F5 (FFIV) 10-Q 6 May 20 2020 Q2 Quarterly report Financial data

Cover Page

Cover Page - shares	3 Months Ended	6 Months Ended
	Mar. 31, 2020	Mar. 31, 2020	May 01, 2020
Cover [Abstract]
Document Type		10-Q
Document Quarterly Report		true
Document Period End Date		Mar. 31, 2020
Document Transition Report		false
Entity File Number		000-26041
Entity Registrant Name		F5 NETWORKS, INC.
Entity Incorporation, State or Country Code		WA
Entity Tax Identification Number		91-1714307
Entity Address, Address Line One		801 5th Avenue
Entity Address, City or Town		Seattle
Entity Address, State or Province		WA
Entity Address, Postal Zip Code		98104
City Area Code		206
Local Phone Number		272-5555
Title of 12(b) Security		Common stock, no par value
Trading Symbol		FFIV
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			60,896,541
Entity Central Index Key		0001048695
Current Fiscal Year End Date		--09-30
Document Fiscal Year Focus		2020
Document Fiscal Period Focus	Q2
Amendment Flag		false

Consolidated Balance Sheets

Consolidated Balance Sheets - USD ($) $ in Thousands	Mar. 31, 2020	Sep. 30, 2019
Current assets
Cash and cash equivalents	$ 572,888	$ 599,219
Short-term investments	248,257	373,063
Accounts receivable, net of allowances of $3,305 and $3,259	338,655	322,029
Inventories	30,942	34,401
Other current assets	217,989	182,874
Total current assets	1,408,731	1,511,586
Property and equipment, net	232,006	223,426
Operating lease right-of-use assets	327,436	0
Long-term investments	204,969	358,402
Deferred tax assets	47,230	27,701
Goodwill	1,864,991	1,065,379
Other assets, net	355,614	203,781
Total assets	4,440,977	3,390,275
Current liabilities
Accounts payable	56,200	62,627
Accrued liabilities	286,902	235,869
Deferred revenue	889,629	807,030
Current portion of long-term debt	19,275	0
Total current liabilities	1,252,006	1,105,526
Deferred tax liabilities	221	313
Deferred revenue, long-term	391,475	391,086
Operating lease liabilities, long-term	357,645	0
Long-term debt	378,685	0
Other long-term liabilities	62,751	131,853
Total long-term liabilities	1,190,777	523,252
Commitments and contingencies (Note 9)
Shareholders' equity
Preferred stock, no par value; 10,000 shares authorized, no shares outstanding	0	0
Common stock, no par value; 200,000 shares authorized, 60,629 and 60,367 shares issued and outstanding	223,101	142,597
Accumulated other comprehensive loss	(22,903)	(19,190)
Retained earnings	1,797,996	1,638,090
Total shareholders' equity	1,998,194	1,761,497
Total liabilities and shareholders' equity	$ 4,440,977	$ 3,390,275

Consolidated Balance Sheets (Pa

Consolidated Balance Sheets (Parenthetical) - USD ($) $ in Thousands	Mar. 31, 2020	Sep. 30, 2019
Statement of Financial Position [Abstract]
Accounts receivable, allowances	$ 3,305	$ 3,259
Preferred stock, par value (dollars per share)	$ 0	$ 0
Preferred stock, shares authorized	10,000,000	10,000,000
Preferred stock, shares outstanding	0	0
Common stock, par value (dollars per share)	$ 0	$ 0
Common stock, shares authorized	200,000,000	200,000,000
Common stock, shares issued	60,629,000	60,367,000

Consolidated Income Statements

Consolidated Income Statements - USD ($) shares in Thousands, $ in Thousands	3 Months Ended		6 Months Ended
	Mar. 31, 2020	Mar. 31, 2019	Mar. 31, 2020	Mar. 31, 2019
Net revenues
Revenue from contract with customer, excluding assessed tax	$ 583,449	$ 544,895	$ 1,152,754	$ 1,088,665
Cost of net revenues
Cost of net revenues	101,238	88,178	189,880	174,892
Gross profit	482,211	456,717	962,874	913,773
Operating expenses
Sales and marketing	215,472	170,954	410,991	335,213
Research and development	109,028	96,314	205,033	188,352
General and administrative	74,013	46,656	133,017	89,199
Restructuring charges	0	0	7,800	0
Total	398,513	313,924	756,841	612,764
Income from operations	83,698	142,793	206,033	301,009
Other (loss) income, net	(141)	7,434	5,079	14,529
Income before income taxes	83,557	150,227	211,112	315,538
Provision for income taxes	22,178	34,140	51,206	68,546
Net income	$ 61,379	$ 116,087	$ 159,906	$ 246,992
Net income per share — basic (dollars per share)	$ 1.01	$ 1.94	$ 2.63	$ 4.12
Weighted average shares — basic (shares)	60,869	59,686	60,758	59,954
Net income per share — diluted (dollars per share)	$ 1	$ 1.93	$ 2.62	$ 4.09
Weighted average shares — diluted (shares)	61,084	60,029	61,017	60,374
Product
Net revenues
Revenue from contract with customer, excluding assessed tax	$ 259,538	$ 237,859	$ 494,074	$ 471,736
Cost of net revenues
Cost of net revenues	53,086	43,547	95,204	85,957
Service
Net revenues
Revenue from contract with customer, excluding assessed tax	323,911	307,036	658,680	616,929
Cost of net revenues
Cost of net revenues	$ 48,152	$ 44,631	$ 94,676	$ 88,935

Consolidated Statements Of Comp

Consolidated Statements Of Comprehensive Income - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Mar. 31, 2020	Mar. 31, 2019	Mar. 31, 2020	Mar. 31, 2019
Statement of Comprehensive Income [Abstract]
Net income	$ 61,379	$ 116,087	$ 159,906	$ 246,992
Other comprehensive (loss) income:
Foreign currency translation adjustment	(1,586)	(197)	(952)	(56)
Available-for-sale securities:
Unrealized (losses) gains on securities, net of taxes of $(368) and $679 for the three months ended March 31, 2020 and 2019, respectively, and $(344) and $743 for the six months ended March 31, 2020 and 2019, respectively	(2,999)	2,849	(2,831)	2,893
Reclassification adjustment for realized losses included in net income, net of taxes of $(17) and $0 for the three months ended March 31, 2020 and 2019, respectively, and $(18) and $0 for the six months ended March 31, 2020 and 2019, respectively	58	0	70	0
Net change in unrealized (losses) gains on available-for-sale securities, net of tax	(2,941)	2,849	(2,761)	2,893
Total other comprehensive (loss) income	(4,527)	2,652	(3,713)	2,837
Comprehensive income	$ 56,852	$ 118,739	$ 156,193	$ 249,829

Consolidated Statements Of Co_2

Consolidated Statements Of Comprehensive Income (Parenthetical) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Mar. 31, 2020	Mar. 31, 2019	Mar. 31, 2020	Mar. 31, 2019
Statement of Comprehensive Income [Abstract]
Tax effect of unrealized gain (loss) on securities	$ (368)	$ 679	$ (344)	$ 743
Tax effect of reclassification adjustment for realized (gains) losses	$ (17)	$ 0	$ (18)	$ 0

