DexCom (DXCM) 10-Q 6 Nov 19 2019 Q3 Quarterly report Financial data

Cover Page

Cover Page - shares	9 Months Ended
	Sep. 30, 2019	Nov. 01, 2019
Cover page.
Document Type	10-Q
Document Quarterly Report	true
Document Period End Date	Sep. 30, 2019
Document Transition Report	false
Entity File Number	000-51222
Entity Registrant Name	DEXCOM, INC.
Entity Incorporation, State or Country Code	DE
Entity Tax Identification Number	33-0857544
Entity Address, Address Line One	6340 Sequence Drive
Entity Address, City or Town	San Diego,
Entity Address, State or Province	CA
Entity Address, Postal Zip Code	92121
City Area Code	858
Local Phone Number	200-0200
Title of 12(b) Security	Common Stock, $0.001 Par Value Per Share
Trading Symbol	DXCM
Security Exchange Name	NASDAQ
Entity Current Reporting Status	Yes
Entity Interactive Data Current	Yes
Entity Filer Category	Large Accelerated Filer
Entity Small Business	false
Entity Emerging Growth	false
Entity Shell Company	false
Entity Common Stock, Shares Outstanding		91,528,588
Amendment Flag	false
Document Fiscal Year Focus	2019
Document Fiscal Period Focus	Q3
Entity Central Index Key	0001093557
Current Fiscal Year End Date	--12-31

Consolidated Balance Sheets

Consolidated Balance Sheets - USD ($) $ in Millions	Sep. 30, 2019	Dec. 31, 2018
Current assets:
Cash and cash equivalents	$ 395.6	$ 1,137
Short-term marketable securities	1,034.3	248.6
Accounts receivable, net	234.9	226.7
Inventory	120.4	70.7
Prepaid and other current assets	30.5	16.5
Total current assets	1,815.7	1,699.5
Property and equipment, net	301	183.1
Operating lease right-of-use assets	34.6
Goodwill	18.4	18.7
Other assets	16	14.7
Total assets	2,185.7	1,916
Current liabilities:
Accounts payable and accrued liabilities	232.4	147.1
Accrued payroll and related expenses	70.9	72.4
Operating lease liabilities, current portion	14.8
Deferred revenue	4.3	2.9
Total current liabilities	322.4	222.4
Long-term senior convertible notes	1,047.1	1,010.3
Operating lease liabilities, net of current portion	34.3
Other long-term liabilities	17.6	20
Total liabilities	1,421.4	1,252.7
Commitments and contingencies
Stockholders’ equity:
Preferred stock, $0.001 par value, 5.0 million shares authorized; no shares issued and outstanding at September 30, 2019 and December 31, 2018	0	0
Common stock, $0.001 par value, 200.0 million shares authorized; 92.3 million and 91.5 million shares issued and outstanding, respectively, at September 30, 2019; and 91.1 million and 90.0 million shares issued and outstanding, respectively, at December 31, 2018	0.1	0.1
Additional paid-in capital	1,651.6	1,560.6
Accumulated other comprehensive income	1	1.5
Accumulated deficit	(788.4)	(798.9)
Treasury stock, at cost; 0.8 million shares at September 30, 2019 and December 31, 2018	(100)	(100)
Total stockholders’ equity	764.3	663.3
Total liabilities and stockholders’ equity	$ 2,185.7	$ 1,916

Consolidated Balance Sheets (Pa

Consolidated Balance Sheets (Parenthetical) - $ / shares	Sep. 30, 2019	Dec. 31, 2018
Statement of Financial Position [Abstract]
Preferred stock, par value (in dollars per share)	$ 0.001	$ 0.001
Preferred stock, shares authorized	5,000,000	5,000,000
Preferred stock, shares issued	0	0
Preferred stock, shares outstanding	0	0
Common stock, par value (in dollars per share)	$ 0.001	$ 0.001
Common stock, shares authorized	200,000,000	200,000,000
Common stock, shares issued	92,300,000	91,100,000
Common stock, shares outstanding	91,500,000	90,000,000
Treasury stock	800,000	800,000

Consolidated Statements of Oper

Consolidated Statements of Operations - USD ($) shares in Millions, $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Income Statement [Abstract]
Revenues	$ 396.3	$ 266.7	$ 1,013.2	$ 693.6
Cost of sales	149.4	98.1	391	252.5
Gross profit	246.9	168.6	622.2	441.1
Operating expenses:
Research and development	66.7	50.1	194.7	142.1
Selling, general and administrative	124.2	104.6	386.7	320.7
Total operating expenses	190.9	154.7	581.4	462.8
Operating income (loss)	56	13.9	40.8	(21.7)
Interest expense	(15.1)	(4.9)	(45)	(14.5)
Income (loss) from equity investments	0	34.9	(4.2)	85
Interest and other income, net	4.9	0.9	18.3	1.6
Income before income taxes	45.8	44.8	9.9	50.4
Income tax expense (benefit)	0	(1.8)	1.5	(2.2)
Net income	$ 45.8	$ 46.6	$ 8.4	$ 52.6
Basic net income per share	$ 0.50	$ 0.53	$ 0.09	$ 0.60
Shares used to compute basic net income per share	91.3	88.5	90.9	88
Diluted net income per share	$ 0.50	$ 0.52	$ 0.09	$ 0.59
Shares used to compute diluted net income per share	92.5	90.3	92.2	89.3

Consolidated Statements of Comp

Consolidated Statements of Comprehensive Income - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Statement of Comprehensive Income [Abstract]
Net income	$ 45.8	$ 46.6	$ 8.4	$ 52.6
Other comprehensive income (loss), net of income taxes:
Foreign currency translation gain (loss)	(0.9)	0.9	(1)	2.2
Unrealized income (loss) on marketable debt securities	(0.1)	0.1	0.5	0.1
Total other comprehensive income (loss), net	(1)	1	(0.5)	2.3
Comprehensive income	$ 44.8	$ 47.6	$ 7.9	$ 54.9

Consolidated Statements of Stoc

Consolidated Statements of Stockholders' Equity - USD ($) shares in Millions, $ in Millions	Total	Common Stock	Additional Paid-In Capital	Accumulated Other Comprehensive Income (Loss)	Accumulated Deficit	Treasury Stock
Beginning Balance (in shares) at Dec. 31, 2017		87
Beginning Balance at Dec. 31, 2017	$ 419.4	$ 0.1	$ 1,093.7	$ (2.6)	$ (671.8)	$ 0
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Issuance of common stock under equity incentive plans (in shares)		1.6
Issuance of common stock under equity incentive plans	1.7		1.7
Issuance of common stock for Employee Stock Purchase Plan (in shares)		0.2
Issuance of common stock for Employee Stock Purchase Plan	8.9		8.9
Share-based compensation expense	77.3		77.3
Net income	52.6				52.6
Other comprehensive loss	2.3			2.3
Ending Balance (in shares) at Sep. 30, 2018		88.8
Ending Balance at Sep. 30, 2018	562.2	$ 0.1	1,181.6	(0.3)	(619.2)	0
Beginning Balance (in shares) at Jun. 30, 2018		88.4
Beginning Balance at Jun. 30, 2018	482.1	$ 0.1	1,149.1	(1.3)	(665.8)	0
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Issuance of common stock under equity incentive plans (in shares)		0.3
Issuance of common stock under equity incentive plans	0.6		0.6
Issuance of common stock for Employee Stock Purchase Plan (in shares)		0.1
Issuance of common stock for Employee Stock Purchase Plan	4.8		4.8
Share-based compensation expense	27.1		27.1
Net income	46.6				46.6
Other comprehensive loss	1			1
Ending Balance (in shares) at Sep. 30, 2018		88.8
Ending Balance at Sep. 30, 2018	562.2	$ 0.1	1,181.6	(0.3)	(619.2)	0
Beginning Balance (in shares) at Dec. 31, 2018		90
Beginning Balance at Dec. 31, 2018	663.3	$ 0.1	1,560.6	1.5	(798.9)	(100)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Cumulative-effect adjustment from adoption of new lease accounting standard (Note 2)	2.1
Cumulative-effect adjustment from adoption of new lease accounting standard (Note 2) | Accounting Standards Update 2016-02					2.1
Issuance of common stock under equity incentive plans (in shares)		1.3
Issuance of common stock under equity incentive plans	0.3		0.3
Issuance of common stock for Employee Stock Purchase Plan (in shares)		0.2
Issuance of common stock for Employee Stock Purchase Plan	11.6		11.6
Share-based compensation expense	79.1		79.1
Net income	8.4				8.4
Other comprehensive loss	(0.5)			(0.5)
Ending Balance (in shares) at Sep. 30, 2019		91.5
Ending Balance at Sep. 30, 2019	764.3	$ 0.1	1,651.6	1	(788.4)	(100)
Beginning Balance (in shares) at Jun. 30, 2019		91.2
Beginning Balance at Jun. 30, 2019	688.3	$ 0.1	1,620.4	2	(834.2)	(100)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Issuance of common stock under equity incentive plans (in shares)		0.2
Issuance of common stock under equity incentive plans	0		0
Issuance of common stock for Employee Stock Purchase Plan (in shares)		0.1
Issuance of common stock for Employee Stock Purchase Plan	6.8		6.8
Share-based compensation expense	24.4		24.4
Net income	45.8				45.8
Other comprehensive loss	(1)			(1)
Ending Balance (in shares) at Sep. 30, 2019		91.5
Ending Balance at Sep. 30, 2019	$ 764.3	$ 0.1	$ 1,651.6	$ 1	$ (788.4)	$ (100)

Consolidated Statements of Cash

Consolidated Statements of Cash Flows - USD ($) $ in Millions	9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018
Operating activities
Net income	$ 8.4	$ 52.6
Adjustments to reconcile net income to cash provided by operating activities:
Depreciation and amortization	34.4	20.5
Share-based compensation	79.1	77.3
Non-cash interest expense	37	11.3
Unrealized (gain) loss on equity investment	0	(40.8)
Realized (gain) loss on equity investment	4.2	(44.2)
Other non-cash income and expenses	0.6	5.1
Changes in operating assets and liabilities:
Accounts receivable, net	(9.2)	(36.2)
Inventory	(49.7)	(10)
Prepaid and other assets	(2.6)	(3.4)
Accounts payable and accrued liabilities	78.2	50.2
Accrued payroll and related expenses	(1.2)	6.2
Deferred revenue and other liabilities	(8.4)	0.9
Net cash provided by operating activities	170.8	89.5
Cash flows from investing activities:
Purchases of marketable securities	(1,556.8)	(340)
Proceeds from sale and maturity of marketable securities	773	231
Purchases of other equity investments	(1.2)	(1)
Purchases of property and equipment	(135.9)	(49.4)
Acquisitions, net of cash acquired	0	(11.3)
Net cash used in investing activities	(920.9)	(170.7)
Cash flows from financing activities:
Net proceeds from issuance of common stock	11.9	10.6
Payments on acquisition related contingent consideration liability	(0.7)	(1.8)
Other financing activities	(0.4)	0
Net cash provided by financing activities	10.8	8.8
Effect of exchange rate changes on cash, cash equivalents and restricted cash	(1.7)	(1.4)
Decrease in cash, cash equivalents and restricted cash	(741)	(73.8)
Cash, cash equivalents and restricted cash, beginning of period	1,137.1	441.5
Cash, cash equivalents and restricted cash, end of period	396.1	367.7
Reconciliation of cash, cash equivalents and restricted cash, end of period:
Total cash, cash equivalents and restricted cash	1,137.1	441.5
Supplemental disclosure of non-cash investing and financing transactions:
Acquisition of property and equipment included in accounts payable and accrued liabilities	22.3	$ 3
Right-of-use assets obtained in exchange for lease liabilities	$ 57.2

