Fortinet (FTNT) 10-Q 8 Nov 21 2021 Q3 Quarterly report Financial data

Document and Entity Information

Document and Entity Information - shares	9 Months Ended
	Sep. 30, 2021	Nov. 05, 2021
Cover [Abstract]
Document Type	10-Q
Document Quarterly Report	true
Document Period End Date	Sep. 30, 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		163,499,790
Entity Central Index Key	0001262039
Amendment Flag	false
Document Fiscal Year Focus	2021
Document Fiscal Period Focus	Q3
Current Fiscal Year End Date	--12-31

Condensed Consolidated Balance

Condensed Consolidated Balance Sheets - USD ($) $ in Millions	Sep. 30, 2021	Dec. 31, 2020
CURRENT ASSETS:
Cash and cash equivalents	$ 1,852.1	$ 1,061.8
Short-term investments	1,228.1	775.5
Marketable equity securities	40.8	0
Accounts receivable—net	604.9	720
Inventory	177.9	139.8
Prepaid expenses and other current assets	59.7	43.3
Total current assets	3,963.5	2,740.4
LONG-TERM INVESTMENTS	298.2	118.3
PROPERTY AND EQUIPMENT—NET	556.6	448
DEFERRED CONTRACT COSTS	378.8	304.8
DEFERRED TAX ASSETS	337.3	245.2
GOODWILL	127.6	93
OTHER INTANGIBLE ASSETS—NET	71	31.6
OTHER ASSETS	237.6	63.2
TOTAL ASSETS	5,970.6	4,044.5
CURRENT LIABILITIES:
Accounts payable	142.3	141.6
Accrued liabilities	247.8	149.2
Accrued payroll and compensation	174.2	145.9
Current portion of long-term debt	17.6	0
Deferred revenue	1,616.1	1,392.8
Total current liabilities	2,198	1,829.5
DEFERRED REVENUE	1,490.3	1,212.5
INCOME TAX LIABILITIES	96.5	90.3
LONG-TERM DEBT	988	0
OTHER LIABILITIES	62.2	56.2
Total liabilities	4,835	3,188.5
COMMITMENTS AND CONTINGENCIES (Note 13)
EQUITY:
Common stock, $0.001 par value—300.0 shares authorized; 163.4 and 162.5 shares issued and outstanding at September 30, 2021 and December 31, 2020, respectively	0.2	0.2
Additional paid-in capital	1,257.7	1,207.2
Accumulated other comprehensive income (loss)	(1.2)	0.7
Accumulated deficit	(138.6)	(352.1)
Total Fortinet, Inc. stockholders’ equity	1,118.1	856
Non-controlling interests	17.5	0
Total equity	1,135.6	856
TOTAL LIABILITIES AND EQUITY	$ 5,970.6	$ 4,044.5

Condensed Consolidated Balanc_2

Condensed Consolidated Balance Sheets Parenthetical - $ / shares	Sep. 30, 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	163,400,000	162,500,000
Common Stock, shares outstanding	163,400,000	162,500,000

Condensed Consolidated Statemen

Condensed Consolidated Statements of Income - USD ($) shares in Millions, $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
REVENUE:
Total revenue	$ 867.2	$ 651.1	$ 2,378.6	$ 1,846.4
COST OF REVENUE:
Total cost of revenue	211.2	139.2	554.7	403
GROSS PROFIT:
Total gross profit	656	511.9	1,823.9	1,443.4
OPERATING EXPENSES:
Research and development	107.8	90	311.6	252.4
Sales and marketing	347.1	266.7	978	780.5
General and administrative	35.8	29.4	102.2	87.1
Gain on intellectual property matter	(1.1)	(1.1)	(3.4)	(39)
Total operating expenses	489.6	385	1,388.4	1,081
OPERATING INCOME	166.4	126.9	435.5	362.4
INTEREST INCOME	1.2	2.5	3.5	15.7
INTEREST EXPENSE	(4.6)	0	(10.4)	0
OTHER EXPENSE—NET	(6.3)	(1)	(7.5)	(8.1)
INCOME BEFORE INCOME TAXES AND LOSS FROM EQUITY METHOD INVESTMENT	156.7	128.4	421.1	370
PROVISION FOR (BENEFIT FROM) INCOME TAXES	(9.3)	5	10.4	28.2
LOSS FROM EQUITY METHOD INVESTMENT	(2.8)	0	(2.8)	0
NET INCOME INCLUDING NON-CONTROLLING INTERESTS	163.2	123.4	407.9	341.8
LESS: NET INCOME ATTRIBUTABLE TO NON-CONTROLLING INTERESTS, NET OF TAX	0.1	0	0.1	0
NET INCOME ATTRIBUTABLE TO FORTINET, INC.	$ 163.1	$ 123.4	$ 407.8	$ 341.8
Net income per share attributable to Fortinet, Inc. common stockholders (Note 9):
Basic (in dollars per share)	$ 1	$ 0.76	$ 2.50	$ 2.07
Diluted (in dollars per share)	$ 0.97	$ 0.75	$ 2.44	$ 2.03
Weighted-average shares used to compute net income per share attributable to Fortinet, Inc. common stockholders
Basic (in shares)	163.5	162.1	163.3	164.8
Diluted (in shares)	167.7	165.6	167.1	168.4
Product [Member]
REVENUE:
Total revenue	$ 337.1	$ 223.8	$ 876.1	$ 628
COST OF REVENUE:
Total cost of revenue	134.3	84.3	341.2	245
GROSS PROFIT:
Total gross profit	202.8	139.5	534.9	383
Service [Member]
REVENUE:
Total revenue	530.1	427.3	1,502.5	1,218.4
COST OF REVENUE:
Total cost of revenue	76.9	54.9	213.5	158
GROSS PROFIT:
Total gross profit	$ 453.2	$ 372.4	$ 1,289	$ 1,060.4

Condensed Consolidated Statem_2

Condensed Consolidated Statements of Comprehensive Income - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
Statement of Comprehensive Income [Abstract]
Net income including non-controlling interests	$ 163.2	$ 123.4	$ 407.9	$ 341.8
Other comprehensive income (loss):
Change in foreign currency translation	(1.6)	0	(1.6)	0
Change in unrealized gains (losses) on investments	0	(1.4)	(1)	0.7
Less: tax provision (benefit) related to items of other comprehensive income or loss	(0.1)	(0.3)	(0.3)	0.4
Other comprehensive income (loss)	(1.5)	(1.1)	(2.3)	0.3
Comprehensive income including non-controlling interests	161.7	122.3	405.6	342.1
Less: comprehensive loss attributable to non-controlling interests	(0.3)	0	(0.3)	0
Comprehensive income attributable to Fortinet, Inc.	$ 162	$ 122.3	$ 405.9	$ 342.1

Condensed Consolidated Statem_3

Condensed Consolidated Statements of Stockholders' Equity - USD ($) shares in Millions, $ in Millions	Total	Common Stock	Additional Paid-In Capital	Accumulated Other Comprehensive Income (Loss)	Accumulated Deficit	Non-Controlling Interests
Balance, shares at Dec. 31, 2019		171.7
Balance, beginning of period 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)		2
Issuance of common stock in connection with equity incentive plans - net of tax withholding	(68.3)		(68.3)
Repurchase and retirement of common stock (in shares)		(11.4)
Repurchase and retirement of common stock	(1,046)		(76.5)		(969.5)
Stock-based compensation expense	143		143
Net unrealized gain on investments - net of tax	0.3			0.3
Net income including non-controlling interests	341.8
Balance, shares at Sep. 30, 2020		162.3
Balance, end of period at Sep. 30, 2020	713.2	$ 0.2	1,178.5	1.4	(466.9)	$ 0
Balance, shares at Jun. 30, 2020		161.8
Balance, beginning of period at Jun. 30, 2020	566.7	$ 0.2	1,154.3	2.5	(590.3)	0
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Issuance of common stock in connection with equity incentive plans - net of tax withholding (in shares)		0.5
Issuance of common stock in connection with equity incentive plans - net of tax withholding	(25.1)		(25.1)
Stock-based compensation expense	49.3		49.3
Net unrealized gain on investments - net of tax	(1.1)			(1.1)
Net income including non-controlling interests	123.4				123.4
Balance, shares at Sep. 30, 2020		162.3
Balance, end of period at Sep. 30, 2020	713.2	$ 0.2	1,178.5	1.4	(466.9)	0
Balance, shares at Dec. 31, 2020		162.5
Balance, beginning of period at Dec. 31, 2020	856	$ 0.2	1,207.2	0.7	(352.1)	0
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Issuance of common stock in connection with equity incentive plans - net of tax withholding (in shares)		1.7
Issuance of common stock in connection with equity incentive plans - net of tax withholding	(98.2)		(98.2)
Repurchase and retirement of common stock (in shares)		(0.8)
Repurchase and retirement of common stock	(200.4)		(6.1)		(194.3)
Stock-based compensation expense	154.8		154.8
Net unrealized gain on investments - net of tax	(0.7)			(0.7)
Foreign currency translation adjustment	(1.6)			(1.2)
Net income including non-controlling interests	407.9				407.8	0.1
Balance, shares at Sep. 30, 2021		163.4
Balance, end of period at Sep. 30, 2021	1,135.6	$ 0.2	1,257.7	(1.2)	(138.6)	17.5
Balance, shares at Jun. 30, 2021		163.3
Balance, beginning of period at Jun. 30, 2021	1,050.2	$ 0.2	1,245.8	(0.1)	(195.7)	0
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Issuance of common stock in connection with equity incentive plans - net of tax withholding (in shares)		0.4
Issuance of common stock in connection with equity incentive plans - net of tax withholding	(38)		(38)
Repurchase and retirement of common stock (in shares)		(0.3)
Repurchase and retirement of common stock	(108.8)		(2.8)		(106)
Stock-based compensation expense	52.7		52.7
Recognition of non-controlling interests upon business combination	17.8					17.8
Net unrealized gain on investments - net of tax	0.1			0.1
Foreign currency translation adjustment	(1.6)			(1.2)		(0.4)
Net income including non-controlling interests	163.2				163.1	0.1
Balance, shares at Sep. 30, 2021		163.4
Balance, end of period at Sep. 30, 2021	$ 1,135.6	$ 0.2	$ 1,257.7	$ (1.2)	$ (138.6)	$ 17.5

Condensed Consolidated Statem_4

Condensed Consolidated Statements of Cash Flows - USD ($) $ in Millions	9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020
CASH FLOWS FROM OPERATING ACTIVITIES:
Net income including non-controlling interests	$ 407.9	$ 341.8
Adjustments to reconcile net income to net cash provided by operating activities:
Stock-based compensation	154.8	143
Amortization of deferred contract costs	126.9	99.8
Depreciation and amortization	59.1	52.1
Amortization of investment premiums	4.8	0.2
Loss from equity method investment	2.8	0
Other	4.4	5.8
Changes in operating assets and liabilities, net of impact of business combinations:
Accounts receivable—net	130.6	(3.1)
Inventory	(19.5)	(31)
Prepaid expenses and other current assets	(12.5)	(4.6)
Deferred contract costs	(201)	(143.9)
Deferred tax assets	(91.9)	4.4
Other assets	(15.7)	(2)
Accounts payable	(11.8)	(4.2)
Accrued liabilities	77	16.5
Accrued payroll and compensation	23.1	19.5
Other liabilities	(3.2)	10.3
Deferred revenue	497.1	282.6
Net cash provided by operating activities	1,132.9	787.2
CASH FLOWS FROM INVESTING ACTIVITIES:
Purchases of investments	(1,749.9)	(776.3)
Sales of investments	82.2	141.4
Maturities of investments	1,029	730.3
Purchases of property and equipment	(144.6)	(93.6)
Purchase of investment in privately held company	(160)	0
Payments made in connection with business combinations, net of cash acquired	(73.4)	(9.2)
Purchases of marketable equity securities	(42.5)	(0.4)
Net cash used in investing activities	(1,059.2)	(7.8)
CASH FLOWS FROM FINANCING ACTIVITIES:
Proceeds from long-term borrowings, net of discount and underwriting fees	989.4	0
Payments for debt issuance costs	(2.4)	0
Payments of debt assumed in connection with business combination	(2.2)	(4.1)
Repurchase and retirement of common stock	(170)	(1,046)
Proceeds from issuance of common stock	20.7	18.2
Taxes paid related to net share settlement of equity awards	(118.9)	(86.5)
Other	(0.2)	(1.2)
Net cash provided by (used in) financing activities	716.4	(1,119.6)
EFFECT OF EXCHANGE RATE CHANGES ON CASH AND CASH EQUIVALENTS	0.2	0
NET INCREASE (DECREASE) IN CASH AND CASH EQUIVALENTS	790.3	(340.2)
CASH AND CASH EQUIVALENTS—Beginning of period	1,061.8	1,222.5
CASH AND CASH EQUIVALENTS—End of period	1,852.1	882.3
SUPPLEMENTAL DISCLOSURES OF CASH FLOW INFORMATION:
Cash paid for income taxes—net	69.9	27.6
Operating lease liabilities arising from obtaining right-of-use assets	31	14.7
NON-CASH INVESTING AND FINANCING ACTIVITIES:
Transfers of evaluation units from inventory to property and equipment	14.6	14.8
Liability for purchase of property and equipment	23.8	26.1
Liability incurred for repurchase of common stock	$ 30.4	$ 0

