Fortinet (FTNT) 10-Q 3 May 21 2021 Q1 Quarterly report Financial data

Document and Entity Information

Document and Entity Information - shares	3 Months Ended
	Mar. 31, 2021	Apr. 30, 2021
Cover [Abstract]
Document Type	10-Q
Document Quarterly Report	true
Document Period End Date	Mar. 31, 2021
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		163,317,652
Entity Central Index Key	0001262039
Amendment Flag	false
Document Fiscal Year Focus	2021
Document Fiscal Period Focus	Q1
Current Fiscal Year End Date	--12-31

Condensed Consolidated Balance

Condensed Consolidated Balance Sheets - USD ($) $ in Millions	Mar. 31, 2021	Dec. 31, 2020
CURRENT ASSETS:
Cash and cash equivalents	$ 1,860.2	$ 1,061.8
Short-term investments	1,076.7	775.5
Accounts receivable—net	637.3	720
Inventory	149.6	139.8
Prepaid expenses and other current assets	57.4	43.3
Total current assets	3,781.2	2,740.4
LONG-TERM INVESTMENTS	151.1	118.3
PROPERTY AND EQUIPMENT—NET	494.2	448
DEFERRED CONTRACT COSTS	320.2	304.8
DEFERRED TAX ASSETS	260.6	245.2
GOODWILL	99.2	93
OTHER INTANGIBLE ASSETS—NET	32.3	31.6
OTHER ASSETS	143.4	63.2
TOTAL ASSETS	5,282.2	4,044.5
CURRENT LIABILITIES:
Accounts payable	129.5	141.6
Accrued liabilities	143.2	149.2
Accrued payroll and compensation	141.9	145.9
Deferred revenue	1,465.1	1,392.8
Total current liabilities	1,879.7	1,829.5
DEFERRED REVENUE	1,280.5	1,212.5
INCOME TAX LIABILITIES	97.7	90.3
LONG-TERM DEBT	987	0
OTHER LIABILITIES	56.5	56.2
Total liabilities	4,301.4	3,188.5
COMMITMENTS AND CONTINGENCIES (Note 14)
STOCKHOLDERS’ EQUITY:
Common stock, $0.001 par value—300.0 shares authorized; 163.3 and 162.5 shares issued and outstanding at March 31, 2021 and December 31, 2020, respectively	0.2	0.2
Additional paid-in capital	1,225.2	1,207.2
Accumulated other comprehensive income	0.3	0.7
Accumulated deficit	(244.9)	(352.1)
Total stockholders’ equity	980.8	856
TOTAL LIABILITIES AND STOCKHOLDERS’ EQUITY	$ 5,282.2	$ 4,044.5

Condensed Consolidated Balanc_2

Condensed Consolidated Balance Sheets Parenthetical - $ / shares	Mar. 31, 2021	Dec. 31, 2020
Statement of Financial Position [Abstract]
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	163,300,000	162,500,000
Common Stock, shares outstanding	163,300,000	162,500,000

Condensed Consolidated Statemen

Condensed Consolidated Statements of Income - USD ($) shares in Millions, $ in Millions	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020
REVENUE:
Total revenue	$ 710.3	$ 577.7
COST OF REVENUE:
Total cost of revenue	156.6	128.7
GROSS PROFIT:
Total gross profit	553.7	449
OPERATING EXPENSES:
Research and development	97.2	80.3
Sales and marketing	304	260
General and administrative	32	28.8
Gain on intellectual property matter	(1.1)	(36.8)
Total operating expenses	432.1	332.3
OPERATING INCOME	121.6	116.7
INTEREST INCOME (EXPENSE)—NET	(0.2)	9.2
OTHER EXPENSE—NET	(2)	(8)
INCOME BEFORE INCOME TAXES	119.4	117.9
PROVISION FOR INCOME TAXES	12.2	13.3
NET INCOME	$ 107.2	$ 104.6
Net income per share (Note 10):
Basic (in dollars per share)	$ 0.66	$ 0.61
Diluted (in dollars per share)	$ 0.64	$ 0.60
Weighted-average shares outstanding:
Basic (in shares)	163	170.6
Diluted (in shares)	166.4	174.2
Product [Member]
REVENUE:
Total revenue	$ 240.7	$ 192.3
COST OF REVENUE:
Total cost of revenue	91.3	76.3
GROSS PROFIT:
Total gross profit	149.4	116
Service [Member]
REVENUE:
Total revenue	469.6	385.4
COST OF REVENUE:
Total cost of revenue	65.3	52.4
GROSS PROFIT:
Total gross profit	$ 404.3	$ 333

Condensed Consolidated Statem_2

Condensed Consolidated Statements of Comprehensive Income - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020
Statement of Comprehensive Income [Abstract]
Net income	$ 107.2	$ 104.6
Other comprehensive loss:
Change in unrealized gains (losses) on investments	(0.6)	(5.2)
Less: tax benefit related to change in unrealized gains (losses) on investments	(0.2)	(1)
Other comprehensive loss	(0.4)	(4.2)
Comprehensive income	$ 106.8	$ 100.4

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, 2019		171.7
Balance at Dec. 31, 2019	$ 1,342.4	$ 0.2	$ 1,180.3	$ 1.1	$ 160.8
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 loss on investments - net of tax	(4.2)			(4.2)
Net income	104.6				104.6
Balance, shares at Mar. 31, 2020		162.6
Balance at Mar. 31, 2020	557.4	$ 0.2	1,128.4	(3.1)	(568.1)
Balance, shares at Dec. 31, 2020		162.5
Balance at Dec. 31, 2020	856	$ 0.2	1,207.2	0.7	(352.1)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Issuance of common stock in connection with equity incentive plans - net of tax withholding (in shares)		0.8
Issuance of common stock in connection with equity incentive plans - net of tax withholding	(31.5)		(31.5)
Stock-based compensation expense	49.5		49.5
Net unrealized loss on investments - net of tax	(0.4)			(0.4)
Net income	107.2				107.2
Balance, shares at Mar. 31, 2021		163.3
Balance at Mar. 31, 2021	$ 980.8	$ 0.2	$ 1,225.2	$ 0.3	$ (244.9)

Condensed Consolidated Statem_4

Condensed Consolidated Statements of Cash Flows - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020
CASH FLOWS FROM OPERATING ACTIVITIES:
Net income	$ 107.2	$ 104.6
Adjustments to reconcile net income to net cash provided by operating activities:
Stock-based compensation	49.5	44.8
Amortization of deferred contract costs	39.7	31.3
Depreciation and amortization	17.3	17.6
Amortization of investment premiums (discounts)	1.2	(0.6)
Other	0.4	4.3
Changes in operating assets and liabilities:
Accounts receivable—net	82.5	69.6
Inventory	(14.7)	6.7
Prepaid expenses and other current assets	(13.4)	(12.9)
Deferred contract costs	(55.2)	(43)
Deferred tax assets	(15.2)	7.3
Other assets	(4.8)	0.9
Accounts payable	(12.4)	(9)
Accrued liabilities	(2.8)	1.8
Accrued payroll and compensation	(3.9)	1.8
Other liabilities	0.2	4.1
Deferred revenue	140.3	90.1
Net cash provided by operating activities	315.9	319.4
CASH FLOWS FROM INVESTING ACTIVITIES:
Purchases of investments	(647.1)	(368.3)
Sales of investments	18.6	126.8
Maturities of investments	292.4	277.2
Purchases of property and equipment	(52.1)	(27.6)
Purchase of investment in privately held company	(75)	0
Payments made in connection with business combination, net of cash acquired	(10.3)	(3.1)
Other	0	(0.4)
Net cash provided by (used in) investing activities	(473.5)	4.6
CASH FLOWS FROM FINANCING ACTIVITIES:
Proceeds from long-term debt, net of discount and underwriting fees	989.4	0
Payments for debt issuance costs	(1.9)	0
Repurchase and retirement of common stock	0	(889.9)
Proceeds from issuance of common stock	9.9	7.4
Taxes paid related to net share settlement of equity awards	(41.4)	(37.8)
Other	0	(0.1)
Net cash provided by (used in) financing activities	956	(920.4)
NET INCREASE (DECREASE) IN CASH AND CASH EQUIVALENTS	798.4	(596.4)
CASH AND CASH EQUIVALENTS—Beginning of period	1,061.8	1,222.5
CASH AND CASH EQUIVALENTS—End of period	1,860.2	626.1
SUPPLEMENTAL DISCLOSURES OF CASH FLOW INFORMATION:
Operating lease liabilities arising from obtaining right-of-use assets	9.8	2.4
NON-CASH INVESTING AND FINANCING ACTIVITIES:
Transfers of evaluation units from inventory to property and equipment	5.1	6.3
Liability for purchase of property and equipment	34.3	25.9
Liability incurred for repurchase of common stock	0	10
Liability incurred in connection with business acquisition	$ 0.5	$ 0

Summary of Significant Accounti

Summary of Significant Accounting Policies	3 Months Ended
	Mar. 31, 2021
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, 2020, contained in our Annual Report on Form 10-K filed with the SEC on February 19, 2021. 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, 2021 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, 2020 is derived from the audited consolidated financial statements for the year ended December 31, 2020. 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, 2021. Recently Adopted Accounting Standards Income Taxes In December 2019, the Financial Accounting Standards Board (the “FASB”) issued Accounting Standards Update (“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 was effective for us beginning on January 1, 2021. The adoption of this guidance did not have any impact on our condensed consolidated financial statements and accompanying disclosures.

