Summary of Significant Accounting Policies (Policies)	12 Months Ended
Mar. 31, 2018
Accounting Policies [Abstract]
Basis of presentation	The accompanying Consolidated Financial Statements include the accounts of Electro Scientific Industries, Inc. and its subsidiaries. All intercompany accounts and transactions have been eliminated. The Company’s fiscal year consists of 52 or 53 week periods ending on the Saturday nearest March 31. Accordingly, the fiscal 2018 reporting period consisted of a 52-week period ending on March 31, 2018, the fiscal 2017 reporting period consisted of a 52-week period ending on April 1, 2017 and the fiscal 2016 reporting period consisted of a 53-week period ending on April 2, 2016. All references to years or quarters relate to fiscal years or fiscal quarters unless otherwise noted.
Estimates	The preparation of Consolidated Financial Statements in conformity with accounting principles generally accepted in the United States (GAAP) requires management to make estimates and assumptions that affect the reported amounts of assets and liabilities and disclosure of commitments and contingencies at the date of the financial statements and the reported amounts of revenues and expenses during the reporting periods. Actual results may differ from those estimates. Management believes that the estimates used are reasonable. Estimates made by management include: revenue recognition; inventory valuation; valuation of investments; accrued restructuring costs; share-based compensation; income taxes, including the valuation of deferred tax assets; valuation of long-lived assets, including intangibles; goodwill and acquisition accounting.
Cash equivalents	All highly liquid investments with a maturity of 90 days or less at the date of purchase are considered to be cash equivalents.
Investments	Short-term investments reflect marketable securities that have maturities of less than one year or are subject to immediate pre-payment or call provisions. These securities consist primarily of marketable debt securities and are classified as “available-for-sale securities” and recorded at fair market value. Unrealized gains and losses on investments are recorded as a component of accumulated other comprehensive income (loss). To determine whether any existing impairment is other-than-temporary and requires recognition of an impairment loss in the results of operations, the Company evaluates its marketable securities based on the nature of the investments and the Company’s intent and ability to hold the securities until the securities are no longer in an unrealized loss position.
Accounts receviable and allowance for doubtful accounts	Trade receivables are stated at the amount the Company expects to collect and generally do not bear interest. Credit limits are established by reviewing the financial history and stability of each customer. Where appropriate, the Company obtains credit rating reports and financial statements of the customer to establish or modify credit limits. On certain foreign sales, letters of credit are obtained. The collectability of trade receivable balances is regularly evaluated based on a combination of factors such as customer reputation and credit-worthiness, past transaction history with the customer, current economic and industry trends, among other factors. If it is determined or expected that a customer will be unable to fully meet its financial obligation, such as in the case of a bankruptcy filing or other material events impacting its business, a specific allowance for bad debt is recorded to reduce the related receivable to the amount expected to be recovered.
Accrued restructuring costs
Inventories	Inventories are principally valued at standard costs, which approximate the lower of cost or net realizable value on a first-in, first-out basis. Costs utilized for inventory valuation purposes include material, labor and manufacturing overhead
Shipped systems pending acceptance	Shipped systems pending acceptance relate to systems that have been ordered and shipped to the customer, but where revenue has been deferred in accordance with the Company’s revenue recognition policy. Shipped systems pending acceptance are recognized as cost of sales once all criteria for revenue recognition have been met and revenue is recorded. Shipped systems pending acceptance are valued at standard costs, which approximate the lower of cost (first-in, first-out) or net realizable value. Costs utilized in the valuation of shipped systems pending acceptance include material, labor and manufacturing overhead and exclude costs of installation.
Property, plant and equipment	Property, plant and equipment are stated at cost less accumulated depreciation and amortization. Depreciation and amortization are recognized using the straight-line basis over the estimated useful lives of the assets. Expenditures for maintenance, repairs and minor improvements are expensed as incurred. Major improvements and additions are capitalized. When assets are sold or retired in the normal course of business, the cost and related accumulated depreciation and amortization are removed from the accounts and the resulting gain or loss is included as a component of operating expenses.
