and $20.0 million at March 31, 2019 and 2018, respectively. Concentration of Credit Risk Financial instruments that potentially subject the Company to concentration of credit risk consist primarily of investments, trade accounts receivable and accounts payable. NetScout's cash, cash equivalents, and marketable securities are placed with financial institutions with high credit standings. At March 31, 2019 and 2018 respectively, the Company had no direct customers or indirect channel partners which accounted for more than 10% of the accounts receivable balance. During the fiscal years ended March 31, 2019 and 2018 respectively, no direct customers or indirect channel partners accounted for more than 10% of total revenue. During the fiscal year ended March 31, 2017, one direct customer, Verizon Communications Inc. (Verizon), accounted for more than 10% of total revenue, while no indirect channel partner accounted for more than 10% of total revenue. Historically, the Company has not experienced any significant failure of its customers to meet their payment obligations nor does the Company anticipate material non-performance by its customers in the future; accordingly, the Company does not require collateral from its customers. However, if the Company’s assumptions are incorrect, there could be an adverse impact on its allowance for doubtful accounts. Trade Receivable Valuations Accounts receivable are stated at their net realizable value. The allowance against gross trade receivables reflects the best estimate of probable losses inherent in the receivables portfolio determined on the basis of historical experience, specific allowances for known troubled accounts and other currently available information. Inventories Inventories are stated at the lower of actual cost or net realizable value. Cost is determined by using the first-in, first-out (FIFO) method. Fixed Assets Fixed assets are stated at cost and depreciated using the straight-line method over the estimated useful lives of the assets. Leasehold improvements are amortized on a straight-line basis over the shorter of the lease term or anticipated useful life of the improvement. Gains and losses upon asset disposal are recognized in the year of disposition. Expenditures for replacements and building improvements are capitalized, while expenditures for maintenance and repairs are charged against earnings as incurred. Valuation of Goodwill, Intangible Assets and Other Acquisition and Divestiture Accounting Items The Company amortizes acquired definite-lived intangible assets over their estimated useful lives. Goodwill and other indefinite-lived intangible assets are not amortized but subject to annual impairment tests; more frequently if events or circumstances occur that would indicate a potential decline in their fair value. The Company performs the assessment annually during the fourth quarter and on an interim basis if potential impairment indicators arise. The Company has identified two reporting units: (1) Service Assurance and (2) Security. To test impairment, the Company first assesses qualitative factors to determine whether the existence of events and circumstances indicate that it is more likely than not that the intangible asset is impaired. If based on the Company's qualitative assessment it is more likely than not that the fair value of the intangible asset is less than its carrying amount, quantitative impairment testing is required. However, if the Company concludes otherwise, quantitative impairment testing is not required. During fiscal year 2019, the Company performed a quantitative analysis for goodwill. The Company determined the fair value of the reporting unit's goodwill using established income and market valuation approaches. Goodwill was estimated to be recoverable as of January 31, 2019. Indefinite-lived intangible assets are tested for impairment at least annually, or on an interim basis if an event occurs or circumstances change that would, more likely than not, reduce the fair value of the indefinite-lived intangible assets below its carrying value. To test impairment, the Company first assesses qualitative factors to determine whether the existence of events and circumstances indicate that it is more likely than not that the indefinite-lived intangible is impaired. If based on the Company's qualitative assessment, the Company concludes that it is more likely than not that the fair value of the indefinite-lived asset is greater than its carrying amount, quantitative impairment testing is not required. The Company completed its annual impairment test of the indefinite-lived intangible asset at January 31, 2019 using the qualitative Step 0 assessment. No impairment indicators were observed as of January 31, 2019. The Company completed two acquisitions and one divestiture during the three-year period ended March 31, 2019. The acquisition method of accounting requires an estimate of the fair value of the assets and liabilities acquired as part of these transactions. In order to estimate the fair value of acquired intangible assets, the Company uses a relief from royalty model which requires management to estimate: future revenues expected to be generated by the acquired intangible assets, a royalty rate which a market participant would pay related to the projected revenue stream, a present value factor which approximates a risk adjusted rate of return for a market participant purchasing the assets, and a technology migration curve representing a period of time over which the technology assets or some portion thereof are still being used. The Company is also required to develop the fair value for customer relationships acquired as part of these transactions which requires that it create estimates for the following items: a projection of future revenues associated with the acquired company's existing customers, a turnover rate for those customers, a margin related to those sales, and a risk adjusted rate of return for a market participant purchasing those relationships. The Company has a contingent consideration asset related to the divestiture of its handheld network test (HNT) tools business in September 2018. The contingent consideration asset represents potential future earnout payments to the Company of up to $4.0 million over two years that are contingent on the HNT tools business achieving certain milestones. The fair value of the contingent consideration of $2.3 million was recognized on the acquisition date and was measured using unobservable (Level 3) inputs. The value of the contingent consideration asset at March 31, 2019 was $0.8 million. The Company had a contingent liability at March 31, 2018 for $523 thousand related to the acquisition of Efflux in July 2017 for which an escrow account was established to cover damages NetScout may have suffered related to any liabilities that NetScout did not agree to assume or as a result of the breach of representations and warranties of the seller as described in the merger agreement. The $523 thousand was paid to the seller in July 2018. The Company had a contingent liability at March 31, 2018 for $4.9 million related to the acquisition of Simena LLC in November 2011, which was based on the ultimate settlement of assets and liabilities acquired as part of the transaction, and the former owners' future period of employment with NetScout. The contingent purchase consideration of $5.0 million was paid to the seller in November 2018. The Company had $660 thousand of contingent purchase consideration related to the acquisition of Avvasi Incorporated (Avvasi) in August 2016 for which an escrow account was established to cover damages NetScout may have suffered related to any liabilities that NetScout did not agree to assume or as a result of the breach of representations and warranties of the seller as described in the asset purchase agreement. The $660 thousand was paid to the seller in August 2017. Capitalized Software Development Costs Costs incurred in the research and development of the Company’s products are expensed as incurred, except for certain software development costs. Costs associated with the development of