Fortinet (FTNT) 10-Q 31 Oct 19 2019 Q3 Quarterly report Financial data

Document and Entity Information

Document and Entity Information - shares	9 Months Ended
	Sep. 30, 2019	Oct. 23, 2019
Cover page.
Document Type	10-Q
Document Quarterly Report	true
Document Period End Date	Sep. 30, 2019
Document Transition Report	false
Entity File Number	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		171,033,736
Entity Central Index Key	0001262039
Amendment Flag	false
Document Fiscal Year Focus	2019
Document Fiscal Period Focus	Q3
Current Fiscal Year End Date	--12-31

Condensed Consolidated Balance

Condensed Consolidated Balance Sheets - USD ($) $ in Millions	Sep. 30, 2019	Dec. 31, 2018
CURRENT ASSETS:
Cash and cash equivalents	$ 1,175.5	$ 1,112.4
Short-term investments	764.8	537.2
Accounts receivable—net	384.1	444.5
Inventory	99.2	90
Prepaid expenses and other current assets	42.6	36.8
Total current assets	2,466.2	2,220.9
LONG-TERM INVESTMENTS	204.2	67
PROPERTY AND EQUIPMENT—NET	305.5	271.4
DEFERRED CONTRACT COSTS	217.4	182.6
DEFERRED TAX ASSETS	243.7	255
GOODWILL	38.2	38.2
OTHER INTANGIBLE ASSETS—NET	14	22.1
OTHER ASSETS	56.4	20.8
TOTAL ASSETS	3,545.6	3,078
CURRENT LIABILITIES:
Accounts payable	85.9	86.4
Accrued liabilities	90.4	77.5
Accrued payroll and compensation	90.4	98.4
Income taxes payable	11.6	28.2
Deferred revenue	1,063.6	965.9
Total current liabilities	1,341.9	1,256.4
DEFERRED REVENUE	882	720.9
INCOME TAX LIABILITIES	83.1	77.5
OTHER LIABILITIES	38.2	13
Total liabilities	2,345.2	2,067.8
COMMITMENTS AND CONTINGENCIES (Note 11)
STOCKHOLDERS’ EQUITY:
Common stock, $0.001 par value—300 shares authorized; 171.3 and 169.8 shares issued and outstanding at September 30, 2019 and December 31, 2018, respectively	0.2	0.2
Additional paid-in capital	1,152.6	1,068.3
Accumulated other comprehensive income (loss)	1.1	(0.8)
Retained earnings (accumulated deficit)	46.5	(57.5)
Total stockholders’ equity	1,200.4	1,010.2
TOTAL LIABILITIES AND STOCKHOLDERS’ EQUITY	$ 3,545.6	$ 3,078

Condensed Consolidated Statemen

Condensed Consolidated Statements of Income - USD ($) shares in Millions, $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
REVENUE:
Total revenue	$ 547.5	$ 453.9	$ 1,541.8	$ 1,294.2
COST OF REVENUE:
Total cost of revenue	124.1	111.6	365.4	321.9
GROSS PROFIT:
Total gross profit	423.4	342.3	1,176.4	972.3
OPERATING EXPENSES:
Research and development	69.9	58.7	205.9	179
Sales and marketing	227.4	198.3	669.8	576.4
General and administrative	26.1	22.5	74.9	71
Total operating expenses	323.4	279.5	950.6	826.4
OPERATING INCOME	100	62.8	225.8	145.9
INTEREST INCOME	11.4	6.9	32.6	17.2
OTHER INCOME (EXPENSE)—NET	(6)	0.9	(6.9)	(4.3)
INCOME BEFORE INCOME TAXES	105.4	70.6	251.5	158.8
PROVISION FOR INCOME TAXES	25.6	11.9	40.2	9.2
NET INCOME	$ 79.8	$ 58.7	$ 211.3	$ 149.6
Net income per share (Note 9):
Basic (in dollars per share)	$ 0.47	$ 0.35	$ 1.24	$ 0.89
Diluted (in dollars per share)	$ 0.46	$ 0.33	$ 1.21	$ 0.86
Weighted-average shares outstanding:
Basic (in shares)	171.3	169.8	170.9	168.7
Diluted (in shares)	174.8	175.7	174.9	173.7
Product [Member]
REVENUE:
Total revenue	$ 197.1	$ 164.5	$ 549.7	$ 473.6
COST OF REVENUE:
Total cost of revenue	79	72	231.9	204.1
GROSS PROFIT:
Total gross profit	118.1	92.5	317.8	269.5
Service [Member]
REVENUE:
Total revenue	350.4	289.4	992.1	820.6
COST OF REVENUE:
Total cost of revenue	45.1	39.6	133.5	117.8
GROSS PROFIT:
Total gross profit	$ 305.3	$ 249.8	$ 858.6	$ 702.8

Condensed Consolidated Balanc_2

Condensed Consolidated Balance Sheets Parenthetical - $ / shares	Sep. 30, 2019	Dec. 31, 2018
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	171,300,000	169,800,000
Common Stock, shares outstanding	171,300,000	169,800,000

Condensed Consolidated Statem_2

Condensed Consolidated Statements of Comprehensive Income - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Net income	$ 79.8	$ 58.7	$ 211.3	$ 149.6
Other comprehensive income (loss):
Change in unrealized gains (losses) on investments	0.2	0.5	2.7	(0.1)
Less: tax provision related to change in unrealized gains (losses) on investments	0	0.1	0.7	0.1
Other comprehensive income (loss)	0.2	0.4	2	(0.2)
Comprehensive income	$ 80	$ 59.1	$ 213.3	$ 149.4

Condensed Consolidated Statem_3

Condensed Consolidated Statements of Stockholders' Equity - USD ($) shares in Millions, $ in Millions	Total	Common Stock [Member]	Additional Paid-in Capital [Member]	Accumulated Other Comprehensive Income (Loss) [Member]	Retained Earnings (Accumulated Deficit) [Member]
Balance, shares at Dec. 31, 2017		167.9
Balance at Dec. 31, 2017	$ 589.4	$ 0.2	$ 909.6	$ (0.8)	$ (319.6)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Issuance of common stock in connection with equity incentive plans - net of tax withholding (in shares)		4.9
Issuance of common stock in connection with equity incentive plans - net of tax withholding	32.3		32.3
Repurchase and retirement of common stock (in shares)		(2.5)
Repurchase and retirement of common stock	(117.1)		(13.8)		(103.3)
Stock-based compensation expense	120.3		120.3
Net unrealized gain on investments - net of tax	(0.2)			(0.2)
Net income	149.6				149.6
Balance, shares at Sep. 30, 2018		170.3
Balance at Sep. 30, 2018	891.6	$ 0.2	1,048.4	(1)	(156)
Balance, shares at Jun. 30, 2018		169
Balance at Jun. 30, 2018	780.2	$ 0.2	996.1	(1.4)	(214.7)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Issuance of common stock in connection with equity incentive plans - net of tax withholding (in shares)		1.3
Issuance of common stock in connection with equity incentive plans - net of tax withholding	9.1		9.1
Repurchase and retirement of common stock (in shares)		0
Repurchase and retirement of common stock	0		0		0
Stock-based compensation expense	43.2		43.2
Net unrealized gain on investments - net of tax	0.4			0.4
Net income	58.7				58.7
Balance, shares at Sep. 30, 2018		170.3
Balance at Sep. 30, 2018	891.6	$ 0.2	1,048.4	(1)	(156)
Balance, shares at Dec. 31, 2018		169.8
Balance at Dec. 31, 2018	1,010.2	$ 0.2	1,068.3	(0.8)	(57.5)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Issuance of common stock in connection with equity incentive plans - net of tax withholding (in shares)		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 on investments - net of tax	2			2
Net income	211.3				211.3
Balance, shares at Sep. 30, 2019		171.3
Balance at Sep. 30, 2019	1,200.4	$ 0.2	1,152.6	1.1	46.5
Balance, shares at Jun. 30, 2019		171
Balance at Jun. 30, 2019	1,122.3	$ 0.2	1,130.2	0.9	(9)
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 on investments - net of tax	0.2			0.2
Net income	79.8
Balance, shares at Sep. 30, 2019		171.3
Balance at Sep. 30, 2019	$ 1,200.4	$ 0.2	$ 1,152.6	$ 1.1	$ 46.5

Condensed Consolidated Statem_4

Condensed Consolidated Statements of Cash Flows - USD ($) $ in Millions	9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018
CASH FLOWS FROM OPERATING ACTIVITIES:
Net income	$ 211.3	$ 149.6
Adjustments to reconcile net income to net cash provided by operating activities:
Stock-based compensation	130.4	120.3
Amortization of deferred contract costs	78.5	66.3
Depreciation and amortization	45.9	41
Amortization of investment premiums, net of accretion of purchase discounts	(4.7)	0
Other	5	(1.7)
Changes in operating assets and liabilities:
Accounts receivable—net	60.5	38
Inventory	(25.2)	(19)
Prepaid expenses and other current assets	(6.3)	1.8
Deferred contract costs	(113.1)	(98.8)
Deferred tax assets	10.6	(19.1)
Other assets	(0.8)	(3.3)
Accounts payable	(6.2)	(4.9)
Accrued liabilities	(5.6)	(2)
Accrued payroll and compensation	(9.5)	(8.6)
Other liabilities	(1)	(2.8)
Deferred revenue	258.8	209.9
Income taxes payable	(11)	(8)
Net cash provided by operating activities	617.6	458.7
CASH FLOWS FROM INVESTING ACTIVITIES:
Purchases of investments	(1,072.4)	(405.2)
Sales of investments	19.7	39.6
Maturities of investments	695	405.6
Purchases of property and equipment	(45)	(41.4)
Payments made in connection with business combination, net of cash acquired	0	(6)
Net cash used in investing activities	(402.7)	(7.4)
CASH FLOWS FROM FINANCING ACTIVITIES:
Repurchase and retirement of common stock	(117.6)	(117.1)
Proceeds from issuance of common stock	41.8	81.6
Taxes paid related to net share settlement of equity awards	(76)	(48)
Payments of debt assumed in connection with business combination	0	(9.5)
Net cash used in financing activities	(151.8)	(93)
NET INCREASE IN CASH AND CASH EQUIVALENTS	63.1	358.3
CASH AND CASH EQUIVALENTS—Beginning of period	1,112.4	811
CASH AND CASH EQUIVALENTS—End of period	1,175.5	1,169.3
SUPPLEMENTAL DISCLOSURES OF CASH FLOW INFORMATION:
Operating lease liabilities arising from obtaining right-of-use assets	12.6
Cash paid to settle liability incurred for repurchase of common stock	4.2	0
NON-CASH INVESTING AND FINANCING ACTIVITIES:
Transfers of evaluation units from inventory to property and equipment	16.3	16.2
Liability for purchase of property and equipment and asset retirement obligations	20.1	6.7
Liability incurred for repurchase of common stock	$ 4	$ 0

