Summary of Significant Accounting Policies	9 Months Ended
Sep. 30, 2016
Accounting Policies [Abstract]
Significant Accounting Policies [Text Block]	SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES Basis of Presentation The accompanying unaudited Condensed Consolidated Financial Statements have been prepared in accordance with U.S. generally accepted accounting principles for interim financial information. The financial statements include all adjustments, consisting of normal recurring adjustments that the management of Gilead Sciences, Inc. (Gilead, we or us) believes are necessary for a fair presentation of the periods presented. These interim financial results are not necessarily indicative of results expected for the full fiscal year or for any subsequent interim period. The accompanying Condensed Consolidated Financial Statements include the accounts of Gilead, our wholly-owned subsidiaries and certain variable interest entities for which we are the primary beneficiary. All intercompany transactions have been eliminated. For consolidated entities where we own or are exposed to less than 100% of the economics, we record net income or loss attributable to noncontrolling interest in our Condensed Consolidated Statements of Income equal to the percentage of the economic or ownership interest retained in such entities by the respective noncontrolling parties. We assess whether we are the primary beneficiary of a variable interest entity (VIE) at the inception of the arrangement and at each reporting date. This assessment is based on our power to direct the activities of the VIE that most significantly impact the VIE’s economic performance and our obligation to absorb losses or the right to receive benefits from the VIE that could potentially be significant to the VIE. As of September 30, 2016, the only material VIE was our joint venture with Bristol-Myers Squibb Company (BMS) which is described in Note 8, Collaborative Arrangements. The accompanying Condensed Consolidated Financial Statements and related Notes to Condensed Consolidated Financial Statements should be read in conjunction with the audited Consolidated Financial Statements and the related notes thereto for the year ended December 31, 2015, included in our Annual Report on Form 10-K filed with the U.S. Securities and Exchange Commission. Significant Accounting Policies, Estimates and Judgments The preparation of these Condensed Consolidated Financial Statements requires us to make estimates and judgments that affect the reported amounts of assets, liabilities, revenues and expenses and related disclosures. On an ongoing basis, we evaluate our significant accounting policies and estimates. We base our estimates on historical experience and on various market-specific and other relevant assumptions that we believe to be reasonable under the circumstances, the results of which form the basis for making judgments about the carrying values of assets and liabilities that are not readily apparent from other sources. Estimates are assessed each period and updated to reflect current information. Actual results may differ significantly from these estimates. Concentrations of Risk We are subject to credit risk from our portfolio of cash, cash equivalents and marketable securities. Under our investment policy, we limit amounts invested in such securities by credit rating, maturity, industry group, investment type and issuer, except for securities issued by the U.S. government. We are not exposed to any significant concentrations of credit risk from these financial instruments. The goals of our investment policy, in order of priority, are as follows: safety and preservation of principal and diversification of risk; liquidity of investments sufficient to meet cash flow requirements; and a competitive after-tax rate of return. We are also subject to credit risk from our accounts receivable related to our product sales. The majority of our trade accounts receivable arises from product sales in the United States, Europe and Japan. As of September 30, 2016, our accounts receivable in Southern Europe, specifically Greece, Italy, Portugal and Spain, totaled approximately $566 million, of which $132 million were greater than 120 days past due, including $62 million greater than 365 days past due. To date, we have not experienced significant losses with respect to the collection of our accounts receivable. We believe that our allowance for doubtful accounts was adequate at September 30, 2016. Recent Accounting Pronouncements In May 2014, the Financial Accounting Standards Board (FASB) issued Accounting Standard Update No. 2014-09 (ASU 2014-09) “Revenue from Contracts with Customers.” The standard’s core principle is that a reporting entity will recognize revenue when it transfers promised goods or services to customers in an amount that reflects the consideration to which the entity expects to be entitled in exchange for those goods or services. The standard will become effective for us beginning in the first quarter of 2018. Early adoption is permitted in 2017. Entities have the option of using either a full retrospective or a modified retrospective approach to adopt this new guidance. The FASB issued supplemental adoption guidance and clarification to ASU 2014-09 in March 2016, April 2016 and May 2016 within ASU 2016-08 “Revenue from Contracts with Customers: Principal vs. Agent Considerations,” ASU 2016-10 “Revenue from Contracts with Customers: Identifying Performance Obligations and Licensing” and ASU 2016-12 “Revenue from Contracts with Customers: Narrow-Scope Improvements and Practical Expedients,” respectively. We are evaluating the impact of the adoption of these standards on our Condensed Consolidated Financial Statements. In November 2015, the FASB issued Accounting Standard Update No. 2015-17 (ASU 2015-17) “Balance Sheet Classification of Deferred Taxes.” ASU 2015-17 requires that deferred tax liabilities and assets be classified as noncurrent on the balance sheet. Previous guidance required deferred tax liabilities and assets to be separated into current and noncurrent amounts on the balance sheet. The guidance will become effective for us beginning in the first quarter of 2017 and may be applied either prospectively or retrospectively. Early adoption is permitted. We plan to adopt the guidance in the first quarter of 2017 on a retrospective basis and will reclassify current deferred tax amounts on our Condensed Consolidated Balance Sheets as noncurrent. In January 2016, the FASB issued Accounting Standard Update No. 2016-01(ASU 2016-01) “Recognition and Measurement of Financial Assets and Financial Liabilities.” ASU 2016-01 changes accounting for equity investments, financial liabilities under the fair value option and the presentation and disclosure requirements for financial instruments. In addition, it clarified guidance related to the valuation allowance assessment when recognizing deferred tax assets resulting from unrealized losses on available-for-sale debt securities. The guidance will become effective for us beginning in the first quarter of 2018 and must be adopted using a modified retrospective approach, with certain exceptions. Early adoption is permitted for certain provisions. We are evaluating the impact of the adoption of this standard on our Condensed Consolidated Financial Statements. In February 2016, the FASB issued Accounting Standard Update No. 2016-02 (ASU 2016-02) “Leases.” ASU 2016-02 amends a number of aspects of lease accounting, including requiring lessees to recognize almost all leases with a term greater than one year as a right-of-use asset and corresponding liability, measured at the present value of the lease payments. The guidance will become effective for us beginning in the first quarter of 2019 and is required to be adopted using a modified retrospective approach. Early adoption is permitted. We are evaluating the impact of the adoption of this standard on our Condensed Consolidated Financial Statements, however, we anticipate recognition of additional assets and corresponding liabilities related to leases on our Condensed Consolidated Balance Sheets. In March 2016, the FASB issued Accounting Standard Update No. 2016-09 (ASU 2016-09) “Improvements to Employee Share-Based Payment Accounting.” ASU 2016-09 simplifies several aspects of employee share-based payment accounting, including the income tax consequences, classification of awards as either equity or liabilities and classification on the statement of cash flows. This guidance will become effective for us beginning in the first quarter of 2017. Early adoption is permitted. We plan to adopt the guidance in the first quarter of 2017. We are evaluating the impact of the adoption of this standard on our Condensed Consolidated Financial Statements. In June 2016, the FASB issued Accounting Standard Update No. 2016-13 (ASU 2016-13) “Measurement of Credit Losses on Financial Instruments.” ASU 2016-13 requires measurement and recognition of expected credit losses for financial assets held. This guidance will become effective for us beginning in the first quarter of 2020 and must be adopted using a modified retrospective approach, with certain exceptions. Early adoption is permitted beginning in the first quarter of 2019. We are evaluating the impact of the adoption of this standard on our Condensed Consolidated Financial Statements.

SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES

Basis of Presentation

The accompanying unaudited Condensed Consolidated Financial Statements have been prepared in accordance with U.S. generally accepted accounting principles for interim financial information. The financial statements include all adjustments, consisting of normal recurring adjustments that the management of Gilead Sciences, Inc. (Gilead, we or us) believes are necessary for a fair presentation of the periods presented. These interim financial results are not necessarily indicative of results expected for the full fiscal year or for any subsequent interim period.

The accompanying Condensed Consolidated Financial Statements include the accounts of Gilead, our wholly-owned subsidiaries and certain variable interest entities for which we are the primary beneficiary. All intercompany transactions have been eliminated. For consolidated entities where we own or are exposed to less than 100% of the economics, we record net income or loss attributable to noncontrolling interest in our Condensed Consolidated Statements of Income equal to the percentage of the economic or ownership interest retained in such entities by the respective noncontrolling parties.

We assess whether we are the primary beneficiary of a variable interest entity (VIE) at the inception of the arrangement and at each reporting date. This assessment is based on our power to direct the activities of the VIE that most significantly impact the VIE’s economic performance and our obligation to absorb losses or the right to receive benefits from the VIE that could potentially be significant to the VIE. As of September 30, 2016, the only material VIE was our joint venture with Bristol-Myers Squibb Company (BMS) which is described in Note 8, Collaborative Arrangements.

The accompanying Condensed Consolidated Financial Statements and related Notes to Condensed Consolidated Financial Statements should be read in conjunction with the audited Consolidated Financial Statements and the related notes thereto for the year ended December 31, 2015, included in our Annual Report on Form 10-K filed with the U.S. Securities and Exchange Commission.

Significant Accounting Policies, Estimates and Judgments

The preparation of these Condensed Consolidated Financial Statements requires us to make estimates and judgments that affect the reported amounts of assets, liabilities, revenues and expenses and related disclosures. On an ongoing basis, we evaluate our significant accounting policies and estimates. We base our estimates on historical experience and on various market-specific and other relevant assumptions that we believe to be reasonable under the circumstances, the results of which form the basis for making judgments about the carrying values of assets and liabilities that are not readily apparent from other sources. Estimates are assessed each period and updated to reflect current information. Actual results may differ significantly from these estimates.