Summary of Significant Accounti

Summary of Significant Accounting Policies	9 Months Ended
	Sep. 30, 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 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. The results of operations for the three and nine months ended September 30, 2021 are not necessarily indicative of the results to be expected 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 condensed consolidated financial statements include the accounts of Fortinet, Inc. and its subsidiaries. We consolidate all legal entities in which we have an absolute controlling financial interest. All intercompany balances and transactions have been eliminated in consolidation. Investments in common stock or in-substance common stock of entities that provide us with the ability to exercise significant influence, but not an absolute controlling financial interest, over the investee are accounted for under the equity method of accounting. Investments accounted for under the equity method are initially recorded at cost. Subsequently, we recognize our proportionate share of the entities’ net income or loss and the amortization of any basis differences through the condensed consolidated statements of income and as an adjustment to the investment balance. We record our share of the results of equity method investments on a three-month lag basis as income or loss from equity method investments, net of tax in the condensed consolidated statements of income. We evaluate our equity method investments at the end of each reporting period to determine whether events or changes in business circumstances indicate that the carrying value of the investment may not be recoverable. As of September 30, 2021, our investment in Linksys Holdings, Inc. (“Linksys”) was our only equity method investment. 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 other material changes to our significant accounting policies as of and for the three and nine months ended September 30, 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. Recent Accounting Standards Not Yet Effective Business Combinations In October 2021, the FASB issued ASU 2021-08—Business Combinations (“Topic 805”): Accounting for Contract Assets and Contract Liabilities from Contracts with Customers. The amendments in ASU 2021-08 require that an entity

Revenue Recognition

Revenue Recognition	9 Months Ended
	Sep. 30, 2021
Revenue from Contract with Customer [Abstract]
REVENUE RECOGNITION	REVENUE RECOGNITION We 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 Nine Months Ended September 30, September 30, September 30, September 30, Product $ 337.1 $ 223.8 $ 876.1 $ 628.0 Service: Security subscription 287.4 235.4 815.6 669.4 Technical support and other 242.7 191.9 686.9 549.0 Total service revenue 530.1 427.3 1,502.5 1,218.4 Total revenue $ 867.2 $ 651.1 $ 2,378.6 $ 1,846.4 Deferred Revenue During the three months ended September 30, 2021 and September 30, 2020, we recognized $309.2 million and $263.1 million in service revenue that was included in the deferred revenue balance as of December 31, 2020 and December 31, 2019, respectively. During the nine months ended September 30, 2021 and September 30, 2020, we recognized $1.10 billion and $921.7 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 September 30, 2021, the aggregate amount of the transaction price allocated to remaining performance obligations was $3.11 billion, which was substantially comprised of deferred security subscription and technical support services revenue. We expect to recognize approximately $1.62 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 $2.6 million and $2.5 million as of September 30, 2021 and December 31, 2020, respectively. Provisions, write-offs and recoveries were not material during the nine months ended September 30, 2021 and 2020. Deferred Contract Costs Amortization of deferred contract costs during the three months ended September 30, 2021 and 2020 were $45.1 million and $35.3 million, respectively. Amortization of deferred contract costs during the nine months ended September 30, 2021 and 2020 were $126.9 million and $99.8 million, respectively.

Financial Instruments and Fair

Financial Instruments and Fair Value	9 Months Ended
	Sep. 30, 2021
Financial Instruments and Fair Value [Abstract]
FINANCIAL INSTRUMENTS AND FAIR VALUE	FINANCIAL INSTRUMENTS AND FAIR VALUE The following tables summarize our available-for-sale securities (in millions): September 30, 2021 Amortized Unrealized Unrealized Fair Commercial paper $ 647.0 $ 0.1 $ — $ 647.1 Corporate debt securities 484.6 0.2 (0.2) 484.6 Certificates of deposit and term deposits (1) 214.5 — — 214.5 U.S. government securities 174.7 — (0.1) 174.6 Municipal Bonds 5.5 — — 5.5 Total available-for-sale securities $ 1,526.3 $ 0.3 $ (0.3) $ 1,526.3 December 31, 2020 Amortized Unrealized Unrealized Fair Commercial paper $ 185.4 $ — $ — $ 185.4 Corporate debt securities 410.5 1.0 — 411.5 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 available-for-sale securities that have been in a continuous unrealized loss position (in millions): September 30, 2021 Less Than 12 Months 12 Months or Greater Total Fair Unrealized Fair Unrealized Fair Unrealized Commercial paper $ 116.3 $ — $ — $ — $ 116.3 $ — Corporate debt securities 281.0 (0.2) — — 281.0 (0.2) Certificates of deposit and term deposits 15.8 — — — 15.8 — U.S. government securities 80.6 (0.1) — — 80.6 (0.1) Municipal Bonds 5.4 — — — 5.4 — Total available-for-sale securities $ 499.1 $ (0.3) $ — $ — $ 499.1 $ (0.3) December 31, 2020 Less Than 12 Months 12 Months or Greater Total Fair Unrealized Fair Unrealized Fair Unrealized Commercial paper $ 61.5 $ — $ — $ — $ 61.5 $ — Corporate debt securities 111.3 — — — 111.3 — Certificates of deposit and term deposits 29.5 — — — 29.5 — U.S. government securities 38.1 — — — 38.1 — Total available-for-sale securities $ 240.4 $ — $ — $ — $ 240.4 $ — The contractual maturities of our investments were as follows (in millions): September 30, December 31, Due within one year $ 1,228.1 $ 775.5 Due within one to three years 298.2 118.3 Total $ 1,526.3 $ 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 equity and in comprehensive income. Accrued interest receivable of $2.4 million as of September 30, 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. Our marketable equity securities were $40.8 million as of September 30, 2021. The changes in fair value of our marketable equity securities are recorded in other expense, net on the condensed consolidated statements of income. We recognized $3.7 million loss and $0.1 million loss during the three months ended September 30, 2021 and 2020, respectively, and $2.9 million loss and $0.3 million gain during the nine months ended September 30, 2021 and 2020, respectively. 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, certain U.S. government securities and marketable equity 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): September 30, 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: Commercial paper $ 651.1 $ — $ 651.1 $ — $ 197.2 $ — $ 197.2 $ — Corporate debt securities 484.6 — 484.6 — 413.7 — 413.7 — Certificates of deposit and term deposits 214.5 — 214.5 — 112.0 — 112.0 — U.S. government securities 174.6 164.6 10.0 — 184.9 184.9 — — Money market funds 32.3 32.3 — — 152.7 152.7 — — Municipal Bonds 5.5 — 5.5 — — — — — Marketable equity securities 40.8 40.8 — — — — — — Total $ 1,603.4 $ 237.7 $ 1,365.7 $ — $ 1,060.5 $ 337.6 $ 722.9 $ — Reported as: Cash equivalents $ 36.3 $ 166.7 Marketable equity securities 40.8 — Short-term investments 1,228.1 775.5 Long-term investments 298.2 118.3 Total $ 1,603.4 $ 1,060.5 There were no transfers between Level 1 and Level 2 of the fair value hierarchy during the nine months ended September 30, 2021 and year ended December 31, 2020.

Inventory

Inventory	9 Months Ended
	Sep. 30, 2021
Inventory Disclosure [Abstract]
INVENTORY	INVENTORY Inventory consisted of the following (in millions): September 30, December 31, Raw materials $ 35.6 $ 13.8 Work in process 7.9 — Finished goods 134.4 126.0 Inventory $ 177.9 $ 139.8

Property and Equipment_Net

Property and Equipment—Net	9 Months Ended
	Sep. 30, 2021
Property, Plant and Equipment [Abstract]
PROPERTY AND EQUIPMENT—Net	PROPERTY AND EQUIPMENT—Net Property and equipment—net consisted of the following (in millions): September 30, December 31, Land $ 128.3 $ 93.3 Buildings and improvements 365.4 150.6 Computer equipment and software 166.4 137.2 Leasehold improvements 38.8 31.9 Evaluation units 19.8 19.8 Furniture and fixtures 27.0 21.3 Construction-in-progress 16.9 166.4 Total property and equipment 762.6 620.5 Less: accumulated depreciation (206.0) (172.5) Property and equipment—net $ 556.6 $ 448.0 In September 2021, we purchased certain real estate in Burnaby, Canada for $37.7 million. The purchase was accounted for under the asset acquisition method. The cost of the assets acquired was allocated to land and buildings based on their relative fair values. The amounts allocated to land and buildings were $16.6 million and $21.1 million, respectively. Depreciation expense was $18.1 million and $13.9 million during the three months ended September 30, 2021 and 2020, respectively. Depreciation expense was $47.4 million and $41.6 million during the nine months ended September 30, 2021 and 2020, respectively.

Investments in Privately-Held C

Investments in Privately-Held Companies	9 Months Ended
	Sep. 30, 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 for a 32.6% ownership interest. Linksys provides router connectivity solutions to the consumer and small business markets. On September 24, 2021, we invested an additional $85.0 million in cash for shares of Series A Preferred Stock of Linksys, and as of September 30, 2021, we held 50.8% of the outstanding common stock (on an as-converted basis) of Linksys. We have concluded that our investment in Linksys is an in-substance common stock investment and that we do not hold an absolute controlling financial interest in Linksys, but that we have the ability to exercise significant influence over the operating and financial policies of Linksys. Therefore, we determined to account for this investment using the equity method of accounting. We record our share of Linksys’ financial results on a three-month lag basis. Our share of the earnings of Linksys’ financial results, which are accounted for under the three-month lag basis, was $2.8 million for the three and nine months ended September 30, 2021, and has been recorded in loss from equity method investment on the condensed consolidated statements of income. As of September 30, 2021, the investment was included in other assets on our condensed consolidated balance sheet. Transaction costs related to this investment were not material. Other investments Our other investments in the equity securities of privately held companies without readily determinable fair values totaled $1.0 million as of September 30, 2021 and December 31, 2020.