Summary of Significant Accounti

Summary of Significant Accounting Policies	9 Months Ended
	Sep. 30, 2019
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, 2018, contained in our Annual Report on Form 10-K filed with the SEC on February 27, 2019. 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, 2019 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, 2018 is derived from the audited consolidated financial statements for the year ended December 31, 2018. 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, 2019 , except for the accounting policies for leases that were updated as a result of adopting Accounting Standards Update (“ ASU ”) 2016-02—Leases (Topic 842) (“ Topic 842 ”). For more information, refer to the “Recently Adopted Accounting Standards” and Note 10 . Recently Adopted Accounting Standards Leases In February 2016, the Financial Accounting Standards Board (the “ FASB ”) issued Topic 842 , which requires the recognition of right-of-use (“ROU”) assets and lease liabilities for operating leases on the condensed consolidated balance sheet. We adopted Topic 842 and its related amendments as of January 1, 2019 using a modified retrospective transition approach by applying the new standard to all leases existing at the date of initial application and not restating comparative periods. We elected the package of practical expedients permitted under the transition guidance, which allowed us to waive reassessing the lease classification for any expired or existing leases, the initial direct costs for any existing leases and whether any expired or existing contracts contained leases. Under the new guidance, we determine if an arrangement contains a lease and the classification of that lease, if applicable, at inception or upon modification of a contract. We have elected to not recognize a lease liability or ROU asset for short-term leases (leases that, at the commencement date, have a lease term of twelve months or less and do not include an option to purchase the underlying asset that the Company is reasonably certain to exercise). We have elected to not allocate the contract consideration for operating lease contracts with lease and non-lease components, and account for the lease and non-lease components as a single lease component. ROU assets represent our right to use an underlying asset for the lease term. Lease liabilities represent our obligation to make lease payments under the lease. Operating lease ROU assets and liabilities are recognized at the lease commencement date based on the present value of lease payments over the lease term. The implicit rate within our operating leases is generally not determinable and therefore we use our incremental borrowing rate at the lease commencement date to determine the present value of lease payments. The determination of our incremental borrowing rate requires judgment. We determine our incremental borrowing rate for each lease using indicative bank borrowing rates, adjusted for various factors including level of collateralization, term and currency to align with the terms of a lease. The operating lease ROU asset also includes any lease prepayments, net of lease incentives. Certain leases include options to extend or terminate the lease. An option to extend the lease is considered in connection with determining the ROU asset and lease liability when it is reasonably certain we will exercise that option. An option to terminate is considered unless it is reasonably certain we will not exercise the option. The primary impact of adopting Topic 842 was the recognition of ROU assets and lease liabilities for operating leases of $39.1 million and $40.6 million , respectively, on January 1, 2019, which included reclassifying prepaid rent and deferred rent as a component of the ROU asset. Topic 842 did not have a material impact on our condensed consolidated statements of income and cash flows. The ROU assets and the short-term and long-term lease liabilities from our operating leases are included in other assets, accrued liabilities and other liabilities in our condensed consolidated balance sheets, respectively. Our accounting for finance leases (formerly referred to as capital leases prior to the adoption of Topic 842 ) remains substantially unchanged. Finance leases are not material to our condensed consolidated financial statements. Lease expense for lease payments for our operating leases is recognized on a straight-line basis over the term of the lease. Comprehensive Income In February 2018, the FASB issued ASU 2018-02—Income Statement—Reporting Comprehensive Income (Topic 220): Reclassification of Certain Tax Effects from Accumulated Other Comprehensive Income, which allows companies to reclassify stranded tax effects resulting from the Tax Cuts and Jobs Act (the “ 2017 Tax Act ”) from accumulated other comprehensive income to retained earnings. We adopted ASU 2018-02 on January 1, 2019 and elected to reclassify $0.1 million of stranded tax effects as of that date. Stock Compensation In June 2018, the FASB issued ASU 2018-07—Compensation—Stock Compensation (Topic 718): Improvements to Nonemployee Share-Based Payment Accounting, which simplifies the accounting for share-based payments to nonemployees by aligning it with the accounting for share-based payments to employees subject to certain exceptions. ASU 2018-07 expands the scope of Accounting Standards Codification (“ ASC ”) Topic 718, Compensation—Stock Compensation (“ ASC 718 ”), to include share-based payments granted to nonemployees in exchange for goods or services used or consumed in an entity’s own operations and supersedes the guidance in ASC 505, Equity, by moving it to ASC 718 . We adopted ASU 2018-07 on January 1, 2019. ASU 2018-07 did not have a material impact on our condensed consolidated financial statements. Recent Accounting Standards Not Yet Effective 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 ASC Topic 350, Intangibles—Goodwill and Other, to determine which implementation costs to capitalize as assets or expense as incurred. Companies can choose to adopt the ASU 2018-15 prospectively or retrospectively. ASU 2018-15 is effective for us beginning January 1, 2020, and early adoption is permitted. We are currently evaluating the impact of ASU 2018-15 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. ASU 2018-13 is effective for us beginning January 1, 2020. The amendments in ASU 2018-13 that relate to changes in unrealized gains and losses, the range and weighted average of significant unobservable inputs used to develop Level 3 fair value measurements and the narrative description of measurement uncertainty should be applied prospectively for only the most recent interim or annual period presented in the initial fiscal year of adoption. All other amendments in ASU 2018-13 should be applied retrospectively to all periods presented upon their effective date. Early adoption is permitted upon issuance of ASU 2018-13. An entity is permitted to early adopt any removed or modified disclosures upon issuance of ASU 2018-13 and delay adoption of the additional disclosures until their effective date. We are currently assessing the impact the new guidance will have on our disclosures. Financial Instruments In June 2016, the FASB issued ASU 2016-13—Financial Instruments—Credit Losses (Topic 326): Measurement of Credit Losses on Financial Instruments and in November 2018, the FASB issued ASU 2018-19—Codification Improvements to Topic 326, Financial Instruments—Credit Losses, as a subsequent amendment to the initial guidance (collectively, Topic 326). In April 2019, the FASB issued ASU 2019-04—Codification Improvements to Topic 326: Financial Instruments—Credit Losses, Topic 815, Derivatives and Hedging, and Topic 825, Financial Instruments, and in May 2019, the FASB issued ASU 2019-05—Financial Instruments—Credit Losses (Topic 326): Targeted Transition Relief. Topic 326 requires a financial asset (or a group of financial assets) measured at an amortized cost basis to be presented at the net amount expected to be collected. The new approach to estimating credit losses (referred to as the current expected credit losses model) generally accelerates recognition of credit losses. We are in the process of determining the changes needed to our valuation model for trade receivables, and we are reviewing our process to identify credit-related losses on available-for-sale investments. We also expect the new guidance to expand our related financial statement disclosures. The new guidance is effective for us beginning on January 1, 2020, and early adoption is permitted. We are currently assessing the impact of the new guidance on our condensed consolidated financial statements.

Revenue Recognition

Revenue Recognition	9 Months Ended
	Sep. 30, 2019
Revenue from Contract with Customer [Abstract]
Revenue Recognition	REVENUE RECOGNITION Our revenue consists of product and service revenue. Product revenue is generated by sales of our FortiGate products and other hardware and software solutions. Service revenue relates to sales of our FortiGuard security subscription, FortiCare technical support services and other services. Disaggregation of Revenue The following table presents our revenue disaggregated by major product and service lines (in millions): Three Months Ended Nine Months Ended September 30, September 30, September 30, September 30, Product $ 197.1 $ 164.5 $ 549.7 $ 473.6 Service: Security subscription 192.8 157.0 545.5 440.7 Technical support and other 157.6 132.4 446.6 379.9 Total service revenue 350.4 289.4 992.1 820.6 Total revenue $ 547.5 $ 453.9 $ 1,541.8 $ 1,294.2 Deferred Revenue During the three months ended September 30, 2019 and September 30, 2018 , we recognized $211.6 million and $173.0 million in revenue that was included in the deferred revenue balance as of December 31, 2018 and December 31, 2017, respectively. During the nine months ended September 30, 2019 and September 30, 2018 , we recognized $752.2 million and $615.3 million in revenue that was included in the deferred revenue balance as of December 31, 2018 and December 31, 2017, respectively. Transaction Price Allocated to the Remaining Performance Obligations As of September 30, 2019 , the aggregate amount of the transaction price allocated to remaining performance obligations was $1.95 billion , which was substantially comprised of deferred security subscription and technical support services revenue. We expect to recognize approximately $1.06 billion as revenue over the next 12 months and the remainder thereafter. Accounts Receivable Trade accounts receivable are recorded at the invoiced amount. Trade accounts receivable are reduced by an allowance for doubtful accounts which is determined based on our assessment of the collectability of customer accounts. The allowance for doubtful accounts was $0.8 million and $0.9 million as of September 30, 2019 and December 31, 2018, respectively. 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, 2019 and September 30, 2018 were $27.5 million and $23.2 million , respectively. Amortization of deferred contract costs during the nine months ended September 30, 2019 and September 30, 2018 were $78.5 million and $66.3 million , respectively.

Financial Instruments and Fair

Financial Instruments and Fair Value	9 Months Ended
	Sep. 30, 2019
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, 2019 Amortized Cost Unrealized Gains Unrealized Losses Fair Value Corporate debt securities $ 541.5 $ 1.2 $ (0.2 ) $ 542.5 Commercial paper 132.8 0.1 — 132.9 U.S. government and agency securities 221.3 0.3 — 221.6 Certificates of deposit and term deposits (1) 72.0 — — 72.0 Total available-for-sale securities $ 967.6 $ 1.6 $ (0.2 ) $ 969.0 December 31, 2018 Amortized Cost Unrealized Gains Unrealized Losses Fair Value Corporate debt securities $ 299.5 $ — $ (1.2 ) $ 298.3 Commercial paper 102.5 — — 102.5 Certificates of deposit and term deposits (1) 145.8 — — 145.8 U.S. government and agency securities 57.7 — (0.1 ) 57.6 Total available-for-sale securities $ 605.5 $ — $ (1.3 ) $ 604.2 (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, 2019 Less Than 12 Months 12 Months or Greater Total Fair Value Unrealized Losses Fair Value Unrealized Losses Fair Value Unrealized Losses Corporate debt securities $ 67.3 $ (0.1 ) $ 35.9 $ (0.1 ) $ 103.2 $ (0.2 ) December 31, 2018 Less Than 12 Months 12 Months or Greater Total Fair Value Unrealized Losses Fair Value Unrealized Losses Fair Value Unrealized Losses Corporate debt securities $ 150.1 $ (0.2 ) $ 93.5 $ (1.0 ) $ 243.6 $ (1.2 ) Commercial paper 75.6 (0.1 ) — — 75.6 (0.1 ) Certificates of deposit and term deposits 51.7 — — — 51.7 — U.S. government and agency securities 39.0 — 3.5 — 42.5 — Total available-for-sale securities $ 316.4 $ (0.3 ) $ 97.0 $ (1.0 ) $ 413.4 $ (1.3 ) The contractual maturities of our investments were as follows (in millions): September 30, December 31, Due within one year $ 764.8 $ 537.2 Due within one to three years 204.2 67.0 Total $ 969.0 $ 604.2 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. 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 condensed consolidated statements of income. We use the specific identification method to determine the cost basis of investments sold. The unrealized losses on our available-for-sale securities were caused by fluctuations in market value and interest rates as a result of the economic environment. We consider these investments to be temporarily impaired as of September 30, 2019 because (i) the decline in market value was attributable to changes in market conditions and not credit quality, and (ii) we have concluded currently 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. 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 and agency 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, 2019 and December 31, 2018 (in millions): September 30, 2019 December 31, 2018 Aggregate Fair Value Quoted Prices in Active Markets For Identical Assets Significant Other Observable Remaining Inputs Significant Other Unobservable Remaining Inputs Aggregate Fair Value Quoted Prices in Active Markets For Identical Assets Significant Other Observable Remaining Inputs Significant Other Unobservable Remaining Inputs (Level 1) (Level 2) (Level 3) (Level 1) (Level 2) (Level 3) Assets: Corporate debt securities $ 542.5 $ — $ 542.5 $ — $ 299.3 $ — $ 299.3 $ — Commercial paper 144.1 — 144.1 — 184.7 — 184.7 — Certificates of deposit and term deposits 72.0 — 72.0 — 217.4 — 217.4 — U.S. government and agency securities 221.6 221.6 — — 57.6 45.3 12.3 — Money market funds 34.2 34.2 — — 58.6 58.6 — — Total $ 1,014.4 $ 255.8 $ 758.6 $ — $ 817.6 $ 103.9 $ 713.7 $ — Reported as: Cash equivalents $ 45.4 $ 213.4 Short-term investments 764.8 537.2 Long-term investments 204.2 67.0 Total $ 1,014.4 $ 817.6 There were no transfers between Level 1 and Level 2 of the fair value hierarchy during the nine months ended September 30, 2019 and year ended December 31, 2018 .

