Fortinet (FTNT) 10-Q 7 May 20 2020 Q1 Quarterly report Financial data

Document and Entity Information

Document and Entity Information - shares	3 Months Ended
	Mar. 31, 2020	May 01, 2020
Cover [Abstract]
Document Type	10-Q
Document Quarterly Report	true
Document Period End Date	Mar. 31, 2020
Document Transition Report	false
Entity File Number	001-34511
Entity Registrant Name	FORTINET, INC.
Entity Incorporation, State or Country Code	DE
Entity Tax Identification Number	77-0560389
Entity Address, Address Line One	899 Kifer Road
Entity Address, City or Town	Sunnyvale
Entity Address, State or Province	CA
Entity Address, Postal Zip Code	94086
City Area Code	408
Local Phone Number	235-7700
Title of 12(b) Security	Common Stock, $0.001 Par Value
Trading Symbol	FTNT
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 Company	false
Entity Shell Company	false
Entity Common Stock, Shares Outstanding		161,648,540
Entity Central Index Key	0001262039
Amendment Flag	false
Document Fiscal Year Focus	2020
Document Fiscal Period Focus	Q1
Current Fiscal Year End Date	--12-31

Condensed Consolidated Balance

Condensed Consolidated Balance Sheets - USD ($) $ in Millions	Mar. 31, 2020	Dec. 31, 2019
CURRENT ASSETS:
Cash and cash equivalents	$ 626.1	$ 1,222.5
Short-term investments	775.2	843.1
Accounts receivable—net	474.7	544.3
Inventory	105	117.9
Prepaid expenses and other current assets	54.3	41.2
Total current assets	2,035.3	2,769
LONG-TERM INVESTMENTS	172	144.3
PROPERTY AND EQUIPMENT—NET	374.2	344.3
DEFERRED CONTRACT COSTS	248.7	237
DEFERRED TAX ASSETS	226.5	232.6
GOODWILL	67.2	67.2
OTHER INTANGIBLE ASSETS—NET	27.1	31.1
OTHER ASSETS	55.2	60
TOTAL ASSETS	3,206.2	3,885.5
CURRENT LIABILITIES:
Accounts payable	87.8	96.4
Accrued liabilities	121.4	101.8
Accrued payroll and compensation	103.6	101.8
Deferred revenue	1,230.2	1,173.6
Total current liabilities	1,543	1,473.6
DEFERRED REVENUE	996.6	962.3
INCOME TAX LIABILITIES	81.3	82.8
OTHER LIABILITIES	49	44.9
Total liabilities	2,669.9	2,563.6
COMMITMENTS AND CONTINGENCIES (Note 11)
STOCKHOLDERS’ EQUITY:
Common stock, $0.001 par value—300 shares authorized; 162.6 and 171.7 shares issued and outstanding at March 31, 2020 and December 31, 2019, respectively	0.2	0.2
Additional paid-in capital	1,128.4	1,180.3
Accumulated other comprehensive income (loss)	(3.1)	1.1
Retained earnings (accumulated deficit)	(589.2)	140.3
Total stockholders’ equity	536.3	1,321.9
TOTAL LIABILITIES AND STOCKHOLDERS’ EQUITY	$ 3,206.2	$ 3,885.5

Condensed Consolidated Statemen

Condensed Consolidated Statements of Income - USD ($) shares in Millions, $ in Millions	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
REVENUE:
Total revenue	$ 576.9	$ 472.6
COST OF REVENUE:
Total cost of revenue	128.7	113
GROSS PROFIT:
Total gross profit	448.2	359.6
OPERATING EXPENSES:
Research and development	80.3	68.6
Sales and marketing	260	215.9
General and administrative	28.8	24.5
Gain on intellectual property matter	(36.8)	0
Total operating expenses	332.3	309
OPERATING INCOME	115.9	50.6
INTEREST INCOME—NET	9.2	10.2
OTHER EXPENSE—NET	(8)	(0.5)
INCOME BEFORE INCOME TAXES	117.1	60.3
PROVISION FOR INCOME TAXES	13.1	1.5
NET INCOME	$ 104	$ 58.8
Net income per share (Note 8):
Basic (in dollars per share)	$ 0.61	$ 0.35
Diluted (in dollars per share)	$ 0.60	$ 0.34
Weighted-average shares outstanding:
Basic (in shares)	170.6	170.2
Diluted (in shares)	174.2	174.8
Product [Member]
REVENUE:
Total revenue	$ 192.3	$ 162.7
COST OF REVENUE:
Total cost of revenue	76.3	70.2
GROSS PROFIT:
Total gross profit	116	92.5
Service [Member]
REVENUE:
Total revenue	384.6	309.9
COST OF REVENUE:
Total cost of revenue	52.4	42.8
GROSS PROFIT:
Total gross profit	$ 332.2	$ 267.1

Condensed Consolidated Balanc_2

Condensed Consolidated Balance Sheets Parenthetical - $ / shares	Mar. 31, 2020	Dec. 31, 2019
Common Stock, par value (dollars per share)	$ 0.001	$ 0.001
Common Stock, shares authorized	300,000,000	300,000,000
Common Stock, shares issued	162,600,000	171,700,000
Common Stock, shares outstanding	162,600,000	171,700,000

Condensed Consolidated Statem_2

Condensed Consolidated Statements of Comprehensive Income - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
Net income	$ 104	$ 58.8
Other comprehensive income (loss):
Change in unrealized gains (losses) on investments	(5.2)	1
Less: tax provision (benefit) related to change in unrealized gains (losses) on investments	(1)	0.3
Other comprehensive income (loss)	(4.2)	0.7
Comprehensive income	$ 99.8	$ 59.5

Condensed Consolidated Statem_3

Condensed Consolidated Statements of Stockholders' Equity - USD ($) shares in Millions, $ in Millions	Total	Common Stock [Member]	Additional Paid-in Capital [Member]	Accumulated Other Comprehensive Income (Loss) [Member]	Retained Earnings (Accumulated Deficit) [Member]
Balance, shares at Dec. 31, 2018		169.8
Balance at Dec. 31, 2018	$ 1,010.2	$ 0.2	$ 1,068.3	$ (0.8)	$ (57.5)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Issuance of common stock in connection with equity incentive plans - net of tax withholding (in shares)		1.7
Issuance of common stock in connection with equity incentive plans - net of tax withholding	1.6		1.6
Repurchase and retirement of common stock (in shares)		(0.8)
Repurchase and retirement of common stock	(56.2)		(4.8)		(51.4)
Stock-based compensation expense	43		43
Net unrealized gain (loss) on investments - net of tax	0.7			0.7
Net income	58.8				58.8
Balance, shares at Mar. 31, 2019		170.7
Balance at Mar. 31, 2019	1,058.1	$ 0.2	1,108.1	(0.2)	(50)
Balance, shares at Dec. 31, 2019		171.7
Balance at Dec. 31, 2019	1,321.9	$ 0.2	1,180.3	1.1	140.3
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Issuance of common stock in connection with equity incentive plans - net of tax withholding (in shares)		0.9
Issuance of common stock in connection with equity incentive plans - net of tax withholding	(30.3)		(30.3)
Repurchase and retirement of common stock (in shares)		(10)
Repurchase and retirement of common stock	(899.9)		(66.4)		(833.5)
Stock-based compensation expense	44.8		44.8
Net unrealized gain (loss) on investments - net of tax	(4.2)			(4.2)
Net income	104
Balance, shares at Mar. 31, 2020		162.6
Balance at Mar. 31, 2020	$ 536.3	$ 0.2	$ 1,128.4	$ (3.1)	$ (589.2)

Condensed Consolidated Statem_4

Condensed Consolidated Statements of Cash Flows - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
CASH FLOWS FROM OPERATING ACTIVITIES:
Net income	$ 104	$ 58.8
Adjustments to reconcile net income to net cash provided by operating activities:
Stock-based compensation	44.8	43
Amortization of deferred contract costs	31.3	25.1
Depreciation and amortization	17.6	15.7
Amortization of investment premiums (discounts)	(0.6)	(1.1)
Other	4.3	0.3
Changes in operating assets and liabilities:
Accounts receivable—net	69.6	63.6
Inventory	6.7	(2.6)
Prepaid expenses and other current assets	(12.9)	(5.9)
Deferred contract costs	(43)	(32.9)
Deferred tax assets	7.1	(8)
Other assets	0.9	0.1
Accounts payable	(9)	(18)
Accrued liabilities	1.8	3.2
Accrued payroll and compensation	1.8	(18.1)
Other liabilities	4.1	(0.9)
Deferred revenue	90.9	79
Net cash provided by operating activities	319.4	201.3
CASH FLOWS FROM INVESTING ACTIVITIES:
Purchases of investments	(368.3)	(264.5)
Sales of investments	126.8	8.1
Maturities of investments	277.2	227.6
Purchases of property and equipment	(27.6)	(10.2)
Payments made in connection with business combination, net of cash acquired	(3.1)	0
Other	(0.4)	0
Net cash provided by (used in) investing activities	4.6	(39)
CASH FLOWS FROM FINANCING ACTIVITIES:
Repurchase and retirement of common stock	(889.9)	(60.4)
Proceeds from issuance of common stock	7.4	34.6
Taxes paid related to net share settlement of equity awards	(37.8)	(32)
Other	(0.1)	0
Net cash used in financing activities	(920.4)	(57.8)
NET INCREASE (DECREASE) IN CASH AND CASH EQUIVALENTS	(596.4)	104.5
CASH AND CASH EQUIVALENTS—Beginning of period	1,222.5	1,112.4
CASH AND CASH EQUIVALENTS—End of period	626.1	1,216.9
SUPPLEMENTAL DISCLOSURES OF CASH FLOW INFORMATION:
Operating lease liabilities arising from obtaining right-of-use assets	2.4	3.5
Cash paid to settle liability incurred for repurchase of common stock	0	4.2
NON-CASH INVESTING AND FINANCING ACTIVITIES:
Transfers of evaluation units from inventory to property and equipment	6.3	4.3
Liability for purchase of property and equipment and asset retirement obligations	25.9	7.6
Liability incurred for repurchase of common stock	$ 10	$ 0

Summary of Significant Accounti

Summary of Significant Accounting Policies	3 Months Ended
	Mar. 31, 2020
Accounting Policies [Abstract]
SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES	SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES Basis of Presentation and Preparation —The unaudited condensed consolidated financial statements of Fortinet, Inc. and its wholly owned subsidiaries (collectively, “we,” “us” or “our”) have been prepared in accordance with generally accepted accounting principles in the United States (“ GAAP ”) for interim financial information, as well as the instructions to Form 10-Q pursuant to the rules and regulations of the U.S. Securities and Exchange Commission (the “ SEC ”). Accordingly, they do not include all of the information and footnotes required by GAAP for complete financial statements, and should be read in conjunction with our audited consolidated financial statements as of and for the year ended December 31, 2019, contained in our Annual Report on Form 10-K filed with the SEC on February 26, 2020. In the opinion of management, all adjustments, which includes normal recurring adjustments, considered necessary for a fair presentation have been included. All intercompany balances, transactions and cash flows have been eliminated. The results of operations for the three months ended March 31, 2020 are not necessarily indicative of the results for the full year or for any future periods. The condensed consolidated balance sheet as of December 31, 2019 is derived from the audited consolidated financial statements for the year ended December 31, 2019. For 2020, the amounts previously reported as Income taxes payable are included in Accrued liabilities. Prior periods have been reclassified to conform with current period presentation. The preparation of financial statements in accordance with GAAP requires management to make estimates and assumptions that affect the amounts reported in the condensed consolidated financial statements and accompanying notes. Actual results could differ materially from those estimates. There have been no material changes to our significant accounting policies as of and for the three months ended March 31, 2020 . Recently Adopted Accounting Standards Financial Instruments In June 2016, the Financial Accounting Standards Board (“FASB”) issued Accounting Standards Update (“ASU”) 2016-13—Financial Instruments—Credit Losses (Topic 326): Measurement of Credit Losses on Financial Instruments (“ Topic 326 ”), which provides guidance on how an entity should measure credit losses on financial instruments. The standard replaces the existing incurred loss model with an expected credit loss model for financial assets measured at amortized cost, including trade receivables, and requires that credit losses on available-for-sale debt securities be presented as an allowance rather than as a write-down. The new approach to estimating credit losses (referred to as the current expected credit losses model) generally accelerates recognition of credit losses. We adopted Topic 326 on January 1, 2020 using the modified retrospective method. The adoption of this standard did not have a material impact on our condensed consolidated financial statements. Cloud Computing In August 2018, the FASB issued ASU 2018-15—Intangibles—Goodwill and Other—Internal-Use Software (Subtopic 350-40): Customer’s Accounting for Implementation Costs Incurred in a Cloud Computing Arrangement That Is a Service Contract, which requires a customer in a cloud computing arrangement that is a service contract to follow the internal-use software guidance in Accounting Standards Codification (“ ASC ”) Topic 350, Intangibles—Goodwill and Other, to determine which implementation costs to capitalize as assets or expense as incurred. We adopted ASU 2018-15 on January 1, 2020. The adoption of this standard did not have a material impact on our condensed consolidated financial statements. Fair Value Measurements In August 2018, the FASB issued ASU 2018-13—Fair Value Measurement (Topic 820): Disclosure Framework—Changes to the Disclosure Requirements for Fair Value Measurement, which eliminates, adds and modifies certain disclosure requirements for fair value measurements in ASC 820, Fair Value Measurement, as part of its disclosure framework project. We adopted ASU 2018-13 on January 1, 2020. The adoption of this standard did not have a material impact on our disclosures. Recent Accounting Standards Not Yet Effective Income Taxes In December 2019, the FASB issued ASU 2019-12—Income Taxes (Topic 740): Simplifying the Accounting for Income Taxes. The amendments in ASU 2019-12 simplify the accounting for income taxes by removing certain exceptions to the general principles in Topic 740. The amendments also improve consistent application and simplification of GAAP for other areas of Topic 740 by clarifying and amending existing guidance. ASU 2019-12 is effective for us beginning on January 1, 2021. Early adoption of the amendments is permitted. We are currently evaluating the impact of ASU 2019-12 on our condensed consolidated financial statements.