Immaterial Correction of Prior

Immaterial Correction of Prior Period Financial Statements	3 Months Ended
	Mar. 31, 2021
Accounting Changes and Error Corrections [Abstract]
IMMATERIAL CORRECTION OF PRIOR PERIOD FINANCIAL STATEMENTS	IMMATERIAL CORRECTION OF PRIOR PERIOD FINANCIAL STATEMENTS Subsequent to the issuance of our condensed consolidated financial statements for the period ended March 31, 2020, we identified an immaterial error related to the commencement of revenue recognition for certain FortiCare support service contracts. Rather than commencing recognition upon end user registration, we should have commenced recognition when control had passed to the distributor, which we have determined is our customer. We assessed the effect of this correction, individually and in the aggregate, on prior periods’ financial statements in accordance with the SEC’s Staff Accounting Bulletin Nos. 99 and 108 and, based on an analysis of quantitative and qualitative factors, determined that the correction was not individually material to any of our prior interim or annual consolidated financial statements. All financial information contained in the accompanying notes to these condensed consolidated financial statements has been revised to reflect the correction of this error. The corrections to our condensed consolidated statement of income for the three months ended March 31, 2020 were as follows (in millions, except per share amounts): Three Months Ended March 31, 2020 As Previously Reported Corrections As Corrected REVENUE: Service $ 384.6 $ 0.8 $ 385.4 Total revenue 576.9 0.8 577.7 GROSS PROFIT: Service 332.2 0.8 333.0 Total gross profit 448.2 0.8 449.0 OPERATING INCOME 115.9 0.8 116.7 INCOME BEFORE INCOME TAXES 117.1 0.8 117.9 PROVISION FOR INCOME TAXES 13.1 0.2 13.3 NET INCOME $ 104.0 $ 0.6 $ 104.6 Net income per share (Note 10): Basic $ 0.61 $ — $ 0.61 Diluted $ 0.60 $ — $ 0.60 The corrections to our condensed consolidated statement of cash flows for the three months ended March 31, 2020 were as follows (in millions): Three Months Ended March 31, 2020 As Previously Reported Corrections As Corrected CASH FLOWS FROM OPERATING ACTIVITIES: Net income $ 104.0 $ 0.6 $ 104.6 Changes in operating assets and liabilities: Deferred tax assets 7.1 0.2 7.3 Deferred revenue 90.9 (0.8) 90.1 For the period in which we corrected net income, we made corresponding corrections to net income and comprehensive income in our condensed consolidated statement of comprehensive income and to net income, retained earnings (accumulated deficit) and total stockholders’ equity in our condensed consolidated statements of stockholders’ equity.

Revenue Recognition

Revenue Recognition	3 Months Ended
	Mar. 31, 2021
Revenue from Contract with Customer [Abstract]
REVENUE RECOGNITION	REVENUE RECOGNITIONWe sell cybersecurity solutions to a variety of organizations, such as enterprises, communication service providers, government organizations and small to medium-sized enterprises. Our revenue consists of product and service revenue. Product revenue is generated by our FortiGate network security products, our Fortinet Security Fabric platform products and other products. Service revenue relates to sales of our security subscription services, which mainly consists of our FortiGuard security solutions, as well as our 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 $ 240.7 $ 192.3 Service: Security subscription 255.3 211.4 Technical support and other 214.3 174.0 Total service revenue 469.6 385.4 Total revenue $ 710.3 $ 577.7 Deferred Revenue During the three months ended March 31, 2021 and March 31, 2020, we recognized $417.9 million and $343.3 million in service revenue that was included in the deferred revenue balance as of December 31, 2020 and December 31, 2019, respectively. Transaction Price Allocated to the Remaining Performance Obligations As of March 31, 2021, the aggregate amount of the transaction price allocated to remaining performance obligations was $2.75 billion, which was substantially comprised of deferred security subscription and technical support services revenue. We expect to recognize approximately $1.47 billion as revenue over the next 12 months and the remainder thereafter. Accounts receivable Trade accounts receivable are recorded at the invoiced amount. Our accounts receivable balance is reduced by an allowance for expected credit losses. We measure expected credit losses of accounts receivable on a collective (pooled) 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. Expected credit losses are recorded as general and administrative expenses on our consolidated statements of income. The allowance for credit losses was $3.1 million and $2.5 million as of March 31, 2021 and December 31, 2020, respectively. Provisions, write-offs and recoveries were not material during the three months ended March 31, 2021 and 2020. Deferred Contract Costs

Financial Instruments and Fair

Financial Instruments and Fair Value	3 Months Ended
	Mar. 31, 2021
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, 2021 Amortized Unrealized Unrealized Fair Corporate debt securities $ 482.1 $ 0.5 $ (0.2) $ 482.4 Commercial paper 426.4 0.1 — 426.5 Certificates of deposit and term deposits (1) 162.7 — — 162.7 U.S. government securities 156.2 — — 156.2 Total available-for-sale securities $ 1,227.4 $ 0.6 $ (0.2) $ 1,227.8 December 31, 2020 Amortized Unrealized Unrealized Fair Corporate debt securities $ 410.5 $ 1.0 $ — $ 411.5 Commercial paper 185.4 — — 185.4 Certificates of deposit and term deposits (1) 112.0 — — 112.0 U.S. government securities 184.9 — — 184.9 Total available-for-sale securities $ 892.8 $ 1.0 $ — $ 893.8 (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, 2021 Less Than 12 Months 12 Months or Greater Total Fair Unrealized Fair Unrealized Fair Unrealized Corporate debt securities $ 272.2 $ (0.2) $ — $ — $ 272.2 $ (0.2) Commercial paper 164.1 — — — 164.1 — Certificates of deposit and term deposits 29.5 — 5.5 — 35.0 — Total available-for-sale securities $ 465.8 $ (0.2) $ 5.5 $ — $ 471.3 $ (0.2) December 31, 2020 Less Than 12 Months 12 Months or Greater Total Fair Unrealized Fair Unrealized Fair Unrealized Corporate debt securities $ 111.3 $ — $ — $ — $ 111.3 $ — Commercial paper 61.5 — — — 61.5 — U.S. government securities 38.1 — — — 38.1 — Certificates of deposit and term deposits 29.5 — — — 29.5 — Total available-for-sale securities $ 240.4 $ — $ — $ — $ 240.4 $ — The contractual maturities of our investments were as follows (in millions): March 31, December 31, Due within one year $ 1,076.7 $ 775.5 Due within one to three years 151.1 118.3 Total $ 1,227.8 $ 893.8 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 receivable of $2.6 million as of March 31, 2021 was excluded from the fair value of our available-for-sale securities and was recorded in prepaid expenses and other current assets in our condensed consolidated balance sheet. Realized gains and losses on available-for-sale securities were insignificant in the periods presented. 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 (in millions): March 31, 2021 December 31, 2020 Aggregate Quoted Significant Significant Aggregate Quoted Significant Significant (Level 1) (Level 2) (Level 3) (Level 1) (Level 2) (Level 3) Assets: Corporate debt securities $ 489.6 $ 489.6 $ — $ 413.7 $ — $ 413.7 $ — Commercial paper 463.2 — 463.2 — 197.2 — 197.2 — U.S. government securities 156.2 156.2 — — 184.9 184.9 — — Certificates of deposit and term deposits 169.2 — 169.2 — 112.0 — 112.0 — Money market funds 282.8 282.8 — — 152.7 152.7 — — Total $ 1,561.0 $ 439.0 $ 1,122.0 $ — $ 1,060.5 $ 337.6 $ 722.9 $ — Reported as: Cash equivalents $ 333.2 $ 166.7 Short-term investments 1,076.7 775.5 Long-term investments 151.1 118.3 Total $ 1,561.0 $ 1,060.5 There were no transfers between Level 1 and Level 2 of the fair value hierarchy during the three months ended March 31, 2021 and year ended December 31, 2020.

Inventory

Inventory	3 Months Ended
	Mar. 31, 2021
Inventory Disclosure [Abstract]
INVENTORY	INVENTORY Inventory consisted of the following (in millions): March 31, December 31, Raw materials $ 15.2 $ 13.8 Finished goods 134.4 126.0 Inventory $ 149.6 $ 139.8

Property and Equipment_Net

Property and Equipment—Net	3 Months Ended
	Mar. 31, 2021
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 $ 106.8 $ 93.3 Building and building improvements 153.8 150.6 Computer equipment and software 146.4 137.2 Leasehold improvements 33.6 31.9 Evaluation units 18.7 19.8 Furniture and fixtures 22.1 21.3 Construction-in-progress 193.4 166.4 Total property and equipment 674.8 620.5 Less: accumulated depreciation (180.6) (172.5) Property and equipment—net $ 494.2 $ 448.0 Construction-in-progress consists primarily of costs incurred in connection with the construction of a second building at our headquarters campus.