Organization and Significant Ac

Organization and Significant Accounting Policies	9 Months Ended
	Sep. 30, 2019
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Organization and Significant Accounting Policies	Organization and Significant Accounting Policies Organization and Business DexCom, Inc. is a medical device company focused on the design, development and commercialization of continuous glucose monitoring, or CGM, systems for use by people with diabetes and by healthcare providers. Unless the context requires otherwise, the terms “we,” “us,” “our,” the “company,” or “DexCom” refer to DexCom, Inc. and its subsidiaries. Basis of Presentation and Principles of Consolidation We have prepared the accompanying unaudited consolidated financial statements (the “financial statements”) in accordance with U.S. generally accepted accounting principles, or GAAP, for interim financial information and with the instructions to Form 10-Q and Article 10 of Securities and Exchange Commission, or SEC, Regulation S-X. Accordingly, they do not include all of the information and disclosures required by GAAP for complete financial statements. In the opinion of management, all adjustments, which include only normal recurring adjustments considered necessary for a fair presentation, have been included. Operating results for the three and nine months ended September 30, 2019 are not necessarily indicative of the results that may be expected for the year ending December 31, 2019 . We expect that revenues we generate from the sales of our products will fluctuate from quarter to quarter. We experience seasonality that is typical in our industry, with lower sales in the first quarter of each year compared to the fourth quarter of the previous year. These financial statements should be read in conjunction with the audited consolidated financial statements and related notes thereto for the year ended December 31, 2018 included in the Annual Report on Form 10-K that we filed with the SEC on February 21, 2019 . These financial statements include the accounts of DexCom, Inc. and our wholly owned subsidiaries. All significant intercompany balances and transactions have been eliminated in consolidation. We have reclassified certain amounts previously reported in our financial statements to conform to the current presentation. Use of Estimates The preparation of financial statements in conformity with GAAP requires us to make estimates and assumptions that affect the amounts reported in our financial statements and the disclosures made in the accompanying notes. Despite our intention to establish accurate estimates and use reasonable assumptions, actual results may differ from our estimates. Concentration of Credit Risk and Significant Customers Financial instruments which potentially subject us to concentrations of credit risk consist primarily of cash, cash equivalents, short-term investment securities, and accounts receivable. We limit our exposure to credit risk by placing our cash and investments with high credit quality financial institutions. We have also established guidelines regarding diversification of our investments and their maturities that are designed to maintain principal and maximize liquidity. We review these guidelines periodically and modify them to take advantage of trends in yields and interest rates and changes in our operations and financial position. Three of our customers are significant. The following table sets forth the percentage of total revenues that the revenues of these customers represented for the periods shown: Three Months Ended Nine Months Ended 2019 2018 2019 2018 Distributor A 17 % 15 % 16 % 15 % Distributor B 11 % * 12 % 13 % Distributor C 12 % * 10 % * * less than 10% The following table sets forth the percentage of accounts receivable that is attributable to our significant customers for the periods shown: September 30, 2019 December 31, 2018 Distributor A 20 % 19 % Distributor B 11 % 15 % Distributor C 13 % * * less than 10% Revenue Recognition We generate our revenue from the sale of our durable systems and disposable sensors (the Components). Our durable systems include a reusable transmitter and receiver. Disposable sensors are sold separately. We also provide free-of-charge software and mobile applications for use with our durable systems and disposable sensors. The initial durable system price is generally not dependent upon the subsequent purchase of any amount of disposable sensors. We sell our durable systems and disposable sensors through two main sales channels: 1) directly to customers who use our products or organizations (the Direct Channel) and 2) to distribution partners who resell our products (the Distributor Channel). In the Direct Channel, we sell the Components to customers and we receive payment directly from customers, organizations and third-party payors. Third-party payors primarily include commercial insurance companies and federal and state agencies (under Medicare and Medicaid programs). Policy elections and ASC Topic 606 practical expedients taken • We report revenue net of taxes collected from customers, which are subsequently remitted to governmental authorities; • We account for shipping and handling activities that are performed after a customer has obtained control of a good as fulfillment costs rather than as separate performance obligations; • We do not assess whether promised goods or services are performance obligations if they are immaterial in the context of the contract with the customer; and • If we expect, at contract inception, that the period between the transfer of control and corresponding payment from the customer will be one year or less, we do not adjust the amount of consideration for the effects of a significant financing component. Contracts and performance obligations We consider customer purchase orders, which in most cases are governed by agreements with distributors or third-party payors, to be contracts with a customer. For each contract, we consider the obligation to transfer the Components to the customer, each of which are distinct, to be separate performance obligations. The Components are individually priced and can be purchased separately or bundled in a contract. We also provide free-of-charge software, mobile applications and updates for our DexCom Share ® remote monitoring system. The standalone selling prices of our mobile applications and updates are based on an expected cost plus a margin approach. Transaction price Transaction price for the Components reflects the net consideration to which we expect to be entitled. Transaction price is typically based on contracted rates less any estimates of claim denials and historical reimbursement experience, which would include current and future expectations regarding reimbursement contracts, guidelines and payor mix, and less estimated variable consideration adjustments. Variable consideration Rebates. We estimate reductions to our revenues for rebates paid to payors, healthcare providers and distributors. Rebates are based on contractual arrangements or statutory requirements, which may vary by product, payor and individual payor plans. Our estimates are based on products sold, historical payor mix and, as available, known market events or trends and channel inventory data. We also take into consideration, as available, new information regarding changes in programs’ regulations and guidelines that would impact the amount of the actual rebates and/or our expectations regarding future payor mix for these programs. Product Returns. We generally provide a “ 30 -day money back guarantee” program whereby first-time end-user customers may return the durable system. In accordance with the terms of their distribution agreements, most distributors do not have rights of return outside of our limited warranty. The distributors typically have a limited time frame to notify us of any missing, damaged, defective or non-conforming products. Our returns have historically been immaterial. Revenue recognition We recognize revenue when control is transferred to our customers. The timing of revenue recognition is based on the satisfaction of performance obligations. Substantially all of the performance obligations associated with the Components are satisfied at a point in time, which typically occurs at shipment. Terms of direct and distributor orders are generally Freight on Board (FOB) shipping point for U.S. orders or Free Carrier (FCA) shipping point for international orders. For certain of our distributors, control transfers at delivery of the product to the customer. In cases where our free-of-charge software, mobile applications and updates are deemed to be separate performance obligations, revenue is recognized over time on a ratable basis over the estimated life of the durable systems. Our sales of the durable systems include an assurance-type warranty which is accounted for based on the cost accrual method recognized as expense when the products are sold and is not considered a separate performance obligation. See Note 9, “Business Segment and Geographic Information,” for revenues disaggregated by geographic region and by sales channel. Contract balances The timing of revenue recognition, billing and cash collections results in the recording of trade receivables and deferred revenue in our consolidated balance sheets. We recognize a receivable in the period in which our right to the consideration is unconditional. We generally do not have contracts or performance obligations with a term of more than one year. Payment terms vary by contract type and type of customer and generally range from 30 to 90 days. Accounts receivable as of September 30, 2019 and December 31, 2018 included unbilled accounts receivable of $5.2 million and $5.1 million , respectively. Unbilled accounts receivable consist of revenue recognized for Components we have delivered but not yet invoiced to customers. We expect to invoice and collect all unbilled accounts receivable within twelve months. Most of our deferred revenue as of September 30, 2019 is associated with certain of our free-of-charge software and mobile applications and will be recognized over the next twelve months. The table below shows revenue that we recognized as a result of changes in the contract liability balances in the periods shown. Three Months Ended Nine Months Ended (In millions) 2019 2018 2019 2018 Revenue recognized in the period from: Amounts included in contract liabilities at the beginning of the period $ 2.9 $ 5.0 $ 2.6 $ 1.9 Deferred cost of sales Deferred cost of sales are associated with sales for which revenue recognition criteria are not met but product has shipped and released from inventory. These costs are recognized in cost of sales when the associated revenue is recognized. Deferred cost of sales are included in prepaid and other current assets in our consolidated balance sheets. Incentive compensation costs We generally expense incentive compensation associated with our internal sales force when incurred because the amortization period for such costs, if capitalized, would have been one year or less. We record these costs in selling, general and administrative expense in our consolidated statement of operations. Leases We adopted Accounting Standards Codification Topic 842 (ASC 842) utilizing the modified retrospective transition method at the beginning of the first quarter of 2019. Under ASC 842, w e determine if an arrangement is a lease at inception. We record operating lease right-of-use assets and liabilities based on the present value of the lease payments over the lease term. In determining the present value of the lease payments, we use our incremental borrowing rate at the lease commencement date. We define the initial lease term to include the construction build-out period but to exclude lease extension periods when we are not reasonably certain to exercise our extension option. We record lease expense on a straight-line basis over the expected lease term. Lease costs which are variable and dependent on a rate, an index, or on usage of the asset are expensed in the period they are incurred. We have facilities lease agreements with lease and non-lease components, such as common area maintenance. We generally account for the lease and non-lease components of these agreements as a single lease component. We account for short-term lease expense on a straight-line basis over the lease term. Net Income Per Share Basic net income per share attributable to common stockholders is calculated by dividing the net income attributable to common stockholders by the weighted-average number of common shares outstanding during the period. Diluted net income per share is computed using the weighted average number of common shares outstanding during the period and, when dilutive, potential common share equivalents. Common share equivalents that we calculate using the treasury stock method include outstanding stock options and unvested RSUs that are settleable in shares of common stock and potential common shares from convertible securities that we intend to settle using a combination of shares of our common stock and cash. Common share equivalents that we calculate using the if-converted method include potential common shares from convertible securities that we intend to settle using only shares of our common stock. The following table sets forth the computation of basic and diluted net income per share for the periods shown. Three Months Ended Nine Months Ended (In millions) 2019 2018 2019 2018 Net income $ 45.8 $ 46.6 $ 8.4 $ 52.6 Net income per common share: Basic $ 0.50 $ 0.53 $ 0.09 $ 0.60 Diluted $ 0.50 $ 0.52 $ 0.09 $ 0.59 Basic weighted average shares outstanding 91.3 88.5 90.9 88.0 Effect of potentially dilutive stock options — 0.2 — 0.2 Effect of potentially dilutive restricted stock units 1.2 1.6 1.3 1.1 Diluted weighted average shares outstanding 92.5 90.3 92.2 89.3 Outstanding anti-dilutive securities not included in the diluted net income per share attributable to common stockholders calculations were as follows: Three Months Ended Nine Months Ended (In millions) 2019 2018 2019 2018 Unvested restricted stock units — — 0.3 0.3 Senior convertible notes due 2022 4.0 4.0 4.0 4.0 Senior convertible notes due 2023 5.2 — 5.2 — 2023 Warrants 5.2 — 5.2 — Total 14.4 4.0 14.7 4.3 Recent Accounting Guidance Recently Adopted Accounting Pronouncements In February 2016, the FASB issued Accounting Standards Update (ASU) No. 2016-02, Leases (Topic 842) (ASU 2016-02), which requires a lessee to recognize most leases on the consolidated balance sheet as lease liabilities with corresponding right-of-use assets. We adopted ASU 2016-02 utilizing the modified retrospective transition method at the beginning of the first quarter of 2019. See Note 2, “Leases,” for more information on the impact of our adoption of ASU 2016-02 and related disclosures. In August 2017, the FASB issued ASU No. 2017-12, Derivatives and Hedging (ASU 2017-12), which is intended to more closely align hedge accounting with companies’ risk management strategies, simplify the application of hedge accounting, and increase transparency regarding the scope and results of hedging programs. The guidance in this update is applied using a cumulative-effect adjustment to retained earnings at the beginning of the fiscal year of adoption. ASU 2017-12 is effective for public business entities for fiscal years beginning after December 15, 2018, including interim periods within those fiscal years. Our adoption of ASU 2017-12 at the beginning of the first quarter of 2019 did not have a significant impact on our financial statements. Recently Issued Accounting Pronouncements Not Yet Adopted In June 2016, the FASB issued ASU 2016-13, Financial Instruments - Credit Losses: Measurement of Credit Losses on Financial Instruments , which amends the impairment model by requiring entities to use a forward-looking approach based on expected losses to estimate credit losses on certain types of financial instruments, including trade receivables and available-for-sale debt securities. This update is effective for annual periods beginning after December 15, 2019, and interim periods within those periods, and early adoption is permitted. W e expect to adopt the standard on its effective date in the first quarter of 2020. We believe the adoption will modify the way we analyze financial instruments, but currently do not expect the adoption to have a material financial impact on our consolidated financial statements. In January 2017, the FASB issued ASU No. 2017-04, Intangibles – Goodwill and Other (Topic 350): Simplifying the Test for Goodwill Impairment (ASU 2017-04). This new guidance eliminates the requirement to calculate the implied fair value of goodwill to measure a goodwill impairment charge. Instead, entities will record an impairment charge based on the excess of a reporting unit’s carrying amount over its fair value. ASU 2017-04 is effective for public business entities for fiscal years beginning after December 15, 2019, including interim periods within those fiscal years, and early adoption is permitted. We are currently evaluating the impact that this guidance will have on our financial statements. In August 2018, the FASB issued ASU No. 2018-13, Fair Value Measurement: Disclosure Framework – Changes to the Disclosure Requirements for Fair Value Measurement (ASU 2018-13), which adds and modifies certain disclosure requirements for fair value measurements. Under the new guidance, entities will no longer be required to disclose the amount of and reasons for transfers between Level 1 and Level 2 of the fair value hierarchy, or valuation processes for Level 3 fair value measurements. However, public business entities will be required to disclose the range and weighted average of significant unobservable inputs used to develop Level 3 fair value measurements, and related changes in unrealized gains and losses included in other comprehensive income. ASU 2018-13 is effective for public business entities for fiscal years beginning after December 15, 2019, including interim periods within those fiscal years, and early adoption is permitted. We are currently evaluating the impact that this guidance will have on our financial statements. In August 2018, the FASB issued ASU No. 2018-15, Intangibles - Goodwill and Other – Internal-Use Software: Customer’s Accounting for Implementation Costs Incurred in a Cloud Computing Arrangement that is a Service Contract (ASU 2018-15). This new guidance requires a customer in a cloud computing arrangement to determine which implementation costs to capitalize as assets or expense as incurred. Capitalized implementation costs related to a hosting arrangement that is a service contract will be amortized over the term of the hosting arrangement, beginning when the module or component of the hosting arrangement is ready for its intended use. ASU 2018-15 is effective for public business entities for fiscal years beginning after December 15, 2019, including interim periods within those fiscal years, and early adoption is permitted. Application of this guidance can be applied either prospectively or retrospectively. We are currently evaluating the impact that this guidance will have on our financial statements.

Leases

Leases	9 Months Ended
	Sep. 30, 2019
Leases [Abstract]
Leases	Leases Impact of Adoption of ASC 842 We adopted ASC 842 utilizing the modified retrospective transition method through a $2.1 million cumulative-effect adjustment to retained earnings at the beginning of the first quarter of 2019. We will continue to report financial information for fiscal years prior to 2019 under the previous lease accounting standards. We elected the package of practical expedients permitted under the transition guidance in the new standard, which allowed us to carry forward the historical classification of leases that were in place as of January 1, 2019. Under the previous lease accounting standards we were deemed the owner of our Mesa, Arizona building during the construction period. As a result of our adoption of ASC 842, we have de-recognized the estimated fair value of the building shell and the related lease liability as of December 31, 2018 and recorded the difference between the asset and liability as an adjustment to retained earnings at the beginning of the first quarter of 2019. In addition, as a result of our adoption of ASC 842 we recorded operating lease right-of-use assets of $26.7 million , finance lease right-of-use assets of $15.3 million , operating lease liabilities of $40.4 million and finance lease liabilities of $15.9 million in our consolidated balance sheets at the beginning of the first quarter of 2019, with no material impact to our consolidated statement of operations. Operating lease right-of-use assets and liabilities are presented separately in our consolidated balance sheets. Finance lease right-of-use assets are included in property and equipment and finance lease liabilities are included in accounts payable and accrued liabilities and in other long-term liabilities in our consolidated balance sheets. Information About Our Leases Our corporate headquarters are located in San Diego, California. Our manufacturing facilities are located in San Diego, California and Mesa, Arizona. We lease approximately 219,000 square feet of space in San Diego under leases that expire in February and March 2022. We have the option to renew each of these leases for two additional five-year terms. In San Diego we also lease approximately 87,000 square feet of space under a lease that expires in February 2022 with no renewal options and approximately 132,600 square feet of space under a sublease that expires in January 2022. We lease approximately 148,800 square feet of space in Mesa, Arizona under a lease that expires in March 2028. We have the option to renew this lease for four additional five-year terms. We have also entered into other domestic and international operating lease agreements, primarily for office and warehouse space, that expire at various times through September 2029. The components of lease expense for the three and nine months ended September 30, 2019 were as follows: (In millions) Three Months Ended Nine Months Ended 2019 2019 Finance lease cost: Amortization of right-of-use assets $ 0.3 $ 0.8 Interest on lease liabilities 0.2 0.6 Operating lease cost 2.8 8.4 Short-term lease cost 1.3 3.3 Variable lease cost (1) 1.0 3.0 Total lease cost $ 5.6 $ 16.1 (1) Variable lease costs are primarily related to common area maintenance charges and property taxes. Other information related to leases was as shown in the table below. All figures include the leases recorded at the beginning of the first quarter of 2019 as a result of our adoption of ASC 842. (Dollars in millions) Three Months Ended Nine Months Ended 2019 2019 Cash paid for amounts included in the measurement of lease liabilities: Operating cash flows from operating leases $ 4.0 $ 10.0 Operating cash flows from finance leases $ 0.2 $ 0.6 Financing cash flows from finance leases $ 0.1 $ 0.4 Right-of-use assets obtained in exchange for lease liabilities: Operating leases $ 1.4 $ 41.7 Finance leases $ — $ 15.5 Weighted average remaining lease term in years: Operating leases 3.8 3.8 Finance leases 13.5 13.5 Weighted average discount rate: Operating leases 5.0 % 5.0 % Finance leases 5.0 % 5.0 % Amortization of operating lease right-of-use asset included in cash flows from operating activities in the Consolidated Statements of Cash Flows was $2.7 million and $6.7 million for the three and nine months ended September 30, 2019 , respectively. Future minimum lease payments under non-cancellable leases as of September 30, 2019 were as shown in the table below. (In millions) Operating Leases Finance Leases Remaining 2019 $ 4.1 $ 0.3 2020 16.9 1.3 2021 17.1 1.3 2022 6.3 1.4 2023 4.4 1.4 Thereafter 5.4 15.3 Total future lease cost 54.2 21.0 Less: Amount representing interest (4.9 ) (5.9 ) Present value of future payments 49.3 15.1 Less: Short-term leases not recorded as a liability (0.2 ) — Revised present value of future lease payments 49.1 15.1 Less: Current portion (14.8 ) (0.6 ) Long-term portion $ 34.3 $ 14.5
Leases	Leases Impact of Adoption of ASC 842 We adopted ASC 842 utilizing the modified retrospective transition method through a $2.1 million cumulative-effect adjustment to retained earnings at the beginning of the first quarter of 2019. We will continue to report financial information for fiscal years prior to 2019 under the previous lease accounting standards. We elected the package of practical expedients permitted under the transition guidance in the new standard, which allowed us to carry forward the historical classification of leases that were in place as of January 1, 2019. Under the previous lease accounting standards we were deemed the owner of our Mesa, Arizona building during the construction period. As a result of our adoption of ASC 842, we have de-recognized the estimated fair value of the building shell and the related lease liability as of December 31, 2018 and recorded the difference between the asset and liability as an adjustment to retained earnings at the beginning of the first quarter of 2019. In addition, as a result of our adoption of ASC 842 we recorded operating lease right-of-use assets of $26.7 million , finance lease right-of-use assets of $15.3 million , operating lease liabilities of $40.4 million and finance lease liabilities of $15.9 million in our consolidated balance sheets at the beginning of the first quarter of 2019, with no material impact to our consolidated statement of operations. Operating lease right-of-use assets and liabilities are presented separately in our consolidated balance sheets. Finance lease right-of-use assets are included in property and equipment and finance lease liabilities are included in accounts payable and accrued liabilities and in other long-term liabilities in our consolidated balance sheets. Information About Our Leases Our corporate headquarters are located in San Diego, California. Our manufacturing facilities are located in San Diego, California and Mesa, Arizona. We lease approximately 219,000 square feet of space in San Diego under leases that expire in February and March 2022. We have the option to renew each of these leases for two additional five-year terms. In San Diego we also lease approximately 87,000 square feet of space under a lease that expires in February 2022 with no renewal options and approximately 132,600 square feet of space under a sublease that expires in January 2022. We lease approximately 148,800 square feet of space in Mesa, Arizona under a lease that expires in March 2028. We have the option to renew this lease for four additional five-year terms. We have also entered into other domestic and international operating lease agreements, primarily for office and warehouse space, that expire at various times through September 2029. The components of lease expense for the three and nine months ended September 30, 2019 were as follows: (In millions) Three Months Ended Nine Months Ended 2019 2019 Finance lease cost: Amortization of right-of-use assets $ 0.3 $ 0.8 Interest on lease liabilities 0.2 0.6 Operating lease cost 2.8 8.4 Short-term lease cost 1.3 3.3 Variable lease cost (1) 1.0 3.0 Total lease cost $ 5.6 $ 16.1 (1) Variable lease costs are primarily related to common area maintenance charges and property taxes. Other information related to leases was as shown in the table below. All figures include the leases recorded at the beginning of the first quarter of 2019 as a result of our adoption of ASC 842. (Dollars in millions) Three Months Ended Nine Months Ended 2019 2019 Cash paid for amounts included in the measurement of lease liabilities: Operating cash flows from operating leases $ 4.0 $ 10.0 Operating cash flows from finance leases $ 0.2 $ 0.6 Financing cash flows from finance leases $ 0.1 $ 0.4 Right-of-use assets obtained in exchange for lease liabilities: Operating leases $ 1.4 $ 41.7 Finance leases $ — $ 15.5 Weighted average remaining lease term in years: Operating leases 3.8 3.8 Finance leases 13.5 13.5 Weighted average discount rate: Operating leases 5.0 % 5.0 % Finance leases 5.0 % 5.0 % Amortization of operating lease right-of-use asset included in cash flows from operating activities in the Consolidated Statements of Cash Flows was $2.7 million and $6.7 million for the three and nine months ended September 30, 2019 , respectively. Future minimum lease payments under non-cancellable leases as of September 30, 2019 were as shown in the table below. (In millions) Operating Leases Finance Leases Remaining 2019 $ 4.1 $ 0.3 2020 16.9 1.3 2021 17.1 1.3 2022 6.3 1.4 2023 4.4 1.4 Thereafter 5.4 15.3 Total future lease cost 54.2 21.0 Less: Amount representing interest (4.9 ) (5.9 ) Present value of future payments 49.3 15.1 Less: Short-term leases not recorded as a liability (0.2 ) — Revised present value of future lease payments 49.1 15.1 Less: Current portion (14.8 ) (0.6 ) Long-term portion $ 34.3 $ 14.5