computer software are expensed prior to the establishment of technological feasibility and capitalized thereafter until the related software products are available for first customer shipment. Such costs are amortized using the straight-line method over the estimated economic life of the product, which generally does not exceed three years. Capitalized software development costs are periodically assessed for recoverability in the event of changes to the anticipated future revenue for the software products or changes in product technologies. Unamortized capitalized software development costs that are determined to be in excess of the net realizable value of the software products would be expensed in the period in which such a determination is made. Typically for accounting purposes, these R&D investments have not been capitalized because of the development methodology employed. The developments are added individually to the core code over a shorter period of time but marketed as a release once all portions are complete. Amortization included as cost of product revenue was $1.1 million, $1.0 million and $594 thousand for the fiscal years ended March 31, 2019, 2018, and 2017, respectively. The Company capitalized $0.1 million and $0.1 million in software development costs in the fiscal years ended March 31, 2019 and 2018. Derivative Financial Instruments Under authoritative guidance for derivative instruments and hedging activities, all hedging activities must be documented at the inception of the hedge and must meet the definition of highly effective in offsetting changes to future cash flows in order for the derivative to qualify for hedge accounting. Under the guidance, if an instrument qualifies for hedge accounting, the changes in the fair value each period for open contracts, measured at the end of the period, are recorded to other comprehensive income. Otherwise, changes in the fair value are recorded in earnings each period. Management must perform initial and ongoing tests in order to qualify for hedge accounting. In accordance with the guidance, the Company accounts for its instruments under hedge accounting. The effectiveness and a measurement of ineffectiveness of qualifying hedge contracts are assessed by the Company quarterly. The Company records the fair value of its derivatives in prepaid expenses and other current assets and accrued other in the Company's consolidated balance sheet. The effective portion of gains or losses resulting from changes in the fair value of qualifying hedges are recorded in other comprehensive income (loss) until the forecasted transaction occurs, with any ineffective portion classified directly to the Company’s consolidated statement of operations based on the expense categories of the items being hedged. When forecasted transactions occur, unrealized gains or losses associated with the effective portion of the hedge are reclassified to the respective expense categories in the Company’s consolidated statement of operations. Gains or losses related to hedging activity are included as operating activities in the Company’s consolidated statement of cash flows. If the underlying forecasted transactions do not occur, or it becomes probable that they will not occur, the gain or loss on the related cash flow hedge is recognized immediately in earnings. Contingencies NetScout accounts for claims and contingencies in accordance with authoritative guidance that requires an estimated loss to be recorded from a claim or loss contingency when information available prior to issuance of its consolidated financial statements indicates that it is probable that a liability has been incurred at the date of the consolidated financial statements and the amount of the loss can be reasonably estimated. If NetScout determines that it is reasonably possible but not probable that an asset has been impaired or a liability has been incurred or if the amount of a probable loss cannot be reasonably estimated, then in accordance with the authoritative guidance, Netscout discloses the amount or range of estimated loss if the amount or range of estimated loss is material. Accounting for claims and contingencies requires NetScout to use its judgment. NetScout consults with legal counsel on those issues related to litigation and seeks input from other experts and advisors with respect to matters in the ordinary course of business. Contingent assets and liabilities include contingent consideration in connection with the Company’s acquisitions and divestitures. Contingent consideration represents earnout payments in connection with the Company’s acquisitions and divestitures and is recognized at fair value on the acquisition date and remeasured each reporting period with subsequent adjustments recognized in the consolidated statements of income. The Company discounts the contingent purchase consideration to present value using a risk adjusted interest rate at each reporting period. Contingent consideration is valued using significant inputs that are not observable in the market which are defined as Level 3 inputs pursuant to fair value measurement accounting. The Company believes its estimates and assumptions are reasonable, however, there is significant judgment involved. Changes in the fair value of contingent assets and liabilities may result from changes in discount periods. The Company reflects changes in fair value due to probability changes in earnings in the consolidated statements of income. Earnout payments are reflected in both cash flows from operating and financing activities and the changes in fair value are reflected in cash flows from operating activities in the consolidated statements of cash flows. Share-Based Compensation NetScout recognizes compensation expense for all share-based payments granted. Under the fair value recognition provisions, share-based compensation is calculated net of an estimated forfeiture rate and compensation cost is only recognized for those shares expected to vest on a straight-line basis over the expected requisite service period of the award. Foreign Currency NetScout accounts for its reporting of foreign operations in accordance with guidance which establishes guidelines for the determination of the functional currency of foreign subsidiaries. In accordance with the guidance, NetScout has determined its functional currency for those foreign subsidiaries that are an extension of NetScout's U.S. operations to be the U.S. Dollar. Assets and liabilities of subsidiaries operating outside the United States with a functional currency other than U.S. dollars are translated into United States dollars using the period-end exchange rate, and income and expense items are translated using the average exchange rate during the period. Cumulative translation adjustments are reflected as a separate component of stockholders’ equity. NetScout will experience currency exchange risk with respect to foreign currency denominated expenses. In order to partially offset the risks associated with the effects of certain foreign currency exposures, NetScout has established a program that utilizes foreign currency forward contracts. Under this program, increases or decreases in foreign currency exposures are partially offset by gains or losses on forward contracts, to mitigate the impact of foreign currency transaction gains or losses. The Company does not use forward contracts to engage in currency speculation. All outstanding foreign currency forward contracts are recorded at fair value at the end of each fiscal period. The Company had foreign currency losses of $2.0 million, $4.1 million and $2.5 million for the fiscal years ended March 31, 2019, 2018 and 2017, respectively. These amounts are included in other expense, net. Advertising Expense NetScout recognizes advertising expense as incurred. Advertising expense was $9.4 million, $6.5 million and $8.1 million for the fiscal years ended March 31, 2019, 2018 and 2017, respectively. Comprehensive Income (Loss) Comprehensive income (loss) consists of net income (loss) and other comprehensive income (loss). Other comprehensive income (loss) typically consists of unrealized