Fortinet (FTNT) 10-Q 6 Nov 20 2020 Q3 Quarterly report Financial data

Document and Entity Information

Document and Entity Information - shares	9 Months Ended
	Sep. 30, 2020	Oct. 30, 2020
Cover [Abstract]
Document Type	10-Q
Document Quarterly Report	true
Document Period End Date	Sep. 30, 2020
Document Transition Report	false
Entity File Number	001-34511
Entity Registrant Name	FORTINET, INC.
Entity Incorporation, State or Country Code	DE
Entity Tax Identification Number	77-0560389
Entity Address, Address Line One	899 Kifer Road
Entity Address, City or Town	Sunnyvale
Entity Address, State or Province	CA
Entity Address, Postal Zip Code	94086
City Area Code	408
Local Phone Number	235-7700
Title of 12(b) Security	Common Stock, $0.001 Par Value
Trading Symbol	FTNT
Security Exchange Name	NASDAQ
Entity Current Reporting Status	Yes
Entity Interactive Data Current	Yes
Entity Filer Category	Large Accelerated Filer
Entity Small Business	false
Entity Emerging Growth Company	false
Entity Shell Company	false
Entity Common Stock, Shares Outstanding		162,332,075
Entity Central Index Key	0001262039
Amendment Flag	false
Document Fiscal Year Focus	2020
Document Fiscal Period Focus	Q3
Current Fiscal Year End Date	--12-31

Condensed Consolidated Balance

Condensed Consolidated Balance Sheets - USD ($) $ in Millions	Sep. 30, 2020	Dec. 31, 2019
CURRENT ASSETS:
Cash and cash equivalents	$ 882.3	$ 1,222.5
Short-term investments	774.4	843.1
Accounts receivable—net	546.6	544.3
Inventory	134.5	117.9
Prepaid expenses and other current assets	46.8	41.2
Total current assets	2,384.6	2,769
LONG-TERM INVESTMENTS	117.9	144.3
PROPERTY AND EQUIPMENT—NET	419.4	344.3
DEFERRED CONTRACT COSTS	281.1	237
DEFERRED TAX ASSETS	230.1	226.3
GOODWILL	68.2	67.2
OTHER INTANGIBLE ASSETS—NET	25.3	31.1
OTHER ASSETS	59.6	60
TOTAL ASSETS	3,586.2	3,879.2
CURRENT LIABILITIES:
Accounts payable	95.9	96.4
Accrued liabilities	127.8	101.8
Accrued payroll and compensation	121.9	101.8
Deferred revenue	1,300	1,155.8
Total current liabilities	1,645.6	1,455.8
DEFERRED REVENUE	1,092	953.3
INCOME TAX LIABILITIES	79.3	82.8
OTHER LIABILITIES	56.1	44.9
Total liabilities	2,873	2,536.8
COMMITMENTS AND CONTINGENCIES (Note 13)
STOCKHOLDERS’ EQUITY:
Common stock, $0.001 par value—300 shares authorized; 162.3 and 171.7 shares issued and outstanding at September 30, 2020 and December 31, 2019, respectively	0.2	0.2
Additional paid-in capital	1,178.5	1,180.3
Accumulated other comprehensive income	1.4	1.1
Retained earnings (accumulated deficit)	(466.9)	160.8
Total stockholders’ equity	713.2	1,342.4
TOTAL LIABILITIES AND STOCKHOLDERS’ EQUITY	$ 3,586.2	$ 3,879.2

Condensed Consolidated Balanc_2

Condensed Consolidated Balance Sheets Parenthetical - $ / shares	Sep. 30, 2020	Dec. 31, 2019
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	162,300,000	171,700,000
Common Stock, shares outstanding	162,300,000	171,700,000

Condensed Consolidated Statemen

Condensed Consolidated Statements of Income - USD ($) shares in Millions, $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
REVENUE:
Total revenue	$ 651.1	$ 548.1	$ 1,846.4	$ 1,544.9
COST OF REVENUE:
Total cost of revenue	139.2	124.1	403	365.4
GROSS PROFIT:
Total gross profit	511.9	424	1,443.4	1,179.5
OPERATING EXPENSES:
Research and development	90	69.9	252.4	205.9
Sales and marketing	266.7	227.4	780.5	669.8
General and administrative	29.4	26.1	87.1	74.9
Gain on intellectual property matter	(1.1)	0	(39)	0
Total operating expenses	385	323.4	1,081	950.6
OPERATING INCOME	126.9	100.6	362.4	228.9
INTEREST INCOME—NET	2.5	11.4	15.7	32.6
OTHER EXPENSE—NET	(1)	(6)	(8.1)	(6.9)
INCOME BEFORE INCOME TAXES	128.4	106	370	254.6
PROVISION FOR INCOME TAXES	5	25.8	28.2	41.1
NET INCOME	$ 123.4	$ 80.2	$ 341.8	$ 213.5
Net income per share (Note 10):
Basic (in dollars per share)	$ 0.76	$ 0.47	$ 2.07	$ 1.25
Diluted (in dollars per share)	$ 0.75	$ 0.46	$ 2.03	$ 1.22
Weighted-average shares outstanding:
Basic (in shares)	162.1	171.3	164.8	170.9
Diluted (in shares)	165.6	174.8	168.4	174.9
Product [Member]
REVENUE:
Total revenue	$ 223.8	$ 197.1	$ 628	$ 549.7
COST OF REVENUE:
Total cost of revenue	84.3	79	245	231.9
GROSS PROFIT:
Total gross profit	139.5	118.1	383	317.8
Service [Member]
REVENUE:
Total revenue	427.3	351	1,218.4	995.2
COST OF REVENUE:
Total cost of revenue	54.9	45.1	158	133.5
GROSS PROFIT:
Total gross profit	$ 372.4	$ 305.9	$ 1,060.4	$ 861.7

Condensed Consolidated Statem_2

Condensed Consolidated Statements of Comprehensive Income - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Statement of Comprehensive Income [Abstract]
Net income	$ 123.4	$ 80.2	$ 341.8	$ 213.5
Other comprehensive income (loss):
Change in unrealized gains (losses) on investments	(1.4)	0.2	0.7	2.7
Less: tax provision (benefit) related to change in unrealized gains (losses) on investments	(0.3)	0	0.4	0.7
Other comprehensive income (loss)	(1.1)	0.2	0.3	2
Comprehensive income	$ 122.3	$ 80.4	$ 342.1	$ 215.5

Condensed Consolidated Statem_3

Condensed Consolidated Statements of Stockholders' Equity - USD ($) shares in Millions, $ in Millions	Total	Cumulative-effect adjustment from adoption of ASU 2018-02	Common Stock [Member]	Additional Paid-in Capital [Member]	Accumulated Other Comprehensive Income (Loss) [Member]	Accumulated Other Comprehensive Income (Loss) [Member]Cumulative-effect adjustment from adoption of ASU 2018-02	Retained Earnings (Accumulated Deficit) [Member]	Retained Earnings (Accumulated Deficit) [Member]Cumulative-effect adjustment from adoption of ASU 2018-02
Balance, shares at Dec. 31, 2018			169.8
Balance at Dec. 31, 2018	$ 1,025.5	$ 0	$ 0.2	$ 1,068.3	$ (0.8)	$ (0.1)	$ (42.2)	$ 0.1
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Issuance of common stock in connection with equity incentive plans - net of tax withholding (in shares)			3.1
Issuance of common stock in connection with equity incentive plans - net of tax withholding	(36.1)			(36.1)
Repurchase and retirement of common stock (in shares)			(1.6)
Repurchase and retirement of common stock	(117.4)			(10)			(107.4)
Stock-based compensation expense	130.4			130.4
Net unrealized gain (loss) on investments - net of tax	2				2
Net income	213.5						213.5
Balance, shares at Sep. 30, 2019			171.3
Balance at Sep. 30, 2019	1,217.9		$ 0.2	1,152.6	1.1		64
Balance, shares at Jun. 30, 2019			171
Balance at Jun. 30, 2019	1,139.4		$ 0.2	1,130.2	0.9		8.1
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Issuance of common stock in connection with equity incentive plans - net of tax withholding (in shares)			0.6
Issuance of common stock in connection with equity incentive plans - net of tax withholding	(17.8)			(17.8)
Repurchase and retirement of common stock (in shares)			(0.3)
Repurchase and retirement of common stock	(26.5)			(2.2)			(24.3)
Stock-based compensation expense	42.4			42.4
Net unrealized gain (loss) on investments - net of tax	0.2				0.2
Net income	80.2						80.2
Balance, shares at Sep. 30, 2019			171.3
Balance at Sep. 30, 2019	1,217.9		$ 0.2	1,152.6	1.1		64
Balance, shares at Dec. 31, 2019			171.7
Balance at Dec. 31, 2019	1,342.4		$ 0.2	1,180.3	1.1		160.8
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Issuance of common stock in connection with equity incentive plans - net of tax withholding (in shares)			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 (loss) on investments - net of tax	0.3				0.3
Net income	341.8						341.8
Balance, shares at Sep. 30, 2020			162.3
Balance at Sep. 30, 2020	713.2		$ 0.2	1,178.5	1.4		(466.9)
Balance, shares at Jun. 30, 2020			161.8
Balance at Jun. 30, 2020	566.7		$ 0.2	1,154.3	2.5		(590.3)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Issuance of common stock in connection with equity incentive plans - net of tax withholding (in shares)			0.5
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 (loss) on investments - net of tax	(1.1)				(1.1)
Net income	123.4						123.4
Balance, shares at Sep. 30, 2020			162.3
Balance at Sep. 30, 2020	$ 713.2		$ 0.2	$ 1,178.5	$ 1.4		$ (466.9)

Condensed Consolidated Statem_4

Condensed Consolidated Statements of Stockholders' Equity (Parenthetical)	12 Months Ended
	Dec. 31, 2018
Statement of Stockholders' Equity [Abstract]
Accounting Standards Update [Extensible List]	us-gaap:AccountingStandardsUpdate201802Member

Condensed Consolidated Statem_5

Condensed Consolidated Statements of Cash Flows - USD ($) $ in Millions	9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019
CASH FLOWS FROM OPERATING ACTIVITIES:
Net income	$ 341.8	$ 213.5
Adjustments to reconcile net income to net cash provided by operating activities:
Stock-based compensation	143	130.4
Amortization of deferred contract costs	99.8	78.5
Depreciation and amortization	52.1	45.9
Amortization of investment premiums (discounts)	0.2	(4.7)
Other	5.8	5
Changes in operating assets and liabilities:
Accounts receivable—net	(3.1)	60.5
Inventory	(31)	(25.2)
Prepaid expenses and other current assets	(4.6)	(6.3)
Deferred contract costs	(143.9)	(113.1)
Deferred tax assets	4.4	11.5
Other assets	(2)	(0.8)
Accounts payable	(4.2)	(6.2)
Accrued liabilities	16.5	(16.6)
Accrued payroll and compensation	19.5	(9.5)
Other liabilities	10.3	(1)
Deferred revenue	282.6	255.7
Net cash provided by operating activities	787.2	617.6
CASH FLOWS FROM INVESTING ACTIVITIES:
Purchases of investments	(776.3)	(1,072.4)
Sales of investments	141.4	19.7
Maturities of investments	730.3	695
Purchases of property and equipment	(93.6)	(45)
Payments made in connection with business combination, net of cash acquired	(9.2)	0
Other	(0.4)	0
Net cash used in investing activities	(7.8)	(402.7)
CASH FLOWS FROM FINANCING ACTIVITIES:
Repurchase and retirement of common stock	(1,046)	(117.6)
Proceeds from issuance of common stock	18.2	41.8
Taxes paid related to net share settlement of equity awards	(86.5)	(76)
Payments of debt assumed in connection with business combination	(4.1)	0
Other	(1.2)	0
Net cash used in financing activities	(1,119.6)	(151.8)
NET INCREASE (DECREASE) IN CASH AND CASH EQUIVALENTS	(340.2)	63.1
CASH AND CASH EQUIVALENTS—Beginning of period	1,222.5	1,112.4
CASH AND CASH EQUIVALENTS—End of period	882.3	1,175.5
SUPPLEMENTAL DISCLOSURES OF CASH FLOW INFORMATION:
Operating lease liabilities arising from obtaining right-of-use assets	14.7	12.6
Cash paid to settle liability incurred for repurchase of common stock	0	4.2
NON-CASH INVESTING AND FINANCING ACTIVITIES:
Transfers of evaluation units from inventory to property and equipment	14.8	16.3
Liability for purchase of property and equipment	26.1	20.1
Liability incurred for repurchase of common stock	$ 0	$ 4