Long-lived asset impairment and amortization	Long-lived assets, principally property, plant and equipment and identifiable long-lived intangibles, are reviewed for impairment whenever events or circumstances indicate that the carrying amount of the assets may not be recoverable. The Company evaluates the recoverability of assets to be held and used by comparing the carrying amount of an asset or asset group to estimated future net undiscounted cash flows generated by the asset. If such assets are considered to be impaired, the impairment recognized is measured as the amount by which the carrying amount of the assets exceeds the fair value of the assets. The Company’s purchased patents are amortized over their estimated useful lives, generally nine to seventeen years. Other purchased intangible assets with finite useful lives are carried at cost less accumulated amortization. Amortization expense is recognized on a straight-line basis over the estimated useful lives of the intangible assets, which range from one to ten years.
Goodwill impairment
Cost method investments
Fair value of financial instruments	The carrying amounts of financial instruments, including cash equivalents, accounts receivable, accounts payable, accrued liabilities and income taxes payable approximate fair value because of the nature of the underlying transactions and short-term maturities involved. Current and non-current marketable securities are recorded at fair value which is defined under FASB ASC Topic 820 “Fair Value Measurements and Disclosures” (ASC Topic 820).
Derivative financial instruments	The Company’s primary objective for holding derivative financial instruments is to manage currency risk. The Company’s accounting policies for these instruments are based on whether they meet the Company’s criteria for designation as hedging transactions, either as cash flow or fair value hedges. A hedge of the exposure to variability in the cash flows of an asset or a liability, or of a forecasted transaction, is referred to as a cash flow hedge. A hedge of the exposure to changes in fair value of an asset or a liability, or of an unrecognized firm commitment, is referred to as a fair value hedge. The criteria for designating a derivative as a hedge include the instrument’s effectiveness in risk reduction and, in most cases, a one-to-one matching of the derivative instrument to its underlying transaction. The Company enters into foreign currency exchange contracts as cashflow hedges to offset the earnings impact relating to the variability in exchange rates on certain short-term monetary assets and liabilities denominated in non-functional currencies. The Company does not designate these foreign currency contracts as hedges. The change in fair value of these derivative instruments not designated as hedging instruments is reported each period in other income (expense), net, in the Consolidated Statements of Operations.
Revenue recognition	The Company sells a significant portion of its products to a small number of large printed circuit board (PCB), semiconductor and microelectronics manufacturers. The Company's top ten customers for 2018, 2017 and 2016 accounted for approximately 59%, 47% and 51% of total net sales, respectively. In 2018, two customers, Career Technology (Mfg.). Co. Ltd. and Top Unique Trading Co. LTD., accounted for approximately 17% and 13% of net sales, respectively. In 2017, two customers, Sumitomo Corporation and Zhen Ding Technologies, accounted for approximately 12% and 11% of net sales, respectively. One customer, Apple Inc. and its affiliates, accounted for approximately 15% of net sales in 2016. No other customer individually accounted for more than 10% of total net sales in 2018, 2017 or 2016. The Company recognizes revenue when persuasive evidence of an arrangement exists, delivery has occurred or the services have been rendered, the sales price is fixed or determinable and collection of the related receivable is reasonably assured. Title and risk of loss generally pass to the customer at the time of delivery of the product to a common carrier. Revenue is recognized upon such delivery, provided that fulfillment of acceptance criteria can be demonstrated prior to shipment. Where the acceptance criteria cannot be demonstrated prior to shipment, as in the case of substantially new products, revenue is deferred until acceptance has been received. For multiple element arrangements, the relative fair value of any undelivered elements is deferred until the elements are delivered and acceptance criteria, if any, are met. Revenues are recorded net of taxes collected which are required to be submitted to government authorities. Installation services are not essential to the functionality of the delivered equipment and installation revenue is deferred as a separate deliverable until installation is complete. Neither accrued installation costs nor the fair value of installation service revenue deferred has been material. Revenues associated with sales to customers under local contracts in Japan are generally recognized upon title transfer, which occurs upon customer acceptance. Revenues related to spare parts and consumable sales are generally recognized upon shipment. Revenues related to maintenance and service contracts are generally recognized ratably over the duration of the contracts.