gains and losses on marketable securities, unrealized gain (loss) on hedge contracts, actuarial gains and losses, and foreign currency translation adjustments. Income Taxes NetScout accounts for its income taxes under the asset and liability method. Under the asset and liability method, deferred tax assets and liabilities are recognized based on anticipated future tax consequences attributable to differences between financial statement carrying amounts of assets and liabilities and their respective tax basis, as well as the effect of any net operating loss and tax credit carryforwards. Income tax expense is comprised of the current tax liability or benefit and the change in deferred tax assets and liabilities. NetScout evaluates the recoverability of deferred tax assets by considering all positive and negative evidence relating to future profitability. NetScout weighs objective and verifiable evidence more heavily in this analysis. In situations where NetScout concludes that it does not have sufficient objective and verifiable evidence to support the realizability of the deferred tax asset, NetScout creates a valuation allowance against it. Recent Accounting Standards In August 2018, the Financial Accounting Standards Board (FASB) issued Accounting Standards Update 2018-15, Intangibles – Goodwill and Other – Internal-Use Software (Subtopic 350-40): Customer’s Accounting for Implementation Costs Incurred in a Cloud Computing Arrangement That Is a Service Contract (ASU 2018-15). This ASU clarifies the accounting treatment for implementation costs for cloud computing arrangements (hosting arrangements) that is a service contract. This guidance is effective for fiscal years beginning after December 15, 2019, including interim periods within that fiscal year. The Company adopted ASU 2018-15 effective July 1, 2018. The adoption has had an immaterial impact to the consolidated financial statements for the twelve months ended March 31, 2019. In August 2018, the FASB issued ASU 2018-14, Compensation – Retirement Benefits – Defined Benefit Plans – General (Subtopic 715-20): Disclosure Framework—Changes to the Disclosure Requirements for Defined Benefit Plans. This ASU adds, modifies and clarifies several disclosure requirements for employers that sponsor defined benefit pension or other postretirement plans. This guidance is effective for fiscal years ending after December 15, 2020. ASU 2018-14 is effective for NetScout beginning April 1, 2021. Early adoption is permitted. The Company is currently assessing the effect that ASU 2018-14 will have on its financial position, results of operations, and disclosures. In August 2018, the FASB issued ASU 2018-13, Fair Value Measurement (Topic 820): Disclosure Framework – Changes to the Disclosure Requirements for Fair Value Measurement. ASU 2018-13 adds, modifies and removes several disclosure requirements relative to the three levels of inputs used to measure fair value in accordance with Topic 820, Fair Value Measurement. This guidance is effective for fiscal years beginning after December 15, 2019, including interim periods within that fiscal year. ASU 2018-13 is effective for NetScout beginning April 1, 2020. Early adoption is permitted. The Company is currently assessing the effect that ASU 2018-13 will have on its financial position, results of operations, and disclosures. In February 2018, the FASB issued ASU 2018-02, Reclassification of Certain Tax Effects From Accumulated Other Comprehensive Income. ASU 2018-02 amends ASC 220, Income Statement - Reporting Comprehensive Income, to allow a reclassification from accumulated other comprehensive income to retained earnings for stranded tax effects resulting from the Tax Act. In addition, under the ASU 2018-02, the Company may be required to provide certain disclosures regarding stranded tax effects. ASU 2018-02 is effective for years beginning after December 15, 2018, and interim periods within those fiscal years. ASU 2018-02 is effective for the Company beginning April 1, 2019. Early adoption is permitted. The Company does not believe the adoption of ASU 2018-02 will have a material impact on its consolidated financial statements. In August 2017, the FASB issued ASU 2017-12, Derivatives and Hedging (Topic 815), Targeted Improvements to Accounting for Hedging Activities (ASU 2017-12). ASU 2017-12 intends to better align an entity's risk management activities and financial reporting for hedging relationships through changes to both the designation and measurement guidance for qualifying hedging relationships and the presentation of hedge results. The amendments expand and refine hedge accounting for both non-financial and financial risk components and align the recognition and presentation of the effects of the hedging instrument and the hedged item in the financial statements. This standard is effective for financial statements issued for fiscal years beginning after December 15, 2018, with early adoption permitted. ASU 2017-12 is effective for the Company beginning April 1, 2019. The Company does not believe the adoption of ASU 2017-12 will have a material impact on its consolidated financial statements. In February 2016, the FASB issued ASU 2016-02, Leases (Topic 842) and issued subsequent amendments to initial guidance: ASU 2017-13, ASU 2018-10, ASU 2018-11, ASU 2018-20 and ASU 2019-01 (collectively, Topic 842). ASC 842 aims to increase transparency and comparability among organizations with respect to accounting for leases. Lessees will recognize a right-of-use (ROU) asset and a lease liability measured at the present value of lease payments for virtually all of their leases. Short term leases with a term of 12 months or less are not required to be recognized. ASC 842 also requires disclosure of key information about leasing arrangements. ASC 842 will be effective for fiscal years beginning after December 15, 2018, including interim periods within such fiscal years. Early adoption is permitted. The Company adopted the new standard on April 1, 2019 using the effective date as the date of initial application. Consequently, financial information will not be updated and disclosures required under the new standard will not be provided for dates and periods before April 1, 2019. The new standard provides a number of optional practical expedients in transition. The Company elected the package of practical expedients, which among other things, allows the carryforward of the historical lease classification. Further, the Company elected the practical expedients to combine lease and non-lease components, and to not recognize ROU assets and lease liabilities for short-term leases. The Company currently anticipates that the adoption of this new standard will materially impact the consolidated balance sheets by recognizing new ROU assets and lease liabilities for operating leases with the most significant impact from the recognition of ROU assets and lease liabilities related to the Company's office space operating leases. The impact on the Company's results of operations and cash flows is not expected to be material. The Company has implemented a new lease accounting system and is updating processes and controls in preparation for the adoption of the new standard, including the requirement to provide significant new disclosures about the Company's leasing activities. Please refer to Note 18, "Commitments and Contingencies" for additional information about the Company's leases, including the future minimum lease payments for operating leases at March 31, 2019. In May 2014, the FASB issued ASU No. 2014-09, Revenue from Contracts with Customers: Topic 606 (Topic 606). Topic 606 supersedes the revenue recognition requirements in Topic 605, Revenue Recognition, and requires entities to recognize revenue when control of the promised goods or services is transferred to customers at an amount that reflects the consideration to which the entity expects to be entitled to in exchange for those goods or services. The Company adopted Topic 606 as of April 1, 2018 using the modified retrospective transition method. Please refer to Note 3, "Revenue Recognition" for further details.

SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES

Principles of Consolidation

The consolidated financial statements include the accounts of NetScout and its wholly owned subsidiaries. Inter-company transactions and balances have been eliminated in consolidation.

Certain amounts for the twelve months ended March 31, 2018 and March 31, 2017, respectively, have been reclassified to conform to the current period presentation. These reclassifications had no effect on the reported results of operations.

Segment Reporting

The Company's operating segments are determined based on the units that constitute a business for which financial information is available and for which operating results are regularly reviewed by the Chief Operating Decision Maker (CODM). The Company reports revenue and income in one reportable segment.

Use of Estimates

The preparation of financial statements in conformity with generally accepted accounting principles (GAAP) requires management to make estimates and assumptions that affect the reported amounts of assets and liabilities and disclosures of contingent assets and liabilities at the date of the consolidated financial statements and the reported amounts of revenues and expenses during the reporting period. Significant estimates in these financial statements include those involving revenue recognition, valuation of goodwill and acquired assets and liabilities, valuation of the pension obligation, valuation of contingent consideration and share-based compensation. These items are continuously monitored and analyzed by management for changes in facts and circumstances and material changes in these estimates could occur in the future.

Cash and Cash Equivalents and Marketable Securities

Under current authoritative guidance, NetScout has classified its investments as "available-for-sale" which are carried at fair value based on quoted market prices and associated unrealized gains or losses are recorded as a separate component of stockholders’ equity until realized. NetScout considers all highly liquid investments purchased with an original maturity of three months or less to be cash equivalents and those investments with original maturities greater than three months to be marketable securities.