Summary of Significant Accounti

Summary of Significant Accounting Policies	9 Months Ended
	Sep. 30, 2020
Accounting Policies [Abstract]
SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES	SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES Basis of Presentation and Preparation —The unaudited condensed consolidated financial statements of Fortinet, Inc. and its wholly owned subsidiaries (collectively, “we,” “us” or “our”) have been prepared in accordance with generally accepted accounting principles in the United States (“GAAP”) for interim financial information, as well as the instructions to Form 10-Q pursuant to the rules and regulations of the U.S. Securities and Exchange Commission (the “SEC”). Accordingly, they do not include all of the information and footnotes required by GAAP for complete financial statements, and should be read in conjunction with our audited consolidated financial statements as of and for the year ended December 31, 2019, contained in our Annual Report on Form 10-K filed with the SEC on February 26, 2020. In the opinion of management, all adjustments, which includes normal recurring adjustments, considered necessary for a fair presentation have been included. All intercompany balances, transactions and cash flows have been eliminated. The results of operations for the three and nine months ended September 30, 2020 are not necessarily indicative of the results for the full year or for any future periods. The condensed consolidated balance sheet as of December 31, 2019 is derived from the audited consolidated financial statements for the year ended December 31, 2019. For 2020, the amounts previously reported as Income taxes payable are included in Accrued liabilities. Prior periods have been reclassified to conform with current period presentation. The preparation of financial statements in accordance with GAAP requires management to make estimates and assumptions that affect the amounts reported in the condensed consolidated financial statements and accompanying notes. Actual results could differ materially from those estimates. There have been no material changes to our significant accounting policies as of and for the three and nine months ended September 30, 2020. Recently Adopted Accounting Standards Financial Instruments In June 2016, the Financial Accounting Standards Board (“FASB”) issued Accounting Standards Update (“ASU”) 2016-13—Financial Instruments—Credit Losses (Topic 326): Measurement of Credit Losses on Financial Instruments (“Topic 326”), which provides guidance on how an entity should measure credit losses on financial instruments. The standard replaces the existing incurred loss model with an expected credit loss model for financial assets measured at amortized cost, including trade receivables, and requires that credit losses on available-for-sale debt securities be presented as an allowance rather than as a write-down. The new approach to estimating credit losses (referred to as the current expected credit losses model) generally accelerates recognition of credit losses. We adopted Topic 326 on January 1, 2020 using the modified retrospective method. The adoption of this standard did not have a material impact on our condensed consolidated financial statements. Cloud Computing In August 2018, the FASB issued ASU 2018-15—Intangibles—Goodwill and Other—Internal-Use Software (Subtopic 350-40): Customer’s Accounting for Implementation Costs Incurred in a Cloud Computing Arrangement That Is a Service Contract, which requires a customer in a cloud computing arrangement that is a service contract to follow the internal-use software guidance in Accounting Standards Codification (“ASC”) Topic 350, Intangibles—Goodwill and Other, to determine which implementation costs to capitalize as assets or expense as incurred. We adopted ASU 2018-15 on January 1, 2020. The adoption of this standard did not have a material impact on our condensed consolidated financial statements. Fair Value Measurements In August 2018, the FASB issued ASU 2018-13—Fair Value Measurement (Topic 820): Disclosure Framework—Changes to the Disclosure Requirements for Fair Value Measurement, which eliminates, adds and modifies certain disclosure requirements for fair value measurements in ASC 820, Fair Value Measurement, as part of its disclosure framework project. We adopted ASU 2018-13 on January 1, 2020. The adoption of this standard did not have a material impact on our disclosures. Recent Accounting Standards Not Yet Effective Income Taxes In December 2019, the FASB issued ASU 2019-12—Income Taxes (Topic 740): Simplifying the Accounting for Income Taxes. The amendments in ASU 2019-12 simplify the accounting for income taxes by removing certain exceptions to the general principles in Topic 740. The amendments also improve consistent application and simplification of GAAP for other areas of Topic 740 by clarifying and amending existing guidance. ASU 2019-12 is effective for us beginning on January 1, 2021. We are currently evaluating the impact of ASU 2019-12 on our condensed consolidated financial statements.

Immaterial Correction of Prior

Immaterial Correction of Prior Period Financial Statements	9 Months Ended
	Sep. 30, 2020
Accounting Changes and Error Corrections [Abstract]
IMMATERIAL CORRECTION OF PRIOR PERIOD FINANCIAL STATEMENTS	IMMATERIAL CORRECTION OF PRIOR PERIOD FINANCIAL STATEMENTS Subsequent to the issuance of our condensed consolidated financial statements for the period ended June 30, 2020, we identified an immaterial error related to the commencement of revenue recognition for certain FortiCare standalone service contracts. Rather than commencing recognition upon end user registration, we should have begun to recognize revenue over the service period when control had passed to the distributor which we have determined is our customer. We assessed the effect of this correction, individually and in the aggregate, on prior periods’ financial statements in accordance with the SEC’s Staff Accounting Bulletins No. 99 and 108 and, based on an analysis of quantitative and qualitative factors, determined that the correction was not individually material to any of our prior interim or annual consolidated financial statements. All financial information contained in the accompanying notes to these condensed consolidated financial statements has been revised to reflect the correction of this error. The corrections to our condensed consolidated balance sheet as of December 31, 2019 were as follows (in millions): December 31, 2019 As Previously Reported Corrections As Corrected ASSETS DEFERRED TAX ASSETS $ 232.6 $ (6.3) $ 226.3 TOTAL ASSETS 3,885.5 (6.3) 3,879.2 LIABILITIES AND STOCKHOLDERS’ EQUITY CURRENT LIABILITIES: Deferred revenue 1,173.6 (17.8) 1,155.8 Total current liabilities 1,473.6 (17.8) 1,455.8 DEFERRED REVENUE 962.3 (9.0) 953.3 Total liabilities 2,563.6 (26.8) 2,536.8 STOCKHOLDERS’ EQUITY: Retained earnings (accumulated deficit) 140.3 20.5 160.8 Total stockholders’ equity 1,321.9 20.5 1,342.4 TOTAL LIABILITIES AND STOCKHOLDERS’ EQUITY $ 3,885.5 $ (6.3) $ 3,879.2 The corrections to our condensed consolidated statements of income for the three and nine months ended September 30, 2019 were as follows (in millions, except per share amounts): Three Months Ended September 30, 2019 As Previously Reported Corrections As Corrected REVENUE: Service $ 350.4 $ 0.6 $ 351.0 Total revenue 547.5 0.6 548.1 GROSS PROFIT: Service 305.3 0.6 305.9 Total gross profit 423.4 0.6 424.0 OPERATING INCOME 100.0 0.6 100.6 INCOME BEFORE INCOME TAXES 105.4 0.6 106.0 PROVISION FOR INCOME TAXES 25.6 0.2 25.8 NET INCOME $ 79.8 $ 0.4 $ 80.2 Net income per share (Note 10): Basic $ 0.47 $ — $ 0.47 Diluted $ 0.46 $ — $ 0.46 Nine Months Ended September 30, 2019 As Previously Reported Corrections As Corrected REVENUE: Service $ 992.1 $ 3.1 $ 995.2 Total revenue 1,541.8 3.1 1,544.9 GROSS PROFIT: Service 858.6 3.1 861.7 Total gross profit 1,176.4 3.1 1,179.5 OPERATING INCOME 225.8 3.1 228.9 INCOME BEFORE INCOME TAXES 251.5 3.1 254.6 PROVISION FOR INCOME TAXES 40.2 0.9 41.1 NET INCOME $ 211.3 $ 2.2 $ 213.5 Net income per share (Note 10): Basic $ 1.24 $ 0.01 $ 1.25 Diluted $ 1.21 $ 0.01 $ 1.22 The corrections to our condensed consolidated statements of cash flows for the nine months ended September 30, 2019 were as follows (in millions): Nine Months Ended September 30, 2019 As Previously Reported Corrections As Corrected CASH FLOWS FROM OPERATING ACTIVITIES: Net income $ 211.3 $ 2.2 $ 213.5 Changes in operating assets and liabilities: Deferred tax assets 10.6 0.9 11.5 Deferred revenue 258.8 (3.1) 255.7 Net cash provided by operating activities $ 617.6 $ — $ 617.6 The results for the nine months ended September 30, 2020 include corrections to increase revenue, gross profit and operating income by $0.8 million and $2.1 million for the three months ended March 31, 2020 and June 30, 2020, respectively, and to increase net income by $0.6 million and $1.7 million for the three months ended March 31, 2020 and June 30, 2020, respectively. The correction did not change diluted net income per share for the three months ended March 31, 2020 but did increase diluted net income per share by $0.01 for the three months ended June 30, 2020. For all periods in which we corrected net income, we made corresponding corrections to net income and comprehensive income in our condensed consolidated statements of comprehensive income and to net income, retained earnings (accumulated deficit) and total stockholders’ equity in our condensed consolidated statements of stockholders’ equity.

Revenue Recognition

Revenue Recognition	9 Months Ended
	Sep. 30, 2020
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 businesses. Our revenue consists of product and service revenue. Product revenue is generated by our FortiGate network security appliances, our Fortinet Security Fabric platform products and other products. Service revenue relates to sales of our security subscription services, which mainly consist 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 $ 223.8 $ 197.1 $ 628.0 $ 549.7 Service: Security subscription 235.4 192.8 669.4 545.5 Technical support and other 191.9 158.2 549.0 449.7 Total service revenue 427.3 351.0 1,218.4 995.2 Total revenue $ 651.1 $ 548.1 $ 1,846.4 $ 1,544.9 Deferred Revenue During the three months ended September 30, 2020 and September 30, 2019, we recognized $263.1 million and $211.8 million in service revenue that was included in the deferred revenue balance as of December 31, 2019 and December 31, 2018, respectively. During the nine months ended September 30, 2020 and September 30, 2019, we recognized $921.7 million and $754.5 million in service revenue that was included in the deferred revenue balance as of December 31, 2019 and December 31, 2018, respectively. Transaction Price Allocated to the Remaining Performance Obligations As of September 30, 2020, the aggregate amount of the transaction price allocated to remaining performance obligations was $2.39 billion, which was substantially comprised of deferred security subscription and technical support services revenue. We expect to recognize approximately $1.30 billion as revenue over the next 12 months and the remainder thereafter. Accounts Receivable Trade accounts receivable are recorded at the invoiced amount. On January 1, 2020, we adopted Topic 326, which provides guidance on how to measure credit losses on financial instruments, including accounts receivable. Prior to our adoption of Topic 326, our accounts receivable balance was reduced by an allowance for doubtful accounts that we determined based on our assessment of the collectability of customer accounts. Under Topic 326, our accounts receivable balance is reduced by an allowance for 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. The COVID-19 pandemic and the recent economic downturn prompted us to perform additional credit reviews of our existing customers, including obtaining recent credit reports and reviewing their latest available statements of financial position. In addition, we have seen an increase in requests for extended payment terms. After performing our additional reviews, we increased the allowance for credit losses for certain accounts receivable. The allowance for credit losses was $2.2 million as of September 30, 2020, and the allowance for doubtful accounts was $1.2 million as of December 31, 2019. Provisions, write-offs and recoveries were not material during the nine months ended September 30, 2020. Deferred Contract Costs Sales commissions earned by our sales force are considered incremental and recoverable costs of obtaining a contract with a customer. The amortization of deferred contract costs is included in sales and marketing expense in our condensed consolidated statements of income. Amortization of deferred contract costs during the three months ended September 30, 2020 and September 30, 2019 were $35.3 million and $27.5 million, respectively. Amortization of deferred contract costs during the nine months ended September 30, 2020 and September 30, 2019 were $99.8 million and $78.5 million, respectively.

Financial Instruments and Fair

Financial Instruments and Fair Value	9 Months Ended
	Sep. 30, 2020
Financial Instruments and Fair Value [Abstract]
FINANCIAL INSTRUMENTS AND FAIR VALUE	FINANCIAL INSTRUMENTS AND FAIR VALUE The following tables summarize our investments (in millions): September 30, 2020 Amortized Unrealized Unrealized Fair Corporate debt securities $ 501.1 $ 1.8 $ (0.1) $ 502.8 U.S. government securities 166.3 0.1 — 166.4 Commercial paper 125.2 0.1 — 125.3 Certificates of deposit and term deposits (1) 97.8 — — 97.8 Total available-for-sale securities $ 890.4 $ 2.0 $ (0.1) $ 892.3 December 31, 2019 Amortized Unrealized Unrealized Fair Corporate debt securities $ 576.1 $ 1.0 $ (0.1) $ 577.0 U.S. government securities 195.0 0.2 — 195.2 Commercial paper 148.7 0.1 — 148.8 Certificates of deposit and term deposits (1) 66.4 — — 66.4 Total available-for-sale securities $ 986.2 $ 1.3 $ (0.1) $ 987.4 (1) The majority of our certificates of deposit and term deposits are foreign deposits. The following tables show the gross unrealized losses and the related fair values of our investments that have been in a continuous unrealized loss position (in millions): September 30, 2020 Less Than 12 Months 12 Months or Greater Total Fair Unrealized Fair Unrealized Fair Unrealized Corporate debt securities $ 103.9 $ — $ — $ — $ 103.9 $ — U.S. government securities 42.1 — — — 42.1 — Commercial paper 24.6 — — — 24.6 — Certificates of deposit and term deposits 17.3 (0.1) — — 17.3 (0.1) Total available-for-sale securities $ 187.9 $ (0.1) $ — $ — $ 187.9 $ (0.1) December 31, 2019 Less Than 12 Months 12 Months or Greater Total Fair Unrealized Fair Unrealized Fair Unrealized Corporate debt securities $ 117.3 $ (0.1) $ 16.1 $ — $ 133.4 $ (0.1) U.S. government securities 47.1 — — — 47.1 — Commercial paper 26.0 — — — 26.0 — Certificates of deposit and term deposits 13.0 — — — 13.0 — Total available-for-sale securities $ 203.4 $ (0.1) $ 16.1 $ — $ 219.5 $ (0.1) The contractual maturities of our investments were as follows (in millions): September 30, December 31, Due within one year $ 774.4 $ 843.1 Due within one to three years 117.9 144.3 Total $ 892.3 $ 987.4 Available-for-sale securities are reported at fair value, with unrealized gains and losses and the related tax impact included as a separate component of stockholders’ equity and in comprehensive income. Accrued interest of $3.2 million as of September 30, 2020 is excluded from both the fair value and the amortized cost of our available-for-sale securities and is recorded in Prepaid expenses and other current assets in our condensed consolidated balance sheet. We have elected to not record an allowance for credit losses for accrued interest for available-for-sale securities and will reverse the accrued interest against interest income in the period in which we determine the accrued interest to be uncollectible. Prior to 2020, we followed the guidance in ASC 320 Investments—Debt and Equity Securities in determining whether unrealized losses were other than temporary. We adopted Topic 326 on January 1, 2020, and now consider whether unrealized losses have resulted from a credit loss or other factors. The unrealized losses on our available-for-sale securities as of September 30, 2020 and as of December 31, 2019 were caused by fluctuations in market value and interest rates as a result of the economic environment. We concluded that an allowance for credit losses was unnecessary as of September 30, 2020 and that the impairments as of December 31, 2019 were not other than temporary because (i) the decline in market value was attributable to changes in market conditions and not credit quality, and (ii) we concluded that neither do we intend to sell nor is it more likely than not that we will be required to sell these investments prior to recovery of their amortized cost basis. Realized gains and losses on available-for-sale securities were insignificant in the periods presented and are included in Other income (expense)—net in our consolidated statements of income. We use the specific identification method to determine the cost basis of investments sold. Fair Value Accounting—We apply the following fair value hierarchy for disclosure of the inputs used to measure fair value. This hierarchy prioritizes the inputs into three broad levels as follows: Level 1—Inputs are unadjusted quoted prices in active markets for identical assets or liabilities. Level 2—Inputs are quoted prices for similar assets and liabilities in active markets or inputs that are observable for the assets or liabilities, either directly or indirectly through market corroboration, for substantially the full term of the financial instruments. Level 3—Unobservable inputs based on our own assumptions used to measure assets and liabilities at fair value. The inputs require significant management judgment or estimation. We measure the fair value of money market funds and certain U.S. government securities using quoted prices in active markets for identical assets. The fair value of all other financial instruments was based on quoted prices for similar assets in active markets, or model-driven valuations using significant inputs derived from or corroborated by observable market data. We classify investments within Level 1 if quoted prices are available in active markets for identical securities. We classify items within Level 2 if the investments are valued using model-driven valuations using observable inputs such as quoted market prices, benchmark yields, reported trades, broker/dealer quotes or alternative pricing sources with reasonable levels of price transparency. Investments are held by custodians who obtain investment prices from a third-party pricing provider that incorporates standard inputs in various asset price models. Fair Value of Financial Instruments Assets Measured at Fair Value on a Recurring Basis The following tables present the fair value of our financial assets measured at fair value on a recurring basis as of September 30, 2020 and December 31, 2019 (in millions): September 30, 2020 December 31, 2019 Aggregate Quoted Significant Significant Aggregate Quoted Significant Significant (Level 1) (Level 2) (Level 3) (Level 1) (Level 2) (Level 3) Assets: Corporate debt securities $ 505.9 $ — $ 505.9 $ — $ 577.0 $ — $ 577.0 $ — U.S. government securities 166.4 166.4 — — 195.2 195.2 — — Commercial paper 125.3 — 125.3 — 165.8 — 165.8 — Certificates of deposit and term deposits 97.8 — 97.8 — 66.4 — 66.4 — Money market funds 164.0 164.0 — — 15.0 15.0 — — Total $ 1,059.4 $ 330.4 $ 729.0 $ — $ 1,019.4 $ 210.2 $ 809.2 $ — Reported as: Cash equivalents $ 167.1 $ 32.0 Short-term investments 774.4 843.1 Long-term investments 117.9 144.3 Total $ 1,059.4 $ 1,019.4 There were no transfers between Level 1 and Level 2 of the fair value hierarchy during the nine months ended September 30, 2020 and year ended December 31, 2019.