Investments in Privately-Held C

Investments in Privately-Held Companies	3 Months Ended
	Mar. 31, 2021
Investments, All Other Investments [Abstract]
INVESTMENTS IN PRIVATELY-HELD COMPANIES	INVESTMENTS IN PRIVATELY HELD COMPANIES Linksys Holdings, Inc. On March 19, 2021, we invested $75.0 million in cash for shares of the Series A Preferred Stock of Linksys Holdings, Inc. (“Linksys”), which provides router connectivity solutions, for a 32.6% ownership interest in the outstanding capital stock of Linksys. We concluded that our investment is an in-substance common-stock investment, and, though we do not hold a controlling financial interest in Linksys, we have the ability to exercise significant influence over the operating and financial policies of Linksys. Therefore, we will account for this investment using the equity method of accounting. As of March 31, 2021, the investment was included in other assets on our condensed consolidated balance sheet. Our share of the earnings of Linksys subsequent to the acquisition date was not material for the quarter ended March 31, 2021. Transaction costs related to this investment were not material. Our other investments in the equity securities of privately held companies without readily determinable fair values totaled $1.0 million as of March 31, 2021 and December 31, 2020.

Business Combinations

Business Combinations	3 Months Ended
	Mar. 31, 2021
Business Combinations [Abstract]
BUSINESS COMBINATIONS	BUSINESS COMBINATIONShieldX Networks, Inc. On March 10, 2021, we closed an acquisition of certain assets and liabilities of ShieldX Networks Inc. ( “ ShieldX ”

Goodwill and Other Intangible A

Goodwill and Other Intangible Assets - Net	3 Months Ended
	Mar. 31, 2021
Goodwill and Intangible Assets Disclosure [Abstract]
GOODWILL AND OTHER INTANGIBLE ASSETS - Net	GOODWILL AND OTHER INTANGIBLE ASSETS—Net Goodwill The following table presents the changes in the carrying amount of goodwill (in millions): Amount Balance—December 31, 2020 $ 93.0 Addition due to business combination 6.2 Balance—March 31, 2021 $ 99.2 There were no impairments to goodwill during the three months ended March 31, 2021 or during prior periods. Other Intangible Assets—Net The following tables present other intangible assets—net (in millions, except years): March 31, 2021 Weighted-Average Useful Life (in Years) Gross Accumulated Amortization Net Other intangible assets—net: Finite-lived intangible assets: Developed technologies 4.0 $ 63.4 $ 34.8 $ 28.6 Customer relationships 4.0 24.8 21.1 3.7 Total other intangible assets—net $ 88.2 $ 55.9 $ 32.3 December 31, 2020 Weighted-Average Useful Life (in Years) Gross Accumulated Amortization Net Other intangible assets—net: Finite-lived intangible assets: Developed technologies 4.0 $ 59.3 $ 32.3 $ 27.0 Customer relationships 4.0 24.8 20.2 4.6 Total other intangible assets—net $ 84.1 $ 52.5 $ 31.6 Amortization expense was $3.4 million and $4.0 million during the three months ended March 31, 2021 and 2020, respectively. The following table summarizes estimated future amortization expense of finite-lived intangible assets—net (in millions): Amount Years: 2021 (the remainder of 2021) $ 10.5 2022 10.7 2023 7.6 2024 3.2 2025 0.3 Total $ 32.3

Net Income Per Share

Net Income Per Share	3 Months Ended
	Mar. 31, 2021
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 (“RSUs”) 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 $ 107.2 $ 104.6 Denominator: Basic shares: Weighted-average common stock outstanding-basic 163.0 170.6 Diluted shares: Weighted-average common stock outstanding-basic 163.0 170.6 Effect of potentially dilutive securities: RSUs 2.0 2.4 Stock options 1.4 1.2 Weighted-average shares used to compute diluted net income per share 166.4 174.2 Net income per share: Basic $ 0.66 $ 0.61 Diluted $ 0.64 $ 0.60 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 0.4 0.6 Stock options 0.3 0.3 Total 0.7 0.9

Leases

Leases	3 Months Ended
	Mar. 31, 2021
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 six years. Unless and until we are reasonably certain we will exercise these renewal options, 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. 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 March 31, March 31, Operating lease expense $ 5.9 $ 4.3 Variable lease expense (1) 0.8 0.6 Short-term lease expense 0.8 0.9 Total lease expense $ 7.5 $ 5.8 (1) Variable lease expense for the three months ended March 31, 2021 and 2020 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 $ 53.9 $ 49.3 Operating lease liabilities - current Accrued liabilities $ 20.6 $ 19.1 Operating lease liabilities - non-current Other liabilities 35.8 34.0 Total operating lease liabilities $ 56.4 $ 53.1 Weighted average remaining lease term in years - operating leases 3.4 3.5 Weighted average discount rate - operating leases 2.8 % 3.2 % Supplemental cash flow information related to leases was as follows (in millions): 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 $ 6.1 $ 4.6 Maturities of operating lease liabilities as of March 31, 2021 were as follows (in millions): Year Ending December 31, Amount 2021 (the remainder of 2021) $ 16.5 2022 17.8 2023 12.0 2024 7.5 2025 3.9 Thereafter 1.4 Total lease payments 59.1 Less imputed interest (2.7) Total $ 56.4 As of March 31, 2021, we had additional minimum lease payments of $2.7 million relating to operating leases for colocation space that had been signed but had not yet commenced. These leases will commence during 2021 and will have lease
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 six years. Unless and until we are reasonably certain we will exercise these renewal options, 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. 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 March 31, March 31, Operating lease expense $ 5.9 $ 4.3 Variable lease expense (1) 0.8 0.6 Short-term lease expense 0.8 0.9 Total lease expense $ 7.5 $ 5.8 (1) Variable lease expense for the three months ended March 31, 2021 and 2020 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 $ 53.9 $ 49.3 Operating lease liabilities - current Accrued liabilities $ 20.6 $ 19.1 Operating lease liabilities - non-current Other liabilities 35.8 34.0 Total operating lease liabilities $ 56.4 $ 53.1 Weighted average remaining lease term in years - operating leases 3.4 3.5 Weighted average discount rate - operating leases 2.8 % 3.2 % Supplemental cash flow information related to leases was as follows (in millions): 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 $ 6.1 $ 4.6 Maturities of operating lease liabilities as of March 31, 2021 were as follows (in millions): Year Ending December 31, Amount 2021 (the remainder of 2021) $ 16.5 2022 17.8 2023 12.0 2024 7.5 2025 3.9 Thereafter 1.4 Total lease payments 59.1 Less imputed interest (2.7) Total $ 56.4 As of March 31, 2021, we had additional minimum lease payments of $2.7 million relating to operating leases for colocation space that had been signed but had not yet commenced. These leases will commence during 2021 and will have lease

Debt

Debt	3 Months Ended
	Mar. 31, 2021
Debt Disclosure [Abstract]
DEBT	DEBT On March 5, 2021, we issued $1.0 billion aggregate principal amount of senior notes (collectively, the “Senior Notes”), consisting of $500.0 million aggregate principal amount of 1.0% notes due March 15, 2026 (the “2026 Senior Notes”) and $500.0 million aggregate principal amount of 2.2% notes due March 15, 2031 (the “2031 Senior Notes”), in an underwritten registered public offering. The Senior Notes are senior unsecured obligations and rank equally with each other in right of payment and with our other outstanding obligations. We may redeem the Senior Notes at any time in whole or in part for cash, at specified redemption prices that include accrued and unpaid interest, if any, and a make-whole premium. However, no make-whole premium will be paid for redemptions of the 2026 Senior Notes on or after February 15, 2026, or the 2031 Senior Notes on or after December 15, 2030. Interest on the Senior Notes is payable on March 15 and September 15 of each year, beginning on September 15, 2021. As of March 31, 2021, the Senior Notes were recorded as long-term debt, net of discount and issuance costs, which are amortized to interest expense over the respective contractual terms of these notes using the effective interest method. The total outstanding debt is summarized below (in millions, except percentages): Maturity Coupon Rate Effective Interest Rate March 31, 2021 Debt 2026 Senior Notes March 2026 1.0 % 1.3 % $ 500.0 2031 Senior Notes March 2031 2.2 % 2.3 % 500.0 Total debt 1,000.0 Less: Unamortized discount and debt issuance costs (13.0) Total long-term debt $ 987.0 As of March 31, 2021 we accrued interest payable of $1.2 million, and there are no financial covenants with which we must comply. During the quarter ended March 31, 2021 we recorded $1.3 million of total interest expense in relation to these Senior Notes. The total estimated fair value of the outstanding Senior Notes was approximately $975.6 million, including accrued and unpaid interest, as of March 31, 2021. The fair value was determined based on observable market prices of identical instruments in less active markets. The estimated fair values are based on Level 2 inputs.

Mutual Covenant-Not-to-Sue and

Mutual Covenant-Not-to-Sue and Release Agreement	3 Months Ended
	Mar. 31, 2021
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.

Commitments and Contingencies

Commitments and Contingencies	3 Months Ended
	Mar. 31, 2021
Commitments and Contingencies Disclosure [Abstract]
COMMITMENTS AND CONTINGENCIES	COMMITMENTS AND CONTINGENCIES The following table summarizes our inventory purchase commitments as of March 31, 2021 (in millions): Total 2021 2022 2023 2024 2025 Thereafter Inventory purchase commitments $ 298.8 $ 298.7 $ 0.1 $ — $ — $ — $ — 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, 2021, we had $298.8 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, 2021, we had $65.1 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. Litigation loss contingency accruals were not material as of March 31, 2021 and December 31, 2020. 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. Although from time to time there are indemnification claims asserted against us and currently there are pending indemnification claims, to date there have been no material awards under such indemnification provisions. Similar to other security companies and companies in other industries, we have in the past experienced, and we may in the future experience, cybersecurity threats, malicious activity directed against our information technology infrastructure or unauthorized attempts to gain access to our and our customers’ sensitive information and systems. We currently are unaware of any existing claims or proceedings related to these types of matters, including any that we believe are likely to have a material adverse effect on our financial position.