Inventory

Inventory	9 Months Ended
	Sep. 30, 2019
Inventory Disclosure [Abstract]
INVENTORY	INVENTORY Inventory consisted of the following (in millions): September 30, December 31, Raw materials $ 7.7 $ 13.3 Finished goods 91.5 76.7 Inventory $ 99.2 $ 90.0

Property and Equipment_Net

Property and Equipment—Net	9 Months Ended
	Sep. 30, 2019
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 $ 75.7 $ 75.7 Building and building improvements 143.6 144.2 Computer equipment and software 113.6 95.9 Leasehold improvements 20.1 17.9 Evaluation units 20.5 20.5 Furniture and fixtures 16.7 15.7 Construction-in-progress 44.4 12.3 Total property and equipment 434.6 382.2 Less: accumulated depreciation (129.1 ) (110.8 ) Property and equipment—net $ 305.5 $ 271.4 Depreciation expense was $12.8 million and $11.8 million during the three months ended September 30, 2019 and September 30, 2018 , respectively. Depreciation expense was $37.8 million and $34.9 million during the nine months ended September 30, 2019 and September 30, 2018

Investments in Privately-Held C

Investments in Privately-Held Companies	9 Months Ended
	Sep. 30, 2019
Investments, All Other Investments [Abstract]
INVESTMENTS IN PRIVATELY-HELD COMPANIES	INVESTMENTS IN PRIVATELY HELD COMPANIES Our investments in the equity securities of privately held companies totaled $5.3 million and $9.1 million as of September 30, 2019 and December 31, 2018 , respectively. These investments are accounted for at cost, adjusted for changes in observable prices minus impairment. We own less than 20% of the voting securities in each of these investments and do not have the ability to exercise significant influence over operating and financial policies of the respective entities. These investments are recorded as other assets in our condensed consolidated balance sheets and would be measured at fair value if indicators of an increase in value or impairment existed. During the three months ended September 30, 2019, we determined that one of our investments was other-than-temporarily impaired. As a result, we recognized a non-cash impairment charge of $3.8 million to Other income (expense)—net in our condensed consolidated statements of income. During the three months ended September 30, 2018, we sold equity securities of a privately held company for $5.2 million and recognized a gain of $2.2 million to Other income (expense)—net in our condensed consolidated statements of income.

Business Combinations

Business Combinations	9 Months Ended
	Sep. 30, 2019
Business Combinations [Abstract]
BUSINESS COMBINATIONS	BUSINESS COMBINATIONS ZoneFox Holdings Limited On October 22, 2018, we acquired all outstanding shares of ZoneFox Holdings Limited (“ZoneFox”), a privately held cloud-based company providing insider threat detection and response. ZoneFox is headquartered in Edinburgh, Scotland. Under the business combination method of accounting in accordance with ASC Topic 805, Business Combinations (“ASC 805”), the total purchase price was allocated to ZoneFox’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 purchase price for ZoneFox was $16.1 million , of which $12.5 million was allocated to goodwill that was non-deductible for tax purposes, and $6.8 million was allocated to identifiable intangible assets, the majority of which was developed technology offset by $3.2 million of net liabilities assumed. Acquisition-related costs related to the ZoneFox acquisition were not material. 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. We may pay an additional $2.0 million in cash consideration as an earn-out that is subject in full to satisfaction of certain performance conditions. As of September 30, 2019 , no fair value was assigned to the contingent consideration based on the estimated probability of attainment of the performance conditions. Bradford Networks, Inc. On June 4, 2018, we acquired all outstanding shares of Bradford Networks, Inc. (“Bradford”), a provider of network access control security products and services. Under the business combination method of accounting in accordance with ASC 805, the total purchase price was allocated to Bradford’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 purchase price for Bradford was $6.8 million , of which $11.1 million was allocated to goodwill that was non-deductible for tax purposes, and $8.0 million was allocated to identifiable intangible assets, the majority of which was developed technology offset by $12.3 million of net liabilities assumed. Acquisition-related costs related to the Bradford acquisition were not material. 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. The acquisition included a $2.0 million cash earn-out that was subject in full to satisfaction of certain performance conditions. The performance conditions were not met and the cash earn-out will not be paid. Pro forma information has not been presented for these acquisitions as the impact to our condensed consolidated financial statements was not material.

Goodwill and Other Intangible A

Goodwill and Other Intangible Assets - Net	9 Months Ended
	Sep. 30, 2019
Goodwill and Intangible Assets Disclosure [Abstract]
GOODWILL AND OTHER INTANGIBLE ASSETS - Net	GOODWILL AND OTHER INTANGIBLE ASSETS—Net Goodwill As of September 30, 2019 and December 31, 2018 , we had goodwill of $38.2 million . There were no impairments to goodwill during the nine months ended September 30, 2019 or during prior periods. Other Intangible Assets—Net The following tables present other intangible assets—net as of September 30, 2019 and December 31, 2018 (in millions, except years): September 30, 2019 Weighted-Average Useful Life (in Years) Gross Accumulated Amortization Net Other intangible assets—net: Finite-lived intangible assets: Developed technologies 4.0 $ 34.4 $ 22.7 $ 11.7 Customer relationships 4.4 17.5 15.2 2.3 Total other intangible assets—net $ 51.9 $ 37.9 $ 14.0 December 31, 2018 Weighted-Average Useful Life (in Years) Gross Accumulated Amortization Net Other intangible assets—net: Finite-lived intangible assets: Developed technologies 4.0 $ 34.4 $ 17.0 $ 17.4 Customer relationships 4.4 17.5 12.8 4.7 Total other intangible assets—net $ 51.9 $ 29.8 $ 22.1 Amortization expense was $2.2 million and $2.5 million during the three months ended September 30, 2019 and September 30, 2018 , respectively. Amortization expense was $8.1 million and $6.1 million during the nine months ended September 30, 2019 and September 30, 2018 , respectively. The following table summarizes estimated future amortization expense of finite-lived intangible assets—net (in millions): Amount Years: 2019 (the remainder of 2019) $ 2.2 2020 6.2 2021 3.5 2022 2.1 Total $ 14.0

Net Income Per Share

Net Income Per Share	9 Months Ended
	Sep. 30, 2019
Earnings Per Share [Abstract]
NET INCOME PER SHARE	NET INCOME PER SHARE Basic net income per share is computed by dividing net income by the weighted-average number of shares of common stock outstanding during the period. Diluted net income per share is computed by dividing net income by the weighted-average number of shares of common stock outstanding during the period, plus the dilutive effects of restricted stock units (“ RSU s”), stock options and our Employee Stock Purchase Plan (the “ ESPP ”), which was terminated in February 2019 at the completion of the prior offering period. 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 $ 79.8 $ 58.7 $ 211.3 $ 149.6 Denominator: Basic shares: Weighted-average common stock outstanding-basic 171.3 169.8 170.9 168.7 Diluted shares: Weighted-average common stock outstanding-basic 171.3 169.8 170.9 168.7 Effect of potentially dilutive securities: RSUs 2.4 4.2 2.9 3.5 Stock options 1.1 1.6 1.1 1.4 ESPP — 0.1 — 0.1 Weighted-average shares used to compute diluted net income per share 174.8 175.7 174.9 173.7 Net income per share: Basic $ 0.47 $ 0.35 $ 1.24 $ 0.89 Diluted $ 0.46 $ 0.33 $ 1.21 $ 0.86 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 0.2 0.3 0.3 0.6 Stock options 0.7 — 0.6 0.4 ESPP — 0.2 — 0.1 Total 0.9 0.5 0.9 1.1

Leases

Leases	9 Months Ended
	Sep. 30, 2019
Leases [Abstract]
LEASES	LEASES We have operating leases for offices, research and development facilities and data centers. Our leases have remaining terms that range from less than one year to approximately seven years , some of which include one or more options to renew, with renewal terms of up to five years . We do not include renewal options in our lease terms for calculating our lease liability, as the renewal options allow us to maintain operational flexibility and we are not reasonably certain we will exercise these renewal options at the time of the lease commencement. Our finance leases are not material to our financial statements. The components of lease expense were as follows (in millions): Three Months Ended Nine Months Ended September 30, September 30, Operating lease expense $ 3.8 $ 11.1 Variable lease expense (1) 0.7 1.9 Short-term lease expense 0.8 2.2 Total lease expense $ 5.3 $ 15.2 (1) Variable lease expense for the three and nine months ended September 30, 2019 predominantly included common area maintenance charges and parking expense. Rent expense was $4.4 million and $13.1 million during the three and nine months ended September 30, 2018 , respectively. Rent expense was recognized in accordance with ASC 840, Leases, using the straight-line method over the term of a lease. Supplemental balance sheet information related to our operating leases was as follows (in millions, except lease term and discount rate): Classification September 30, Operating lease ROU assets - non-current Other assets $ 41.0 Operating lease liabilities - current Accrued liabilities $ 13.9 Operating lease liabilities - non-current Other liabilities 27.7 Total operating lease liabilities $ 41.6 Weighted average remaining lease term in years - operating leases 3.9 Weighted average discount rate - operating leases 3.0 % Supplemental cash flow information related to leases was as follows (in millions): Nine Months Ended September 30, Cash paid for amounts included in the measurement of lease liabilities Operating cash flows used for operating leases $ 11.9 Lease liabilities arising from obtaining right-of-use assets Operating leases $ 12.6 Maturities of operating lease liabilities as of September 30, 2019 were as follows (in millions): Year ending December 31, Amount 2019 (the remainder of 2019) $ 3.5 2020 14.6 2021 10.6 2022 6.2 2023 4.5 Thereafter 4.9 Total lease payments $ 44.3 Less imputed interest (2.7 ) Total $ 41.6 As of September 30, 2019 , we had additional minimum lease payments of $1.7 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 2019 and will have lease terms of approximately two to five years . The following table summarizes our future principal contractual obligations for operating lease commitments as of December 31, 2018 (in millions): Year ending December 31, Amount 2019 $ 17.1 2020 12.2 2021 8.5 2022 5.0 2023 3.6 Thereafter 3.7 Total $ 50.1 Total future principal contractual obligations for operating lease commitments as of December 31, 2018 exceeded our undiscounted lease liability as of the Topic 842 adoption date, primarily because the lease liability excluded short-term lease payments (due to the adoption of the short-term lease exemption) and excluded minimum lease payments relating to an operating lease that had been signed but had not yet commenced.

Commitments and Contingencies

Commitments and Contingencies	9 Months Ended
	Sep. 30, 2019
Commitments and Contingencies Disclosure [Abstract]
COMMITMENTS AND CONTINGENCIES	COMMITMENTS AND CONTINGENCIES The following table summarizes our future principal contractual obligations as of September 30, 2019 (in millions): Total 2019 2020 2021 2022 2023 Thereafter Inventory purchase commitments $ 241.4 $ 144.5 $ 96.9 $ — $ — $ — $ — 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, 2019 , we had $241.4 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, 2019 , we had $12.6 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 intellectual property 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 intellectual property 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 intellectual property infringement, that could potentially expose us to losses in excess of the amount received under the agreement, and in some instances to potential liability that is not contractually limited. To date, although from time to time there are indemnification claims asserted against us and currently there are pending indemnification claims, there have been no material awards under such indemnification provisions.