Inventory

Inventory	9 Months Ended
	Sep. 30, 2020
Inventory Disclosure [Abstract]
INVENTORY	INVENTORY Inventory consisted of the following (in millions): September 30, December 31, Raw materials $ 15.6 $ 9.7 Finished goods 118.9 108.2 Inventory $ 134.5 $ 117.9

Property and Equipment_Net

Property and Equipment—Net	9 Months Ended
	Sep. 30, 2020
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 $ 93.3 $ 93.3 Building and building improvements 148.1 147.4 Computer equipment and software 131.5 116.7 Leasehold improvements 30.3 25.5 Evaluation units 18.8 19.9 Furniture and fixtures 20.0 17.3 Construction-in-progress 140.8 61.2 Total property and equipment 582.8 481.3 Less: accumulated depreciation (163.4) (137.0) Property and equipment—net $ 419.4 $ 344.3 Construction-in-progress consists primarily of costs incurred in connection with the construction of a second building at our headquarters campus. Depreciation expense was $13.9 million and $12.8 million during the three months ended September 30, 2020 and September 30, 2019, respectively. Depreciation expense was $41.6 million and $37.8 million during the nine months ended September 30, 2020 and September 30, 2019, respectively.

Investments in Privately-Held C

Investments in Privately-Held Companies	9 Months Ended
	Sep. 30, 2020
Investments, All Other Investments [Abstract]
INVESTMENTS IN PRIVATELY-HELD COMPANIES	INVESTMENTS IN PRIVATELY HELD COMPANIESOur investments in the equity securities of privately held companies without readily determinable fair values totaled $1.0 million and $5.3 million as of September 30, 2020 and December 31, 2019, respectively. These investments are accounted for at cost, adjusted for changes in observable prices minus impairment. We own less than 20% of the voting securities in each of these investments and do not have the ability to exercise significant influence over operating and financial policies of the respective entities. These investments are recorded as Other assets in our condensed consolidated balance sheets and would be measured at fair value if indicators of an increase in value or impairment existed. In the first quarter of 2020 and in the third quarter of 2019, we recognized non-cash impairment charges of $4.3 million and $3.8 million in Other expense—net in our condensed consolidated statements of income, respectively. Cumulative impairment adjustments to all equity securities without readily determinable fair values totaled $8.1 million since their respective acquisitions through September 30, 2020. As of September 30, 2020, no other events have occurred that would affect the carrying value of these investments.

Business Combinations

Business Combinations	9 Months Ended
	Sep. 30, 2020
Business Combinations [Abstract]
BUSINESS COMBINATIONS	BUSINESS COMBINATION OPAQ Networks, Inc. On July 20, 2020, we acquired all outstanding shares of OPAQ Networks, Inc. (“OPAQ”), a privately held Secure Access Service Edge (“SASE”) cloud provider. Under the acquisition method of accounting in accordance with ASC 805, the total preliminary purchase price was allocated to OPAQ’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 preliminary purchase price for OPAQ was $8.0 million in cash, of which $1.0 million was allocated to goodwill, $4.7 million was allocated to identifiable intangible assets, the majority of which was developed technology, and $2.3 million was allocated to other net assets acquired, which predominantly included cash, deferred tax assets, operating lease right-of-use assets and lease liabilities, accounts payable, accrued liabilities and assumed debt. The preliminary purchase price included a $1.3 million indemnity fund held in escrow for 12 months after the transaction closing date. 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, and goodwill is non-deductible for tax purposes. 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 are included in our condensed consolidated statement of income from the date of acquisition. Acquisition-related costs for this acquisition were not material. Pro forma information has not been presented as the impact of this acquisition was not material to our condensed consolidated financial statements.

Goodwill and Other Intangible A

Goodwill and Other Intangible Assets - Net	9 Months Ended
	Sep. 30, 2020
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 2019 $ 67.2 Addition due to business combination 1.0 Balance—September 2020 $ 68.2 There were no impairments to goodwill during the nine months ended September 30, 2020 or during prior periods. Other Intangible Assets—Net The following tables present other intangible assets—net as of September 30, 2020 and December 31, 2019 (in millions, except years): September 30, 2020 Weighted-Average Useful Life (in Years) Gross Accumulated Amortization Net Other intangible assets—net: Finite-lived intangible assets: Developed technologies 4.0 $ 53.3 $ 30.2 $ 23.1 Customer relationships 4.1 21.8 19.6 2.2 Total other intangible assets—net $ 75.1 $ 49.8 $ 25.3 December 31, 2019 Weighted-Average Useful Life (in Years) Gross Accumulated Amortization Net Other intangible assets—net: Finite-lived intangible assets: Developed technologies 4.0 $ 50.2 $ 24.6 $ 25.6 Customer relationships 4.1 21.6 16.1 5.5 Total other intangible assets—net $ 71.8 $ 40.7 $ 31.1 Amortization expense was $2.8 million and $2.2 million during the three months ended September 30, 2020 and September 30, 2019, respectively. Amortization expense was $10.5 million and $8.1 million during the nine months ended September 30, 2020 and September 30, 2019, respectively. The following table summarizes estimated future amortization expense of finite-lived intangible assets—net (in millions): Amount Years: 2020 (the remainder of 2020) $ 2.7 2021 9.6 2022 7.5 2023 4.8 2024 0.7 Total $ 25.3

Net Income Per Share

Net Income Per Share	9 Months Ended
	Sep. 30, 2020
Earnings Per Share [Abstract]
NET INCOME PER SHARE	NET INCOME PER SHARE Basic net income per share is computed by dividing net income by the weighted-average number of shares of common stock outstanding during the period. Diluted net income per share is computed by dividing net income by the weighted-average number of shares of common stock outstanding during the period, plus the dilutive effects of restricted stock units (“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 $ 123.4 $ 80.2 $ 341.8 $ 213.5 Denominator: Basic shares: Weighted-average common stock outstanding-basic 162.1 171.3 164.8 170.9 Diluted shares: Weighted-average common stock outstanding-basic 162.1 171.3 164.8 170.9 Effect of potentially dilutive securities: RSUs 2.3 2.4 2.4 2.9 Stock options 1.2 1.1 1.2 1.1 Weighted-average shares used to compute diluted net income per share 165.6 174.8 168.4 174.9 Net income per share: Basic $ 0.76 $ 0.47 $ 2.07 $ 1.25 Diluted $ 0.75 $ 0.46 $ 2.03 $ 1.22 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 0.3 0.2 0.3 0.3 Stock options 0.6 0.7 0.5 0.6 Total 0.9 0.9 0.8 0.9

Leases

Leases	9 Months Ended
	Sep. 30, 2020
Leases [Abstract]
LEASES	LEASES We have operating leases for offices, research and development facilities and data centers. Our leases have remaining terms that range from less than one year to approximately seven years, some of which include one or more options to renew, with renewal terms of up to 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 $ 4.8 $ 3.8 $ 13.5 $ 11.1 Variable lease expense (1) 0.7 0.7 1.7 1.9 Short-term lease expense 1.0 0.8 2.9 2.2 Total lease expense $ 6.5 $ 5.3 $ 18.1 $ 15.2 (1) Variable lease expense for the nine months ended September 30, 2020 and September 30, 2019 predominantly included common area maintenance charges and parking expense. Supplemental balance sheet information related to our operating leases was as follows (in millions, except lease term and discount rate): Classification September 30, December 31, Operating lease ROU assets - non-current Other assets $ 45.6 $ 44.3 Operating lease liabilities - current Accrued liabilities $ 17.2 $ 15.5 Operating lease liabilities - non-current Other liabilities 31.0 30.6 Total operating lease liabilities $ 48.2 $ 46.1 Weighted average remaining lease term in years - operating leases 3.6 3.7 Weighted average discount rate - operating leases 3.2 % 2.8 % Supplemental cash flow information related to leases was as follows (in millions): Nine Months Ended 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 $ 13.8 $ 11.9 Maturities of operating lease liabilities as of September 30, 2020 were as follows (in millions): Year ending December 31, Amount 2020 (the remainder of 2020) $ 4.2 2021 17.8 2022 12.6 2023 7.2 2024 5.3 Thereafter 4.0 Total lease payments 51.1 Less imputed interest (2.9) Total $ 48.2 As of September 30, 2020, we had additional minimum lease payments of $3.8 million relating to operating leases that had been signed but had not yet commenced and therefore were excluded from the table above. These leases will commence during 2020 and will have lease terms of approximately three
LEASES	LEASES We have operating leases for offices, research and development facilities and data centers. Our leases have remaining terms that range from less than one year to approximately seven years, some of which include one or more options to renew, with renewal terms of up to six years. Unless and until we are reasonably certain we will exercise these renewal options, we do not include renewal options in our lease terms for calculating our lease liability, as the renewal options allow us to maintain operational flexibility. During the year ended December 31, 2019, we entered into a finance lease with $3.6 million lease liabilities arising from obtaining right-of-use assets with a lease term of approximately two years. Our remaining finance leases were not material to our condensed consolidated financial statements. The related assumptions and further disclosures for finance leases are not material. The components of lease expense were as follows (in millions): Three Months Ended Nine Months Ended September 30, September 30, September 30, September 30, Operating lease expense $ 4.8 $ 3.8 $ 13.5 $ 11.1 Variable lease expense (1) 0.7 0.7 1.7 1.9 Short-term lease expense 1.0 0.8 2.9 2.2 Total lease expense $ 6.5 $ 5.3 $ 18.1 $ 15.2 (1) Variable lease expense for the nine months ended September 30, 2020 and September 30, 2019 predominantly included common area maintenance charges and parking expense. Supplemental balance sheet information related to our operating leases was as follows (in millions, except lease term and discount rate): Classification September 30, December 31, Operating lease ROU assets - non-current Other assets $ 45.6 $ 44.3 Operating lease liabilities - current Accrued liabilities $ 17.2 $ 15.5 Operating lease liabilities - non-current Other liabilities 31.0 30.6 Total operating lease liabilities $ 48.2 $ 46.1 Weighted average remaining lease term in years - operating leases 3.6 3.7 Weighted average discount rate - operating leases 3.2 % 2.8 % Supplemental cash flow information related to leases was as follows (in millions): Nine Months Ended 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 $ 13.8 $ 11.9 Maturities of operating lease liabilities as of September 30, 2020 were as follows (in millions): Year ending December 31, Amount 2020 (the remainder of 2020) $ 4.2 2021 17.8 2022 12.6 2023 7.2 2024 5.3 Thereafter 4.0 Total lease payments 51.1 Less imputed interest (2.9) Total $ 48.2 As of September 30, 2020, we had additional minimum lease payments of $3.8 million relating to operating leases that had been signed but had not yet commenced and therefore were excluded from the table above. These leases will commence during 2020 and will have lease terms of approximately three

Mutual Covenant-Not-to-Sue and

Mutual Covenant-Not-to-Sue and Release Agreement	9 Months Ended
	Sep. 30, 2020
Mutual Covenant-Not-to-Sue Agreement [Abstract]
MUTUAL COVENANT-NOT-TO-SUE AND RELEASE AGREEMENT	MUTUAL COVENANT-NOT-TO-SUE AND RELEASE AGREEMENT In January 2020, we entered into an agreement with a competitor in the network security industry whereby, in February 2020, the competitor party paid us a lump sum of $50.0 million for a seven-year mutual covenant-not-to-sue for patent claims. Pursuant to this agreement, at the end of this first seven-year period, either party may extend the agreement for an additional seven-year mutual covenant-not-to-sue in return for this competitor paying us an additional $50.0 million. This agreement arose after expiration of previous agreements between the parties whereby the competitor had paid us sums for a limited term license to certain of our intellectual property (“IP”) and a limited term mutual covenant-not-to-sue. We concluded that the agreement was a 14-year contract with a total transaction price of $100.0 million, and that it contained two material distinct performance obligations: (1) the right to use our existing patents, and (2) the right to use any patents that we develop over the term of the contract. We allocated $36.0 million to the functional patents, which was recognized upon commencement of the contract; the remaining $64.0 million, representing the right to utilize future patents, will be recognized over the contract term. We further concluded that our existing patents represent functional IP that should be recognized upon granting our competitor access. We also concluded that the right to receive additional functional IP that we will develop in the future represents a stand ready obligation. Therefore, the transaction price allocated to this obligation is recognized ratably over the 14-year contract term. We estimated the stand-alone selling price of each distinct performance obligation and allocated the $100.0 million transaction price. During the three and nine months ended September 30, 2020, we recorded $1.1 million and $39.0 million in Gain on IP matter in our condensed consolidated statements of income, respectively. We recorded $11.0 million in Accrued liabilities and Other liabilities in our condensed consolidated balance sheet as of September 30, 2020.