Revenue Recognition

Revenue Recognition	3 Months Ended
	Mar. 31, 2020
Revenue from Contract with Customer [Abstract]
Revenue Recognition	REVENUE RECOGNITION Our revenue consists of product and service revenue. Product revenue is generated by sales of our FortiGate products and other hardware and software solutions. Service revenue relates to sales of our FortiGuard security subscription, FortiCare technical support services and other services. Disaggregation of Revenue The following table presents our revenue disaggregated by major product and service lines (in millions): Three Months Ended March 31, March 31, Product $ 192.3 $ 162.7 Service: Security subscription 211.4 169.6 Technical support and other 173.2 140.3 Total service revenue 384.6 309.9 Total revenue $ 576.9 $ 472.6 Deferred Revenue During the three months ended March 31, 2020 and March 31, 2019 , we recognized $348.9 million and $288.6 million in service revenue that was included in the deferred revenue balance as of December 31, 2019 and December 31, 2018, respectively. Transaction Price Allocated to the Remaining Performance Obligations As of March 31, 2020 , the aggregate amount of the transaction price allocated to remaining performance obligations was $2.23 billion , which was substantially comprised of deferred security subscription and technical support services revenue. We expect to recognize approximately $1.23 billion as revenue over the next 12 months and the remainder thereafter. Accounts Receivable Trade accounts receivable are recorded at the invoiced amount. On January 1, 2020, we adopted Topic 326 , which provides guidance on how to measure credit losses on financial instruments, including accounts receivable. Prior to our adoption of Topic 326 , our accounts receivable balance was reduced by an allowance for doubtful accounts that we determined based on our assessment of the collectability of customer accounts. Under Topic 326 , our accounts receivable balance is reduced by an allowance for credit losses. We measure expected credit losses of accounts receivable on a collective (pool) basis, aggregating accounts receivable that are either current or no more than 60 days past due, and aggregating accounts receivable that are more than 60 days past due. We apply a credit-loss percentage to each of the pools that is based on our historical credit losses. We review whether each of our significant accounts receivable that is more than 60 days past due continues to exhibit similar risk characteristics with the other accounts receivable in the pool. If we determine that it does not, we evaluate it for expected credit losses on an individual basis. The COVID-19 pandemic and the recent economic downturn prompted us to perform additional credit reviews of our existing customers, including obtaining recent credit reports and reviewing their latest available statements of financial position. After performing our additional reviews, we determined that, while there may be delays in our collections, the risk of credit loss on our trade accounts receivable as of March 31, 2020 was expected to be consistent with prior periods and that our methodology for estimating credit losses was appropriate. The allowance for credit losses was $1.1 million as of March 31, 2020 , and the allowance for doubtful accounts was $1.2 million as of December 31, 2019. Provisions, write-offs and recoveries were not material during the three months ended March 31, 2020 . Deferred Contract Costs Sales commissions earned by our sales force are considered incremental and recoverable costs of obtaining a contract with a customer. The amortization of deferred contract costs is included in sales and marketing expense in our condensed consolidated statements of income. Amortization of deferred contract costs during the three months ended March 31, 2020 and March 31, 2019 were $31.3 million and $25.1 million , respectively.

Financial Instruments and Fair

Financial Instruments and Fair Value	3 Months Ended
	Mar. 31, 2020
Financial Instruments and Fair Value [Abstract]
FINANCIAL INSTRUMENTS AND FAIR VALUE	FINANCIAL INSTRUMENTS AND FAIR VALUE The following tables summarize our investments (in millions): March 31, 2020 Amortized Cost Unrealized Gains Unrealized Losses Fair Value Corporate debt securities $ 616.3 $ 0.3 $ (4.2 ) $ 612.4 Commercial paper 150.6 0.1 (0.1 ) 150.6 U.S. government securities 96.6 0.5 — 97.1 Certificates of deposit and term deposits (1) 87.7 0.1 (0.7 ) 87.1 Total available-for-sale securities $ 951.2 $ 1.0 $ (5.0 ) $ 947.2 December 31, 2019 Amortized Cost Unrealized Gains Unrealized Losses Fair Value Corporate debt securities $ 576.1 $ 1.0 $ (0.1 ) $ 577.0 Commercial paper 148.7 0.1 — 148.8 U.S. government securities 195.0 0.2 — 195.2 Certificates of deposit and term deposits (1) 66.4 — — 66.4 Total available-for-sale securities $ 986.2 $ 1.3 $ (0.1 ) $ 987.4 (1) The majority of our certificates of deposit and term deposits are foreign deposits. The following tables show the gross unrealized losses and the related fair values of our investments that have been in a continuous unrealized loss position (in millions): March 31, 2020 Less Than 12 Months 12 Months or Greater Total Fair Value Unrealized Losses Fair Value Unrealized Losses Fair Value Unrealized Losses Corporate debt securities $ 475.2 $ (4.2 ) $ 7.1 $ — $ 482.3 $ (4.2 ) Commercial paper 45.5 (0.1 ) — — 45.5 (0.1 ) Certificates of deposit and term deposits 49.1 (0.7 ) — — 49.1 (0.7 ) Total available-for-sale securities $ 569.8 $ (5.0 ) $ 7.1 $ — $ 576.9 $ (5.0 ) December 31, 2019 Less Than 12 Months 12 Months or Greater Total Fair Value Unrealized Losses Fair Value Unrealized Losses Fair Value Unrealized Losses Corporate debt securities $ 117.3 $ (0.1 ) $ 16.1 $ — $ 133.4 $ (0.1 ) Commercial paper 26.0 — — — 26.0 — U.S. government securities 47.1 — — — 47.1 — Certificates of deposit and term deposits 13.0 — — — 13.0 — Total available-for-sale securities $ 203.4 $ (0.1 ) $ 16.1 $ — $ 219.5 $ (0.1 ) The contractual maturities of our investments were as follows (in millions): March 31, December 31, Due within one year $ 775.2 $ 843.1 Due within one to three years 172.0 144.3 Total $ 947.2 $ 987.4 Available-for-sale securities are reported at fair value, with unrealized gains and losses and the related tax impact included as a separate component of stockholders’ equity and in comprehensive income. Accrued interest of $4.7 million as of March 31, 2020 is excluded from both the fair value and the amortized cost of our available-for-sale securities and is recorded in Prepaid expenses and other current assets in our condensed consolidated balance sheet. We have elected to not record an allowance for credit losses for accrued interest for available-for-sale securities and will reverse the accrued interest against interest income in the period in which we determine the accrued interest to be uncollectible. Prior to 2020, we followed the guidance in ASC 320 Investments—Debt and Equity Securities in determining whether unrealized losses were other than temporary. We adopted Topic 326 on January 1, 2020, and now consider whether unrealized losses have resulted from a credit loss or other factors. The unrealized losses on our available-for-sale securities as of March 31, 2020 and as of December 31, 2019 were caused by fluctuations in market value and interest rates as a result of the economic environment. We concluded that an allowance for credit losses was unnecessary as of March 31, 2020 and that the impairments as of December 31, 2019 were not other than temporary because (i) the decline in market value was attributable to changes in market conditions and not credit quality, and (ii) we concluded that neither do we intend to sell nor is it more likely than not that we will be required to sell these investments prior to recovery of their amortized cost basis. Realized losses on available-for-sale securities were insignificant in the periods presented and are included in Other expense—net in our consolidated statements of income. We use the specific identification method to determine the cost basis of investments sold. Fair Value Accounting—We apply the following fair value hierarchy for disclosure of the inputs used to measure fair value. This hierarchy prioritizes the inputs into three broad levels as follows: Level 1—Inputs are unadjusted quoted prices in active markets for identical assets or liabilities. Level 2—Inputs are quoted prices for similar assets and liabilities in active markets or inputs that are observable for the assets or liabilities, either directly or indirectly through market corroboration, for substantially the full term of the financial instruments. Level 3—Unobservable inputs based on our own assumptions used to measure assets and liabilities at fair value. The inputs require significant management judgment or estimation. We measure the fair value of money market funds and certain U.S. government securities using quoted prices in active markets for identical assets. The fair value of all other financial instruments was based on quoted prices for similar assets in active markets, or model-driven valuations using significant inputs derived from or corroborated by observable market data. We classify investments within Level 1 if quoted prices are available in active markets for identical securities. We classify items within Level 2 if the investments are valued using model-driven valuations using observable inputs such as quoted market prices, benchmark yields, reported trades, broker/dealer quotes or alternative pricing sources with reasonable levels of price transparency. Investments are held by custodians who obtain investment prices from a third-party pricing provider that incorporates standard inputs in various asset price models. Fair Value of Financial Instruments Assets Measured at Fair Value on a Recurring Basis The following tables present the fair value of our financial assets measured at fair value on a recurring basis as of March 31, 2020 and December 31, 2019 (in millions): March 31, 2020 December 31, 2019 Aggregate Fair Value Quoted Prices in Active Markets For Identical Assets Significant Other Observable Remaining Inputs Significant Other Unobservable Remaining Inputs Aggregate Fair Value Quoted Prices in Active Markets For Identical Assets Significant Other Observable Remaining Inputs Significant Other Unobservable Remaining Inputs (Level 1) (Level 2) (Level 3) (Level 1) (Level 2) (Level 3) Assets: Corporate debt securities $ 613.4 $ — $ 613.4 $ — $ 577.0 $ — $ 577.0 $ — Commercial paper 164.6 — 164.6 — 165.8 — 165.8 — Certificates of deposit and term deposits 87.1 — 87.1 — 66.4 — 66.4 — U.S. government securities 97.1 97.1 — — 195.2 195.2 — — Money market funds 163.7 163.7 — — 15.0 15.0 — — Total $ 1,125.9 $ 260.8 $ 865.1 $ — $ 1,019.4 $ 210.2 $ 809.2 $ — Reported as: Cash equivalents $ 178.7 $ 32.0 Short-term investments 775.2 843.1 Long-term investments 172.0 144.3 Total $ 1,125.9 $ 1,019.4 There were no transfers between Level 1 and Level 2 of the fair value hierarchy during the three months ended March 31, 2020 and year ended December 31, 2019 .