Stockholders' Equity

Stockholders' Equity	3 Months Ended
	Mar. 31, 2021
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 RSUs and stock options. As of March 31, 2021, there were a total of 11.4 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 RSUs 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, 2020 4.7 $ 90.46 Granted 0.8 172.74 Forfeited (0.1) 100.57 Vested (0.8) 79.95 Balance—March 31, 2021 4.6 $ 107.37 Stock compensation expense is recognized on a straight-line basis over the vesting period of each RSU. As of March 31, 2021, total compensation expense related to unvested RSUs granted to employees and non-employees under the Amended Plan, but not yet recognized, was $450.7 million, with a weighted-average remaining vesting period of 2.9 years. RSUs settle into shares of common stock upon vesting. Upon the vesting of the RSUs, we net-settle the RSUs and withhold a portion of the shares to satisfy employee withholding tax requirements. The payment of the withheld taxes 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 0.3 Amount withheld for taxes $ 41.4 $ 37.8 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 39.5 % 33.5 % Risk-free interest rate 0.5 % 1.3 % 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 Weighted- Weighted- Aggregate Balance—December 31, 2020 2.7 $ 67.53 4.2 220.4 Granted 0.5 171.93 Forfeited — 109.16 Exercised (0.2) 50.36 Balance—March 31, 2021 3.0 $ 85.66 Options vested and expected to vest—March 31, 2021 3.0 $ 85.66 4.5 $ 297.1 Options exercisable—March 31, 2021 1.5 $ 51.63 3.3 $ 205.8 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, 2021 for all in-the-money stock options. Stock compensation expense is recognized on a straight-line basis over the vesting period of each stock option. As of March 31, 2021, total compensation expense related to unvested stock options granted to employees but not yet recognized was $54.6 million, with a weighted-average remaining vesting period of 3.2 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 $ 56.49 $ 33.82 Intrinsic value of options exercised $ 22.3 $ 13.1 Fair value of options vested $ 7.0 $ 6.0 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 3.5 3.0 Research and development 13.0 10.9 Sales and marketing 26.8 25.7 General and administrative 6.3 5.3 Total stock-based compensation expense $ 50.0 $ 45.3 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 $ 45.8 $ 42.2 Stock options 4.2 3.1 Total stock-based compensation expense $ 50.0 $ 45.3 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 $ 11.0 $ 10.0 Share Repurchase Program In July 2020, under the Share Repurchase Program originally approved by our board of directors in January 2016 (the “Repurchase Program”), our board of directors approved a $500.0 million increase and extended the term to February 28, 2022, bringing the aggregate amount authorized to be repurchased to $3.0 billion. 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. There were no shares repurchased under the Repurchase Program during the three months ended March 31, 2021. As of March 31, 2021, $1.01 billion remained available for future share repurchases under the Repurchase Program.

Income Taxes

Income Taxes	3 Months Ended
	Mar. 31, 2021
Income Tax Disclosure [Abstract]
INCOME TAXES	INCOME TAXES Our effective tax rate was 10% for the three months ended March 31, 2021, compared to an effective tax rate of 11% 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, the tax benefit from foreign-derived intangible income deduction (the “FDII deduction”) and excess tax benefits from stock-based compensation expense. The tax rates for the three months ended March 31, 2021 and 2020 were composed of U.S. federal and state taxes, withholding taxes and foreign taxes that amounted to $35.7 million and $33.3 million, respectively. The tax rate for the three months ended March 31, 2021 was impacted by a tax benefit of $7.3 million from the FDII deduction and by excess tax benefits from stock-based compensation expense of $16.2 million. The tax rate for the three months ended March 31, 2020 was impacted by a tax benefit of $4.8 million from the FDII deduction and excess tax benefits from stock-based compensation expense of $15.2 million. As of March 31, 2021 and December 31, 2020, unrecognized tax benefits were $81.6 million and $77.3 million, respectively. If recognized, $74.6 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 unrecognized tax benefits in income tax expense. As of March 31, 2021 and December 31, 2020, accrued interest and penalties were $16.0 million and $14.5 million, respectively. It is reasonably possible that our gross unrecognized tax benefits will decrease by up to $4.4 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, Germany and several other foreign jurisdictions. The focus of these audits is the inter-company profit allocation.

Defined Contribution Plans

Defined Contribution Plans	3 Months Ended
	Mar. 31, 2021
Retirement Benefits [Abstract]
DEFINED CONTRIBUTION PLANS	DEFINED CONTRIBUTION PLANSOur 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, 2021 and 2020 were $2.7 million and $2.2 million, respectively.

Segment Information

Segment Information	3 Months Ended
	Mar. 31, 2021
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 $ 212.5 $ 181.9 Other Americas 78.4 60.7 Total Americas 290.9 242.6 Europe, Middle East and Africa (“EMEA”) 275.7 221.0 Asia Pacific (“APAC”) 143.7 114.1 Total revenue $ 710.3 $ 577.7 Property and Equipment — net March 31, December 31, Americas: United States $ 342.7 $ 296.3 Canada 120.2 121.3 Latin America 2.1 2.0 Total Americas 465.0 419.6 EMEA 22.3 20.6 APAC 6.9 7.8 Total property and equipment—net $ 494.2 $ 448.0 The following distributors accounted for 10% or more of our revenue: Three Months Ended March 31, March 31, Exclusive Networks Group (“Exclusive”) 32 % 31 % Ingram Micro, Inc. (“Ingram Micro”) 11 % 10 % The following distributors accounted for 10% or more of net accounts receivable: March 31, December 31, Exclusive 31 % 34 % Ingram Micro 16 % 11 %

Summary of Significant Accoun_2

Summary of Significant Accounting Policies (Policies)	3 Months Ended
	Mar. 31, 2021
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, 2020, contained in our Annual Report on Form 10-K filed with the SEC on February 19, 2021. 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, 2021 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, 2020 is derived from the audited consolidated financial statements for the year ended December 31, 2020. 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, 2021.
Recently Adopted Accounting Standards	Recently Adopted Accounting Standards Income Taxes In December 2019, the Financial Accounting Standards Board (the “FASB”) issued Accounting Standards Update (“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 was effective for us beginning on January 1, 2021. The adoption of this guidance did not have any impact on our condensed consolidated financial statements and accompanying disclosures.

Immaterial Correction of Prio_2

Immaterial Correction of Prior Period Financial Statements (Tables)	3 Months Ended
	Mar. 31, 2021
Accounting Changes and Error Corrections [Abstract]
Schedule of Effects of Corrections to Prior Period Financial Statements	The corrections to our condensed consolidated statement of income for the three months ended March 31, 2020 were as follows (in millions, except per share amounts): Three Months Ended March 31, 2020 As Previously Reported Corrections As Corrected REVENUE: Service $ 384.6 $ 0.8 $ 385.4 Total revenue 576.9 0.8 577.7 GROSS PROFIT: Service 332.2 0.8 333.0 Total gross profit 448.2 0.8 449.0 OPERATING INCOME 115.9 0.8 116.7 INCOME BEFORE INCOME TAXES 117.1 0.8 117.9 PROVISION FOR INCOME TAXES 13.1 0.2 13.3 NET INCOME $ 104.0 $ 0.6 $ 104.6 Net income per share (Note 10): Basic $ 0.61 $ — $ 0.61 Diluted $ 0.60 $ — $ 0.60 The corrections to our condensed consolidated statement of cash flows for the three months ended March 31, 2020 were as follows (in millions): Three Months Ended March 31, 2020 As Previously Reported Corrections As Corrected CASH FLOWS FROM OPERATING ACTIVITIES: Net income $ 104.0 $ 0.6 $ 104.6 Changes in operating assets and liabilities: Deferred tax assets 7.1 0.2 7.3 Deferred revenue 90.9 (0.8) 90.1

Revenue Recognition (Tables)

Revenue Recognition (Tables)	3 Months Ended
	Mar. 31, 2021
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 $ 240.7 $ 192.3 Service: Security subscription 255.3 211.4 Technical support and other 214.3 174.0 Total service revenue 469.6 385.4 Total revenue $ 710.3 $ 577.7