Commitments and Contingencies

Commitments and Contingencies	9 Months Ended
	Sep. 30, 2020
Commitments and Contingencies Disclosure [Abstract]
COMMITMENTS AND CONTINGENCIES	COMMITMENTS AND CONTINGENCIES The following table summarizes our inventory purchase commitments as of September 30, 2020 (in millions): Total 2020 2021 2022 2023 2024 Thereafter Inventory purchase commitments $ 284.7 $ 207.6 $ 77.1 $ — $ — $ — $ — Inventory Purchase Commitments —Our independent contract manufacturers procure components and build our products based on our forecasts. These forecasts are based on estimates of future demand for our products, which are in turn based on historical trends and an analysis from our sales and marketing organizations, adjusted for overall market conditions. In order to reduce manufacturing lead times and plan for adequate component supply, we may issue purchase orders to some of our independent contract manufacturers, which may not be cancelable. As of September 30, 2020, we had $284.7 million of open purchase orders with our independent contract manufacturers that may not be cancelable. Other Contractual Commitments and Open Purchase Orders —In addition to commitments with contract manufacturers, we have open purchase orders and contractual obligations in the ordinary course of business for which we have not received goods or services. As of September 30, 2020, we had $23.1 million in other contractual commitments having a remaining term in excess of one year that may not be cancelable. Litigation —We are involved in disputes, litigation, and other legal actions. For lawsuits where we are the defendant, we are in the process of defending these litigation matters, and while there can be no assurances and the outcome of certain of these matters is currently not determinable and not predictable, we currently are unaware of any existing claims or proceedings that we believe are likely to have a material adverse effect on our financial position. There are many uncertainties associated with any litigation and these actions or other third-party claims against us may cause us to incur costly litigation fees, costs and substantial settlement charges, and possibly subject us to damages and other penalties. In addition, the resolution of any IP litigation may require us to make royalty payments, which could adversely affect our gross margins in future periods. If any of those events were to occur, our business, financial condition, results of operations, and cash flows could be adversely affected. Litigation is unpredictable and the actual liability in any such matters may be materially different from our current estimates, which could result in the need to adjust any accrued liability and record additional expenses. We accrue for contingencies when we believe that a loss is probable and that we can reasonably estimate the amount of any such loss. Indemnification and Other Matters —Under the indemnification provisions of our standard sales contracts, we agree to defend our customers against third-party claims asserting various allegations such as product defects and infringement of certain IP rights, which may include patents, copyrights, trademarks or trade secrets, and to pay judgments entered on such claims. In some contracts, our exposure under these indemnification provisions is limited by the terms of the contracts to certain defined limits, such as the total amount paid by our customer under the agreement. However, certain agreements include covenants, penalties and indemnification provisions including and beyond indemnification for third-party claims of IP infringement that could potentially expose us to losses in excess of the amount received under the agreement, and in some instances to potential liability that is not contractually limited. Although from time to time there are indemnification claims asserted against us and currently there are pending indemnification claims, to date there have been no material awards under such indemnification provisions. Similar to other security companies and companies in other industries, we have in the past experienced, and we may in the future experience, cybersecurity threats, malicious activity directed against our information technology infrastructure or unauthorized attempts to gain access to our and our customers’ sensitive information and systems. We currently are unaware of any existing claims or proceedings related to these types of matters, including any that we believe are likely to have a material adverse effect on our financial position.

Stockholders' Equity

Stockholders' Equity	9 Months Ended
	Sep. 30, 2020
Share-based Payment Arrangement [Abstract]
STOCKHOLDERS' EQUITY	STOCKHOLDERS’ EQUITY Stock-Based Compensation Plans We maintain the Amended and Restated Fortinet, Inc. 2009 Equity Incentive Plan (the “Amended Plan”) pursuant to which we have granted RSUs and stock options. As of September 30, 2020, there was a total of 12.1 million shares of common stock available for grant under the Amended Plan. We also previously had an Employee Stock Purchase Plan (“ESPP”) for eligible employees, which was terminated in February 2019. 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, 2019 6.1 $ 64.56 Granted 1.8 121.30 Forfeited (0.3) 76.80 Vested (2.3) 57.07 Balance—September 30, 2020 5.3 $ 86.31 Stock compensation expense is recognized on a straight-line basis over the vesting period of each RSU. As of September 30, 2020, total compensation expense related to unvested RSUs granted to employees and non-employees under the 2009 Plan, but not yet recognized, was $399.1 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 0.2 0.2 0.7 0.9 Amount withheld for taxes $ 27.6 $ 19.6 $ 86.5 $ 76.1 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 39.9 % 35.3 % 34.6 % 34.2 % Risk-free interest rate 0.2 % 1.4 % 1.1 % 2.4 % 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, 2019 2.7 $ 50.37 Granted 0.6 118.96 Forfeited (0.1) 91.73 Exercised (0.4) 40.99 Balance—September 30, 2020 2.8 $ 66.72 Options vested and expected to vest—September 30, 2020 2.8 $ 66.72 4.4 $ 146.4 Options exercisable—September 30, 2020 1.5 $ 42.81 3.3 $ 109.6 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, 2020 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, 2020, total compensation expense related to unvested stock options granted to employees but not yet recognized was $35.1 million, with a weighted-average remaining vesting period of 2.8 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 $ 43.80 $ 24.97 $ 35.76 $ 26.96 Intrinsic value of options exercised 5.5 3.2 35.8 40.1 Fair value of options vested 2.5 2.0 10.9 8.2 Stock-Based Compensation Expense Stock-based compensation expense, including stock-based compensation expense related to awards classified as liabilities, is included in costs and expenses as follows (in millions): Three Months Ended Nine Months Ended September 30, September 30, September 30, September 30, Cost of product revenue $ 0.4 $ 0.4 $ 1.2 $ 1.2 Cost of service revenue 3.3 2.7 9.5 8.4 Research and development 12.7 9.3 35.6 28.7 Sales and marketing 27.7 24.9 81.3 76.6 General and administrative 5.9 5.1 17.3 15.5 Total stock-based compensation expense $ 50.0 $ 42.4 $ 144.9 $ 130.4 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 $ 46.4 $ 39.5 $ 134.5 $ 120.6 Stock options 3.6 2.9 10.4 8.5 ESPP — — — 1.3 Total stock-based compensation expense $ 50.0 $ 42.4 $ 144.9 $ 130.4 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 $ 11.0 $ 9.8 $ 31.9 $ 30.1 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. During the nine months ended September 30, 2020, we repurchased 11.4 million shares of common stock under the Repurchase Program in open market transactions at an average price $91.55 per share, for an aggregate purchase price $1.05 billion. As of September 30, 2020, $1.05 billion remained available for future share repurchases under the Repurchase Program.

Income Taxes

Income Taxes	9 Months Ended
	Sep. 30, 2020
Income Tax Disclosure [Abstract]
INCOME TAXES	INCOME TAXES Our effective tax rate was 4% for the three months ended September 30, 2020, compared to an effective tax rate of 24% for the same period last year. Our effective tax rate was 8% for the nine months ended September 30, 2020, compared to an effective tax rate of 16% for the same period last year. The effective tax rates for the periods presented are primarily comprised of U.S. federal and state taxes, withholding taxes, foreign taxes and excess tax benefits from stock-based compensation expense. The tax rates for the three months ended September 30, 2020 and September 30, 2019 were impacted by U.S. federal and state taxes, withholding taxes and foreign taxes that were $17.5 million and $32.7 million, respectively. The U.S. federal and state taxes included a tax benefit of $16.0 million from the foreign-derived intangible income deduction for the three months ended September 30, 2020. The tax rates for the three months ended September 30, 2020 and September 30, 2019 were impacted by excess tax benefits from stock-based compensation expense of $12.5 million and $6.9 million, respectively. The tax rates for the nine months ended September 30, 2020 and September 30, 2019 were impacted by U.S. federal and state taxes, withholding taxes and foreign taxes of $74.8 million and $75.4 million, respectively. The U.S. federal and state taxes included a tax benefit of $25.6 million from the foreign-derived intangible income deduction for the nine months ended September 30, 2020. The tax rates for the nine months ended September 30, 2020 and September 30, 2019 were impacted by excess tax benefits from stock-based compensation expense of $37.6 million and $34.6 million, respectively, and release of reserves of $9.0 million and $10.0 million, respectively, on uncertain tax positions and the interest due to the expiration of the statute of limitations. The provision for income taxes for the nine months ended September 30, 2019 was further impacted by an increase in tax expense of $10.3 million for an unrecognized tax benefit related to the opinion of the U.S. Court of Appeals for the Ninth Circuit (the “Ninth Circuit”) in Altera Corporation and Subsidiaries vs. Commissioner of Internal Revenue (“ Altera ”) described below, regarding stock-based compensation expense in cost sharing arrangements. As of September 30, 2020 and December 31, 2019, unrecognized tax benefits were $67.1 million and $67.5 million, respectively. If recognized, $61.7 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, 2020 and December 31, 2019, accrued interest and penalties were $13.1 million and $14.1 million, respectively. It is reasonably possible that our gross unrecognized tax benefits will decrease by up to $4.0 million in the next 12 months, due to the lapse of the statute of limitations. This decrease, if recognized, would positively impact our effective tax rate, and would be recognized as additional tax benefits. We file income tax returns in the U.S. federal jurisdiction and in various U.S. state and foreign jurisdictions. Generally, we are no longer subject to U.S. state and foreign income tax examinations by tax authorities for tax years prior to 2010. We are no longer subject to examination by U.S federal income tax authorities for tax years prior to 2015. We currently have ongoing tax audits in the United Kingdom, Canada and several other foreign jurisdictions. The focus of these audits is the inter-company profit allocation. On June 7, 2019, the Ninth Circuit overturned the U.S. Tax Court’s decision in Altera and ruled in favor of the Commissioner, validating the regulations requiring that stock-based compensation be included in a cost sharing arrangement. On June 22, 2020, the Supreme Court of the United States (the “Supreme Court”) issued an order declining the petition for certiorari in Altera . As a result, the Ninth Circuit’s decision requiring that stock-based compensation be included in cost sharing arrangements is the controlling law at present. However, as we are no longer part of a cost sharing arrangement, this does not impact our future income tax provisions. The Ninth Circuit’s decision, together with Supreme Court’s order, did not have a material impact on our condensed consolidated financial statements. On March 27, 2020, the President signed into law the Coronavirus Aid, Relief, and Economic Security Act (the “CARES Act”). The CARES Act provides numerous tax provisions and other stimulus measures, including temporary changes regarding the prior and future utilization of net operating losses, temporary changes to the prior and future limitations on interest deductions, temporary suspension of certain payment requirements for the employer portion of Social Security taxes, technical corrections from prior tax legislation for tax depreciation of certain qualified improvement property and the creation of certain refundable employee retention credits. We do not expect there to be a material tax impact on our condensed consolidated financial statements at this time and will continue to assess the implications of the CARES Act and its continuing developments and interpretations. 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 foreign-derived intangible income deduction and 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. On September 29, 2020, the U.S. Treasury and the IRS released final regulations related to foreign tax credits that were the subject of proposed regulations issued in December 2019 and proposed certain provisions in proposed regulations issued in December 2019. The final and proposed regulations provide administrative guidance for the foreign tax credit regime, which was updated in the 2017 Tax Cuts and Jobs Act. Generally, the provisions that were included in the 2019 proposed regulations apply to taxable years ending on or after December 16, 2019, except as otherwise specified. We are in the process of analyzing the tax impact from the final regulations on our foreign tax credit calculation.

Defined Contribution Plans

Defined Contribution Plans	9 Months Ended
	Sep. 30, 2020
Retirement Benefits [Abstract]
DEFINED CONTRIBUTION PLANS	DEFINED CONTRIBUTION PLANSOur tax-deferred savings plan under our 401(k) Plan permits participating U.S. employees to contribute a portion of their pre-tax or after-tax earnings. In Canada, we have a Group Registered Retirement Savings Plan Program (the “RRSP”), which permits participants to make tax-deductible contributions. Our board of directors approved 50% matching contributions on employee contributions up to 4% of each employee’s eligible earnings. Our matching contributions to our 401(k) Plan and the RRSP for the three months ended September 30, 2020 and September 30, 2019 were $2.1 million and $1.8 million, respectively. Our matching contributions to our 401(k) Plan and the RRSP for the nine months ended September 30, 2020 and September 30, 2019 were $6.5 million and $5.2 million, respectively.