Fair Value Measurements

Fair Value Measurements	9 Months Ended
	Sep. 30, 2019
Fair Value Disclosures [Abstract]
Fair Value Measurements	Fair Value Measurements Assets and Liabilities Measured at Fair Value on a Recurring Basis We estimate the fair value of our Level 1 financial instruments, which are in active markets, using unadjusted quoted market prices for identical instruments. We obtain the fair values for our Level 2 financial instruments, which are not in active markets, from a primary professional pricing source that uses quoted market prices for identical or comparable instruments, rather than direct observations of quoted prices in active markets. Fair values obtained from this professional pricing source can also be based on pricing models whereby all significant observable inputs, including maturity dates, issue dates, settlement dates, benchmark yields, reported trades, broker-dealer quotes, issue spreads, benchmark securities, bids, offers or other market-related data, are observable or can be derived from, or corroborated by, observable market data for substantially the full term of the asset. We validate the quoted market prices provided by our primary pricing service by comparing the fair values of our Level 2 marketable securities portfolio balance provided by our primary pricing service against the fair values of our Level 2 marketable securities portfolio balance provided by our investment managers. The following table summarizes financial assets that we measured at fair value on a recurring basis as of September 30, 2019 , classified in accordance with the fair value hierarchy. We sold the equity investment in Tandem Diabetes Care, Inc. that we held as of December 31, 2018 during the first quarter of 2019. Fair Value Measurements Using (In millions) Level 1 Level 2 Level 3 Total Cash equivalents $ 256.9 $ 45.0 $ — $ 301.9 Debt securities, available for sale: U.S. government agencies — 699.0 — 699.0 Commercial paper — 277.9 — 277.9 Corporate debt — 57.4 — 57.4 Total debt securities, available for sale — 1,034.3 — 1,034.3 Total assets measured at fair value on a recurring basis $ 256.9 $ 1,079.3 $ — $ 1,336.2 The following table summarizes financial assets that we measured at fair value on a recurring basis as of December 31, 2018 , classified in accordance with the fair value hierarchy. Fair Value Measurements Using (In millions) Level 1 Level 2 Level 3 Total Cash equivalents $ 199.3 $ 66.7 $ — $ 266.0 Equity investment in Tandem Diabetes Care, Inc. 38.0 — — 38.0 Debt securities, available for sale: U.S. government agencies — 173.1 — 173.1 Commercial paper — 36.2 — 36.2 Corporate debt — 1.3 — 1.3 Total debt securities, available for sale — 210.6 — 210.6 Total assets measured at fair value on a recurring basis $ 237.3 $ 277.3 $ — $ 514.6 There were no transfers between Level 1 and Level 2 securities during the three and nine months ended September 30, 2019 and 2018 . There were no transfers into or out of Level 3 securities during the three and nine months ended September 30, 2019 and 2018 . We hold certain other investments that we do not measure at fair value on a recurring basis. The carrying values of these investments are not significant and we include them in other assets in our consolidated balance sheets. It is impracticable for us to estimate the fair value of these investments on a recurring basis due to the fact that these entities are privately held and limited information is available. We monitor the information that becomes available from time to time and adjust the carrying values of these investments if there are identified events or changes in circumstances that have a significant adverse effect on the fair values. Fair Value of Senior Convertible Notes The fair value, based on trading prices (Level 1), of our Senior Convertible Notes were as follows as of the dates indicated. Fair Value Measurements Using Level 1 (In millions) September 30, 2019 December 31, 2018 0.75% Senior Convertible Notes due 2022 $ 635.6 $ 540.2 0.75% Senior Convertible Notes due 2023 996.5 859.6 Total fair value of outstanding senior convertible notes $ 1,632.1 $ 1,399.8 For more information on the carrying values and fair values of our 2022 Notes and 2023 Notes, see Note 5, “Debt.” Foreign Currency and Derivative Financial Instruments From time to time we engage in limited hedging transactions to reduce foreign currency risks on certain intercompany balances. The fair values of these derivatives are based on quoted market prices, which are Level 1 inputs. As of September 30, 2019 , we had no

Balance Sheet Details

Balance Sheet Details	9 Months Ended
	Sep. 30, 2019
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Balance Sheet Details	Balance Sheet Details Short-Term Marketable Securities Short-term marketable securities, consisting of equity securities and debt securities, were as follows as of the dates indicated. September 30, 2019 (In millions) Amortized Cost Gross Unrealized Gains Gross Unrealized Losses Estimated Market Value Debt securities, available for sale: U.S. government agencies $ 698.6 $ 0.4 $ — $ 699.0 Commercial paper 277.9 0.1 (0.1 ) 277.9 Corporate debt 57.4 — — 57.4 Total debt securities, available for sale 1,033.9 0.5 (0.1 ) 1,034.3 Total marketable securities $ 1,033.9 $ 0.5 $ (0.1 ) $ 1,034.3 December 31, 2018 (In millions) Cost or Amortized Cost Gross Unrealized Gains Gross Unrealized Losses Estimated Market Value Equity investment in Tandem Diabetes Care, Inc. $ 2.0 $ 36.0 $ — $ 38.0 Debt securities, available for sale: U.S. government agencies 173.2 — (0.1 ) 173.1 Commercial paper 36.2 — — 36.2 Corporate debt 1.3 — — 1.3 Total debt securities, available for sale 210.7 — (0.1 ) 210.6 Total marketable securities $ 212.7 $ 36.0 $ (0.1 ) $ 248.6 The following table reconciles the net gain recognized on equity securities during the three and nine months ended September 30, 2019 and 2018 to the unrealized gain recognized during the periods on equity securities still held at the reporting date. We sold the equity investment in Tandem Diabetes Care, Inc. that we held as of December 31, 2018 during the first quarter of 2019 and did not have any outstanding equity securities as of September 30, 2019 . Three Months Ended Nine Months Ended (In millions) 2019 2018 2019 2018 Net gains and losses recognized during the period on equity securities $ — $ 34.9 $ (4.2 ) $ 85.0 Less: Net gains and losses recognized during the period on equity securities sold during the period — (14.1 ) 4.2 (44.2 ) Unrealized gains recognized during the reporting period on equity securities still held at the reporting date $ — $ 20.8 $ — $ 40.8 As of September 30, 2019 and December 31, 2018 , all of our debt securities had contractual maturities of less than 12 months . Gross realized gains and losses on sales of our debt securities during the three and nine months ended September 30, 2019 and 2018 were not significant. We periodically review our portfolio of debt securities to determine if any investment is other-than-temporarily impaired due to changes in credit risk or other potential valuation concerns. We believe that the investments we held at September 30, 2019 were not other-than-temporarily impaired. Unrealized losses on available-for-sale debt securities at that date were not significant and were due to changes in interest rates, including market credit spreads, and not due to increased credit risks associated with specific securities. We do not intend to sell these investments and it is not more likely than not that we will be required to sell the investments before recovery of their amortized cost bases, which may be at maturity. Inventory (In millions) September 30, 2019 December 31, 2018 Raw materials $ 57.9 $ 30.8 Work-in-process 8.2 11.2 Finished goods 54.3 28.7 Total inventory $ 120.4 $ 70.7 During the three and nine months ended September 30, 2019 we recorded excess and obsolete inventory charges of $6.8 million and $10.1 million , respectively, in cost of sales as a result of our ongoing assessment of sales demand and inventory on hand for each product line. During the three and nine months ended September 30, 2018 we recorded excess and obsolete inventory charges of $0.6 million and $6.1 million , respectively, in cost of sales primarily as a result of the approval and launch of our G6 system and our ongoing assessment of sales demand and inventory on hand for each product line. Property and Equipment (In millions) September 30, 2019 December 31, 2018 Building and land $ 15.5 $ 6.0 Furniture and fixtures 12.2 9.0 Computer software and hardware 32.8 29.2 Machinery and equipment 97.5 80.7 Leasehold improvements 96.6 80.7 Construction in progress 148.0 57.3 Total cost 402.6 262.9 Less accumulated depreciation and amortization (101.6 ) (79.8 ) Total property and equipment, net $ 301.0 $ 183.1 Building and Land. Although we do not legally own these premises, under previous lease accounting standards we were deemed the owner of the construction project during the construction period of our manufacturing facility in Mesa, Arizona under a build-to-suit lease arrangement. As a result of our adoption of ASC 842, we de-recognized the estimated fair value of the building shell that was included in “building and land” in our consolidated balance sheets as of December 31, 2018 and the related lease liability and recorded the difference between the asset and liability as an adjustment to retained earnings at the beginning of the first quarter of 2019. The September 30, 2019 balance in “building and land” represents our finance lease right-of-use assets as a result of our adoption of ASC 842. Construction in Progress. The increase in construction in progress as of September 30, 2019 compared to December 31, 2018 is primarily due to continued investment in the expansion and automation of our production capabilities. Accounts Payable and Accrued Liabilities (In millions) September 30, 2019 December 31, 2018 Accounts payable trade $ 101.4 $ 75.5 Accrued tax, audit, and legal fees 20.3 11.7 Accrued rebates 74.6 36.1 Accrued warranty 7.5 6.8 Restructuring reserve 0.7 — Other accrued liabilities 27.9 17.0 Total accounts payable and accrued liabilities $ 232.4 $ 147.1 Accrued Rebates. The increase in the balance of accrued rebates as of September 30, 2019 compared with December 31, 2018 is due to increased sales volume in the pharmacy channel and to a lesser extent liabilities pending the outcome of ongoing discussions regarding the terms of one of our rebate agreements. Restructuring Reserve. In February 2019, our Board of Directors approved a restructuring plan that will result in the transition of certain of our operations to the Philippines. We estimate that we will incur total pre-tax charges and costs of approximately $8.0 million , primarily for employee severance benefits under both ongoing and one-time benefit arrangements. We have incurred most of these costs in the first half of 2019 and expect the restructuring activities to be substantially complete by the end of 2019. Other Long-Term Liabilities (In millions) September 30, 2019 December 31, 2018 Finance lease liabilities $ 14.5 $ 7.3 Deferred rent — 9.4 Other liabilities 3.1 3.3 Total other long-term liabilities $ 17.6 $ 20.0 Our adoption of ASC 842 during the first quarter of 2019 affected the balances of finance lease liabilities and deferred rent. See Note 2, “Leases,” for more information.