Business Combinations

Business Combinations	9 Months Ended
	Sep. 30, 2021
Business Combination and Asset Acquisition [Abstract]
BUSINESS COMBINATIONS	BUSINESS COMBINATION AlaxalA Networks Corporation On August 31, 2021, we closed an acquisition of 75% of equity interests in AlaxalA Networks Corporation (“AlaxalA”), a privately held network hardware equipment company in Japan, for $64.2 million in cash. We acquired the equity interest in AlaxalA to help address the increasing need for secure switches integrated with FortiGate Firewalls and Security Fabric functionality, and, over time, to innovate and rebrand certain of AlaxalA’s switches to offer a broader suite of secure switches globally. Under the acquisition method of accounting in accordance with ASC 805, the total preliminary purchase price was allocated to AlaxalA’s identifiable tangible and intangible assets acquired and liabilities assumed based on their estimated fair values using management’s best estimates and assumptions to assign fair value as of the acquisition date. The following table provides the assets acquired and liabilities assumed as of the date of acquisition: (in millions) Estimated Fair Value ASSETS Cash $ 1.1 Accounts receivable—net 15.6 Inventory 33.4 Prepaid expenses and other current assets 2.9 Property and equipment 5.3 Goodwill 29.0 Other intangible assets 48.0 Other long-term assets 2.7 TOTAL ASSETS $ 138.0 LIABILITIES Accounts payable $ 11.0 Current portion of long-term debt 20.2 Accrued and other current liabilities 14.7 Other long-term liabilities 10.1 TOTAL LIABILITIES $ 56.0 NON-CONTROLLING INTERESTS $ 17.8 Net purchase consideration $ 64.2 The excess of the purchase consideration and the fair value of non-controlling interests over the fair value of net tangible and identified intangible assets acquired was recorded as goodwill, which is not deductible for tax purposes. Goodwill is primarily attributable to the assembled workforce of AlaxalA and the anticipated operational synergies. The fair value of the non-controlling interests of $17.8 million was estimated based on the non-controlling interests ’ respective share of the AlaxalA business value. Identified intangible assets acquired and their estimated useful lives (in years) as of August 31, 2021, were as follows (in millions, except years) : Fair Value Estimated Useful Life (in years) Developed technology $ 26.6 4 Customer relationships 10.0 10 Trade name 6.4 10 Backlog 5.0 1 Total identified intangible assets: $ 48.0 Developed technology relates to AlaxalA ’ s network equipment. We valued the developed technology using the relief-from-royalty method under the income approach. This method reflects the present value of the projected cash flows that are expected to be generated by the developed technology. The economic useful life was determined based on the technology cycle related to each developed technology, as well as the cash flows over the forecast period. Customer relationships represent the fair value of future projected revenue that will be derived from sales to existing customers of AlaxalA. Customer contracts and related relationships were valued using the multi-period excess earnings method. This method reflects the present value of the projected cash flows that are expected to be generated by the customer contracts and relationships less charges representing the contribution of other assets to those cash flows. The economic useful life was determined based on historical customer turnover rates. Trade name relates to the “AlaxalA” trade name. The fair value was determined by applying the relief-from-royalty method under the income approach. This method is based on the application of a royalty rate to forecasted revenue under the trade name. The economic useful life was determined based on the expected life of the trade name and the cash flows anticipated over the forecast period. Customer backlog relates to the unfulfilled customer contract orders. Backlog was valued using the multi-period excess earnings method. This method reflects the present value of the projected cash flows that are expected to be generated by the execution of the unfulfilled customer contract orders less charges representing the contribution of other assets to those cash flows. The economic useful life was determined based on the anticipated contract orders ’ execution timeframe. Our estimates and assumptions are subject to change within the measurement period, which is up to 12 months after the acquisition date. The allocation of the purchase price for this acquisition has been prepared on a preliminary basis and changes to the allocation of certain assets and liabilities may occur as additional information becomes available. The primary areas of the purchase price that are not yet finalized are related to income taxes and the valuation of acquired assets and assumed liabilities. The operating results of the acquired company were included in our condensed consolidated financial statements from the date of acquisition which was August 31, 2021. For the period from September 1, 2021 through September 30, 2021, AlaxalA contributed revenue of $15.6 million. Income before income taxes for the period from September 1, 2021 through September 30, 2021 was not material. Acquisition-related costs for this acquisition were not material and were recorded as general and administrative expense . The following unaudited pro forma financial information presents the combined results of operations of Fortinet, Inc. and AlaxalA, as if AlaxalA had been acquired as of the beginning of business on January 1, 2020. The unaudited pro forma financial information is presented for informational purposes only and is not necessarily indicative of our consolidated results of operations of the combined business that would have been achieved if the acquisition had taken place at the beginning of business on January 1, 2020, or of the results of our future operations of the combined business. The following unaudited pro forma financial information for all periods presented includes purchase accounting adjustments for amortization of acquired intangible assets, depreciation of acquired property and equipment, the purchase accounting effect on inventory acquired and related tax effects (in millions): Three Months Ended Nine Months Ended September 30, September 30, September 30, September 30, Pro forma revenue $ 887.6 $ 684.3 $ 2,460.5 $ 1,939.6 Pro forma net income attributable to Fortinet, Inc. $ 165.1 $ 122.8 $ 407.3 $ 334.8 ShieldX Networks, Inc. On March 10, 2021, we closed an acquisition of certain assets and liabilities of ShieldX Networks Inc. (“ShieldX”), a provider of a security platform focusing on protecting multi-cloud data centers from the risk of lateral movement that can lead to attacks such as ransomware, data loss and service disruption, for $10.8 million in cash. This acquisition was accounted for as a business combination using the acquisition method of accounting. Of the purchase price, $6.2 million was allocated to goodwill, $4.1 million was allocated to developed technology intangible asset and $0.5 million was allocated to other net assets acquired. Goodwill recorded in connection with this acquisition represents the value we expect to be created through expansion into markets within our existing business and potential cost savings and synergies. All acquired goodwill is expected to be deductible for tax purposes. Acquisition-related costs related to this acquisition were not material and were recorded as general and administrative expense.

Goodwill and Other Intangible A

Goodwill and Other Intangible Assets - Net	9 Months Ended
	Sep. 30, 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 Additions due to business combinations 35.2 Foreign currency translation adjustments (0.6) Balance—September 30, 2021 $ 127.6 There were no impairments to goodwill during the nine months ended September 30, 2021 or during prior periods. Other Intangible Assets—Net The following tables present other intangible assets—net (in millions, except years): September 30, 2021 Weighted-Average Useful Life (in Years) Gross Accumulated Amortization Net Other intangible assets—net: Finite-lived intangible assets: Developed technologies 4.0 $ 89.5 $ 40.8 $ 48.7 Customer relationships 5.7 34.6 23.0 11.6 Trade name 10.0 6.3 0.1 6.2 Backlog 1.0 4.9 $ 0.4 4.5 Total other intangible assets—net $ 135.3 $ 64.3 $ 71.0 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 $4.8 million and $2.8 million during the three months ended September 30, 2021 and 2020, respectively. Amortization expense was $11.7 million and $10.5 million during the nine months ended September 30, 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) $ 6.8 2022 22.9 2023 16.3 2024 11.5 2025 6.2 Thereafter 7.3 Total $ 71.0

Net Income Per Share

Net Income Per Share	9 Months Ended
	Sep. 30, 2021
Earnings Per Share [Abstract]
NET INCOME PER SHARE	NET INCOME PER SHAREBasic net income per share is computed by dividing net income attributable to Fortinet, Inc. 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 Nine Months Ended September 30, September 30, September 30, September 30, Numerator: Net income including non-controlling interests $ 163.2 $ 123.4 $ 407.9 $ 341.8 Net income attributable to non-controlling interests 0.1 — 0.1 — Net income attributable to Fortinet, Inc. $ 163.1 $ 123.4 $ 407.8 $ 341.8 Denominator: Basic shares: Weighted-average common stock outstanding-basic 163.5 162.1 163.3 164.8 Diluted shares: Weighted-average common stock outstanding-basic 163.5 162.1 163.3 164.8 Effect of potentially dilutive securities: RSUs 2.4 2.3 2.2 2.4 Stock options 1.8 1.2 1.6 1.2 Weighted-average shares used to compute diluted net income per share attributable to Fortinet, Inc. common stockholders 167.7 165.6 167.1 168.4 Net income per share attributable to Fortinet, Inc. common stockholders: Basic $ 1.00 $ 0.76 $ 2.50 $ 2.07 Diluted $ 0.97 $ 0.75 $ 2.44 $ 2.03 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 Nine Months Ended September 30, September 30, September 30, September 30, RSUs 0.1 0.3 0.2 0.3 Stock options — 0.6 0.3 0.5 Total 0.1 0.9 0.5 0.8

Leases

Leases	9 Months Ended
	Sep. 30, 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 six 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 Nine Months Ended September 30, September 30, September 30, September 30, Operating lease expense $ 6.8 $ 4.8 $ 18.9 $ 13.5 Variable lease expense (1) 0.8 0.7 2.3 1.7 Short-term lease expense 1.0 1.0 2.7 2.9 Total lease expense $ 8.6 $ 6.5 $ 23.9 $ 18.1 (1) Variable lease expense for the three and nine months ended September 30, 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 September 30, December 31, Operating lease ROU assets - non-current Other assets $ 63.6 $ 49.3 Operating lease liabilities - current Accrued liabilities $ 25.0 $ 19.1 Operating lease liabilities - non-current Other liabilities 40.5 34.0 Total operating lease liabilities $ 65.5 $ 53.1 Weighted average remaining lease term in years - operating leases 3.1 3.5 Weighted average discount rate - operating leases 2.2 % 3.2 % Supplemental cash flow information related to leases was as follows (in millions): Nine Months Ended September 30, September 30, Cash paid for amounts included in the measurement of lease liabilities Operating cash flows used for operating leases $ 18.8 $ 13.8 Maturities of operating lease liabilities as of September 30, 2021 were as follows (in millions): Year Ending December 31, Amount 2021 (the remainder of 2021) $ 6.8 2022 25.0 2023 18.4 2024 11.8 2025 4.3 Thereafter 1.4 Total lease payments 67.7 Less imputed interest (2.2) Total $ 65.5 As of September 30, 2021, we had additional minimum lease payments of $7.7 million relating to operating leases that had been signed but had not yet commenced. These leases will commence during 2021 and will have lease terms of approximately two
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 six 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 Nine Months Ended September 30, September 30, September 30, September 30, Operating lease expense $ 6.8 $ 4.8 $ 18.9 $ 13.5 Variable lease expense (1) 0.8 0.7 2.3 1.7 Short-term lease expense 1.0 1.0 2.7 2.9 Total lease expense $ 8.6 $ 6.5 $ 23.9 $ 18.1 (1) Variable lease expense for the three and nine months ended September 30, 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 September 30, December 31, Operating lease ROU assets - non-current Other assets $ 63.6 $ 49.3 Operating lease liabilities - current Accrued liabilities $ 25.0 $ 19.1 Operating lease liabilities - non-current Other liabilities 40.5 34.0 Total operating lease liabilities $ 65.5 $ 53.1 Weighted average remaining lease term in years - operating leases 3.1 3.5 Weighted average discount rate - operating leases 2.2 % 3.2 % Supplemental cash flow information related to leases was as follows (in millions): Nine Months Ended September 30, September 30, Cash paid for amounts included in the measurement of lease liabilities Operating cash flows used for operating leases $ 18.8 $ 13.8 Maturities of operating lease liabilities as of September 30, 2021 were as follows (in millions): Year Ending December 31, Amount 2021 (the remainder of 2021) $ 6.8 2022 25.0 2023 18.4 2024 11.8 2025 4.3 Thereafter 1.4 Total lease payments 67.7 Less imputed interest (2.2) Total $ 65.5 As of September 30, 2021, we had additional minimum lease payments of $7.7 million relating to operating leases that had been signed but had not yet commenced. These leases will commence during 2021 and will have lease terms of approximately two

Debt

Debt	9 Months Ended
	Sep. 30, 2021
Debt Disclosure [Abstract]
DEBT	DEBT 2026 and 2031 Senior Notes 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 September 30, 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 September 30, 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 12.0 Total long-term debt $ 988.0 As of September 30, 2021 we accrued interest payable of $0.7 million, and there are no financial covenants with which we must comply. During the three and nine months ended September 30, 2021 we recorded $4.4 million and $10.2 million of total interest expense in relation to these Senior Notes, respectively. No interest costs were capitalized for the three and nine months ended September 30, 2021, as the costs that qualified for capitalization were not material. The total estimated fair value of the outstanding Senior Notes was approximately $991.1 million, including accrued and unpaid interest, as of September 30, 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. AlaxalA debt In connection with our acquisition of AlaxalA, we assumed certain current debt liabilities of $20.2 million as of August 31, 2021. We concluded that the fair value of debt approximated its book value as of the acquisition date. We had $17.6 million of this debt outstanding and recorded as current portion of long-term debt on our condensed consolidated balance sheet as of September 30, 2021. We repaid this balance in full in October 2021. As of September 30, 2021, the accrued interest under the assumed AlaxalA debt obligations was not material. During the post-acquisition period from September 1, 2021 through September 30, 2021, interest expense related to AlaxalA debt was not material.

Mutual Covenant-Not-to-Sue and

Mutual Covenant-Not-to-Sue and Release Agreement	9 Months Ended
	Sep. 30, 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. During the three months ended September 30, 2021 and 2020, we recorded $1.1 million gain on IP matter in our condensed consolidated statements of income. During the nine months ended September 30, 2021 and 2020, we recorded $3.4 million and $39.0 million gain on IP matter in our condensed consolidated statements of income, respectively. We recorded $6.4 million and $9.8 million in accrued liabilities and other liabilities in our condensed consolidated balance sheets as of September 30, 2021 and December 31, 2020, respectively.