At March 31, 2019 and periodically throughout the year, NetScout has maintained cash balances in various operating accounts in excess of federally insured limits. NetScout limits the amount of credit exposure by investing only with credit worthy institutions which the Company believes are those institutions with an investment grade rating for deposits.

Revenue Recognition

The Company accounts for revenue in accordance with ASU No. 2014-09, Revenue from Contracts with Customers (Topic 606), which was adopted on April 1, 2018 using the modified retrospective transition method. For further discussion of the Company's accounting policies related to revenue see Note 3, "Revenue Recognition."

Commission Expense

Sales commissions are recorded as an asset when the initial contract's duration is longer than 12 months and amortized to expense ratably over the remaining performance periods of the related contracts.

Uncollected Deferred Revenue

Because of NetScout's revenue recognition policies, there are circumstances for which the Company does not recognize revenue relating to sales transactions that have been billed, but the related account receivable has not been collected. While the receivable represents an enforceable obligation, for balance sheet presentation purposes, the Company has not recognized the deferred revenue or the related account receivable and no amounts appear in the consolidated balance sheets for such transactions because control of the underlying deliverable has not transferred. The aggregate amount of unrecognized accounts receivable and deferred revenue was $23.3 million and $20.0 million at March 31, 2019 and 2018, respectively.

Concentration of Credit Risk

Financial instruments that potentially subject the Company to concentration of credit risk consist primarily of investments, trade accounts receivable and accounts payable. NetScout's cash, cash equivalents, and marketable securities are placed with financial institutions with high credit standings.

At March 31, 2019 and 2018 respectively, the Company had no direct customers or indirect channel partners which accounted for more than 10% of the accounts receivable balance.

During the fiscal years ended March 31, 2019 and 2018 respectively, no direct customers or indirect channel partners accounted for more than 10% of total revenue. During the fiscal year ended March 31, 2017, one direct customer, Verizon Communications Inc. (Verizon), accounted for more than 10% of total revenue, while no indirect channel partner accounted for more than 10% of total revenue.

Historically, the Company has not experienced any significant failure of its customers to meet their payment obligations nor does the Company anticipate material non-performance by its customers in the future; accordingly, the Company does not require collateral from its customers. However, if the Company’s assumptions are incorrect, there could be an adverse impact on its allowance for doubtful accounts.

Trade Receivable Valuations

Accounts receivable are stated at their net realizable value. The allowance against gross trade receivables reflects the best estimate of probable losses inherent in the receivables portfolio determined on the basis of historical experience, specific allowances for known troubled accounts and other currently available information.

Inventories

Inventories are stated at the lower of actual cost or net realizable value. Cost is determined by using the first-in, first-out (FIFO) method.

Fixed Assets

Fixed assets are stated at cost and depreciated using the straight-line method over the estimated useful lives of the assets. Leasehold improvements are amortized on a straight-line basis over the shorter of the lease term or anticipated useful life of the improvement. Gains and losses upon asset disposal are recognized in the year of disposition. Expenditures for replacements and building improvements are capitalized, while expenditures for maintenance and repairs are charged against earnings as incurred.

Valuation of Goodwill, Intangible Assets and Other Acquisition and Divestiture Accounting Items

The Company amortizes acquired definite-lived intangible assets over their estimated useful lives. Goodwill and other indefinite-lived intangible assets are not amortized but subject to annual impairment tests; more frequently if events or circumstances occur that would indicate a potential decline in their fair value. The Company performs the assessment annually during the fourth quarter and on an interim basis if potential impairment indicators arise. The Company has identified two reporting units: (1) Service Assurance and (2) Security.

To test impairment, the Company first assesses qualitative factors to determine whether the existence of events and circumstances indicate that it is more likely than not that the intangible asset is impaired. If based on the Company's qualitative assessment it is more likely than not that the fair value of the intangible asset is less than its carrying amount, quantitative impairment testing is required. However, if the Company concludes otherwise, quantitative impairment testing is not required. During fiscal year 2019, the Company performed a quantitative analysis for goodwill. The Company determined the fair value of the reporting unit's goodwill using established income and market valuation approaches. Goodwill was estimated to be recoverable as of January 31, 2019.

Indefinite-lived intangible assets are tested for impairment at least annually, or on an interim basis if an event occurs or circumstances change that would, more likely than not, reduce the fair value of the indefinite-lived intangible assets below its carrying value. To test impairment, the Company first assesses qualitative factors to determine whether the existence of events and circumstances indicate that it is more likely than not that the indefinite-lived intangible is impaired. If based on the Company's qualitative assessment, the Company concludes that it is more likely than not that the fair value of the indefinite-lived asset is greater than its carrying amount, quantitative impairment testing is not required. The Company completed its annual impairment test of the indefinite-lived intangible asset at January 31, 2019 using the qualitative Step 0 assessment. No impairment indicators were observed as of January 31, 2019.