Product warranty	The Company evaluates obligations related to product warranties quarterly. A standard warranty is provided on most of the Company's products over a specified period of time, generally 12 to 24 months, at no additional cost to its customers. Warranty charges are comprised of costs to service the warranty, including labor to repair the system and replacement parts for defective items, as well as other costs incidental to the repairs. Warranty charges are recorded net of any cost recoveries resulting from either successful repair of damaged parts or from warranties offered by the Company’s suppliers for defective components. Using historical data, the Company estimates average warranty cost per system or part type and records the provision for such charges as an element of cost of sales upon recognition of the related revenue. Additionally, the overall warranty accrual balance is separately analyzed using the remaining warranty periods outstanding on systems and items under warranty, and any resulting changes in estimates are recorded as an adjustment to cost of sales. If circumstances change, or if a significant change in warranty-related incidents occurs, the impact of the change in the warranty accrual could be material. Accrued product warranty is included on the Consolidated Balance Sheets as a component of accrued liabilities.
Research and development	Research and development costs, which include labor and related employee expenses, patent maintenance fees, project materials costs, development tool placement and installation costs, project subcontractors, depreciation of engineering equipment, building costs and other administration expenses, are generally expensed as incurred. Engineering materials that are expected to provide future value are included in inventories.
Comprehensive income (loss)	Comprehensive income (loss) includes net income (loss) and other comprehensive income (loss), which includes charges or credits to equity that are not the result of transactions with shareholders. Comprehensive income (loss) comprised primarily of cumulative foreign currency translation adjustments, benefit plan obligations and unrealized gains and losses on securities available for sale. The cumulative translation adjustment included in accumulated other comprehensive income (loss) at March 31, 2018 and April 1, 2017 was $0.6 million and $(1.2) million, respectively.
Earnings per share	Basic earnings per share (EPS) is computed by dividing income available to common stockholders by the weighted average number of shares outstanding during the period. Diluted EPS also considers common stock equivalents, such as stock options, stock-settled stock appreciation rights (SARs), employee stock purchase plan (ESPP) shares and restricted stock units, to the extent that they are not antidilutive.
Share-based compensation	The Company recognizes expense related to the fair value of SARs and ESPP using the Black-Scholes model to estimate the fair value of awards on the date of grant. The fair value of time-based and performance-based restricted stock units (RSUs) are measured on the grant date based on the market value of the Company's common stock. The market-based RSUs must achieve the total shareholder return (TSR) measures in order for the awards to vest, and the grant date fair value of the awards is calculated using a Monte Carlo simulation model. Except performance-based RSUs, the Company recognizes compensation expense for all share-based compensation awards, net of estimated forfeitures, on a straight-line basis over the requisite service period of the award. Expense for performance-based RSUs is recognized based on the probability of achievement of the performance criteria. The compensation cost for market-based RSUs is recognized on a straight-line basis over the related service period, even if the market condition is never satisfied.
Segment reporting	The Company complies with ASC Topic 280 Segment Reporting (ASC Topic 280). ASC Topic 280, which is based on a management approach to segment reporting, establishes requirements to report selected segment information quarterly and to report annually entity-wide disclosures about products, major customers and the geographies in which the entity holds material assets and reports revenue. An operating segment is defined as a component that engages in business activities whose operating results are reviewed by the chief operating decision maker and for which discrete financial information is available. Based on the provisions of ASC Topic 280, the Company has determined that it operates in a single segment. There is no difference between the accounting policies used for the segment compared to those used on a consolidated basis.
Employee benefit plans	The Company has an employee savings plan under the provisions of Section 401(k) of the Internal Revenue Code. During 2018, 2017 and 2016, contributions to the plan by the Company were $0.7 million, $0.8 million and $0.7 million, respectively. The Company has defined benefit retirement plans at certain of its foreign subsidiaries. The Company accounts for these plans based on the provisions of ASC Topic 715, Compensation-Retirement Benefits.