Consolidated Statements of Shar

Consolidated Statements of Shareholders' Equity Statement - USD ($) shares in Thousands, $ in Thousands	Total	Common Stock	AOCI Attributable to Parent	Retained Earnings
Beginning Balance (in shares) at Sep. 30, 2018		60,215
Beginning Balance at Sep. 30, 2018	$ 1,285,492	$ 20,427	$ (22,178)	$ 1,287,243
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Exercise of employee stock options (in shares)		135
Exercise of employee stock options	18,901	$ 18,901
Issuance of restricted stock (in shares)		531
Issuance of restricted stock	$ 0
Repurchase of common stock (in shares)	(1,186)
Repurchase of common stock	$ (201,045)	$ (88,110)		(112,935)
Stock-based compensation	78,183	$ 78,183
Net income	246,992			246,992
Other comprehensive loss	2,837		2,837
Ending Balance ( in shares) at Mar. 31, 2019		59,695
Ending Balance at Mar. 31, 2019	1,467,408	$ 29,401	(19,341)	1,457,348
Beginning Balance (in shares) at Dec. 31, 2018		60,058
Beginning Balance at Dec. 31, 2018	1,409,188	$ 13,277	(21,993)	1,417,904
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Issuance of restricted stock (in shares)		254
Issuance of restricted stock	0
Repurchase of common stock (in shares)		(617)
Repurchase of common stock	(100,013)	$ (23,370)		(76,643)
Stock-based compensation	39,494	$ 39,494
Net income	116,087			116,087
Other comprehensive loss	2,652		2,652
Ending Balance ( in shares) at Mar. 31, 2019		59,695
Ending Balance at Mar. 31, 2019	$ 1,467,408	$ 29,401	(19,341)	1,457,348
Beginning Balance (in shares) at Sep. 30, 2019	60,367	60,367
Beginning Balance at Sep. 30, 2019	$ 1,761,497	$ 142,597	(19,190)	1,638,090
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Issuance of stock under employee stock purchase plan (in shares)		31
Exercise of employee stock options	789	$ 789
Exercise of employee stock options (in shares)		169
Exercise of employee stock options	20,670	$ 20,670
Issuance of restricted stock (in shares)		504
Issuance of restricted stock	$ 0
Repurchase of common stock (in shares)	(442)
Repurchase of common stock	$ (50,009)	$ (50,009)
Stock-based compensation	109,054	$ 109,054
Net income	159,906			159,906
Other comprehensive loss	$ (3,713)		(3,713)
Ending Balance ( in shares) at Mar. 31, 2020	60,629	60,629
Ending Balance at Mar. 31, 2020	$ 1,998,194	$ 223,101	(22,903)	1,797,996
Beginning Balance (in shares) at Dec. 31, 2019		60,803
Beginning Balance at Dec. 31, 2019	1,929,458	$ 211,217	(18,376)	1,736,617
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Exercise of employee stock options (in shares)		20
Exercise of employee stock options	498	$ 498
Issuance of restricted stock (in shares)		248
Issuance of restricted stock	$ 0
Repurchase of common stock (in shares)	(442)
Repurchase of common stock	$ (50,009)	$ (50,009)
Stock-based compensation	61,395	$ 61,395
Net income	61,379			61,379
Other comprehensive loss	$ (4,527)		(4,527)
Ending Balance ( in shares) at Mar. 31, 2020	60,629	60,629
Ending Balance at Mar. 31, 2020	$ 1,998,194	$ 223,101	$ (22,903)	$ 1,797,996

Consolidated Statements Of Cash

Consolidated Statements Of Cash Flows - USD ($) $ in Thousands	6 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
Operating activities
Net income	$ 159,906	$ 246,992
Adjustments to reconcile net income to net cash provided by operating activities:
Stock-based compensation	98,447	78,183
Depreciation and amortization	43,112	28,246
Non-cash operating lease costs	18,970
Other	54	(43)
Deferred income taxes	5,353	3,606
Changes in operating assets and liabilities (excluding effects of the acquisition of businesses):
Accounts receivable	4,317	(24,419)
Inventories	3,459	(2,895)
Other current assets	(19,603)	(35,735)
Other assets	(4,298)	2,683
Accounts payable and accrued liabilities	(1,936)	16,746
Deferred revenue	43,987	78,046
Lease liabilities	(25,948)
Net cash provided by operating activities	325,820	391,410
Investing activities
Purchases of investments	(195,123)	(211,087)
Maturities of investments	237,892	351,600
Sales of investments	232,255	2,499
Acquisition of businesses, net of cash acquired	(955,574)	0
Purchases of property and equipment	(35,463)	(50,056)
Net cash (used in) provided by investing activities	(716,013)	92,956
Financing activities
Proceeds from the exercise of stock options and purchases of stock under employee stock purchase plan	21,443	18,900
Repurchase of common stock	(50,009)	(201,045)
Proceeds from term debt agreement	400,000	0
Payments for debt issuance costs	(3,040)	0
Net cash provided by (used in) financing activities	368,394	(182,145)
Net (decrease) increase in cash, cash equivalents and restricted cash	(21,799)	302,221
Effect of exchange rate changes on cash, cash equivalents and restricted cash	(1,090)	(265)
Cash, cash equivalents and restricted cash, beginning of period	602,254	425,894
Cash, cash equivalents and restricted cash, end of period	579,365	727,850
Supplemental disclosures of cash flow information
Cash paid for amounts included in the measurement of operating lease liabilities	30,067
Cash paid for interest on long-term debt	2,089
Supplemental disclosures of non-cash activities
Right-of-use assets obtained in exchange for lease obligations	399,203
Capitalized leasehold improvements paid directly by landlord	$ 0	$ 28,814