The Company completed two acquisitions and one divestiture during the three-year period ended March 31, 2019. The acquisition method of accounting requires an estimate of the fair value of the assets and liabilities acquired as part of these transactions. In order to estimate the fair value of acquired intangible assets, the Company uses a relief from royalty model which requires management to estimate: future revenues expected to be generated by the acquired intangible assets, a royalty rate which a market participant would pay related to the projected revenue stream, a present value factor which approximates a risk adjusted rate of return for a market participant purchasing the assets, and a technology migration curve representing a period of time over which the technology assets or some portion thereof are still being used. The Company is also required to develop the fair value for customer relationships acquired as part of these transactions which requires that it create estimates for the following items: a projection of future revenues associated with the acquired company's existing customers, a turnover rate for those customers, a margin related to those sales, and a risk adjusted rate of return for a market participant purchasing those relationships.

The Company has a contingent consideration asset related to the divestiture of its handheld network test (HNT) tools business in September 2018. The contingent consideration asset represents potential future earnout payments to the Company of up to $4.0 million over two years that are contingent on the HNT tools business achieving certain milestones. The fair value of the contingent consideration of $2.3 million was recognized on the acquisition date and was measured using unobservable (Level 3) inputs. The value of the contingent consideration asset at March 31, 2019 was $0.8 million.

The Company had a contingent liability at March 31, 2018 for $523 thousand related to the acquisition of Efflux in July 2017 for which an escrow account was established to cover damages NetScout may have suffered related to any liabilities that NetScout did not agree to assume or as a result of the breach of representations and warranties of the seller as described in the merger agreement. The $523 thousand was paid to the seller in July 2018.

The Company had a contingent liability at March 31, 2018 for $4.9 million related to the acquisition of Simena LLC in November 2011, which was based on the ultimate settlement of assets and liabilities acquired as part of the transaction, and the former owners' future period of employment with NetScout. The contingent purchase consideration of $5.0 million was paid to the seller in November 2018.

The Company had $660 thousand of contingent purchase consideration related to the acquisition of Avvasi Incorporated (Avvasi) in August 2016 for which an escrow account was established to cover damages NetScout may have suffered related to any liabilities that NetScout did not agree to assume or as a result of the breach of representations and warranties of the seller as described in the asset purchase agreement. The $660 thousand was paid to the seller in August 2017.

Capitalized Software Development Costs

Costs incurred in the research and development of the Company’s products are expensed as incurred, except for certain software development costs. Costs associated with the development of computer software are expensed prior to the establishment of technological feasibility and capitalized thereafter until the related software products are available for first customer shipment. Such costs are amortized using the straight-line method over the estimated economic life of the product, which generally does not exceed three years. Capitalized software development costs are periodically assessed for recoverability in the event of changes to the anticipated future revenue for the software products or changes in product technologies. Unamortized capitalized software development costs that are determined to be in excess of the net realizable value of the software products would be expensed in the period in which such a determination is made.

Typically for accounting purposes, these R&D investments have not been capitalized because of the development methodology employed. The developments are added individually to the core code over a shorter period of time but marketed as a release once all portions are complete.

Amortization included as cost of product revenue was $1.1 million, $1.0 million and $594 thousand for the fiscal years ended March 31, 2019, 2018, and 2017, respectively. The Company capitalized $0.1 million and $0.1 million in software development costs in the fiscal years ended March 31, 2019 and 2018.

Derivative Financial Instruments

Under authoritative guidance for derivative instruments and hedging activities, all hedging activities must be documented at the inception of the hedge and must meet the definition of highly effective in offsetting changes to future cash flows in order for the derivative to qualify for hedge accounting. Under the guidance, if an instrument qualifies for hedge accounting, the changes in the fair value each period for open contracts, measured at the end of the period, are recorded to other comprehensive income. Otherwise, changes in the fair value are recorded in earnings each period. Management must perform initial and ongoing tests in order to qualify for hedge accounting. In accordance with the guidance, the Company accounts for its instruments under hedge accounting. The effectiveness and a measurement of ineffectiveness of qualifying hedge contracts are assessed by the Company quarterly. The Company records the fair value of its derivatives in prepaid expenses and other current assets and accrued other in the Company's consolidated balance sheet. The effective portion of gains or losses resulting from changes in the fair value of qualifying hedges are recorded in other comprehensive income (loss) until the forecasted transaction occurs, with any ineffective portion classified directly to the Company’s consolidated statement of operations based on the expense categories of the items being hedged. When forecasted transactions occur, unrealized gains or losses associated with the effective portion of the hedge are reclassified to the respective expense categories in the Company’s consolidated statement of operations. Gains or losses related to hedging activity are included as operating activities in the Company’s consolidated statement of cash flows. If the underlying forecasted transactions do not occur, or it becomes probable that they will not occur, the gain or loss on the related cash flow hedge is recognized immediately in earnings.