Stockholders' Equity

Stockholders' Equity	9 Months Ended
	Sep. 30, 2019
Share-based Payment Arrangement [Abstract]
STOCKHOLDERS' EQUITY	STOCKHOLDERS’ EQUITY Stock-Based Compensation Plans We have stock-based compensation plans pursuant to which we have granted RSU s and stock options. We also previously had an ESPP for eligible employees, which was terminated in February 2019. On June 21, 2019, our stockholders approved the Amended and Restated Fortinet, Inc. 2009 Equity Incentive Plan (the “Amended Plan”). Among other things, the Amended Plan provided for a net decrease in the number of shares of common stock that were authorized and available for issuance pursuant to future awards granted on or following the effective date of the Amended Plan. On June 28, 2019, we deregistered from various registration statements on Form S-8 an aggregate of 46.2 million shares of common stock that were originally registered for issuance under our 2009 Equity Incentive Plan. As of September 30, 2019 , there was a total of 13.6 million shares of common stock available for grant under the Amended Plan. Restricted Stock Units The following table summarizes the activity and related information for RSU s for the periods presented below (in millions, except per share amounts): Restricted Stock Units Outstanding Number of Shares Weighted-Average Grant Date Fair Value per Share Balance—December 31, 2018 7.8 $ 46.07 Granted 2.2 83.76 Forfeited (0.5 ) 53.69 Vested (3.0 ) 43.13 Balance—September 30, 2019 6.5 $ 59.36 As of September 30, 2019 , total compensation expense related to unvested RSU s granted to employees and non-employees under the 2009 Plan, but not yet recognized, was $338.5 million . This expense is expected to be amortized on a straight-line basis over a weighted-average vesting period of 2.7 years. RSU s settle into shares of common stock upon vesting. Upon the vesting of the RSU s, we net-settle the RSU s and withhold a portion of the shares to satisfy minimum statutory employee withholding tax requirement. Total payment of the employees’ tax obligations to the tax authorities is reflected as a financing activity within the condensed consolidated statements of cash flows. The following summarizes the number and value of the shares withheld for employee taxes (in millions): Three Months Ended Nine Months Ended September 30, September 30, September 30, September 30, Shares withheld for taxes 0.2 0.2 0.9 0.9 Amount withheld for taxes $ 19.6 $ 15.5 $ 76.1 $ 48.0 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 35.3 % 30.5 % 34.2 % 31.6 % Risk-free interest rate 1.4 % 2.7 % 2.4 % 2.7 % Dividend rate — % — % — % — % The following table summarizes the stock option activity and related information for the periods presented below (in millions, except exercise prices and contractual life): Options Outstanding Number of Shares Weighted- Average Exercise Price Weighted- Average Remaining Contractual Life (Years) Aggregate Intrinsic Value Balance—December 31, 2018 3.0 $ 35.53 Granted 0.7 84.19 Forfeited (0.1 ) 62.68 Exercised (0.7 ) 29.23 Balance—September 30, 2019 2.9 $ 48.46 Options vested and expected to vest—September 30, 2019 2.9 $ 48.46 4.6 $ 86.5 Options exercisable—September 30, 2019 1.5 $ 33.64 3.5 $ 62.6 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, 2019 for all in-the-money stock options. As of September 30, 2019 , total compensation expense related to unvested stock options granted to employees but not yet recognized was $26.0 million . This expense is expected to be amortized on a straight-line basis over a weighted-average period of 2.9 years. Additional information related to our stock options is summarized below (in millions, except per share amounts): Three Months Ended Nine Months Ended September 30, September 30, September 30, September 30, Weighted-average fair value per share granted $ 24.97 $ 22.75 $ 26.96 $ 15.67 Intrinsic value of options exercised 3.2 14.1 40.1 53.6 Fair value of options vested 2.0 1.4 8.2 5.7 Stock-based Compensation Expense Stock-based compensation expense 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 $ 0.3 $ 1.2 $ 1.1 Cost of service revenue 2.7 2.8 8.4 8.0 Research and development 9.3 9.3 28.7 26.9 Sales and marketing 24.9 26.0 76.6 70.5 General and administrative 5.1 4.8 15.5 13.8 Total stock-based compensation expense $ 42.4 $ 43.2 $ 130.4 $ 120.3 The following table summarizes stock-based compensation expense by award type (in millions): Three Months Ended Nine Months Ended September 30, September 30, September 30, September 30, RSUs $ 39.5 $ 38.2 $ 120.6 $ 106.1 Stock options 2.9 2.4 8.5 6.7 ESPP — 2.6 1.3 7.5 Total stock-based compensation expense $ 42.4 $ 43.2 $ 130.4 $ 120.3 Total income tax benefit associated with stock-based compensation that is recognized in the condensed consolidated statements of income is as follows (in millions): Three Months Ended Nine Months Ended September 30, September 30, September 30, September 30, Income tax benefit associated with stock-based compensation $ 9.8 $ 6.8 $ 30.1 $ 19.0 Share Repurchase Program Under the Share Repurchase Program originally approved by our board of directors in January 2016 (the “ Repurchase Program ”), the repurchase of up to $1.5 billion of our outstanding common stock is authorized through December 31, 2019. Share repurchases may be made by us from time to time in privately negotiated transactions or in open market transactions. The Repurchase Program does not require us to purchase a minimum number of shares, and may be suspended, modified or discontinued at any time without prior notice. During the three and nine months ended September 30, 2019 , we repurchased 0.3 million and 1.6 million shares of common stock, respectively, under the Repurchase Program in open market transactions at an average price of $78.67 per share and $73.94 per share, respectively, for an aggregate purchase price of $26.5 million and $117.4 million , respectively. As of September 30, 2019 , $616.3 million remained available for future share repurchases under the Repurchase Program .

Income Taxes

Income Taxes	9 Months Ended
	Sep. 30, 2019
Income Tax Disclosure [Abstract]
INCOME TAXES	INCOME TAXES Our effective tax rate was 24% for the three months ended September 30, 2019 , compared to an effective tax rate of 17% for the same period last year. Our effective tax rate was 16% for the nine months ended September 30, 2019 , compared to an effective tax rate of 6% 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, 2019 and September 30, 2018 were impacted by U.S. federal and state taxes, withholding taxes and foreign taxes of $29.6 million and $17.7 million , respectively, which were offset by excess tax benefits from stock-based compensation expense of $6.9 million and $5.8 million , respectively. The tax rate for the three months ended September 30, 2019 was impacted by a net increase in tax expense of $2.9 million due to the settlement of foreign tax audits. The tax rates for the nine months ended September 30, 2019 and September 30, 2018 were impacted by U.S. federal and state taxes, withholding taxes and foreign taxes of $71.6 million and $43.4 million , respectively, which were offset by excess tax benefits from stock-based compensation expense of $34.6 million and $16.2 million , respectively. The provision for income taxes for the nine months ended September 30, 2019 included an increase in tax expense of $10.3 million for an unrecognized tax benefit related to the Ninth Circuit’s opinion in Altera Corporation and Subsidiaries vs. Commissioner of Internal Revenue (“Altera”) described below, regarding stock-based compensation expense in cost sharing arrangements. The provision for income taxes for the nine months ended September 30, 2019 included a net increase in tax expense of $2.9 million due to the settlement of foreign tax audits. The net increase was offset due to the release of $10.0 million of reserves related to uncertain tax positions and interest due to the expiration of the statute of limitations. The tax rate for the nine months ended September 30, 2018 was also impacted by release of a reserve on uncertain tax position including interest of $18.0 million . As of September 30, 2019 and December 31, 2018 , unrecognized tax benefits were $67.7 million and $63.5 million , respectively. If recognized, $62.7 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 uncertain tax benefits in income tax expense. As of September 30, 2019 and December 31, 2018 , accrued interest and penalties were $13.8 million and $11.6 million , respectively. It is reasonably possible that our gross unrecognized tax benefits will decrease by up to $7.1 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, Italy, 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 on Altera and ruled in favor of the Commissioner, validating the regulations requiring stock-based compensation to be included in a cost sharing arrangement. Due to the uncertainty surrounding the status of the current regulations and questions related to the scope of potential benefits or obligations, we incurred an unrecognized tax benefit of $10.3 million related to the Ninth Circuit’s Altera decision regarding stock-based compensation in cost sharing arrangements. We continue to monitor developments in this case and any impact it could have on our tax provision.

Defined Contribution Plans

Defined Contribution Plans	9 Months Ended
	Sep. 30, 2019
Retirement Benefits [Abstract]
DEFINED CONTRIBUTION PLANS	DEFINED CONTRIBUTION PLANS Our tax-deferred savings plan under our 401(k) Plan permits participating U.S. employees to contribute a portion of their pre-tax or after-tax earnings. In Canada, we have a Group Registered Retirement Savings Plan Program (the “RRSP”), which permits participants to make tax deductible contributions. Our board of directors approved 50% matching contributions on employee contributions up to 4% of each employee’s eligible earnings. Our matching contributions to our 401(k) Plan and the RRSP for the three months ended September 30, 2019 and September 30, 2018 were $1.8 million and $1.4 million , respectively. Our matching contributions to our 401(k) Plan and the RRSP for the nine months ended September 30, 2019 and September 30, 2018 were $5.2 million and $4.4 million , respectively.

Segment Information

Segment Information	9 Months Ended
	Sep. 30, 2019
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 $ 182.1 $ 146.8 $ 505.9 $ 425.3 Other Americas (1) 58.6 47.2 160.8 133.8 Total Americas 240.7 194.0 666.7 559.1 Europe, Middle East and Africa (“EMEA”) 200.7 165.4 569.9 474.3 Asia Pacific (“APAC”) 106.1 94.5 305.2 260.8 Total revenue $ 547.5 $ 453.9 $ 1,541.8 $ 1,294.2 (1) In 2019, Canada and Latin America revenue were combined and presented as Other Americas. Prior periods have been reclassified to conform with current period presentation. Property and Equipment — net September 30, December 31, Americas: United States $ 162.7 $ 132.1 Canada 117.1 113.5 Latin America 0.5 0.4 Total Americas 280.3 246.0 EMEA (1) 16.6 16.2 APAC 8.6 9.2 Total property and equipment—net $ 305.5 $ 271.4 (1) In 2019, France and Other EMEA property and equipment were combined and presented as EMEA. Prior periods have been reclassified to conform with current period presentation. 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 30 % 29 % 31 % 29 % Ingram Micro 11 % 11 % 11 % 10 % The following distributors accounted for 10% or more of net accounts receivable: September 30, December 31, Exclusive Networks Group 32 % 38 % Ingram Micro 11 % * * Represents less than 10%

Accumulated Other Comprehensive

Accumulated Other Comprehensive Income (Loss)	9 Months Ended
	Sep. 30, 2019
Other Comprehensive Income (Loss), Net of Tax [Abstract]
Accumulated Other Comprehensive Income (Loss)	ACCUMULATED OTHER COMPREHENSIVE INCOME (LOSS) The following table summarizes the changes in accumulated balances of other comprehensive income (loss) (in millions): Unrealized Gains (Losses) on Investments Tax provision (benefit) related to unrealized gains or losses on investments Total Balance—December 31, 2018 $ (1.3 ) $ (0.5 ) $ (0.8 ) Other comprehensive income before reclassifications 2.7 0.7 2.0 Amounts reclassified from accumulated other comprehensive loss — 0.1 (0.1 ) Net current-period other comprehensive income 2.7 0.8 1.9 Balance—September 30, 2019 $ 1.4 $ 0.3 $ 1.1 We adopted ASU 2018-02 on January 1, 2019, and elected to reclassify the income tax effects of the 2017 Tax Act to retained earnings at the beginning of the period. Other amounts reclassified from accumulated other comprehensive loss for unrealized losses on investments and tax provision related to unrealized gains or losses on investments are recorded in other income (expense)—net and in provision for (benefit from) income taxes, respectively.

Subsequent Events

Subsequent Events	9 Months Ended
	Sep. 30, 2019
Subsequent Events [Abstract]
SUBSEQUENT EVENTS	SUBSEQUENT EVENTS Business combination On October 28, 2019, we acquired enSilo Ltd. (“enSilo”), a privately held company that provides endpoint detection and response products and services. We acquired enSilo for approximately $20.0 million in initial consideration, subject to certain adjustments. We are currently in the process of evaluating the business combination accounting, including the consideration transferred and the initial purchase price allocation. Share repurchase Subsequent to September 30, 2019 through the filing of this Quarterly Report on Form 10-Q, we repurchased 0.3 million shares of our common stock, for an aggregate purchase price of $23.5 million at an average price of $77.39 per share, under the Repurchase Program.