Financial Instruments and Fai_2

Financial Instruments and Fair Value (Tables)	3 Months Ended
	Mar. 31, 2021
Financial Instruments and Fair Value [Abstract]
Summary of Investments	The following tables summarize our investments (in millions): March 31, 2021 Amortized Unrealized Unrealized Fair Corporate debt securities $ 482.1 $ 0.5 $ (0.2) $ 482.4 Commercial paper 426.4 0.1 — 426.5 Certificates of deposit and term deposits (1) 162.7 — — 162.7 U.S. government securities 156.2 — — 156.2 Total available-for-sale securities $ 1,227.4 $ 0.6 $ (0.2) $ 1,227.8 December 31, 2020 Amortized Unrealized Unrealized Fair Corporate debt securities $ 410.5 $ 1.0 $ — $ 411.5 Commercial paper 185.4 — — 185.4 Certificates of deposit and term deposits (1) 112.0 — — 112.0 U.S. government securities 184.9 — — 184.9 Total available-for-sale securities $ 892.8 $ 1.0 $ — $ 893.8 (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, 2021 Less Than 12 Months 12 Months or Greater Total Fair Unrealized Fair Unrealized Fair Unrealized Corporate debt securities $ 272.2 $ (0.2) $ — $ — $ 272.2 $ (0.2) Commercial paper 164.1 — — — 164.1 — Certificates of deposit and term deposits 29.5 — 5.5 — 35.0 — Total available-for-sale securities $ 465.8 $ (0.2) $ 5.5 $ — $ 471.3 $ (0.2) December 31, 2020 Less Than 12 Months 12 Months or Greater Total Fair Unrealized Fair Unrealized Fair Unrealized Corporate debt securities $ 111.3 $ — $ — $ — $ 111.3 $ — Commercial paper 61.5 — — — 61.5 — U.S. government securities 38.1 — — — 38.1 — Certificates of deposit and term deposits 29.5 — — — 29.5 — Total available-for-sale securities $ 240.4 $ — $ — $ — $ 240.4 $ —
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 $ 1,076.7 $ 775.5 Due within one to three years 151.1 118.3 Total $ 1,227.8 $ 893.8
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 (in millions): March 31, 2021 December 31, 2020 Aggregate Quoted Significant Significant Aggregate Quoted Significant Significant (Level 1) (Level 2) (Level 3) (Level 1) (Level 2) (Level 3) Assets: Corporate debt securities $ 489.6 $ 489.6 $ — $ 413.7 $ — $ 413.7 $ — Commercial paper 463.2 — 463.2 — 197.2 — 197.2 — U.S. government securities 156.2 156.2 — — 184.9 184.9 — — Certificates of deposit and term deposits 169.2 — 169.2 — 112.0 — 112.0 — Money market funds 282.8 282.8 — — 152.7 152.7 — — Total $ 1,561.0 $ 439.0 $ 1,122.0 $ — $ 1,060.5 $ 337.6 $ 722.9 $ — Reported as: Cash equivalents $ 333.2 $ 166.7 Short-term investments 1,076.7 775.5 Long-term investments 151.1 118.3 Total $ 1,561.0 $ 1,060.5

Inventory (Tables)

Inventory (Tables)	3 Months Ended
	Mar. 31, 2021
Inventory Disclosure [Abstract]
Inventory	Inventory consisted of the following (in millions): March 31, December 31, Raw materials $ 15.2 $ 13.8 Finished goods 134.4 126.0 Inventory $ 149.6 $ 139.8

Property and Equipment_Net (Tab

Property and Equipment—Net (Tables)	3 Months Ended
	Mar. 31, 2021
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 $ 106.8 $ 93.3 Building and building improvements 153.8 150.6 Computer equipment and software 146.4 137.2 Leasehold improvements 33.6 31.9 Evaluation units 18.7 19.8 Furniture and fixtures 22.1 21.3 Construction-in-progress 193.4 166.4 Total property and equipment 674.8 620.5 Less: accumulated depreciation (180.6) (172.5) Property and equipment—net $ 494.2 $ 448.0

Goodwill and Other Intangible_2

Goodwill and Other Intangible Assets - Net (Tables)	3 Months Ended
	Mar. 31, 2021
Goodwill and Intangible Assets Disclosure [Abstract]
Changes in Carrying Amount of Goodwill	The following table presents the changes in the carrying amount of goodwill (in millions): Amount Balance—December 31, 2020 $ 93.0 Addition due to business combination 6.2 Balance—March 31, 2021 $ 99.2
Schedule of Finite-Lived Intangible Assets by Major Class	The following tables present other intangible assets—net (in millions, except years): March 31, 2021 Weighted-Average Useful Life (in Years) Gross Accumulated Amortization Net Other intangible assets—net: Finite-lived intangible assets: Developed technologies 4.0 $ 63.4 $ 34.8 $ 28.6 Customer relationships 4.0 24.8 21.1 3.7 Total other intangible assets—net $ 88.2 $ 55.9 $ 32.3 December 31, 2020 Weighted-Average Useful Life (in Years) Gross Accumulated Amortization Net Other intangible assets—net: Finite-lived intangible assets: Developed technologies 4.0 $ 59.3 $ 32.3 $ 27.0 Customer relationships 4.0 24.8 20.2 4.6 Total other intangible assets—net $ 84.1 $ 52.5 $ 31.6
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: 2021 (the remainder of 2021) $ 10.5 2022 10.7 2023 7.6 2024 3.2 2025 0.3 Total $ 32.3

Net Income Per Share (Tables)

Net Income Per Share (Tables)	3 Months Ended
	Mar. 31, 2021
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 $ 107.2 $ 104.6 Denominator: Basic shares: Weighted-average common stock outstanding-basic 163.0 170.6 Diluted shares: Weighted-average common stock outstanding-basic 163.0 170.6 Effect of potentially dilutive securities: RSUs 2.0 2.4 Stock options 1.4 1.2 Weighted-average shares used to compute diluted net income per share 166.4 174.2 Net income per share: Basic $ 0.66 $ 0.61 Diluted $ 0.64 $ 0.60
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 0.4 0.6 Stock options 0.3 0.3 Total 0.7 0.9

Leases (Tables)

Leases (Tables)	3 Months Ended
	Mar. 31, 2021
Leases [Abstract]
Components of Lease Expense and Supplemental Cash Flow Information	The components of lease expense were as follows (in millions): Three Months Ended March 31, March 31, Operating lease expense $ 5.9 $ 4.3 Variable lease expense (1) 0.8 0.6 Short-term lease expense 0.8 0.9 Total lease expense $ 7.5 $ 5.8 (1) Variable lease expense for the three months ended March 31, 2021 and 2020 predominantly included common area maintenance charges and parking expense. Supplemental cash flow information related to leases was as follows (in millions): 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 $ 6.1 $ 4.6
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 $ 53.9 $ 49.3 Operating lease liabilities - current Accrued liabilities $ 20.6 $ 19.1 Operating lease liabilities - non-current Other liabilities 35.8 34.0 Total operating lease liabilities $ 56.4 $ 53.1 Weighted average remaining lease term in years - operating leases 3.4 3.5 Weighted average discount rate - operating leases 2.8 % 3.2 %
Maturities of Operating Lease Liabilities	Maturities of operating lease liabilities as of March 31, 2021 were as follows (in millions): Year Ending December 31, Amount 2021 (the remainder of 2021) $ 16.5 2022 17.8 2023 12.0 2024 7.5 2025 3.9 Thereafter 1.4 Total lease payments 59.1 Less imputed interest (2.7) Total $ 56.4

Debt (Tables)

Debt (Tables)	3 Months Ended
	Mar. 31, 2021
Debt Disclosure [Abstract]
Summary of Outstanding Debt	The total outstanding debt is summarized below (in millions, except percentages): Maturity Coupon Rate Effective Interest Rate March 31, 2021 Debt 2026 Senior Notes March 2026 1.0 % 1.3 % $ 500.0 2031 Senior Notes March 2031 2.2 % 2.3 % 500.0 Total debt 1,000.0 Less: Unamortized discount and debt issuance costs (13.0) Total long-term debt $ 987.0

Commitments and Contingencies (

Commitments and Contingencies (Tables)	3 Months Ended
	Mar. 31, 2021
Commitments and Contingencies Disclosure [Abstract]
Inventory Purchase Commitments, Fiscal Year Maturity Schedule	The following table summarizes our inventory purchase commitments as of March 31, 2021 (in millions): Total 2021 2022 2023 2024 2025 Thereafter Inventory purchase commitments $ 298.8 $ 298.7 $ 0.1 $ — $ — $ — $ —

Stockholders' Equity (Tables)

Stockholders' Equity (Tables)	3 Months Ended
	Mar. 31, 2021
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 RSUs 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, 2020 4.7 $ 90.46 Granted 0.8 172.74 Forfeited (0.1) 100.57 Vested (0.8) 79.95 Balance—March 31, 2021 4.6 $ 107.37
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 0.3 Amount withheld for taxes $ 41.4 $ 37.8
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 39.5 % 33.5 % Risk-free interest rate 0.5 % 1.3 % 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 Weighted- Weighted- Aggregate Balance—December 31, 2020 2.7 $ 67.53 4.2 220.4 Granted 0.5 171.93 Forfeited — 109.16 Exercised (0.2) 50.36 Balance—March 31, 2021 3.0 $ 85.66 Options vested and expected to vest—March 31, 2021 3.0 $ 85.66 4.5 $ 297.1 Options exercisable—March 31, 2021 1.5 $ 51.63 3.3 $ 205.8
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 $ 56.49 $ 33.82 Intrinsic value of options exercised $ 22.3 $ 13.1 Fair value of options vested $ 7.0 $ 6.0
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 3.5 3.0 Research and development 13.0 10.9 Sales and marketing 26.8 25.7 General and administrative 6.3 5.3 Total stock-based compensation expense $ 50.0 $ 45.3
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 $ 45.8 $ 42.2 Stock options 4.2 3.1 Total stock-based compensation expense $ 50.0 $ 45.3
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 $ 11.0 $ 10.0

Segment Information (Tables)