Contingencies

NetScout accounts for claims and contingencies in accordance with authoritative guidance that requires an estimated loss to be recorded from a claim or loss contingency when information available prior to issuance of its consolidated financial statements indicates that it is probable that a liability has been incurred at the date of the consolidated financial statements and the amount of the loss can be reasonably estimated. If NetScout determines that it is reasonably possible but not probable that an asset has been impaired or a liability has been incurred or if the amount of a probable loss cannot be reasonably estimated, then in accordance with the authoritative guidance, Netscout discloses the amount or range of estimated loss if the amount or range of estimated loss is material. Accounting for claims and contingencies requires NetScout to use its judgment. NetScout consults with legal counsel on those issues related to litigation and seeks input from other experts and advisors with respect to matters in the ordinary course of business.

Contingent assets and liabilities include contingent consideration in connection with the Company’s acquisitions and divestitures. Contingent consideration represents earnout payments in connection with the Company’s acquisitions and divestitures and is recognized at fair value on the acquisition date and remeasured each reporting period with subsequent adjustments recognized in the consolidated statements of income. The Company discounts the contingent purchase consideration to present value using a risk adjusted interest rate at each reporting period. Contingent consideration is valued using significant inputs that are not observable in the market which are defined as Level 3 inputs pursuant to fair value measurement accounting. The Company believes its estimates and assumptions are reasonable, however, there is significant judgment involved.

Changes in the fair value of contingent assets and liabilities may result from changes in discount periods. The Company reflects changes in fair value due to probability changes in earnings in the consolidated statements of income. Earnout payments are reflected in both cash flows from operating and financing activities and the changes in fair value are reflected in cash flows from operating activities in the consolidated statements of cash flows.

Share-Based Compensation

NetScout recognizes compensation expense for all share-based payments granted. Under the fair value recognition provisions, share-based compensation is calculated net of an estimated forfeiture rate and compensation cost is only recognized for those shares expected to vest on a straight-line basis over the expected requisite service period of the award.

Foreign Currency

NetScout accounts for its reporting of foreign operations in accordance with guidance which establishes guidelines for the determination of the functional currency of foreign subsidiaries. In accordance with the guidance, NetScout has determined its functional currency for those foreign subsidiaries that are an extension of NetScout's U.S. operations to be the U.S. Dollar.

Assets and liabilities of subsidiaries operating outside the United States with a functional currency other than U.S. dollars are translated into United States dollars using the period-end exchange rate, and income and expense items are translated using the average exchange rate during the period. Cumulative translation adjustments are reflected as a separate component of stockholders’ equity.

NetScout will experience currency exchange risk with respect to foreign currency denominated expenses. In order to partially offset the risks associated with the effects of certain foreign currency exposures, NetScout has established a program that utilizes foreign currency forward contracts. Under this program, increases or decreases in foreign currency exposures are partially offset by gains or losses on forward contracts, to mitigate the impact of foreign currency transaction gains or losses. The Company does not use forward contracts to engage in currency speculation. All outstanding foreign currency forward contracts are recorded at fair value at the end of each fiscal period.

The Company had foreign currency losses of $2.0 million, $4.1 million and $2.5 million for the fiscal years ended March 31, 2019, 2018 and 2017, respectively. These amounts are included in other expense, net.

Advertising Expense

NetScout recognizes advertising expense as incurred. Advertising expense was $9.4 million, $6.5 million and $8.1 million for the fiscal years ended March 31, 2019, 2018 and 2017, respectively.

Comprehensive Income (Loss)

Comprehensive income (loss) consists of net income (loss) and other comprehensive income (loss). Other comprehensive income (loss) typically consists of unrealized gains and losses on marketable securities, unrealized gain (loss) on hedge contracts, actuarial gains and losses, and foreign currency translation adjustments.

Income Taxes

NetScout accounts for its income taxes under the asset and liability method. Under the asset and liability method, deferred tax assets and liabilities are recognized based on anticipated future tax consequences attributable to differences between financial statement carrying amounts of assets and liabilities and their respective tax basis, as well as the effect of any net operating loss and tax credit carryforwards. Income tax expense is comprised of the current tax liability or benefit and the change in deferred tax assets and liabilities. NetScout evaluates the recoverability of deferred tax assets by considering all positive and negative evidence relating to future profitability. NetScout weighs objective and verifiable evidence more heavily in this analysis. In situations where NetScout concludes that it does not have sufficient objective and verifiable evidence to support the realizability of the deferred tax asset, NetScout creates a valuation allowance against it.

Recent Accounting Standards

In August 2018, the Financial Accounting Standards Board (FASB) issued Accounting Standards Update 2018-15, Intangibles – Goodwill and Other – Internal-Use Software (Subtopic 350-40): Customer’s Accounting for Implementation Costs Incurred in a Cloud Computing Arrangement That Is a Service Contract (ASU 2018-15). This ASU clarifies the accounting treatment for implementation costs for cloud computing arrangements (hosting arrangements) that is a service contract. This guidance is effective for fiscal years beginning after December 15, 2019, including interim periods within that fiscal year. The Company adopted ASU 2018-15 effective July 1, 2018. The adoption has had an immaterial impact to the consolidated financial statements for the twelve months ended March 31, 2019.

