Contingencies	9 Months Ended
Contingencies	Sep. 30, 2019
Commitments and Contingencies Disclosure [Abstract]
Contingencies	Contingencies Litigation On March 28, 2016, AgaMatrix, Inc., or AgaMatrix, filed a patent infringement lawsuit against us in the U.S. District Court for the District of Oregon, asserting that certain of our products infringe three patents held by AgaMatrix. (After filing suit, AgaMatrix reorganized its business and the Court granted AgaMatrix’s motion to substitute the newly created entity WaveForm Technologies, Inc., as the plaintiff following AgaMatrix’s transfer of the three asserted patents to WaveForm.) DexCom filed petitions for inter partes review with the Patent Trial and Appeal Board, or PTAB, of the U.S. Patent and Trademark Office, challenging each of the three asserted patents as being unpatentable in view of prior art. The PTAB issued a Final Written Decision for each of the first two patents on February 28, 2018, where the PTAB found the majority of asserted claims from the first patent unpatentable and the remaining claims under review not unpatentable. The PTAB found all claims under review from the second patent not unpatentable. On September 12, 2018, the PTAB found all of the asserted claims in the third patent unpatentable. In October 2018, we filed in the District Court a motion for summary judgment that all remaining asserted claims are invalid. The District Court granted that motion and, on August 23, 2019, entered judgment in our favor. On September 6, 2019, WaveForm appealed the judgment. We have also filed several lawsuits against AgaMatrix. We filed a patent infringement lawsuit against Agamatrix in the United States District Court for the Central District of California, or C.D. Cal., in which a Final Judgment of non-infringement was entered by the C.D. Cal judge on February 23, 2018 and affirmed on appeal by the Federal Circuit on March 7, 2019. AgaMatrix was awarded attorneys' fees for this lawsuit. As of September 30, 2019, we have accrued an immaterial amount for those fees. The fee decision is currently on appeal to the Federal Circuit. On September 15, 2017, we filed a patent infringement lawsuit against AgaMatrix in the United States District Court for the District of Delaware, asserting certain single-point blood glucose monitoring products of AgaMatrix infringe two patents held by us. In addition, on September 18, 2017, we filed a Complaint against AgaMatrix in the International Trade Commission, referred to as the ITC, requesting that the ITC institute an investigation and issue an order excluding certain products of AgaMatrix from importation into or sale in the United States based on AgaMatrix’s infringement of the same two patents asserted in the Delaware litigation. The investigation was terminated by the ITC on April 4, 2019 with a finding of non-infringement. The decision is currently on appeal. Neither the outcome of these lawsuits nor the amount and range of potential loss associated with the lawsuits can be assessed at this time. Other than the attorneys’ fees described above, as of September 30, 2019 we have accrued no amounts for contingent losses associated with these suits. We are subject to various claims, complaints and legal actions that arise from time to time in the normal course of business, including commercial insurance, product liability and employment related matters. In addition, from time to time, we may bring claims or initiate lawsuits against various third parties with respect to matters arising out of the ordinary course of our business, including commercial and employment related matters. We do not expect that the resolution of these matters would, or will, have a material adverse effect or material impact on our financial position or results of operations.