Segment Information (Tables)	3 Months Ended
	Mar. 31, 2021
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 $ 212.5 $ 181.9 Other Americas 78.4 60.7 Total Americas 290.9 242.6 Europe, Middle East and Africa (“EMEA”) 275.7 221.0 Asia Pacific (“APAC”) 143.7 114.1 Total revenue $ 710.3 $ 577.7
Property and Equipment by Geographic Region	Property and Equipment — net March 31, December 31, Americas: United States $ 342.7 $ 296.3 Canada 120.2 121.3 Latin America 2.1 2.0 Total Americas 465.0 419.6 EMEA 22.3 20.6 APAC 6.9 7.8 Total property and equipment—net $ 494.2 $ 448.0
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 (“Exclusive”) 32 % 31 % Ingram Micro, Inc. (“Ingram Micro”) 11 % 10 % The following distributors accounted for 10% or more of net accounts receivable: March 31, December 31, Exclusive 31 % 34 % Ingram Micro 16 % 11 %

Immaterial Correction of Prio_3

Immaterial Correction of Prior Period Financial Statements - Income Statement (Details) - USD ($) $ / shares in Units, $ in Millions	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020
REVENUE:
Total revenue	$ 710.3	$ 577.7
GROSS PROFIT:
Gross Profit	553.7	449
OPERATING INCOME	121.6	116.7
INCOME BEFORE INCOME TAXES	119.4	117.9
PROVISION FOR INCOME TAXES	12.2	13.3
NET INCOME	$ 107.2	$ 104.6
Net income per share (Note 10):
Basic (in dollars per share)	$ 0.66	$ 0.61
Diluted (in dollars per share)	$ 0.64	$ 0.60
As Previously Reported [Member]
REVENUE:
Total revenue		$ 576.9
GROSS PROFIT:
Gross Profit		448.2
OPERATING INCOME		115.9
INCOME BEFORE INCOME TAXES		117.1
PROVISION FOR INCOME TAXES		13.1
NET INCOME		$ 104
Net income per share (Note 10):
Basic (in dollars per share)		$ 610,000
Diluted (in dollars per share)		$ 600,000
Corrections [Member]
REVENUE:
Total revenue		$ 0.8
GROSS PROFIT:
Gross Profit		0.8
OPERATING INCOME		0.8
INCOME BEFORE INCOME TAXES		0.8
PROVISION FOR INCOME TAXES		0.2
NET INCOME		$ 0.6
Net income per share (Note 10):
Basic (in dollars per share)		$ 0
Diluted (in dollars per share)		$ 0
Service [Member]
REVENUE:
Total revenue	$ 469.6	$ 385.4
GROSS PROFIT:
Gross Profit	$ 404.3	333
Service [Member] | As Previously Reported [Member]
REVENUE:
Total revenue		384.6
GROSS PROFIT:
Gross Profit		332.2
Service [Member] | Corrections [Member]
REVENUE:
Total revenue		0.8
GROSS PROFIT:
Gross Profit		$ 0.8

Immaterial Correction of Prio_4

Immaterial Correction of Prior Period Financial Statements - Cash Flows (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020
CASH FLOWS FROM OPERATING ACTIVITIES:
Net income	$ 107.2	$ 104.6
Changes in operating assets and liabilities:
Deferred tax assets	(15.2)	7.3
Deferred revenue	$ 140.3	90.1
As Previously Reported [Member]
CASH FLOWS FROM OPERATING ACTIVITIES:
Net income		104
Changes in operating assets and liabilities:
Deferred tax assets		7.1
Deferred revenue		90.9
Corrections [Member]
CASH FLOWS FROM OPERATING ACTIVITIES:
Net income		0.6
Changes in operating assets and liabilities:
Deferred tax assets		0.2
Deferred revenue		$ (0.8)

Revenue Recognition - Disaggreg

Revenue Recognition - Disaggregated Revenues (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020
Disaggregation of Revenue [Line Items]
Total revenue	$ 710.3	$ 577.7
Product [Member]
Disaggregation of Revenue [Line Items]
Total revenue	240.7	192.3
Service [Member]
Disaggregation of Revenue [Line Items]
Total revenue	469.6	385.4
Security Subscription [Member]
Disaggregation of Revenue [Line Items]
Total revenue	255.3	211.4
Technical Support and Other [Member]
Disaggregation of Revenue [Line Items]
Total revenue	$ 214.3	$ 174

Revenue Recognition (Details)

Revenue Recognition (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020	Dec. 31, 2020
Disaggregation of Revenue [Line Items]
Remaining performance obligation	$ 2,750
Threshold period past due	60 days
Allowance for credit losses	$ 3.1		$ 2.5
Amortization of deferred contract costs	39.7	$ 31.3
Service [Member]
Disaggregation of Revenue [Line Items]
Deferred revenue recognized in period	$ 417.9	$ 343.3

Revenue Recognition - Performan

Revenue Recognition - Performance Obligation Satisfaction Period (Details) $ in Millions	Mar. 31, 2021USD ($)
Revenue from Contract with Customer [Abstract]
Remaining performance obligation	$ 2,750
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2021-04-01
Revenue from Contract with Customer [Abstract]
Remaining performance obligation	$ 1,470
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]: 2022-04-01
Revenue from Contract with Customer [Abstract]
Remaining performance obligation	$ 1,280
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, 2021	Dec. 31, 2020
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	$ 1,227.4	$ 892.8
Unrealized Gains	0.6	1
Unrealized Losses	(0.2)	0
Fair Value	1,227.8	893.8
Available-for-sale Securities, Continuous Unrealized Loss Position [Abstract]
Less Than 12 Months, Fair Value	465.8	240.4
Less Than 12 Months, Unrealized Losses	(0.2)	0
12 Months or Greater, Fair Value	5.5	0
12 Months or Greater, Unrealized Losses	0	0
Total, Fair Value	471.3	240.4
Total, Unrealized Losses	(0.2)	0
Available-for-sale Securities, Debt Maturities, Fair Value [Abstract]
Due within one year	1,076.7	775.5
Due within one to three years	151.1	118.3
Fair Value	1,227.8	893.8
Corporate debt securities [Member]
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	482.1	410.5
Unrealized Gains	0.5	1
Unrealized Losses	(0.2)	0
Fair Value	482.4	411.5
Available-for-sale Securities, Continuous Unrealized Loss Position [Abstract]
Less Than 12 Months, Fair Value	272.2	111.3
Less Than 12 Months, Unrealized Losses	(0.2)	0
12 Months or Greater, Fair Value	0	0
12 Months or Greater, Unrealized Losses	0	0
Total, Fair Value	272.2	111.3
Total, Unrealized Losses	(0.2)	0
Available-for-sale Securities, Debt Maturities, Fair Value [Abstract]
Fair Value	482.4	411.5
Commercial paper [Member]
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	426.4	185.4
Unrealized Gains	0.1	0
Unrealized Losses	0	0
Fair Value	426.5	185.4
Available-for-sale Securities, Continuous Unrealized Loss Position [Abstract]
Less Than 12 Months, Fair Value	164.1	61.5
Less Than 12 Months, Unrealized Losses	0	0
12 Months or Greater, Fair Value	0	0
12 Months or Greater, Unrealized Losses	0	0
Total, Fair Value	164.1	61.5
Total, Unrealized Losses	0	0
Available-for-sale Securities, Debt Maturities, Fair Value [Abstract]
Fair Value	426.5	185.4
Certificates of deposit and term deposits [Member]
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	162.7	112
Unrealized Gains	0	0
Unrealized Losses	0	0
Fair Value	162.7	112
Available-for-sale Securities, Continuous Unrealized Loss Position [Abstract]
Less Than 12 Months, Fair Value	29.5	29.5
Less Than 12 Months, Unrealized Losses	0	0
12 Months or Greater, Fair Value	5.5	0
12 Months or Greater, Unrealized Losses	0	0
Total, Fair Value	35	29.5
Total, Unrealized Losses	0	0
Available-for-sale Securities, Debt Maturities, Fair Value [Abstract]
Fair Value	162.7	112
U.S. government securities [Member]
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	156.2	184.9
Unrealized Gains	0	0
Unrealized Losses	0	0
Fair Value	156.2	184.9
Available-for-sale Securities, Continuous Unrealized Loss Position [Abstract]
Less Than 12 Months, Fair Value		38.1
Less Than 12 Months, Unrealized Losses		0
12 Months or Greater, Fair Value		0
12 Months or Greater, Unrealized Losses		0
Total, Fair Value		38.1
Total, Unrealized Losses		0
Available-for-sale Securities, Debt Maturities, Fair Value [Abstract]
Fair Value	$ 156.2	$ 184.9

Financial Instruments and Fai_4

Financial Instruments and Fair Value , Additional Information (Details) $ in Millions	Mar. 31, 2021USD ($)
Financial Instruments and Fair Value [Abstract]
Accrued interest on available-for-sale securities	$ 2.6

Financial Instruments and Fai_5

Financial Instruments and Fair Value , Fair Value Measurements (Details) - USD ($) $ in Millions	Mar. 31, 2021	Dec. 31, 2020
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value	$ 1,227.8	$ 893.8
Corporate debt securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value	482.4	411.5
Commercial paper [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value	426.5	185.4
U.S. government securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value	156.2	184.9
Certificates of deposit and term deposits [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value	162.7	112
Recurring Basis [Member] | Fair Value [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total Assets, Fair Value Disclosure	1,561	1,060.5
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	439	337.6
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	1,122	722.9
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	489.6	413.7
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
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	489.6	413.7
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	463.2	197.2
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	463.2	197.2
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] | U.S. government securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value	156.2	184.9
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	156.2	184.9
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] | Certificates of deposit and term deposits [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value	169.2	112
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	169.2	112
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] | Money market funds [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value	282.8	152.7
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	282.8	152.7
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	1,561	1,060.5
Recurring Basis [Member] | Reported as [Member] | Cash equivalents [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value	333.2	166.7
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	1,076.7	775.5
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	$ 151.1	$ 118.3