Summary of Significant Accounting Policies (Policies)

12 Months Ended

Mar. 31, 2018

The accompanying Consolidated Financial Statements include the accounts of Electro Scientific Industries, Inc. and its subsidiaries. All intercompany accounts and transactions have been eliminated.

The Company’s fiscal year consists of 52 or 53 week periods ending on the Saturday nearest March 31. Accordingly, the fiscal 2018 reporting period consisted of a 52-week period ending on March 31, 2018, the fiscal 2017 reporting period consisted of a 52-week period ending on April 1, 2017 and the fiscal 2016 reporting period consisted of a 53-week period ending on April 2, 2016. All references to years or quarters relate to fiscal years or fiscal quarters unless otherwise noted.

Estimates

The preparation of Consolidated Financial Statements in conformity with accounting principles generally accepted in the United States (GAAP) requires management to make estimates and assumptions that affect the reported amounts of assets and liabilities and disclosure of commitments and contingencies at the date of the financial statements and the reported amounts of revenues and expenses during the reporting periods. Actual results may differ from those estimates.

Management believes that the estimates used are reasonable. Estimates made by management include: revenue recognition; inventory valuation; valuation of investments; accrued restructuring costs; share-based compensation; income taxes, including the valuation of deferred tax assets; valuation of long-lived assets, including intangibles; goodwill and acquisition accounting.

Cash equivalents

All highly liquid investments with a maturity of 90 days or less at the date of purchase are considered to be cash equivalents.

Investments

Short-term investments reflect marketable securities that have maturities of less than one year or are subject to immediate pre-payment or call provisions. These securities consist primarily of marketable debt securities and are classified as “available-for-sale securities” and recorded at fair market value. Unrealized gains and losses on investments are recorded as a component of accumulated other comprehensive income (loss). To determine whether any existing impairment is other-than-temporary and requires recognition of an impairment loss in the results of operations, the Company evaluates its marketable securities based on the nature of the investments and the Company’s intent and ability to hold the securities until the securities are no longer in an unrealized loss position.

Accounts receviable and allowance for doubtful accounts

Trade receivables are stated at the amount the Company expects to collect and generally do not bear interest. Credit limits are established by reviewing the financial history and stability of each customer. Where appropriate, the Company obtains credit rating reports and financial statements of the customer to establish or modify credit limits. On certain foreign sales, letters of credit are obtained. The collectability of trade receivable balances is regularly evaluated based on a combination of factors such as customer reputation and credit-worthiness, past transaction history with the customer, current economic and industry trends, among other factors. If it is determined or expected that a customer will be unable to fully meet its financial obligation, such as in the case of a bankruptcy filing or other material events impacting its business, a specific allowance for bad debt is recorded to reduce the related receivable to the amount expected to be recovered.

Accrued restructuring costs

Inventories

Inventories are principally valued at standard costs, which approximate the lower of cost or net realizable value on a first-in, first-out basis. Costs utilized for inventory valuation purposes include material, labor and manufacturing overhead

Shipped systems pending acceptance

Shipped systems pending acceptance relate to systems that have been ordered and shipped to the customer, but where revenue has been deferred in accordance with the Company’s revenue recognition policy. Shipped systems pending acceptance are recognized as cost of sales once all criteria for revenue recognition have been met and revenue is recorded. Shipped systems pending acceptance are valued at standard costs, which approximate the lower of cost (first-in, first-out) or net realizable value. Costs utilized in the valuation of shipped systems pending acceptance include material, labor and manufacturing overhead and exclude costs of installation.

Property, plant and equipment

Property, plant and equipment are stated at cost less accumulated depreciation and amortization. Depreciation and amortization are recognized using the straight-line basis over the estimated useful lives of the assets. Expenditures for maintenance, repairs and minor improvements are expensed as incurred. Major improvements and additions are capitalized. When assets are sold or retired in the normal course of business, the cost and related accumulated depreciation and amortization are removed from the accounts and the resulting gain or loss is included as a component of operating expenses.