Summary of Significant Accounti

Summary of Significant Accounting Policies	6 Months Ended
	Mar. 31, 2020
Accounting Policies [Abstract]
Summary of Significant Accounting Policies	Summary of Significant Accounting Policies Description of Business F5 Networks, Inc. (the "Company") is a leading provider of multi-cloud application services which enable its customers to develop, deploy, operate, secure, and govern applications in any architecture, from on-premises to the public cloud. The Company's cloud, software, and hardware solutions enable its customers to deliver digital experiences to their customers faster, reliably, and at scale. The Company's enterprise-grade application services are available as cloud-based, software-as-a-service, and software-only solutions optimized for multi-cloud environments, with modules that can run independently, or as part of an integrated solution on its high-performance appliances. In connection with its solutions, the Company offers a broad range of professional services, including consulting, training, installation, maintenance, and other technical support services. On January 24, 2020, the Company completed the acquisition of Shape Security, Inc. ("Shape"), a leader in online fraud and abuse prevention, adding protection from automated attacks, botnets, and targeted fraud to F5's world-class portfolio of application services. Basis of Presentation The year-end consolidated balance sheet data was derived from audited financial statements but does not include all disclosures required by accounting principles generally accepted in the United States of America ("GAAP"). In the opinion of management, the unaudited consolidated financial statements reflect all adjustments, consisting only of normal recurring adjustments, necessary for their fair statement in conformity with accounting principles generally accepted in the United States of America. Certain information and footnote disclosures normally included in annual financial statements have been condensed or omitted in accordance with the rules and regulations of the Securities and Exchange Commission ("SEC"). The information included in this Form 10-Q should be read in conjunction with Management’s Discussion and Analysis of Financial Condition and Results of Operations and financial statements and notes thereto included in the Company’s Annual Report on Form 10-K for the fiscal year ended September 30, 2019 . Certain prior year amounts have been reclassified to conform to the current year presentation in the Consolidated Statements of Cash Flows. The reclassified amounts are considered immaterial and there was no change to total cash from operating, investing or financing activities as a result. There have been no material changes to the Company's significant accounting policies as of and for the three and six months ended March 31, 2020 , except for the accounting policy for leases that was updated as a result of adopting Accounting Standards Update 2016-02, Leases (Topic 842) (ASU 2016-02) and related standards. For more information, refer to the "Recently Adopted Accounting Standards" section of Note 1 and Note 8 - Leases. In December 2019, a novel strain of coronavirus (“COVID-19“) was first identified, and in March 2020, the World Health Organization categorized COVID-19 as a pandemic. The Company assessed the impact that COVID-19 had on its results of operations, including, but not limited to an assessment of its allowance for doubtful accounts, the carrying value of short-term and long-term investments, the carrying value of goodwill and other long-lived assets, and the impact to revenue recognition and cost of revenues. For the quarter ended March 31, 2020, the Company’s analysis shows COVID-19 had a net-neutral impact on its results of operations. The Company is actively monitoring the impact to the results of its business operations, and may make decisions required by federal, state or local authorities, or that are determined to be in the best interests of its employees, customers, partners, suppliers and stockholders. As of the filing date, the extent to which the COVID-19 pandemic may impact the Company’s financial condition or results of operations remains uncertain. Recently Adopted Accounting Standards In February 2016, the Financial Accounting Standards Board ("FASB") issued ASU 2016-02, Leases (Topic 842) (ASU 2016-02), which requires lessees to recognize on the balance sheet a right-of-use asset, representing its right to use the underlying asset for the lease term, and a corresponding lease liability for all leases with terms greater than twelve months. The Company's leases consist primarily of operating leases for its offices and lab spaces. The Company does not have finance leases. The guidance also requires qualitative and quantitative disclosures designed to assess the amount, timing and uncertainty of cash flows arising from leases. The Company adopted this standard on October 1, 2019 on a modified retrospective basis by applying the new standard to its lease portfolio as of October 1, 2019, while continuing to apply legacy guidance in the comparative periods. The adoption of this standard had no impact on the consolidated income statements and consolidated statements of cash flows. Refer to Note 8 - Leases for further discussion. Upon adoption of the standard, the Company elected the package of three expedients for existing and expired contracts to not reassess: the existence of additional leases, lease classification, or the treatment of initial direct costs. The Company also applies the short-term lease exemption for leases with an original expected term of 12 months or less and expenses such leases month-to-month and does not record a right-of-use asset or lease liability. Short-term lease activity under the exception is not significant. Additionally, the Company does not separate lease and non-lease components in the allocation of minimum lease payments for its office space and equipment leases, as such separation is not significant. The Company includes in minimum lease payments, fixed and variable payments based on a rate or index, but excludes variable payments based on satisfying future benchmarks or actual future costs incurred; such amounts are expensed as incurred. To calculate the net present value, the Company applied an incremental borrowing rate. This incremental borrowing rate is determined using a portfolio approach based on the rate of interest the Company would pay to borrow an amount equal to the lease payments on a collateralized basis over a similar term . Renewal options to extend lease terms are excluded from the minimum lease term at lease commencement. Recently Issued Accounting Pronouncements In June 2016, the FASB issued ASU 2016-13, Financial Instruments - Credit Losses (Topic 326): Measurement of Credit Losses on Financial Instruments (ASU 2016-13), which replaces the incurred loss impairment methodology in current GAAP with a methodology that reflects expected credit losses. The new standard is effective for fiscal years, and interim periods within those fiscal years, beginning after December 15, 2019. Early adoption is permitted. The Company does not anticipate that the adoption of this standard will have a material impact on its consolidated financial statements. In August 2018, the FASB issued ASU 2018-15, Intangibles - Goodwill and Other - Internal-Use Software (Subtopic 350-40) (ASU 2018-15), which aligns the requirements for capitalizing implementation costs incurred in a hosting arrangement that is a service contract with the requirements for capitalizing implementation costs incurred to develop or obtain internal-use software, and hosting arrangements that include an internal use software license. The accounting for the service element of a hosting arrangement that is a service contract is not affected by the amendments in this update. The new standard is effective for fiscal years, and interim periods within those fiscal years, beginning after December 15, 2019. Early adoption is permitted. The Company does not anticipate that the adoption of this standard will have a material impact on its consolidated financial statements.

Revenue from Contracts with Cus

Revenue from Contracts with Customers	6 Months Ended
	Mar. 31, 2020
Revenue from Contract with Customer [Abstract]
Revenue from Contracts with Customers	Revenue from Contracts with Customers Capitalized Contract Acquisition Costs The table below shows significant movements in capitalized contract acquisition costs (current and noncurrent) for the six months ended March 31, 2020 (in thousands): Balance, September 30, 2019 $ 59,446 Additional capitalized contract acquisition costs deferred 21,836 Amortization of capitalized contract acquisition costs (16,972 ) Balance, March 31, 2020 $ 64,310 Amortization of capitalized contract acquisition costs was $8.3 million and $7.2 million for the three months ended March 31, 2020 and 2019, respectively, and $17.0 million and $14.4 million for the six months ended March 31, 2020 and 2019, respectively, and is recorded in Sales and Marketing expense in the accompanying consolidated income statements. There was no impairment of any capitalized contract acquisition costs during any period presented. Contract Balances Timing may differ between the satisfaction of performance obligations and the invoicing and collection of amounts related to the Company's contracts with customers. The Company records assets for amounts related to performance obligations that are satisfied but not yet billed and/or collected, in addition to contracts that have started, but not yet been fully billed. These assets are recorded as contract assets rather than receivables when receipt of the consideration is conditional on something other than the passage of time. Liabilities are recorded for amounts that are collected in advance of the satisfaction of performance obligations. These liabilities are classified as current and non-current deferred revenue. The table below shows significant movements in contract assets (current and noncurrent) for the six months ended March 31, 2020 (in thousands): Balance, September 30, 2019 $ 132,492 Revenue recognized during period but not yet billed 13,998 Contract asset additions 38,060 Contract assets acquired through the purchase of Shape 6,045 Contract assets reclassified to accounts receivable (33,211 ) Balance, March 31, 2020 $ 157,384 As of March 31, 2020 , contract assets that are expected to be reclassified to receivables within the next 12 months are included in other current assets, with those expected to be transferred to receivables in more than 12 months included in other assets. There were no impairments of contract assets during the six months ended March 31, 2020 and 2019. The table below shows significant movements in the deferred revenue balances (current and noncurrent) for the six months ended March 31, 2020 (in thousands): Balance, September 30, 2019 $ 1,198,116 Amounts billed but not recognized as revenues 587,983 Amounts acquired through the purchase of Shape 39,000 Revenues recognized related to the opening balance of deferred revenue (543,995 ) Balance, March 31, 2020 $ 1,281,104 The Company's contract assets and liabilities are reported in a net position on a contract by contract basis at the end of each reporting period. Remaining Performance Obligations Remaining performance obligations represent the amount of the transaction price under contracts with customers that are attributable to performance obligations that are unsatisfied or partially satisfied at the reporting date. As of March 31, 2020, the total non-cancelable remaining performance obligations under the Company's contracts with customers was approximately $1.3 billion and the Company expects to recognize revenues on approximately 69.4% of these remaining performance obligations over the next 12 months, 18.6% in year two, and the remaining balance thereafter. See Note 12, Segment Information, for disaggregated revenue by significant customer and geographic region.