Summary of Significant Accoun_2

Summary of Significant Accounting Policies (Policies)	9 Months Ended
	Sep. 30, 2019
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, 2018, contained in our Annual Report on Form 10-K filed with the SEC on February 27, 2019. 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, 2019 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, 2018 is derived from the audited consolidated financial statements for the year ended December 31, 2018. 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, 2019 , except for the accounting policies for leases that were updated as a result of adopting Accounting Standards Update (“ ASU ”) 2016-02—Leases (Topic 842) (“ Topic 842 ”). For more information, refer to the “Recently Adopted Accounting Standards” and Note 10 .
Recently Adopted Accounting Standards and Recent Accounting Standards Not Yet Effective	Recently Adopted Accounting Standards Leases In February 2016, the Financial Accounting Standards Board (the “ FASB ”) issued Topic 842 , which requires the recognition of right-of-use (“ROU”) assets and lease liabilities for operating leases on the condensed consolidated balance sheet. We adopted Topic 842 and its related amendments as of January 1, 2019 using a modified retrospective transition approach by applying the new standard to all leases existing at the date of initial application and not restating comparative periods. We elected the package of practical expedients permitted under the transition guidance, which allowed us to waive reassessing the lease classification for any expired or existing leases, the initial direct costs for any existing leases and whether any expired or existing contracts contained leases. Under the new guidance, we determine if an arrangement contains a lease and the classification of that lease, if applicable, at inception or upon modification of a contract. We have elected to not recognize a lease liability or ROU asset for short-term leases (leases that, at the commencement date, have a lease term of twelve months or less and do not include an option to purchase the underlying asset that the Company is reasonably certain to exercise). We have elected to not allocate the contract consideration for operating lease contracts with lease and non-lease components, and account for the lease and non-lease components as a single lease component. ROU assets represent our right to use an underlying asset for the lease term. Lease liabilities represent our obligation to make lease payments under the lease. Operating lease ROU assets and liabilities are recognized at the lease commencement date based on the present value of lease payments over the lease term. The implicit rate within our operating leases is generally not determinable and therefore we use our incremental borrowing rate at the lease commencement date to determine the present value of lease payments. The determination of our incremental borrowing rate requires judgment. We determine our incremental borrowing rate for each lease using indicative bank borrowing rates, adjusted for various factors including level of collateralization, term and currency to align with the terms of a lease. The operating lease ROU asset also includes any lease prepayments, net of lease incentives. Certain leases include options to extend or terminate the lease. An option to extend the lease is considered in connection with determining the ROU asset and lease liability when it is reasonably certain we will exercise that option. An option to terminate is considered unless it is reasonably certain we will not exercise the option. The primary impact of adopting Topic 842 was the recognition of ROU assets and lease liabilities for operating leases of $39.1 million and $40.6 million , respectively, on January 1, 2019, which included reclassifying prepaid rent and deferred rent as a component of the ROU asset. Topic 842 did not have a material impact on our condensed consolidated statements of income and cash flows. The ROU assets and the short-term and long-term lease liabilities from our operating leases are included in other assets, accrued liabilities and other liabilities in our condensed consolidated balance sheets, respectively. Our accounting for finance leases (formerly referred to as capital leases prior to the adoption of Topic 842 ) remains substantially unchanged. Finance leases are not material to our condensed consolidated financial statements. Lease expense for lease payments for our operating leases is recognized on a straight-line basis over the term of the lease. Comprehensive Income In February 2018, the FASB issued ASU 2018-02—Income Statement—Reporting Comprehensive Income (Topic 220): Reclassification of Certain Tax Effects from Accumulated Other Comprehensive Income, which allows companies to reclassify stranded tax effects resulting from the Tax Cuts and Jobs Act (the “ 2017 Tax Act ”) from accumulated other comprehensive income to retained earnings. We adopted ASU 2018-02 on January 1, 2019 and elected to reclassify $0.1 million of stranded tax effects as of that date. Stock Compensation In June 2018, the FASB issued ASU 2018-07—Compensation—Stock Compensation (Topic 718): Improvements to Nonemployee Share-Based Payment Accounting, which simplifies the accounting for share-based payments to nonemployees by aligning it with the accounting for share-based payments to employees subject to certain exceptions. ASU 2018-07 expands the scope of Accounting Standards Codification (“ ASC ”) Topic 718, Compensation—Stock Compensation (“ ASC 718 ”), to include share-based payments granted to nonemployees in exchange for goods or services used or consumed in an entity’s own operations and supersedes the guidance in ASC 505, Equity, by moving it to ASC 718 . We adopted ASU 2018-07 on January 1, 2019. ASU 2018-07 did not have a material impact on our condensed consolidated financial statements. Recent Accounting Standards Not Yet Effective 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 ASC Topic 350, Intangibles—Goodwill and Other, to determine which implementation costs to capitalize as assets or expense as incurred. Companies can choose to adopt the ASU 2018-15 prospectively or retrospectively. ASU 2018-15 is effective for us beginning January 1, 2020, and early adoption is permitted. We are currently evaluating the impact of ASU 2018-15 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. ASU 2018-13 is effective for us beginning January 1, 2020. The amendments in ASU 2018-13 that relate to changes in unrealized gains and losses, the range and weighted average of significant unobservable inputs used to develop Level 3 fair value measurements and the narrative description of measurement uncertainty should be applied prospectively for only the most recent interim or annual period presented in the initial fiscal year of adoption. All other amendments in ASU 2018-13 should be applied retrospectively to all periods presented upon their effective date. Early adoption is permitted upon issuance of ASU 2018-13. An entity is permitted to early adopt any removed or modified disclosures upon issuance of ASU 2018-13 and delay adoption of the additional disclosures until their effective date. We are currently assessing the impact the new guidance will have on our disclosures. Financial Instruments In June 2016, the FASB issued ASU 2016-13—Financial Instruments—Credit Losses (Topic 326): Measurement of Credit Losses on Financial Instruments and in November 2018, the FASB issued ASU 2018-19—Codification Improvements to Topic 326, Financial Instruments—Credit Losses, as a subsequent amendment to the initial guidance (collectively, Topic 326). In April 2019, the FASB issued ASU 2019-04—Codification Improvements to Topic 326: Financial Instruments—Credit Losses, Topic 815, Derivatives and Hedging, and Topic 825, Financial Instruments, and in May 2019, the FASB issued ASU 2019-05—Financial Instruments—Credit Losses (Topic 326): Targeted Transition Relief. Topic 326 requires a financial asset (or a group of financial assets) measured at an amortized cost basis to be presented at the net amount expected to be collected. The new approach to estimating credit losses (referred to as the current expected credit losses model) generally accelerates recognition of credit losses. We are in the process of determining the changes needed to our valuation model for trade receivables, and we are reviewing our process to identify credit-related losses on available-for-sale investments. We also expect the new guidance to expand our related financial statement disclosures. The new guidance is effective for us beginning on January 1, 2020, and early adoption is permitted. We are currently assessing the impact of the new guidance on our condensed consolidated financial statements.

Revenue Recognition (Tables)

Revenue Recognition (Tables)	9 Months Ended
	Sep. 30, 2019
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 $ 197.1 $ 164.5 $ 549.7 $ 473.6 Service: Security subscription 192.8 157.0 545.5 440.7 Technical support and other 157.6 132.4 446.6 379.9 Total service revenue 350.4 289.4 992.1 820.6 Total revenue $ 547.5 $ 453.9 $ 1,541.8 $ 1,294.2

Financial Instruments and Fai_2

Financial Instruments and Fair Value (Tables)	9 Months Ended
	Sep. 30, 2019
Financial Instruments and Fair Value [Abstract]
Summary of Investments	The following tables summarize our investments (in millions): September 30, 2019 Amortized Cost Unrealized Gains Unrealized Losses Fair Value Corporate debt securities $ 541.5 $ 1.2 $ (0.2 ) $ 542.5 Commercial paper 132.8 0.1 — 132.9 U.S. government and agency securities 221.3 0.3 — 221.6 Certificates of deposit and term deposits (1) 72.0 — — 72.0 Total available-for-sale securities $ 967.6 $ 1.6 $ (0.2 ) $ 969.0 December 31, 2018 Amortized Cost Unrealized Gains Unrealized Losses Fair Value Corporate debt securities $ 299.5 $ — $ (1.2 ) $ 298.3 Commercial paper 102.5 — — 102.5 Certificates of deposit and term deposits (1) 145.8 — — 145.8 U.S. government and agency securities 57.7 — (0.1 ) 57.6 Total available-for-sale securities $ 605.5 $ — $ (1.3 ) $ 604.2 (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, 2019 Less Than 12 Months 12 Months or Greater Total Fair Value Unrealized Losses Fair Value Unrealized Losses Fair Value Unrealized Losses Corporate debt securities $ 67.3 $ (0.1 ) $ 35.9 $ (0.1 ) $ 103.2 $ (0.2 ) December 31, 2018 Less Than 12 Months 12 Months or Greater Total Fair Value Unrealized Losses Fair Value Unrealized Losses Fair Value Unrealized Losses Corporate debt securities $ 150.1 $ (0.2 ) $ 93.5 $ (1.0 ) $ 243.6 $ (1.2 ) Commercial paper 75.6 (0.1 ) — — 75.6 (0.1 ) Certificates of deposit and term deposits 51.7 — — — 51.7 — U.S. government and agency securities 39.0 — 3.5 — 42.5 — Total available-for-sale securities $ 316.4 $ (0.3 ) $ 97.0 $ (1.0 ) $ 413.4 $ (1.3 )
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 $ 764.8 $ 537.2 Due within one to three years 204.2 67.0 Total $ 969.0 $ 604.2
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, 2019 and December 31, 2018 (in millions): September 30, 2019 December 31, 2018 Aggregate Fair Value Quoted Prices in Active Markets For Identical Assets Significant Other Observable Remaining Inputs Significant Other Unobservable Remaining Inputs Aggregate Fair Value Quoted Prices in Active Markets For Identical Assets Significant Other Observable Remaining Inputs Significant Other Unobservable Remaining Inputs (Level 1) (Level 2) (Level 3) (Level 1) (Level 2) (Level 3) Assets: Corporate debt securities $ 542.5 $ — $ 542.5 $ — $ 299.3 $ — $ 299.3 $ — Commercial paper 144.1 — 144.1 — 184.7 — 184.7 — Certificates of deposit and term deposits 72.0 — 72.0 — 217.4 — 217.4 — U.S. government and agency securities 221.6 221.6 — — 57.6 45.3 12.3 — Money market funds 34.2 34.2 — — 58.6 58.6 — — Total $ 1,014.4 $ 255.8 $ 758.6 $ — $ 817.6 $ 103.9 $ 713.7 $ — Reported as: Cash equivalents $ 45.4 $ 213.4 Short-term investments 764.8 537.2 Long-term investments 204.2 67.0 Total $ 1,014.4 $ 817.6

Inventory (Tables)

Inventory (Tables)	9 Months Ended
	Sep. 30, 2019
Inventory Disclosure [Abstract]
Inventory	Inventory consisted of the following (in millions): September 30, December 31, Raw materials $ 7.7 $ 13.3 Finished goods 91.5 76.7 Inventory $ 99.2 $ 90.0

Property and Equipment_Net (Tab

Property and Equipment—Net (Tables)	9 Months Ended
	Sep. 30, 2019
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 $ 75.7 $ 75.7 Building and building improvements 143.6 144.2 Computer equipment and software 113.6 95.9 Leasehold improvements 20.1 17.9 Evaluation units 20.5 20.5 Furniture and fixtures 16.7 15.7 Construction-in-progress 44.4 12.3 Total property and equipment 434.6 382.2 Less: accumulated depreciation (129.1 ) (110.8 ) Property and equipment—net $ 305.5 $ 271.4

Goodwill and Other Intangible_2

Goodwill and Other Intangible Assets - Net (Tables)	9 Months Ended
	Sep. 30, 2019
Goodwill and Intangible Assets Disclosure [Abstract]
Schedule of Finite-Lived and Indefinite-Lived Intangible Assets by Major Class	The following tables present other intangible assets—net as of September 30, 2019 and December 31, 2018 (in millions, except years): September 30, 2019 Weighted-Average Useful Life (in Years) Gross Accumulated Amortization Net Other intangible assets—net: Finite-lived intangible assets: Developed technologies 4.0 $ 34.4 $ 22.7 $ 11.7 Customer relationships 4.4 17.5 15.2 2.3 Total other intangible assets—net $ 51.9 $ 37.9 $ 14.0 December 31, 2018 Weighted-Average Useful Life (in Years) Gross Accumulated Amortization Net Other intangible assets—net: Finite-lived intangible assets: Developed technologies 4.0 $ 34.4 $ 17.0 $ 17.4 Customer relationships 4.4 17.5 12.8 4.7 Total other intangible assets—net $ 51.9 $ 29.8 $ 22.1
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: 2019 (the remainder of 2019) $ 2.2 2020 6.2 2021 3.5 2022 2.1 Total $ 14.0

Net Income Per Share (Tables)

Net Income Per Share (Tables)	9 Months Ended
	Sep. 30, 2019
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 $ 79.8 $ 58.7 $ 211.3 $ 149.6 Denominator: Basic shares: Weighted-average common stock outstanding-basic 171.3 169.8 170.9 168.7 Diluted shares: Weighted-average common stock outstanding-basic 171.3 169.8 170.9 168.7 Effect of potentially dilutive securities: RSUs 2.4 4.2 2.9 3.5 Stock options 1.1 1.6 1.1 1.4 ESPP — 0.1 — 0.1 Weighted-average shares used to compute diluted net income per share 174.8 175.7 174.9 173.7 Net income per share: Basic $ 0.47 $ 0.35 $ 1.24 $ 0.89 Diluted $ 0.46 $ 0.33 $ 1.21 $ 0.86
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 0.2 0.3 0.3 0.6 Stock options 0.7 — 0.6 0.4 ESPP — 0.2 — 0.1 Total 0.9 0.5 0.9 1.1

Leases (Tables)