In August 2018, the FASB issued ASU 2018-14, Compensation – Retirement Benefits – Defined Benefit Plans – General (Subtopic 715-20): Disclosure Framework—Changes to the Disclosure Requirements for Defined Benefit Plans. This ASU adds, modifies and clarifies several disclosure requirements for employers that sponsor defined benefit pension or other postretirement plans. This guidance is effective for fiscal years ending after December 15, 2020. ASU 2018-14 is effective for NetScout beginning April 1, 2021. Early adoption is permitted. The Company is currently assessing the effect that ASU 2018-14 will have on its financial position, results of operations, and disclosures.

In August 2018, the FASB issued ASU 2018-13, Fair Value Measurement (Topic 820): Disclosure Framework – Changes to the Disclosure Requirements for Fair Value Measurement. ASU 2018-13 adds, modifies and removes several disclosure requirements relative to the three levels of inputs used to measure fair value in accordance with Topic 820, Fair Value Measurement. This guidance is effective for fiscal years beginning after December 15, 2019, including interim periods within that fiscal year. ASU 2018-13 is effective for NetScout beginning April 1, 2020. Early adoption is permitted. The Company is currently assessing the effect that ASU 2018-13 will have on its financial position, results of operations, and disclosures.

In February 2018, the FASB issued ASU 2018-02, Reclassification of Certain Tax Effects From Accumulated Other Comprehensive Income. ASU 2018-02 amends ASC 220, Income Statement - Reporting Comprehensive Income, to allow a reclassification from accumulated other comprehensive income to retained earnings for stranded tax effects resulting from the Tax Act. In addition, under the ASU 2018-02, the Company may be required to provide certain disclosures regarding stranded tax effects. ASU 2018-02 is effective for years beginning after December 15, 2018, and interim periods within those fiscal years. ASU 2018-02 is effective for the Company beginning April 1, 2019. Early adoption is permitted. The Company does not believe the adoption of ASU 2018-02 will have a material impact on its consolidated financial statements.

In August 2017, the FASB issued ASU 2017-12, Derivatives and Hedging (Topic 815), Targeted Improvements to Accounting for Hedging Activities (ASU 2017-12). ASU 2017-12 intends to better align an entity's risk management activities and financial reporting for hedging relationships through changes to both the designation and measurement guidance for qualifying hedging relationships and the presentation of hedge results. The amendments expand and refine hedge accounting for both non-financial and financial risk components and align the recognition and presentation of the effects of the hedging instrument and the hedged item in the financial statements. This standard is effective for financial statements issued for fiscal years beginning after December 15, 2018, with early adoption permitted. ASU 2017-12 is effective for the Company beginning April 1, 2019. The Company does not believe the adoption of ASU 2017-12 will have a material impact on its consolidated financial statements.

In February 2016, the FASB issued ASU 2016-02, Leases (Topic 842) and issued subsequent amendments to initial guidance: ASU 2017-13, ASU 2018-10, ASU 2018-11, ASU 2018-20 and ASU 2019-01 (collectively, Topic 842). ASC 842 aims to increase transparency and comparability among organizations with respect to accounting for leases. Lessees will recognize a right-of-use (ROU) asset and a lease liability measured at the present value of lease payments for virtually all of their leases. Short term leases with a term of 12 months or less are not required to be recognized. ASC 842 also requires disclosure of key information about leasing arrangements. ASC 842 will be effective for fiscal years beginning after December 15, 2018, including interim periods within such fiscal years. Early adoption is permitted. The Company adopted the new standard on April 1, 2019 using the effective date as the date of initial application. Consequently, financial information will not be updated and disclosures required under the new standard will not be provided for dates and periods before April 1, 2019.

The new standard provides a number of optional practical expedients in transition. The Company elected the package of practical expedients, which among other things, allows the carryforward of the historical lease classification. Further, the Company elected the practical expedients to combine lease and non-lease components, and to not recognize ROU assets and lease liabilities for short-term leases.

The Company currently anticipates that the adoption of this new standard will materially impact the consolidated balance sheets by recognizing new ROU assets and lease liabilities for operating leases with the most significant impact from the recognition of ROU assets and lease liabilities related to the Company's office space operating leases. The impact on the Company's results of operations and cash flows is not expected to be material.

The Company has implemented a new lease accounting system and is updating processes and controls in preparation for the adoption of the new standard, including the requirement to provide significant new disclosures about the Company's leasing activities. Please refer to Note 18, "Commitments and Contingencies" for additional information about the Company's leases, including the future minimum lease payments for operating leases at March 31, 2019.

In May 2014, the FASB issued ASU No. 2014-09, Revenue from Contracts with Customers: Topic 606 (Topic 606). Topic 606 supersedes the revenue recognition requirements in Topic 605, Revenue Recognition, and requires entities to recognize revenue when control of the promised goods or services is transferred to customers at an amount that reflects the consideration to which the entity expects to be entitled to in exchange for those goods or services. The Company adopted Topic 606 as of April 1, 2018 using the modified retrospective transition method. Please refer to Note 3, "Revenue Recognition" for further details.