Fair Value Measurements

Fair Value Measurements	6 Months Ended
	Mar. 31, 2020
Fair Value Disclosures [Abstract]
Fair Value Measurements	Fair Value Measurements In accordance with the authoritative guidance on fair value measurements and disclosure under GAAP, the Company determines fair value using a fair value hierarchy that distinguishes between market participant assumptions developed based on market data obtained from sources independent of the reporting entity, and the reporting entity’s own assumptions about market participant assumptions developed based on the best information available in the circumstances and expands disclosure about fair value measurements. Fair value is the price that would be received to sell an asset or paid to transfer a liability in the principal or most advantageous market for the asset or liability in an orderly transaction between market participants at the measurement date, essentially the exit price. The levels of fair value hierarchy are: Level 1: Quoted prices in active markets for identical assets and liabilities at the measurement date that the Company has the ability to access. Level 2: Observable inputs other than quoted prices included in Level 1, such as quoted prices for similar assets and liabilities in active markets; quoted prices for identical or similar assets and liabilities in markets that are not active; or other inputs that are observable or can be corroborated by observable market data. Level 3: Unobservable inputs for which there is little or no market data available. These inputs reflect management's assumptions of what market participants would use in pricing the asset or liability. Level 1 investments are valued based on quoted market prices in active markets and include the Company's cash equivalent investments. Level 2 investments, which include investments that are valued based on quoted prices in markets that are not active, broker or dealer quotations, actual trade data, benchmark yields or alternative pricing sources with reasonable levels of price transparency, include the Company's certificates of deposit, corporate bonds and notes, municipal bonds and notes, U.S. government securities, U.S. government agency securities and international government securities. Fair values for the Company's level 2 investments are based on similar assets without applying significant judgments. In addition, all of the Company's level 2 investments have a sufficient level of trading volume to demonstrate that the fair values used are appropriate for these investments. A financial instrument's level within the fair value hierarchy is based upon the lowest level of any input that is significant to the fair value measurement. However, the determination of what constitutes "observable" requires significant judgment by the Company. The Company considers observable data to be market data which is readily available, regularly distributed or updated, reliable and verifiable, not proprietary, and provided by independent sources that are actively involved in the relevant market. The Company's financial assets measured at fair value on a recurring basis subject to the disclosure requirements at March 31, 2020 , were as follows (in thousands): Fair Value Measurements at Reporting Date Using Quoted Prices in Active Markets for Identical Securities (Level 1) Significant Other Observable Inputs (Level 2) Significant Unobservable Inputs (Level 3) Fair Value at Cash equivalents $ 100,355 $ — $ — $ 100,355 Short-term investments Available-for-sale securities — certificates of deposits — 493 — 493 Available-for-sale securities — corporate bonds and notes — 201,811 — 201,811 Available-for-sale securities — municipal bonds and notes — 8,057 — 8,057 Available-for-sale securities — U.S. government securities — 27,232 — 27,232 Available-for-sale securities — U.S. government agency securities — 10,664 — 10,664 Long-term investments Available-for-sale securities — corporate bonds and notes — 180,625 — 180,625 Available-for-sale securities — U.S. government agency securities — 24,344 — 24,344 Total $ 100,355 $ 453,226 $ — $ 553,581 The Company's financial assets measured at fair value on a recurring basis subject to the disclosure requirements at September 30, 2019 , were as follows (in thousands): Fair Value Measurements at Reporting Date Using Quoted Prices in Active Markets for Identical Securities (Level 1) Significant Other Observable Inputs (Level 2) Significant Unobservable Inputs (Level 3) Fair Value at September 30, 2019 Cash equivalents $ 140,238 $ 153,404 $ — $ 293,642 Short-term investments Available-for-sale securities — certificates of deposits — 249 — 249 Available-for-sale securities — corporate bonds and notes — 259,547 — 259,547 Available-for-sale securities — municipal bonds and notes — 12,129 — 12,129 Available-for-sale securities — U.S. government securities — 78,992 — 78,992 Available-for-sale securities — U.S. government agency securities — 22,146 — 22,146 Long-term investments Available-for-sale securities — corporate bonds and notes — 298,916 — 298,916 Available-for-sale securities — municipal bonds and notes — 2,524 — 2,524 Available-for-sale securities — U.S. government securities — 5,515 — 5,515 Available-for-sale securities — U.S. government agency securities — 51,447 — 51,447 Total $ 140,238 $ 884,869 $ — $ 1,025,107 The Company uses the fair value hierarchy for financial assets and liabilities. The fair value of the Company's borrowings under its Term Loan Facility approximate the carrying value based on the borrowing rates currently available to the Company for loans with similar terms using Level 2 inputs. The carrying amounts of other current financial assets and other current financial liabilities approximate fair value due to their short-term nature. The Company's non-financial assets and liabilities, which include goodwill, intangible assets, and long-lived assets, are not required to be carried at fair value on a recurring basis. These non-financial assets and liabilities are measured at fair value on a non-recurring basis when there is an indicator of impairment, and they are recorded at fair value only when impairment is recognized. The Company reviews goodwill and intangible assets for impairment annually, during the second quarter of each fiscal year, or as circumstances indicate the possibility of impairment. The Company monitors the carrying value of long-lived assets for impairment whenever events or changes in circumstances indicate its carrying amount may not be recoverable. Included in the Company’s impairment considerations for non-financial assets and liabilities in the current quarter were the potential impacts of the COVID-19 pandemic. During the three and six months ended March 31, 2020 and 2019, the Company did not recognize any impairment charges related to goodwill, intangible assets, or long-lived assets.

Short-Term and Long-Term Invest

Short-Term and Long-Term Investments	6 Months Ended
	Mar. 31, 2020
Investments, Debt and Equity Securities [Abstract]
Short-Term and Long-Term Investments	Short-Term and Long-Term Investments Short-term investments consist of the following (in thousands): March 31, 2020 Cost or Cost Gross Gains Gross Losses Fair Value Certificates of deposits $ 493 $ — $ — $ 493 Corporate bonds and notes 202,270 259 (718 ) 201,811 Municipal bonds and notes 8,056 10 (9 ) 8,057 U.S. government securities 27,007 225 — 27,232 U.S. government agency securities 10,627 37 — 10,664 $ 248,453 $ 531 $ (727 ) $ 248,257 September 30, 2019 Cost or Cost Gross Gains Gross Losses Fair Value Certificates of deposits $ 249 $ — $ — $ 249 Corporate bonds and notes 259,242 402 (97 ) 259,547 Municipal bonds and notes 12,128 6 (5 ) 12,129 U.S. government securities 78,988 18 (14 ) 78,992 U.S. government agency securities 22,138 9 (1 ) 22,146 $ 372,745 $ 435 $ (117 ) $ 373,063 Long-term investments consist of the following (in thousands): March 31, 2020 Cost or Cost Gross Gains Gross Losses Fair Value Corporate bonds and notes $ 183,265 $ 259 $ (2,899 ) $ 180,625 U.S. government agency securities 24,276 71 (3 ) 24,344 $ 207,541 $ 330 $ (2,902 ) $ 204,969 September 30, 2019 Cost or Cost Gross Gains Gross Losses Fair Value Corporate bonds and notes $ 298,888 $ 469 $ (441 ) $ 298,916 Municipal bonds and notes 2,528 2 (6 ) 2,524 U.S. government securities 5,515 3 (3 ) 5,515 U.S. government agency securities 51,463 5 (21 ) 51,447 $ 358,394 $ 479 $ (471 ) $ 358,402 Interest income from investments was $3.3 million and $7.5 million for the three months ended March 31, 2020 and 2019, respectively, and $8.9 million and $14.4 million for the six months ended March 31, 2020 and 2019, respectively. Interest income is included in other income, net on the Company's consolidated income statements. The following table summarizes investments that have been in a continuous unrealized loss position for less than 12 months and those that have been in a continuous unrealized loss position for more than 12 months as of March 31, 2020 (in thousands): Less Than 12 Months 12 Months or Greater Total March 31, 2020 Fair Value Gross Unrealized Losses Fair Value Gross Unrealized Losses Fair Value Gross Unrealized Losses Corporate bonds and notes $ 254,910 $ (3,477 ) $ 11,732 $ (140 ) $ 266,642 $ (3,617 ) Municipal bonds and notes 2,911 (9 ) — — 2,911 (9 ) U.S. government agency securities 1,498 (3 ) — — 1,498 (3 ) Total $ 259,319 $ (3,489 ) $ 11,732 $ (140 ) $ 271,051 $ (3,629 ) The following table summarizes investments that have been in a continuous unrealized loss position for less than 12 months and those that have been in a continuous unrealized loss position for more than 12 months as of September 30, 2019 (in thousands): Less Than 12 Months 12 Months or Greater Total September 30, 2019 Fair Value Gross Unrealized Losses Fair Value Gross Unrealized Losses Fair Value Gross Unrealized Losses Corporate bonds and notes $ 237,747 $ (434 ) $ 109,613 $ (104 ) $ 347,360 $ (538 ) Municipal bonds and notes 864 — 7,800 (11 ) 8,664 (11 ) U.S. government securities 27,095 (12 ) 9,991 (5 ) 37,086 (17 ) U.S. government agency securities 30,946 (22 ) — — 30,946 (22 ) Total $ 296,652 $ (468 ) $ 127,404 $ (120 ) $ 424,056 $ (588 ) The Company invests in securities that are rated investment grade. The Company reviews the individual securities in its portfolio to determine whether a decline in a security's fair value below the amortized cost basis is other-than-temporary. Gross unrealized losses were not deemed material as of March 31, 2020 and were primarily caused by global market disruptions resulting from the COVID-19 pandemic in March 2020 rather than credit risks associated with the respective issuers of the debt securities. The Company determined that as of March 31, 2020, there were no investments in its portfolio that were other-than-temporarily impaired as a result of the COVID-19 pandemic or other market conditions.