Segment Information

Segment Information	9 Months Ended
	Sep. 30, 2020
Segment Reporting [Abstract]
SEGMENT INFORMATION	SEGMENT INFORMATION Operating segments are defined as components of an enterprise about which separate financial information is available that is evaluated regularly by the chief operating decision maker in deciding how to allocate resources and in assessing performance. Our chief operating decision maker is our chief executive officer. Our chief executive officer reviews financial information presented on a consolidated basis, accompanied by information about revenue by geographic region for purposes of allocating resources and evaluating financial performance. We have one business activity, and there are no segment managers who are held accountable for operations, operating results and plans for levels or components below the consolidated unit level. Accordingly, we have determined that we have one operating segment, and therefore, one reportable segment. Revenue by geographic region is based on the billing address of our customers. The following tables set forth revenue and property and equipment—net by geographic region (in millions): Three Months Ended Nine Months Ended Revenue September 30, September 30, September 30, September 30, Americas: United States $ 206.0 $ 182.3 $ 589.1 $ 506.9 Other Americas 66.4 58.7 186.9 161.1 Total Americas 272.4 241.0 776.0 668.0 Europe, Middle East and Africa (“EMEA”) 243.3 200.9 693.5 571.1 Asia Pacific (“APAC”) 135.4 106.2 376.9 305.8 Total revenue $ 651.1 $ 548.1 $ 1,846.4 $ 1,544.9 Property and Equipment — net September 30, December 31, Americas: United States $ 270.9 $ 197.4 Canada 121.3 120.5 Latin America 6.9 5.5 Total Americas 399.1 323.4 EMEA 15.3 15.2 APAC 5.0 5.7 Total property and equipment—net $ 419.4 $ 344.3 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”) 29 % 30 % 30 % 31 % Ingram Micro, Inc. (“Ingram Micro”) 10 % 11 % 10 % 11 % The following distributors accounted for 10% or more of net accounts receivable: September 30, December 31, Exclusive 31 % 36 % Ingram Micro 11 % 10 % Tech Data Corporation 10 % * * Represents less than 10%

Summary of Significant Accoun_2

Summary of Significant Accounting Policies (Policies)	9 Months Ended
	Sep. 30, 2020
Accounting Policies [Abstract]
Basis of Presentation and Preparation	Basis of Presentation and Preparation —The unaudited condensed consolidated financial statements of Fortinet, Inc. and its wholly owned subsidiaries (collectively, “we,” “us” or “our”) have been prepared in accordance with generally accepted accounting principles in the United States (“GAAP”) for interim financial information, as well as the instructions to Form 10-Q pursuant to the rules and regulations of the U.S. Securities and Exchange Commission (the “SEC”). Accordingly, they do not include all of the information and footnotes required by GAAP for complete financial statements, and should be read in conjunction with our audited consolidated financial statements as of and for the year ended December 31, 2019, contained in our Annual Report on Form 10-K filed with the SEC on February 26, 2020. In the opinion of management, all adjustments, which includes normal recurring adjustments, considered necessary for a fair presentation have been included. All intercompany balances, transactions and cash flows have been eliminated. The results of operations for the three and nine months ended September 30, 2020 are not necessarily indicative of the results for the full year or for any future periods. The condensed consolidated balance sheet as of December 31, 2019 is derived from the audited consolidated financial statements for the year ended December 31, 2019. For 2020, the amounts previously reported as Income taxes payable are included in Accrued liabilities. Prior periods have been reclassified to conform with current period presentation. The preparation of financial statements in accordance with GAAP requires management to make estimates and assumptions that affect the amounts reported in the condensed consolidated financial statements and accompanying notes. Actual results could differ materially from those estimates. There have been no material changes to our significant accounting policies as of and for the three and nine months ended September 30, 2020.
Recently Adopted Accounting Standards and Recent Accounting Standards Not Yet Effective	Recently Adopted Accounting Standards Financial Instruments In June 2016, the Financial Accounting Standards Board (“FASB”) issued Accounting Standards Update (“ASU”) 2016-13—Financial Instruments—Credit Losses (Topic 326): Measurement of Credit Losses on Financial Instruments (“Topic 326”), which provides guidance on how an entity should measure credit losses on financial instruments. The standard replaces the existing incurred loss model with an expected credit loss model for financial assets measured at amortized cost, including trade receivables, and requires that credit losses on available-for-sale debt securities be presented as an allowance rather than as a write-down. The new approach to estimating credit losses (referred to as the current expected credit losses model) generally accelerates recognition of credit losses. We adopted Topic 326 on January 1, 2020 using the modified retrospective method. The adoption of this standard did not have a material impact on our condensed consolidated financial statements. Cloud Computing In August 2018, the FASB issued ASU 2018-15—Intangibles—Goodwill and Other—Internal-Use Software (Subtopic 350-40): Customer’s Accounting for Implementation Costs Incurred in a Cloud Computing Arrangement That Is a Service Contract, which requires a customer in a cloud computing arrangement that is a service contract to follow the internal-use software guidance in Accounting Standards Codification (“ASC”) Topic 350, Intangibles—Goodwill and Other, to determine which implementation costs to capitalize as assets or expense as incurred. We adopted ASU 2018-15 on January 1, 2020. The adoption of this standard did not have a material impact on our condensed consolidated financial statements. Fair Value Measurements In August 2018, the FASB issued ASU 2018-13—Fair Value Measurement (Topic 820): Disclosure Framework—Changes to the Disclosure Requirements for Fair Value Measurement, which eliminates, adds and modifies certain disclosure requirements for fair value measurements in ASC 820, Fair Value Measurement, as part of its disclosure framework project. We adopted ASU 2018-13 on January 1, 2020. The adoption of this standard did not have a material impact on our disclosures. Recent Accounting Standards Not Yet Effective Income Taxes In December 2019, the FASB issued ASU 2019-12—Income Taxes (Topic 740): Simplifying the Accounting for Income Taxes. The amendments in ASU 2019-12 simplify the accounting for income taxes by removing certain exceptions to the general principles in Topic 740. The amendments also improve consistent application and simplification of GAAP for other areas of Topic 740 by clarifying and amending existing guidance. ASU 2019-12 is effective for us beginning on January 1, 2021. We are currently evaluating the impact of ASU 2019-12 on our condensed consolidated financial statements.

Immaterial Correction of Prio_2

Immaterial Correction of Prior Period Financial Statements (Tables)	9 Months Ended
	Sep. 30, 2020
Accounting Changes and Error Corrections [Abstract]
Schedule of Effects of Corrections to Prior Period Financial Statements	The corrections to our condensed consolidated balance sheet as of December 31, 2019 were as follows (in millions): December 31, 2019 As Previously Reported Corrections As Corrected ASSETS DEFERRED TAX ASSETS $ 232.6 $ (6.3) $ 226.3 TOTAL ASSETS 3,885.5 (6.3) 3,879.2 LIABILITIES AND STOCKHOLDERS’ EQUITY CURRENT LIABILITIES: Deferred revenue 1,173.6 (17.8) 1,155.8 Total current liabilities 1,473.6 (17.8) 1,455.8 DEFERRED REVENUE 962.3 (9.0) 953.3 Total liabilities 2,563.6 (26.8) 2,536.8 STOCKHOLDERS’ EQUITY: Retained earnings (accumulated deficit) 140.3 20.5 160.8 Total stockholders’ equity 1,321.9 20.5 1,342.4 TOTAL LIABILITIES AND STOCKHOLDERS’ EQUITY $ 3,885.5 $ (6.3) $ 3,879.2 The corrections to our condensed consolidated statements of income for the three and nine months ended September 30, 2019 were as follows (in millions, except per share amounts): Three Months Ended September 30, 2019 As Previously Reported Corrections As Corrected REVENUE: Service $ 350.4 $ 0.6 $ 351.0 Total revenue 547.5 0.6 548.1 GROSS PROFIT: Service 305.3 0.6 305.9 Total gross profit 423.4 0.6 424.0 OPERATING INCOME 100.0 0.6 100.6 INCOME BEFORE INCOME TAXES 105.4 0.6 106.0 PROVISION FOR INCOME TAXES 25.6 0.2 25.8 NET INCOME $ 79.8 $ 0.4 $ 80.2 Net income per share (Note 10): Basic $ 0.47 $ — $ 0.47 Diluted $ 0.46 $ — $ 0.46 Nine Months Ended September 30, 2019 As Previously Reported Corrections As Corrected REVENUE: Service $ 992.1 $ 3.1 $ 995.2 Total revenue 1,541.8 3.1 1,544.9 GROSS PROFIT: Service 858.6 3.1 861.7 Total gross profit 1,176.4 3.1 1,179.5 OPERATING INCOME 225.8 3.1 228.9 INCOME BEFORE INCOME TAXES 251.5 3.1 254.6 PROVISION FOR INCOME TAXES 40.2 0.9 41.1 NET INCOME $ 211.3 $ 2.2 $ 213.5 Net income per share (Note 10): Basic $ 1.24 $ 0.01 $ 1.25 Diluted $ 1.21 $ 0.01 $ 1.22 The corrections to our condensed consolidated statements of cash flows for the nine months ended September 30, 2019 were as follows (in millions): Nine Months Ended September 30, 2019 As Previously Reported Corrections As Corrected CASH FLOWS FROM OPERATING ACTIVITIES: Net income $ 211.3 $ 2.2 $ 213.5 Changes in operating assets and liabilities: Deferred tax assets 10.6 0.9 11.5 Deferred revenue 258.8 (3.1) 255.7 Net cash provided by operating activities $ 617.6 $ — $ 617.6

Revenue Recognition (Tables)

Revenue Recognition (Tables)	9 Months Ended
	Sep. 30, 2020
Revenue from Contract with Customer [Abstract]
Disaggregation of Revenue	Disaggregation of Revenue The following table presents our revenue disaggregated by major product and service lines (in millions): Three Months Ended Nine Months Ended September 30, September 30, September 30, September 30, Product $ 223.8 $ 197.1 $ 628.0 $ 549.7 Service: Security subscription 235.4 192.8 669.4 545.5 Technical support and other 191.9 158.2 549.0 449.7 Total service revenue 427.3 351.0 1,218.4 995.2 Total revenue $ 651.1 $ 548.1 $ 1,846.4 $ 1,544.9

Financial Instruments and Fai_2

Financial Instruments and Fair Value (Tables)	9 Months Ended
	Sep. 30, 2020
Financial Instruments and Fair Value [Abstract]
Summary of Investments	The following tables summarize our investments (in millions): September 30, 2020 Amortized Unrealized Unrealized Fair Corporate debt securities $ 501.1 $ 1.8 $ (0.1) $ 502.8 U.S. government securities 166.3 0.1 — 166.4 Commercial paper 125.2 0.1 — 125.3 Certificates of deposit and term deposits (1) 97.8 — — 97.8 Total available-for-sale securities $ 890.4 $ 2.0 $ (0.1) $ 892.3 December 31, 2019 Amortized Unrealized Unrealized Fair Corporate debt securities $ 576.1 $ 1.0 $ (0.1) $ 577.0 U.S. government securities 195.0 0.2 — 195.2 Commercial paper 148.7 0.1 — 148.8 Certificates of deposit and term deposits (1) 66.4 — — 66.4 Total available-for-sale securities $ 986.2 $ 1.3 $ (0.1) $ 987.4 (1) The majority of our certificates of deposit and term deposits are foreign deposits.
Schedule of Unrealized Loss on Investments	The following tables show the gross unrealized losses and the related fair values of our investments that have been in a continuous unrealized loss position (in millions): September 30, 2020 Less Than 12 Months 12 Months or Greater Total Fair Unrealized Fair Unrealized Fair Unrealized Corporate debt securities $ 103.9 $ — $ — $ — $ 103.9 $ — U.S. government securities 42.1 — — — 42.1 — Commercial paper 24.6 — — — 24.6 — Certificates of deposit and term deposits 17.3 (0.1) — — 17.3 (0.1) Total available-for-sale securities $ 187.9 $ (0.1) $ — $ — $ 187.9 $ (0.1) December 31, 2019 Less Than 12 Months 12 Months or Greater Total Fair Unrealized Fair Unrealized Fair Unrealized Corporate debt securities $ 117.3 $ (0.1) $ 16.1 $ — $ 133.4 $ (0.1) U.S. government securities 47.1 — — — 47.1 — Commercial paper 26.0 — — — 26.0 — Certificates of deposit and term deposits 13.0 — — — 13.0 — Total available-for-sale securities $ 203.4 $ (0.1) $ 16.1 $ — $ 219.5 $ (0.1)
Investments Classified by Contractual Maturity Date	The contractual maturities of our investments were as follows (in millions): September 30, December 31, Due within one year $ 774.4 $ 843.1 Due within one to three years 117.9 144.3 Total $ 892.3 $ 987.4
Schedule of Fair Value, Assets and Liabilities Measured on Recurring Basis	The following tables present the fair value of our financial assets measured at fair value on a recurring basis as of September 30, 2020 and December 31, 2019 (in millions): September 30, 2020 December 31, 2019 Aggregate Quoted Significant Significant Aggregate Quoted Significant Significant (Level 1) (Level 2) (Level 3) (Level 1) (Level 2) (Level 3) Assets: Corporate debt securities $ 505.9 $ — $ 505.9 $ — $ 577.0 $ — $ 577.0 $ — U.S. government securities 166.4 166.4 — — 195.2 195.2 — — Commercial paper 125.3 — 125.3 — 165.8 — 165.8 — Certificates of deposit and term deposits 97.8 — 97.8 — 66.4 — 66.4 — Money market funds 164.0 164.0 — — 15.0 15.0 — — Total $ 1,059.4 $ 330.4 $ 729.0 $ — $ 1,019.4 $ 210.2 $ 809.2 $ — Reported as: Cash equivalents $ 167.1 $ 32.0 Short-term investments 774.4 843.1 Long-term investments 117.9 144.3 Total $ 1,059.4 $ 1,019.4

Inventory (Tables)

Inventory (Tables)	9 Months Ended
	Sep. 30, 2020
Inventory Disclosure [Abstract]
Inventory	Inventory consisted of the following (in millions): September 30, December 31, Raw materials $ 15.6 $ 9.7 Finished goods 118.9 108.2 Inventory $ 134.5 $ 117.9

Property and Equipment_Net (Tab

Property and Equipment—Net (Tables)	9 Months Ended
	Sep. 30, 2020
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 $ 93.3 $ 93.3 Building and building improvements 148.1 147.4 Computer equipment and software 131.5 116.7 Leasehold improvements 30.3 25.5 Evaluation units 18.8 19.9 Furniture and fixtures 20.0 17.3 Construction-in-progress 140.8 61.2 Total property and equipment 582.8 481.3 Less: accumulated depreciation (163.4) (137.0) Property and equipment—net $ 419.4 $ 344.3

Goodwill and Other Intangible_2

Goodwill and Other Intangible Assets - Net (Tables)	9 Months Ended
	Sep. 30, 2020
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 2019 $ 67.2 Addition due to business combination 1.0 Balance—September 2020 $ 68.2
Schedule of Finite-Lived Intangible Assets by Major Class	The following tables present other intangible assets—net as of September 30, 2020 and December 31, 2019 (in millions, except years): September 30, 2020 Weighted-Average Useful Life (in Years) Gross Accumulated Amortization Net Other intangible assets—net: Finite-lived intangible assets: Developed technologies 4.0 $ 53.3 $ 30.2 $ 23.1 Customer relationships 4.1 21.8 19.6 2.2 Total other intangible assets—net $ 75.1 $ 49.8 $ 25.3 December 31, 2019 Weighted-Average Useful Life (in Years) Gross Accumulated Amortization Net Other intangible assets—net: Finite-lived intangible assets: Developed technologies 4.0 $ 50.2 $ 24.6 $ 25.6 Customer relationships 4.1 21.6 16.1 5.5 Total other intangible assets—net $ 71.8 $ 40.7 $ 31.1
Schedule of Finite-Lived Intangible Assets, Future Amortization Expense	The following table summarizes estimated future amortization expense of finite-lived intangible assets—net (in millions): Amount Years: 2020 (the remainder of 2020) $ 2.7 2021 9.6 2022 7.5 2023 4.8 2024 0.7 Total $ 25.3

