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Segment Information Schedule of revenue by major customers (Details)
 3 Months Ended
Mar. 31, 2015
Mar. 31, 2014
McKesson Corp.    
Revenue, Major Customer [Line Items]    
Percentage of Revenues 25.00%us-gaap_ConcentrationRiskPercentage1
/ us-gaap_MajorCustomersAxis
= gild_MckessonCorpMember		 23.00%us-gaap_ConcentrationRiskPercentage1
/ us-gaap_MajorCustomersAxis
= gild_MckessonCorpMember
AmerisourceBergen Corp.    
Revenue, Major Customer [Line Items]    
Percentage of Revenues 21.00%us-gaap_ConcentrationRiskPercentage1
/ us-gaap_MajorCustomersAxis
= gild_AmerisourcebergenCorpMember		 27.00%us-gaap_ConcentrationRiskPercentage1
/ us-gaap_MajorCustomersAxis
= gild_AmerisourcebergenCorpMember
Cardinal Health, Inc.    
Revenue, Major Customer [Line Items]    
Percentage of Revenues 17.00%us-gaap_ConcentrationRiskPercentage1
/ us-gaap_MajorCustomersAxis
= gild_CardinalHealthIncMember		 13.00%us-gaap_ConcentrationRiskPercentage1
/ us-gaap_MajorCustomersAxis
= gild_CardinalHealthIncMember