Business Combinations

Business Combinations	6 Months Ended
	Mar. 31, 2020
Business Combinations [Abstract]
Business Combinations	Business Combinations Fiscal Year 2020 Acquisition of Shape Security, Inc. On December 19, 2019 , the Company entered into a Merger Agreement (the "Merger Agreement") with Shape Security, Inc. (" Shape "), a provider of fraud and abuse prevention solutions. The transaction closed on January 24, 2020 with Shape becoming a wholly-owned subsidiary of F5. Pursuant to the Merger Agreement, at the effective time of the acquisition, the capital stock of Shape and the vested outstanding and unexercised stock options in Shape were cancelled and converted to the right to receive approximately $1.0 billion in cash, subject to certain adjustments and conditions set forth in the Merger Agreement, and the unvested stock options and restricted stock units in Shape held by continuing employees of Shape were assumed by F5, on the terms and conditions set forth in the Merger Agreement. Included in cash consideration was $23.2 million of transaction costs paid by F5 on behalf of Shape. In addition, the Company incurred $11.4 million and $15.3 million of transaction costs associated with the acquisition for the three and six months ended March 31, 2020, respectively, which was included in General and Administrative expenses. Shape is a leader in online fraud and abuse prevention, adding protection from automated attacks, botnets, and targeted fraud to F5's world-class portfolio of application services. As a result of the acquisition, the Company acquired all the assets and assumed all the liabilities of Shape . The goodwill related to the Shape acquisition is comprised primarily of expected synergies from combining operations and the acquired intangible assets that do not qualify for separate recognition. Goodwill related to the Shape acquisition is not expected to be deductible for tax purposes. The results of operations of Shape have been included in the Company's consolidated financial statements from the date of acquisition. The preliminary purchase price allocation is as follows (in thousands): Estimated Useful Life Assets acquired Cash, cash equivalents, and restricted cash $ 53,934 Fair value of tangible assets: Accounts receivable 21,077 Deferred tax assets 24,619 Operating lease right-of-use assets 29,644 Other tangible assets 22,571 Identifiable intangible assets: Developed technologies 120,000 7 years Customer relationships 21,000 4 years Trade name 9,500 5 years Goodwill 799,611 Total assets acquired $ 1,101,956 Liabilities assumed Deferred revenue $ (39,000 ) Operating lease liabilities (30,773 ) Other assumed liabilities (18,571 ) Total liabilities assumed $ (88,344 ) Net assets acquired $ 1,013,612 The initial allocation of the purchase price was based on preliminary valuations and assumptions and is subject to change within the measurement period. The Company expects to finalize the allocation of the purchase price as soon as practicable and no later than one year from the acquisition date. The developed technology intangible asset will be amortized on a straight-line basis over its estimated useful life of seven years and included in cost of net product revenues. The trade names and customer relationships intangible assets will be amortized on a straight-line basis over their estimated useful lives of five and four years , respectively, and included in sales and marketing expenses. The weighted average life of the amortizable intangible assets recognized from the Shape acquisition was 6.5 years as of January 24, 2020, the date the transaction closed. The estimated useful lives for the acquired intangible assets were based on the expected future cash flows associated with the respective asset. Since the Shape acquisition was completed on January 24, 2020, the F5 and Shape teams have been executing a plan to integrate ongoing operations. The pro forma financial information, as well as the revenue and earnings generated by Shape, were not considered material to the Company's operations. Fiscal Year 2019 Acquisition of Nginx, Inc. On March 9, 2019, the Company entered into a Merger Agreement (the "Merger Agreement") with Nginx, Inc. ("NGINX"), a provider of open source web server software and application delivery solutions. The transaction closed on May 8, 2019 with NGINX becoming a wholly-owned subsidiary of F5. Pursuant to the Merger Agreement, at the effective time of the acquisition, the capital stock of NGINX and the vested outstanding and unexercised stock options in NGINX were cancelled and converted to the right to receive approximately $643.2 million in cash, subject to certain adjustments and conditions set forth in the Merger Agreement, and the unvested stock options and restricted stock units in NGINX held by continuing employees of NGINX were assumed by F5, on the terms and conditions set forth in the Merger Agreement. Included in cash consideration was $19.0 million of transaction costs paid by F5 on behalf of NGINX. In addition, the Company incurred an additional $1.0 million of transaction costs associated with the acquisition which was included in General and Administrative expenses for fiscal 2019. NGINX is an open source leader in application delivery. The combined company will enable multi-cloud application services across all environments, providing the ease-of-use and flexibility developers require while also delivering the scale, security, reliability and enterprise readiness network operations teams demand. As a result of the acquisition, the Company acquired all the assets and assumed all the liabilities of NGINX. The goodwill related to the NGINX acquisition is comprised primarily of expected synergies from combining operations and the acquired intangible assets that do not qualify for separate recognition. The results of operations of NGINX have been included in the Company's consolidated financial statements from the date of acquisition. The preliminary purchase price allocation is as follows (in thousands): Estimated Useful Life Assets acquired Cash and cash equivalents $ 29,911 Fair value of tangible assets: Other tangible assets 23,699 Identifiable intangible assets: Developed technologies 62,500 7 years Customer relationships 12,000 15 years Trade name 14,500 7 years Non-competition agreements 300 2 years Goodwill 509,414 Total assets acquired $ 652,324 Liabilities assumed Other assumed liabilities $ (9,116 ) Total liabilities assumed $ (9,116 ) Net assets acquired $ 643,208 The measurement period for the NGINX acquisition will lapse during the third quarter of fiscal 2020. The developed technology intangible asset will be amortized on a straight-line basis over its estimated useful life of seven years and included in cost of net product revenues. The trade names and customer relationships intangible assets will be amortized on a straight-line basis over their estimated useful lives of seven years and fifteen years , respectively, and included in sales and marketing expenses. The weighted average life of the amortizable intangible assets recognized from the NGINX acquisition was 8.1 years as of May 8, 2019, the date the transaction closed. The estimated useful lives for the acquired intangible assets were based on the expected future cash flows associated with the respective asset. Tax deductible goodwill based on the Company's preliminary calculation is $450.7 million . Since the NGINX acquisition was completed on May 8, 2019, the F5 and NGINX teams have been executing a plan to integrate ongoing operations.