Inventory (Details)

Inventory (Details) - USD ($) $ in Millions	Mar. 31, 2021	Dec. 31, 2020
Inventory, Net [Abstract]
Raw materials	$ 15.2	$ 13.8
Finished goods	134.4	126
Inventory	$ 149.6	$ 139.8

Property and Equipment_Net (Det

Property and Equipment—Net (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020	Dec. 31, 2020
Property, Plant and Equipment, Net, by Type [Abstract]
Total property and equipment	$ 674.8		$ 620.5
Less: accumulated depreciation	(180.6)		(172.5)
Property and equipment—net	494.2		448
Depreciation expense	14	$ 13.6
Land [Member]
Property, Plant and Equipment, Net, by Type [Abstract]
Total property and equipment	106.8		93.3
Building and building improvements [Member]
Property, Plant and Equipment, Net, by Type [Abstract]
Total property and equipment	153.8		150.6
Computer equipment and software [Member]
Property, Plant and Equipment, Net, by Type [Abstract]
Total property and equipment	146.4		137.2
Leasehold improvements [Member]
Property, Plant and Equipment, Net, by Type [Abstract]
Total property and equipment	33.6		31.9
Evaluation units [Member]
Property, Plant and Equipment, Net, by Type [Abstract]
Total property and equipment	18.7		19.8
Furniture and fixtures [Member]
Property, Plant and Equipment, Net, by Type [Abstract]
Total property and equipment	22.1		21.3
Construction-in-progress [Member]
Property, Plant and Equipment, Net, by Type [Abstract]
Total property and equipment	$ 193.4		$ 166.4

Investments in Privately-Held_2

Investments in Privately-Held Companies (Details) - USD ($) $ in Millions	Mar. 19, 2021	Mar. 31, 2021	Mar. 31, 2020	Dec. 31, 2020
Schedule of Equity Method Investments [Line Items]
Cash investment in privately held company		$ 75	$ 0
Investments in equity securities of privately-held companies		$ 1		$ 1
Linksys
Schedule of Equity Method Investments [Line Items]
Cash investment in privately held company	$ 75
Ownership interest percentage	32.60%

Business Combinations - Additio

Business Combinations - Additional Information (Details) - USD ($) $ in Millions	Mar. 10, 2021	Mar. 31, 2021	Dec. 31, 2020
Business Acquisition [Line Items]
Goodwill		$ 99.2	$ 93
ShieldX Networks Inc (ShieldX) [Member]
Business Acquisition [Line Items]
Cash consideration	$ 10.8
Goodwill	6.2
Other net assets acquired	0.5
ShieldX Networks Inc (ShieldX) [Member] | Developed Technologies [Member]
Business Acquisition [Line Items]
Identifiable intangible assets	$ 4.1

Goodwill and Other Intangible_3

Goodwill and Other Intangible Assets - Net - Changes in Carrying Amount of Goodwill (Details) $ in Millions	3 Months Ended
	Mar. 31, 2021USD ($)
Goodwill [Roll Forward]
Balance - beginning of period	$ 93
Addition due to business combination	6.2
Balance - end of period	$ 99.2

Goodwill and Other Intangible_4

Goodwill and Other Intangible Assets - Net - Narrative (Details) - USD ($)	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020
Goodwill and Intangible Assets Disclosure [Abstract]
Goodwill impairment	$ 0	$ 0
Amortization expense	$ 3,400,000	$ 4,000,000

Goodwill and Other Intangible_5

Goodwill and Other Intangible Assets - Net - Other Intangible Assets, Net (Details) - USD ($) $ in Millions	3 Months Ended	12 Months Ended
	Mar. 31, 2021	Dec. 31, 2020
Finite-Lived Intangible Assets, Net [Abstract]
Gross	$ 88.2	$ 84.1
Accumulated Amortization	55.9	52.5
Total	$ 32.3	$ 31.6
Developed Technologies [Member]
Finite-Lived Intangible Assets [Line Items]
Weighted average useful life	4 years	4 years
Finite-Lived Intangible Assets, Net [Abstract]
Gross	$ 63.4	$ 59.3
Accumulated Amortization	34.8	32.3
Total	$ 28.6	$ 27
Customer Relationships [Member]
Finite-Lived Intangible Assets [Line Items]
Weighted average useful life	4 years	4 years
Finite-Lived Intangible Assets, Net [Abstract]
Gross	$ 24.8	$ 24.8
Accumulated Amortization	21.1	20.2
Total	$ 3.7	$ 4.6

Goodwill and Other Intangible_6

Goodwill and Other Intangible Assets - Net - Estimated Future Amortization Expense (Details) - USD ($) $ in Millions	Mar. 31, 2021	Dec. 31, 2020
Fiscal Years:
2021 (the remainder of 2021)	$ 10.5
2022	10.7
2023	7.6
2024	3.2
2025	0.3
Total	$ 32.3	$ 31.6

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, 2021	Mar. 31, 2020
Earnings Per Share [Line Items]
Net income	$ 107.2	$ 104.6
Basic shares:
Weighted-average common shares outstanding-basic (in shares)	163	170.6
Diluted shares:
Weighted-average common shares outstanding-basic (in shares)	163	170.6
Effect of potentially dilutive securities:
Weighted-average shares used to compute diluted net income per share (in shares)	166.4	174.2
Net income per share:
Basic (in dollars per share)	$ 0.66	$ 0.61
Diluted (in dollars per share)	$ 0.64	$ 0.60
Restricted Stock Units (RSUs) [Member]
Effect of potentially dilutive securities:
RSUs and stock options (in shares)	2	2.4
Stock Options [Member]
Effect of potentially dilutive securities:
RSUs and stock options (in shares)	1.4	1.2

Net Income Per Share , Anti Dil

Net Income Per Share , Anti Dilutive Securities (Details) - shares shares in Millions	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Anti-dilutive securities (in shares)	0.7	0.9
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)	0.4	0.6
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, 2021	Dec. 31, 2019
Lessee, Lease, Description [Line Items]
Renewal terms (up to)	6 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	$ 2.7
Minimum [Member]
Lessee, Lease, Description [Line Items]
Remaining terms (less than for minimum)	1 year
Maximum [Member]
Lessee, Lease, Description [Line Items]
Remaining terms (less than for minimum)	7 years
Lease not yet commenced, approximate term	3 years

Leases - Components of Lease Ex

Leases - Components of Lease Expense (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020
Leases [Abstract]
Operating lease expense	$ 5.9	$ 4.3
Variable lease expense	0.8	0.6
Short-term lease expense	0.8	0.9
Total lease expense	$ 7.5	$ 5.8

Leases - Supplemental Balance S

Leases - Supplemental Balance Sheet Information (Details) - USD ($) $ in Millions	Mar. 31, 2021	Dec. 31, 2020
Leases [Abstract]
Operating Lease, Right-of-Use Asset, Statement of Financial Position [Extensible List]	us-gaap:OtherAssets	us-gaap:OtherAssets
Operating lease ROU assets - non-current	$ 53.9	$ 49.3
Operating Lease, Liability, Current, Statement of Financial Position [Extensible List]	us-gaap:AccountsPayableAndAccruedLiabilitiesCurrent	us-gaap:AccountsPayableAndAccruedLiabilitiesCurrent
Operating lease liabilities - current	$ 20.6	$ 19.1
Operating Lease, Liability, Noncurrent, Statement of Financial Position [Extensible List]	OTHER LIABILITIES	OTHER LIABILITIES
Operating lease liabilities - non-current	$ 35.8	$ 34
Total operating lease liabilities	$ 56.4	$ 53.1
Weighted average remaining lease term in years - operating leases	3 years 4 months 24 days	3 years 6 months
Weighted average discount rate - operating leases	2.80%	3.20%

Leases - Supplemental Cash Flow

Leases - Supplemental Cash Flow Information (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020
Cash paid for amounts included in the measurement of lease liabilities
Operating cash flows used for operating leases	$ 6.1	$ 4.6

Leases - Maturities of Operatin

Leases - Maturities of Operating Lease Liabilities (Details) - USD ($) $ in Millions	Mar. 31, 2021	Dec. 31, 2020
Leases [Abstract]
2021 (the remainder of 2021)	$ 16.5
2022	17.8
2023	12
2024	7.5
2025	3.9
Thereafter	1.4
Total lease payments	59.1
Less imputed interest	(2.7)
Total	$ 56.4	$ 53.1

Debt - Narrative (Details)

Debt - Narrative (Details) - Senior Notes [Member] - USD ($)	3 Months Ended
	Mar. 31, 2021	Mar. 05, 2021
Debt Instrument [Line Items]
Aggregate principal amount		$ 1,000,000,000
Accrued interest payable	$ 1,200,000
Interest expense	1,300,000
Level 2 [Member]
Debt Instrument [Line Items]
Estimated fair value of outstanding debt	$ 975,600,000
2026 Senior Notes [Member]
Debt Instrument [Line Items]
Aggregate principal amount		$ 500,000,000
Stated interest rate	1.00%	1.00%
2031 Senior Notes [Member]
Debt Instrument [Line Items]
Aggregate principal amount		$ 500,000,000
Stated interest rate	2.20%	2.20%

