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Collaborative Arrangements - Collaborative Arrangements Narrative (Details) $ in Millions | 3 Months Ended
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Mar. 31, 2019 USD ($)
Collaborative Arrangements [Abstract] |
Collaboration Agreement, Initial Consideration Transferred | $ 165
Other Research and Development Expense | $ 126

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- Definition Collaboration Agreement, Initial Consideration Transferred + References No definition available. + Details
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Balance Type: | credit
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- Definition Collaborative Arrangements [Abstract] + References No definition available. + Details
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Namespace Prefix: | gild_
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- Definition Amount of other research and development expense. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 730 -SubTopic 10 -Section 50 -Paragraph 1 -URI http://asc.fasb.org/extlink&oid=6420194&loc=d3e21568-108373 + Details
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Namespace Prefix: | us-gaap_
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