Debt

Debt	9 Months Ended
	Sep. 30, 2019
Debt Disclosure [Abstract]
Debt	Debt Senior Convertible Notes The following table shows the net carrying values, fair values, and if-converted values in excess of principal amounts for each of our senior convertible notes. (In millions) September 30, 2019 December 31, 2018 0.75% Senior Convertible Notes due 2022: Principal amount $ 400.0 $ 400.0 Unamortized debt discount (40.7 ) (51.1 ) Unamortized debt issuance costs (5.0 ) (6.3 ) Net carrying amount of Senior Convertible Notes due 2022 354.3 342.6 0.75% Senior Convertible Notes due 2023: Principal amount 850.0 850.0 Unamortized debt discount (148.1 ) (171.8 ) Unamortized debt issuance costs (9.1 ) (10.5 ) Net carrying amount of Senior Convertible Notes due 2023 692.8 667.7 Total net carrying amount of senior convertible notes $ 1,047.1 $ 1,010.3 Fair value of outstanding senior convertible notes: Senior Convertible Notes due 2022 $ 635.6 $ 540.2 Senior Convertible Notes due 2023 996.5 859.6 Total fair value of outstanding senior convertible notes $ 1,632.1 $ 1,399.8 Amount by which the notes' if-converted value exceeds their principal amount: Senior Convertible Notes due 2022 $ 221.6 $ 125.4 Senior Convertible Notes due 2023 93.9 — Total by which the notes' if-converted value exceeds their principal amount $ 315.5 $ 125.4 The following table summarizes the components of interest expense and the effective interest rates for each of our senior convertible notes for the periods shown. (In millions) Three Months Ended Nine Months Ended 2019 2018 2019 2018 Interest expense recognized: 0.75% Senior Convertible Notes due 2022: Contractual coupon interest $ 0.8 $ 0.8 $ 2.3 $ 2.3 Accretion of debt discount 3.5 3.4 10.4 10.0 Amortization of debt issuance costs 0.4 0.4 1.2 1.2 Interest expense recognized on 2022 Notes 4.7 4.6 13.9 13.5 0.75% Senior Convertible Notes due 2023: Contractual coupon interest 1.6 — 4.8 — Accretion of debt discount 8.0 — 23.7 — Amortization of debt issuance costs 0.5 — 1.5 — Interest expense recognized on 2023 Notes 10.1 — 30.0 — Total interest expense recognized on senior notes $ 14.8 $ 4.6 $ 43.9 $ 13.5 Effective interest rates: 0.75% Senior Convertible Notes due 2022 5.1 % 5.1 % 5.1 % 5.1 % 0.75% Senior Convertible Notes due 2023 5.6 % — 5.6 % — The discount on the senior convertible notes due 2022 is being amortized through May 15, 2022 . Interest on the 2022 Notes began accruing upon issuance and is payable semi-annually on May 15 and November 15 of each year. The discount on the senior convertible notes due 2023 is being amortized through December 1, 2023 . Interest on the 2023 Notes began accruing upon issuance and is payable semi-annually on June 1 and December 1 of each year. 0.75% Senior Convertible Notes due 2022 In June 2017, we completed an offering of $400.0 million aggregate principal amount of unsecured senior convertible notes with a stated interest rate of 0.75% and a maturity date of May 15, 2022 (the 2022 Notes). The net proceeds from the offering, after deducting initial purchasers’ discounts and costs directly related to the offering, were approximately $389.0 million . The 2022 Notes may be settled in cash, stock, or a combination thereof, solely at our discretion. It is our current intent and policy to settle all 2022 Notes conversions in shares of our common stock. The initial conversion rate of the 2022 Notes is 10.0918 shares per $1,000 principal amount of notes, which is equivalent to a conversion price of approximately $99.09 per share, subject to adjustments. We use the if-converted method for assumed conversion of the 2022 Notes to compute the weighted average shares of common stock outstanding for diluted earnings per share. Since upon conversion by the holders we may elect to settle such conversion in shares of our common stock, cash, or a combination thereof, we accounted for the cash conversion option as an equity instrument classified to stockholders’ equity. As a result, we recognized $72.6 million in additional paid-in-capital during 2017. In the event of a fundamental change (as defined in the indenture related to the 2022 Notes), holders of the 2022 Notes have the right to require us to repurchase for cash all or a portion of their notes at a price equal to 100% of the principal amount of the 2022 Notes, plus any accrued and unpaid interest. Holders of the 2022 Notes who convert their notes in connection with a make-whole fundamental change (as defined in the indenture) or following the delivery by DexCom of a notice of redemption are, under certain circumstances, entitled to an increase in the conversion rate. Prior to 5:00 p.m., New York City time, on the business day immediately preceding February 15, 2022, holders of the 2022 Notes may convert all or a portion of their notes, in multiples of $1,000 principal amount, only under the following circumstances: (1) during any calendar quarter commencing after September 30, 2017 (and only during such calendar quarter), if the last reported sale price of common stock for at least 20 trading days (whether or not consecutive) during the period of 30 consecutive trading days ending on the last trading day of the immediately preceding calendar quarter is greater than or equal to 130% of the applicable conversion price of the Notes on each such trading day; (2) during the five business day period after any five consecutive trading day period in which the trading price per $1,000 principal amount of the Notes for each day of that five day consecutive trading day period was less than 98% of the product of the last reported sale price of common stock and the applicable conversion rate of the Notes on such trading day; (3) if we call any or all of the Notes for redemption, at any time prior to the close on business on the scheduled trading day immediately preceding the redemption date; or (4) upon the occurrence of specified corporate transactions. On or after February 15, 2022 , until 5:00 p.m., New York City time, on the business day immediately preceding the maturity date, holders of the 2022 Notes may convert all or a portion of their notes regardless of the foregoing circumstances. DexCom may not redeem the 2022 Notes prior to May 15, 2020. On or after May 15, 2020, DexCom may redeem for cash all or part of the 2022 Notes, at its option, if the last reported sale price of our common stock has been at least 140% of the conversion price then in effect for at least 20 trading days (whether or not consecutive) during any 30 consecutive trading day period ending on, and including, the trading day immediately preceding the date on which DexCom provides notice of redemption. The redemption price will be equal to 100% of the principal amount of the 2022 Notes to be redeemed plus accrued and unpaid interest to, but excluding, the redemption date. No principal payments are due on the 2022 Notes prior to maturity. Other than restrictions relating to certain fundamental changes and consolidations, mergers or asset sales and customary anti-dilution adjustments, the indenture relating to the 2022 Notes includes customary terms and covenants, including certain events of default after which the 2022 Notes may be due and payable immediately. Circumstance (1) listed above occurred during the quarters ended March 31, 2019 and September 30, 2019. As a result, the 2022 Notes became convertible at the option of the holders from April 1, 2019 through June 30, 2019 and will remain convertible at the option of the holder from October 1, 2019 through December 31, 2019. Holders of 2022 Notes with an insignificant principal amount exercised their option to convert their 2022 Notes during the second quarter of 2019 and we settled these conversions with shares of our common stock. We continue to classify the carrying value of the liability component of the 2022 Notes as long-term debt, and the equity component of the 2022 Notes as permanent equity in our consolidated balance sheets as of September 30, 2019 . 0.75% Senior Convertible Notes due 2023 In November 2018, we completed an offering of $850.0 million aggregate principal amount of unsecured senior convertible notes with a stated interest rate of 0.75% and a maturity date of December 1, 2023 (the 2023 Notes). The net proceeds from the offering, after deducting initial purchasers’ discounts and costs directly related to the offering, were approximately $836.6 million . The 2023 Notes may be settled in cash, stock, or a combination thereof, solely at our discretion. It is our current intent and policy to settle all 2023 Notes conversions through combination settlement, satisfying the principal amount outstanding with cash and any note conversion value in excess of the principal amount in shares of our common stock. The initial conversion rate of the 2023 Notes is 6.0869 shares per $1,000 principal amount of notes, which is equivalent to a conversion price of approximately $164.29 per share, subject to adjustments. We use the treasury stock method for assumed conversion of the 2023 Notes to compute the weighted average shares of common stock outstanding for diluted earnings per share. We entered into transactions for a convertible note hedge (the 2023 Note Hedge) and warrants (the 2023 Warrants) concurrently with the issuance of the 2023 Notes. Since upon conversion by the holders we may elect to settle such conversion in shares of our common stock, cash, or a combination thereof, we accounted for the cash conversion option as an equity instrument classified to stockholders’ equity. As a result, we recognized $174.4 million in additional paid-in capital during 2018. Holders of the 2023 Notes have the right to require us to repurchase for cash all or a portion of their notes at 100% of their principal amount, plus any accrued and unpaid interest, upon the occurrence of a fundamental change (as defined in the indenture relating to the notes). We will also be required to increase the conversion rate for holders who convert their 2023 Notes in connection with certain fundamental changes occurring prior to the maturity date or following the delivery by DexCom of a notice of redemption. Holders of the 2023 Notes may convert all or a portion of their notes at their option prior to 5:00 p.m., New York City time, on the business day immediately preceding September 1, 2023, in multiples of $1,000 principal amount, only under the following circumstances: (1) during any calendar quarter commencing after March 31, 2019 (and only during such calendar quarter), if the last reported sale price of common stock for at least 20 trading days (whether or not consecutive) during the period of 30 consecutive trading days ending on the last trading day of the immediately preceding calendar quarter is greater than or equal to 130% of the applicable conversion price of the 2023 Notes on each such trading day; (2) during the five business day period after any five consecutive trading day period in which the trading price per $1,000 principal amount of the 2023 Notes for each day of that five -day consecutive trading day period was less than 98% of the product of the last reported sale price of common stock and the applicable conversion rate of the 2023 Notes on such trading day; (3) if we call any or all of the 2023 Notes for redemption, at any time prior to the close of business on the scheduled trading day immediately preceding the redemption date; or (4) upon the occurrence of specified corporate transactions. On or after September 1, 2023 , until 5:00 p.m., New York City time, on the second scheduled trading day immediately preceding the maturity date, holders of the 2023 Notes may convert all or a portion of their notes regardless of the foregoing circumstances. DexCom may not redeem the 2023 Notes prior to December 1, 2021. On or after December 1, 2021 and prior to September 1, 2023, DexCom may redeem for cash all or part of the 2023 Notes, at its option, if the last reported sale price of our common stock has been at least 130% of the conversion price then in effect for at least 20 trading days (whether or not consecutive) during any 30 consecutive trading day period ending on, and including, the trading day immediately preceding the date on which DexCom provides notice of redemption. The redemption price will be equal to 100% of the principal amount of the 2023 Notes to be redeemed plus accrued and unpaid interest to, but excluding, the redemption date. No principal payments are due on the 2023 Notes prior to maturity. Other than restrictions relating to certain fundamental changes and consolidations, mergers or asset sales and customary anti-dilution adjustments, the indenture relating to the 2023 Notes includes customary terms and covenants, including certain events of default after which the 2023 Notes may be due and payable immediately. As of the date of these financial statements, we are unaware of any current events or market conditions that would allow holders to convert the 2023 Notes. 2023 Note Hedge In connection with the offering of the 2023 Notes, in November 2018 we entered into convertible note hedge transactions with two of the initial purchasers of the 2023 Notes (the 2023 Counterparties) entitling us to purchase up to 5.2 million shares of our common stock at an initial price of $164.29 per share, each of which is subject to adjustment. The cost of the 2023 Note Hedge was $218.9 million and we accounted for it as an equity instrument by recognizing $218.9 million in additional paid-in capital during 2018. The 2023 Note Hedge will expire on December 1, 2023 . The 2023 Note Hedge is expected to reduce the potential equity dilution upon any conversion of the 2023 Notes and/or offset any cash payments we are required to make in excess of the principal amount of converted 2023 Notes if the daily volume-weighted average price per share of our common stock exceeds the strike price of the 2023 Note Hedge. The strike price of the 2023 Note Hedge initially corresponds to the conversion price of the 2023 Notes and is subject to certain adjustments under the terms of the 2023 Note Hedge. An assumed exercise of the 2023 Note Hedge by us is considered anti-dilutive since the effect of the inclusion would always be anti-dilutive with respect to the calculation of diluted earnings per share. 2023 Warrants In November 2018, we also sold warrants to the 2023 Counterparties to acquire up to 5.2 million shares of our common stock. The 2023 Warrants require net share settlement and a pro rated number of warrants will expire on each of the 60 scheduled trading days starting on March 1, 2024 . We received $183.8 million in cash proceeds from the sale of the 2023 Warrants, which we recorded in additional paid-in capital during 2018. The 2023 Warrants could have a dilutive effect on our earnings per share to the extent that the price of our common stock during a given measurement period exceeds the strike price of the 2023 Warrants. The strike price of the 2023 Warrants is initially $198.38 per share and is subject to certain adjustments under the terms of the warrant agreements. We use the treasury share method for assumed conversion of the 2023 Warrants when computing the weighted average common shares outstanding for diluted earnings per share. Revolving Credit Agreement In December 2018, we entered into a five-year $200.0 million revolving credit agreement (the Credit Agreement) with JPMorgan Chase Bank, NA, as administrative agent, Bank of America, Silicon Valley Bank, Union Bank and Bank of the West. The Credit Agreement provides a $50.0 million sublimit for borrowings in Canadian Dollars, Euros, British Pounds, Swedish Krona, Japanese Yen and any other currency that is subsequently approved by the lenders and a sub-facility of up to $10.0 million for letters of credit. Subject to customary conditions and the approval of any lender whose commitment would be increased, we have the option to increase the maximum principal amount available under the Credit Agreement by up to an additional $300.0 million , resulting in a maximum available principal amount of $500.0 million . However, at this time none of the lenders have committed to provide any such increase in their commitments. Revolving loans under the Credit Agreement bear interest at our choice of one of two base rates plus a range of applicable margin rates that are based on our leverage ratio. The first base rate is the highest of (a) the publicly announced JPMorgan Chase prime rate, (b) the federal funds rate, or (c) the overnight bank funding rate, and the applicable margin rate ranges from 0.375% to 1.000% . The second base rate is a LIBOR-based rate, and the applicable margin rate ranges from 1.375% to 2.000% . We will also pay a commitment fee of between 0.2% and 0.3% , payable quarterly in arrears, on the average daily unused amount of the revolving facility based on our leverage ratio. The Credit Agreement requires us to maintain a maximum leverage ratio and a minimum fixed charge coverage ratio. We were in compliance with these covenants as of September 30, 2019 . We drew no loans under the Credit Agreement during the three and nine months ended September 30, 2019 . As of September 30, 2019 , we had no outstanding borrowings, $4.4 million in outstanding letters of credit, and a total available balance of $195.6 million under the Credit Agreement.

Contingencies

Contingencies	9 Months Ended
	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.

Income Taxes

Income Taxes	9 Months Ended
	Sep. 30, 2019
Income Tax Disclosure [Abstract]
Income Taxes	Income Taxes Our effective tax rates for the three and nine months ended September 30, 2019 were 0.0% and 15.2% , compared to negative rates of 4.0% and 4.4% for the same periods of 2018 . For the nine months ended September 30, 2019 , the income tax expense is primarily attributable to foreign and state income tax expense as a result of current taxable income in those jurisdictions. No income tax benefit was recorded on losses in jurisdictions where valuation allowances are recorded against net deferred tax assets. We maintain a full valuation allowance against our net deferred tax assets as of September 30, 2019 based on our assessment that it is not more likely than not these future benefits will be realized before expiration.

Stockholders' Equity

Stockholders' Equity	9 Months Ended
	Sep. 30, 2019
Share-based Payment Arrangement [Abstract]
Stockholders' Equity	Stockholders’ Equity Share-Based Compensation Expense The following table summarizes share-based compensation expense, net of capitalized amounts, for the periods shown. Three Months Ended Nine Months Ended (In millions) 2019 2018 2019 2018 Cost of sales $ 2.2 $ 2.5 $ 6.9 $ 7.1 Research and development 8.1 8.1 25.8 24.8 Selling, general and administrative 14.1 16.5 46.4 45.4 Total share-based compensation expense included in net income $ 24.4 $ 27.1 $ 79.1 $ 77.3 As of September 30, 2019 , unrecognized estimated compensation costs related to unvested restricted stock units, or RSUs, and performance stock units, or PSUs, totaled $139.8 million and is expected to be recognized through 2022 . Restricted Stock Units A summary of our RSU and PSU activity for the nine months ended September 30, 2019 is as follows: Weighted Average Aggregate Grant Date Intrinsic (In millions, except weighted average grant date fair values) Shares Fair Value Value Nonvested at December 31, 2018 2.7 $ 69.19 $ 319.0 Granted 0.7 142.87 Vested (1.4 ) 68.89 Forfeited (0.2 ) 83.09 Nonvested at September 30, 2019 1.8 $ 95.06 $ 276.0 The total vest date fair value of RSUs that vested during the nine months ended September 30, 2019 was $195.9 million . No PSUs vested during that period.