Leases (Tables)	9 Months Ended
	Sep. 30, 2019
Leases [Abstract]
Components of Lease Expense and Supplemental Cash Flow Information	Supplemental cash flow information related to leases was as follows (in millions): Nine Months Ended September 30, Cash paid for amounts included in the measurement of lease liabilities Operating cash flows used for operating leases $ 11.9 Lease liabilities arising from obtaining right-of-use assets Operating leases $ 12.6 The components of lease expense were as follows (in millions): Three Months Ended Nine Months Ended September 30, September 30, Operating lease expense $ 3.8 $ 11.1 Variable lease expense (1) 0.7 1.9 Short-term lease expense 0.8 2.2 Total lease expense $ 5.3 $ 15.2 (1) Variable lease expense for the three and nine months ended September 30, 2019 predominantly included common area maintenance charges and parking expense.
Supplemental Balance Sheet Information	Supplemental balance sheet information related to our operating leases was as follows (in millions, except lease term and discount rate): Classification September 30, Operating lease ROU assets - non-current Other assets $ 41.0 Operating lease liabilities - current Accrued liabilities $ 13.9 Operating lease liabilities - non-current Other liabilities 27.7 Total operating lease liabilities $ 41.6 Weighted average remaining lease term in years - operating leases 3.9 Weighted average discount rate - operating leases 3.0 %
Maturities of Operating Lease Liabilities	Maturities of operating lease liabilities as of September 30, 2019 were as follows (in millions): Year ending December 31, Amount 2019 (the remainder of 2019) $ 3.5 2020 14.6 2021 10.6 2022 6.2 2023 4.5 Thereafter 4.9 Total lease payments $ 44.3 Less imputed interest (2.7 ) Total $ 41.6
Schedule of Future Principal Contractual Obligations for Operating Lease Commitments	The following table summarizes our future principal contractual obligations for operating lease commitments as of December 31, 2018 (in millions): Year ending December 31, Amount 2019 $ 17.1 2020 12.2 2021 8.5 2022 5.0 2023 3.6 Thereafter 3.7 Total $ 50.1

Commitments and Contingencies (

Commitments and Contingencies (Tables)	9 Months Ended
	Sep. 30, 2019
Commitments and Contingencies Disclosure [Abstract]
Contractual Obligation, Fiscal Year Maturity Schedule	The following table summarizes our future principal contractual obligations as of September 30, 2019 (in millions): Total 2019 2020 2021 2022 2023 Thereafter Inventory purchase commitments $ 241.4 $ 144.5 $ 96.9 $ — $ — $ — $ —

Stockholders' Equity (Tables)

Stockholders' Equity (Tables)	9 Months Ended
	Sep. 30, 2019
Share-based Payment Arrangement [Abstract]
Schedule of Share-based Compensation, Restricted Stock Units Award Activity	The following table summarizes the activity and related information for RSU s for the periods presented below (in millions, except per share amounts): Restricted Stock Units Outstanding Number of Shares Weighted-Average Grant Date Fair Value per Share Balance—December 31, 2018 7.8 $ 46.07 Granted 2.2 83.76 Forfeited (0.5 ) 53.69 Vested (3.0 ) 43.13 Balance—September 30, 2019 6.5 $ 59.36
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 0.9 0.9 Amount withheld for taxes $ 19.6 $ 15.5 $ 76.1 $ 48.0
Schedule of Share-based Payment Award, Stock Options, Valuation Assumptions	The following table summarizes the weighted-average assumptions relating to our employee stock options: Three Months Ended Nine Months Ended September 30, September 30, September 30, September 30, Expected term in years 4.4 4.4 4.4 4.4 Volatility 35.3 % 30.5 % 34.2 % 31.6 % Risk-free interest rate 1.4 % 2.7 % 2.4 % 2.7 % Dividend rate — % — % — % — %
Schedule of Share-based Compensation, Stock Options, Activity	The following table summarizes the stock option activity and related information for the periods presented below (in millions, except exercise prices and contractual life): Options Outstanding Number of Shares Weighted- Average Exercise Price Weighted- Average Remaining Contractual Life (Years) Aggregate Intrinsic Value Balance—December 31, 2018 3.0 $ 35.53 Granted 0.7 84.19 Forfeited (0.1 ) 62.68 Exercised (0.7 ) 29.23 Balance—September 30, 2019 2.9 $ 48.46 Options vested and expected to vest—September 30, 2019 2.9 $ 48.46 4.6 $ 86.5 Options exercisable—September 30, 2019 1.5 $ 33.64 3.5 $ 62.6
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 $ 24.97 $ 22.75 $ 26.96 $ 15.67 Intrinsic value of options exercised 3.2 14.1 40.1 53.6 Fair value of options vested 2.0 1.4 8.2 5.7
Schedule of Employee Service Share-based Compensation, Allocation of Recognized Period Costs	Stock-based compensation expense 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 $ 0.3 $ 1.2 $ 1.1 Cost of service revenue 2.7 2.8 8.4 8.0 Research and development 9.3 9.3 28.7 26.9 Sales and marketing 24.9 26.0 76.6 70.5 General and administrative 5.1 4.8 15.5 13.8 Total stock-based compensation expense $ 42.4 $ 43.2 $ 130.4 $ 120.3
Schedule of Employee Service Share based Compensation Allocation of Recognized Period Costs by Award Type	The following table summarizes stock-based compensation expense by award type (in millions): Three Months Ended Nine Months Ended September 30, September 30, September 30, September 30, RSUs $ 39.5 $ 38.2 $ 120.6 $ 106.1 Stock options 2.9 2.4 8.5 6.7 ESPP — 2.6 1.3 7.5 Total stock-based compensation expense $ 42.4 $ 43.2 $ 130.4 $ 120.3
Income Tax Benefit from Stock Option Plans	Total income tax benefit associated with stock-based compensation that is recognized in the condensed consolidated statements of income is as follows (in millions): Three Months Ended Nine Months Ended September 30, September 30, September 30, September 30, Income tax benefit associated with stock-based compensation $ 9.8 $ 6.8 $ 30.1 $ 19.0

Segment Information (Tables)

Segment Information (Tables)	9 Months Ended
	Sep. 30, 2019
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 $ 182.1 $ 146.8 $ 505.9 $ 425.3 Other Americas (1) 58.6 47.2 160.8 133.8 Total Americas 240.7 194.0 666.7 559.1 Europe, Middle East and Africa (“EMEA”) 200.7 165.4 569.9 474.3 Asia Pacific (“APAC”) 106.1 94.5 305.2 260.8 Total revenue $ 547.5 $ 453.9 $ 1,541.8 $ 1,294.2 (1) In 2019, Canada and Latin America revenue were combined and presented as Other Americas. Prior periods have been reclassified to conform with current period presentation.
Property and equipment by geographic region	Property and Equipment — net September 30, December 31, Americas: United States $ 162.7 $ 132.1 Canada 117.1 113.5 Latin America 0.5 0.4 Total Americas 280.3 246.0 EMEA (1) 16.6 16.2 APAC 8.6 9.2 Total property and equipment—net $ 305.5 $ 271.4 (1) In 2019, France and Other EMEA property and equipment were combined and presented as EMEA. Prior periods have been reclassified to conform with current period presentation.
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 30 % 29 % 31 % 29 % Ingram Micro 11 % 11 % 11 % 10 % The following distributors accounted for 10% or more of net accounts receivable: September 30, December 31, Exclusive Networks Group 32 % 38 % Ingram Micro 11 % * * Represents less than 10%

Accumulated Other Comprehensi_2

Accumulated Other Comprehensive Income (Loss) (Tables)	9 Months Ended
	Sep. 30, 2019
Other Comprehensive Income (Loss), Net of Tax [Abstract]
Schedule of Accumulated Other Comprehensive Income (Loss)	The following table summarizes the changes in accumulated balances of other comprehensive income (loss) (in millions): Unrealized Gains (Losses) on Investments Tax provision (benefit) related to unrealized gains or losses on investments Total Balance—December 31, 2018 $ (1.3 ) $ (0.5 ) $ (0.8 ) Other comprehensive income before reclassifications 2.7 0.7 2.0 Amounts reclassified from accumulated other comprehensive loss — 0.1 (0.1 ) Net current-period other comprehensive income 2.7 0.8 1.9 Balance—September 30, 2019 $ 1.4 $ 0.3 $ 1.1

Summary of Significant Accoun_3

Summary of Significant Accounting Policies , Recent Accounting Pronouncements (Details) - USD ($) $ in Millions	Sep. 30, 2019	Jan. 01, 2019	Jan. 01, 2018
New Accounting Pronouncement, Early Adoption [Line Items]
ROU assets for operating leases	$ 41
Lease liabilities for operating leases	$ 41.6
Cumulative-effect adjustment from adoption of accounting principle		$ 0	$ 117.3
Accounting Standards Update 2016-02
New Accounting Pronouncement, Early Adoption [Line Items]
ROU assets for operating leases		39.1
Lease liabilities for operating leases		40.6
Accumulated Other Comprehensive Income (Loss) [Member]
New Accounting Pronouncement, Early Adoption [Line Items]
Cumulative-effect adjustment from adoption of accounting principle		(0.1)	0
Accumulated Other Comprehensive Income (Loss) [Member] | Accounting Standards Update 2018-02
New Accounting Pronouncement, Early Adoption [Line Items]
Cumulative-effect adjustment from adoption of accounting principle		(0.1)
Retained Earnings (Accumulated Deficit) [Member]
New Accounting Pronouncement, Early Adoption [Line Items]
Cumulative-effect adjustment from adoption of accounting principle		0.1	$ 117.3
Retained Earnings (Accumulated Deficit) [Member] | Accounting Standards Update 2018-02
New Accounting Pronouncement, Early Adoption [Line Items]
Cumulative-effect adjustment from adoption of accounting principle		$ 0.1

Revenue Recognition - Disaggreg

Revenue Recognition - Disaggregated Revenues (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Disaggregation of Revenue [Line Items]
Total revenue	$ 547.5	$ 453.9	$ 1,541.8	$ 1,294.2
Product [Member]
Disaggregation of Revenue [Line Items]
Total revenue	197.1	164.5	549.7	473.6
Service [Member]
Disaggregation of Revenue [Line Items]
Total revenue	350.4	289.4	992.1	820.6
Security Subscription [Member]
Disaggregation of Revenue [Line Items]
Total revenue	192.8	157	545.5	440.7
Technical Support and Other [Member]
Disaggregation of Revenue [Line Items]
Total revenue	$ 157.6	$ 132.4	$ 446.6	$ 379.9

Revenue Recognition (Details)

Revenue Recognition (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018	Dec. 31, 2018
Revenue from Contract with Customer [Abstract]
Deferred revenue recognized in period	$ 211.6	$ 173	$ 752.2	$ 615.3
Remaining performance obligation	1,950		1,950
Allowance for doubtful accounts	0.8		0.8		$ 0.9
Amortization of deferred contract costs	$ 27.5	$ 23.2	$ 78.5	$ 66.3