Commitments and Contingencies

Commitments and Contingencies	9 Months Ended
	Sep. 30, 2021
Commitments and Contingencies Disclosure [Abstract]
COMMITMENTS AND CONTINGENCIES	COMMITMENTS AND CONTINGENCIES The following table summarizes our inventory purchase commitments as of September 30, 2021 (in millions): Total 2021 2022 2023 2024 2025 Thereafter Inventory purchase commitments $ 868.0 $ 376.7 $ 491.3 $ — $ — $ — $ — 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 supply chain matters and other market conditions. In order to reduce manufacturing lead times, plan for adequate component supply and incentivize suppliers to deliver, we may issue purchase orders to some of our independent contract manufacturers, which are non-cancelable. As of September 30, 2021, we had $868.0 million of open purchase orders with our independent contract manufacturers that are non-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 September 30, 2021, we had $68.9 million in other contractual commitments having a remaining term in excess of one year that are non-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. In October 2021, we held settlement discussions related to an existing patent infringement lawsuit. Pursuant to such discussions, we may enter into an agreement that provides for the settlement and dismissal of the patent lawsuit and a mutual covenant not to sue for a defined duration of time. As a result, we have determined that a loss in connection with such lawsuit is now probable. We accrued $5 million as a loss contingency in the quarter ended September 30, 2021 and the associated charge was recorded against revenue in the income statement. Litigation loss contingency accruals associated with other outstanding cases were not material as of September 30, 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.

Equity

Equity	9 Months Ended
	Sep. 30, 2021
Share-based Payment Arrangement [Abstract]
EQUITY	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 September 30, 2021, there were a total of 11.7 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 1.1 190.47 Forfeited (0.3) 111.20 Vested (1.9) 81.15 Balance—September 30, 2021 3.6 $ 123.67 Stock compensation expense is recognized on a straight-line basis over the vesting period of each RSU. As of September 30, 2021, total compensation expense related to unvested RSUs granted to employees and non-employees under the Amended Plan, but not yet recognized, was $391.2 million, with a weighted-average remaining vesting period of 2.7 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 Nine Months Ended September 30, September 30, September 30, September 30, Shares withheld for taxes 0.1 0.2 0.6 0.7 Amount withheld for taxes $ 42.9 $ 27.6 $ 119.0 $ 86.5 Employee Stock Options The following table summarizes the weighted-average assumptions relating to our employee stock options: Three Months Ended Nine Months Ended September 30, September 30, September 30, September 30, Expected term in years 4.4 4.4 4.4 4.4 Volatility 36.9 % 39.9 % 39.2 % 34.6 % Risk-free interest rate 0.7 % 0.2 % 0.5 % 1.1 % 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 0.6 179.95 Forfeited (0.1) 117.60 Exercised (0.4) 53.26 Balance—September 30, 2021 2.8 $ 90.20 Options vested and expected to vest—September 30, 2021 2.8 $ 90.20 4.1 $ 567.2 Options exercisable—September 30, 2021 1.6 $ 56.62 3.1 $ 379.9 The aggregate intrinsic value represents the difference between the exercise price of stock options and the quoted market price of our common stock on September 30, 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 September 30, 2021, total compensation expense related to unvested stock options granted to employees but not yet recognized was $46.6 million, with a weighted-average remaining vesting period of 2.9 years. Additional information related to our stock options is summarized below (in millions, except per share amounts): Three Months Ended Nine Months Ended September 30, September 30, September 30, September 30, Weighted-average fair value per share granted $ 95.33 $ 43.80 $ 58.69 $ 35.76 Intrinsic value of options exercised $ 20.9 $ 5.5 $ 60.2 $ 35.8 Fair value of options vested $ 3.3 $ 2.5 $ 13.9 $ 10.9 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 Nine Months Ended September 30, September 30, September 30, September 30, Cost of product revenue $ 0.4 $ 0.4 $ 1.3 $ 1.2 Cost of service revenue 4.1 3.3 11.4 9.5 Research and development 14.5 12.7 42.0 35.6 Sales and marketing 27.6 27.7 82.1 81.3 General and administrative 6.9 5.9 20.2 17.3 Total stock-based compensation expense $ 53.5 $ 50.0 $ 157.0 $ 144.9 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 Nine Months Ended September 30, September 30, September 30, September 30, RSUs $ 48.5 $ 46.4 $ 142.8 $ 134.5 Stock options 5.0 3.6 14.2 10.4 Total stock-based compensation expense $ 53.5 $ 50.0 $ 157.0 $ 144.9 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 Nine Months Ended September 30, September 30, September 30, September 30, Income tax benefit associated with stock-based compensation $ 11.7 $ 11.0 $ 34.5 $ 31.9 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. Refer to Note 18. Subsequent Events for information of the approved $1.25 billion increase in the authorized stock repurchase under the Repurchase Program in October 2021. During the three and nine months ended September 30, 2021, we repurchased 0.3 million and 0.8 million shares of common stock, respectively, under the Repurchase Program in open-market transactions at a weighted-average price of $294.07 per share and $242.95 per share, respectively, for an aggregate purchase price of $108.8 million and $200.4 million, respectively. As of September 30, 2021, $812.3 million remained available for future share repurchases under the Repurchase Program.

Income Taxes

Income Taxes	9 Months Ended
	Sep. 30, 2021
Income Tax Disclosure [Abstract]
INCOME TAXES	INCOME TAXES Our effective tax rate was negative 6% for the three months ended September 30, 2021, compared to an effective tax rate of 4% for the same period last year. Our effective tax rate was 2% for the nine months ended September 30, 2021, compared to an effective tax rate of 8% 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 September 30, 2021 and 2020 were composed of U.S. federal and state taxes, withholding taxes and foreign taxes that amounted to $40.1 million and $33.8 million , respectively. The tax rate for the three months ended September 30, 2021 was impacted by a tax benefit of $8.7 million from the FDII deduction and excess tax benefits from stock-based compensation expense of $25.0 million . In addition, the tax rate for the three months ended September 30, 2021 was further impacted by a tax benefit of $15.7 million for a change in tax accounting positions in finalization of the prior year tax return. The tax rate for the three months ended September 30, 2020 was impacted by a tax benefit of $16.3 million from the FDII deduction and excess tax benefits from stock-based compensation expense of $12.5 million . The tax rates for the nine months ended September 30, 2021 and 2020 were composed of U.S. federal and state taxes, withholding taxes and foreign taxes that amounted to $115.8 million and $100.7 million , respectively. The tax rate for the nine months ended September 30, 2021 was impacted by a tax benefit of $23.9 million from the FDII deduction, excess tax benefits from stock-based compensation expense o f $60.3 million and release of reserves o f $5.5 million on uncertain tax positions and the interest due to the expiration of the statute of limitations. In addition, the tax rate for the nine months ended September 30, 2021 was further impacted by a tax benefit of $15.7 million for a change in tax accounting positions in finalization of the prior year tax return. The tax rate for the nine month s ended September 30, 2020 was impacted by a tax benefit of $25.9 million from the FDII deduction, excess tax benefits from stock-based compensation expense of $37.6 million and release of reserves of $9.0 million on uncertain tax positions and the interest due to the expiration of the statute of limitations. As of September 30, 2021 and December 31, 2020, unrecognized tax benefits were $80.7 million and $77.3 million , respectively. If recognized, $73.3 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 September 30, 2021 and December 31, 2020, accrued interest and penalties were $16.2 million and $14.5 million, respectively. It is reasonably possible that our gross unrecognized tax benefits will decrease by up to $27.3 million in the next 12 months, due to the lapse of the statute of limitations. This decrease, if recognized, would favorably 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. The Coronavirus Aid, Relief, and Economic Security Act (the “CARES Act”) was signed into law on March 27, 2020. The CARES Act provides numerous tax provisions and other stimulus measures, including temporary changes regarding the prior and future utilization of net operating losses, temporary changes to the prior and future limitations on interest deductions, temporary suspension of certain payment requirements for the employer portion of Social Security taxes, technical corrections from prior tax legislation for tax depreciation of certain qualified improvement property and the creation of certain refundable employee retention credits. There is no material tax impact on our condensed consolidated financial statements. On July 9, 2020, the United States Department of the Treasury (the “U.S. Treasury”) and the Internal Revenue Service (the “IRS”) released final Section 250 regulations, providing guidance on the foreign-derived intangible income deduction and the global intangible low-taxed income. Generally, the final regulations are applicable for taxable years beginning on or after January 1, 2021. However, taxpayers may apply the final regulations for taxable years beginning on or after January 1, 2018. We have elected to apply the final regulations to the year ending December 31, 2020 and included the tax impact from the final regulations on our foreign-derived intangible income deduction calculation.

Defined Contribution Plans

Defined Contribution Plans	9 Months Ended
	Sep. 30, 2021
Retirement Benefits [Abstract]
DEFINED CONTRIBUTION PLANS	DEFINED CONTRIBUTION PLANS Our tax-deferred savings plan under our 401(k) Plan permits participating U.S. employees to contribute a portion of their pre-tax or after-tax earnings. In Canada, we have a Group Registered Retirement Savings Plan Program (the “RRSP”), which permits participants to make tax-deductible contributions. Our board of directors approved 50% matching contributions on employee contributions up to 4% of each employee’s eligible earnings. Our matching contributions to our 401(k) Plan and the RRSP for the three months ended September 30, 2021 and 2020 were $2.5 million and $2.1 million, respectively. Our matching contributions to our 401(k) Plan and the RRSP for the nine months ended September 30, 2021 and 2020 were $7.9 million and $6.5 million, respectively.

Segment Information

Segment Information	9 Months Ended
	Sep. 30, 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 Nine Months Ended Revenue September 30, September 30, September 30, September 30, Americas: United States $ 258.4 $ 206.0 $ 722.6 $ 589.1 Other Americas 91.7 66.4 255.4 186.9 Total Americas 350.1 272.4 978.0 776.0 Europe, Middle East and Africa (“EMEA”) 323.2 243.3 905.1 693.5 Asia Pacific (“APAC”) 193.9 135.4 495.5 376.9 Total revenue $ 867.2 $ 651.1 $ 2,378.6 $ 1,846.4 Property and Equipment — net September 30, December 31, Americas: United States $ 357.1 $ 296.3 Canada 160.9 121.3 Latin America 1.8 2.0 Total Americas 519.8 419.6 EMEA 23.8 20.6 APAC 13.0 7.8 Total property and equipment—net $ 556.6 $ 448.0 The following distributors accounted for 10% or more of our revenue: Three Months Ended Nine Months Ended September 30, September 30, September 30, September 30, Exclusive Networks Group (“Exclusive”) 31 % 29 % 32 % 30 % Ingram Micro, Inc. (“Ingram Micro”) 12 % 10 % 12 % 10 % The following distributors accounted for 10% or more of net accounts receivable: September 30, December 31, Exclusive 30 % 34 % TD Synnex 15 % * Ingram Micro 11 % 11 %

Subsequent Events

Subsequent Events	9 Months Ended
	Sep. 30, 2021
Subsequent Events [Abstract]
SUBSEQUENT EVENTS	SUBSEQUENT EVENTS Debt Repayment In October 2021, we fully repaid the outstanding $17.6 million of debt liabilities assumed in the AlaxalA transaction. Building Purchase In October 2021, we purchased real property in Texas totaling approximately 87,000 square feet for a cash payment of $22.5 million. Share Repurchase Program In October 2021, our board of directors approved a $1.25 billion increase in the authorized stock repurchase under the Repurchase Program and extended the term of the Repurchase Program to February 28, 2023, bringing the aggregate amount authorized to be repurchased to $4.25 billion of our outstanding common stock through February 28, 2023.