Business Segment and Geographic

Business Segment and Geographic Information	9 Months Ended
	Sep. 30, 2019
Segment Reporting [Abstract]
Business Segment and Geographic Information	Business Segment and Geographic Information Reportable Segments An operating segment is identified as a component of a business that has discrete financial information available and for which the chief operating decision maker must decide the level of resource allocation. In addition, the guidance for segment reporting indicates certain quantitative materiality thresholds. We currently consider our operations to be, and manage our business globally within, one reportable segment, which is consistent with how our President and Chief Executive Officer, who is our chief operating decision maker, reviews our business, makes investment and resource allocation decisions, and assesses operating performance. Disaggregation of Revenue DexCom is domiciled in the United States. We sell our durable systems and disposable sensors through a direct sales force in the United States, Canada and some countries in Europe, and through distribution arrangements in the United States, Canada, Australia, New Zealand, and in some countries in Europe, Asia, Latin America, the Middle East and Africa. We disaggregate our revenue from contracts by major sales channel and geography as we believe they best depict how the nature, amount and timing of revenues and cash flows are affected by economic factors. Revenues by geographic region During the three and nine months ended September 30, 2019 and 2018 , no country outside of the United States generated revenue that represented more than 10% of our total revenue. The following tables set forth revenues disaggregated by our two primary geographical markets, United States and outside of the United States, based on the geographic location to which we deliver the Components: Three Months Ended Three Months Ended (In millions) Amount % of Total Amount % of Total Revenues: United States $ 308.8 78 % $ 202.4 76 % Outside of the United States 87.5 22 % 64.3 24 % Total revenues $ 396.3 100 % $ 266.7 100 % Nine Months Ended Nine Months Ended (In millions) Amount % of Total Amount % of Total Revenues: United States $ 785.6 78 % $ 537.4 77 % Outside of the United States 227.6 22 % 156.2 23 % Total revenues $ 1,013.2 100 % $ 693.6 100 % Revenues by customer sales channel The following tables set forth revenues disaggregated by customer sales channel: Three Months Ended Three Months Ended (In millions) Amount % of Total Amount % of Total Revenues: Distributor $ 270.4 68 % $ 154.6 58 % Direct 125.9 32 % 112.1 42 % Total revenues $ 396.3 100 % $ 266.7 100 % Nine Months Ended Nine Months Ended (In millions) Amount % of Total Amount % of Total Revenues: Distributor $ 680.0 67 % $ 431.3 62 % Direct 333.2 33 % 262.3 38 % Total revenues $ 1,013.2 100 % $ 693.6 100 %

Organization and Summary of Sig

Organization and Summary of Significant Accounting Policies (Policies)	9 Months Ended
	Sep. 30, 2019
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Basis of Presentation	Organization and Business DexCom, Inc. is a medical device company focused on the design, development and commercialization of continuous glucose monitoring, or CGM, systems for use by people with diabetes and by healthcare providers. Unless the context requires otherwise, the terms “we,” “us,” “our,” the “company,” or “DexCom” refer to DexCom, Inc. and its subsidiaries. Basis of Presentation and Principles of Consolidation We have prepared the accompanying unaudited consolidated financial statements (the “financial statements”) in accordance with U.S. generally accepted accounting principles, or GAAP, for interim financial information and with the instructions to Form 10-Q and Article 10 of Securities and Exchange Commission, or SEC, Regulation S-X. Accordingly, they do not include all of the information and disclosures required by GAAP for complete financial statements. In the opinion of management, all adjustments, which include only normal recurring adjustments considered necessary for a fair presentation, have been included. Operating results for the three and nine months ended September 30, 2019 are not necessarily indicative of the results that may be expected for the year ending December 31, 2019 . We expect that revenues we generate from the sales of our products will fluctuate from quarter to quarter. We experience seasonality that is typical in our industry, with lower sales in the first quarter of each year compared to the fourth quarter of the previous year. These financial statements should be read in conjunction with the audited consolidated financial statements and related notes thereto for the year ended December 31, 2018 included in the Annual Report on Form 10-K that we filed with the SEC on February 21, 2019 .
Principles of Consolidation	Basis of Presentation and Principles of Consolidation We have prepared the accompanying unaudited consolidated financial statements (the “financial statements”) in accordance with U.S. generally accepted accounting principles, or GAAP, for interim financial information and with the instructions to Form 10-Q and Article 10 of Securities and Exchange Commission, or SEC, Regulation S-X. Accordingly, they do not include all of the information and disclosures required by GAAP for complete financial statements. In the opinion of management, all adjustments, which include only normal recurring adjustments considered necessary for a fair presentation, have been included. Operating results for the three and nine months ended September 30, 2019 are not necessarily indicative of the results that may be expected for the year ending December 31, 2019 . We expect that revenues we generate from the sales of our products will fluctuate from quarter to quarter. We experience seasonality that is typical in our industry, with lower sales in the first quarter of each year compared to the fourth quarter of the previous year. These financial statements should be read in conjunction with the audited consolidated financial statements and related notes thereto for the year ended December 31, 2018 included in the Annual Report on Form 10-K that we filed with the SEC on February 21, 2019 .
Reclassification	We have reclassified certain amounts previously reported in our financial statements to conform to the current presentation.
Use of Estimates	Use of Estimates The preparation of financial statements in conformity with GAAP requires us to make estimates and assumptions that affect the amounts reported in our financial statements and the disclosures made in the accompanying notes. Despite our intention to establish accurate estimates and use reasonable assumptions, actual results may differ from our estimates.
Concentration of Credit Risk and Significant Customers	Concentration of Credit Risk and Significant Customers Financial instruments which potentially subject us to concentrations of credit risk consist primarily of cash, cash equivalents, short-term investment securities, and accounts receivable. We limit our exposure to credit risk by placing our cash and investments with high credit quality financial institutions. We have also established guidelines regarding diversification of our investments and their maturities that are designed to maintain principal and maximize liquidity. We review these guidelines periodically and modify them to take advantage of trends in yields and interest rates and changes in our operations and financial position.
Revenue Recognition	Revenue Recognition We generate our revenue from the sale of our durable systems and disposable sensors (the Components). Our durable systems include a reusable transmitter and receiver. Disposable sensors are sold separately. We also provide free-of-charge software and mobile applications for use with our durable systems and disposable sensors. The initial durable system price is generally not dependent upon the subsequent purchase of any amount of disposable sensors. We sell our durable systems and disposable sensors through two main sales channels: 1) directly to customers who use our products or organizations (the Direct Channel) and 2) to distribution partners who resell our products (the Distributor Channel). In the Direct Channel, we sell the Components to customers and we receive payment directly from customers, organizations and third-party payors. Third-party payors primarily include commercial insurance companies and federal and state agencies (under Medicare and Medicaid programs). Policy elections and ASC Topic 606 practical expedients taken • We report revenue net of taxes collected from customers, which are subsequently remitted to governmental authorities; • We account for shipping and handling activities that are performed after a customer has obtained control of a good as fulfillment costs rather than as separate performance obligations; • We do not assess whether promised goods or services are performance obligations if they are immaterial in the context of the contract with the customer; and • If we expect, at contract inception, that the period between the transfer of control and corresponding payment from the customer will be one year or less, we do not adjust the amount of consideration for the effects of a significant financing component. Contracts and performance obligations We consider customer purchase orders, which in most cases are governed by agreements with distributors or third-party payors, to be contracts with a customer. For each contract, we consider the obligation to transfer the Components to the customer, each of which are distinct, to be separate performance obligations. The Components are individually priced and can be purchased separately or bundled in a contract. We also provide free-of-charge software, mobile applications and updates for our DexCom Share ® remote monitoring system. The standalone selling prices of our mobile applications and updates are based on an expected cost plus a margin approach. Transaction price Transaction price for the Components reflects the net consideration to which we expect to be entitled. Transaction price is typically based on contracted rates less any estimates of claim denials and historical reimbursement experience, which would include current and future expectations regarding reimbursement contracts, guidelines and payor mix, and less estimated variable consideration adjustments. Variable consideration Rebates. We estimate reductions to our revenues for rebates paid to payors, healthcare providers and distributors. Rebates are based on contractual arrangements or statutory requirements, which may vary by product, payor and individual payor plans. Our estimates are based on products sold, historical payor mix and, as available, known market events or trends and channel inventory data. We also take into consideration, as available, new information regarding changes in programs’ regulations and guidelines that would impact the amount of the actual rebates and/or our expectations regarding future payor mix for these programs. Product Returns. We generally provide a “ 30 -day money back guarantee” program whereby first-time end-user customers may return the durable system. In accordance with the terms of their distribution agreements, most distributors do not have rights of return outside of our limited warranty. The distributors typically have a limited time frame to notify us of any missing, damaged, defective or non-conforming products. Our returns have historically been immaterial. Revenue recognition We recognize revenue when control is transferred to our customers. The timing of revenue recognition is based on the satisfaction of performance obligations. Substantially all of the performance obligations associated with the Components are satisfied at a point in time, which typically occurs at shipment. Terms of direct and distributor orders are generally Freight on Board (FOB) shipping point for U.S. orders or Free Carrier (FCA) shipping point for international orders. For certain of our distributors, control transfers at delivery of the product to the customer. In cases where our free-of-charge software, mobile applications and updates are deemed to be separate performance obligations, revenue is recognized over time on a ratable basis over the estimated life of the durable systems. Our sales of the durable systems include an assurance-type warranty which is accounted for based on the cost accrual method recognized as expense when the products are sold and is not considered a separate performance obligation. See Note 9, “Business Segment and Geographic Information,” for revenues disaggregated by geographic region and by sales channel. Contract balances The timing of revenue recognition, billing and cash collections results in the recording of trade receivables and deferred revenue in our consolidated balance sheets. We recognize a receivable in the period in which our right to the consideration is unconditional. We generally do not have contracts or performance obligations with a term of more than one year. Payment terms vary by contract type and type of customer and generally range from 30 to 90 days. Accounts receivable as of September 30, 2019 and December 31, 2018 included unbilled accounts receivable of $5.2 million and $5.1 million , respectively. Unbilled accounts receivable consist of revenue recognized for Components we have delivered but not yet invoiced to customers. We expect to invoice and collect all unbilled accounts receivable within twelve months. Most of our deferred revenue as of September 30, 2019 is associated with certain of our free-of-charge software and mobile applications and will be recognized over the next twelve months. The table below shows revenue that we recognized as a result of changes in the contract liability balances in the periods shown. Three Months Ended Nine Months Ended (In millions) 2019 2018 2019 2018 Revenue recognized in the period from: Amounts included in contract liabilities at the beginning of the period $ 2.9 $ 5.0 $ 2.6 $ 1.9 Deferred cost of sales Deferred cost of sales are associated with sales for which revenue recognition criteria are not met but product has shipped and released from inventory. These costs are recognized in cost of sales when the associated revenue is recognized. Deferred cost of sales are included in prepaid and other current assets in our consolidated balance sheets. Incentive compensation costs We generally expense incentive compensation associated with our internal sales force when incurred because the amortization period for such costs, if capitalized, would have been one year or less. We record these costs in selling, general and administrative expense in our consolidated statement of operations.
Leases	Leases We adopted Accounting Standards Codification Topic 842 (ASC 842) utilizing the modified retrospective transition method at the beginning of the first quarter of 2019. Under ASC 842, w e determine if an arrangement is a lease at inception. We record operating lease right-of-use assets and liabilities based on the present value of the lease payments over the lease term. In determining the present value of the lease payments, we use our incremental borrowing rate at the lease commencement date. We define the initial lease term to include the construction build-out period but to exclude lease extension periods when we are not reasonably certain to exercise our extension option. We record lease expense on a straight-line basis over the expected lease term. Lease costs which are variable and dependent on a rate, an index, or on usage of the asset are expensed in the period they are incurred. We have facilities lease agreements with lease and non-lease components, such as common area maintenance. We generally account for the lease and non-lease components of these agreements as a single lease component. We account for short-term lease expense on a straight-line basis over the lease term.
Net Income Per Share	Net Income Per Share Basic net income per share attributable to common stockholders is calculated by dividing the net income attributable to common stockholders by the weighted-average number of common shares outstanding during the period. Diluted net income per share is computed using the weighted average number of common shares outstanding during the period and, when dilutive, potential common share equivalents. Common share equivalents that we calculate using the treasury stock method include outstanding stock options and unvested RSUs that are settleable in shares of common stock and potential common shares from convertible securities that we intend to settle using a combination of shares of our common stock and cash. Common share equivalents that we calculate using the if-converted method include potential common shares from convertible securities that we intend to settle using only shares of our common stock.
Recent Accounting Guidance	Recent Accounting Guidance Recently Adopted Accounting Pronouncements In February 2016, the FASB issued Accounting Standards Update (ASU) No. 2016-02, Leases (Topic 842) (ASU 2016-02), which requires a lessee to recognize most leases on the consolidated balance sheet as lease liabilities with corresponding right-of-use assets. We adopted ASU 2016-02 utilizing the modified retrospective transition method at the beginning of the first quarter of 2019. See Note 2, “Leases,” for more information on the impact of our adoption of ASU 2016-02 and related disclosures. In August 2017, the FASB issued ASU No. 2017-12, Derivatives and Hedging (ASU 2017-12), which is intended to more closely align hedge accounting with companies’ risk management strategies, simplify the application of hedge accounting, and increase transparency regarding the scope and results of hedging programs. The guidance in this update is applied using a cumulative-effect adjustment to retained earnings at the beginning of the fiscal year of adoption. ASU 2017-12 is effective for public business entities for fiscal years beginning after December 15, 2018, including interim periods within those fiscal years. Our adoption of ASU 2017-12 at the beginning of the first quarter of 2019 did not have a significant impact on our financial statements. Recently Issued Accounting Pronouncements Not Yet Adopted In June 2016, the FASB issued ASU 2016-13, Financial Instruments - Credit Losses: Measurement of Credit Losses on Financial Instruments , which amends the impairment model by requiring entities to use a forward-looking approach based on expected losses to estimate credit losses on certain types of financial instruments, including trade receivables and available-for-sale debt securities. This update is effective for annual periods beginning after December 15, 2019, and interim periods within those periods, and early adoption is permitted. W e expect to adopt the standard on its effective date in the first quarter of 2020. We believe the adoption will modify the way we analyze financial instruments, but currently do not expect the adoption to have a material financial impact on our consolidated financial statements. In January 2017, the FASB issued ASU No. 2017-04, Intangibles – Goodwill and Other (Topic 350): Simplifying the Test for Goodwill Impairment (ASU 2017-04). This new guidance eliminates the requirement to calculate the implied fair value of goodwill to measure a goodwill impairment charge. Instead, entities will record an impairment charge based on the excess of a reporting unit’s carrying amount over its fair value. ASU 2017-04 is effective for public business entities for fiscal years beginning after December 15, 2019, including interim periods within those fiscal years, and early adoption is permitted. We are currently evaluating the impact that this guidance will have on our financial statements. In August 2018, the FASB issued ASU No. 2018-13, Fair Value Measurement: Disclosure Framework – Changes to the Disclosure Requirements for Fair Value Measurement (ASU 2018-13), which adds and modifies certain disclosure requirements for fair value measurements. Under the new guidance, entities will no longer be required to disclose the amount of and reasons for transfers between Level 1 and Level 2 of the fair value hierarchy, or valuation processes for Level 3 fair value measurements. However, public business entities will be required to disclose the range and weighted average of significant unobservable inputs used to develop Level 3 fair value measurements, and related changes in unrealized gains and losses included in other comprehensive income. ASU 2018-13 is effective for public business entities for fiscal years beginning after December 15, 2019, including interim periods within those fiscal years, and early adoption is permitted. We are currently evaluating the impact that this guidance will have on our financial statements. In August 2018, the FASB issued ASU No. 2018-15, Intangibles - Goodwill and Other – Internal-Use Software: Customer’s Accounting for Implementation Costs Incurred in a Cloud Computing Arrangement that is a Service Contract (ASU 2018-15). This new guidance requires a customer in a cloud computing arrangement to determine which implementation costs to capitalize as assets or expense as incurred. Capitalized implementation costs related to a hosting arrangement that is a service contract will be amortized over the term of the hosting arrangement, beginning when the module or component of the hosting arrangement is ready for its intended use. ASU 2018-15 is effective for public business entities for fiscal years beginning after December 15, 2019, including interim periods within those fiscal years, and early adoption is permitted. Application of this guidance can be applied either prospectively or retrospectively. We are currently evaluating the impact that this guidance will have on our financial statements.

