Basis of Presentation and Summary of Significant Accounting Policies	9 Months Ended
Mar. 30, 2018
Accounting Policies [Abstract]
Basis of Presentation and Summary of Significant Accounting Policies	Basis of Presentation and Summary of Significant Accounting Policies Organization Seagate Technology plc (the “Company”) is a leading provider of data storage technology and solutions. Its principal products are hard disk drives, commonly referred to as disk drives, hard drives or HDDs. In addition to HDDs, the Company produces a broad range of data storage products including solid state drives (“SSD”) and their related controllers, solid state hybrid drives (“SSHD”) and storage subsystems. Hard disk drives are devices that store digitally encoded data on rapidly rotating disks with magnetic surfaces. Disk drives continue to be the primary medium of mass data storage due to their performance attributes, high quality and cost effectiveness. Complementing existing data center storage architecture, solid-state storage devices use integrated circuit assemblies as memory to store data with most SSDs using NAND-based flash memory. In addition to HDDs and SSDs, SSHDs combine the features of SSDs and HDDs in the same unit, containing a large hard disk drive and an SSD cache to improve performance of frequently accessed data. The Company’s products are designed for mission critical and nearline applications in enterprise servers and storage systems; edge compute / client compute applications, where its products are designed primarily for desktop and mobile computing; and edge non-compute / client non-compute applications, where its products are designed for a wide variety of end user devices such as portable external storage systems, surveillance systems, network-attached storage (“NAS”), digital video recorders (“DVRs”) and gaming consoles. The Company’s cloud systems and solutions extend innovation from the device into the information infrastructure, onsite and in the cloud. Its portfolio includes modular original equipment manufacturers (“OEM”) storage systems and scale-out storage servers. Basis of Presentation and Consolidation The unaudited condensed consolidated financial statements include the accounts of the Company and all its wholly-owned and majority-owned subsidiaries, after elimination of intercompany transactions and balances. The preparation of financial statements in accordance with U.S. generally accepted accounting principles requires management to make estimates and assumptions that affect the amounts reported in the Company’s condensed consolidated financial statements and accompanying notes. Actual results could differ materially from those estimates. The methods, estimates and judgments the Company uses in applying its most critical accounting policies have a significant impact on the results the Company reports in its condensed consolidated financial statements. The condensed consolidated financial statements reflect, in the opinion of management, all material adjustments necessary to present fairly the condensed consolidated financial position, results of operations, comprehensive income, cash flows and shareholders’ equity for the periods presented. Such adjustments are of a normal and recurring nature. Certain prior period amounts in the condensed consolidated financial statements and notes to the condensed consolidated financial statements have been reclassified to conform to the current period's presentation. The Company’s consolidated financial statements for the fiscal year ended June 30, 2017, are included in its Annual Report on Form 10-K as filed with the United States Securities and Exchange Commission (“SEC”) on August 4, 2017. The Company believes that the disclosures included in the unaudited condensed consolidated financial statements, when read in conjunction with its consolidated financial statements as of June 30, 2017, and the notes thereto, are adequate to make the information presented not misleading. The results of operations for the three and nine months ended March 30, 2018 are not necessarily indicative of the results of operations to be expected for any subsequent interim period or for the Company’s fiscal year ending June 29, 2018. The Company operates and reports financial results on a fiscal year of 52 or 53 weeks ending on the Friday closest to June 30. Both the three and nine months ended March 30, 2018 and the three and nine months ended March 31, 2017 consisted of 13 weeks and 39 weeks, respectively. Fiscal year 2018, which ends on June 29, 2018, and fiscal year 2017, which ended on June 30, 2017, are both comprised of 52 weeks. The fiscal quarters ended March 30, 2018, December 29, 2017, and March 31, 2017, are also referred to herein as the “March 2018 quarter”, the “December 2017 quarter”, and the “March 2017 quarter”, respectively. Summary of Significant Accounting Policies There have been no significant changes in the Company's significant accounting policies. Please refer to Note 1 of “Financial Statements and Supplementary Data” contained in Part II, Item 8 of the Company’s Annual Report on Form 10-K for the fiscal year ended June 30, 2017, as filed with the SEC on August 4, 2017 for a discussion of the Company’s significant accounting policies. Recently Issued Accounting Pronouncements In May 2014, August 2015, April 2016, May 2016 and December 2016, the Financial Accounting Standards Board (“FASB”) issued Accounting Standard Update ("ASU") 2014-09 (ASC Topic 606), Revenue from Contracts with Customers, ASU 2015-14 (ASC Topic 606) Revenue from Contracts with Customers, Deferral of the Effective Date, ASU 2016-10 (ASC Topic 606) Revenue from Contracts with Customers, Identifying Performance Obligations and Licensing, ASU 2016-12 (ASC Topic 606) Revenue from Contracts with Customers, Narrow-Scope Improvements and Practical Expedients, and ASU 2016-20 (ASC Topic 606) Technical Corrections and Improvements to Topic 606, Revenue from Contracts with Customers, respectively. ASC Topic 606 outlines a single comprehensive model for entities to use in accounting for revenue arising from contracts with customers and supersedes most current revenue recognition guidance, including industry-specific guidance. It also requires entities to disclose both quantitative and qualitative information that enable financial statements users to understand the nature, amount, timing, and uncertainty of revenue and cash flows arising from contracts with customers. The Company is required to adopt the guidance in the first quarter of fiscal year 2019. This standard may be applied retrospectively to all prior periods presented, or retrospectively with a cumulative adjustment to retained earnings in the year of adoption (“modified retrospective transition approach”). Based on its assessment, the Company plans to adopt the new revenue standard in the first quarter of fiscal year 2019, utilizing the modified retrospective method of transition. While management has not yet completed its assessment of the impact of adopting this new standard on the Company’s consolidated financial statements, the Company expects the adoption of the new standard will result in the recognition of revenue generally upon shipment (sell-in basis) for sales of products to certain direct retail customers and customers in certain indirect retail channels which are currently being recognized on a sell-through basis. Accordingly, the Company will need to estimate variable consideration (e.g. rebates) related to customer incentives on these arrangements. These changes are not expected to have a material impact on the Company’s condensed consolidated financial statements. In January 2016, the FASB issued ASU 2016-01 (ASC Subtopic 825-10), Financial Instruments—Overall Recognition and Measurement of Financial Assets and Financial Liabilities, as amended by ASU 2018-03, Financial Instruments—Overall: Technical Correction and Improvements, issued in February 2018. The amendments in these ASUs require entities to measure all investments in equity securities at fair value with changes recognized through net income. This requirement does not apply to investments that qualify for the equity method of accounting, to those that result in consolidation of the investee, or for which the entity meets a practicability exception to fair value measurement. Additionally, the amendments eliminate certain disclosure requirements related to financial instruments measured at amortized cost and add disclosures related to the measurement categories of financial assets and financial liabilities. The Company is required to adopt the guidance in the first quarter of fiscal year 2019. Early adoption is permitted for only certain portions of the ASU. The Company expects to elect the measurement alternative for measurement of equity investments, defined as cost, less impairments, if any, plus or minus changes resulting from observable price changes in orderly transactions for an identical or similar investment in the same issuer (the "Price Changes") until the equity investments' fair value becomes readily determinable. The amount of the impact to equity investments will depend on any Price Changes observed after adoption in the first quarter of fiscal year 2019. In February 2016, the FASB issued ASU 2016-02 (ASC Topic 842), Leases. This ASU amends a number of aspects of lease accounting, including requiring lessees to recognize operating leases with a term greater than one year on their balance sheet as a right-of-use asset and corresponding lease liability, measured at the present value of the lease payments. The Company is required to adopt this guidance in the first quarter of fiscal year 2020. Early adoption is permitted. The Company is in the process of assessing the impact of this ASU on its condensed consolidated financial statements. In June 2016, the FASB issued ASU 2016-13 (ASC Topic 326), Financial Instruments - Credit Losses: Measurement of Credit Losses on Financial Instruments. This ASU amends