Summary of Significant Accoun_2

Summary of Significant Accounting Policies (Policies)	9 Months Ended
	Sep. 30, 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 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. The results of operations for the three and nine months ended September 30, 2021 are not necessarily indicative of the results to be expected 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 condensed consolidated financial statements include the accounts of Fortinet, Inc. and its subsidiaries. We consolidate all legal entities in which we have an absolute controlling financial interest. All intercompany balances and transactions have been eliminated in consolidation. Investments in common stock or in-substance common stock of entities that provide us with the ability to exercise significant influence, but not an absolute controlling financial interest, over the investee are accounted for under the equity method of accounting. Investments accounted for under the equity method are initially recorded at cost. Subsequently, we recognize our proportionate share of the entities’ net income or loss and the amortization of any basis differences through the condensed consolidated statements of income and as an adjustment to the investment balance. We record our share of the results of equity method investments on a three-month lag basis as income or loss from equity method investments, net of tax in the condensed consolidated statements of income. We evaluate our equity method investments at the end of each reporting period to determine whether events or changes in business circumstances indicate that the carrying value of the investment may not be recoverable. As of September 30, 2021, our investment in Linksys Holdings, Inc. (“Linksys”) was our only equity method investment. 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 other material changes to our significant accounting policies as of and for the three and nine months ended September 30, 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. Recent Accounting Standards Not Yet Effective Business Combinations In October 2021, the FASB issued ASU 2021-08—Business Combinations (“Topic 805”): Accounting for Contract Assets and Contract Liabilities from Contracts with Customers. The amendments in ASU 2021-08 require that an entity

Revenue Recognition (Tables)

Revenue Recognition (Tables)	9 Months Ended
	Sep. 30, 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 Nine Months Ended September 30, September 30, September 30, September 30, Product $ 337.1 $ 223.8 $ 876.1 $ 628.0 Service: Security subscription 287.4 235.4 815.6 669.4 Technical support and other 242.7 191.9 686.9 549.0 Total service revenue 530.1 427.3 1,502.5 1,218.4 Total revenue $ 867.2 $ 651.1 $ 2,378.6 $ 1,846.4

Financial Instruments and Fai_2

Financial Instruments and Fair Value (Tables)	9 Months Ended
	Sep. 30, 2021
Financial Instruments and Fair Value [Abstract]
Summary of Investments	The following tables summarize our available-for-sale securities (in millions): September 30, 2021 Amortized Unrealized Unrealized Fair Commercial paper $ 647.0 $ 0.1 $ — $ 647.1 Corporate debt securities 484.6 0.2 (0.2) 484.6 Certificates of deposit and term deposits (1) 214.5 — — 214.5 U.S. government securities 174.7 — (0.1) 174.6 Municipal Bonds 5.5 — — 5.5 Total available-for-sale securities $ 1,526.3 $ 0.3 $ (0.3) $ 1,526.3 December 31, 2020 Amortized Unrealized Unrealized Fair Commercial paper $ 185.4 $ — $ — $ 185.4 Corporate debt securities 410.5 1.0 — 411.5 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 available-for-sale securities that have been in a continuous unrealized loss position (in millions): September 30, 2021 Less Than 12 Months 12 Months or Greater Total Fair Unrealized Fair Unrealized Fair Unrealized Commercial paper $ 116.3 $ — $ — $ — $ 116.3 $ — Corporate debt securities 281.0 (0.2) — — 281.0 (0.2) Certificates of deposit and term deposits 15.8 — — — 15.8 — U.S. government securities 80.6 (0.1) — — 80.6 (0.1) Municipal Bonds 5.4 — — — 5.4 — Total available-for-sale securities $ 499.1 $ (0.3) $ — $ — $ 499.1 $ (0.3) December 31, 2020 Less Than 12 Months 12 Months or Greater Total Fair Unrealized Fair Unrealized Fair Unrealized Commercial paper $ 61.5 $ — $ — $ — $ 61.5 $ — Corporate debt securities 111.3 — — — 111.3 — Certificates of deposit and term deposits 29.5 — — — 29.5 — U.S. government securities 38.1 — — — 38.1 — 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): September 30, December 31, Due within one year $ 1,228.1 $ 775.5 Due within one to three years 298.2 118.3 Total $ 1,526.3 $ 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): September 30, 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: Commercial paper $ 651.1 $ — $ 651.1 $ — $ 197.2 $ — $ 197.2 $ — Corporate debt securities 484.6 — 484.6 — 413.7 — 413.7 — Certificates of deposit and term deposits 214.5 — 214.5 — 112.0 — 112.0 — U.S. government securities 174.6 164.6 10.0 — 184.9 184.9 — — Money market funds 32.3 32.3 — — 152.7 152.7 — — Municipal Bonds 5.5 — 5.5 — — — — — Marketable equity securities 40.8 40.8 — — — — — — Total $ 1,603.4 $ 237.7 $ 1,365.7 $ — $ 1,060.5 $ 337.6 $ 722.9 $ — Reported as: Cash equivalents $ 36.3 $ 166.7 Marketable equity securities 40.8 — Short-term investments 1,228.1 775.5 Long-term investments 298.2 118.3 Total $ 1,603.4 $ 1,060.5

Inventory (Tables)

Inventory (Tables)	9 Months Ended
	Sep. 30, 2021
Inventory Disclosure [Abstract]
Inventory	Inventory consisted of the following (in millions): September 30, December 31, Raw materials $ 35.6 $ 13.8 Work in process 7.9 — Finished goods 134.4 126.0 Inventory $ 177.9 $ 139.8

Property and Equipment_Net (Tab

Property and Equipment—Net (Tables)	9 Months Ended
	Sep. 30, 2021
Property, Plant and Equipment [Abstract]
Property, Plant and Equipment - Net	Property and equipment—net consisted of the following (in millions): September 30, December 31, Land $ 128.3 $ 93.3 Buildings and improvements 365.4 150.6 Computer equipment and software 166.4 137.2 Leasehold improvements 38.8 31.9 Evaluation units 19.8 19.8 Furniture and fixtures 27.0 21.3 Construction-in-progress 16.9 166.4 Total property and equipment 762.6 620.5 Less: accumulated depreciation (206.0) (172.5) Property and equipment—net $ 556.6 $ 448.0

Business Combinations and Asset

Business Combinations and Asset Acquisitions (Tables)	9 Months Ended
	Sep. 30, 2021
Business Combination and Asset Acquisition [Abstract]
Schedule of Recognized Identified Assets Acquired and Liabilities Assumed	The following table provides the assets acquired and liabilities assumed as of the date of acquisition: (in millions) Estimated Fair Value ASSETS Cash $ 1.1 Accounts receivable—net 15.6 Inventory 33.4 Prepaid expenses and other current assets 2.9 Property and equipment 5.3 Goodwill 29.0 Other intangible assets 48.0 Other long-term assets 2.7 TOTAL ASSETS $ 138.0 LIABILITIES Accounts payable $ 11.0 Current portion of long-term debt 20.2 Accrued and other current liabilities 14.7 Other long-term liabilities 10.1 TOTAL LIABILITIES $ 56.0 NON-CONTROLLING INTERESTS $ 17.8 Net purchase consideration $ 64.2
Schedule of Acquired Finite-Lived Intangible Assets	Identified intangible assets acquired and their estimated useful lives (in years) as of August 31, 2021, were as follows (in millions, except years) : Fair Value Estimated Useful Life (in years) Developed technology $ 26.6 4 Customer relationships 10.0 10 Trade name 6.4 10 Backlog 5.0 1 Total identified intangible assets: $ 48.0
Pro Forma Information	The following unaudited pro forma financial information for all periods presented includes purchase accounting adjustments for amortization of acquired intangible assets, depreciation of acquired property and equipment, the purchase accounting effect on inventory acquired and related tax effects (in millions): Three Months Ended Nine Months Ended September 30, September 30, September 30, September 30, Pro forma revenue $ 887.6 $ 684.3 $ 2,460.5 $ 1,939.6 Pro forma net income attributable to Fortinet, Inc. $ 165.1 $ 122.8 $ 407.3 $ 334.8

Goodwill and Other Intangible_2

Goodwill and Other Intangible Assets - Net (Tables)	9 Months Ended
	Sep. 30, 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 Additions due to business combinations 35.2 Foreign currency translation adjustments (0.6) Balance—September 30, 2021 $ 127.6
Schedule of Finite-Lived Intangible Assets by Major Class	The following tables present other intangible assets—net (in millions, except years): September 30, 2021 Weighted-Average Useful Life (in Years) Gross Accumulated Amortization Net Other intangible assets—net: Finite-lived intangible assets: Developed technologies 4.0 $ 89.5 $ 40.8 $ 48.7 Customer relationships 5.7 34.6 23.0 11.6 Trade name 10.0 6.3 0.1 6.2 Backlog 1.0 4.9 $ 0.4 4.5 Total other intangible assets—net $ 135.3 $ 64.3 $ 71.0 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) $ 6.8 2022 22.9 2023 16.3 2024 11.5 2025 6.2 Thereafter 7.3 Total $ 71.0

Net Income Per Share (Tables)

Net Income Per Share (Tables)	9 Months Ended
	Sep. 30, 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 Nine Months Ended September 30, September 30, September 30, September 30, Numerator: Net income including non-controlling interests $ 163.2 $ 123.4 $ 407.9 $ 341.8 Net income attributable to non-controlling interests 0.1 — 0.1 — Net income attributable to Fortinet, Inc. $ 163.1 $ 123.4 $ 407.8 $ 341.8 Denominator: Basic shares: Weighted-average common stock outstanding-basic 163.5 162.1 163.3 164.8 Diluted shares: Weighted-average common stock outstanding-basic 163.5 162.1 163.3 164.8 Effect of potentially dilutive securities: RSUs 2.4 2.3 2.2 2.4 Stock options 1.8 1.2 1.6 1.2 Weighted-average shares used to compute diluted net income per share attributable to Fortinet, Inc. common stockholders 167.7 165.6 167.1 168.4 Net income per share attributable to Fortinet, Inc. common stockholders: Basic $ 1.00 $ 0.76 $ 2.50 $ 2.07 Diluted $ 0.97 $ 0.75 $ 2.44 $ 2.03
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 Nine Months Ended September 30, September 30, September 30, September 30, RSUs 0.1 0.3 0.2 0.3 Stock options — 0.6 0.3 0.5 Total 0.1 0.9 0.5 0.8

Leases (Tables)

Leases (Tables)	9 Months Ended
	Sep. 30, 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 Nine Months Ended September 30, September 30, September 30, September 30, Operating lease expense $ 6.8 $ 4.8 $ 18.9 $ 13.5 Variable lease expense (1) 0.8 0.7 2.3 1.7 Short-term lease expense 1.0 1.0 2.7 2.9 Total lease expense $ 8.6 $ 6.5 $ 23.9 $ 18.1 (1) Variable lease expense for the three and nine months ended September 30, 2021 and 2020 predominantly included common area maintenance charges and parking expense. Supplemental cash flow information related to leases was as follows (in millions): Nine Months Ended September 30, September 30, Cash paid for amounts included in the measurement of lease liabilities Operating cash flows used for operating leases $ 18.8 $ 13.8
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 September 30, December 31, Operating lease ROU assets - non-current Other assets $ 63.6 $ 49.3 Operating lease liabilities - current Accrued liabilities $ 25.0 $ 19.1 Operating lease liabilities - non-current Other liabilities 40.5 34.0 Total operating lease liabilities $ 65.5 $ 53.1 Weighted average remaining lease term in years - operating leases 3.1 3.5 Weighted average discount rate - operating leases 2.2 % 3.2 %
Maturities of Operating Lease Liabilities	Maturities of operating lease liabilities as of September 30, 2021 were as follows (in millions): Year Ending December 31, Amount 2021 (the remainder of 2021) $ 6.8 2022 25.0 2023 18.4 2024 11.8 2025 4.3 Thereafter 1.4 Total lease payments 67.7 Less imputed interest (2.2) Total $ 65.5

Debt (Tables)

Debt (Tables)	9 Months Ended
	Sep. 30, 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 September 30, 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 12.0 Total long-term debt $ 988.0

Commitments and Contingencies (

Commitments and Contingencies (Tables)	9 Months Ended
	Sep. 30, 2021
Commitments and Contingencies Disclosure [Abstract]
Inventory Purchase Commitments, Fiscal Year Maturity Schedule	The following table summarizes our inventory purchase commitments as of September 30, 2021 (in millions): Total 2021 2022 2023 2024 2025 Thereafter Inventory purchase commitments $ 868.0 $ 376.7 $ 491.3 $ — $ — $ — $ —

Equity (Tables)