Inventory

Inventory	3 Months Ended
	Mar. 31, 2020
Inventory Disclosure [Abstract]
INVENTORY	INVENTORY Inventory consisted of the following (in millions): March 31, December 31, Raw materials $ 12.5 $ 9.7 Finished goods 92.5 108.2 Inventory $ 105.0 $ 117.9

Property and Equipment_Net

Property and Equipment—Net	3 Months Ended
	Mar. 31, 2020
Property, Plant and Equipment [Abstract]
PROPERTY AND EQUIPMENT—Net	PROPERTY AND EQUIPMENT—Net Property and equipment—net consisted of the following (in millions): March 31, December 31, Land $ 93.3 $ 93.3 Building and building improvements 148.0 147.4 Computer equipment and software 121.7 116.7 Leasehold improvements 26.8 25.5 Evaluation units 22.4 19.9 Furniture and fixtures 18.2 17.3 Construction-in-progress 90.7 61.2 Total property and equipment 521.1 481.3 Less: accumulated depreciation (146.9 ) (137.0 ) Property and equipment—net $ 374.2 $ 344.3 Depreciation expense was $13.6 million and $12.7 million during the three months ended March 31, 2020 and March 31, 2019 , respectively.

Investments in Privately-Held C

Investments in Privately-Held Companies	3 Months Ended
	Mar. 31, 2020
Investments, All Other Investments [Abstract]
INVESTMENTS IN PRIVATELY-HELD COMPANIES	INVESTMENTS IN PRIVATELY HELD COMPANIES Our investments in the equity securities of privately held companies totaled $1.0 million and $5.3 million as of March 31, 2020 and December 31, 2019 , respectively. These investments are accounted for at cost, adjusted for changes in observable prices minus impairment. We own less than 20% of the voting securities in each of these investments and do not have the ability to exercise significant influence over operating and financial policies of the respective entities. These investments are recorded as Other assets in our condensed consolidated balance sheets and would be measured at fair value if indicators of an increase in value or impairment existed. During the three months ended March 31, 2020, we determined that one investment was impaired. As a result, we recognized and included a non-cash impairment charge of $4.3 million in Other expense—net in our condensed consolidated statements of income. As of March 31, 2020 , no other events have occurred that would affect the carrying value of these investments.

Goodwill and Other Intangible A

Goodwill and Other Intangible Assets - Net	3 Months Ended
	Mar. 31, 2020
Goodwill and Intangible Assets Disclosure [Abstract]
GOODWILL AND OTHER INTANGIBLE ASSETS - Net	GOODWILL AND OTHER INTANGIBLE ASSETS—Net Goodwill As of March 31, 2020 and December 31, 2019 , we had goodwill of $67.2 million . There were no impairments to goodwill during the three months ended March 31, 2020 or during prior periods. Other Intangible Assets—Net The following tables present other intangible assets—net as of March 31, 2020 and December 31, 2019 (in millions, except years): March 31, 2020 Weighted-Average Useful Life (in Years) Gross Accumulated Amortization Net Other intangible assets—net: Finite-lived intangible assets: Developed technologies 4.0 $ 48.8 $ 25.8 $ 23.0 Customer relationships 4.1 21.6 17.5 4.1 Total other intangible assets—net $ 70.4 $ 43.3 $ 27.1 December 31, 2019 Weighted-Average Useful Life (in Years) Gross Accumulated Amortization Net Other intangible assets—net: Finite-lived intangible assets: Developed technologies 4.0 $ 50.2 $ 24.6 $ 25.6 Customer relationships 4.1 21.6 16.1 5.5 Total other intangible assets—net $ 71.8 $ 40.7 $ 31.1 Amortization expense was $4.0 million and $3.0 million during the three months ended March 31, 2020 and March 31, 2019 , respectively. The following table summarizes estimated future amortization expense of finite-lived intangible assets—net (in millions): Amount Years: 2020 (the remainder of 2020) $ 8.7 2021 8.3 2022 6.4 2023 3.7 Total $ 27.1

Net Income Per Share

Net Income Per Share	3 Months Ended
	Mar. 31, 2020
Earnings Per Share [Abstract]
NET INCOME PER SHARE	NET INCOME PER SHARE Basic net income per share is computed by dividing net income by the weighted-average number of shares of common stock outstanding during the period. Diluted net income per share is computed by dividing net income by the weighted-average number of shares of common stock outstanding during the period, plus the dilutive effects of restricted stock units (“ RSU s”) and stock options. Dilutive shares of common stock are determined by applying the treasury stock method. A reconciliation of the numerator and denominator used in the calculation of basic and diluted net income per share is as follows (in millions, except per share amounts): Three Months Ended March 31, March 31, Numerator: Net income $ 104.0 $ 58.8 Denominator: Basic shares: Weighted-average common stock outstanding-basic 170.6 170.2 Diluted shares: Weighted-average common stock outstanding-basic 170.6 170.2 Effect of potentially dilutive securities: RSUs 2.4 3.3 Stock options 1.2 1.3 Weighted-average shares used to compute diluted net income per share 174.2 174.8 Net income per share: Basic $ 0.61 $ 0.35 Diluted $ 0.60 $ 0.34 The following weighted-average shares of common stock were excluded from the computation of diluted net income per share for the periods presented, as their effect would have been antidilutive (in millions): Three Months Ended March 31, March 31, RSUs 0.6 0.7 Stock options 0.3 0.3 Total 0.9 1.0

Leases

Leases	3 Months Ended
	Mar. 31, 2020
Leases [Abstract]
LEASES	LEASES We have operating leases for offices, research and development facilities and data centers. Our leases have remaining terms that range from less than one year to approximately seven years , some of which include one or more options to renew, with renewal terms of up to five years . We do not include renewal options in our lease terms for calculating our lease liability, as the renewal options allow us to maintain operational flexibility and we are not reasonably certain we will exercise these renewal options at the time of the lease commencement. During the year ended December 31, 2019, we entered into a finance lease with $3.6 million lease liabilities arising from obtaining right-of-use assets with a lease term of approximately two years . Our remaining finance leases were not material to our condensed consolidated financial statements. The related assumptions and further disclosures for finance leases are not material. The components of lease expense were as follows (in millions): Three Months Ended Three Months Ended March 31, March 31, Operating lease expense $ 4.3 $ 3.6 Variable lease expense (1) 0.6 0.6 Short-term lease expense 0.9 0.7 Total lease expense $ 5.8 $ 4.9 (1) Variable lease expense for the three months ended March 31, 2020 and March 31, 2019 predominantly included common area maintenance charges and parking expense. Supplemental balance sheet information related to our operating leases was as follows (in millions, except lease term and discount rate): Classification March 31, December 31, Operating lease ROU assets - non-current Other assets $ 42.7 $ 44.3 Operating lease liabilities - current Accrued liabilities $ 14.8 $ 15.5 Operating lease liabilities - non-current Other liabilities 28.3 30.6 Total operating lease liabilities $ 43.1 $ 46.1 Weighted average remaining lease term in years - operating leases 3.6 3.7 Weighted average discount rate - operating leases 2.8 % 2.8 % Supplemental cash flow information related to leases was as follows (in millions): Three Months Ended Three Months Ended March 31, March 31, Cash paid for amounts included in the measurement of lease liabilities Operating cash flows used for operating leases $ 4.6 $ 4.6 Lease liabilities arising from obtaining right-of-use assets Operating leases $ 2.4 $ 3.5 Maturities of operating lease liabilities as of March 31, 2020 were as follows (in millions): Year ending December 31, Amount 2020 (the remainder of 2020) $ 11.9 2021 13.6 2022 8.7 2023 5.4 2024 3.9 Thereafter 1.8 Total lease payments 45.3 Less imputed interest (2.2 ) Total $ 43.1 As of March 31, 2020 , we had additional minimum lease payments of $5.1 million relating to operating leases that had been signed but had not yet commenced and therefore were excluded from the table above. These leases will commence during 2020 and will have lease terms of approximately five to seven years .
LEASES	LEASES We have operating leases for offices, research and development facilities and data centers. Our leases have remaining terms that range from less than one year to approximately seven years , some of which include one or more options to renew, with renewal terms of up to five years . We do not include renewal options in our lease terms for calculating our lease liability, as the renewal options allow us to maintain operational flexibility and we are not reasonably certain we will exercise these renewal options at the time of the lease commencement. During the year ended December 31, 2019, we entered into a finance lease with $3.6 million lease liabilities arising from obtaining right-of-use assets with a lease term of approximately two years . Our remaining finance leases were not material to our condensed consolidated financial statements. The related assumptions and further disclosures for finance leases are not material. The components of lease expense were as follows (in millions): Three Months Ended Three Months Ended March 31, March 31, Operating lease expense $ 4.3 $ 3.6 Variable lease expense (1) 0.6 0.6 Short-term lease expense 0.9 0.7 Total lease expense $ 5.8 $ 4.9 (1) Variable lease expense for the three months ended March 31, 2020 and March 31, 2019 predominantly included common area maintenance charges and parking expense. Supplemental balance sheet information related to our operating leases was as follows (in millions, except lease term and discount rate): Classification March 31, December 31, Operating lease ROU assets - non-current Other assets $ 42.7 $ 44.3 Operating lease liabilities - current Accrued liabilities $ 14.8 $ 15.5 Operating lease liabilities - non-current Other liabilities 28.3 30.6 Total operating lease liabilities $ 43.1 $ 46.1 Weighted average remaining lease term in years - operating leases 3.6 3.7 Weighted average discount rate - operating leases 2.8 % 2.8 % Supplemental cash flow information related to leases was as follows (in millions): Three Months Ended Three Months Ended March 31, March 31, Cash paid for amounts included in the measurement of lease liabilities Operating cash flows used for operating leases $ 4.6 $ 4.6 Lease liabilities arising from obtaining right-of-use assets Operating leases $ 2.4 $ 3.5 Maturities of operating lease liabilities as of March 31, 2020 were as follows (in millions): Year ending December 31, Amount 2020 (the remainder of 2020) $ 11.9 2021 13.6 2022 8.7 2023 5.4 2024 3.9 Thereafter 1.8 Total lease payments 45.3 Less imputed interest (2.2 ) Total $ 43.1 As of March 31, 2020 , we had additional minimum lease payments of $5.1 million relating to operating leases that had been signed but had not yet commenced and therefore were excluded from the table above. These leases will commence during 2020 and will have lease terms of approximately five to seven years .

Mutual Covenant-Not-to-Sue and

Mutual Covenant-Not-to-Sue and Release Agreement	3 Months Ended
	Mar. 31, 2020
Mutual Covenant-Not-to-Sue Agreement [Abstract]
MUTUAL COVENANT-NOT-TO-SUE AND RELEASE AGREEMENT	MUTUAL COVENANT-NOT-TO-SUE AND RELEASE AGREEMENT In January 2020, we entered into an agreement with a competitor in the network security industry whereby, in February 2020, the competitor party paid us a lump sum of $50.0 million for a seven-year mutual covenant-not-to-sue for patent claims. Pursuant to this agreement, at the end of this first seven-year period, either party may extend the agreement for an additional seven-year mutual covenant-not-to-sue in return for this competitor paying us an additional $50.0 million . This agreement arose after expiration of previous agreements between the parties whereby the competitor had paid us sums for a limited term license to certain of our intellectual property (“ IP ”) and a limited term mutual covenant-not-to-sue. We concluded that the agreement was a 14 -year contract with a total transaction price of $100.0 million , and that it contained two material distinct performance obligations: (1) the right to use our existing patents, and (2) the right to use any patents that we develop over the term of the contract. We allocated $36.0 million to the functional patents, which was recognized upon commencement of the contract; the remaining $64.0 million , representing the right to utilize future patents, will be recognized over the contract term. We further concluded that our existing patents represent functional IP that should be recognized upon granting our competitor access. We also concluded that the right to receive additional functional IP that we will develop in the future represents a stand ready obligation. Therefore, the transaction price allocated to this obligation is recognized ratably over the 14 -year contract term. We estimated the stand-alone selling price of each distinct performance obligation and allocated the $100.0 million transaction price. During the three months ended March 31, 2020 , we recorded $36.8 million in Gain on IP matter in our condensed consolidated statement of income, consisting of the $36.0 million allocated to the functional patents and $0.8 million of amortization of the deferred component. We recorded $13.2 million in Accrued liabilities and Other liabilities in our condensed consolidated balance sheet as of March 31, 2020 .