Net Income Per Share (Tables)

Net Income Per Share (Tables)	9 Months Ended
	Sep. 30, 2020
Earnings Per Share [Abstract]
Schedule of Earnings Per Share, Basic and Diluted	A reconciliation of the numerator and denominator used in the calculation of basic and diluted net income per share is as follows (in millions, except per share amounts): Three Months Ended Nine Months Ended September 30, September 30, September 30, September 30, Numerator: Net income $ 123.4 $ 80.2 $ 341.8 $ 213.5 Denominator: Basic shares: Weighted-average common stock outstanding-basic 162.1 171.3 164.8 170.9 Diluted shares: Weighted-average common stock outstanding-basic 162.1 171.3 164.8 170.9 Effect of potentially dilutive securities: RSUs 2.3 2.4 2.4 2.9 Stock options 1.2 1.1 1.2 1.1 Weighted-average shares used to compute diluted net income per share 165.6 174.8 168.4 174.9 Net income per share: Basic $ 0.76 $ 0.47 $ 2.07 $ 1.25 Diluted $ 0.75 $ 0.46 $ 2.03 $ 1.22
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 0.3 0.2 0.3 0.3 Stock options 0.6 0.7 0.5 0.6 Total 0.9 0.9 0.8 0.9

Leases (Tables)

Leases (Tables)	9 Months Ended
	Sep. 30, 2020
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 $ 4.8 $ 3.8 $ 13.5 $ 11.1 Variable lease expense (1) 0.7 0.7 1.7 1.9 Short-term lease expense 1.0 0.8 2.9 2.2 Total lease expense $ 6.5 $ 5.3 $ 18.1 $ 15.2 (1) Variable lease expense for the nine months ended September 30, 2020 and September 30, 2019 predominantly included common area maintenance charges and parking expense. Supplemental cash flow information related to leases was as follows (in millions): Nine Months Ended 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 $ 13.8 $ 11.9
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 $ 45.6 $ 44.3 Operating lease liabilities - current Accrued liabilities $ 17.2 $ 15.5 Operating lease liabilities - non-current Other liabilities 31.0 30.6 Total operating lease liabilities $ 48.2 $ 46.1 Weighted average remaining lease term in years - operating leases 3.6 3.7 Weighted average discount rate - operating leases 3.2 % 2.8 %
Maturities of Operating Lease Liabilities	Maturities of operating lease liabilities as of September 30, 2020 were as follows (in millions): Year ending December 31, Amount 2020 (the remainder of 2020) $ 4.2 2021 17.8 2022 12.6 2023 7.2 2024 5.3 Thereafter 4.0 Total lease payments 51.1 Less imputed interest (2.9) Total $ 48.2

Commitments and Contingencies (

Commitments and Contingencies (Tables)	9 Months Ended
	Sep. 30, 2020
Commitments and Contingencies Disclosure [Abstract]
Inventory Purchase Commitments, Fiscal Year Maturity Schedule	The following table summarizes our inventory purchase commitments as of September 30, 2020 (in millions): Total 2020 2021 2022 2023 2024 Thereafter Inventory purchase commitments $ 284.7 $ 207.6 $ 77.1 $ — $ — $ — $ —

Stockholders' Equity (Tables)

Stockholders' Equity (Tables)	9 Months Ended
	Sep. 30, 2020
Share-based Payment Arrangement [Abstract]
Schedule of Share-based Compensation, Restricted Stock Units Award Activity	The following table summarizes the activity and related information for 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, 2019 6.1 $ 64.56 Granted 1.8 121.30 Forfeited (0.3) 76.80 Vested (2.3) 57.07 Balance—September 30, 2020 5.3 $ 86.31
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 0.2 0.2 0.7 0.9 Amount withheld for taxes $ 27.6 $ 19.6 $ 86.5 $ 76.1
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 39.9 % 35.3 % 34.6 % 34.2 % Risk-free interest rate 0.2 % 1.4 % 1.1 % 2.4 % 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, 2019 2.7 $ 50.37 Granted 0.6 118.96 Forfeited (0.1) 91.73 Exercised (0.4) 40.99 Balance—September 30, 2020 2.8 $ 66.72 Options vested and expected to vest—September 30, 2020 2.8 $ 66.72 4.4 $ 146.4 Options exercisable—September 30, 2020 1.5 $ 42.81 3.3 $ 109.6
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 $ 43.80 $ 24.97 $ 35.76 $ 26.96 Intrinsic value of options exercised 5.5 3.2 35.8 40.1 Fair value of options vested 2.5 2.0 10.9 8.2
Schedule of Employee Service Share-based Compensation, Allocation of Recognized Period Costs	Stock-based compensation expense, including stock-based compensation expense related to awards classified as liabilities, is included in costs and expenses as follows (in millions): Three Months Ended Nine Months Ended September 30, September 30, September 30, September 30, Cost of product revenue $ 0.4 $ 0.4 $ 1.2 $ 1.2 Cost of service revenue 3.3 2.7 9.5 8.4 Research and development 12.7 9.3 35.6 28.7 Sales and marketing 27.7 24.9 81.3 76.6 General and administrative 5.9 5.1 17.3 15.5 Total stock-based compensation expense $ 50.0 $ 42.4 $ 144.9 $ 130.4
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 $ 46.4 $ 39.5 $ 134.5 $ 120.6 Stock options 3.6 2.9 10.4 8.5 ESPP — — — 1.3 Total stock-based compensation expense $ 50.0 $ 42.4 $ 144.9 $ 130.4
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 $ 11.0 $ 9.8 $ 31.9 $ 30.1

Segment Information (Tables)

Segment Information (Tables)	9 Months Ended
	Sep. 30, 2020
Segment Reporting [Abstract]
Revenue From External Customers by Geographic Region	Revenue by geographic region is based on the billing address of our customers. The following tables set forth revenue and property and equipment—net by geographic region (in millions): Three Months Ended Nine Months Ended Revenue September 30, September 30, September 30, September 30, Americas: United States $ 206.0 $ 182.3 $ 589.1 $ 506.9 Other Americas 66.4 58.7 186.9 161.1 Total Americas 272.4 241.0 776.0 668.0 Europe, Middle East and Africa (“EMEA”) 243.3 200.9 693.5 571.1 Asia Pacific (“APAC”) 135.4 106.2 376.9 305.8 Total revenue $ 651.1 $ 548.1 $ 1,846.4 $ 1,544.9
Property and Equipment by Geographic Region	Property and Equipment — net September 30, December 31, Americas: United States $ 270.9 $ 197.4 Canada 121.3 120.5 Latin America 6.9 5.5 Total Americas 399.1 323.4 EMEA 15.3 15.2 APAC 5.0 5.7 Total property and equipment—net $ 419.4 $ 344.3
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”) 29 % 30 % 30 % 31 % Ingram Micro, Inc. (“Ingram Micro”) 10 % 11 % 10 % 11 % The following distributors accounted for 10% or more of net accounts receivable: September 30, December 31, Exclusive 31 % 36 % Ingram Micro 11 % 10 % Tech Data Corporation 10 % * * Represents less than 10%

Immaterial Correction of Prio_3

Immaterial Correction of Prior Period Financial Statements - Balance Sheet (Details) - USD ($) $ in Millions	Sep. 30, 2020	Jun. 30, 2020	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Dec. 31, 2018
ASSETS
DEFERRED TAX ASSETS	$ 230.1		$ 226.3
TOTAL ASSETS	3,586.2		3,879.2
CURRENT LIABILITIES:
Deferred revenue	1,300		1,155.8
Total current liabilities	1,645.6		1,455.8
DEFERRED REVENUE	1,092		953.3
Total liabilities	2,873		2,536.8
Retained earnings (accumulated deficit)	(466.9)		160.8
Total stockholders’ equity	713.2	$ 566.7	1,342.4	$ 1,217.9	$ 1,139.4	$ 1,025.5
TOTAL LIABILITIES AND STOCKHOLDERS’ EQUITY	$ 3,586.2		3,879.2
As Previously Reported [Member]
ASSETS
DEFERRED TAX ASSETS			232.6
TOTAL ASSETS			3,885.5
CURRENT LIABILITIES:
Deferred revenue			1,173.6
Total current liabilities			1,473.6
DEFERRED REVENUE			962.3
Total liabilities			2,563.6
Retained earnings (accumulated deficit)			140.3
Total stockholders’ equity			1,321.9
TOTAL LIABILITIES AND STOCKHOLDERS’ EQUITY			3,885.5
Corrections [Member]
ASSETS
DEFERRED TAX ASSETS			(6.3)
TOTAL ASSETS			(6.3)
CURRENT LIABILITIES:
Deferred revenue			(17.8)
Total current liabilities			(17.8)
DEFERRED REVENUE			(9)
Total liabilities			(26.8)
Retained earnings (accumulated deficit)			20.5
Total stockholders’ equity			20.5
TOTAL LIABILITIES AND STOCKHOLDERS’ EQUITY			$ (6.3)

Immaterial Correction of Prio_4

Immaterial Correction of Prior Period Financial Statements - Income Statement (Details) - USD ($) $ / shares in Units, $ in Millions	3 Months Ended				9 Months Ended
	Sep. 30, 2020	Jun. 30, 2020	Mar. 31, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
REVENUE:
Total revenue	$ 651.1			$ 548.1	$ 1,846.4	$ 1,544.9
GROSS PROFIT:
Gross Profit	511.9			424	1,443.4	1,179.5
OPERATING INCOME	126.9			100.6	362.4	228.9
INCOME BEFORE INCOME TAXES	128.4			106	370	254.6
PROVISION FOR INCOME TAXES	5			25.8	28.2	41.1
NET INCOME	$ 123.4			$ 80.2	$ 341.8	$ 213.5
Net income per share (Note 10):
Basic (in dollars per share)	$ 0.76			$ 0.47	$ 2.07	$ 1.25
Diluted (in dollars per share)	$ 0.75			$ 0.46	$ 2.03	$ 1.22
As Previously Reported [Member]
REVENUE:
Total revenue				$ 547.5		$ 1,541.8
GROSS PROFIT:
Gross Profit				423.4		1,176.4
OPERATING INCOME				100		225.8
INCOME BEFORE INCOME TAXES				105.4		251.5
PROVISION FOR INCOME TAXES				25.6		40.2
NET INCOME				$ 79.8		$ 211.3
Net income per share (Note 10):
Basic (in dollars per share)				$ 0.47		$ 1.24
Diluted (in dollars per share)				$ 0.46		$ 1.21
Corrections [Member]
REVENUE:
Total revenue		$ 2.1	$ 0.8	$ 0.6		$ 3.1
GROSS PROFIT:
Gross Profit		2.1	0.8	0.6		3.1
OPERATING INCOME		2.1	0.8	0.6		3.1
INCOME BEFORE INCOME TAXES				0.6		3.1
PROVISION FOR INCOME TAXES				0.2		0.9
NET INCOME		$ 1.7	$ 0.6	$ 0.4		$ 2.2
Net income per share (Note 10):
Basic (in dollars per share)				$ 0		$ 0.01
Diluted (in dollars per share)		$ 0.01	$ 0	$ 0		$ 0.01
Service [Member]
REVENUE:
Total revenue	$ 427.3			$ 351	$ 1,218.4	$ 995.2
GROSS PROFIT:
Gross Profit	$ 372.4			305.9	$ 1,060.4	861.7
Service [Member] | As Previously Reported [Member]
REVENUE:
Total revenue				350.4		992.1
GROSS PROFIT:
Gross Profit				305.3		858.6
Service [Member] | Corrections [Member]
REVENUE:
Total revenue				0.6		3.1
GROSS PROFIT:
Gross Profit				$ 0.6		$ 3.1

Immaterial Correction of Prio_5

Immaterial Correction of Prior Period Financial Statements - Cash Flows (Details) - USD ($) $ in Millions	3 Months Ended				9 Months Ended
	Sep. 30, 2020	Jun. 30, 2020	Mar. 31, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
CASH FLOWS FROM OPERATING ACTIVITIES:
Net income	$ 123.4			$ 80.2	$ 341.8	$ 213.5
Adjustments to Reconcile Net Income (Loss) to Cash Provided by (Used in) Operating Activities [Abstract]
Deferred tax assets					4.4	11.5
Deferred revenue					282.6	255.7
Net cash provided by operating activities					$ 787.2	617.6
As Previously Reported [Member]
CASH FLOWS FROM OPERATING ACTIVITIES:
Net income				79.8		211.3
Adjustments to Reconcile Net Income (Loss) to Cash Provided by (Used in) Operating Activities [Abstract]
Deferred tax assets						10.6
Deferred revenue						258.8
Net cash provided by operating activities						617.6
Corrections [Member]
CASH FLOWS FROM OPERATING ACTIVITIES:
Net income		$ 1.7	$ 0.6	$ 0.4		2.2
Adjustments to Reconcile Net Income (Loss) to Cash Provided by (Used in) Operating Activities [Abstract]
Deferred tax assets						0.9
Deferred revenue						(3.1)
Net cash provided by operating activities						$ 0

Immaterial Correction of Prio_6

Immaterial Correction of Prior Period Financial Statements - Narrative (Details) - USD ($) $ / shares in Units, $ in Millions	3 Months Ended				9 Months Ended
	Sep. 30, 2020	Jun. 30, 2020	Mar. 31, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Error Corrections and Prior Period Adjustments Restatement [Line Items]
Total revenue	$ 651.1			$ 548.1	$ 1,846.4	$ 1,544.9
Gross Profit	511.9			424	1,443.4	1,179.5
OPERATING INCOME	126.9			100.6	362.4	228.9
Net income	$ 123.4			$ 80.2	$ 341.8	$ 213.5
Diluted net income per share (in dollars per share)	$ 0.75			$ 0.46	$ 2.03	$ 1.22
Corrections [Member]
Error Corrections and Prior Period Adjustments Restatement [Line Items]
Total revenue		$ 2.1	$ 0.8	$ 0.6		$ 3.1
Gross Profit		2.1	0.8	0.6		3.1
OPERATING INCOME		2.1	0.8	0.6		3.1
Net income		$ 1.7	$ 0.6	$ 0.4		$ 2.2
Diluted net income per share (in dollars per share)		$ 0.01	$ 0	$ 0		$ 0.01