Equity (Tables)	9 Months Ended
	Sep. 30, 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 1.1 190.47 Forfeited (0.3) 111.20 Vested (1.9) 81.15 Balance—September 30, 2021 3.6 $ 123.67
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 Nine Months Ended September 30, September 30, September 30, September 30, Shares withheld for taxes 0.1 0.2 0.6 0.7 Amount withheld for taxes $ 42.9 $ 27.6 $ 119.0 $ 86.5
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 Nine Months Ended September 30, September 30, September 30, September 30, Expected term in years 4.4 4.4 4.4 4.4 Volatility 36.9 % 39.9 % 39.2 % 34.6 % Risk-free interest rate 0.7 % 0.2 % 0.5 % 1.1 % 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 0.6 179.95 Forfeited (0.1) 117.60 Exercised (0.4) 53.26 Balance—September 30, 2021 2.8 $ 90.20 Options vested and expected to vest—September 30, 2021 2.8 $ 90.20 4.1 $ 567.2 Options exercisable—September 30, 2021 1.6 $ 56.62 3.1 $ 379.9
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 Nine Months Ended September 30, September 30, September 30, September 30, Weighted-average fair value per share granted $ 95.33 $ 43.80 $ 58.69 $ 35.76 Intrinsic value of options exercised $ 20.9 $ 5.5 $ 60.2 $ 35.8 Fair value of options vested $ 3.3 $ 2.5 $ 13.9 $ 10.9
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 Nine Months Ended September 30, September 30, September 30, September 30, Cost of product revenue $ 0.4 $ 0.4 $ 1.3 $ 1.2 Cost of service revenue 4.1 3.3 11.4 9.5 Research and development 14.5 12.7 42.0 35.6 Sales and marketing 27.6 27.7 82.1 81.3 General and administrative 6.9 5.9 20.2 17.3 Total stock-based compensation expense $ 53.5 $ 50.0 $ 157.0 $ 144.9
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 Nine Months Ended September 30, September 30, September 30, September 30, RSUs $ 48.5 $ 46.4 $ 142.8 $ 134.5 Stock options 5.0 3.6 14.2 10.4 Total stock-based compensation expense $ 53.5 $ 50.0 $ 157.0 $ 144.9
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 Nine Months Ended September 30, September 30, September 30, September 30, Income tax benefit associated with stock-based compensation $ 11.7 $ 11.0 $ 34.5 $ 31.9

Segment Information (Tables)

Segment Information (Tables)	9 Months Ended
	Sep. 30, 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 Nine Months Ended Revenue September 30, September 30, September 30, September 30, Americas: United States $ 258.4 $ 206.0 $ 722.6 $ 589.1 Other Americas 91.7 66.4 255.4 186.9 Total Americas 350.1 272.4 978.0 776.0 Europe, Middle East and Africa (“EMEA”) 323.2 243.3 905.1 693.5 Asia Pacific (“APAC”) 193.9 135.4 495.5 376.9 Total revenue $ 867.2 $ 651.1 $ 2,378.6 $ 1,846.4
Property and Equipment by Geographic Region	Property and Equipment — net September 30, December 31, Americas: United States $ 357.1 $ 296.3 Canada 160.9 121.3 Latin America 1.8 2.0 Total Americas 519.8 419.6 EMEA 23.8 20.6 APAC 13.0 7.8 Total property and equipment—net $ 556.6 $ 448.0
Schedule of Distributor Concentration	The following distributors accounted for 10% or more of our revenue: Three Months Ended Nine Months Ended September 30, September 30, September 30, September 30, Exclusive Networks Group (“Exclusive”) 31 % 29 % 32 % 30 % Ingram Micro, Inc. (“Ingram Micro”) 12 % 10 % 12 % 10 % The following distributors accounted for 10% or more of net accounts receivable: September 30, December 31, Exclusive 30 % 34 % TD Synnex 15 % * Ingram Micro 11 % 11 %

Revenue Recognition - Disaggreg

Revenue Recognition - Disaggregated Revenues (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
Disaggregation of Revenue [Line Items]
Total revenue	$ 867.2	$ 651.1	$ 2,378.6	$ 1,846.4
Product [Member]
Disaggregation of Revenue [Line Items]
Total revenue	337.1	223.8	876.1	628
Service [Member]
Disaggregation of Revenue [Line Items]
Total revenue	530.1	427.3	1,502.5	1,218.4
Security Subscription [Member]
Disaggregation of Revenue [Line Items]
Total revenue	287.4	235.4	815.6	669.4
Technical Support and Other [Member]
Disaggregation of Revenue [Line Items]
Total revenue	$ 242.7	$ 191.9	$ 686.9	$ 549

Revenue Recognition (Details)

Revenue Recognition (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020	Dec. 31, 2020
Disaggregation of Revenue [Line Items]
Remaining performance obligation	$ 3,110		$ 3,110
Threshold period past due	60 days		60 days
Allowance for credit losses	$ 2.6		$ 2.6		$ 2.5
Amortization of deferred contract costs	45.1	$ 35.3	126.9	$ 99.8
Service [Member]
Disaggregation of Revenue [Line Items]
Deferred revenue recognized in period	$ 309.2	$ 263.1	$ 1,100	$ 921.7

Revenue Recognition - Performan

Revenue Recognition - Performance Obligation Satisfaction Period (Details) $ in Millions	Sep. 30, 2021USD ($)
Revenue from Contract with Customer [Abstract]
Remaining performance obligation	$ 3,110
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2021-10-01
Revenue from Contract with Customer [Abstract]
Remaining performance obligation	$ 1,620
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]: 2022-10-01
Revenue from Contract with Customer [Abstract]
Remaining performance obligation	$ 1,380
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	Sep. 30, 2021	Dec. 31, 2020
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	$ 1,526.3	$ 892.8
Unrealized Gains	0.3	1
Unrealized Losses	(0.3)	0
Fair Value	1,526.3	893.8
Available-for-sale Securities, Continuous Unrealized Loss Position [Abstract]
Less Than 12 Months, Fair Value	499.1	240.4
Less Than 12 Months, Unrealized Losses	(0.3)	0
12 Months or Greater, Fair Value	0	0
12 Months or Greater, Unrealized Losses	0	0
Total, Fair Value	499.1	240.4
Total, Unrealized Losses	(0.3)	0
Available-for-sale Securities, Debt Maturities, Fair Value [Abstract]
Due within one year	1,228.1	775.5
Due within one to three years	298.2	118.3
Fair Value	1,526.3	893.8
Commercial paper [Member]
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	647	185.4
Unrealized Gains	0.1	0
Unrealized Losses	0	0
Fair Value	647.1	185.4
Available-for-sale Securities, Continuous Unrealized Loss Position [Abstract]
Less Than 12 Months, Fair Value	116.3	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	116.3	61.5
Total, Unrealized Losses	0	0
Available-for-sale Securities, Debt Maturities, Fair Value [Abstract]
Fair Value	647.1	185.4
Corporate debt securities [Member]
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	484.6	410.5
Unrealized Gains	0.2	1
Unrealized Losses	(0.2)	0
Fair Value	484.6	411.5
Available-for-sale Securities, Continuous Unrealized Loss Position [Abstract]
Less Than 12 Months, Fair Value	281	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	281	111.3
Total, Unrealized Losses	(0.2)	0
Available-for-sale Securities, Debt Maturities, Fair Value [Abstract]
Fair Value	484.6	411.5
Certificates of deposit and term deposits [Member]
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	214.5	112
Unrealized Gains	0	0
Unrealized Losses	0	0
Fair Value	214.5	112
Available-for-sale Securities, Continuous Unrealized Loss Position [Abstract]
Less Than 12 Months, Fair Value	15.8	29.5
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	15.8	29.5
Total, Unrealized Losses	0	0
Available-for-sale Securities, Debt Maturities, Fair Value [Abstract]
Fair Value	214.5	112
U.S. government securities [Member]
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	174.7	184.9
Unrealized Gains	0	0
Unrealized Losses	(0.1)	0
Fair Value	174.6	184.9
Available-for-sale Securities, Continuous Unrealized Loss Position [Abstract]
Less Than 12 Months, Fair Value	80.6	38.1
Less Than 12 Months, Unrealized Losses	(0.1)	0
12 Months or Greater, Fair Value	0	0
12 Months or Greater, Unrealized Losses	0	0
Total, Fair Value	80.6	38.1
Total, Unrealized Losses	(0.1)	0
Available-for-sale Securities, Debt Maturities, Fair Value [Abstract]
Fair Value	174.6	$ 184.9
Municipal Bonds [Member]
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	5.5
Unrealized Gains	0
Unrealized Losses	0
Fair Value	5.5
Available-for-sale Securities, Continuous Unrealized Loss Position [Abstract]
Less Than 12 Months, Fair Value	5.4
Less Than 12 Months, Unrealized Losses	0
12 Months or Greater, Fair Value	0
12 Months or Greater, Unrealized Losses	0
Total, Fair Value	5.4
Total, Unrealized Losses	0
Available-for-sale Securities, Debt Maturities, Fair Value [Abstract]
Fair Value	$ 5.5

Financial Instruments and Fai_4

Financial Instruments and Fair Value , Additional Information (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020	Dec. 31, 2020
Financial Instruments and Fair Value [Abstract]
Accrued interest on available-for-sale securities	$ 2.4		$ 2.4
Marketable equity securities	40.8		40.8		$ 0
Recognized gain (loss) on marketable equity securities	$ (3.7)	$ (0.1)	$ (2.9)	$ 0.3

Financial Instruments and Fai_5

Financial Instruments and Fair Value , Fair Value Measurements (Details) - USD ($) $ in Millions	Sep. 30, 2021	Dec. 31, 2020
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value	$ 1,526.3	$ 893.8
Commercial paper [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value	647.1	185.4
Corporate debt securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value	484.6	411.5
Certificates of deposit and term deposits [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value	214.5	112
U.S. government securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value	174.6	184.9
Municipal Bonds [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value	5.5
Recurring Basis [Member] | Fair Value [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total Assets, Fair Value Disclosure	1,603.4	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	237.7	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	1,365.7	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] | Commercial paper [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value	651.1	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	651.1	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] | Corporate debt securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value	484.6	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	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	484.6	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] | Certificates of deposit and term deposits [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value	214.5	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	214.5	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] | U.S. government securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value	174.6	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	164.6	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	10	0
Recurring Basis [Member] | Fair Value [Member] | U.S. government securities [Member] | Level 3 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value	0	0
Recurring Basis [Member] | Fair Value [Member] | Money market funds [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value	32.3	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	32.3	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] | Fair Value [Member] | Municipal Bonds [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value	5.5	0
Recurring Basis [Member] | Fair Value [Member] | Municipal Bonds [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] | Municipal Bonds [Member] | Level 2 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value	5.5	0
Recurring Basis [Member] | Fair Value [Member] | Municipal Bonds [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] | Equity Securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value	40.8	0
Recurring Basis [Member] | Fair Value [Member] | Equity Securities | Level 1 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value	40.8	0
Recurring Basis [Member] | Fair Value [Member] | Equity Securities | 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] | Equity Securities | 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	1,603.4	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	36.3	166.7
Recurring Basis [Member] | Reported as [Member] | Equity Securities, Line Item [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value	40.8	0
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	1,228.1	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	$ 298.2	$ 118.3

Inventory (Details)

Inventory (Details) - USD ($) $ in Millions	Sep. 30, 2021	Dec. 31, 2020
Inventory, Net [Abstract]
Raw materials	$ 35.6	$ 13.8
Work in process	7.9	0
Finished goods	134.4	126
Inventory	$ 177.9	$ 139.8