Commitments and Contingencies

Commitments and Contingencies	3 Months Ended
	Mar. 31, 2020
Commitments and Contingencies Disclosure [Abstract]
COMMITMENTS AND CONTINGENCIES	COMMITMENTS AND CONTINGENCIES The following table summarizes our inventory purchase commitments as of March 31, 2020 (in millions): Total 2020 2021 2022 2023 2024 Thereafter Inventory purchase commitments $ 247.2 $ 247.2 $ — $ — $ — $ — $ — Inventory Purchase Commitments —Our independent contract manufacturers procure components and build our products based on our forecasts. These forecasts are based on estimates of future demand for our products, which are in turn based on historical trends and an analysis from our sales and marketing organizations, adjusted for overall market conditions. In order to reduce manufacturing lead times and plan for adequate component supply, we may issue purchase orders to some of our independent contract manufacturers, which may not be cancelable. As of March 31, 2020 , we had $247.2 million of open purchase orders with our independent contract manufacturers that may not be cancelable. Other Contractual Commitments and Open Purchase Orders —In addition to commitments with contract manufacturers, we have open purchase orders and contractual obligations in the ordinary course of business for which we have not received goods or services. As of March 31, 2020 , we had $10.9 million in other contractual commitments having a remaining term in excess of one year that may not be cancelable. Litigation —We are involved in disputes, litigation, and other legal actions. For lawsuits where we are the defendant, we are in the process of defending these litigation matters, and while there can be no assurances and the outcome of certain of these matters is currently not determinable and not predictable, we currently are unaware of any existing claims or proceedings that we believe are likely to have a material adverse effect on our financial position. There are many uncertainties associated with any litigation and these actions or other third-party claims against us may cause us to incur costly litigation fees, costs and substantial settlement charges, and possibly subject us to damages and other penalties. In addition, the resolution of any IP litigation may require us to make royalty payments, which could adversely affect our gross margins in future periods. If any of those events were to occur, our business, financial condition, results of operations, and cash flows could be adversely affected. Litigation is unpredictable and the actual liability in any such matters may be materially different from our current estimates, which could result in the need to adjust any accrued liability and record additional expenses. We accrue for contingencies when we believe that a loss is probable and that we can reasonably estimate the amount of any such loss. Indemnification and Other Matters —Under the indemnification provisions of our standard sales contracts, we agree to defend our customers against third-party claims asserting various allegations such as product defects and infringement of certain IP rights, which may include patents, copyrights, trademarks or trade secrets, and to pay judgments entered on such claims. In some contracts, our exposure under these indemnification provisions is limited by the terms of the contracts to certain defined limits, such as the total amount paid by our customer under the agreement. However, certain agreements include covenants, penalties and indemnification provisions including and beyond indemnification for third-party claims of IP infringement, that could potentially expose us to losses in excess of the amount received under the agreement, and in some instances to potential liability that is not contractually limited. To date, although from time to time there are indemnification claims asserted against us and currently there are pending indemnification claims, there have been no material awards under such indemnification provisions. Periodically, we, like other security companies and companies in other industries, may experience cybersecurity threats, malicious activity directed against our information technology infrastructure and unauthorized attempts to gain access to our and our customers’ sensitive information and systems.

Stockholders' Equity

Stockholders' Equity	3 Months Ended
	Mar. 31, 2020
Share-based Payment Arrangement [Abstract]
STOCKHOLDERS' EQUITY	STOCKHOLDERS’ EQUITY Stock-Based Compensation Plans We maintain the Amended and Restated Fortinet, Inc. 2009 Equity Incentive Plan (the “Amended Plan”) pursuant to which we have granted RSU s and stock options. We also previously had an Employee Stock Purchase Plan (“ESPP”) for eligible employees, which was terminated in February 2019. As of March 31, 2020 , there was a total of 12.1 million shares of common stock available for grant under the Amended Plan. Restricted Stock Units The following table summarizes the activity and related information for RSU s for the periods presented below (in millions, except per share amounts): Restricted Stock Units Outstanding Number of Shares Weighted-Average Grant Date Fair Value per Share Balance—December 31, 2019 6.1 $ 64.56 Granted 1.3 114.33 Forfeited (0.1 ) 68.19 Vested (1.0 ) 58.17 Balance—March 31, 2020 6.3 $ 75.96 As of March 31, 2020 , total compensation expense related to unvested RSU s granted to employees and non-employees under the 2009 Plan, but not yet recognized, was $440.8 million . This expense is expected to be amortized on a straight-line basis over a weighted-average vesting period of 2.9 years. RSU s settle into shares of common stock upon vesting. Upon the vesting of the RSU s, we net-settle the RSU s and withhold a portion of the shares to satisfy minimum statutory employee withholding tax requirements. Total payment of the employees’ tax obligations to the tax authorities is reflected as a financing activity within the condensed consolidated statements of cash flows. The following summarizes the number and value of the shares withheld for employee taxes (in millions): Three Months Ended March 31, March 31, Shares withheld for taxes 0.3 0.4 Amount withheld for taxes $ 37.8 $ 32.0 Employee Stock Options The following table summarizes the weighted-average assumptions relating to our employee stock options: Three Months Ended March 31, March 31, Expected term in years 4.4 4.4 Volatility 33.5 % 34.2 % Risk-free interest rate 1.3 % 2.5 % Dividend rate — % — % The following table summarizes the stock option activity and related information for the periods presented below (in millions, except exercise prices and contractual life): Options Outstanding Number of Shares Weighted- Average Exercise Price Weighted- Average Remaining Contractual Life (Years) Aggregate Intrinsic Value Balance—December 31, 2019 2.7 $ 50.37 Granted 0.5 114.48 Forfeited — 59.28 Exercised (0.2 ) 40.02 Balance—March 31, 2020 3.0 $ 62.41 Options vested and expected to vest—March 31, 2020 3.0 $ 62.41 4.8 $ 123.8 Options exercisable—March 31, 2020 1.5 $ 39.50 3.5 $ 90.3 The aggregate intrinsic value represents the difference between the exercise price of stock options and the quoted market price of our common stock on March 31, 2020 for all in-the-money stock options. As of March 31, 2020 , total compensation expense related to unvested stock options granted to employees but not yet recognized was $38.6 million . This expense is expected to be amortized on a straight-line basis over a weighted-average period of 3.1 years. Additional information related to our stock options is summarized below (in millions, except per share amounts): Three Months Ended March 31, March 31, Weighted-average fair value per share granted $ 33.82 $ 27.12 Intrinsic value of options exercised $ 13.1 $ 27.2 Fair value of options vested $ 6.0 $ 4.2 Stock-Based Compensation Expense Stock-based compensation expense, including stock-based compensation expense related to awards classified as liabilities, is included in costs and expenses as follows (in millions): Three Months Ended March 31, March 31, Cost of product revenue $ 0.4 $ 0.4 Cost of service revenue 3.0 2.8 Research and development 10.9 9.4 Sales and marketing 25.7 25.4 General and administrative 5.3 5.0 Total stock-based compensation expense $ 45.3 $ 43.0 The following table summarizes stock-based compensation expense, including stock-based compensation expense related to awards classified as liabilities, by award type (in millions): Three Months Ended March 31, March 31, RSUs $ 42.2 $ 39.2 Stock options 3.1 2.5 ESPP — 1.3 Total stock-based compensation expense $ 45.3 $ 43.0 Total income tax benefit associated with stock-based compensation that is recognized in the condensed consolidated statements of income is as follows (in millions): Three Months Ended March 31, March 31, Income tax benefit associated with stock-based compensation $ 10.0 $ 10.0 Share Repurchase Program Under the Share Repurchase Program originally approved by our board of directors in January 2016 (the “ Repurchase Program ”), our board of directors has authorized the repurchase of up to $2.5 billion of our outstanding common stock through February 28, 2021. Share repurchases may be made by us from time to time in privately negotiated transactions or in open market transactions. The Repurchase Program does not require us to purchase a minimum number of shares, and may be suspended, modified or discontinued at any time without prior notice. During the three months ended March 31, 2020 , we repurchased 10.0 million shares of common stock under the Repurchase Program in open market transactions at an average price of $90.36 per share and for an aggregate purchase price of $899.9 million . As of March 31, 2020 , $692.9 million remained available for future share repurchases under the Repurchase Program .

Income Taxes

Income Taxes	3 Months Ended
	Mar. 31, 2020
Income Tax Disclosure [Abstract]
INCOME TAXES	INCOME TAXES Our effective tax rate was 11% for the three months ended March 31, 2020 , compared to an effective tax rate of 2% for the same period last year. The effective tax rates for the periods presented are primarily comprised of U.S. federal and state taxes, withholding taxes, foreign taxes and excess tax benefits from stock-based compensation expense. The tax rates for the three months ended March 31, 2020 and March 31, 2019 were impacted by U.S. federal and state taxes, withholding taxes and foreign taxes that were $28.3 million and $17.5 million , respectively, which were offset by excess tax benefits from stock-based compensation expense of $15.2 million and $16.0 million , respectively. U.S. federal and state taxes were lowered by a tax benefit of $4.8 million from the foreign-derived intangible income deduction for the three months ended March 31, 2020. As of March 31, 2020 and December 31, 2019 , unrecognized tax benefits were $65.6 million and $67.5 million , respectively. If recognized, $60.4 million of the unrecognized tax benefits would favorably affect our effective tax rate. It is our policy to include accrued interest and penalties related to uncertain tax benefits in income tax expense. As of March 31, 2020 and December 31, 2019 , accrued interest and penalties were $14.5 million and $14.1 million , respectively. It is reasonably possible that our gross unrecognized tax benefits will decrease by up to $10.4 million in the next 12 months, due to the lapse of the statute of limitations. This decrease, if recognized, would positively impact our effective tax rate, and would be recognized as additional tax benefits. We file income tax returns in the U.S. federal jurisdiction and in various U.S. state and foreign jurisdictions. Generally, we are no longer subject to U.S. state and foreign income tax examinations by tax authorities for tax years prior to 2010. We are no longer subject to examination by U.S federal income tax authorities for tax years prior to 2015. We currently have ongoing tax audits in the United Kingdom, Canada and several other foreign jurisdictions. The focus of these audits is the inter-company profit allocation. On June 7, 2019, the Ninth Circuit overturned the U.S. Tax Court’s decision in Altera Corporation and Subsidiaries vs. Commissioner of Internal Revenue (“Altera”) and ruled in favor of the Commissioner, validating the regulations requiring stock-based compensation to be included in a cost sharing arrangement. Due to the uncertainty surrounding the status of the current regulations and questions related to the scope of potential benefits or obligations, we incurred an unrecognized tax benefit of $8.5 million as of March 31, 2020 related to the Ninth Circuit’s Altera decision regarding stock-based compensation in cost sharing arrangements. We continue to monitor developments in this case and any impact it could have on our tax provision. On March 27, 2020, the President signed into law the Coronavirus Aid, Relief, and Economic Security Act (the “CARES” Act). The CARES Act provides numerous tax provisions and other stimulus measures, including temporary changes regarding the prior and future utilization of net operating losses, temporary changes to the prior and future limitations on interest deductions, temporary suspension of certain payment requirements for the employer portion of Social Security taxes, technical corrections from prior tax legislation for tax depreciation of certain qualified improvement property and the creation of certain refundable employee retention credits. The Company does not expect there to be a material tax impact on its consolidated financial statements at this time and will continue to assess the implications of the CARES Act and its continuing developments and interpretations.