Revenue Recognition - Performan

Revenue Recognition - Performance Obligation Satisfaction Period (Details) $ in Millions	Sep. 30, 2019USD ($)
Revenue from Contract with Customer [Abstract]
Remaining performance obligation	$ 1,950
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2019-10-01
Revenue from Contract with Customer [Abstract]
Remaining performance obligation	$ 1,060
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]: 2020-10-01
Revenue from Contract with Customer [Abstract]
Remaining performance obligation	$ 890
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, 2019	Dec. 31, 2018
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	$ 967.6	$ 605.5
Unrealized Gains	1.6	0
Unrealized Losses	(0.2)	(1.3)
Fair Value	969	604.2
Available-for-sale Securities, Continuous Unrealized Loss Position [Abstract]
Less Than 12 Months, Fair Value		316.4
Less Than 12 Months, Unrealized Losses		(0.3)
12 Months or Greater, Fair Value		97
12 Months or Greater, Unrealized Losses		(1)
Total, Fair Value		413.4
Total, Unrealized Losses		(1.3)
Available-for-sale Securities, Debt Maturities, Fair Value [Abstract]
Due within one year	764.8	537.2
Due within one to three years	204.2	67
Fair Value	969	604.2
Corporate debt securities [Member]
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	541.5	299.5
Unrealized Gains	1.2	0
Unrealized Losses	(0.2)	(1.2)
Fair Value	542.5	298.3
Available-for-sale Securities, Continuous Unrealized Loss Position [Abstract]
Less Than 12 Months, Fair Value	67.3	150.1
Less Than 12 Months, Unrealized Losses	(0.1)	(0.2)
12 Months or Greater, Fair Value	35.9	93.5
12 Months or Greater, Unrealized Losses	(0.1)	(1)
Total, Fair Value	103.2	243.6
Total, Unrealized Losses	(0.2)	(1.2)
Available-for-sale Securities, Debt Maturities, Fair Value [Abstract]
Fair Value	542.5	298.3
Commercial paper [Member]
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	132.8	102.5
Unrealized Gains	0.1	0
Unrealized Losses	0	0
Fair Value	132.9	102.5
Available-for-sale Securities, Continuous Unrealized Loss Position [Abstract]
Less Than 12 Months, Fair Value		75.6
Less Than 12 Months, Unrealized Losses		(0.1)
12 Months or Greater, Fair Value		0
12 Months or Greater, Unrealized Losses		0
Total, Fair Value		75.6
Total, Unrealized Losses		(0.1)
Available-for-sale Securities, Debt Maturities, Fair Value [Abstract]
Fair Value	132.9	102.5
Certificates of deposit and term deposits [Member]
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	72	145.8
Unrealized Gains	0	0
Unrealized Losses	0	0
Fair Value	72	145.8
Available-for-sale Securities, Continuous Unrealized Loss Position [Abstract]
Less Than 12 Months, Fair Value		51.7
Less Than 12 Months, Unrealized Losses		0
12 Months or Greater, Fair Value		0
12 Months or Greater, Unrealized Losses		0
Total, Fair Value		51.7
Total, Unrealized Losses		0
Available-for-sale Securities, Debt Maturities, Fair Value [Abstract]
Fair Value	72	145.8
U.S. government and agency securities [Member]
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	221.3	57.7
Unrealized Gains	0.3	0
Unrealized Losses	0	(0.1)
Fair Value	221.6	57.6
Available-for-sale Securities, Continuous Unrealized Loss Position [Abstract]
Less Than 12 Months, Fair Value		39
Less Than 12 Months, Unrealized Losses		0
12 Months or Greater, Fair Value		3.5
12 Months or Greater, Unrealized Losses		0
Total, Fair Value		42.5
Total, Unrealized Losses		0
Available-for-sale Securities, Debt Maturities, Fair Value [Abstract]
Fair Value	$ 221.6	$ 57.6

Financial Instruments and Fai_4

Financial Instruments and Fair Value , Fair Value Measurements (Details) - USD ($) $ in Millions	Sep. 30, 2019	Dec. 31, 2018
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value	$ 969	$ 604.2
Corporate debt securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value	542.5	298.3
Commercial paper [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value	132.9	102.5
Certificates of deposit and term deposits [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value	72	145.8
U.S. government and agency securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value	221.6	57.6
Recurring Basis [Member] | Fair Value [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total Assets, Fair Value Disclosure	1,014.4	817.6
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	255.8	103.9
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	758.6	713.7
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	542.5	299.3
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	542.5	299.3
Recurring Basis [Member] | Fair Value [Member] | Corporate debt securities [Member] | Level 3 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value	0	0
Recurring Basis [Member] | Fair Value [Member] | Commercial paper [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value	144.1	184.7
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	144.1	184.7
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	72	217.4
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	72	217.4
Recurring Basis [Member] | Fair Value [Member] | Certificates of deposit and term deposits [Member] | Level 3 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value	0	0
Recurring Basis [Member] | Fair Value [Member] | U.S. government and agency securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value	221.6	57.6
Recurring Basis [Member] | Fair Value [Member] | U.S. government and agency securities [Member] | Level 1 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value	221.6	45.3
Recurring Basis [Member] | Fair Value [Member] | U.S. government and agency securities [Member] | Level 2 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value	0	12.3
Recurring Basis [Member] | Fair Value [Member] | U.S. government and agency securities [Member] | Level 3 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value	0	0
Recurring Basis [Member] | Fair Value [Member] | Money market funds [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value	34.2	58.6
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	34.2	58.6
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] | Reported as [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total Assets, Fair Value Disclosure	1,014.4	817.6
Recurring Basis [Member] | Reported as [Member] | Cash equivalents [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value	45.4	213.4
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	764.8	537.2
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	$ 204.2	$ 67

Inventory (Details)

Inventory (Details) - USD ($) $ in Millions	Sep. 30, 2019	Dec. 31, 2018
Inventory, Net [Abstract]
Raw materials	$ 7.7	$ 13.3
Finished goods	91.5	76.7
Inventory	$ 99.2	$ 90

Property and Equipment_Net (Det

Property and Equipment—Net (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018	Dec. 31, 2018
Property, Plant and Equipment, Net, by Type [Abstract]
Total property and equipment	$ 434.6		$ 434.6		$ 382.2
Less: accumulated depreciation	(129.1)		(129.1)		(110.8)
Property and equipment - net	305.5		305.5		271.4
Depreciation expense	12.8	$ 11.8	37.8	$ 34.9
Land [Member]
Property, Plant and Equipment, Net, by Type [Abstract]
Total property and equipment	75.7		75.7		75.7
Building and building improvements [Member]
Property, Plant and Equipment, Net, by Type [Abstract]
Total property and equipment	143.6		143.6		144.2
Computer equipment and software [Member]
Property, Plant and Equipment, Net, by Type [Abstract]
Total property and equipment	113.6		113.6		95.9
Leasehold improvements [Member]
Property, Plant and Equipment, Net, by Type [Abstract]
Total property and equipment	20.1		20.1		17.9
Evaluation units [Member]
Property, Plant and Equipment, Net, by Type [Abstract]
Total property and equipment	20.5		20.5		20.5
Furniture and fixtures [Member]
Property, Plant and Equipment, Net, by Type [Abstract]
Total property and equipment	16.7		16.7		15.7
Construction-in-progress [Member]
Property, Plant and Equipment, Net, by Type [Abstract]
Total property and equipment	$ 44.4		$ 44.4		$ 12.3

Investments in Privately-Held_2

Investments in Privately-Held Companies (Details) - USD ($) $ in Millions	3 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Dec. 31, 2018
Investments, All Other Investments [Abstract]
Investments in equity securities of privately-held companies	$ 5.3		$ 9.1
Non-cash impairment charge	$ 3.8
Proceeds from sale of equity securities of privately held company		$ 5.2
Recognized gain on sale of equity securities of privately held company		$ 2.2

Business Combinations - Additi

Business Combinations - Additional Information (Details) - USD ($)	Sep. 30, 2019	Dec. 31, 2018	Oct. 22, 2018	Jun. 04, 2018
Business Acquisition [Line Items]
Goodwill not deductible for tax purposes	$ 38,200,000	$ 38,200,000
ZoneFox Holdings Limited [Member]
Business Acquisition [Line Items]
Preliminary purchase price			$ 16,100,000
Goodwill not deductible for tax purposes			12,500,000
Identifiable intangible assets			6,800,000
Liabilities assumed			3,200,000
Cash consideration that may be paid as an earn-out subject to satisfaction of certain performance conditions			$ 2,000,000
Fair value assigned to contingent consideration	$ 0
Bradford [Member]
Business Acquisition [Line Items]
Preliminary purchase price				$ 6,800,000
Goodwill not deductible for tax purposes				11,100,000
Identifiable intangible assets				8,000,000
Liabilities assumed				12,300,000
Cash consideration that may be paid as an earn-out subject to satisfaction of certain performance conditions				$ 2,000,000

Goodwill and Other Intangible_3

Goodwill and Other Intangible Assets - Net - Narrative (Details) - USD ($)	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018	Dec. 31, 2018
Goodwill and Intangible Assets Disclosure [Abstract]
Goodwill	$ 38,200,000		$ 38,200,000		$ 38,200,000
Goodwill impairment			0	$ 0
Amortization expense	$ 2,200,000	$ 2,500,000	$ 8,100,000	$ 6,100,000

Goodwill and Other Intangible_4

Goodwill and Other Intangible Assets - Net - Other Intangible Assets, Net (Details) - USD ($) $ in Millions	9 Months Ended	12 Months Ended
	Sep. 30, 2019	Dec. 31, 2018
Finite-Lived Intangible Assets, Net [Abstract]
Gross	$ 51.9	$ 51.9
Accumulated Amortization	37.9	29.8
Total	$ 14	$ 22.1
Developed Technologies [Member]
Finite-Lived Intangible Assets [Line Items]
Weighted average useful life	4 years	4 years
Finite-Lived Intangible Assets, Net [Abstract]
Gross	$ 34.4	$ 34.4
Accumulated Amortization	22.7	17
Total	$ 11.7	$ 17.4
Customer Relationships [Member]
Finite-Lived Intangible Assets [Line Items]
Weighted average useful life	4 years 4 months 24 days	4 years 4 months 24 days
Finite-Lived Intangible Assets, Net [Abstract]
Gross	$ 17.5	$ 17.5
Accumulated Amortization	15.2	12.8
Total	$ 2.3	$ 4.7

Goodwill and Other Intangible_5

Goodwill and Other Intangible Assets - Net - Estimated Future Amortization Expense (Details) - USD ($) $ in Millions	Sep. 30, 2019	Dec. 31, 2018
Fiscal Years:
2019 (the remainder of 2019)	$ 2.2
2020	6.2
2021	3.5
2022	2.1
Total	$ 14	$ 22.1

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, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Earnings Per Share [Line Items]
Net income	$ 79.8	$ 58.7	$ 211.3	$ 149.6
Basic shares:
Weighted-average common shares outstanding-basic (in shares)	171.3	169.8	170.9	168.7
Diluted shares:
Weighted-average common shares outstanding-basic (in shares)	171.3	169.8	170.9	168.7
Effect of potentially dilutive securities:
Weighted-average shares used to compute diluted net income per share (in shares)	174.8	175.7	174.9	173.7
Basic (in dollars per share)	$ 0.47	$ 0.35	$ 1.24	$ 0.89
Diluted (in dollars per share)	$ 0.46	$ 0.33	$ 1.21	$ 0.86
Restricted Stock Units (RSUs) [Member]
Effect of potentially dilutive securities:
RSUs, stock options, and ESPP (in shares)	2.4	4.2	2.9	3.5
Stock Options [Member]
Effect of potentially dilutive securities:
RSUs, stock options, and ESPP (in shares)	1.1	1.6	1.1	1.4
ESPP [Member]
Effect of potentially dilutive securities:
RSUs, stock options, and ESPP (in shares)	0	0.1	0	0.1

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, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Anti-dilutive securities (in shares)	0.9	0.5	0.9	1.1
Restricted Stock Units (RSUs) [Member] | Share-based Payment Arrangement [Member]
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Anti-dilutive securities (in shares)	0.2	0.3	0.3	0.6
Stock Options [Member] | Share-based Payment Arrangement [Member]
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Anti-dilutive securities (in shares)	0.7	0	0.6	0.4
ESPP [Member] | Share-based Payment Arrangement [Member]
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Anti-dilutive securities (in shares)	0	0.2	0	0.1

Leases (Details)

Leases (Details) - USD ($) $ in Millions	3 Months Ended	9 Months Ended
	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Lessee, Lease, Description [Line Items]
Renewal terms (up to)		5 years
Rent expense	$ 4.4		$ 13.1
Additional minimum lease payments relating to operating office space lease signed but not yet commenced		$ 1.7
Minimum [Member]
Lessee, Lease, Description [Line Items]
Remaining terms (less than for minimum)		1 year
Lease not yet commenced, approximate term		2 years
Maximum [Member]
Lessee, Lease, Description [Line Items]
Remaining terms (less than for minimum)		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, 2019	Sep. 30, 2019
Leases [Abstract]
Operating lease expense	$ 3.8	$ 11.1
Variable lease expense	0.7	1.9
Short-term lease expense	0.8	2.2
Total lease expense	$ 5.3	$ 15.2

Leases - Supplemental Balance S

Leases - Supplemental Balance Sheet Information (Details) $ in Millions	Sep. 30, 2019USD ($)
Leases [Abstract]
Operating lease ROU assets - non-current	$ 41
Operating lease liabilities - current	13.9
Operating lease liabilities - non-current	27.7
Total operating lease liabilities	$ 41.6
Weighted average remaining lease term in years - operating leases	3 years 10 months 24 days
Weighted average discount rate - operating leases	3.00%

Leases - Supplemental Cash Flow

Leases - Supplemental Cash Flow Information (Details) $ in Millions	9 Months Ended
	Sep. 30, 2019USD ($)
Cash paid for amounts included in the measurement of lease liabilities
Operating cash flows used for operating leases	$ 11.9
Lease liabilities arising from obtaining right-of-use assets
Operating leases	$ 12.6