Property and Equipment_Net (Det

Property and Equipment—Net (Details) - USD ($) $ in Millions	1 Months Ended	3 Months Ended		9 Months Ended
	Sep. 30, 2021	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020	Dec. 31, 2020
Property, Plant and Equipment, Net, by Type [Abstract]
Total property and equipment	$ 762.6	$ 762.6		$ 762.6		$ 620.5
Less: accumulated depreciation	(206)	(206)		(206)		(172.5)
Property and equipment—net	556.6	556.6		556.6		448
Purchase of property and equipment				144.6	$ 93.6
Depreciation expense		18.1	$ 13.9	47.4	$ 41.6
Canada [Member]
Property, Plant and Equipment, Net, by Type [Abstract]
Property and equipment—net	160.9	160.9		160.9		121.3
Purchase of property and equipment	37.7
Land [Member]
Property, Plant and Equipment, Net, by Type [Abstract]
Total property and equipment	128.3	128.3		128.3		93.3
Land [Member] | Canada [Member]
Property, Plant and Equipment, Net, by Type [Abstract]
Total property and equipment	16.6	16.6		16.6
Building and building improvements [Member]
Property, Plant and Equipment, Net, by Type [Abstract]
Total property and equipment	365.4	365.4		365.4		150.6
Building and building improvements [Member] | Canada [Member]
Property, Plant and Equipment, Net, by Type [Abstract]
Total property and equipment	21.1	21.1		21.1
Computer equipment and software [Member]
Property, Plant and Equipment, Net, by Type [Abstract]
Total property and equipment	166.4	166.4		166.4		137.2
Leasehold improvements [Member]
Property, Plant and Equipment, Net, by Type [Abstract]
Total property and equipment	38.8	38.8		38.8		31.9
Evaluation units [Member]
Property, Plant and Equipment, Net, by Type [Abstract]
Total property and equipment	19.8	19.8		19.8		19.8
Furniture and fixtures [Member]
Property, Plant and Equipment, Net, by Type [Abstract]
Total property and equipment	27	27		27		21.3
Construction-in-progress [Member]
Property, Plant and Equipment, Net, by Type [Abstract]
Total property and equipment	$ 16.9	$ 16.9		$ 16.9		$ 166.4

Investments in Privately-Held_2

Investments in Privately-Held Companies (Details) - USD ($) $ in Millions	Sep. 24, 2021	Mar. 19, 2021	Sep. 30, 2021	Sep. 30, 2020	Dec. 31, 2020
Schedule of Equity Method Investments [Line Items]
Cash investment in privately held company			$ 160	$ 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	$ 85	$ 75
Ownership interest percentage		32.60%	50.80%

Business Combinations - Additio

Business Combinations - Additional Information (Details) - USD ($)	Aug. 31, 2021	Mar. 10, 2021	Sep. 30, 2021	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020	Dec. 31, 2020
Business Acquisition [Line Items]
Total revenue				$ 867,200,000	$ 651,100,000	$ 2,378,600,000	$ 1,846,400,000
Goodwill			$ 127,600,000	$ 127,600,000		$ 127,600,000		$ 93,000,000
AlaxaIA
Business Acquisition [Line Items]
Equity interests acquired	75.00%
Cash consideration	$ 64,200,000
Non-controlling interests	17,800,000
Total revenue			$ 15,600,000
Goodwill	29,000,000
Other intangible assets	$ 48,000,000
ShieldX Networks Inc (ShieldX)
Business Acquisition [Line Items]
Cash consideration		$ 10,800,000
Goodwill		6,200,000
Other net assets acquired		500,000
ShieldX Networks Inc (ShieldX) | Developed technology
Business Acquisition [Line Items]
Other intangible assets		$ 4,100,000

Business Combinations - Schedul

Business Combinations - Schedule of Recognized Identified Assets Acquired and Liabilities Assumed (Details) - USD ($) $ in Millions	Sep. 30, 2021	Aug. 31, 2021	Dec. 31, 2020
ASSETS
Goodwill	$ 127.6		$ 93
AlaxaIA
ASSETS
Cash		$ 1.1
Accounts receivable—net		15.6
Inventory		33.4
Prepaid expenses and other current assets		2.9
Property and equipment		5.3
Goodwill		29
Other intangible assets		48
Other long-term assets		2.7
TOTAL ASSETS		138
LIABILITIES
Accounts payable		11
Current portion of long-term debt		20.2
Accrued and other current liabilities		14.7
Other long-term liabilities		10.1
TOTAL LIABILITIES		56
NON-CONTROLLING INTERESTS		17.8
Net purchase consideration		$ 64.2

Business Combinations -Schedule

Business Combinations -Schedule of Acquired Finite-Lived Intangible Assets (Details) - USD ($) $ in Millions	Aug. 31, 2021	Sep. 30, 2021	Dec. 31, 2020
Developed technology
Business Acquisition [Line Items]
Estimated Useful Life (in years)		4 years	4 years
Customer relationships
Business Acquisition [Line Items]
Estimated Useful Life (in years)		5 years 8 months 12 days	4 years
Trade name
Business Acquisition [Line Items]
Estimated Useful Life (in years)		10 years
Backlog
Business Acquisition [Line Items]
Estimated Useful Life (in years)		1 year
AlaxaIA
Business Acquisition [Line Items]
Total identified intangible assets:	$ 48
AlaxaIA | Developed technology
Business Acquisition [Line Items]
Fair Value	$ 26.6
Estimated Useful Life (in years)	4 years
AlaxaIA | Customer relationships
Business Acquisition [Line Items]
Fair Value	$ 10
Estimated Useful Life (in years)	10 years
AlaxaIA | Trade name
Business Acquisition [Line Items]
Fair Value	$ 6.4
Estimated Useful Life (in years)	10 years
AlaxaIA | Backlog
Business Acquisition [Line Items]
Fair Value	$ 5
Estimated Useful Life (in years)	1 year

Business Combinations - Pro For

Business Combinations - Pro Forma Information (Details) - AlaxaIA - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
Business Acquisition [Line Items]
Pro forma revenue	$ 887.6	$ 684.3	$ 2,460.5	$ 1,939.6
Pro forma net income attributable to Fortinet, Inc.	$ 165.1	$ 122.8	$ 407.3	$ 334.8

Goodwill and Other Intangible_3

Goodwill and Other Intangible Assets - Net - Changes in Carrying Amount of Goodwill (Details) $ in Millions	9 Months Ended
	Sep. 30, 2021USD ($)
Goodwill [Roll Forward]
Balance - beginning of period	$ 93
Additions due to business combinations	35.2
Foreign currency translation adjustments	(0.6)
Balance - end of period	$ 127.6

Goodwill and Other Intangible_4

Goodwill and Other Intangible Assets - Net - Narrative (Details) - USD ($)	3 Months Ended		9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
Goodwill and Intangible Assets Disclosure [Abstract]
Goodwill impairment			$ 0	$ 0
Amortization expense	$ 4,800,000	$ 2,800,000	$ 11,700,000	$ 10,500,000

Goodwill and Other Intangible_5

Goodwill and Other Intangible Assets - Net - Other Intangible Assets, Net (Details) - USD ($) $ in Millions	9 Months Ended	12 Months Ended
	Sep. 30, 2021	Dec. 31, 2020
Finite-Lived Intangible Assets, Net [Abstract]
Gross	$ 135.3	$ 84.1
Accumulated Amortization	64.3	52.5
Total	$ 71	$ 31.6
Developed technology
Finite-Lived Intangible Assets [Line Items]
Estimated Useful Life (in years)	4 years	4 years
Finite-Lived Intangible Assets, Net [Abstract]
Gross	$ 89.5	$ 59.3
Accumulated Amortization	40.8	32.3
Total	$ 48.7	$ 27
Customer relationships
Finite-Lived Intangible Assets [Line Items]
Estimated Useful Life (in years)	5 years 8 months 12 days	4 years
Finite-Lived Intangible Assets, Net [Abstract]
Gross	$ 34.6	$ 24.8
Accumulated Amortization	23	20.2
Total	$ 11.6	$ 4.6
Trade name
Finite-Lived Intangible Assets [Line Items]
Estimated Useful Life (in years)	10 years
Finite-Lived Intangible Assets, Net [Abstract]
Gross	$ 6.3
Accumulated Amortization	0.1
Total	$ 6.2
Backlog
Finite-Lived Intangible Assets [Line Items]
Estimated Useful Life (in years)	1 year
Finite-Lived Intangible Assets, Net [Abstract]
Gross	$ 4.9
Accumulated Amortization	0.4
Total	$ 4.5

Goodwill and Other Intangible_6

Goodwill and Other Intangible Assets - Net - Estimated Future Amortization Expense (Details) - USD ($) $ in Millions	Sep. 30, 2021	Dec. 31, 2020
Fiscal Years:
2021 (the remainder of 2021)	$ 6.8
2022	22.9
2023	16.3
2024	11.5
2025	6.2
Thereafter	7.3
Total	$ 71	$ 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		9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
Earnings Per Share [Line Items]
Net income	$ 163.1	$ 123.4	$ 407.8	$ 341.8
Basic shares:
Weighted-average common shares outstanding-basic (in shares)	163.5	162.1	163.3	164.8
Diluted shares:
Weighted-average common shares outstanding-basic (in shares)	163.5	162.1	163.3	164.8
Effect of potentially dilutive securities:
Weighted-average shares used to compute diluted net income per share (in shares)	167.7	165.6	167.1	168.4
Net income per share attributable to Fortinet, Inc. common stockholders:
Basic (in dollars per share)	$ 1	$ 0.76	$ 2.50	$ 2.07
Diluted (in dollars per share)	$ 0.97	$ 0.75	$ 2.44	$ 2.03
Restricted Stock Units (RSUs) [Member]
Effect of potentially dilutive securities:
RSUs and stock options (in shares)	2.4	2.3	2.2	2.4
Stock Options [Member]
Effect of potentially dilutive securities:
RSUs and stock options (in shares)	1.8	1.2	1.6	1.2

Net Income Per Share , Anti Dil

Net Income Per Share , Anti Dilutive Securities (Details) - shares shares in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Anti-dilutive securities (in shares)	0.1	0.9	0.5	0.8
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)	0.1	0.3	0.2	0.3
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	0.6	0.3	0.5

Leases (Details)

Leases (Details) - USD ($) $ in Millions	9 Months Ended	12 Months Ended
	Sep. 30, 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	$ 7.7
Minimum [Member]
Lessee, Lease, Description [Line Items]
Remaining terms (less than for minimum)	1 year
Lease not yet commenced, approximate term	2 years
Maximum [Member]
Lessee, Lease, Description [Line Items]
Remaining terms (less than for minimum)	6 years
Lease not yet commenced, approximate term	5 years

Leases - Components of Lease Ex

Leases - Components of Lease Expense (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
Leases [Abstract]
Operating lease expense	$ 6.8	$ 4.8	$ 18.9	$ 13.5
Variable lease expense	0.8	0.7	2.3	1.7
Short-term lease expense	1	1	2.7	2.9
Total lease expense	$ 8.6	$ 6.5	$ 23.9	$ 18.1

Leases - Supplemental Balance S

Leases - Supplemental Balance Sheet Information (Details) - USD ($) $ in Millions	Sep. 30, 2021	Dec. 31, 2020
Leases [Abstract]
Operating Lease, Right-of-Use Asset, Statement of Financial Position [Extensible List]	OTHER ASSETS	OTHER ASSETS
Operating lease ROU assets - non-current	$ 63.6	$ 49.3
Operating Lease, Liability, Current, Statement of Financial Position [Extensible List]	Accrued liabilities	Accrued liabilities
Operating lease liabilities - current	$ 25	$ 19.1
Operating Lease, Liability, Noncurrent, Statement of Financial Position [Extensible List]	OTHER LIABILITIES	OTHER LIABILITIES
Operating lease liabilities - non-current	$ 40.5	$ 34
Total operating lease liabilities	$ 65.5	$ 53.1
Weighted average remaining lease term in years - operating leases	3 years 1 month 6 days	3 years 6 months
Weighted average discount rate - operating leases	2.20%	3.20%

Leases - Supplemental Cash Flow

Leases - Supplemental Cash Flow Information (Details) - USD ($) $ in Millions	9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020
Cash paid for amounts included in the measurement of lease liabilities
Operating cash flows used for operating leases	$ 18.8	$ 13.8

Leases - Maturities of Operatin

Leases - Maturities of Operating Lease Liabilities (Details) - USD ($) $ in Millions	Sep. 30, 2021	Dec. 31, 2020
Leases [Abstract]
2021 (the remainder of 2021)	$ 6.8
2022	25
2023	18.4
2024	11.8
2025	4.3
Thereafter	1.4
Total lease payments	67.7
Less imputed interest	(2.2)
Total	$ 65.5	$ 53.1

Debt - Narrative (Details)