Organization and Summary of S_2

Organization and Summary of Significant Accounting Policies (Tables)	9 Months Ended
	Sep. 30, 2019
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Schedules of Concentration of Risk, by Risk Factor	Three of our customers are significant. The following table sets forth the percentage of total revenues that the revenues of these customers represented for the periods shown: Three Months Ended Nine Months Ended 2019 2018 2019 2018 Distributor A 17 % 15 % 16 % 15 % Distributor B 11 % * 12 % 13 % Distributor C 12 % * 10 % * * less than 10% The following table sets forth the percentage of accounts receivable that is attributable to our significant customers for the periods shown: September 30, 2019 December 31, 2018 Distributor A 20 % 19 % Distributor B 11 % 15 % Distributor C 13 % * * less than 10%
Contract with Customer, Asset and Liability	The table below shows revenue that we recognized as a result of changes in the contract liability balances in the periods shown. Three Months Ended Nine Months Ended (In millions) 2019 2018 2019 2018 Revenue recognized in the period from: Amounts included in contract liabilities at the beginning of the period $ 2.9 $ 5.0 $ 2.6 $ 1.9
Schedule of Earnings Per Share, Basic and Diluted	The following table sets forth the computation of basic and diluted net income per share for the periods shown. Three Months Ended Nine Months Ended (In millions) 2019 2018 2019 2018 Net income $ 45.8 $ 46.6 $ 8.4 $ 52.6 Net income per common share: Basic $ 0.50 $ 0.53 $ 0.09 $ 0.60 Diluted $ 0.50 $ 0.52 $ 0.09 $ 0.59 Basic weighted average shares outstanding 91.3 88.5 90.9 88.0 Effect of potentially dilutive stock options — 0.2 — 0.2 Effect of potentially dilutive restricted stock units 1.2 1.6 1.3 1.1 Diluted weighted average shares outstanding 92.5 90.3 92.2 89.3
Outstanding anti-dilutive securities not included in diluted net loss per share	Outstanding anti-dilutive securities not included in the diluted net income per share attributable to common stockholders calculations were as follows: Three Months Ended Nine Months Ended (In millions) 2019 2018 2019 2018 Unvested restricted stock units — — 0.3 0.3 Senior convertible notes due 2022 4.0 4.0 4.0 4.0 Senior convertible notes due 2023 5.2 — 5.2 — 2023 Warrants 5.2 — 5.2 — Total 14.4 4.0 14.7 4.3

Leases (Tables)

Leases (Tables)	9 Months Ended
	Sep. 30, 2019
Leases [Abstract]
Components of lease expense	Other information related to leases was as shown in the table below. All figures include the leases recorded at the beginning of the first quarter of 2019 as a result of our adoption of ASC 842. (Dollars in millions) Three Months Ended Nine Months Ended 2019 2019 Cash paid for amounts included in the measurement of lease liabilities: Operating cash flows from operating leases $ 4.0 $ 10.0 Operating cash flows from finance leases $ 0.2 $ 0.6 Financing cash flows from finance leases $ 0.1 $ 0.4 Right-of-use assets obtained in exchange for lease liabilities: Operating leases $ 1.4 $ 41.7 Finance leases $ — $ 15.5 Weighted average remaining lease term in years: Operating leases 3.8 3.8 Finance leases 13.5 13.5 Weighted average discount rate: Operating leases 5.0 % 5.0 % Finance leases 5.0 % 5.0 % Amortization of operating lease right-of-use asset included in cash flows from operating activities in the Consolidated Statements of Cash Flows was $2.7 million and $6.7 million for the three and nine months ended September 30, 2019 , respectively. The components of lease expense for the three and nine months ended September 30, 2019 were as follows: (In millions) Three Months Ended Nine Months Ended 2019 2019 Finance lease cost: Amortization of right-of-use assets $ 0.3 $ 0.8 Interest on lease liabilities 0.2 0.6 Operating lease cost 2.8 8.4 Short-term lease cost 1.3 3.3 Variable lease cost (1) 1.0 3.0 Total lease cost $ 5.6 $ 16.1 (1) Variable lease costs are primarily related to common area maintenance charges and property taxes.
Future minimum lease payments, operating leases	Future minimum lease payments under non-cancellable leases as of September 30, 2019 were as shown in the table below. (In millions) Operating Leases Finance Leases Remaining 2019 $ 4.1 $ 0.3 2020 16.9 1.3 2021 17.1 1.3 2022 6.3 1.4 2023 4.4 1.4 Thereafter 5.4 15.3 Total future lease cost 54.2 21.0 Less: Amount representing interest (4.9 ) (5.9 ) Present value of future payments 49.3 15.1 Less: Short-term leases not recorded as a liability (0.2 ) — Revised present value of future lease payments 49.1 15.1 Less: Current portion (14.8 ) (0.6 ) Long-term portion $ 34.3 $ 14.5
Future minimum lease payments, finance leases	Future minimum lease payments under non-cancellable leases as of September 30, 2019 were as shown in the table below. (In millions) Operating Leases Finance Leases Remaining 2019 $ 4.1 $ 0.3 2020 16.9 1.3 2021 17.1 1.3 2022 6.3 1.4 2023 4.4 1.4 Thereafter 5.4 15.3 Total future lease cost 54.2 21.0 Less: Amount representing interest (4.9 ) (5.9 ) Present value of future payments 49.3 15.1 Less: Short-term leases not recorded as a liability (0.2 ) — Revised present value of future lease payments 49.1 15.1 Less: Current portion (14.8 ) (0.6 ) Long-term portion $ 34.3 $ 14.5

Fair Value Measurements (Tables

Fair Value Measurements (Tables)	9 Months Ended
	Sep. 30, 2019
Fair Value Disclosures [Abstract]
Fair Value Hierarchy for Financial Assets	The following table summarizes financial assets that we measured at fair value on a recurring basis as of September 30, 2019 , classified in accordance with the fair value hierarchy. We sold the equity investment in Tandem Diabetes Care, Inc. that we held as of December 31, 2018 during the first quarter of 2019. Fair Value Measurements Using (In millions) Level 1 Level 2 Level 3 Total Cash equivalents $ 256.9 $ 45.0 $ — $ 301.9 Debt securities, available for sale: U.S. government agencies — 699.0 — 699.0 Commercial paper — 277.9 — 277.9 Corporate debt — 57.4 — 57.4 Total debt securities, available for sale — 1,034.3 — 1,034.3 Total assets measured at fair value on a recurring basis $ 256.9 $ 1,079.3 $ — $ 1,336.2 The following table summarizes financial assets that we measured at fair value on a recurring basis as of December 31, 2018 , classified in accordance with the fair value hierarchy. Fair Value Measurements Using (In millions) Level 1 Level 2 Level 3 Total Cash equivalents $ 199.3 $ 66.7 $ — $ 266.0 Equity investment in Tandem Diabetes Care, Inc. 38.0 — — 38.0 Debt securities, available for sale: U.S. government agencies — 173.1 — 173.1 Commercial paper — 36.2 — 36.2 Corporate debt — 1.3 — 1.3 Total debt securities, available for sale — 210.6 — 210.6 Total assets measured at fair value on a recurring basis $ 237.3 $ 277.3 $ — $ 514.6
Schedule of Carrying Values and Estimated Fair Values of Debt Instruments	The fair value, based on trading prices (Level 1), of our Senior Convertible Notes were as follows as of the dates indicated. Fair Value Measurements Using Level 1 (In millions) September 30, 2019 December 31, 2018 0.75% Senior Convertible Notes due 2022 $ 635.6 $ 540.2 0.75% Senior Convertible Notes due 2023 996.5 859.6 Total fair value of outstanding senior convertible notes $ 1,632.1 $ 1,399.8 The following table shows the net carrying values, fair values, and if-converted values in excess of principal amounts for each of our senior convertible notes. (In millions) September 30, 2019 December 31, 2018 0.75% Senior Convertible Notes due 2022: Principal amount $ 400.0 $ 400.0 Unamortized debt discount (40.7 ) (51.1 ) Unamortized debt issuance costs (5.0 ) (6.3 ) Net carrying amount of Senior Convertible Notes due 2022 354.3 342.6 0.75% Senior Convertible Notes due 2023: Principal amount 850.0 850.0 Unamortized debt discount (148.1 ) (171.8 ) Unamortized debt issuance costs (9.1 ) (10.5 ) Net carrying amount of Senior Convertible Notes due 2023 692.8 667.7 Total net carrying amount of senior convertible notes $ 1,047.1 $ 1,010.3 Fair value of outstanding senior convertible notes: Senior Convertible Notes due 2022 $ 635.6 $ 540.2 Senior Convertible Notes due 2023 996.5 859.6 Total fair value of outstanding senior convertible notes $ 1,632.1 $ 1,399.8 Amount by which the notes' if-converted value exceeds their principal amount: Senior Convertible Notes due 2022 $ 221.6 $ 125.4 Senior Convertible Notes due 2023 93.9 — Total by which the notes' if-converted value exceeds their principal amount $ 315.5 $ 125.4

Balance Sheet Details (Tables)

Balance Sheet Details (Tables)	9 Months Ended
	Sep. 30, 2019
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Short Term Marketable Securities, Available for Sale	Short-Term Marketable Securities Short-term marketable securities, consisting of equity securities and debt securities, were as follows as of the dates indicated. September 30, 2019 (In millions) Amortized Cost Gross Unrealized Gains Gross Unrealized Losses Estimated Market Value Debt securities, available for sale: U.S. government agencies $ 698.6 $ 0.4 $ — $ 699.0 Commercial paper 277.9 0.1 (0.1 ) 277.9 Corporate debt 57.4 — — 57.4 Total debt securities, available for sale 1,033.9 0.5 (0.1 ) 1,034.3 Total marketable securities $ 1,033.9 $ 0.5 $ (0.1 ) $ 1,034.3 December 31, 2018 (In millions) Cost or Amortized Cost Gross Unrealized Gains Gross Unrealized Losses Estimated Market Value Equity investment in Tandem Diabetes Care, Inc. $ 2.0 $ 36.0 $ — $ 38.0 Debt securities, available for sale: U.S. government agencies 173.2 — (0.1 ) 173.1 Commercial paper 36.2 — — 36.2 Corporate debt 1.3 — — 1.3 Total debt securities, available for sale 210.7 — (0.1 ) 210.6 Total marketable securities $ 212.7 $ 36.0 $ (0.1 ) $ 248.6
Net Gain Recognized on Equity Securities	The following table reconciles the net gain recognized on equity securities during the three and nine months ended September 30, 2019 and 2018 to the unrealized gain recognized during the periods on equity securities still held at the reporting date. We sold the equity investment in Tandem Diabetes Care, Inc. that we held as of December 31, 2018 during the first quarter of 2019 and did not have any outstanding equity securities as of September 30, 2019 . Three Months Ended Nine Months Ended (In millions) 2019 2018 2019 2018 Net gains and losses recognized during the period on equity securities $ — $ 34.9 $ (4.2 ) $ 85.0 Less: Net gains and losses recognized during the period on equity securities sold during the period — (14.1 ) 4.2 (44.2 ) Unrealized gains recognized during the reporting period on equity securities still held at the reporting date $ — $ 20.8 $ — $ 40.8
Inventory	Inventory (In millions) September 30, 2019 December 31, 2018 Raw materials $ 57.9 $ 30.8 Work-in-process 8.2 11.2 Finished goods 54.3 28.7 Total inventory $ 120.4 $ 70.7
Property, Plant and Equipment	Property and Equipment (In millions) September 30, 2019 December 31, 2018 Building and land $ 15.5 $ 6.0 Furniture and fixtures 12.2 9.0 Computer software and hardware 32.8 29.2 Machinery and equipment 97.5 80.7 Leasehold improvements 96.6 80.7 Construction in progress 148.0 57.3 Total cost 402.6 262.9 Less accumulated depreciation and amortization (101.6 ) (79.8 ) Total property and equipment, net $ 301.0 $ 183.1
Accounts Payable and Accrued Liabilities	Accounts Payable and Accrued Liabilities (In millions) September 30, 2019 December 31, 2018 Accounts payable trade $ 101.4 $ 75.5 Accrued tax, audit, and legal fees 20.3 11.7 Accrued rebates 74.6 36.1 Accrued warranty 7.5 6.8 Restructuring reserve 0.7 — Other accrued liabilities 27.9 17.0 Total accounts payable and accrued liabilities $ 232.4 $ 147.1
Other Liabilities	Other Long-Term Liabilities (In millions) September 30, 2019 December 31, 2018 Finance lease liabilities $ 14.5 $ 7.3 Deferred rent — 9.4 Other liabilities 3.1 3.3 Total other long-term liabilities $ 17.6 $ 20.0

Debt (Tables)

Debt (Tables)	9 Months Ended
	Sep. 30, 2019
Debt Disclosure [Abstract]
Schedule of Carrying Values and Estimated Fair Values of Debt Instruments	The fair value, based on trading prices (Level 1), of our Senior Convertible Notes were as follows as of the dates indicated. Fair Value Measurements Using Level 1 (In millions) September 30, 2019 December 31, 2018 0.75% Senior Convertible Notes due 2022 $ 635.6 $ 540.2 0.75% Senior Convertible Notes due 2023 996.5 859.6 Total fair value of outstanding senior convertible notes $ 1,632.1 $ 1,399.8 The following table shows the net carrying values, fair values, and if-converted values in excess of principal amounts for each of our senior convertible notes. (In millions) September 30, 2019 December 31, 2018 0.75% Senior Convertible Notes due 2022: Principal amount $ 400.0 $ 400.0 Unamortized debt discount (40.7 ) (51.1 ) Unamortized debt issuance costs (5.0 ) (6.3 ) Net carrying amount of Senior Convertible Notes due 2022 354.3 342.6 0.75% Senior Convertible Notes due 2023: Principal amount 850.0 850.0 Unamortized debt discount (148.1 ) (171.8 ) Unamortized debt issuance costs (9.1 ) (10.5 ) Net carrying amount of Senior Convertible Notes due 2023 692.8 667.7 Total net carrying amount of senior convertible notes $ 1,047.1 $ 1,010.3 Fair value of outstanding senior convertible notes: Senior Convertible Notes due 2022 $ 635.6 $ 540.2 Senior Convertible Notes due 2023 996.5 859.6 Total fair value of outstanding senior convertible notes $ 1,632.1 $ 1,399.8 Amount by which the notes' if-converted value exceeds their principal amount: Senior Convertible Notes due 2022 $ 221.6 $ 125.4 Senior Convertible Notes due 2023 93.9 — Total by which the notes' if-converted value exceeds their principal amount $ 315.5 $ 125.4
Schedule of Interest Expense	The following table summarizes the components of interest expense and the effective interest rates for each of our senior convertible notes for the periods shown. (In millions) Three Months Ended Nine Months Ended 2019 2018 2019 2018 Interest expense recognized: 0.75% Senior Convertible Notes due 2022: Contractual coupon interest $ 0.8 $ 0.8 $ 2.3 $ 2.3 Accretion of debt discount 3.5 3.4 10.4 10.0 Amortization of debt issuance costs 0.4 0.4 1.2 1.2 Interest expense recognized on 2022 Notes 4.7 4.6 13.9 13.5 0.75% Senior Convertible Notes due 2023: Contractual coupon interest 1.6 — 4.8 — Accretion of debt discount 8.0 — 23.7 — Amortization of debt issuance costs 0.5 — 1.5 — Interest expense recognized on 2023 Notes 10.1 — 30.0 — Total interest expense recognized on senior notes $ 14.8 $ 4.6 $ 43.9 $ 13.5 Effective interest rates: 0.75% Senior Convertible Notes due 2022 5.1 % 5.1 % 5.1 % 5.1 % 0.75% Senior Convertible Notes due 2023 5.6 % — 5.6 % —