Long-lived asset impairment and amortization

Long-lived assets, principally property, plant and equipment and identifiable long-lived intangibles, are reviewed for impairment whenever events or circumstances indicate that the carrying amount of the assets may not be recoverable. The Company evaluates the recoverability of assets to be held and used by comparing the carrying amount of an asset or asset group to estimated future net undiscounted cash flows generated by the asset. If such assets are considered to be impaired, the impairment recognized is measured as the amount by which the carrying amount of the assets exceeds the fair value of the assets.

The Company’s purchased patents are amortized over their estimated useful lives, generally nine to seventeen years.

Other purchased intangible assets with finite useful lives are carried at cost less accumulated amortization. Amortization expense is recognized on a straight-line basis over the estimated useful lives of the intangible assets, which range from one to ten years.

Goodwill impairment

Cost method investments

Fair value of financial instruments

The carrying amounts of financial instruments, including cash equivalents, accounts receivable, accounts payable, accrued liabilities and income taxes payable approximate fair value because of the nature of the underlying transactions and short-term maturities involved. Current and non-current marketable securities are recorded at fair value which is defined under FASB ASC Topic 820 “Fair Value Measurements and Disclosures” (ASC Topic 820).

Derivative financial instruments

The Company’s primary objective for holding derivative financial instruments is to manage currency risk. The Company’s accounting policies for these instruments are based on whether they meet the Company’s criteria for designation as hedging transactions, either as cash flow or fair value hedges. A hedge of the exposure to variability in the cash flows of an asset or a liability, or of a forecasted transaction, is referred to as a cash flow hedge. A hedge of the exposure to changes in fair value of an asset or a liability, or of an unrecognized firm commitment, is referred to as a fair value hedge. The criteria for designating a derivative as a hedge include the instrument’s effectiveness in risk reduction and, in most cases, a one-to-one matching of the derivative instrument to its underlying transaction. The Company enters into foreign currency exchange contracts as cashflow hedges to offset the earnings impact relating to the variability in exchange rates on certain short-term monetary assets and liabilities denominated in non-functional currencies. The Company does not designate these foreign currency contracts as hedges. The change in fair value of these derivative instruments not designated as hedging instruments is reported each period in other income (expense), net, in the Consolidated Statements of Operations.

Revenue recognition

The Company sells a significant portion of its products to a small number of large printed circuit board (PCB), semiconductor and microelectronics manufacturers. The Company's top ten customers for 2018, 2017 and 2016 accounted for approximately 59%, 47% and 51% of total net sales, respectively. In 2018, two customers, Career Technology (Mfg.). Co. Ltd. and Top Unique Trading Co. LTD., accounted for approximately 17% and 13% of net sales, respectively. In 2017, two customers, Sumitomo Corporation and Zhen Ding Technologies, accounted for approximately 12% and 11% of net sales, respectively. One customer, Apple Inc. and its affiliates, accounted for approximately 15% of net sales in 2016. No other customer individually accounted for more than 10% of total net sales in 2018, 2017 or 2016.

The Company recognizes revenue when persuasive evidence of an arrangement exists, delivery has occurred or the services have been rendered, the sales price is fixed or determinable and collection of the related receivable is reasonably assured. Title and risk of loss generally pass to the customer at the time of delivery of the product to a common carrier. Revenue is recognized upon such delivery, provided that fulfillment of acceptance criteria can be demonstrated prior to shipment. Where the acceptance criteria cannot be demonstrated prior to shipment, as in the case of substantially new products, revenue is deferred until acceptance has been received. For multiple element arrangements, the relative fair value of any undelivered elements is deferred until the elements are delivered and acceptance criteria, if any, are met. Revenues are recorded net of taxes collected which are required to be submitted to government authorities. Installation services are not essential to the functionality of the delivered equipment and installation revenue is deferred as a separate deliverable until installation is complete. Neither accrued installation costs nor the fair value of installation service revenue deferred has been material.

Revenues associated with sales to customers under local contracts in Japan are generally recognized upon title transfer, which occurs upon customer acceptance. Revenues related to spare parts and consumable sales are generally recognized upon shipment. Revenues related to maintenance and service contracts are generally recognized ratably over the duration of the contracts.