Debt - Narrative (Details) - USD ($)	3 Months Ended	9 Months Ended
	Sep. 30, 2021	Sep. 30, 2021	Aug. 31, 2021	Mar. 05, 2021	Dec. 31, 2020
Debt Instrument [Line Items]
Current portion of long-term debt	$ 17,600,000	$ 17,600,000			$ 0
AlaxaIA
Debt Instrument [Line Items]
Current portion of long-term debt assumed			$ 20,200,000
Senior Notes [Member]
Debt Instrument [Line Items]
Aggregate principal amount				$ 1,000,000,000
Accrued interest payable	700,000	700,000
Interest expense	4,400,000	10,200,000
Interest costs capitalized	0	0
Senior Notes [Member] | Level 2 [Member]
Debt Instrument [Line Items]
Estimated fair value of outstanding debt	$ 991,100,000	$ 991,100,000
Senior Notes [Member] | 2026 Senior Notes [Member]
Debt Instrument [Line Items]
Aggregate principal amount				$ 500,000,000
Stated interest rate	1.00%	1.00%		1.00%
Senior Notes [Member] | 2031 Senior Notes [Member]
Debt Instrument [Line Items]
Aggregate principal amount				$ 500,000,000
Stated interest rate	2.20%	2.20%		2.20%

Debt - Summary of Outstanding D

Debt - Summary of Outstanding Debt (Details) - USD ($) $ in Millions	Sep. 30, 2021	Mar. 05, 2021	Dec. 31, 2020
Debt Instrument [Line Items]
Total debt	$ 1,000
Less: Unamortized discount and debt issuance costs	12
LONG-TERM DEBT	$ 988		$ 0
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		9 Months Ended
	Jan. 31, 2020	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020	Dec. 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	$ 1,100,000	$ 3,400,000	$ 39,000,000
Amount recorded in Accrued liabilities and Other liabilities in condensed consolidated balance sheet		$ 6,400,000		$ 6,400,000		$ 9,800,000

Commitments and Contingencies -

Commitments and Contingencies - Inventory Purchase Commitments (Details) $ in Millions	Sep. 30, 2021USD ($)
Inventory purchase commitments:
Inventory purchase commitments	$ 868
Inventory purchase commitments, 2021	376.7
Inventory purchase commitments, 2022	491.3
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	Sep. 30, 2021USD ($)
Commitments and Contingencies Disclosure [Abstract]
Inventory purchase commitments	$ 868
Other contractual commitments and open purchase orders	68.9
Loss contingency accrual	$ 5

Equity , Restricted Stock Units

Equity , Restricted Stock Units Activity (Details) - USD ($) $ / shares in Units, shares in Millions, $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
Weighted-Average Grant Date Fair Value per Share
Shares withheld for taxes	0.1	0.2	0.6	0.7
Amount withheld for taxes	$ 42.9	$ 27.6	$ 119	$ 86.5
Stock-based Compensation Plan [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Remaining shares available for grant under the plans	11.7		11.7
Restricted Stock Units (RSUs) [Member]
Number of Shares
Balance, beginning (shares)			4.7
Granted (shares)			1.1
Forfeited (shares)			(0.3)
Vested (shares)			(1.9)
Balance, ending (shares)	3.6		3.6
Weighted-Average Grant Date Fair Value per Share
Balance, beginning (in dollars per share)			$ 90.46
Granted (in dollars per share)			190.47
Forfeited (in dollars per share)			111.20
Vested (in dollars per share)			81.15
Balance, ending (in dollars per share)	$ 123.67		$ 123.67
Compensation cost not yet recognized	$ 391.2		$ 391.2
Compensation cost not yet recognized period of recognition			2 years 8 months 12 days

Equity - Employee Stock Options

Equity - Employee Stock Options (Details) - Stock Options [Member] - USD ($) $ / shares in Units, shares in Millions, $ in Millions	3 Months Ended		9 Months Ended		12 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 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	4 years 4 months 24 days	4 years 4 months 24 days
Volatility	36.90%	39.90%	39.20%	34.60%
Risk-free interest rate	0.70%	0.20%	0.50%	1.10%
Dividend rate	0.00%	0.00%	0.00%	0.00%
Number of Shares
Balance - Beginning (in shares)			2.7
Granted (in shares)			0.6
Forfeited (in shares)			(0.1)
Exercised (in shares)			(0.4)
Balance - Ending (in shares)	2.8		2.8		2.7
Weighted- Average Exercise Price
Balance - Beginning (in dollars per share)			$ 67.53
Granted (in dollars per share)			179.95
Forfeited (in dollars per share)			117.60
Exercised (in dollars per share)			53.26
Balance - Ending (in dollars per share)	$ 90.20		$ 90.20		$ 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)	2.8		2.8
Options vested and expected to vest, Weighted average exercise price (in dollars per share)	$ 90.20		$ 90.20
Options vested and expected to vest, Weighted average remaining contractual life (in years)			4 years 1 month 6 days
Options vested and expected to vest, Aggregate intrinsic value	$ 567.2		$ 567.2
Options exercisable, Outstanding (in shares)	1.6		1.6
Options exercisable, Weighted average exercise price (in dollars per share)	$ 56.62		$ 56.62
Options exercisable, Weighted average remaining contractual life (in years)			3 years 1 month 6 days
Options exercisable, Aggregate intrinsic value	$ 379.9		$ 379.9
Compensation cost not yet recognized	$ 46.6		$ 46.6
Compensation cost not yet recognized period of recognition			2 years 10 months 24 days
Weighted-average fair value per share granted	$ 95.33	$ 43.80	$ 58.69	$ 35.76
Intrinsic value of options exercised	$ 20.9	$ 5.5	$ 60.2	$ 35.8
Fair value of options vested	$ 3.3	$ 2.5	$ 13.9	$ 10.9

Equity , Allocation of Stock-Ba

Equity , Allocation of Stock-Based Compensation Expense (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]
Total stock-based compensation expense	$ 53.5	$ 50	$ 157	$ 144.9
Income tax benefit associated with stock-based compensation	11.7	11	34.5	31.9
Restricted Stock Units (RSUs) [Member]
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]
Total stock-based compensation expense	48.5	46.4	142.8	134.5
Stock Options [Member]
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]
Total stock-based compensation expense	5	3.6	14.2	10.4
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	1.3	1.2
Cost of service revenue [Member]
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]
Total stock-based compensation expense	4.1	3.3	11.4	9.5
Research and development [Member]
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]
Total stock-based compensation expense	14.5	12.7	42	35.6
Sales and marketing [Member]
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]
Total stock-based compensation expense	27.6	27.7	82.1	81.3
General and administrative [Member]
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]
Total stock-based compensation expense	$ 6.9	$ 5.9	$ 20.2	$ 17.3

Equity , Share Repurchase Progr

Equity , Share Repurchase Program (Details) - Repurchase Program [Member] - USD ($) $ / shares in Units, shares in Millions	1 Months Ended		3 Months Ended	9 Months Ended
	Oct. 31, 2021	Jul. 31, 2020	Sep. 30, 2021	Sep. 30, 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 shares)			0.3	0.8
Stock repurchased, average price (in dollars per share)			$ 294.07	$ 242.95
Stock repurchased			$ 108,800,000	$ 200,400,000
Stock repurchase program, unused balance			$ 812,300,000	$ 812,300,000
Subsequent Event
Share Repurchase Program [Line Items]
Increase in authorized stock repurchase amount	$ 1,250,000,000
Stock repurchase program, authorized amount	$ 4,250,000,000

Income Taxes , Narrative (Detai

Income Taxes , Narrative (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020	Dec. 31, 2020
Income Tax Disclosure [Abstract]
Effective tax rate (percent)	6.00%	4.00%	2.00%	8.00%
U.S. federal and state taxes, withholding taxes and foreign taxes	$ 40.1	$ 33.8	$ 115.8	$ 100.7
Tax benefit from foreign-derived intangible income deduction	8.7	16.3	23.9	25.9
Excess tax benefits on stock compensation	25	$ 12.5	60.3	37.6
Tax benefit from change in tax accounting position	15.7		15.7
Release of reserves on uncertain tax positions and interest due			5.5	$ 9
Unrecognized tax benefits	80.7		80.7		$ 77.3
Unrecognized tax benefits that would favorably affect effective tax rate	73.3		73.3
Accrued interest and penalties related to uncertain tax benefits	16.2		16.2		$ 14.5
Possible decrease in unrecognized tax benefits (up to)	$ 27.3		$ 27.3

Defined Contribution Plans (Det

Defined Contribution Plans (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 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	$ 2.5	$ 2.1	$ 7.9	$ 6.5

Segment Information (Details)

Segment Information (Details) $ in Millions	3 Months Ended		9 Months Ended		12 Months Ended
	Sep. 30, 2021USD ($)	Sep. 30, 2020USD ($)	Sep. 30, 2021USD ($)segment_managerbusiness_activityreportable_segmentoperating_segment	Sep. 30, 2020USD ($)	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_manager			0
Number of operating segments (in operating segments) | operating_segment			1
Number of reportable segments (in reportable segments) | reportable_segment			1
Total revenue	$ 867.2	$ 651.1	$ 2,378.6	$ 1,846.4
Property and equipment - net	$ 556.6		$ 556.6		$ 448
Exclusive Networks Group (Exclusive) [Member] | Customer Concentration Risk [Member] | Revenue [Member]
Segment Reporting Information [Line Items]
Concentration (percent)	31.00%	29.00%	32.00%	30.00%
Exclusive Networks Group (Exclusive) [Member] | Customer Concentration Risk [Member] | Accounts Receivable [Member]
Segment Reporting Information [Line Items]
Concentration (percent)			30.00%		34.00%
TD Synnex [Member] | Customer Concentration Risk [Member] | Accounts Receivable [Member]
Segment Reporting Information [Line Items]
Concentration (percent)			15.00%
Ingram Micro, Inc. (Ingram Micro) [Member] | Customer Concentration Risk [Member] | Revenue [Member]
Segment Reporting Information [Line Items]
Concentration (percent)	12.00%	10.00%	12.00%	10.00%
Ingram Micro, Inc. (Ingram Micro) [Member] | Customer Concentration Risk [Member] | Accounts Receivable [Member]
Segment Reporting Information [Line Items]
Concentration (percent)			11.00%		11.00%
Americas [Member]
Segment Reporting Information [Line Items]
Total revenue	$ 350.1	$ 272.4	$ 978	$ 776
Property and equipment - net	519.8		519.8		$ 419.6
U.S. [Member]
Segment Reporting Information [Line Items]
Total revenue	258.4	206	722.6	589.1
Property and equipment - net	357.1		357.1		296.3
Canada [Member]
Segment Reporting Information [Line Items]
Property and equipment - net	160.9		160.9		121.3
Latin America [Member]
Segment Reporting Information [Line Items]
Property and equipment - net	1.8		1.8		2
Other Americas [Member]
Segment Reporting Information [Line Items]
Total revenue	91.7	66.4	255.4	186.9
EMEA [Member]
Segment Reporting Information [Line Items]
Total revenue	323.2	243.3	905.1	693.5
Property and equipment - net	23.8		23.8		20.6
APAC [Member]
Segment Reporting Information [Line Items]
Total revenue	193.9	$ 135.4	495.5	$ 376.9
Property and equipment - net	$ 13		$ 13		$ 7.8

Subsequent Events (Details)

Subsequent Events (Details) ft² in Thousands	1 Months Ended		9 Months Ended
	Oct. 31, 2021USD ($)ft²	Jul. 31, 2020USD ($)	Sep. 30, 2021USD ($)	Sep. 30, 2020USD ($)
Subsequent Event [Line Items]
Payments of debt assumed in connection with business combination			$ 2,200,000	$ 4,100,000
Purchase of property and equipment			$ 144,600,000	$ 93,600,000
Share Repurchase Program [Member]
Subsequent Event [Line Items]
Increase in authorized stock repurchase amount		$ 500,000,000
Stock repurchase program, authorized amount		$ 3,000,000,000
Subsequent Event
Subsequent Event [Line Items]
Square feet purchased | ft²	87
Purchase of property and equipment	$ 22,500,000
Subsequent Event | Share Repurchase Program [Member]
Subsequent Event [Line Items]
Increase in authorized stock repurchase amount	1,250,000,000
Stock repurchase program, authorized amount	4,250,000,000
Subsequent Event | AlaxaIA
Subsequent Event [Line Items]
Payments of debt assumed in connection with business combination	$ 17,600,000