Defined Contribution Plans

Defined Contribution Plans	3 Months Ended
	Mar. 31, 2020
Retirement Benefits [Abstract]
DEFINED CONTRIBUTION PLANS	DEFINED CONTRIBUTION PLANS Our tax-deferred savings plan under our 401(k) Plan permits participating U.S. employees to contribute a portion of their pre-tax or after-tax earnings. In Canada, we have a Group Registered Retirement Savings Plan Program (the “RRSP”), which permits participants to make tax-deductible contributions. Our board of directors approved 50% matching contributions on employee contributions up to 4% of each employee’s eligible earnings. Our matching contributions to our 401(k) Plan and the RRSP for the three months ended March 31, 2020 and March 31, 2019 were $2.2 million and $1.7 million

Segment Information

Segment Information	3 Months Ended
	Mar. 31, 2020
Segment Reporting [Abstract]
SEGMENT INFORMATION	SEGMENT INFORMATION Operating segments are defined as components of an enterprise about which separate financial information is available that is evaluated regularly by the chief operating decision maker in deciding how to allocate resources and in assessing performance. Our chief operating decision maker is our chief executive officer. Our chief executive officer reviews financial information presented on a consolidated basis, accompanied by information about revenue by geographic region for purposes of allocating resources and evaluating financial performance. We have one business activity, and there are no segment managers who are held accountable for operations, operating results and plans for levels or components below the consolidated unit level. Accordingly, we have determined that we have one operating segment, and therefore, one reportable segment. Revenue by geographic region is based on the billing address of our customers. The following tables set forth revenue and property and equipment—net by geographic region (in millions): Three Months Ended Revenue March 31, March 31, Americas: United States $ 181.6 $ 150.3 Other Americas 60.6 50.2 Total Americas 242.2 200.5 Europe, Middle East and Africa (“EMEA”) 220.7 177.2 Asia Pacific (“APAC”) 114.0 94.9 Total revenue $ 576.9 $ 472.6 Property and Equipment — net March 31, December 31, Americas: United States $ 227.4 $ 197.4 Canada 120.2 120.5 Latin America 6.1 5.5 Total Americas 353.7 323.4 EMEA 14.5 15.2 APAC 6.0 5.7 Total property and equipment—net $ 374.2 $ 344.3 The following distributors accounted for 10% or more of our revenue: Three Months Ended March 31, March 31, Exclusive Networks Group 31 % 30 % Ingram Micro 10 % 11 % The following distributors accounted for 10% or more of net accounts receivable: March 31, December 31, Exclusive Networks Group 34 % 36 % Ingram Micro * 10 % * Represents less than 10%

Subsequent Event

Subsequent Event	3 Months Ended
	Mar. 31, 2020
Subsequent Events [Abstract]
SUBSEQUENT EVENT	SUBSEQUENT EVENT Share repurchase Subsequent to March 31, 2020 through the filing of this Quarterly Report on Form 10-Q, we repurchased 1.5 million shares of our common stock under the Repurchase Program, for an aggregate purchase price of $146.1 million .

Summary of Significant Accoun_2

Summary of Significant Accounting Policies (Policies)	3 Months Ended
	Mar. 31, 2020
Accounting Policies [Abstract]
Basis of Presentation and Preparation	Basis of Presentation and Preparation —The unaudited condensed consolidated financial statements of Fortinet, Inc. and its wholly owned subsidiaries (collectively, “we,” “us” or “our”) have been prepared in accordance with generally accepted accounting principles in the United States (“ GAAP ”) for interim financial information, as well as the instructions to Form 10-Q pursuant to the rules and regulations of the U.S. Securities and Exchange Commission (the “ SEC ”). Accordingly, they do not include all of the information and footnotes required by GAAP for complete financial statements, and should be read in conjunction with our audited consolidated financial statements as of and for the year ended December 31, 2019, contained in our Annual Report on Form 10-K filed with the SEC on February 26, 2020. In the opinion of management, all adjustments, which includes normal recurring adjustments, considered necessary for a fair presentation have been included. All intercompany balances, transactions and cash flows have been eliminated. The results of operations for the three months ended March 31, 2020 are not necessarily indicative of the results for the full year or for any future periods. The condensed consolidated balance sheet as of December 31, 2019 is derived from the audited consolidated financial statements for the year ended December 31, 2019. For 2020, the amounts previously reported as Income taxes payable are included in Accrued liabilities. Prior periods have been reclassified to conform with current period presentation. The preparation of financial statements in accordance with GAAP requires management to make estimates and assumptions that affect the amounts reported in the condensed consolidated financial statements and accompanying notes. Actual results could differ materially from those estimates. There have been no material changes to our significant accounting policies as of and for the three months ended March 31, 2020 .
Recently Adopted Accounting Standards and Recent Accounting Standards Not Yet Effective	Recently Adopted Accounting Standards Financial Instruments In June 2016, the Financial Accounting Standards Board (“FASB”) issued Accounting Standards Update (“ASU”) 2016-13—Financial Instruments—Credit Losses (Topic 326): Measurement of Credit Losses on Financial Instruments (“ Topic 326 ”), which provides guidance on how an entity should measure credit losses on financial instruments. The standard replaces the existing incurred loss model with an expected credit loss model for financial assets measured at amortized cost, including trade receivables, and requires that credit losses on available-for-sale debt securities be presented as an allowance rather than as a write-down. The new approach to estimating credit losses (referred to as the current expected credit losses model) generally accelerates recognition of credit losses. We adopted Topic 326 on January 1, 2020 using the modified retrospective method. The adoption of this standard did not have a material impact on our condensed consolidated financial statements. Cloud Computing In August 2018, the FASB issued ASU 2018-15—Intangibles—Goodwill and Other—Internal-Use Software (Subtopic 350-40): Customer’s Accounting for Implementation Costs Incurred in a Cloud Computing Arrangement That Is a Service Contract, which requires a customer in a cloud computing arrangement that is a service contract to follow the internal-use software guidance in Accounting Standards Codification (“ ASC ”) Topic 350, Intangibles—Goodwill and Other, to determine which implementation costs to capitalize as assets or expense as incurred. We adopted ASU 2018-15 on January 1, 2020. The adoption of this standard did not have a material impact on our condensed consolidated financial statements. Fair Value Measurements In August 2018, the FASB issued ASU 2018-13—Fair Value Measurement (Topic 820): Disclosure Framework—Changes to the Disclosure Requirements for Fair Value Measurement, which eliminates, adds and modifies certain disclosure requirements for fair value measurements in ASC 820, Fair Value Measurement, as part of its disclosure framework project. We adopted ASU 2018-13 on January 1, 2020. The adoption of this standard did not have a material impact on our disclosures. Recent Accounting Standards Not Yet Effective Income Taxes In December 2019, the FASB issued ASU 2019-12—Income Taxes (Topic 740): Simplifying the Accounting for Income Taxes. The amendments in ASU 2019-12 simplify the accounting for income taxes by removing certain exceptions to the general principles in Topic 740. The amendments also improve consistent application and simplification of GAAP for other areas of Topic 740 by clarifying and amending existing guidance. ASU 2019-12 is effective for us beginning on January 1, 2021. Early adoption of the amendments is permitted. We are currently evaluating the impact of ASU 2019-12 on our condensed consolidated financial statements.

Revenue Recognition (Tables)

Revenue Recognition (Tables)	3 Months Ended
	Mar. 31, 2020
Revenue from Contract with Customer [Abstract]
Disaggregation of Revenue	Disaggregation of Revenue The following table presents our revenue disaggregated by major product and service lines (in millions): Three Months Ended March 31, March 31, Product $ 192.3 $ 162.7 Service: Security subscription 211.4 169.6 Technical support and other 173.2 140.3 Total service revenue 384.6 309.9 Total revenue $ 576.9 $ 472.6

Financial Instruments and Fai_2

Financial Instruments and Fair Value (Tables)	3 Months Ended
	Mar. 31, 2020
Financial Instruments and Fair Value [Abstract]
Summary of Investments	The following tables summarize our investments (in millions): March 31, 2020 Amortized Cost Unrealized Gains Unrealized Losses Fair Value Corporate debt securities $ 616.3 $ 0.3 $ (4.2 ) $ 612.4 Commercial paper 150.6 0.1 (0.1 ) 150.6 U.S. government securities 96.6 0.5 — 97.1 Certificates of deposit and term deposits (1) 87.7 0.1 (0.7 ) 87.1 Total available-for-sale securities $ 951.2 $ 1.0 $ (5.0 ) $ 947.2 December 31, 2019 Amortized Cost Unrealized Gains Unrealized Losses Fair Value Corporate debt securities $ 576.1 $ 1.0 $ (0.1 ) $ 577.0 Commercial paper 148.7 0.1 — 148.8 U.S. government securities 195.0 0.2 — 195.2 Certificates of deposit and term deposits (1) 66.4 — — 66.4 Total available-for-sale securities $ 986.2 $ 1.3 $ (0.1 ) $ 987.4 (1) The majority of our certificates of deposit and term deposits are foreign deposits.
Schedule of Unrealized Loss on Investments	The following tables show the gross unrealized losses and the related fair values of our investments that have been in a continuous unrealized loss position (in millions): March 31, 2020 Less Than 12 Months 12 Months or Greater Total Fair Value Unrealized Losses Fair Value Unrealized Losses Fair Value Unrealized Losses Corporate debt securities $ 475.2 $ (4.2 ) $ 7.1 $ — $ 482.3 $ (4.2 ) Commercial paper 45.5 (0.1 ) — — 45.5 (0.1 ) Certificates of deposit and term deposits 49.1 (0.7 ) — — 49.1 (0.7 ) Total available-for-sale securities $ 569.8 $ (5.0 ) $ 7.1 $ — $ 576.9 $ (5.0 ) December 31, 2019 Less Than 12 Months 12 Months or Greater Total Fair Value Unrealized Losses Fair Value Unrealized Losses Fair Value Unrealized Losses Corporate debt securities $ 117.3 $ (0.1 ) $ 16.1 $ — $ 133.4 $ (0.1 ) Commercial paper 26.0 — — — 26.0 — U.S. government securities 47.1 — — — 47.1 — Certificates of deposit and term deposits 13.0 — — — 13.0 — Total available-for-sale securities $ 203.4 $ (0.1 ) $ 16.1 $ — $ 219.5 $ (0.1 )
Investments Classified by Contractual Maturity Date	The contractual maturities of our investments were as follows (in millions): March 31, December 31, Due within one year $ 775.2 $ 843.1 Due within one to three years 172.0 144.3 Total $ 947.2 $ 987.4
Schedule of Fair Value, Assets and Liabilities Measured on Recurring Basis	The following tables present the fair value of our financial assets measured at fair value on a recurring basis as of March 31, 2020 and December 31, 2019 (in millions): March 31, 2020 December 31, 2019 Aggregate Fair Value Quoted Prices in Active Markets For Identical Assets Significant Other Observable Remaining Inputs Significant Other Unobservable Remaining Inputs Aggregate Fair Value Quoted Prices in Active Markets For Identical Assets Significant Other Observable Remaining Inputs Significant Other Unobservable Remaining Inputs (Level 1) (Level 2) (Level 3) (Level 1) (Level 2) (Level 3) Assets: Corporate debt securities $ 613.4 $ — $ 613.4 $ — $ 577.0 $ — $ 577.0 $ — Commercial paper 164.6 — 164.6 — 165.8 — 165.8 — Certificates of deposit and term deposits 87.1 — 87.1 — 66.4 — 66.4 — U.S. government securities 97.1 97.1 — — 195.2 195.2 — — Money market funds 163.7 163.7 — — 15.0 15.0 — — Total $ 1,125.9 $ 260.8 $ 865.1 $ — $ 1,019.4 $ 210.2 $ 809.2 $ — Reported as: Cash equivalents $ 178.7 $ 32.0 Short-term investments 775.2 843.1 Long-term investments 172.0 144.3 Total $ 1,125.9 $ 1,019.4

Inventory (Tables)

Inventory (Tables)	3 Months Ended
	Mar. 31, 2020
Inventory Disclosure [Abstract]
Inventory	Inventory consisted of the following (in millions): March 31, December 31, Raw materials $ 12.5 $ 9.7 Finished goods 92.5 108.2 Inventory $ 105.0 $ 117.9

Property and Equipment_Net (Tab

Property and Equipment—Net (Tables)	3 Months Ended
	Mar. 31, 2020
Property, Plant and Equipment [Abstract]
Property, Plant and Equipment - Net	Property and equipment—net consisted of the following (in millions): March 31, December 31, Land $ 93.3 $ 93.3 Building and building improvements 148.0 147.4 Computer equipment and software 121.7 116.7 Leasehold improvements 26.8 25.5 Evaluation units 22.4 19.9 Furniture and fixtures 18.2 17.3 Construction-in-progress 90.7 61.2 Total property and equipment 521.1 481.3 Less: accumulated depreciation (146.9 ) (137.0 ) Property and equipment—net $ 374.2 $ 344.3