the requirement on the measurement and recognition of expected credit losses for financial assets held. The Company is required to adopt this guidance in the first quarter of fiscal year 2021. Early adoption in the first quarter of fiscal year 2020 is permitted. The Company is in the process of assessing the impact of this ASU on its condensed consolidated financial statements. In January 2017, the FASB issued ASU 2017-01 (ASC Topic 805), Business Combination: Clarifying the Definition of a Business. The amendments in this ASU change the definition of a business to assist with evaluating when a set of transferred assets and activities is a business. The Company plans to adopt the guidance in the first quarter of fiscal year 2019. Early adoption is permitted. The Company is in the process of assessing the impact of this ASU on its condensed consolidated financial statements. In May 2017, the FASB issued ASU 2017-09 (ASC Topic 718), Stock Compensation: Scope of Modification Accounting. The amendments in this ASU provide guidance about which changes to the terms or conditions of a share-based payment award require an entity to apply modification accounting. The Company plans to adopt the guidance in the first quarter of fiscal year 2019. The Company is in the process of assessing the impact of this ASU on its condensed consolidated financial statements. In August 2017, the FASB issued ASU 2017-12 (ASC Topic 815), Derivatives and Hedging: Targeted Improvements to Accounting for Hedging Activities. The amendments in this ASU were issued to simplify existing guidance in order to allow companies to more accurately present the economic effects of risk management activities in the financial statements. The amended guidance will eliminate the separate measurement and presentation of hedge ineffectiveness. The Company is required to adopt the guidance in the first quarter of fiscal year 2020. Early adoption is permitted. The Company is in the process of assessing the impact of this ASU on its condensed consolidated financial statements. In February 2018, the FASB issued ASU 2018-02 (ASC Topic 220), Income Statement—Reporting Comprehensive Income: Reclassification of Certain Tax Effects from Accumulated Other Comprehensive Income. This ASU was issued following the enactment of the U.S. Tax Cuts and Jobs Act of 2017 (the "Act") and permits entities to elect a reclassification from accumulated other comprehensive income to retained earnings for stranded tax effects resulting from the Act. The Company is required to adopt the guidance in the first quarter of fiscal year 2020. Early adoption is permitted. The Company is in the process of assessing the impact of this ASU on its condensed consolidated financial statements. Recently Adopted Accounting Pronouncements In July 2015, the FASB issued ASU 2015-11 (ASC Topic 330), Inventory: Simplifying the Measurement of Inventory. The amendments in this ASU require inventory measurement at the lower of cost and net realizable value. This ASU became effective and was adopted by the Company in the September 2017 quarter on a prospective basis. The adoption of this guidance had no material impact on the Company’s condensed consolidated financial statements and disclosures. In March 2016, the FASB issued ASU 2016-09 (ASC Topic 718), Stock Compensation—Improvements to Employee Share-Based Payment Accounting. The amendments in this ASU are intended to simplify several areas of accounting for share-based compensation arrangements, including the income tax consequences, classification on the consolidated statement of cash flows and treatment of forfeitures. This ASU became effective and was adopted by the Company in the September 2017 quarter. Upon adoption, excess tax benefits or deficiencies from share-based award activity are reflected in the condensed consolidated statements of operations as a component of the provision for income taxes, whereas they previously were recognized in the Shareholder's equity in the condensed consolidated balance sheets. The Company also elected to continue to account for share-based compensation expense net of estimated forfeitures. The adoption of this ASU resulted in an increase in deferred tax assets relating to net operating losses of approximately $0.6 billion, offset by an equivalent increase in the valuation allowance with no impact to retained earnings. The adoption of this guidance had no material impact on the Company’s condensed consolidated financial statements and disclosures. In October 2016, the FASB issued ASU 2016-16 (ASC Topic 740), Income Taxes: Intra-Entity Transfers of Assets Other Than Inventory. The amendments in this ASU require the recognition of the income tax consequences for intra-entity transfers of assets other than inventory when the transfer occurs. The Company elected to adopt this ASU in the September 2017 quarter on a modified retrospective basis with no material impact on the Company's condensed consolidated financial statements and disclosures.

