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Employee Benefit Plans - Schedule of Nonvested Stock Options Activity (Detail) (USD $)
In Millions, unless otherwise specified
 12 Months Ended
Dec. 31, 2014
Dec. 31, 2013
Outstanding, Beginning 5.9us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingNumber  
Vested, Shares (0.1)dxcm_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsVestedInPeriod  
Forfeited, Shares 0us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsForfeituresInPeriod  
Outstanding, Ending 3.1us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingNumber  
Outstanding, Weighted-Average Grant Date Fair Value $ 4.60dxcm_ShareBasedCompensationArrangementByShareBasedPaymentAwardAwardsNonvestedWeightedAverageGrantDateFairValue  
Outstanding, Weighted-Average Grant Date Fair Value $ 4.60us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardOptionsVestedWeightedAverageGrantDateFairValue  
Outstanding, Weighted-Average Grant Date Fair Value $ 0dxcm_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsForfeituresInPeriodWeightedAverageGrantDateFairValue  
Outstanding, Weighted-Average Grant Date Fair Value $ 0dxcm_ShareBasedCompensationArrangementByShareBasedPaymentAwardAwardsNonvestedWeightedAverageGrantDateFairValue  
Nonvested [Member]    
Outstanding, Beginning   0.1us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingNumber
/ us-gaap_AwardTypeAxis
= dxcm_NonvestedMember
Outstanding, Ending 0us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingNumber
/ us-gaap_AwardTypeAxis
= dxcm_NonvestedMember		 0.1us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingNumber
/ us-gaap_AwardTypeAxis
= dxcm_NonvestedMember