Leases - Maturities of Operatin

Leases - Maturities of Operating Lease Liabilities (Details) $ in Millions	Sep. 30, 2019USD ($)
Leases [Abstract]
2019 (the remainder of 2019)	$ 3.5
2020	14.6
2021	10.6
2022	6.2
2023	4.5
Thereafter	4.9
Total lease payments	44.3
Less imputed interest	(2.7)
Total	$ 41.6

Leases - Future Principal Contr

Leases - Future Principal Contractual Obligations for Operating Lease Commitments (Details) $ in Millions	Dec. 31, 2018USD ($)
Leases [Abstract]
2019	$ 17.1
2020	12.2
2021	8.5
2022	5
2023	3.6
Thereafter	3.7
Total	$ 50.1

Commitments and Contingencies M

Commitments and Contingencies Minimum Operating Lease Payments (Details) $ in Millions	Sep. 30, 2019USD ($)
Inventory purchase commitments:
Inventory purchase commitments, 2019	$ 144.5
Inventory purchase commitments, 2020	96.9
Inventory purchase commitments, 2021	0
Inventory purchase commitments, 2022	0
Inventory purchase commitments, 2023	0
Inventory purchase commitments, Thereafter	0
Inventory purchase commitments	$ 241.4

Commitments and Contingencies_2

Commitments and Contingencies (Details) $ in Millions	Sep. 30, 2019USD ($)
Commitments and Contingencies Disclosure [Abstract]
Inventory purchase commitments	$ 241.4
Other contractual commitments and open purchase orders	$ 12.6

Stockholders' Equity (Details)

Stockholders' Equity (Details) - USD ($) $ / shares in Units, shares in Millions, $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018	Jun. 28, 2019
Stock-based Compensation Plan [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of shares of common stock deregistered (in shares)					46.2
Remaining shares available for grant under the plans	13.6		13.6
Stock Options [Member]
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	35.30%	30.50%	34.20%	31.60%
Risk-free interest rate	1.40%	2.70%	2.40%	2.70%
Dividend rate	0.00%	0.00%	0.00%	0.00%
Number of Shares
Balance - Beginning (in shares)			3
Granted (in shares)			0.7
Forfeited (in shares)			(0.1)
Exercised (in shares)			(0.7)
Balance - Ending (in shares)	2.9		2.9
Weighted- Average Exercise Price
Balance - Beginning (in dollars per share)			$ 35.53
Granted (in dollars per share)			84.19
Forfeited (in dollars per share)			62.68
Exercised (in dollars per share)			29.23
Balance - Ending (in dollars per share)	$ 48.46		$ 48.46
Share-based Compensation Arrangement by Share-based Payment Award, Options, Additional Disclosures [Abstract]
Options vested and expected to vest, Outstanding (in shares)	2.9		2.9
Options vested and expected to vest, Weighted average exercise price (in dollars per share)	$ 48.46		$ 48.46
Options vested and expected to vest, Weighted average remaining contractual life (in years)			4 years 7 months 6 days
Options vested and expected to vest, Aggregate intrinsic value	$ 86.5		$ 86.5
Options exercisable, Outstanding (in shares)	1.5		1.5
Options exercisable, Weighted average exercise price (in dollars per share)	$ 33.64		$ 33.64
Options exercisable, Weighted average remaining contractual life (in years)			3 years 6 months
Options exercisable, Aggregate intrinsic value	$ 62.6		$ 62.6
Compensation cost not yet recognized	$ 26		$ 26
Compensation cost not yet recognized period of recognition			2 years 10 months 24 days
Weighted-average fair value per share granted	$ 24.97	$ 22.75	$ 26.96	$ 15.67
Intrinsic value of options exercised	$ 3.2	$ 14.1	$ 40.1	$ 53.6
Fair value of options vested	$ 2	$ 1.4	$ 8.2	$ 5.7

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, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Weighted-Average Grant Date Fair Value per Share
Shares withheld for taxes	0.2	0.2	0.9	0.9
Amount withheld for taxes	$ 19.6	$ 15.5	$ 76.1	$ 48
Restricted Stock Units (RSUs) [Member]
Number of Shares
Balance, beginning (shares)			7.8
Granted (shares)			2.2
Forfeited (shares)			(0.5)
Vested (shares)			(3)
Balance, ending (shares)	6.5		6.5
Weighted-Average Grant Date Fair Value per Share
Balance, beginning (in dollars per share)			$ 46.07
Granted (in dollars per share)			83.76
Forfeited (in dollars per share)			53.69
Vested (in dollars per share)			43.13
Balance, ending (in dollars per share)	$ 59.36		$ 59.36
Compensation cost not yet recognized	$ 338.5		$ 338.5
Compensation cost not yet recognized period of recognition			2 years 8 months 12 days

Stockholders' Equity , Allocati

Stockholders' Equity , Allocation of Stock-Based Compensation Expense (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]
Total stock-based compensation expense	$ 42.4	$ 43.2	$ 130.4	$ 120.3
Income tax benefit associated with stock-based compensation	9.8	6.8	30.1	19
Restricted Stock Units (RSUs) [Member]
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]
Total stock-based compensation expense	39.5	38.2	120.6	106.1
Stock Options [Member]
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]
Total stock-based compensation expense	2.9	2.4	8.5	6.7
ESPP [Member]
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]
Total stock-based compensation expense	0	2.6	1.3	7.5
Cost of product revenue [Member]
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]
Total stock-based compensation expense	0.4	0.3	1.2	1.1
Cost of service revenue [Member]
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]
Total stock-based compensation expense	2.7	2.8	8.4	8
Research and development [Member]
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]
Total stock-based compensation expense	9.3	9.3	28.7	26.9
Sales and marketing [Member]
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]
Total stock-based compensation expense	24.9	26	76.6	70.5
General and administrative [Member]
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]
Total stock-based compensation expense	$ 5.1	$ 4.8	$ 15.5	$ 13.8

Stockholders' Equity , Share Re

Stockholders' Equity , Share Repurchase Program (Details) - USD ($) $ / shares in Units, shares in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018	Jan. 31, 2016
Share Repurchase Program [Line Items]
Stock repurchased in the period, value	$ 26,500,000	$ 0	$ 117,400,000	$ 117,100,000
Repurchase Program [Member]
Share Repurchase Program [Line Items]
Stock repurchase program, authorized amount					$ 1,500,000,000
Stock repurchased in the period, shares	0.3		1.6
Stock repurchased, average price (in dollars per share)	$ 78.67		$ 73.94
Stock repurchased in the period, value	$ 26,500,000		$ 117,400,000
Stock repurchase program, unused balance	$ 616,300,000		$ 616,300,000

Income Taxes , Narrative (Detai

Income Taxes , Narrative (Details) - USD ($)	Jun. 07, 2019	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018	Dec. 31, 2018
Income Tax Disclosure [Abstract]
Effective tax rate (percent)		24.00%	17.00%	16.00%	6.00%
U.S. federal and state taxes, withholding taxes and foreign taxes		$ 29,600,000	$ 17,700,000	$ 71,600,000	$ 43,400,000
Excess tax benefits on stock compensation		6,900,000	$ 5,800,000	34,600,000	16,200,000
Increase in tax expense due to settlement of foreign tax audits		2,900,000		2,900,000
Increase in unrecognized tax benefits related to Ninth Circuit Altera decision	$ 10,300,000			10,300,000
Unrecognized tax benefits and related interest release				10,000,000	$ 18,000,000
Unrecognized tax benefits		67,700,000		67,700,000		$ 63,500,000
Unrecognized tax benefits that would favorably affect effective tax rate		62,700,000		62,700,000
Accrued interest and penalties related to uncertain tax benefits		13,800,000		13,800,000		$ 11,600,000
Possible decrease in unrecognized tax benefits (up to)		$ 7,100,000		$ 7,100,000

Defined Contribution Plans (Det

Defined Contribution Plans (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
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	$ 1.8	$ 1.4	$ 5.2	$ 4.4

Segment Information (Details)

Segment Information (Details) $ in Millions	3 Months Ended		9 Months Ended		12 Months Ended
	Sep. 30, 2019USD ($)	Sep. 30, 2018USD ($)	Sep. 30, 2019USD ($)segment_managerreportable_segmentbusiness_activityoperating_segment	Sep. 30, 2018USD ($)	Dec. 31, 2018USD ($)
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	$ 547.5	$ 453.9	$ 1,541.8	$ 1,294.2
Property and equipment - net	$ 305.5		$ 305.5		$ 271.4
Exclusive Networks Group [Member] | Customer Concentration Risk [Member] | Revenue [Member]
Segment Reporting Information [Line Items]
Concentration (percent)	30.00%	29.00%	31.00%	29.00%
Exclusive Networks Group [Member] | Customer Concentration Risk [Member] | Accounts Receivable [Member]
Segment Reporting Information [Line Items]
Concentration (percent)			32.00%		38.00%
Ingram Micro [Member] | Customer Concentration Risk [Member] | Revenue [Member]
Segment Reporting Information [Line Items]
Concentration (percent)	11.00%	11.00%	11.00%	10.00%
Ingram Micro [Member] | Customer Concentration Risk [Member] | Accounts Receivable [Member]
Segment Reporting Information [Line Items]
Concentration (percent)			11.00%
Americas [Member]
Segment Reporting Information [Line Items]
Total revenue	$ 240.7	$ 194	$ 666.7	$ 559.1
Property and equipment - net	280.3		280.3		$ 246
U.S.
Segment Reporting Information [Line Items]
Total revenue	182.1	146.8	505.9	425.3
Property and equipment - net	162.7		162.7		132.1
Canada
Segment Reporting Information [Line Items]
Property and equipment - net	117.1		117.1		113.5
Latin America
Segment Reporting Information [Line Items]
Property and equipment - net	0.5		0.5		0.4
Other Americas
Segment Reporting Information [Line Items]
Total revenue	58.6	47.2	160.8	133.8
EMEA
Segment Reporting Information [Line Items]
Total revenue	200.7	165.4	569.9	474.3
Property and equipment - net	16.6		16.6		16.2
APAC
Segment Reporting Information [Line Items]
Total revenue	106.1	$ 94.5	305.2	$ 260.8
Property and equipment - net	$ 8.6		$ 8.6		$ 9.2

Accumulated Other Comprehensi_3

Accumulated Other Comprehensive Income (Loss) (Changes in Accumulated Balances of Other Comprehensive Loss) (Details) $ in Millions	9 Months Ended
	Sep. 30, 2019USD ($)
Accumulated Other Comprehensive (Loss) Income [Roll Forward]
Beginning balance	$ (0.8)
Other comprehensive income before reclassifications	2
Amounts reclassified from accumulated other comprehensive loss	(0.1)
Net current-period other comprehensive income	1.9
Ending balance	1.1
Tax provision (benefit) related to unrealized gains or losses on investments
Beginning balance, tax	(0.5)
Other comprehensive income before reclassifications, tax	0.7
Amounts reclassified from accumulated other comprehensive income, tax	0.1
Net current-period other comprehensive income, tax	0.8
Ending balance, tax	0.3
Unrealized Gains and Losses on Investments [Member]
Accumulated Other Comprehensive (Loss) Income [Roll Forward]
Beginning balance	(1.3)
Other comprehensive income before reclassifications	2.7
Amounts reclassified from accumulated other comprehensive loss	0
Net current-period other comprehensive income	2.7
Ending balance	$ 1.4

Subsequent Events (Details)

Subsequent Events (Details) - USD ($) $ / shares in Units, shares in Millions, $ in Millions	Oct. 28, 2019	Oct. 31, 2019	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Subsequent Event [Line Items]
Stock repurchased in the period, value			$ 26.5	$ 0	$ 117.4	$ 117.1
Repurchase Program [Member]
Subsequent Event [Line Items]
Stock repurchased in the period, shares			0.3		1.6
Stock repurchased in the period, value			$ 26.5		$ 117.4
Stock repurchased, average price (in dollars per share)			$ 78.67		$ 73.94
Subsequent Event [Member] | Repurchase Program [Member]
Subsequent Event [Line Items]
Stock repurchased in the period, shares		0.3
Stock repurchased in the period, value		$ 23.5
Stock repurchased, average price (in dollars per share)		$ 77.39
Subsequent Event [Member] | EnSilo
Subsequent Event [Line Items]
Initial consideration, subject to certain adjustments	$ 20