Basis of Presentation and Summary of Significant Accounting Policies

Organization

Seagate Technology plc (the “Company”) is a leading provider of data storage technology and solutions. Its principal products are hard disk drives, commonly referred to as disk drives, hard drives or HDDs. In addition to HDDs, the Company produces a broad range of data storage products including solid state drives (“SSD”) and their related controllers, solid state hybrid drives (“SSHD”) and storage subsystems.

Hard disk drives are devices that store digitally encoded data on rapidly rotating disks with magnetic surfaces. Disk drives continue to be the primary medium of mass data storage due to their performance attributes, high quality and cost effectiveness. Complementing existing data center storage architecture, solid-state storage devices use integrated circuit assemblies as memory to store data with most SSDs using NAND-based flash memory. In addition to HDDs and SSDs, SSHDs combine the features of SSDs and HDDs in the same unit, containing a large hard disk drive and an SSD cache to improve performance of frequently accessed data.

The Company’s products are designed for mission critical and nearline applications in enterprise servers and storage systems; edge compute / client compute applications, where its products are designed primarily for desktop and mobile computing; and edge non-compute / client non-compute applications, where its products are designed for a wide variety of end user devices such as portable external storage systems, surveillance systems, network-attached storage (“NAS”), digital video recorders (“DVRs”) and gaming consoles.

The Company’s cloud systems and solutions extend innovation from the device into the information infrastructure, onsite and in the cloud. Its portfolio includes modular original equipment manufacturers (“OEM”) storage systems and scale-out storage servers.

Basis of Presentation and Consolidation

The unaudited condensed consolidated financial statements include the accounts of the Company and all its wholly-owned and majority-owned subsidiaries, after elimination of intercompany transactions and balances.

The preparation of financial statements in accordance with U.S. generally accepted accounting principles requires management to make estimates and assumptions that affect the amounts reported in the Company’s condensed consolidated financial statements and accompanying notes. Actual results could differ materially from those estimates. The methods, estimates and judgments the Company uses in applying its most critical accounting policies have a significant impact on the results the Company reports in its condensed consolidated financial statements. The condensed consolidated financial statements reflect, in the opinion of management, all material adjustments necessary to present fairly the condensed consolidated financial position, results of operations, comprehensive income, cash flows and shareholders’ equity for the periods presented. Such adjustments are of a normal and recurring nature. Certain prior period amounts in the condensed consolidated financial statements and notes to the condensed consolidated financial statements have been reclassified to conform to the current period's presentation.

The Company’s consolidated financial statements for the fiscal year ended June 30, 2017, are included in its Annual Report on Form 10-K as filed with the United States Securities and Exchange Commission (“SEC”) on August 4, 2017. The Company believes that the disclosures included in the unaudited condensed consolidated financial statements, when read in conjunction with its consolidated financial statements as of June 30, 2017, and the notes thereto, are adequate to make the information presented not misleading.

The results of operations for the three and nine months ended March 30, 2018 are not necessarily indicative of the results of operations to be expected for any subsequent interim period or for the Company’s fiscal year ending June 29, 2018. The Company operates and reports financial results on a fiscal year of 52 or 53 weeks ending on the Friday closest to June 30. Both the three and nine months ended March 30, 2018 and the three and nine months ended March 31, 2017 consisted of 13 weeks and 39 weeks, respectively. Fiscal year 2018, which ends on June 29, 2018, and fiscal year 2017, which ended on June 30, 2017, are both comprised of 52 weeks. The fiscal quarters ended March 30, 2018, December 29, 2017, and March 31, 2017, are also referred to herein as the “March 2018 quarter”, the “December 2017 quarter”, and the “March 2017 quarter”, respectively.

Summary of Significant Accounting Policies

There have been no significant changes in the Company's significant accounting policies. Please refer to Note 1 of “Financial Statements and Supplementary Data” contained in Part II, Item 8 of the Company’s Annual Report on Form 10-K for the fiscal year ended June 30, 2017, as filed with the SEC on August 4, 2017 for a discussion of the Company’s significant accounting policies.