Debt - Summary of Outstanding D

Debt - Summary of Outstanding Debt (Details) - USD ($) $ in Millions	Mar. 31, 2021	Mar. 05, 2021
Debt Instrument [Line Items]
Total debt	$ 1,000
Less: Unamortized discount and debt issuance costs	(13)
Total long-term debt	$ 987
Senior Notes [Member] | 2026 Senior Notes [Member]
Debt Instrument [Line Items]
Coupon Rate	1.00%	1.00%
Effective Interest Rate	1.30%
Total debt	$ 500
Senior Notes [Member] | 2031 Senior Notes [Member]
Debt Instrument [Line Items]
Coupon Rate	2.20%	2.20%
Effective Interest Rate	2.30%
Total debt	$ 500

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, 2021	Mar. 31, 2020
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
Amount representing the right to utilize future patents	$ 64,000,000
Gain on IP matter		$ 1,100,000	$ 36,800,000
Amount recorded in Accrued liabilities and Other liabilities in condensed consolidated balance sheet		$ 8,700,000

Commitments and Contingencies -

Commitments and Contingencies - Inventory Purchase Commitments (Details) $ in Millions	Mar. 31, 2021USD ($)
Inventory purchase commitments:
Inventory purchase commitments	$ 298.8
Inventory purchase commitments, 2021	298.7
Inventory purchase commitments, 2022	0.1
Inventory purchase commitments, 2023	0
Inventory purchase commitments, 2024	0
Inventory purchase commitments, 2025	0
Inventory purchase commitments, Thereafter	$ 0

Commitments and Contingencies_2

Commitments and Contingencies (Details) $ in Millions	Mar. 31, 2021USD ($)
Commitments and Contingencies Disclosure [Abstract]
Inventory purchase commitments	$ 298.8
Other contractual commitments and open purchase orders	$ 65.1

Stockholders' Equity , Restrict

Stockholders' Equity , Restricted Stock Units Activity (Details) - USD ($) $ / shares in Units, shares in Millions, $ in Millions	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020
Weighted-Average Grant Date Fair Value per Share
Shares withheld for taxes	0.3	0.3
Amount withheld for taxes	$ 41.4	$ 37.8
Stock-based Compensation Plan [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Remaining shares available for grant under the plans	11.4
Restricted Stock Units (RSUs) [Member]
Number of Shares
Balance, beginning (shares)	4.7
Granted (shares)	0.8
Forfeited (shares)	(0.1)
Vested (shares)	(0.8)
Balance, ending (shares)	4.6
Weighted-Average Grant Date Fair Value per Share
Balance, beginning (in dollars per share)	$ 90.46
Granted (in dollars per share)	172.74
Forfeited (in dollars per share)	100.57
Vested (in dollars per share)	79.95
Balance, ending (in dollars per share)	$ 107.37
Compensation cost not yet recognized	$ 450.7
Compensation cost not yet recognized period of recognition	2 years 10 months 24 days

Stockholders' Equity - Employee

Stockholders' Equity - Employee Stock Options (Details) - Stock Options [Member] - USD ($) $ / shares in Units, shares in Millions, $ in Millions	3 Months Ended		12 Months Ended
	Mar. 31, 2021	Mar. 31, 2020	Dec. 31, 2020
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	39.50%	33.50%
Risk-free interest rate	0.50%	1.30%
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		2.7
Weighted- Average Exercise Price
Balance - Beginning (in dollars per share)	$ 67.53
Granted (in dollars per share)	171.93
Forfeited (in dollars per share)	109.16
Exercised (in dollars per share)	50.36
Balance - Ending (in dollars per share)	$ 85.66		$ 67.53
Share-based Compensation Arrangement by Share-based Payment Award, Options, Additional Disclosures [Abstract]
Options outstanding, Weighted average remaining contractual life (in years)			4 years 2 months 12 days
Options outstanding, Aggregate intrinsic value			$ 220.4
Options vested and expected to vest, Outstanding (in shares)	3
Options vested and expected to vest, Weighted average exercise price (in dollars per share)	$ 85.66
Options vested and expected to vest, Weighted average remaining contractual life (in years)	4 years 6 months
Options vested and expected to vest, Aggregate intrinsic value	$ 297.1
Options exercisable, Outstanding (in shares)	1.5
Options exercisable, Weighted average exercise price (in dollars per share)	$ 51.63
Options exercisable, Weighted average remaining contractual life (in years)	3 years 3 months 18 days
Options exercisable, Aggregate intrinsic value	$ 205.8
Compensation cost not yet recognized	$ 54.6
Compensation cost not yet recognized period of recognition	3 years 2 months 12 days
Weighted-average fair value per share granted	$ 56.49	$ 33.82
Intrinsic value of options exercised	$ 22.3	$ 13.1
Fair value of options vested	$ 7	$ 6

Stockholders' Equity , Allocati

Stockholders' Equity , Allocation of Stock-Based Compensation Expense (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]
Total stock-based compensation expense	$ 50	$ 45.3
Income tax benefit associated with stock-based compensation	11	10
Restricted Stock Units (RSUs) [Member]
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]
Total stock-based compensation expense	45.8	42.2
Stock Options [Member]
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]
Total stock-based compensation expense	4.2	3.1
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	3.5	3
Research and development [Member]
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]
Total stock-based compensation expense	13	10.9
Sales and marketing [Member]
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]
Total stock-based compensation expense	26.8	25.7
General and administrative [Member]
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]
Total stock-based compensation expense	$ 6.3	$ 5.3

Stockholders' Equity , Share Re

Stockholders' Equity , Share Repurchase Program (Details) - Repurchase Program [Member] - USD ($)	1 Months Ended	3 Months Ended
	Jul. 31, 2020	Mar. 31, 2021
Share Repurchase Program [Line Items]
Increase in authorized stock repurchase amount	$ 500,000,000
Stock repurchase program, authorized amount	$ 3,000,000,000
Stock repurchased in the period (in shares)		0
Stock repurchase program, unused balance		$ 1,010,000,000

Income Taxes , Narrative (Detai

Income Taxes , Narrative (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020	Dec. 31, 2020
Income Tax Disclosure [Abstract]
Effective tax rate (percent)	10.00%	11.00%
U.S. federal and state taxes, withholding taxes and foreign taxes	$ 35.7	$ 33.3
Tax benefit from foreign-derived intangible income deduction	7.3	4.8
Excess tax benefits on stock compensation	16.2	$ 15.2
Unrecognized tax benefits	81.6		$ 77.3
Unrecognized tax benefits that would favorably affect effective tax rate	74.6
Accrued interest and penalties related to uncertain tax benefits	16		$ 14.5
Possible decrease in unrecognized tax benefits (up to)	$ 4.4

Defined Contribution Plans (Det

Defined Contribution Plans (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020
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	$ 2.7	$ 2.2

Segment Information (Details)

Segment Information (Details) $ in Millions	3 Months Ended		12 Months Ended
	Mar. 31, 2021USD ($)business_activityoperating_segmentsegment_manager1reportable_segment	Mar. 31, 2020USD ($)	Dec. 31, 2020USD ($)
Segment Reporting Information [Line Items]
Business activity (in business activities) | business_activity	1
Segment managers responsible for operations (in segment managers) | segment_manager1	0
Number of operating segments (in operating segments) | operating_segment	1
Number of reportable segments (in reportable segments) | reportable_segment	1
Total revenue	$ 710.3	$ 577.7
Property and equipment - net	$ 494.2		$ 448
Exclusive Networks Group (Exclusive) [Member] | Customer Concentration Risk [Member] | Revenue [Member]
Segment Reporting Information [Line Items]
Concentration (percent)	32.00%	31.00%
Exclusive Networks Group (Exclusive) [Member] | Customer Concentration Risk [Member] | Accounts Receivable [Member]
Segment Reporting Information [Line Items]
Concentration (percent)	31.00%		34.00%
Ingram Micro, Inc. (Ingram Micro) [Member] | Customer Concentration Risk [Member] | Revenue [Member]
Segment Reporting Information [Line Items]
Concentration (percent)	11.00%	10.00%
Ingram Micro, Inc. (Ingram Micro) [Member] | Customer Concentration Risk [Member] | Accounts Receivable [Member]
Segment Reporting Information [Line Items]
Concentration (percent)	16.00%		11.00%
Americas [Member]
Segment Reporting Information [Line Items]
Total revenue	$ 290.9	$ 242.6
Property and equipment - net	465		$ 419.6
U.S. [Member]
Segment Reporting Information [Line Items]
Total revenue	212.5	181.9
Property and equipment - net	342.7		296.3
Canada [Member]
Segment Reporting Information [Line Items]
Property and equipment - net	120.2		121.3
Latin America [Member]
Segment Reporting Information [Line Items]
Property and equipment - net	2.1		2
Other Americas [Member]
Segment Reporting Information [Line Items]
Total revenue	78.4	60.7
EMEA [Member]
Segment Reporting Information [Line Items]
Total revenue	275.7	221
Property and equipment - net	22.3		20.6
APAC [Member]
Segment Reporting Information [Line Items]
Total revenue	143.7	$ 114.1
Property and equipment - net	$ 6.9		$ 7.8