Stockholders' Equity (Tables)

Stockholders' Equity (Tables)	9 Months Ended
	Sep. 30, 2019
Share-based Payment Arrangement [Abstract]
Share based compensation expense	The following table summarizes share-based compensation expense, net of capitalized amounts, for the periods shown. Three Months Ended Nine Months Ended (In millions) 2019 2018 2019 2018 Cost of sales $ 2.2 $ 2.5 $ 6.9 $ 7.1 Research and development 8.1 8.1 25.8 24.8 Selling, general and administrative 14.1 16.5 46.4 45.4 Total share-based compensation expense included in net income $ 24.4 $ 27.1 $ 79.1 $ 77.3
Restricted Stock Units	A summary of our RSU and PSU activity for the nine months ended September 30, 2019 is as follows: Weighted Average Aggregate Grant Date Intrinsic (In millions, except weighted average grant date fair values) Shares Fair Value Value Nonvested at December 31, 2018 2.7 $ 69.19 $ 319.0 Granted 0.7 142.87 Vested (1.4 ) 68.89 Forfeited (0.2 ) 83.09 Nonvested at September 30, 2019 1.8 $ 95.06 $ 276.0

Business Segment and Geograph_2

Business Segment and Geographic Information (Tables)	9 Months Ended
	Sep. 30, 2019
Segment Reporting [Abstract]
Revenue from External Customers by Geographic Areas	The following tables set forth revenues disaggregated by our two primary geographical markets, United States and outside of the United States, based on the geographic location to which we deliver the Components: Three Months Ended Three Months Ended (In millions) Amount % of Total Amount % of Total Revenues: United States $ 308.8 78 % $ 202.4 76 % Outside of the United States 87.5 22 % 64.3 24 % Total revenues $ 396.3 100 % $ 266.7 100 % Nine Months Ended Nine Months Ended (In millions) Amount % of Total Amount % of Total Revenues: United States $ 785.6 78 % $ 537.4 77 % Outside of the United States 227.6 22 % 156.2 23 % Total revenues $ 1,013.2 100 % $ 693.6 100 %
Disaggregation of Revenue	The following tables set forth revenues disaggregated by customer sales channel: Three Months Ended Three Months Ended (In millions) Amount % of Total Amount % of Total Revenues: Distributor $ 270.4 68 % $ 154.6 58 % Direct 125.9 32 % 112.1 42 % Total revenues $ 396.3 100 % $ 266.7 100 % Nine Months Ended Nine Months Ended (In millions) Amount % of Total Amount % of Total Revenues: Distributor $ 680.0 67 % $ 431.3 62 % Direct 333.2 33 % 262.3 38 % Total revenues $ 1,013.2 100 % $ 693.6 100 %

Organization and Summary of S_3

Organization and Summary of Significant Accounting Policies - Additional Information (Detail) $ in Millions	9 Months Ended
	Sep. 30, 2019USD ($)SalesChannel	Dec. 31, 2018USD ($)
Organization And Summary Of Significant Accounting Policies [Line Items]
Number of sales channels | SalesChannel	2
Sales returns coverage period	30 days
Unbilled accounts receivable | $	$ 5.2	$ 5.1
Amortization period for incentive compensation costs	1 year

Organization and Significant _2

Organization and Significant Accounting Policies - Concentration Risk and Significant Customers (Details)	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018	Dec. 31, 2018
Distributor A
Concentration Risk [Line Items]
Percentage of revenue	17.00%	15.00%	16.00%	15.00%
Percentage of accounts receivable	20.00%		20.00%		19.00%
Distributor B
Concentration Risk [Line Items]
Percentage of revenue	11.00%		12.00%	13.00%
Percentage of accounts receivable	11.00%		11.00%		15.00%
Distributor C
Concentration Risk [Line Items]
Percentage of revenue	12.00%		10.00%
Percentage of accounts receivable	13.00%		13.00%

Organization and Significant _3

Organization and Significant Accounting Policies - Revenue Recognition from Contract with Customers (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Amounts included in contract liabilities at the beginning of the period	$ 2.9	$ 5	$ 2.6	$ 1.9

Organization and Significant _4

Organization and Significant Accounting Policies - Earnings Per Share, Basic and Diluted (Details) - USD ($) $ / shares in Units, shares in Millions, $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Net income (loss)	$ 45.8	$ 46.6	$ 8.4	$ 52.6
Net income per common share:
Basic (in USD per share)	$ 0.50	$ 0.53	$ 0.09	$ 0.60
Diluted (in USD per share)	$ 0.50	$ 0.52	$ 0.09	$ 0.59
Basic weighted average shares outstanding (in shares)	91.3	88.5	90.9	88
Diluted weighted average shares outstanding (in shares)	92.5	90.3	92.2	89.3
Options outstanding to purchase common stock
Net income per common share:
Effect of potentially dilutive stock options (in shares)	0	0.2	0	0.2
Unvested restricted stock units
Net income per common share:
Effect of potentially dilutive stock options (in shares)	1.2	1.6	1.3	1.1

Organization and Significant _5

Organization and Significant Accounting Policies - Anti-dilutive securities not included in calculation of net loss per share (Details) - shares shares in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive securities excluded from computation of net loss per share	14.4	4	14.7	4.3
Unvested restricted stock units
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive securities excluded from computation of net loss per share	0	0	0.3	0.3
2023 Warrants
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive securities excluded from computation of net loss per share	5.2	0	5.2	0
Senior convertible notes due 2022 | Senior convertible notes
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive securities excluded from computation of net loss per share	4	4	4	4
Senior convertible notes due 2023 | Senior convertible notes
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive securities excluded from computation of net loss per share	5.2	0	5.2	0

Leases - Narrative (Details)

Leases - Narrative (Details) $ in Millions	9 Months Ended
	Sep. 30, 2019USD ($)ft²renewal_term	Jan. 01, 2019USD ($)
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Operating lease right-of-use assets	$ 34.6	$ 26.7
Finance lease right-of-use asset		15.3
Operating lease liabilities	49.3	40.4
Finance lease liability	$ 15.1	15.9
Accumulated Deficit | Accounting Standards Update 2016-02
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Cumulative-effect adjustment to retained earnings		$ 2.1
Building and land
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Leased square footage | ft²	219,000
Lessee leasing arrangements, operating leases, number of renewal terms | renewal_term	0
Leased square footage under sublease | ft²	132,600
Leased square footage without option for renewal | ft²	87,000
Leased Buildings -6340 Sequence Drive, 6310 Sequence Drive, 6290 Sequence drive
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Lessee leasing arrangements, operating leases, number of renewal terms | renewal_term	2
Leased Buildings -232 South Dobson Road
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Leased square footage | ft²	148,800
Lessee leasing arrangements, operating leases, number of renewal terms | renewal_term	4
Lessee, operating lease, renewal term	5 years

Leases - Components of lease ex

Leases - Components of lease expense (Details) - USD ($) $ in Millions	3 Months Ended	9 Months Ended
	Sep. 30, 2019	Sep. 30, 2019
Finance lease cost:
Amortization of right-of-use assets	$ 0.3	$ 0.8
Interest on lease liabilities	0.2	0.6
Operating lease cost	2.8	8.4
Short-term lease cost	1.3	3.3
Variable lease cost	1	3
Total lease cost	$ 5.6	$ 16.1

Leases - Other information rela

Leases - Other information related to leases (Details) $ in Millions	3 Months Ended	9 Months Ended
	Sep. 30, 2019USD ($)	Sep. 30, 2019USD ($)
Cash paid for amounts included in the measurement of lease liabilities:
Operating cash flows from operating leases	$ 4	$ 10
Operating cash flows from finance leases	0.2	0.6
Financing cash flows from finance leases	0.1	0.4
Right-of-use assets obtained in exchange for lease liabilities:
Operating leases	1.4	41.7
Finance leases	$ 0	$ 15.5
Weighted average remaining lease term in years:
Operating leases	3 years 9 months 18 days	3 years 9 months 18 days
Finance leases	13 years 6 months	13 years 6 months
Weighted average discount rate:
Operating leases	5.00%	5.00%
Finance leases	5.00%	5.00%
Amortization of operating lease right-of-use asset	$ 2.7	$ 6.7

Leases - Future minimum lease p

Leases - Future minimum lease payments under non-cancellable leases (Details) - USD ($) $ in Millions	Sep. 30, 2019	Jan. 01, 2019
Operating Leases
Remaining 2019	$ 4.1
2020	16.9
2021	17.1
2022	6.3
2023	4.4
Thereafter	5.4
Total future lease cost	54.2
Less: Amount representing interest	(4.9)
Present value of future payments	49.3	$ 40.4
Less: Short-term leases not recorded as a liability	(0.2)
Revised present value of future lease payments	49.1
Less: Current portion	(14.8)
Long-term portion	34.3
Finance Leases
Remaining 2019	0.3
2020	1.3
2021	1.3
2022	1.4
2023	1.4
Thereafter	15.3
Total future lease cost	21
Less: Amount representing interest	(5.9)
Present value of future payments	15.1	$ 15.9
Less: Short-term leases not recorded as a liability	0
Revised present value of future lease payments	15.1
Less: Current portion	(0.6)
Long-term portion	$ 14.5

Fair Value Measurements (Detail

Fair Value Measurements (Details) - USD ($)	Sep. 30, 2019	Dec. 31, 2018	Sep. 30, 2018
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Abstract]
Cash equivalents	$ 301,900,000	$ 266,000,000
Debt securities, available-for-sale	1,034,300,000	210,600,000
Transfers between Level 1 and Level 2 securities	0		$ 0
Transfers into or out of Level 3 securities	0		$ 0
Fair Value, Inputs, Level 1
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Abstract]
Cash equivalents	256,900,000	199,300,000
Debt securities, available-for-sale	0	0
Fair Value, Inputs, Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Abstract]
Cash equivalents	45,000,000	66,700,000
Debt securities, available-for-sale	1,034,300,000	210,600,000
Fair Value, Inputs, Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Abstract]
Cash equivalents	0	0
Debt securities, available-for-sale	0	0
U.S. government agencies
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Abstract]
Debt securities, available-for-sale	699,000,000	173,100,000
U.S. government agencies | Fair Value, Inputs, Level 1
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Abstract]
Debt securities, available-for-sale	0	0
U.S. government agencies | Fair Value, Inputs, Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Abstract]
Debt securities, available-for-sale	699,000,000	173,100,000
U.S. government agencies | Fair Value, Inputs, Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Abstract]
Debt securities, available-for-sale	0	0
Commercial paper
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Abstract]
Debt securities, available-for-sale	277,900,000	36,200,000
Commercial paper | Fair Value, Inputs, Level 1
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Abstract]
Debt securities, available-for-sale	0	0
Commercial paper | Fair Value, Inputs, Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Abstract]
Debt securities, available-for-sale	277,900,000	36,200,000
Commercial paper | Fair Value, Inputs, Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Abstract]
Debt securities, available-for-sale	0	0
Corporate debt
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Abstract]
Debt securities, available-for-sale	57,400,000	1,300,000
Corporate debt | Fair Value, Inputs, Level 1
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Abstract]
Debt securities, available-for-sale	0	0
Corporate debt | Fair Value, Inputs, Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Abstract]
Debt securities, available-for-sale	57,400,000	1,300,000
Corporate debt | Fair Value, Inputs, Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Abstract]
Debt securities, available-for-sale	0	0
Foreign Exchange Forward | Designated as Hedging Instrument
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Abstract]
Outstanding currency hedging transactions	0
Fair Value, Measurements, Recurring
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Abstract]
Total assets measured at fair value on a recurring basis	1,336,200,000	514,600,000
Fair Value, Measurements, Recurring | Fair Value, Inputs, Level 1
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Abstract]
Total assets measured at fair value on a recurring basis	256,900,000	237,300,000
Fair Value, Measurements, Recurring | Fair Value, Inputs, Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Abstract]
Total assets measured at fair value on a recurring basis	1,079,300,000	277,300,000
Fair Value, Measurements, Recurring | Fair Value, Inputs, Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Abstract]
Total assets measured at fair value on a recurring basis	$ 0	0
Equity investment in Tandem Diabetes Care, Inc.
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Abstract]
Equity investment in Tandem Diabetes Care, Inc.		38,000,000
Equity investment in Tandem Diabetes Care, Inc. | Fair Value, Inputs, Level 1
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Abstract]
Equity investment in Tandem Diabetes Care, Inc.		38,000,000
Equity investment in Tandem Diabetes Care, Inc. | Fair Value, Inputs, Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Abstract]
Equity investment in Tandem Diabetes Care, Inc.		0
Equity investment in Tandem Diabetes Care, Inc. | Fair Value, Inputs, Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Abstract]
Equity investment in Tandem Diabetes Care, Inc.		$ 0

Fair Value Measurements Fair Va

Fair Value Measurements Fair Value of Convertible Senior Notes (Details) - Senior Notes - USD ($) $ in Millions	Sep. 30, 2019	Dec. 31, 2018
Fair Value Disclosures [Line Items]
Fair value of outstanding senior convertible notes:	$ 1,632.1	$ 1,399.8
Senior convertible notes due 2022
Fair Value Disclosures [Line Items]
Fair value of outstanding senior convertible notes:	635.6	540.2
Senior convertible notes due 2023
Fair Value Disclosures [Line Items]
Fair value of outstanding senior convertible notes:	$ 996.5	$ 859.6

Balance Sheet Details - Short T

Balance Sheet Details - Short Term Marketable Securities, Available for Sale (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2018	Sep. 30, 2019
Debt securities, available for sale:
Amortized Cost	$ 210.7	$ 1,033.9
Gross Unrealized Gains	0	0.5
Gross Unrealized Losses	(0.1)	(0.1)
Estimated Market Value	210.6	1,034.3
Total marketable securities
Cost or Amortized Cost	212.7
Gross Unrealized Gains	36
Gross Unrealized Losses	(0.1)
Estimated Market Value	248.6	1,034.3
U.S. government agencies
Debt securities, available for sale:
Amortized Cost	173.2	698.6
Gross Unrealized Gains	0	0.4
Gross Unrealized Losses	(0.1)	0
Estimated Market Value	173.1	699
Commercial paper
Debt securities, available for sale:
Amortized Cost	36.2	277.9
Gross Unrealized Gains	0	0.1
Gross Unrealized Losses	0	(0.1)
Estimated Market Value	36.2	277.9
Corporate debt
Debt securities, available for sale:
Amortized Cost	1.3	57.4
Gross Unrealized Gains	0	0
Gross Unrealized Losses	0	0
Estimated Market Value	1.3	$ 57.4
Equity investment in Tandem Diabetes Care, Inc.
Equity investment in Tandem Diabetes Care, Inc.
Cost or Amortized Cost	2
Gross Unrealized Gains	36
Gross Unrealized Losses	0
Estimated Market Value	$ 38

Balance Sheet Details - Net Gai

Balance Sheet Details - Net Gain on Equity Method Securities (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018	Dec. 31, 2018
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Net gains and losses recognized during the period on equity securities	$ 0	$ 34.9	$ (4.2)	$ 85
Less: Net gains and losses recognized during the period on equity securities sold during the period	0	(14.1)	4.2	(44.2)
Unrealized gains recognized during the reporting period on equity securities still held at the reporting date	$ 0	$ 20.8	$ 0	$ 40.8
Contractual maturities of debt securities (less than)	12 months		12 months		12 months