Revenue Recognition - Disaggreg

Revenue Recognition - Disaggregated Revenues (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Disaggregation of Revenue [Line Items]
Total revenue	$ 651.1	$ 548.1	$ 1,846.4	$ 1,544.9
Product [Member]
Disaggregation of Revenue [Line Items]
Total revenue	223.8	197.1	628	549.7
Service [Member]
Disaggregation of Revenue [Line Items]
Total revenue	427.3	351	1,218.4	995.2
Security Subscription [Member]
Disaggregation of Revenue [Line Items]
Total revenue	235.4	192.8	669.4	545.5
Technical Support and Other [Member]
Disaggregation of Revenue [Line Items]
Total revenue	$ 191.9	$ 158.2	$ 549	$ 449.7

Revenue Recognition (Details)

Revenue Recognition (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019	Dec. 31, 2019
Disaggregation of Revenue [Line Items]
Remaining performance obligation	$ 2,390		$ 2,390
Threshold period past due	60 days		60 days
Allowance for credit losses	$ 2.2		$ 2.2		$ 1.2
Amortization of deferred contract costs	35.3	$ 27.5	99.8	$ 78.5
Service [Member]
Disaggregation of Revenue [Line Items]
Deferred revenue recognized in period	$ 263.1	$ 211.8	$ 921.7	$ 754.5

Revenue Recognition - Performan

Revenue Recognition - Performance Obligation Satisfaction Period (Details) $ in Millions	Sep. 30, 2020USD ($)
Revenue from Contract with Customer [Abstract]
Remaining performance obligation	$ 2,390
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2020-10-01
Revenue from Contract with Customer [Abstract]
Remaining performance obligation	$ 1,300
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Performance obligation expected recognition period for three-fourths of remaining obligation	12 months
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2021-10-01
Revenue from Contract with Customer [Abstract]
Remaining performance obligation	$ 1,090
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, 2020	Dec. 31, 2019
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	$ 890.4	$ 986.2
Unrealized Gains	2	1.3
Unrealized Losses	(0.1)	(0.1)
Fair Value	892.3	987.4
Available-for-sale Securities, Continuous Unrealized Loss Position [Abstract]
Less Than 12 Months, Fair Value	187.9	203.4
Less Than 12 Months, Unrealized Losses	(0.1)	(0.1)
12 Months or Greater, Fair Value	0	16.1
12 Months or Greater, Unrealized Losses	0	0
Total, Fair Value	187.9	219.5
Total, Unrealized Losses	(0.1)	(0.1)
Available-for-sale Securities, Debt Maturities, Fair Value [Abstract]
Due within one year	774.4	843.1
Due within one to three years	117.9	144.3
Fair Value	892.3	987.4
Corporate debt securities [Member]
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	501.1	576.1
Unrealized Gains	1.8	1
Unrealized Losses	(0.1)	(0.1)
Fair Value	502.8	577
Available-for-sale Securities, Continuous Unrealized Loss Position [Abstract]
Less Than 12 Months, Fair Value	103.9	117.3
Less Than 12 Months, Unrealized Losses	0	(0.1)
12 Months or Greater, Fair Value	0	16.1
12 Months or Greater, Unrealized Losses	0	0
Total, Fair Value	103.9	133.4
Total, Unrealized Losses	0	(0.1)
Available-for-sale Securities, Debt Maturities, Fair Value [Abstract]
Fair Value	502.8	577
Commercial paper [Member]
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	125.2	148.7
Unrealized Gains	0.1	0.1
Unrealized Losses	0	0
Fair Value	125.3	148.8
Available-for-sale Securities, Continuous Unrealized Loss Position [Abstract]
Less Than 12 Months, Fair Value	24.6	26
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	24.6	26
Total, Unrealized Losses	0	0
Available-for-sale Securities, Debt Maturities, Fair Value [Abstract]
Fair Value	125.3	148.8
Certificates of deposit and term deposits [Member]
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	97.8	66.4
Unrealized Gains	0	0
Unrealized Losses	0	0
Fair Value	97.8	66.4
Available-for-sale Securities, Continuous Unrealized Loss Position [Abstract]
Less Than 12 Months, Fair Value	17.3	13
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	17.3	13
Total, Unrealized Losses	(0.1)	0
Available-for-sale Securities, Debt Maturities, Fair Value [Abstract]
Fair Value	97.8	66.4
U.S. government securities [Member]
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	166.3	195
Unrealized Gains	0.1	0.2
Unrealized Losses	0	0
Fair Value	166.4	195.2
Available-for-sale Securities, Continuous Unrealized Loss Position [Abstract]
Less Than 12 Months, Fair Value	42.1	47.1
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	42.1	47.1
Total, Unrealized Losses	0	0
Available-for-sale Securities, Debt Maturities, Fair Value [Abstract]
Fair Value	$ 166.4	$ 195.2

Financial Instruments and Fai_4

Financial Instruments and Fair Value , Additional Information (Details) $ in Millions	Sep. 30, 2020USD ($)
Financial Instruments and Fair Value [Abstract]
Accrued interest on available-for-sale securities	$ 3.2

Financial Instruments and Fai_5

Financial Instruments and Fair Value , Fair Value Measurements (Details) - USD ($) $ in Millions	Sep. 30, 2020	Dec. 31, 2019
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value	$ 892.3	$ 987.4
Corporate debt securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value	502.8	577
U.S. government securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value	166.4	195.2
Commercial paper [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value	125.3	148.8
Certificates of deposit and term deposits [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value	97.8	66.4
Recurring Basis [Member] | Fair Value [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total Assets, Fair Value Disclosure	1,059.4	1,019.4
Recurring Basis [Member] | Fair Value [Member] | Level 1 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total Assets, Fair Value Disclosure	330.4	210.2
Recurring Basis [Member] | Fair Value [Member] | Level 2 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total Assets, Fair Value Disclosure	729	809.2
Recurring Basis [Member] | Fair Value [Member] | Level 3 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total Assets, Fair Value Disclosure	0	0
Recurring Basis [Member] | Fair Value [Member] | Corporate debt securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value	505.9	577
Recurring Basis [Member] | Fair Value [Member] | Corporate debt securities [Member] | Level 1 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value	0	0
Recurring Basis [Member] | Fair Value [Member] | Corporate debt securities [Member] | Level 2 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value	505.9	577
Recurring Basis [Member] | Fair Value [Member] | Corporate debt securities [Member] | Level 3 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value	0	0
Recurring Basis [Member] | Fair Value [Member] | U.S. government securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value	166.4	195.2
Recurring Basis [Member] | Fair Value [Member] | U.S. government securities [Member] | Level 1 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value	166.4	195.2
Recurring Basis [Member] | Fair Value [Member] | U.S. government securities [Member] | Level 2 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value	0	0
Recurring Basis [Member] | Fair Value [Member] | U.S. government securities [Member] | Level 3 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value	0	0
Recurring Basis [Member] | Fair Value [Member] | Commercial paper [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value	125.3	165.8
Recurring Basis [Member] | Fair Value [Member] | Commercial paper [Member] | Level 1 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value	0	0
Recurring Basis [Member] | Fair Value [Member] | Commercial paper [Member] | Level 2 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value	125.3	165.8
Recurring Basis [Member] | Fair Value [Member] | Commercial paper [Member] | Level 3 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value	0	0
Recurring Basis [Member] | Fair Value [Member] | Certificates of deposit and term deposits [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value	97.8	66.4
Recurring Basis [Member] | Fair Value [Member] | Certificates of deposit and term deposits [Member] | Level 1 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value	0	0
Recurring Basis [Member] | Fair Value [Member] | Certificates of deposit and term deposits [Member] | Level 2 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value	97.8	66.4
Recurring Basis [Member] | Fair Value [Member] | Certificates of deposit and term deposits [Member] | Level 3 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value	0	0
Recurring Basis [Member] | Fair Value [Member] | Money market funds [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value	164	15
Recurring Basis [Member] | Fair Value [Member] | Money market funds [Member] | Level 1 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value	164	15
Recurring Basis [Member] | Fair Value [Member] | Money market funds [Member] | Level 2 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value	0	0
Recurring Basis [Member] | Fair Value [Member] | Money market funds [Member] | Level 3 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value	0	0
Recurring Basis [Member] | Reported as [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total Assets, Fair Value Disclosure	1,059.4	1,019.4
Recurring Basis [Member] | Reported as [Member] | Cash equivalents [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value	167.1	32
Recurring Basis [Member] | Reported as [Member] | Short-term investments [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value	774.4	843.1
Recurring Basis [Member] | Reported as [Member] | Long-term investments [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value	$ 117.9	$ 144.3

Inventory (Details)

Inventory (Details) - USD ($) $ in Millions	Sep. 30, 2020	Dec. 31, 2019
Inventory, Net [Abstract]
Raw materials	$ 15.6	$ 9.7
Finished goods	118.9	108.2
Inventory	$ 134.5	$ 117.9

Property and Equipment_Net (Det

Property and Equipment—Net (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019	Dec. 31, 2019
Property, Plant and Equipment, Net, by Type [Abstract]
Total property and equipment	$ 582.8		$ 582.8		$ 481.3
Less: accumulated depreciation	(163.4)		(163.4)		(137)
Property and equipment—net	419.4		419.4		344.3
Depreciation expense	13.9	$ 12.8	41.6	$ 37.8
Land [Member]
Property, Plant and Equipment, Net, by Type [Abstract]
Total property and equipment	93.3		93.3		93.3
Building and building improvements [Member]
Property, Plant and Equipment, Net, by Type [Abstract]
Total property and equipment	148.1		148.1		147.4
Computer equipment and software [Member]
Property, Plant and Equipment, Net, by Type [Abstract]
Total property and equipment	131.5		131.5		116.7
Leasehold improvements [Member]
Property, Plant and Equipment, Net, by Type [Abstract]
Total property and equipment	30.3		30.3		25.5
Evaluation units [Member]
Property, Plant and Equipment, Net, by Type [Abstract]
Total property and equipment	18.8		18.8		19.9
Furniture and fixtures [Member]
Property, Plant and Equipment, Net, by Type [Abstract]
Total property and equipment	20		20		17.3
Construction-in-progress [Member]
Property, Plant and Equipment, Net, by Type [Abstract]
Total property and equipment	$ 140.8		$ 140.8		$ 61.2

Investments in Privately-Held_2

Investments in Privately-Held Companies (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2020	Sep. 30, 2019	Sep. 30, 2020	Dec. 31, 2019
Investments, All Other Investments [Abstract]
Investments in equity securities of privately-held companies			$ 1	$ 5.3
Non-cash impairment charge	$ 4.3	$ 3.8
Cumulative impairment adjustments to all equity securities without readily determinable fair values			$ 8.1

Business Combinations - Additio

Business Combinations - Additional Information (Details) - USD ($) $ in Millions	Jul. 20, 2020	Sep. 30, 2020	Dec. 31, 2019
Business Acquisition [Line Items]
Goodwill		$ 68.2	$ 67.2
OPAQ Networks, Inc (OPAQ) [Member]
Business Acquisition [Line Items]
Preliminary purchase price	$ 8
Goodwill	1
Identifiable intangible assets	4.7
Other net assets acquired	2.3
Amount held in indemnity escrow, expected to be held for 12 months	$ 1.3

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, 2020USD ($)
Goodwill [Roll Forward]
Balance - beginning of period	$ 67.2
Addition due to business combination	1
Balance - end of period	$ 68.2

Goodwill and Other Intangible_4

Goodwill and Other Intangible Assets - Net - Narrative (Details) - USD ($)	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Goodwill and Intangible Assets Disclosure [Abstract]
Goodwill impairment	$ 0	$ 0	$ 0	$ 0
Amortization expense	$ 2,800,000	$ 2,200,000	$ 10,500,000	$ 8,100,000

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, 2020	Dec. 31, 2019
Finite-Lived Intangible Assets, Net [Abstract]
Gross	$ 75.1	$ 71.8
Accumulated Amortization	49.8	40.7
Total	$ 25.3	$ 31.1
Developed Technologies [Member]
Finite-Lived Intangible Assets [Line Items]
Weighted average useful life	4 years	4 years
Finite-Lived Intangible Assets, Net [Abstract]
Gross	$ 53.3	$ 50.2
Accumulated Amortization	30.2	24.6
Total	$ 23.1	$ 25.6
Customer Relationships [Member]
Finite-Lived Intangible Assets [Line Items]
Weighted average useful life	4 years 1 month 6 days	4 years 1 month 6 days
Finite-Lived Intangible Assets, Net [Abstract]
Gross	$ 21.8	$ 21.6
Accumulated Amortization	19.6	16.1
Total	$ 2.2	$ 5.5

Goodwill and Other Intangible_6

Goodwill and Other Intangible Assets - Net - Estimated Future Amortization Expense (Details) - USD ($) $ in Millions	Sep. 30, 2020	Dec. 31, 2019
Fiscal Years:
2020 (the remainder of 2020)	$ 2.7
2021	9.6
2022	7.5
2023	4.8
2024	0.7
Total	$ 25.3	$ 31.1

Net Income Per Share , Calculat

Net Income Per Share , Calculation of Basic and Diluted (Details) - USD ($) $ / shares in Units, shares in Millions, $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Earnings Per Share [Line Items]
Net income	$ 123.4	$ 80.2	$ 341.8	$ 213.5
Basic shares:
Weighted-average common shares outstanding-basic (in shares)	162.1	171.3	164.8	170.9
Diluted shares:
Weighted-average common shares outstanding-basic (in shares)	162.1	171.3	164.8	170.9
Effect of potentially dilutive securities:
Weighted-average shares used to compute diluted net income per share (in shares)	165.6	174.8	168.4	174.9
Net income per share:
Basic (in dollars per share)	$ 0.76	$ 0.47	$ 2.07	$ 1.25
Diluted (in dollars per share)	$ 0.75	$ 0.46	$ 2.03	$ 1.22
Restricted Stock Units (RSUs) [Member]
Effect of potentially dilutive securities:
RSUs and stock options (in shares)	2.3	2.4	2.4	2.9
Stock Options [Member]
Effect of potentially dilutive securities:
RSUs and stock options (in shares)	1.2	1.1	1.2	1.1

