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Income Taxes - Additional Information (Detail) (USD $)
12 Months Ended
Dec. 31, 2014
Dec. 31, 2013
Dec. 31, 2012
Operating Loss Carryforwards [Line Items]      
Net tax benefit (expense) $ (100,000)us-gaap_IncomeTaxExpenseBenefit $ 0us-gaap_IncomeTaxExpenseBenefit $ 1,300,000us-gaap_IncomeTaxExpenseBenefit
Tax Credit Carryforward, Expiration Date Jan. 01, 2020    
Tax credit carryforwards subject to expiration 2,100,000dxcm_UnusedExpiredFederalIncomeTaxCredits    
Net operating losses and tax credit carryforwards, limitations on use, ownership changes 50.00%dxcm_NetOperatingLossesAndTaxCreditCarryforwardsLimitationsOnUseOwnershipChanges    
Net operating losses and tax credit carryforwards, limitations on use, ownership change period (years) 3 years    
Valuation allowance amount 169,000,000us-gaap_DeferredTaxAssetsValuationAllowance 164,700,000us-gaap_DeferredTaxAssetsValuationAllowance  
Share-based compensation, excess tax benefits 63,900,000dxcm_ShareBasedCompensationExcessTaxBenefits    
Unrecognized tax benefits 0us-gaap_UnrecognizedTaxBenefitsIncomeTaxPenaltiesExpense    
Undistributed Earnings of Foreign Subsidiaries 1,000,000us-gaap_UndistributedEarningsOfForeignSubsidiaries    
Federal [Member]      
Operating Loss Carryforwards [Line Items]      
Operating Loss Carryforwards 507,500,000us-gaap_OperatingLossCarryforwards
/ us-gaap_IncomeTaxAuthorityAxis
= us-gaap_InternalRevenueServiceIRSMember
   
Deferred Tax Assets, Tax Credit Carryforwards, Research 8,100,000us-gaap_DeferredTaxAssetsTaxCreditCarryforwardsResearch
/ us-gaap_IncomeTaxAuthorityAxis
= us-gaap_InternalRevenueServiceIRSMember
   
Operating Loss Carryforwards, Expiration Dates Jan. 01, 2019    
State [Member]      
Operating Loss Carryforwards [Line Items]      
Operating Loss Carryforwards 333,100,000us-gaap_OperatingLossCarryforwards
/ us-gaap_IncomeTaxAuthorityAxis
= us-gaap_StateAndLocalJurisdictionMember
   
Deferred Tax Assets, Tax Credit Carryforwards, Research $ 10,800,000us-gaap_DeferredTaxAssetsTaxCreditCarryforwardsResearch
/ us-gaap_IncomeTaxAuthorityAxis
= us-gaap_StateAndLocalJurisdictionMember