Balance Sheet Details - Invento

Balance Sheet Details - Inventory (Detail) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018	Dec. 31, 2018
Raw materials	$ 57.9		$ 57.9		$ 30.8
Work-in-process	8.2		8.2		11.2
Finished goods	54.3		54.3		28.7
Total inventory	120.4		120.4		$ 70.7
Customer Notification Related Inventory Reserve
Inventory write-down	$ 6.8	$ 0.6	$ 10.1	$ 6.1

Balance Sheet Details - Propert

Balance Sheet Details - Property and Equipment (Details) - USD ($) $ in Millions	Sep. 30, 2019	Dec. 31, 2018
Property, Plant and Equipment [Line Items]
Total cost	$ 402.6	$ 262.9
Less accumulated depreciation and amortization	(101.6)	(79.8)
Total property and equipment, net	301	183.1
Building and land
Property, Plant and Equipment [Line Items]
Total cost	15.5	6
Furniture and fixtures
Property, Plant and Equipment [Line Items]
Total cost	12.2	9
Computer software and hardware
Property, Plant and Equipment [Line Items]
Total cost	32.8	29.2
Machinery and equipment
Property, Plant and Equipment [Line Items]
Total cost	97.5	80.7
Leasehold improvements
Property, Plant and Equipment [Line Items]
Total cost	96.6	80.7
Construction in progress
Property, Plant and Equipment [Line Items]
Total cost	$ 148	$ 57.3

Balance Sheet Details - Account

Balance Sheet Details - Accounts Payable and Accrued Liabilities (Detail) - USD ($) $ in Millions	5 Months Ended
	Jun. 30, 2019	Sep. 30, 2019	Dec. 31, 2018
Accounts Payable and Accrued Liabilities [Abstract]
Accounts payable trade		$ 101.4	$ 75.5
Accrued tax, audit, and legal fees		20.3	11.7
Accrued rebates		74.6	36.1
Accrued warranty		7.5	6.8
Restructuring reserve		0.7	0
Other accrued liabilities		27.9	17
Total accounts payable and accrued liabilities		$ 232.4	$ 147.1
Restructuring charges	$ 8

Balance Sheet Details - Other L

Balance Sheet Details - Other Long-Term Liabilities (Details) - USD ($) $ in Millions	Sep. 30, 2019	Dec. 31, 2018
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Finance lease liabilities	$ 14.5	$ 7.3
Deferred rent	0	9.4
Other liabilities	3.1	3.3
Total other long-term liabilities	$ 17.6	$ 20

Debt - Schedule of senior conve

Debt - Schedule of senior convertible notes (Details) - USD ($)	9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Dec. 31, 2018	Nov. 30, 2018	Jun. 30, 2017
Senior Notes [Abstract]
Net carrying amount of Senior Convertible Notes due 2022	$ 1,047,100,000		$ 1,010,300,000
Senior Notes
Senior Notes [Abstract]
Fair value of outstanding senior convertible notes:	1,632,100,000		1,399,800,000
Amount by which the notes' if-converted value exceeds their principal amount:	315,500,000	$ 125,400,000
Senior Notes | Senior convertible notes due 2022
Senior Notes [Abstract]
Principal amount	400,000,000		400,000,000		$ 400,000,000
Unamortized debt discount	(40,700,000)		(51,100,000)
Unamortized debt issuance costs	(5,000,000)		(6,300,000)
Net carrying amount of Senior Convertible Notes due 2022	354,300,000		342,600,000
Fair value of outstanding senior convertible notes:	635,600,000		540,200,000
Amount by which the notes' if-converted value exceeds their principal amount:	221,600,000	125,400,000
Senior Notes | Senior convertible notes due 2023
Senior Notes [Abstract]
Principal amount	850,000,000		850,000,000	$ 850,000,000
Unamortized debt discount	(148,100,000)		(171,800,000)
Unamortized debt issuance costs	(9,100,000)		(10,500,000)
Net carrying amount of Senior Convertible Notes due 2022	692,800,000		667,700,000
Fair value of outstanding senior convertible notes:	996,500,000		859,600,000
Amount by which the notes' if-converted value exceeds their principal amount:	93,900,000	$ 0
Senior Notes | Zero Point Seven Five Percent Senior Convertible Notes
Senior Notes [Abstract]
Total net carrying amount of senior convertible notes	$ 1,047,100,000		$ 1,010,300,000

Debt - Schedule of Interest Exp

Debt - Schedule of Interest Expense, Debt (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018	Jun. 30, 2018
Debt Instrument [Line Items]
Accretion of debt discount			$ 37	$ 11.3
Senior convertible notes due 2022
Debt Instrument [Line Items]
Contractual coupon interest	$ 0.8	$ 0.8	2.3	2.3
Accretion of debt discount	3.5	3.4	10.4	10
Amortization of debt issuance costs	0.4	0.4	1.2	1.2
Total interest expense recognized on senior notes	$ 4.7	4.6	$ 13.9	13.5
Effective interest rate	5.10%		5.10%		5.10%
Senior convertible notes due 2023
Debt Instrument [Line Items]
Contractual coupon interest	$ 1.6	0	$ 4.8	0
Accretion of debt discount	8	0	23.7	0
Amortization of debt issuance costs	0.5	0	1.5	0
Total interest expense recognized on senior notes	$ 10.1	0	$ 30	0
Effective interest rate	5.60%		5.60%		0.00%
Senior Notes | Zero Point Seven Five Percent Senior Convertible Notes
Debt Instrument [Line Items]
Total interest expense recognized on senior notes	$ 14.8	$ 4.6	$ 43.9	$ 13.5

Debt - 0.75% Senior convertible

Debt - 0.75% Senior convertible notes (Details) - Senior Notes	1 Months Ended		9 Months Ended	12 Months Ended
	Nov. 30, 2018USD ($)d$ / sharesshares	Jun. 30, 2017USD ($)$ / shares	Sep. 30, 2019USD ($)d	Dec. 31, 2018USD ($)	Dec. 31, 2017USD ($)
Senior convertible notes due 2022
Debt Instrument [Line Items]
Interest rate on convertible notes		0.75%
Aggregate principal amount		$ 400,000,000	$ 400,000,000	$ 400,000,000
Proceeds from convertible debt		$ 389,000,000
Conversion multiple			$ 1,000
Initial conversion price of convertible notes (in dollars per share) | $ / shares		$ 99.09
Conversion price in event of fundamental change			100.00%
Conversion percentage based on last reported sale price			140.00%
Debt instrument, redemption price, percentage			100.00%
Senior convertible notes due 2023
Debt Instrument [Line Items]
Interest rate on convertible notes	0.75%
Aggregate principal amount	$ 850,000,000		$ 850,000,000	850,000,000
Proceeds from convertible debt	$ 836,600,000
Debt instrument, convertible, conversion ratio	0.0060869	0.0100918
Conversion multiple			$ 1,000
Initial conversion price of convertible notes (in dollars per share) | $ / shares	$ 164.29
Conversion price in event of fundamental change			100.00%
Threshold consecutive trading days | d	60
Conversion percentage based on last reported sale price			130.00%
Debt instrument, redemption price, percentage			100.00%
Warrants sold to counterparties (in shares) | shares	5,200,000
Proceeds from issuance of warrants	$ 183,800,000
Strike price of warrant (in usd per share) | $ / shares	$ 198.38
Additional Paid-In Capital | Senior convertible notes due 2022
Debt Instrument [Line Items]
Amount reclassified to stockholders' equity					$ 72,600,000
Additional Paid-In Capital | Senior convertible notes due 2023
Debt Instrument [Line Items]
Amount reclassified to stockholders' equity				$ 174,400,000
Term of at least 20 trading days during a period of 30 consecutive trading days | Minimum | Senior convertible notes due 2022
Debt Instrument [Line Items]
Threshold consecutive trading days | d			20
Threshold percentage of stock price trigger			130.00%
Term of at least 20 trading days during a period of 30 consecutive trading days | Minimum | Senior convertible notes due 2023
Debt Instrument [Line Items]
Threshold consecutive trading days | d			20
Threshold percentage of stock price trigger			130.00%
Term of at least 20 trading days during a period of 30 consecutive trading days | Maximum | Senior convertible notes due 2022
Debt Instrument [Line Items]
Threshold consecutive trading days | d			30
Term of at least 20 trading days during a period of 30 consecutive trading days | Maximum | Senior convertible notes due 2023
Debt Instrument [Line Items]
Threshold consecutive trading days | d			30
Term of five business day period after any five consecutive trading day period | Senior convertible notes due 2022
Debt Instrument [Line Items]
Threshold consecutive trading days | d			5
Term of five business day period after any five consecutive trading day period | Senior convertible notes due 2023
Debt Instrument [Line Items]
Threshold consecutive trading days | d			5
Term of five business day period after any five consecutive trading day period | Maximum | Senior convertible notes due 2022
Debt Instrument [Line Items]
Threshold consecutive trading days | d			5
Threshold percentage of stock price trigger			98.00%
Term of five business day period after any five consecutive trading day period | Maximum | Senior convertible notes due 2023
Debt Instrument [Line Items]
Threshold consecutive trading days | d			5
Threshold percentage of stock price trigger			98.00%
Designated as Hedging Instrument | Senior convertible notes due 2023
Debt Instrument [Line Items]
Convertible note hedge, number of shares | shares	5,200,000
Cost of convertible note hedge recognized in additional paid-in capital	$ 218,900,000

Debt - Revolving Credit Agreeme

Debt - Revolving Credit Agreement (Details) - USD ($)	1 Months Ended
	Dec. 31, 2018	Sep. 30, 2019
Line of Credit Facility [Line Items]
Line of credit, current		$ 0
Line of credit facility, remaining borrowing capacity		195,600,000
Letter of Credit
Line of Credit Facility [Line Items]
Long-term line of credit		$ 4,400,000
Foreign Currency Line of Credit | Letter of Credit
Line of Credit Facility [Line Items]
Line of credit facility, maximum borrowing capacity	$ 50,000,000
Line of Credit
Line of Credit Facility [Line Items]
Long-term line of credit	200,000,000
Line of credit facility, maximum borrowing capacity	$ 500,000,000
Term of revolving credit agreement	5 years
Line of Credit | Letter of Credit
Line of Credit Facility [Line Items]
Line of credit facility, maximum borrowing capacity	$ 10,000,000
Amount of option to increase the maximum available principal	$ 300,000,000
Minimum | Line of Credit
Line of Credit Facility [Line Items]
Debt instrument, interest rate, stated percentage	0.375%
Line of credit facility, unused capacity, commitment fee percentage	0.20%
Maximum | Line of Credit
Line of Credit Facility [Line Items]
Debt instrument, interest rate, stated percentage	1.00%
Line of credit facility, unused capacity, commitment fee percentage	0.30%
London Interbank Offered Rate (LIBOR) | Minimum | Line of Credit
Line of Credit Facility [Line Items]
Margin on variable rate	1.375%
London Interbank Offered Rate (LIBOR) | Maximum | Line of Credit
Line of Credit Facility [Line Items]
Margin on variable rate	2.00%

Contingencies - Litigation (Det

Contingencies - Litigation (Details)	Sep. 14, 2018number_patentsPetition	Feb. 28, 2018number_patents	Sep. 15, 2017number_patents	Mar. 28, 2016number_patents	Sep. 30, 2019USD ($)
Loss Contingencies [Line Items]
Loss contingencies, patents allegedly infringed, number of inter partes review requested | Petition	2
Loss contingency accrual | $					$ 0
AgaMatrix
Loss Contingencies [Line Items]
Loss contingency, patents allegedly infringed, number				3
Loss contingencies, patents allegedly infringed, number of inter partes review requested	2
WaveForm Technologies, Inc.
Loss Contingencies [Line Items]
Loss contingency, patents allegedly infringed, number transferred to new plaintiff				3
Loss contingencies, patents allegedly infringed, number of inter partes review requested		2
AgaMatrix
Loss Contingencies [Line Items]
Gain contingency, patents allegedly infringed upon, number			2

Income Taxes (Details)

Income Taxes (Details) - USD ($)	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Income Tax Disclosure [Abstract]
Effective tax rate	0.00%	(4.00%)	15.20%	(4.40%)
Tax benefit for refunds of foreign withholding tax, partially offset by state and foreign tax expense			$ 0

Stockholders' Equity - Share-Ba

Stockholders' Equity - Share-Based Compensation Expense (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Share-based Payment Arrangement, Expensed and Capitalized, Amount [Line Items]
Total share-based compensation expense included in net income	$ 24.4	$ 27.1	$ 79.1	$ 77.3
Unrecognized estimated compensation costs	139.8		139.8
Cost of Sales
Share-based Payment Arrangement, Expensed and Capitalized, Amount [Line Items]
Total share-based compensation expense included in net income	2.2	2.5	6.9	7.1
Research and Development Expense
Share-based Payment Arrangement, Expensed and Capitalized, Amount [Line Items]
Total share-based compensation expense included in net income	8.1	8.1	25.8	24.8
Selling General And Administrative
Share-based Payment Arrangement, Expensed and Capitalized, Amount [Line Items]
Total share-based compensation expense included in net income	$ 14.1	$ 16.5	$ 46.4	$ 45.4

Stockholders' Equity - Restrict

Stockholders' Equity - Restricted Stock Units (Details) - USD ($) $ / shares in Units, shares in Millions	9 Months Ended
	Sep. 30, 2019	Sep. 30, 2019	Dec. 31, 2018
Unvested restricted stock units
Shares
Nonvested beginning balance (in shares)	1.8	1.8	2.7
Granted	0.7
Vested	(1.4)
Forfeited	(0.2)
Nonvested ending balance (in shares)	1.8
Weighted Average Grant Date Fair Value
Weighted average grant date fair value beginning of period (in dollars per share)	$ 69.19
Granted	142.87
Vested	68.89
Forfeited	83.09
Weighted average grant date fair value end of period (in dollars per share)	$ 95.06
Aggregate intrinsic value		$ 276,000,000	$ 319,000,000
Total vest date fair value	$ 195,900,000
Performance Shares
Weighted Average Grant Date Fair Value
Total vest date fair value	$ 0

Business Segment and Geograph_3

Business Segment and Geographic Information - Additional Information (Detail) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2019USD ($)	Sep. 30, 2018USD ($)	Sep. 30, 2019USD ($)Geographical_Marketsegment	Sep. 30, 2018USD ($)
Disaggregation of Revenue [Line Items]
Number of reportable segments | segment			1
Number of primary geographical markets | Geographical_Market			2
Revenues	$ 396.3	$ 266.7	$ 1,013.2	$ 693.6
Revenue, percentage	100.00%	100.00%	100.00%	100.00%
United States
Disaggregation of Revenue [Line Items]
Revenues	$ 308.8	$ 202.4	$ 785.6	$ 537.4
Revenue, percentage	78.00%	76.00%	78.00%	77.00%
Outside of the United States
Disaggregation of Revenue [Line Items]
Revenues	$ 87.5	$ 64.3	$ 227.6	$ 156.2
Revenue, percentage	22.00%	24.00%	22.00%	23.00%
Distributor
Disaggregation of Revenue [Line Items]
Revenues	$ 270.4	$ 154.6	$ 680	$ 431.3
Revenue, percentage	68.00%	58.00%	67.00%	62.00%
Direct
Disaggregation of Revenue [Line Items]
Revenues	$ 125.9	$ 112.1	$ 333.2	$ 262.3
Revenue, percentage	32.00%	42.00%	33.00%	38.00%

Uncategorized Items - dxcm-2019

Label	Element	Value
Restricted Cash	us-gaap_RestrictedCash	$ 300,000
Restricted Cash	us-gaap_RestrictedCash	$ 500,000