Balance Sheet Details

Balance Sheet Details	6 Months Ended
	Mar. 31, 2020
Balance Sheet Details [Abstract]
Balance Sheet Details	Balance Sheet Details Cash, Cash Equivalents and Restricted Cash The following table provides a reconciliation of the Company's cash and cash equivalents and restricted cash reported within the consolidated balance sheets that sum to the total cash, cash equivalents and restricted cash shown in the Company's consolidated statements of cash flows for the periods presented (in thousands): March 31, September 30, Cash and cash equivalents $ 572,888 $ 599,219 Restricted cash included in other assets, net 6,477 3,035 Total cash, cash equivalents and restricted cash $ 579,365 $ 602,254 Inventories Inventories consist of the following (in thousands): March 31, September 30, Finished goods $ 20,102 $ 22,441 Raw materials 10,840 11,960 $ 30,942 $ 34,401 Other Current Assets Other current assets consist of the following (in thousands): March 31, September 30, Contract assets $ 101,049 $ 79,407 Prepaid expenses 53,569 49,051 Capitalized contract acquisition costs 27,202 28,228 Other 36,169 26,188 $ 217,989 $ 182,874 Other Assets Other assets, net consist of the following (in thousands): March 31, September 30, Intangible assets $ 246,182 $ 108,903 Contract assets 56,335 53,085 Capitalized contract acquisition costs 37,108 31,218 Other 15,989 10,575 $ 355,614 $ 203,781 Accrued Liabilities Accrued liabilities consist of the following (in thousands): March 31, September 30, Payroll and benefits $ 141,076 $ 138,453 Operating lease liabilities, current 46,840 — Income and other tax accruals 32,007 31,801 Other 66,979 65,615 $ 286,902 $ 235,869 Other Long-term Liabilities Other long-term liabilities consist of the following (in thousands): March 31, September 30, Income taxes payable $ 41,340 $ 42,324 Deferred rent — 66,103 Other 21,411 23,426 $ 62,751 $ 131,853

Debt Facilities

Debt Facilities	6 Months Ended
	Mar. 31, 2020
Debt Disclosure [Abstract]
Debt Facilities	Debt Facilities Term Credit Agreement In connection with the acquisition of Shape, on January 24, 2020, the Company entered into a Term Credit Agreement ("Term Credit Agreement") with certain institutional lenders that provides for a senior unsecured term loan facility in an aggregate principal amount of $400.0 million (the "Term Loan Facility"). The proceeds from the Term Loan Facility were primarily used to finance the acquisition of Shape and related expenses. In connection with the Term Loan Facility, the Company incurred $2.2 million in debt issuance costs, which are recorded as a reduction to the carrying value of the principal amount of the debt. Borrowings under the Term Loan Facility bear interest at a rate equal to, at the Company's option, (a) LIBOR, adjusted for customary statutory reserves, plus an applicable margin of 1.125% to 1.75% depending on the Company's leverage ratio, or (b) an alternate base rate determined in accordance with the Term Credit Agreement, plus an applicable margin of 0.125% to 0.750% depending on the Company's leverage ratio. Interest on the outstanding principal of borrowings is currently due quarterly in arrears. As of March 31, 2020, the margin for LIBOR-based loans was 1.125% and the margin for alternate base rate loans was 0.125% . The Term Loan Facility matures on January 24, 2023 with quarterly installments (commencing with the first full fiscal quarter ended after January 24, 2020) equal to 1.25% of the original principal amount of the Term Loan Facility. The remaining outstanding principal of borrowings under the Term Loan Facility is due upon maturity on January 24, 2023. Borrowings under the Term Loan Facility may be voluntarily prepaid, in whole or in part, without penalty or premium. Borrowings repaid or prepaid under the Term Loan Facility may not be reborrowed. Among certain affirmative and negative covenants provided in the Term Credit Agreement, there is a financial covenant that requires the Company to maintain a leverage ratio, calculated as of the last day of each fiscal quarter, of consolidated total indebtedness to consolidated EBITDA. This covenant may result in a higher interest rate on its outstanding principal borrowings on the Term Loan Facility in future periods, depending on the Company's performance. As of March 31, 2020, the Company was in compliance with all covenants. As of March 31, 2020, $400.0 million of principal amount under the Term Loan Facility was outstanding, excluding unamortized debt issuance costs of $2.0 million . The weighted average interest rate on the principal amount under the Term Loan Facility outstanding balance was 2.765% for the period ending March 31, 2020. The following table presents the scheduled principal maturities as of March 31, 2020 (in thousands): Fiscal Years Ending September 30: Amount 2020 (remainder) $ 5,000 2021 20,000 2022 20,000 2023 355,000 Total $ 400,000 Revolving Credit Agreement On January 31, 2020, the Company entered into a Revolving Credit Agreement (the "Revolving Credit Agreement") that provides for a senior unsecured revolving credit facility in an aggregate principal amount of $350.0 million (the "Revolving Credit Facility"). The Company has the option to increase commitments under the Revolving Credit Facility from time to time, subject to certain conditions, by up to $150.0 million . Borrowings under the Revolving Credit Facility bear interest at a rate equal to, at the Company's option, (a) LIBOR, adjusted for customary statutory reserves, plus an applicable margin of 1.125% to 1.75% depending on the Company's leverage ratio, or (b) an alternate base rate determined in accordance with the Revolving Credit Agreement, plus an applicable margin of 0.125% to 0.750% depending on the Company's leverage ratio. The Revolving Credit Agreement also requires payment of a commitment fee calculated at a rate per annum of 0.125% to 0.300% depending on the Company's leverage ratio on the undrawn portion of the Revolving Credit Facility. Amounts incurred during the three months ended March 31, 2020 were not material. The Revolving Credit Facility matures on January 31, 2025, upon which any remaining outstanding principal of borrowings under the Revolving Credit Facility is due. The Company has the option to request up to two extensions of the maturity date in each case for an additional period of one year . Among certain affirmative and negative covenants provided in the Revolving Credit Agreement, there is a financial covenant that requires the Company to maintain a leverage ratio, calculated as of the last day of each fiscal quarter, of consolidated total indebtedness to consolidated EBITDA. As of March 31, 2020, the Company was in compliance with all covenants. As of March 31, 2020, there were no outstanding borrowings under the Revolving Credit Facility, and the Company had available borrowing capacity of $350.0 million

Leases

Leases	6 Months Ended
	Mar. 31, 2020
Leases [Abstract]
Leases	Leases During the first quarter of fiscal 2020, the Company adopted ASU 2016-02, Leases (Topic 842) (the "Leasing Standard") using the transition method provided in ASU 2018-11, Leases (Topic 842): Targeted Improvements . The impact of adopting the Leasing Standard resulted in the recognition of right-of-use assets and lease liabilities of $304.8 million and $386.4 million , respectively, on October 1, 2019, the date of adoption. The majority of the Company's operating lease payments relate to its corporate headquarters in Seattle, Washington, which includes approximately 515,000 square feet of office space. The lease commenced in April 2019 and expires in 2033 with an option for renewal. The Company has concluded that the renewal option is not yet likely to be exercised. The Company also leases additional office and lab space for product development and sales and support personnel in the United States and internationally. The Company's lease agreements do not contain any material residual value guarantees or material restrictive covenants. The components of the Company's operating lease expenses for the three and six months ended March 31, 2020 were as follows (in thousands): Three months ended Six months ended Operating lease expense $ 12,975 $ 24,293 Short-term lease expense 813 1,627 Variable lease expense 4,262 10,101 Total lease expense $ 18,050 $ 36,021 Variable lease expense primarily consists of common area maintenance and parking expenses. The Company executed two sublease contracts that commenced during the first quarter of fiscal year 2020. Lease income payments commenced in the second fiscal quarter. The Company has three additional subleases through the Q2 2020 acquisition of Shape Security. Supplemental balance sheet information related to the Company's operating leases was as follows (in thousands, except lease term and discount rate): March 31, 2020 Operating lease right-of-use assets, net $ 327,436 Operating lease liabilities, current 1 46,840 Operating lease liabilities, long-term 357,645 Total operating lease liabilities $ 404,485 Weighted average remaining lease term (in years) 10.5 Weighted average discount rate 2.60 % (1) Current portion of operating lease liabilities is included in accrued liabilities on the Company's consolidated balance sheet. Maturities of lease liabilities as of March 31, 2020 were as follows (in thousands): Fiscal Years Ending September 30: Operating Lease Payments 2020 (remainder) $ 26,897 2021 59,217 2022 56,041 2023 43,029 2024 38,334 2025 32,119 Thereafter 215,923 Total lease payments 471,560 Less: imputed interest (67,075 ) Total lease liabilities $ 404,485 Operating lease liabilities above do not include sublease income. As of March 31, 2020 , the Company expects to receive sublease income of approximately $12.5 million , which consists of $2.3 million to be received for the remainder of fiscal 2020 and $10.2 million to be received over the three fiscal years thereafter. As of March 31, 2020 , the Company had no significant operating leases that were executed but not yet commenced. ASC 840 - Leases As a result of adopting the Leasing Standard, reporting periods beginning in the first quarter of fiscal 2020 are presented under the new standard while prior period amounts are not adjusted and continue to be reported in accordance with ASC 840 - Leases. Prior to the adoption of the Leasing Standard, future minimum operating lease payments, net of sublease income, were as follows as of September 30, 2019 (in thousands): Fiscal Year Gross Lease Payments Sublease Income Net Lease Payments 2020 $ 54,046 $ 683 $ 53,363 2021 50,712 1,051 49,661 2022 47,550 1,082 46,468 2023 36,514 368 36,146 2024 33,971 — 33,971 Thereafter 242,826 — 242,826 $ 465,619 $ 3,184 $ 462,435