Goodwill and Other Intangible_2

Goodwill and Other Intangible Assets - Net (Tables)	3 Months Ended
	Mar. 31, 2020
Goodwill and Intangible Assets Disclosure [Abstract]
Schedule of Finite-Lived and Indefinite-Lived Intangible Assets by Major Class	The following tables present other intangible assets—net as of March 31, 2020 and December 31, 2019 (in millions, except years): March 31, 2020 Weighted-Average Useful Life (in Years) Gross Accumulated Amortization Net Other intangible assets—net: Finite-lived intangible assets: Developed technologies 4.0 $ 48.8 $ 25.8 $ 23.0 Customer relationships 4.1 21.6 17.5 4.1 Total other intangible assets—net $ 70.4 $ 43.3 $ 27.1 December 31, 2019 Weighted-Average Useful Life (in Years) Gross Accumulated Amortization Net Other intangible assets—net: Finite-lived intangible assets: Developed technologies 4.0 $ 50.2 $ 24.6 $ 25.6 Customer relationships 4.1 21.6 16.1 5.5 Total other intangible assets—net $ 71.8 $ 40.7 $ 31.1
Schedule of Finite-Lived Intangible Assets, Future Amortization Expense	The following table summarizes estimated future amortization expense of finite-lived intangible assets—net (in millions): Amount Years: 2020 (the remainder of 2020) $ 8.7 2021 8.3 2022 6.4 2023 3.7 Total $ 27.1

Net Income Per Share (Tables)

Net Income Per Share (Tables)	3 Months Ended
	Mar. 31, 2020
Earnings Per Share [Abstract]
Schedule of Earnings Per Share, Basic and Diluted	A reconciliation of the numerator and denominator used in the calculation of basic and diluted net income per share is as follows (in millions, except per share amounts): Three Months Ended March 31, March 31, Numerator: Net income $ 104.0 $ 58.8 Denominator: Basic shares: Weighted-average common stock outstanding-basic 170.6 170.2 Diluted shares: Weighted-average common stock outstanding-basic 170.6 170.2 Effect of potentially dilutive securities: RSUs 2.4 3.3 Stock options 1.2 1.3 Weighted-average shares used to compute diluted net income per share 174.2 174.8 Net income per share: Basic $ 0.61 $ 0.35 Diluted $ 0.60 $ 0.34
Schedule of Antidilutive Securities Excluded from Computation of Earnings Per Share	The following weighted-average shares of common stock were excluded from the computation of diluted net income per share for the periods presented, as their effect would have been antidilutive (in millions): Three Months Ended March 31, March 31, RSUs 0.6 0.7 Stock options 0.3 0.3 Total 0.9 1.0

Leases (Tables)

Leases (Tables)	3 Months Ended
	Mar. 31, 2020
Leases [Abstract]
Components of Lease Expense and Supplemental Cash Flow Information	Supplemental cash flow information related to leases was as follows (in millions): Three Months Ended Three Months Ended March 31, March 31, Cash paid for amounts included in the measurement of lease liabilities Operating cash flows used for operating leases $ 4.6 $ 4.6 Lease liabilities arising from obtaining right-of-use assets Operating leases $ 2.4 $ 3.5 The components of lease expense were as follows (in millions): Three Months Ended Three Months Ended March 31, March 31, Operating lease expense $ 4.3 $ 3.6 Variable lease expense (1) 0.6 0.6 Short-term lease expense 0.9 0.7 Total lease expense $ 5.8 $ 4.9 (1) Variable lease expense for the three months ended March 31, 2020 and March 31, 2019 predominantly included common area maintenance charges and parking expense.
Supplemental Balance Sheet Information	Supplemental balance sheet information related to our operating leases was as follows (in millions, except lease term and discount rate): Classification March 31, December 31, Operating lease ROU assets - non-current Other assets $ 42.7 $ 44.3 Operating lease liabilities - current Accrued liabilities $ 14.8 $ 15.5 Operating lease liabilities - non-current Other liabilities 28.3 30.6 Total operating lease liabilities $ 43.1 $ 46.1 Weighted average remaining lease term in years - operating leases 3.6 3.7 Weighted average discount rate - operating leases 2.8 % 2.8 %
Maturities of Operating Lease Liabilities	Maturities of operating lease liabilities as of March 31, 2020 were as follows (in millions): Year ending December 31, Amount 2020 (the remainder of 2020) $ 11.9 2021 13.6 2022 8.7 2023 5.4 2024 3.9 Thereafter 1.8 Total lease payments 45.3 Less imputed interest (2.2 ) Total $ 43.1

Commitments and Contingencies (

Commitments and Contingencies (Tables)	3 Months Ended
	Mar. 31, 2020
Commitments and Contingencies Disclosure [Abstract]
Inventory Purchase Commitments, Fiscal Year Maturity Schedule	The following table summarizes our inventory purchase commitments as of March 31, 2020 (in millions): Total 2020 2021 2022 2023 2024 Thereafter Inventory purchase commitments $ 247.2 $ 247.2 $ — $ — $ — $ — $ —

Stockholders' Equity (Tables)

Stockholders' Equity (Tables)	3 Months Ended
	Mar. 31, 2020
Share-based Payment Arrangement [Abstract]
Schedule of Share-based Compensation, Restricted Stock Units Award Activity	The following table summarizes the activity and related information for RSU s for the periods presented below (in millions, except per share amounts): Restricted Stock Units Outstanding Number of Shares Weighted-Average Grant Date Fair Value per Share Balance—December 31, 2019 6.1 $ 64.56 Granted 1.3 114.33 Forfeited (0.1 ) 68.19 Vested (1.0 ) 58.17 Balance—March 31, 2020 6.3 $ 75.96
Schedule of Share-based Compensation, Shares Withheld for Taxes	The following summarizes the number and value of the shares withheld for employee taxes (in millions): Three Months Ended March 31, March 31, Shares withheld for taxes 0.3 0.4 Amount withheld for taxes $ 37.8 $ 32.0
Schedule of Share-based Payment Award, Stock Options, Valuation Assumptions	The following table summarizes the weighted-average assumptions relating to our employee stock options: Three Months Ended March 31, March 31, Expected term in years 4.4 4.4 Volatility 33.5 % 34.2 % Risk-free interest rate 1.3 % 2.5 % Dividend rate — % — %
Schedule of Share-based Compensation, Stock Options, Activity	The following table summarizes the stock option activity and related information for the periods presented below (in millions, except exercise prices and contractual life): Options Outstanding Number of Shares Weighted- Average Exercise Price Weighted- Average Remaining Contractual Life (Years) Aggregate Intrinsic Value Balance—December 31, 2019 2.7 $ 50.37 Granted 0.5 114.48 Forfeited — 59.28 Exercised (0.2 ) 40.02 Balance—March 31, 2020 3.0 $ 62.41 Options vested and expected to vest—March 31, 2020 3.0 $ 62.41 4.8 $ 123.8 Options exercisable—March 31, 2020 1.5 $ 39.50 3.5 $ 90.3
Schedule of Share-based Compensation, Stock Options, Activity, Additional Information	Additional information related to our stock options is summarized below (in millions, except per share amounts): Three Months Ended March 31, March 31, Weighted-average fair value per share granted $ 33.82 $ 27.12 Intrinsic value of options exercised $ 13.1 $ 27.2 Fair value of options vested $ 6.0 $ 4.2
Schedule of Employee Service Share-based Compensation, Allocation of Recognized Period Costs	Stock-based compensation expense, including stock-based compensation expense related to awards classified as liabilities, is included in costs and expenses as follows (in millions): Three Months Ended March 31, March 31, Cost of product revenue $ 0.4 $ 0.4 Cost of service revenue 3.0 2.8 Research and development 10.9 9.4 Sales and marketing 25.7 25.4 General and administrative 5.3 5.0 Total stock-based compensation expense $ 45.3 $ 43.0
Schedule of Employee Service Share based Compensation Allocation of Recognized Period Costs by Award Type	The following table summarizes stock-based compensation expense, including stock-based compensation expense related to awards classified as liabilities, by award type (in millions): Three Months Ended March 31, March 31, RSUs $ 42.2 $ 39.2 Stock options 3.1 2.5 ESPP — 1.3 Total stock-based compensation expense $ 45.3 $ 43.0
Income Tax Benefit from Stock Option Plans	Total income tax benefit associated with stock-based compensation that is recognized in the condensed consolidated statements of income is as follows (in millions): Three Months Ended March 31, March 31, Income tax benefit associated with stock-based compensation $ 10.0 $ 10.0

Segment Information (Tables)

Segment Information (Tables)	3 Months Ended
	Mar. 31, 2020
Segment Reporting [Abstract]
Revenue from external customers by geographic region	Revenue by geographic region is based on the billing address of our customers. The following tables set forth revenue and property and equipment—net by geographic region (in millions): Three Months Ended Revenue March 31, March 31, Americas: United States $ 181.6 $ 150.3 Other Americas 60.6 50.2 Total Americas 242.2 200.5 Europe, Middle East and Africa (“EMEA”) 220.7 177.2 Asia Pacific (“APAC”) 114.0 94.9 Total revenue $ 576.9 $ 472.6
Property and equipment by geographic region	Property and Equipment — net March 31, December 31, Americas: United States $ 227.4 $ 197.4 Canada 120.2 120.5 Latin America 6.1 5.5 Total Americas 353.7 323.4 EMEA 14.5 15.2 APAC 6.0 5.7 Total property and equipment—net $ 374.2 $ 344.3
Schedule of distributor concentration	The following distributors accounted for 10% or more of our revenue: Three Months Ended March 31, March 31, Exclusive Networks Group 31 % 30 % Ingram Micro 10 % 11 % The following distributors accounted for 10% or more of net accounts receivable: March 31, December 31, Exclusive Networks Group 34 % 36 % Ingram Micro * 10 % * Represents less than 10%

Revenue Recognition - Disaggreg

Revenue Recognition - Disaggregated Revenues (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
Disaggregation of Revenue [Line Items]
Total revenue	$ 576.9	$ 472.6
Product [Member]
Disaggregation of Revenue [Line Items]
Total revenue	192.3	162.7
Service [Member]
Disaggregation of Revenue [Line Items]
Total revenue	384.6	309.9
Security Subscription [Member]
Disaggregation of Revenue [Line Items]
Total revenue	211.4	169.6
Technical Support and Other [Member]
Disaggregation of Revenue [Line Items]
Total revenue	$ 173.2	$ 140.3

Revenue Recognition (Details)

Revenue Recognition (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019	Dec. 31, 2019
Disaggregation of Revenue [Line Items]
Remaining performance obligation	$ 2,230
Threshold period past due	60 days
Allowance for doubtful accounts	$ 1.1		$ 1.2
Amortization of deferred contract costs	31.3	$ 25.1
Service [Member]
Disaggregation of Revenue [Line Items]
Deferred revenue recognized in period	$ 348.9	$ 288.6

Revenue Recognition - Performan

Revenue Recognition - Performance Obligation Satisfaction Period (Details) $ in Millions	Mar. 31, 2020USD ($)
Revenue from Contract with Customer [Abstract]
Remaining performance obligation	$ 2,230
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2020-04-01
Revenue from Contract with Customer [Abstract]
Remaining performance obligation	$ 1,230
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Performance obligation expected recognition period for three-fourths of remaining obligation	12 months
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2021-04-01
Revenue from Contract with Customer [Abstract]
Remaining performance obligation	$ 1,000
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Performance obligation expected recognition period for three-fourths of remaining obligation