Product warranty

The Company evaluates obligations related to product warranties quarterly. A standard warranty is provided on most of the Company's products over a specified period of time, generally 12 to 24 months, at no additional cost to its customers. Warranty charges are comprised of costs to service the warranty, including labor to repair the system and replacement parts for defective items, as well as other costs incidental to the repairs. Warranty charges are recorded net of any cost recoveries resulting from either successful repair of damaged parts or from warranties offered by the Company’s suppliers for defective components. Using historical data, the Company estimates average warranty cost per system or part type and records the provision for such charges as an element of cost of sales upon recognition of the related revenue. Additionally, the overall warranty accrual balance is separately analyzed using the remaining warranty periods outstanding on systems and items under warranty, and any resulting changes in estimates are recorded as an adjustment to cost of sales. If circumstances change, or if a significant change in warranty-related incidents occurs, the impact of the change in the warranty accrual could be material. Accrued product warranty is included on the Consolidated Balance Sheets as a component of accrued liabilities.

Research and development

Research and development costs, which include labor and related employee expenses, patent maintenance fees, project materials costs, development tool placement and installation costs, project subcontractors, depreciation of engineering equipment, building costs and other administration expenses, are generally expensed as incurred. Engineering materials that are expected to provide future value are included in inventories.

Comprehensive income (loss)

Comprehensive income (loss) includes net income (loss) and other comprehensive income (loss), which includes charges or credits to equity that are not the result of transactions with shareholders. Comprehensive income (loss) comprised primarily of cumulative foreign currency translation adjustments, benefit plan obligations and unrealized gains and losses on securities available for sale. The cumulative translation adjustment included in accumulated other comprehensive income (loss) at March 31, 2018 and April 1, 2017 was $0.6 million and $(1.2) million, respectively.

Earnings per share

Basic earnings per share (EPS) is computed by dividing income available to common stockholders by the weighted average number of shares outstanding during the period. Diluted EPS also considers common stock equivalents, such as stock options, stock-settled stock appreciation rights (SARs), employee stock purchase plan (ESPP) shares and restricted stock units, to the extent that they are not antidilutive.

Share-based compensation

The Company recognizes expense related to the fair value of SARs and ESPP using the Black-Scholes model to estimate the fair value of awards on the date of grant. The fair value of time-based and performance-based restricted stock units (RSUs) are measured on the grant date based on the market value of the Company's common stock. The market-based RSUs must achieve the total shareholder return (TSR) measures in order for the awards to vest, and the grant date fair value of the awards is calculated using a Monte Carlo simulation model.

Except performance-based RSUs, the Company recognizes compensation expense for all share-based compensation awards, net of estimated forfeitures, on a straight-line basis over the requisite service period of the award. Expense for performance-based RSUs is recognized based on the probability of achievement of the performance criteria. The compensation cost for market-based RSUs is recognized on a straight-line basis over the related service period, even if the market condition is never satisfied.

Segment reporting

The Company complies with ASC Topic 280 Segment Reporting (ASC Topic 280). ASC Topic 280, which is based on a management approach to segment reporting, establishes requirements to report selected segment information quarterly and to report annually entity-wide disclosures about products, major customers and the geographies in which the entity holds material assets and reports revenue. An operating segment is defined as a component that engages in business activities whose operating results are reviewed by the chief operating decision maker and for which discrete financial information is available. Based on the provisions of ASC Topic 280, the Company has determined that it operates in a single segment. There is no difference between the accounting policies used for the segment compared to those used on a consolidated basis.

Employee benefit plans

The Company has an employee savings plan under the provisions of Section 401(k) of the Internal Revenue Code. During 2018, 2017 and 2016, contributions to the plan by the Company were $0.7 million, $0.8 million and $0.7 million, respectively.

The Company has defined benefit retirement plans at certain of its foreign subsidiaries. The Company accounts for these plans based on the provisions of ASC Topic 715, Compensation-Retirement Benefits.