Commitments and Contingencies

Commitments and Contingencies	6 Months Ended
	Mar. 31, 2020
Commitments and Contingencies Disclosure [Abstract]
Commitments and Contingencies	Commitments and Contingencies Guarantees and Product Warranties In the normal course of business to facilitate sales of its products, the Company indemnifies other parties, including customers, resellers, lessors, and parties to other transactions with the Company, with respect to certain matters. The Company has agreed to hold the other party harmless against losses arising from a breach of representations or covenants, or out of intellectual property infringement or other claims made against certain parties. These agreements may limit the time within which an indemnification claim can be made and the amount of the claim. The Company has entered into indemnification agreements with its officers and directors and certain other employees, and the Company's bylaws contain similar indemnification obligations to the Company's agents. It is not possible to determine the maximum potential amount under these indemnification agreements due to the limited history of prior indemnification claims and the unique facts and circumstances involved in each particular agreement. The Company generally offers warranties of one year for hardware for those customers without service contracts, with the option of purchasing additional warranty coverage in yearly increments. The Company accrues for warranty costs as part of its cost of sales based on associated material product costs and technical support labor costs. Accrued warranty costs as of March 31, 2020 and September 30, 2019 were not material. Commitments As of March 31, 2020 , the Company's principal commitments consisted of borrowings under the Term Loan Facility and obligations outstanding under operating leases. Refer to Note 7 for the scheduled principal maturities of the Term Loan Facility as of March 31, 2020. The Company leases its facilities under operating leases that expire at various dates through 2033. There have been no material changes in the Company's lease obligations compared to those discussed in Note 11 to its annual consolidated financial statements. The Company currently has arrangements with contract manufacturers and other suppliers for the manufacturing of its products. The arrangement with the primary contract manufacturer allows them to procure component inventory on the Company's behalf based on a rolling production forecast provided by the Company. The Company is obligated to the purchase of component inventory that the contract manufacturer procures in accordance with the forecast, unless it gives notice of order cancellation in advance of applicable lead times. There have been no material changes in the Company's inventory purchase obligations compared to those discussed in Note 11 to its annual consolidated financial statements. Legal Proceedings

Income Taxes

Income Taxes	6 Months Ended
	Mar. 31, 2020
Income Tax Disclosure [Abstract]
Income Taxes	Income Taxes The Company's tax provision for interim periods is determined using an estimated annual effective tax rate, adjusted for discrete items in the related period. The effective tax rate was 26.5% and 24.3% for the three and six months ended March 31, 2020 , respectively, compared to 22.7% and 21.7% for the three and six months ended March 31, 2019 , respectively. The increase in the effective tax rate for the three and six months ended March 31, 2020 as compared to the three and six months ended March 31, 2019 is primarily due to the tax impact from stock-based compensation and other non-deductible expenses related to the acquisition of Shape Security, Inc., partially offset by a change in unrecognized tax benefits. At March 31, 2020 , the Company had $42.3 million of unrecognized tax benefits that, if recognized, would affect the effective tax rate. It is anticipated that the Company’s existing liabilities for unrecognized tax benefits will change within the next twelve months due to audit settlements or the expiration of statutes of limitations. The Company does not expect these changes to be material to the consolidated financial statements. The Company recognizes interest and, if applicable, penalties for any uncertain tax positions as a component of income tax expense.

Net Income Per Share

Net Income Per Share	6 Months Ended
	Mar. 31, 2020
Net Income 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 common shares outstanding during the period. Diluted net income per share is computed by dividing net income by the weighted average number of common and dilutive common stock equivalent shares outstanding during the period. The Company's nonvested restricted units do not have nonforfeitable rights to dividends or dividend equivalents and are not considered participating securities that should be included in the computation of earnings per share under the two-class method. The following table sets forth the computation of basic and diluted net income per share (in thousands, except per share data): Three months ended Six months ended 2020 2019 2020 2019 Numerator Net income $ 61,379 $ 116,087 $ 159,906 $ 246,992 Denominator Weighted average shares outstanding — basic 60,869 59,686 60,758 59,954 Dilutive effect of common shares from stock options and restricted stock units 215 343 259 420 Weighted average shares outstanding — diluted 61,084 60,029 61,017 60,374 Basic net income per share $ 1.01 $ 1.94 $ 2.63 $ 4.12 Diluted net income per share $ 1.00 $ 1.93 $ 2.62 $ 4.09 Anti-dilutive stock-based awards excluded from the calculations of diluted earnings per share were immaterial for the three and six months ended March 31, 2020 and 2019.

Restructuring Charges

Restructuring Charges	6 Months Ended
	Mar. 31, 2020
Restructuring Charges [Abstract]
Restructuring Charges	Restructuring Charges In December 2019, the Company initiated a restructuring plan to match strategic and financial objectives and optimize resources for long term growth, including a reduction in force program affecting approximately 75 employees. The Company recorded a restructuring charge of $7.8 million in the first quarter of fiscal 2020. The Company does not expect to record any significant future charges related to the restructuring plan. During the six months ended March 31, 2020, the following activity was recorded (in thousands): Employee Severance, Benefits and Related Costs Accrued expenses, October 1, 2019 $ — Restructuring charges 7,800 Cash payments (6,956 ) Non-cash items — Accrued expenses, March 31, 2020 $ 844