Financial Instruments and Fai_3

Financial Instruments and Fair Value , Investments (Details) - USD ($) $ in Millions	Mar. 31, 2020	Dec. 31, 2019
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	$ 951.2	$ 986.2
Unrealized Gains	1	1.3
Unrealized Losses	(5)	(0.1)
Fair Value	947.2	987.4
Available-for-sale Securities, Continuous Unrealized Loss Position [Abstract]
Less Than 12 Months, Fair Value	569.8	203.4
Less Than 12 Months, Unrealized Losses	(5)	(0.1)
12 Months or Greater, Fair Value	7.1	16.1
12 Months or Greater, Unrealized Losses	0	0
Total, Fair Value	576.9	219.5
Total, Unrealized Losses	(5)	(0.1)
Available-for-sale Securities, Debt Maturities, Fair Value [Abstract]
Due within one year	775.2	843.1
Due within one to three years	172	144.3
Fair Value	947.2	987.4
Corporate debt securities [Member]
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	616.3	576.1
Unrealized Gains	0.3	1
Unrealized Losses	(4.2)	(0.1)
Fair Value	612.4	577
Available-for-sale Securities, Continuous Unrealized Loss Position [Abstract]
Less Than 12 Months, Fair Value	475.2	117.3
Less Than 12 Months, Unrealized Losses	(4.2)	(0.1)
12 Months or Greater, Fair Value	7.1	16.1
12 Months or Greater, Unrealized Losses	0	0
Total, Fair Value	482.3	133.4
Total, Unrealized Losses	(4.2)	(0.1)
Available-for-sale Securities, Debt Maturities, Fair Value [Abstract]
Fair Value	612.4	577
Commercial paper [Member]
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	150.6	148.7
Unrealized Gains	0.1	0.1
Unrealized Losses	(0.1)	0
Fair Value	150.6	148.8
Available-for-sale Securities, Continuous Unrealized Loss Position [Abstract]
Less Than 12 Months, Fair Value	45.5	26
Less Than 12 Months, Unrealized Losses	(0.1)	0
12 Months or Greater, Fair Value	0	0
12 Months or Greater, Unrealized Losses	0	0
Total, Fair Value	45.5	26
Total, Unrealized Losses	(0.1)	0
Available-for-sale Securities, Debt Maturities, Fair Value [Abstract]
Fair Value	150.6	148.8
U.S. government securities [Member]
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	96.6	195
Unrealized Gains	0.5	0.2
Unrealized Losses	0	0
Fair Value	97.1	195.2
Available-for-sale Securities, Continuous Unrealized Loss Position [Abstract]
Less Than 12 Months, Fair Value		47.1
Less Than 12 Months, Unrealized Losses		0
12 Months or Greater, Fair Value		0
12 Months or Greater, Unrealized Losses		0
Total, Fair Value		47.1
Total, Unrealized Losses		0
Available-for-sale Securities, Debt Maturities, Fair Value [Abstract]
Fair Value	97.1	195.2
Certificates of deposit and term deposits [Member]
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	87.7	66.4
Unrealized Gains	0.1	0
Unrealized Losses	(0.7)	0
Fair Value	87.1	66.4
Available-for-sale Securities, Continuous Unrealized Loss Position [Abstract]
Less Than 12 Months, Fair Value	49.1	13
Less Than 12 Months, Unrealized Losses	(0.7)	0
12 Months or Greater, Fair Value	0	0
12 Months or Greater, Unrealized Losses	0	0
Total, Fair Value	49.1	13
Total, Unrealized Losses	(0.7)	0
Available-for-sale Securities, Debt Maturities, Fair Value [Abstract]
Fair Value	$ 87.1	$ 66.4

Financial Instruments and Fai_4

Financial Instruments and Fair Value , Additional Information (Details) $ in Millions	Mar. 31, 2020USD ($)
Financial Instruments and Fair Value [Abstract]
Accrued interest on available-for-sale securities	$ 4.7

Financial Instruments and Fai_5

Financial Instruments and Fair Value , Fair Value Measurements (Details) - USD ($) $ in Millions	Mar. 31, 2020	Dec. 31, 2019
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value	$ 947.2	$ 987.4
Corporate debt securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value	612.4	577
Commercial paper [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value	150.6	148.8
Certificates of deposit and term deposits [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value	87.1	66.4
U.S. government securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value	97.1	195.2
Recurring Basis [Member] | Fair Value [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total Assets, Fair Value Disclosure	1,125.9	1,019.4
Recurring Basis [Member] | Fair Value [Member] | Level 1 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total Assets, Fair Value Disclosure	260.8	210.2
Recurring Basis [Member] | Fair Value [Member] | Level 2 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total Assets, Fair Value Disclosure	865.1	809.2
Recurring Basis [Member] | Fair Value [Member] | Level 3 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total Assets, Fair Value Disclosure	0	0
Recurring Basis [Member] | Fair Value [Member] | Corporate debt securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value	613.4	577
Recurring Basis [Member] | Fair Value [Member] | Corporate debt securities [Member] | Level 1 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value	0	0
Recurring Basis [Member] | Fair Value [Member] | Corporate debt securities [Member] | Level 2 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value	613.4	577
Recurring Basis [Member] | Fair Value [Member] | Corporate debt securities [Member] | Level 3 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value	0	0
Recurring Basis [Member] | Fair Value [Member] | Commercial paper [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value	164.6	165.8
Recurring Basis [Member] | Fair Value [Member] | Commercial paper [Member] | Level 1 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value	0	0
Recurring Basis [Member] | Fair Value [Member] | Commercial paper [Member] | Level 2 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value	164.6	165.8
Recurring Basis [Member] | Fair Value [Member] | Commercial paper [Member] | Level 3 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value	0	0
Recurring Basis [Member] | Fair Value [Member] | Certificates of deposit and term deposits [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value	87.1	66.4
Recurring Basis [Member] | Fair Value [Member] | Certificates of deposit and term deposits [Member] | Level 1 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value	0	0
Recurring Basis [Member] | Fair Value [Member] | Certificates of deposit and term deposits [Member] | Level 2 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value	87.1	66.4
Recurring Basis [Member] | Fair Value [Member] | Certificates of deposit and term deposits [Member] | Level 3 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value	0	0
Recurring Basis [Member] | Fair Value [Member] | U.S. government securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value	97.1	195.2
Recurring Basis [Member] | Fair Value [Member] | U.S. government securities [Member] | Level 1 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value	97.1	195.2
Recurring Basis [Member] | Fair Value [Member] | U.S. government securities [Member] | Level 2 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value	0	0
Recurring Basis [Member] | Fair Value [Member] | U.S. government securities [Member] | Level 3 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value	0	0
Recurring Basis [Member] | Fair Value [Member] | Money market funds [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value	163.7	15
Recurring Basis [Member] | Fair Value [Member] | Money market funds [Member] | Level 1 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value	163.7	15
Recurring Basis [Member] | Fair Value [Member] | Money market funds [Member] | Level 2 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value	0	0
Recurring Basis [Member] | Fair Value [Member] | Money market funds [Member] | Level 3 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value	0	0
Recurring Basis [Member] | Reported as [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total Assets, Fair Value Disclosure	1,125.9	1,019.4
Recurring Basis [Member] | Reported as [Member] | Cash equivalents [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value	178.7	32
Recurring Basis [Member] | Reported as [Member] | Short-term investments [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value	775.2	843.1
Recurring Basis [Member] | Reported as [Member] | Long-term investments [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value	$ 172	$ 144.3

Inventory (Details)

Inventory (Details) - USD ($) $ in Millions	Mar. 31, 2020	Dec. 31, 2019
Inventory, Net [Abstract]
Raw materials	$ 12.5	$ 9.7
Finished goods	92.5	108.2
Inventory	$ 105	$ 117.9

Property and Equipment_Net (Det

Property and Equipment—Net (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019	Dec. 31, 2019
Property, Plant and Equipment, Net, by Type [Abstract]
Total property and equipment	$ 521.1		$ 481.3
Less: accumulated depreciation	(146.9)		(137)
Property and equipment - net	374.2		344.3
Depreciation expense	13.6	$ 12.7
Land [Member]
Property, Plant and Equipment, Net, by Type [Abstract]
Total property and equipment	93.3		93.3
Building and building improvements [Member]
Property, Plant and Equipment, Net, by Type [Abstract]
Total property and equipment	148		147.4
Computer equipment and software [Member]
Property, Plant and Equipment, Net, by Type [Abstract]
Total property and equipment	121.7		116.7
Leasehold improvements [Member]
Property, Plant and Equipment, Net, by Type [Abstract]
Total property and equipment	26.8		25.5
Evaluation units [Member]
Property, Plant and Equipment, Net, by Type [Abstract]
Total property and equipment	22.4		19.9
Furniture and fixtures [Member]
Property, Plant and Equipment, Net, by Type [Abstract]
Total property and equipment	18.2		17.3
Construction-in-progress [Member]
Property, Plant and Equipment, Net, by Type [Abstract]
Total property and equipment	$ 90.7		$ 61.2

Investments in Privately-Held_2

Investments in Privately-Held Companies (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2020	Dec. 31, 2019
Investments, All Other Investments [Abstract]
Investments in equity securities of privately-held companies	$ 1	$ 5.3
Non-cash impairment charge	$ 4.3

Goodwill and Other Intangible_3

Goodwill and Other Intangible Assets - Net - Narrative (Details) - USD ($)	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019	Dec. 31, 2019
Goodwill and Intangible Assets Disclosure [Abstract]
Goodwill	$ 67,200,000		$ 67,200,000
Goodwill impairment	0	$ 0
Amortization expense	$ 4,000,000	$ 3,000,000

Goodwill and Other Intangible_4

Goodwill and Other Intangible Assets - Net - Other Intangible Assets, Net (Details) - USD ($) $ in Millions	3 Months Ended	12 Months Ended
	Mar. 31, 2020	Dec. 31, 2019
Finite-Lived Intangible Assets, Net [Abstract]
Gross	$ 70.4	$ 71.8
Accumulated Amortization	43.3	40.7
Total	$ 27.1	$ 31.1
Developed Technologies [Member]
Finite-Lived Intangible Assets [Line Items]
Weighted average useful life	4 years	4 years
Finite-Lived Intangible Assets, Net [Abstract]
Gross	$ 48.8	$ 50.2
Accumulated Amortization	25.8	24.6
Total	$ 23	$ 25.6
Customer Relationships [Member]
Finite-Lived Intangible Assets [Line Items]
Weighted average useful life	4 years 1 month 6 days	4 years 1 month 6 days
Finite-Lived Intangible Assets, Net [Abstract]
Gross	$ 21.6	$ 21.6
Accumulated Amortization	17.5	16.1
Total	$ 4.1	$ 5.5

Goodwill and Other Intangible_5

Goodwill and Other Intangible Assets - Net - Estimated Future Amortization Expense (Details) - USD ($) $ in Millions	Mar. 31, 2020	Dec. 31, 2019
Fiscal Years:
2020 (the remainder of 2020)	$ 8.7
2021	8.3
2022	6.4
2023	3.7
Total	$ 27.1	$ 31.1

Net Income Per Share , Calculat

Net Income Per Share , Calculation of Basic and Diluted (Details) - USD ($) $ / shares in Units, shares in Millions, $ in Millions	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
Earnings Per Share [Line Items]
Net income	$ 104	$ 58.8
Basic shares:
Weighted-average common shares outstanding-basic (in shares)	170.6	170.2
Diluted shares:
Weighted-average common shares outstanding-basic (in shares)	170.6	170.2
Effect of potentially dilutive securities:
Weighted-average shares used to compute diluted net income per share (in shares)	174.2	174.8
Basic (in dollars per share)	$ 0.61	$ 0.35
Diluted (in dollars per share)	$ 0.60	$ 0.34
Restricted Stock Units (RSUs) [Member]
Effect of potentially dilutive securities:
RSUs, stock options, and ESPP (in shares)	2.4	3.3
Stock Options [Member]
Effect of potentially dilutive securities:
RSUs, stock options, and ESPP (in shares)	1.2	1.3

Net Income Per Share , Anti Dil

Net Income Per Share , Anti Dilutive Securities (Details) - shares shares in Millions	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Anti-dilutive securities (in shares)	0.9	1
Restricted Stock Units (RSUs) [Member] | Share-based Payment Arrangement [Member]
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Anti-dilutive securities (in shares)	0.6	0.7
Stock Options [Member] | Share-based Payment Arrangement [Member]
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Anti-dilutive securities (in shares)	0.3	0.3

Leases (Details)

Leases (Details) - USD ($) $ in Millions	3 Months Ended	12 Months Ended
	Mar. 31, 2020	Dec. 31, 2019
Lessee, Lease, Description [Line Items]
Renewal terms (up to)	5 years
Finance lease liabilities arising from obtaining right-of-use assets		$ 3.6
Finance lease term		2 years
Additional minimum lease payments relating to operating leases signed but not yet commenced	$ 5.1
Minimum [Member]
Lessee, Lease, Description [Line Items]
Remaining terms (less than for minimum)	1 year
Lease not yet commenced, approximate term	5 years
Maximum [Member]
Lessee, Lease, Description [Line Items]
Remaining terms (less than for minimum)	7 years
Lease not yet commenced, approximate term	7 years

Leases - Components of Lease Ex

Leases - Components of Lease Expense (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
Leases [Abstract]
Operating lease expense	$ 4.3	$ 3.6
Variable lease expense	0.6	0.6
Short-term lease expense	0.9	0.7
Total lease expense	$ 5.8	$ 4.9