Recently Issued Accounting Pronouncements

In May 2014, August 2015, April 2016, May 2016 and December 2016, the Financial Accounting Standards Board (“FASB”) issued Accounting Standard Update ("ASU") 2014-09 (ASC Topic 606), Revenue from Contracts with Customers, ASU 2015-14 (ASC Topic 606) Revenue from Contracts with Customers, Deferral of the Effective Date, ASU 2016-10 (ASC Topic 606) Revenue from Contracts with Customers, Identifying Performance Obligations and Licensing, ASU 2016-12 (ASC Topic 606) Revenue from Contracts with Customers, Narrow-Scope Improvements and Practical Expedients, and ASU 2016-20 (ASC Topic 606) Technical Corrections and Improvements to Topic 606, Revenue from Contracts with Customers, respectively. ASC Topic 606 outlines a single comprehensive model for entities to use in accounting for revenue arising from contracts with customers and supersedes most current revenue recognition guidance, including industry-specific guidance. It also requires entities to disclose both quantitative and qualitative information that enable financial statements users to understand the nature, amount, timing, and uncertainty of revenue and cash flows arising from contracts with customers. The Company is required to adopt the guidance in the first quarter of fiscal year 2019. This standard may be applied retrospectively to all prior periods presented, or retrospectively with a cumulative adjustment to retained earnings in the year of adoption (“modified retrospective transition approach”). Based on its assessment, the Company plans to adopt the new revenue standard in the first quarter of fiscal year 2019, utilizing the modified retrospective method of transition. While management has not yet completed its assessment of the impact of adopting this new standard on the Company’s consolidated financial statements, the Company expects the adoption of the new standard will result in the recognition of revenue generally upon shipment (sell-in basis) for sales of products to certain direct retail customers and customers in certain indirect retail channels which are currently being recognized on a sell-through basis. Accordingly, the Company will need to estimate variable consideration (e.g. rebates) related to customer incentives on these arrangements. These changes are not expected to have a material impact on the Company’s condensed consolidated financial statements.

In January 2016, the FASB issued ASU 2016-01 (ASC Subtopic 825-10), Financial Instruments—Overall Recognition and Measurement of Financial Assets and Financial Liabilities, as amended by ASU 2018-03, Financial Instruments—Overall: Technical Correction and Improvements, issued in February 2018. The amendments in these ASUs require entities to measure all investments in equity securities at fair value with changes recognized through net income. This requirement does not apply to investments that qualify for the equity method of accounting, to those that result in consolidation of the investee, or for which the entity meets a practicability exception to fair value measurement. Additionally, the amendments eliminate certain disclosure requirements related to financial instruments measured at amortized cost and add disclosures related to the measurement categories of financial assets and financial liabilities. The Company is required to adopt the guidance in the first quarter of fiscal year 2019. Early adoption is permitted for only certain portions of the ASU. The Company expects to elect the measurement alternative for measurement of equity investments, defined as cost, less impairments, if any, plus or minus changes resulting from observable price changes in orderly transactions for an identical or similar investment in the same issuer (the "Price Changes") until the equity investments' fair value becomes readily determinable. The amount of the impact to equity investments will depend on any Price Changes observed after adoption in the first quarter of fiscal year 2019.

In February 2016, the FASB issued ASU 2016-02 (ASC Topic 842), Leases. This ASU amends a number of aspects of lease accounting, including requiring lessees to recognize operating leases with a term greater than one year on their balance sheet as a right-of-use asset and corresponding lease liability, measured at the present value of the lease payments. The Company is required to adopt this guidance in the first quarter of fiscal year 2020. Early adoption is permitted. The Company is in the process of assessing the impact of this ASU on its condensed consolidated financial statements.

In June 2016, the FASB issued ASU 2016-13 (ASC Topic 326), Financial Instruments - Credit Losses: Measurement of Credit Losses on Financial Instruments. This ASU amends the requirement on the measurement and recognition of expected credit losses for financial assets held. The Company is required to adopt this guidance in the first quarter of fiscal year 2021. Early adoption in the first quarter of fiscal year 2020 is permitted. The Company is in the process of assessing the impact of this ASU on its condensed consolidated financial statements.