Concentrations of Risk

We are subject to credit risk from our portfolio of cash, cash equivalents and marketable securities. Under our investment policy, we limit amounts invested in such securities by credit rating, maturity, industry group, investment type and issuer, except for securities issued by the U.S. government. We are not exposed to any significant concentrations of credit risk from these financial instruments. The goals of our investment policy, in order of priority, are as follows: safety and preservation of principal and diversification of risk; liquidity of investments sufficient to meet cash flow requirements; and a competitive after-tax rate of return.

We are also subject to credit risk from our accounts receivable related to our product sales. The majority of our trade accounts receivable arises from product sales in the United States, Europe and Japan.

As of September 30, 2016, our accounts receivable in Southern Europe, specifically Greece, Italy, Portugal and Spain, totaled approximately $566 million, of which $132 million were greater than 120 days past due, including $62 million greater than 365 days past due. To date, we have not experienced significant losses with respect to the collection of our accounts receivable. We believe that our allowance for doubtful accounts was adequate at September 30, 2016.

Recent Accounting Pronouncements

In May 2014, the Financial Accounting Standards Board (FASB) issued Accounting Standard Update No. 2014-09 (ASU 2014-09) “Revenue from Contracts with Customers.” The standard’s core principle is that a reporting entity will recognize revenue when it transfers promised goods or services to customers in an amount that reflects the consideration to which the entity expects to be entitled in exchange for those goods or services. The standard will become effective for us beginning in the first quarter of 2018. Early adoption is permitted in 2017. Entities have the option of using either a full retrospective or a modified retrospective approach to adopt this new guidance. The FASB issued supplemental adoption guidance and clarification to ASU 2014-09 in March 2016, April 2016 and May 2016 within ASU 2016-08 “Revenue from Contracts with Customers: Principal vs. Agent Considerations,” ASU 2016-10 “Revenue from Contracts with Customers: Identifying Performance Obligations and Licensing” and ASU 2016-12 “Revenue from Contracts with Customers: Narrow-Scope Improvements and Practical Expedients,” respectively. We are evaluating the impact of the adoption of these standards on our Condensed Consolidated Financial Statements.

In November 2015, the FASB issued Accounting Standard Update No. 2015-17 (ASU 2015-17) “Balance Sheet Classification of Deferred Taxes.” ASU 2015-17 requires that deferred tax liabilities and assets be classified as noncurrent on the balance sheet. Previous guidance required deferred tax liabilities and assets to be separated into current and noncurrent amounts on the balance sheet. The guidance will become effective for us beginning in the first quarter of 2017 and may be applied either prospectively or retrospectively. Early adoption is permitted. We plan to adopt the guidance in the first quarter of 2017 on a retrospective basis and will reclassify current deferred tax amounts on our Condensed Consolidated Balance Sheets as noncurrent.

In January 2016, the FASB issued Accounting Standard Update No. 2016-01(ASU 2016-01) “Recognition and Measurement of Financial Assets and Financial Liabilities.” ASU 2016-01 changes accounting for equity investments, financial liabilities under the fair value option and the presentation and disclosure requirements for financial instruments. In addition, it clarified guidance related to the valuation allowance assessment when recognizing deferred tax assets resulting from unrealized losses on available-for-sale debt securities. The guidance will become effective for us beginning in the first quarter of 2018 and must be adopted using a modified retrospective approach, with certain exceptions. Early adoption is permitted for certain provisions. We are evaluating the impact of the adoption of this standard on our Condensed Consolidated Financial Statements.

In February 2016, the FASB issued Accounting Standard Update No. 2016-02 (ASU 2016-02) “Leases.” ASU 2016-02 amends a number of aspects of lease accounting, including requiring lessees to recognize almost all leases with a term greater than one year as a right-of-use asset and corresponding liability, measured at the present value of the lease payments. The guidance will become effective for us beginning in the first quarter of 2019 and is required to be adopted using a modified retrospective approach. Early adoption is permitted. We are evaluating the impact of the adoption of this standard on our Condensed Consolidated Financial Statements, however, we anticipate recognition of additional assets and corresponding liabilities related to leases on our Condensed Consolidated Balance Sheets.

In March 2016, the FASB issued Accounting Standard Update No. 2016-09 (ASU 2016-09) “Improvements to Employee Share-Based Payment Accounting.” ASU 2016-09 simplifies several aspects of employee share-based payment accounting, including the income tax consequences, classification of awards as either equity or liabilities and classification on the statement of cash flows. This guidance will become effective for us beginning in the first quarter of 2017. Early adoption is permitted. We plan to adopt the guidance in the first quarter of 2017. We are evaluating the impact of the adoption of this standard on our Condensed Consolidated Financial Statements.

In June 2016, the FASB issued Accounting Standard Update No. 2016-13 (ASU 2016-13) “Measurement of Credit Losses on Financial Instruments.” ASU 2016-13 requires measurement and recognition of expected credit losses for financial assets held. This guidance will become effective for us beginning in the first quarter of 2020 and must be adopted using a modified retrospective approach, with certain exceptions. Early adoption is permitted beginning in the first quarter of 2019. We are evaluating the impact of the adoption of this standard on our Condensed Consolidated Financial Statements.