Leases - Supplemental Balance S

Leases - Supplemental Balance Sheet Information (Details) - USD ($) $ in Millions	Mar. 31, 2020	Dec. 31, 2019
Leases [Abstract]
Operating lease ROU assets - non-current	$ 42.7	$ 44.3
Operating lease liabilities - current	14.8	15.5
Operating lease liabilities - non-current	28.3	30.6
Total operating lease liabilities	$ 43.1	$ 46.1
Weighted average remaining lease term in years - operating leases	3 years 7 months 6 days	3 years 8 months 12 days
Weighted average discount rate - operating leases	2.80%	2.80%

Leases - Supplemental Cash Flow

Leases - Supplemental Cash Flow Information (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
Cash paid for amounts included in the measurement of lease liabilities
Operating cash flows used for operating leases	$ 4.6	$ 4.6
Lease liabilities arising from obtaining right-of-use assets
Operating leases	$ 2.4	$ 3.5

Leases - Maturities of Operatin

Leases - Maturities of Operating Lease Liabilities (Details) - USD ($) $ in Millions	Mar. 31, 2020	Dec. 31, 2019
Leases [Abstract]
2020 (the remainder of 2020)	$ 11.9
2021	13.6
2022	8.7
2023	5.4
2024	3.9
Thereafter	1.8
Total lease payments	45.3
Less imputed interest	(2.2)
Total	$ 43.1	$ 46.1

Mutual Covenant-Not-to-Sue an_2

Mutual Covenant-Not-to-Sue and Release Agreement (Details) - USD ($)	1 Months Ended	3 Months Ended
	Jan. 31, 2020	Mar. 31, 2020	Mar. 31, 2019
Mutual Covenant-Not-to-Sue Agreement [Abstract]
Proceeds from mutual covenant-not-to-sue agreement	$ 50,000,000
Initial term	7 years
Extension term	7 years
Additional proceeds if extended	$ 50,000,000
Contractual term	14 years
Total proceeds if extension option utilized	$ 100,000,000
Amount allocated to functional component	36,000,000	$ 36,000,000
Amount representing the right to utilize future patents	$ 64,000,000
Gain on IP matter		36,800,000	$ 0
Amortization of deferred component		800,000
Amount recorded in Accrued liabilities and Other liabilities in condensed consolidated balance sheet		$ 13,200,000

Commitments and Contingencies M

Commitments and Contingencies Minimum Operating Lease Payments (Details) $ in Millions	Mar. 31, 2020USD ($)
Inventory purchase commitments:
Inventory purchase commitments, 2020	$ 247.2
Inventory purchase commitments, 2021	0
Inventory purchase commitments, 2022	0
Inventory purchase commitments, 2023	0
Inventory purchase commitments, 2024	0
Inventory purchase commitments, Thereafter	0
Inventory purchase commitments	$ 247.2

Commitments and Contingencies_2

Commitments and Contingencies (Details) $ in Millions	Mar. 31, 2020USD ($)
Commitments and Contingencies Disclosure [Abstract]
Inventory purchase commitments	$ 247.2
Other contractual commitments and open purchase orders	$ 10.9

Stockholders' Equity , Restrict

Stockholders' Equity , Restricted Stock Units Activity (Details) - USD ($) $ / shares in Units, shares in Millions, $ in Millions	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
Weighted-Average Grant Date Fair Value per Share
Shares withheld for taxes	0.3	0.4
Amount withheld for taxes	$ 37.8	$ 32
Stock-based Compensation Plan [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Remaining shares available for grant under the plans	12.1
Restricted Stock Units (RSUs) [Member]
Number of Shares
Balance, beginning (shares)	6.1
Granted (shares)	1.3
Forfeited (shares)	(0.1)
Vested (shares)	(1)
Balance, ending (shares)	6.3
Weighted-Average Grant Date Fair Value per Share
Balance, beginning (in dollars per share)	$ 64.56
Granted (in dollars per share)	114.33
Forfeited (in dollars per share)	68.19
Vested (in dollars per share)	58.17
Balance, ending (in dollars per share)	$ 75.96
Compensation cost not yet recognized	$ 440.8
Compensation cost not yet recognized period of recognition	2 years 10 months 24 days

Stockholders' Equity - Employe

Stockholders' Equity - Employee Stock Options (Details) - Stock Options [Member] - USD ($) $ / shares in Units, shares in Millions, $ in Millions	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
Share-based Compensation Arrangement by Share-based Payment Award, Fair Value Assumptions and Methodology [Abstract]
Expected term in years	4 years 4 months 24 days	4 years 4 months 24 days
Volatility	33.50%	34.20%
Risk-free interest rate	1.30%	2.50%
Dividend rate	0.00%	0.00%
Number of Shares
Balance - Beginning (in shares)	2.7
Granted (in shares)	0.5
Forfeited (in shares)	0
Exercised (in shares)	(0.2)
Balance - Ending (in shares)	3
Weighted- Average Exercise Price
Balance - Beginning (in dollars per share)	$ 50.37
Granted (in dollars per share)	114.48
Forfeited (in dollars per share)	59.28
Exercised (in dollars per share)	40.02
Balance - Ending (in dollars per share)	$ 62.41
Share-based Compensation Arrangement by Share-based Payment Award, Options, Additional Disclosures [Abstract]
Options vested and expected to vest, Outstanding (in shares)	3
Options vested and expected to vest, Weighted average exercise price (in dollars per share)	$ 62.41
Options vested and expected to vest, Weighted average remaining contractual life (in years)	4 years 9 months 18 days
Options vested and expected to vest, Aggregate intrinsic value	$ 123.8
Options exercisable, Outstanding (in shares)	1.5
Options exercisable, Weighted average exercise price (in dollars per share)	$ 39.50
Options exercisable, Weighted average remaining contractual life (in years)	3 years 6 months
Options exercisable, Aggregate intrinsic value	$ 90.3
Compensation cost not yet recognized	$ 38.6
Compensation cost not yet recognized period of recognition	3 years 1 month 6 days
Weighted-average fair value per share granted	$ 33.82	$ 27.12
Intrinsic value of options exercised	$ 13.1	$ 27.2
Fair value of options vested	$ 6	$ 4.2

Stockholders' Equity , Allocati

Stockholders' Equity , Allocation of Stock-Based Compensation Expense (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]
Total stock-based compensation expense	$ 45.3	$ 43
Income tax benefit associated with stock-based compensation	10	10
Restricted Stock Units (RSUs) [Member]
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]
Total stock-based compensation expense	42.2	39.2
Stock Options [Member]
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]
Total stock-based compensation expense	3.1	2.5
ESPP [Member]
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]
Total stock-based compensation expense	0	1.3
Cost of product revenue [Member]
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]
Total stock-based compensation expense	0.4	0.4
Cost of service revenue [Member]
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]
Total stock-based compensation expense	3	2.8
Research and development [Member]
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]
Total stock-based compensation expense	10.9	9.4
Sales and marketing [Member]
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]
Total stock-based compensation expense	25.7	25.4
General and administrative [Member]
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]
Total stock-based compensation expense	$ 5.3	$ 5

Stockholders' Equity , Share Re

Stockholders' Equity , Share Repurchase Program (Details) - USD ($) $ / shares in Units, shares in Millions	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019	Jan. 31, 2016
Share Repurchase Program [Line Items]
Stock repurchased in the period, value	$ 899,900,000	$ 56,200,000
Repurchase Program [Member]
Share Repurchase Program [Line Items]
Stock repurchase program, authorized amount			$ 2,500,000,000
Stock repurchased in the period, shares	10
Stock repurchased, average price (in dollars per share)	$ 90.36
Stock repurchased in the period, value	$ 899,900,000
Stock repurchase program, unused balance	$ 692,900,000

Income Taxes , Narrative (Detai

Income Taxes , Narrative (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019	Dec. 31, 2019
Income Tax Disclosure [Abstract]
Effective tax rate (percent)	11.00%	2.00%
U.S. federal and state taxes, withholding taxes and foreign taxes	$ 28.3	$ 17.5
Excess tax benefits on stock compensation	15.2	$ 16
Tax benefit from foreign-derived intangible income deduction	4.8
Increase in unrecognized tax benefits related to Ninth Circuit Altera decision	8.5
Unrecognized tax benefits	65.6		$ 67.5
Unrecognized tax benefits that would favorably affect effective tax rate	60.4
Accrued interest and penalties related to uncertain tax benefits	14.5		$ 14.1
Possible decrease in unrecognized tax benefits (up to)	$ 10.4

Defined Contribution Plans (Det

Defined Contribution Plans (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
Retirement Benefits [Abstract]
Matching contribution on employee contributions, Percent	50.00%
Maximum contribution percentage of each employee's eligible earnings, Percent	4.00%
Matching contributions to the RRSP and 401(k) Plans	$ 2.2	$ 1.7

Segment Information (Details)

Segment Information (Details) $ in Millions	3 Months Ended		12 Months Ended
	Mar. 31, 2020USD ($)reportable_segmentbusiness_activityoperating_segmentsegment_manager	Mar. 31, 2019USD ($)	Dec. 31, 2019USD ($)
Segment Reporting Information [Line Items]
Business activity (in business activities) | business_activity	1
Segment managers responsible for operations (in segment managers) | segment_manager	0
Number of operating segments (in operating segments) | operating_segment	1
Number of reportable segments (in reportable segments) | reportable_segment	1
Total revenue	$ 576.9	$ 472.6
Property and equipment - net	$ 374.2		$ 344.3
Exclusive Networks Group [Member] | Customer Concentration Risk [Member] | Revenue [Member]
Segment Reporting Information [Line Items]
Concentration (percent)	31.00%	30.00%
Exclusive Networks Group [Member] | Customer Concentration Risk [Member] | Accounts Receivable [Member]
Segment Reporting Information [Line Items]
Concentration (percent)	34.00%		36.00%
Ingram Micro [Member] | Customer Concentration Risk [Member] | Revenue [Member]
Segment Reporting Information [Line Items]
Concentration (percent)	10.00%	11.00%
Ingram Micro [Member] | Customer Concentration Risk [Member] | Accounts Receivable [Member]
Segment Reporting Information [Line Items]
Concentration (percent)			10.00%
Americas [Member]
Segment Reporting Information [Line Items]
Total revenue	$ 242.2	$ 200.5
Property and equipment - net	353.7		$ 323.4
U.S.
Segment Reporting Information [Line Items]
Total revenue	181.6	150.3
Property and equipment - net	227.4		197.4
Canada
Segment Reporting Information [Line Items]
Property and equipment - net	120.2		120.5
Latin America
Segment Reporting Information [Line Items]
Property and equipment - net	6.1		5.5
Other Americas
Segment Reporting Information [Line Items]
Total revenue	60.6	50.2
EMEA
Segment Reporting Information [Line Items]
Total revenue	220.7	177.2
Property and equipment - net	14.5		15.2
APAC
Segment Reporting Information [Line Items]
Total revenue	114	$ 94.9
Property and equipment - net	$ 6		$ 5.7

Subsequent Event (Details)

Subsequent Event (Details) - USD ($) shares in Millions, $ in Millions	1 Months Ended	3 Months Ended
	May 06, 2020	Mar. 31, 2020	Mar. 31, 2019
Subsequent Event [Line Items]
Stock repurchased in the period, value		$ 899.9	$ 56.2
Repurchase Program [Member]
Subsequent Event [Line Items]
Stock repurchased in the period, shares		10
Stock repurchased in the period, value		$ 899.9
Subsequent Event [Member] | Repurchase Program [Member]
Subsequent Event [Line Items]
Stock repurchased in the period, shares	1.5
Stock repurchased in the period, value	$ 146.1

Uncategorized Items - ftnt-0331

Label	Element	Value
Cumulative Effect of New Accounting Principle in Period of Adoption	us-gaap_CumulativeEffectOfNewAccountingPrincipleInPeriodOfAdoption	$ 0
AOCI Attributable to Parent [Member]
Cumulative Effect of New Accounting Principle in Period of Adoption	us-gaap_CumulativeEffectOfNewAccountingPrincipleInPeriodOfAdoption	(100,000)
Retained Earnings [Member]
Cumulative Effect of New Accounting Principle in Period of Adoption	us-gaap_CumulativeEffectOfNewAccountingPrincipleInPeriodOfAdoption	$ 100,000