In January 2017, the FASB issued ASU 2017-01 (ASC Topic 805), Business Combination: Clarifying the Definition of a Business. The amendments in this ASU change the definition of a business to assist with evaluating when a set of transferred assets and activities is a business. The Company plans to adopt the guidance in the first quarter of fiscal year 2019. Early adoption is permitted. The Company is in the process of assessing the impact of this ASU on its condensed consolidated financial statements.

In May 2017, the FASB issued ASU 2017-09 (ASC Topic 718), Stock Compensation: Scope of Modification Accounting. The amendments in this ASU provide guidance about which changes to the terms or conditions of a share-based payment award require an entity to apply modification accounting. The Company plans to adopt the guidance in the first quarter of fiscal year 2019. The Company is in the process of assessing the impact of this ASU on its condensed consolidated financial statements.

In August 2017, the FASB issued ASU 2017-12 (ASC Topic 815), Derivatives and Hedging: Targeted Improvements to Accounting for Hedging Activities. The amendments in this ASU were issued to simplify existing guidance in order to allow companies to more accurately present the economic effects of risk management activities in the financial statements. The amended guidance will eliminate the separate measurement and presentation of hedge ineffectiveness. The Company is required to adopt the guidance in the first quarter of fiscal year 2020. Early adoption is permitted. The Company is in the process of assessing the impact of this ASU on its condensed consolidated financial statements.

In February 2018, the FASB issued ASU 2018-02 (ASC Topic 220), Income Statement—Reporting Comprehensive Income: Reclassification of Certain Tax Effects from Accumulated Other Comprehensive Income. This ASU was issued following the enactment of the U.S. Tax Cuts and Jobs Act of 2017 (the "Act") and permits entities to elect a reclassification from accumulated other comprehensive income to retained earnings for stranded tax effects resulting from the Act. The Company is required to adopt the guidance in the first quarter of fiscal year 2020. Early adoption is permitted. The Company is in the process of assessing the impact of this ASU on its condensed consolidated financial statements.

Recently Adopted Accounting Pronouncements

In July 2015, the FASB issued ASU 2015-11 (ASC Topic 330), Inventory: Simplifying the Measurement of Inventory. The amendments in this ASU require inventory measurement at the lower of cost and net realizable value. This ASU became effective and was adopted by the Company in the September 2017 quarter on a prospective basis. The adoption of this guidance had no material impact on the Company’s condensed consolidated financial statements and disclosures.

In March 2016, the FASB issued ASU 2016-09 (ASC Topic 718), Stock Compensation—Improvements to Employee Share-Based Payment Accounting. The amendments in this ASU are intended to simplify several areas of accounting for share-based compensation arrangements, including the income tax consequences, classification on the consolidated statement of cash flows and treatment of forfeitures. This ASU became effective and was adopted by the Company in the September 2017 quarter. Upon adoption, excess tax benefits or deficiencies from share-based award activity are reflected in the condensed consolidated statements of operations as a component of the provision for income taxes, whereas they previously were recognized in the Shareholder's equity in the condensed consolidated balance sheets. The Company also elected to continue to account for share-based compensation expense net of estimated forfeitures. The adoption of this ASU resulted in an increase in deferred tax assets relating to net operating losses of approximately $0.6 billion, offset by an equivalent increase in the valuation allowance with no impact to retained earnings. The adoption of this guidance had no material impact on the Company’s condensed consolidated financial statements and disclosures.

In October 2016, the FASB issued ASU 2016-16 (ASC Topic 740), Income Taxes: Intra-Entity Transfers of Assets Other Than Inventory. The amendments in this ASU require the recognition of the income tax consequences for intra-entity transfers of assets other than inventory when the transfer occurs. The Company elected to adopt this ASU in the September 2017 quarter on a modified retrospective basis with no material impact on the Company's condensed consolidated financial statements and disclosures.