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, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Anti-dilutive securities (in shares)	0.9	0.9	0.8	0.9
Restricted Stock Units (RSUs) [Member] | Share-based Payment Arrangement [Member]
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Anti-dilutive securities (in shares)	0.3	0.2	0.3	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)	0.6	0.7	0.5	0.6

Leases (Details)

Leases (Details) - USD ($) $ in Millions	9 Months Ended	12 Months Ended
	Sep. 30, 2020	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	$ 3.8
Minimum [Member]
Lessee, Lease, Description [Line Items]
Remaining terms (less than for minimum)	1 year
Lease not yet commenced, approximate term	3 years
Maximum [Member]
Lessee, Lease, Description [Line Items]
Remaining terms (less than for minimum)	7 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, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Leases [Abstract]
Operating lease expense	$ 4.8	$ 3.8	$ 13.5	$ 11.1
Variable lease expense	0.7	0.7	1.7	1.9
Short-term lease expense	1	0.8	2.9	2.2
Total lease expense	$ 6.5	$ 5.3	$ 18.1	$ 15.2

Leases - Supplemental Balance S

Leases - Supplemental Balance Sheet Information (Details) - USD ($) $ in Millions	Sep. 30, 2020	Dec. 31, 2019
Leases [Abstract]
Operating Lease, Right-of-Use Asset, Statement of Financial Position [Extensible List]	us-gaap:OtherAssets	us-gaap:OtherAssets
Operating lease ROU assets - non-current	$ 45.6	$ 44.3
Operating Lease, Liability, Current, Statement of Financial Position [Extensible List]	us-gaap:AccountsPayableAndAccruedLiabilitiesCurrent	us-gaap:AccountsPayableAndAccruedLiabilitiesCurrent
Operating lease liabilities - current	$ 17.2	$ 15.5
Operating Lease, Liability, Noncurrent, Statement of Financial Position [Extensible List]	us-gaap:OtherLiabilitiesNoncurrent	us-gaap:OtherLiabilitiesNoncurrent
Operating lease liabilities - non-current	$ 31	$ 30.6
Total operating lease liabilities	$ 48.2	$ 46.1
Weighted average remaining lease term in years - operating leases	3 years 7 months 6 days	3 years 8 months 12 days
Weighted average discount rate - operating leases	3.20%	2.80%

Leases - Supplemental Cash Flow

Leases - Supplemental Cash Flow Information (Details) - USD ($) $ in Millions	9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019
Cash paid for amounts included in the measurement of lease liabilities
Operating cash flows used for operating leases	$ 13.8	$ 11.9

Leases - Maturities of Operatin

Leases - Maturities of Operating Lease Liabilities (Details) - USD ($) $ in Millions	Sep. 30, 2020	Dec. 31, 2019
Leases [Abstract]
2020 (the remainder of 2020)	$ 4.2
2021	17.8
2022	12.6
2023	7.2
2024	5.3
Thereafter	4
Total lease payments	51.1
Less imputed interest	(2.9)
Total	$ 48.2	$ 46.1

Mutual Covenant-Not-to-Sue an_2

Mutual Covenant-Not-to-Sue and Release Agreement (Details) - USD ($)	1 Months Ended	3 Months Ended		9 Months Ended
	Jan. 31, 2020	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Mutual Covenant-Not-to-Sue Agreement [Abstract]
Proceeds from mutual covenant-not-to-sue agreement	$ 50,000,000
Initial term	7 years
Extension term	7 years
Additional proceeds if extended	$ 50,000,000
Contractual term	14 years
Total proceeds if extension option utilized	$ 100,000,000
Amount allocated to functional component	36,000,000
Amount representing the right to utilize future patents	$ 64,000,000
Gain on IP matter		$ 1,100,000	$ 0	$ 39,000,000	$ 0
Amount recorded in Accrued liabilities and Other liabilities in condensed consolidated balance sheet		$ 11,000,000		$ 11,000,000

Commitments and Contingencies -

Commitments and Contingencies - Inventory Purchase Commitments (Details) $ in Millions	Sep. 30, 2020USD ($)
Inventory purchase commitments:
Inventory purchase commitments	$ 284.7
Inventory purchase commitments, 2020	207.6
Inventory purchase commitments, 2021	77.1
Inventory purchase commitments, 2022	0
Inventory purchase commitments, 2023	0
Inventory purchase commitments, 2024	0
Inventory purchase commitments, Thereafter	$ 0

Commitments and Contingencies_2

Commitments and Contingencies (Details) $ in Millions	Sep. 30, 2020USD ($)
Commitments and Contingencies Disclosure [Abstract]
Inventory purchase commitments	$ 284.7
Other contractual commitments and open purchase orders	$ 23.1

Stockholders' Equity , Restrict

Stockholders' Equity , Restricted Stock Units Activity (Details) - USD ($) $ / shares in Units, shares in Millions, $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Weighted-Average Grant Date Fair Value per Share
Shares withheld for taxes	0.2	0.2	0.7	0.9
Amount withheld for taxes	$ 27.6	$ 19.6	$ 86.5	$ 76.1
Stock-based Compensation Plan [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Remaining shares available for grant under the plans	12.1		12.1
Restricted Stock Units (RSUs) [Member]
Number of Shares
Balance, beginning (shares)			6.1
Granted (shares)			1.8
Forfeited (shares)			(0.3)
Vested (shares)			(2.3)
Balance, ending (shares)	5.3		5.3
Weighted-Average Grant Date Fair Value per Share
Balance, beginning (in dollars per share)			$ 64.56
Granted (in dollars per share)			121.30
Forfeited (in dollars per share)			76.80
Vested (in dollars per share)			57.07
Balance, ending (in dollars per share)	$ 86.31		$ 86.31
Compensation cost not yet recognized	$ 399.1		$ 399.1
Compensation cost not yet recognized period of recognition			2 years 8 months 12 days

Stockholders' Equity - Employee

Stockholders' Equity - Employee Stock Options (Details) - Stock Options [Member] - USD ($) $ / shares in Units, shares in Millions, $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Share-based Compensation Arrangement by Share-based Payment Award, Fair Value Assumptions and Methodology [Abstract]
Expected term in years	4 years 4 months 24 days	4 years 4 months 24 days	4 years 4 months 24 days	4 years 4 months 24 days
Volatility	39.90%	35.30%	34.60%	34.20%
Risk-free interest rate	0.20%	1.40%	1.10%	2.40%
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
Weighted- Average Exercise Price
Balance - Beginning (in dollars per share)			$ 50.37
Granted (in dollars per share)			118.96
Forfeited (in dollars per share)			91.73
Exercised (in dollars per share)			40.99
Balance - Ending (in dollars per share)	$ 66.72		$ 66.72
Share-based Compensation Arrangement by Share-based Payment Award, Options, Additional Disclosures [Abstract]
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)	$ 66.72		$ 66.72
Options vested and expected to vest, Weighted average remaining contractual life (in years)			4 years 4 months 24 days
Options vested and expected to vest, Aggregate intrinsic value	$ 146.4		$ 146.4
Options exercisable, Outstanding (in shares)	1.5		1.5
Options exercisable, Weighted average exercise price (in dollars per share)	$ 42.81		$ 42.81
Options exercisable, Weighted average remaining contractual life (in years)			3 years 3 months 18 days
Options exercisable, Aggregate intrinsic value	$ 109.6		$ 109.6
Compensation cost not yet recognized	$ 35.1		$ 35.1
Compensation cost not yet recognized period of recognition			2 years 9 months 18 days
Weighted-average fair value per share granted	$ 43.80	$ 24.97	$ 35.76	$ 26.96
Intrinsic value of options exercised	$ 5.5	$ 3.2	$ 35.8	$ 40.1
Fair value of options vested	$ 2.5	$ 2	$ 10.9	$ 8.2

Stockholders' Equity , Allocati

Stockholders' Equity , Allocation of Stock-Based Compensation Expense (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]
Total stock-based compensation expense	$ 50	$ 42.4	$ 144.9	$ 130.4
Income tax benefit associated with stock-based compensation	11	9.8	31.9	30.1
Restricted Stock Units (RSUs) [Member]
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]
Total stock-based compensation expense	46.4	39.5	134.5	120.6
Stock Options [Member]
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]
Total stock-based compensation expense	3.6	2.9	10.4	8.5
ESPP [Member]
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]
Total stock-based compensation expense	0	0	0	1.3
Cost of product revenue [Member]
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]
Total stock-based compensation expense	0.4	0.4	1.2	1.2
Cost of service revenue [Member]
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]
Total stock-based compensation expense	3.3	2.7	9.5	8.4
Research and development [Member]
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]
Total stock-based compensation expense	12.7	9.3	35.6	28.7
Sales and marketing [Member]
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]
Total stock-based compensation expense	27.7	24.9	81.3	76.6
General and administrative [Member]
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]
Total stock-based compensation expense	$ 5.9	$ 5.1	$ 17.3	$ 15.5

Stockholders' Equity , Share Re

Stockholders' Equity , Share Repurchase Program (Details) - USD ($) $ / shares in Units, shares in Millions	1 Months Ended	3 Months Ended	9 Months Ended
	Jul. 31, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Share Repurchase Program [Line Items]
Stock repurchased in the period, aggregate purchase price		$ 26,500,000	$ 1,046,000,000	$ 117,400,000
Repurchase Program [Member]
Share Repurchase Program [Line Items]
Increase in authorized stock repurchase amount	$ 500,000,000
Stock repurchase program, authorized amount	$ 3,000,000,000
Stock repurchased in the period (in shares)			11.4
Stock repurchased, average price (in dollars per share)			$ 91.55
Stock repurchased in the period, aggregate purchase price			$ 1,050,000,000
Stock repurchase program, unused balance			$ 1,050,000,000

Income Taxes , Narrative (Detai

Income Taxes , Narrative (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019	Dec. 31, 2019
Income Tax Disclosure [Abstract]
Effective tax rate (percent)	4.00%	24.00%	8.00%	16.00%
U.S. federal and state taxes, withholding taxes and foreign taxes	$ 17.5	$ 32.7	$ 74.8	$ 75.4
Tax benefit from foreign-derived intangible income deduction	16		25.6
Excess tax benefits on stock compensation	12.5	$ 6.9	37.6	34.6
Unrecognized tax benefits and related interest release due to expiration of statute of limitations			9	10
Increase in tax expense related to unrecognized tax benefit from Ninth Circuit Altera decision				$ 10.3
Unrecognized tax benefits	67.1		67.1		$ 67.5
Unrecognized tax benefits that would favorably affect effective tax rate	61.7		61.7
Accrued interest and penalties related to uncertain tax benefits	13.1		13.1		$ 14.1
Possible decrease in unrecognized tax benefits (up to)	$ 4		$ 4

Defined Contribution Plans (Det

Defined Contribution Plans (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Retirement Benefits [Abstract]
Matching contribution on employee contributions, Percent			50.00%
Maximum contribution percentage of each employee's eligible earnings, Percent			4.00%
Matching contributions to the RRSP and 401(k) Plans	$ 2.1	$ 1.8	$ 6.5	$ 5.2

Segment Information (Details)

Segment Information (Details) $ in Millions	3 Months Ended		9 Months Ended		12 Months Ended
	Sep. 30, 2020USD ($)	Sep. 30, 2019USD ($)	Sep. 30, 2020USD ($)operating_segmentsegment_managerreportable_segmentbusiness_activity	Sep. 30, 2019USD ($)	Dec. 31, 2019USD ($)
Segment Reporting Information [Line Items]
Business activity (in business activities) | business_activity			1
Segment managers responsible for operations (in segment managers) | segment_manager			0
Number of operating segments (in operating segments) | operating_segment			1
Number of reportable segments (in reportable segments) | reportable_segment			1
Total revenue	$ 651.1	$ 548.1	$ 1,846.4	$ 1,544.9
Property and equipment - net	$ 419.4		$ 419.4		$ 344.3
Exclusive Networks Group (Exclusive) [Member] | Customer Concentration Risk [Member] | Revenue [Member]
Segment Reporting Information [Line Items]
Concentration (percent)	29.00%	30.00%	30.00%	31.00%
Exclusive Networks Group (Exclusive) [Member] | Customer Concentration Risk [Member] | Accounts Receivable [Member]
Segment Reporting Information [Line Items]
Concentration (percent)			31.00%		36.00%
Ingram Micro, Inc. (Ingram Micro) [Member] | Customer Concentration Risk [Member] | Revenue [Member]
Segment Reporting Information [Line Items]
Concentration (percent)	10.00%	11.00%	10.00%	11.00%
Ingram Micro, Inc. (Ingram Micro) [Member] | Customer Concentration Risk [Member] | Accounts Receivable [Member]
Segment Reporting Information [Line Items]
Concentration (percent)			11.00%		10.00%
Tech Data Corporation [Member] | Customer Concentration Risk [Member] | Accounts Receivable [Member]
Segment Reporting Information [Line Items]
Concentration (percent)			10.00%
Americas [Member]
Segment Reporting Information [Line Items]
Total revenue	$ 272.4	$ 241	$ 776	$ 668
Property and equipment - net	399.1		399.1		$ 323.4
U.S. [Member]
Segment Reporting Information [Line Items]
Total revenue	206	182.3	589.1	506.9
Property and equipment - net	270.9		270.9		197.4
Canada [Member]
Segment Reporting Information [Line Items]
Property and equipment - net	121.3		121.3		120.5
Latin America [Member]
Segment Reporting Information [Line Items]
Property and equipment - net	6.9		6.9		5.5
Other Americas [Member]
Segment Reporting Information [Line Items]
Total revenue	66.4	58.7	186.9	161.1
EMEA [Member]
Segment Reporting Information [Line Items]
Total revenue	243.3	200.9	693.5	571.1
Property and equipment - net	15.3		15.3		15.2
APAC [Member]
Segment Reporting Information [Line Items]
Total revenue	135.4	$ 106.2	376.9	$ 305.8
Property and equipment - net	$ 5		$ 5		$ 5.7