Segment Information

Segment Information	6 Months Ended
	Mar. 31, 2020
Segment Reporting [Abstract]
Segment Information	Segment Information Operating segments are defined as components of an enterprise for which separate financial information is available and evaluated regularly by the chief operating decision-maker, or decision-making group, in deciding how to allocate resources and in assessing performance. Management has determined that the Company is organized as, and operates in, one reportable operating segment: the development, marketing and sale of application services that optimize the security, performance and availability of network applications, servers and storage systems. Revenues by Geographic Location and Other Information The Company does business in three main geographic regions: the Americas (primarily the United States); Europe, the Middle East, and Africa (EMEA); and the Asia Pacific region (APAC). The Company's chief operating decision-maker reviews financial information presented on a consolidated basis accompanied by information about revenues by geographic region. The Company's foreign offices conduct sales, marketing and support activities. Revenues are attributed by geographic location based on the location of the customer. The following presents revenues by geographic region (in thousands): Three months ended Six months ended 2020 2019 2020 2019 Americas: United States $ 302,192 $ 282,037 $ 577,691 $ 546,788 Other 23,094 25,375 49,157 52,268 Total Americas 325,286 307,412 626,848 599,056 EMEA 147,985 136,549 303,937 285,533 Asia Pacific 110,178 100,934 221,969 204,076 $ 583,449 $ 544,895 $ 1,152,754 $ 1,088,665 The following distributors of the Company's products accounted for more than 10% of total net revenue: Three months ended Six months ended 2020 2019 2020 2019 Ingram Micro, Inc. 17.3 % 20.0 % 16.9 % 18.4 % Westcon Group, Inc. — — — 10.5 % Arrow ECS — 10.3 % — 10.6 % Tech Data — 10.0 % — — The Company tracks assets by physical location. Long-lived assets consist of property and equipment, net, and are shown below (in thousands): March 31, September 30, United States $ 200,035 $ 194,176 EMEA 16,244 13,451 Other countries 15,727 15,799 $ 232,006 $ 223,426

Summary of Significant Accoun_2

Summary of Significant Accounting Policies (Policies)	6 Months Ended
	Mar. 31, 2020
Accounting Policies [Abstract]
Description of Business	Description of Business F5 Networks, Inc. (the "Company") is a leading provider of multi-cloud application services which enable its customers to develop, deploy, operate, secure, and govern applications in any architecture, from on-premises to the public cloud. The Company's cloud, software, and hardware solutions enable its customers to deliver digital experiences to their customers faster, reliably, and at scale. The Company's enterprise-grade application services are available as cloud-based, software-as-a-service, and software-only solutions optimized for multi-cloud environments, with modules that can run independently, or as part of an integrated solution on its high-performance appliances. In connection with its solutions, the Company offers a broad range of professional services, including consulting, training, installation, maintenance, and other technical support services. On January 24, 2020, the Company completed the acquisition of Shape Security, Inc. ("Shape"), a leader in online fraud and abuse prevention, adding protection from automated attacks, botnets, and targeted fraud to F5's world-class portfolio of application services.
Basis of Presentation	Basis of Presentation The year-end consolidated balance sheet data was derived from audited financial statements but does not include all disclosures required by accounting principles generally accepted in the United States of America ("GAAP"). In the opinion of management, the unaudited consolidated financial statements reflect all adjustments, consisting only of normal recurring adjustments, necessary for their fair statement in conformity with accounting principles generally accepted in the United States of America. Certain information and footnote disclosures normally included in annual financial statements have been condensed or omitted in accordance with the rules and regulations of the Securities and Exchange Commission ("SEC"). The information included in this Form 10-Q should be read in conjunction with Management’s Discussion and Analysis of Financial Condition and Results of Operations and financial statements and notes thereto included in the Company’s Annual Report on Form 10-K for the fiscal year ended September 30, 2019 . Certain prior year amounts have been reclassified to conform to the current year presentation in the Consolidated Statements of Cash Flows. The reclassified amounts are considered immaterial and there was no change to total cash from operating, investing or financing activities as a result. There have been no material changes to the Company's significant accounting policies as of and for the three and six months ended March 31, 2020 , except for the accounting policy for leases that was updated as a result of adopting Accounting Standards Update 2016-02, Leases (Topic 842) (ASU 2016-02) and related standards. For more information, refer to the "Recently Adopted Accounting Standards" section of Note 1 and Note 8 - Leases.
Recent Accounting Pronouncements	Recently Adopted Accounting Standards In February 2016, the Financial Accounting Standards Board ("FASB") issued ASU 2016-02, Leases (Topic 842) (ASU 2016-02), which requires lessees to recognize on the balance sheet a right-of-use asset, representing its right to use the underlying asset for the lease term, and a corresponding lease liability for all leases with terms greater than twelve months. The Company's leases consist primarily of operating leases for its offices and lab spaces. The Company does not have finance leases. The guidance also requires qualitative and quantitative disclosures designed to assess the amount, timing and uncertainty of cash flows arising from leases. The Company adopted this standard on October 1, 2019 on a modified retrospective basis by applying the new standard to its lease portfolio as of October 1, 2019, while continuing to apply legacy guidance in the comparative periods. The adoption of this standard had no impact on the consolidated income statements and consolidated statements of cash flows. Refer to Note 8 - Leases for further discussion. Upon adoption of the standard, the Company elected the package of three expedients for existing and expired contracts to not reassess: the existence of additional leases, lease classification, or the treatment of initial direct costs. The Company also applies the short-term lease exemption for leases with an original expected term of 12 months or less and expenses such leases month-to-month and does not record a right-of-use asset or lease liability. Short-term lease activity under the exception is not significant. Additionally, the Company does not separate lease and non-lease components in the allocation of minimum lease payments for its office space and equipment leases, as such separation is not significant. The Company includes in minimum lease payments, fixed and variable payments based on a rate or index, but excludes variable payments based on satisfying future benchmarks or actual future costs incurred; such amounts are expensed as incurred. To calculate the net present value, the Company applied an incremental borrowing rate. This incremental borrowing rate is determined using a portfolio approach based on the rate of interest the Company would pay to borrow an amount equal to the lease payments on a collateralized basis over a similar term . Renewal options to extend lease terms are excluded from the minimum lease term at lease commencement. Recently Issued Accounting Pronouncements In June 2016, the FASB issued ASU 2016-13, Financial Instruments - Credit Losses (Topic 326): Measurement of Credit Losses on Financial Instruments (ASU 2016-13), which replaces the incurred loss impairment methodology in current GAAP with a methodology that reflects expected credit losses. The new standard is effective for fiscal years, and interim periods within those fiscal years, beginning after December 15, 2019. Early adoption is permitted. The Company does not anticipate that the adoption of this standard will have a material impact on its consolidated financial statements. In August 2018, the FASB issued ASU 2018-15, Intangibles - Goodwill and Other - Internal-Use Software (Subtopic 350-40) (ASU 2018-15), which aligns the requirements for capitalizing implementation costs incurred in a hosting arrangement that is a service contract with the requirements for capitalizing implementation costs incurred to develop or obtain internal-use software, and hosting arrangements that include an internal use software license. The accounting for the service element of a hosting arrangement that is a service contract is not affected by the amendments in this update. The new standard is effective for fiscal years, and interim periods within those fiscal years, beginning after December 15, 2019. Early adoption is permitted. The Company does not anticipate that the adoption of this standard will have a material impact on its consolidated financial statements.

Revenue from Contracts with C_2

Revenue from Contracts with Customers (Tables)	6 Months Ended
	Mar. 31, 2020
Revenue from Contract with Customer [Abstract]
Capitalized Contract Cost	The table below shows significant movements in capitalized contract acquisition costs (current and noncurrent) for the six months ended March 31, 2020 (in thousands): Balance, September 30, 2019 $ 59,446 Additional capitalized contract acquisition costs deferred 21,836 Amortization of capitalized contract acquisition costs (16,972 ) Balance, March 31, 2020 $ 64,310
Contract with Customer, Asset and Liability	The table below shows significant movements in contract assets (current and noncurrent) for the six months ended March 31, 2020 (in thousands): Balance, September 30, 2019 $ 132,492 Revenue recognized during period but not yet billed 13,998 Contract asset additions 38,060 Contract assets acquired through the purchase of Shape 6,045 Contract assets reclassified to accounts receivable (33,211 ) Balance, March 31, 2020 $ 157,384 The table below shows significant movements in the deferred revenue balances (current and noncurrent) for the six months ended March 31, 2020 (in thousands): Balance, September 30, 2019 $ 1,198,116 Amounts billed but not recognized as revenues 587,983 Amounts acquired through the purchase of Shape 39,000 Revenues recognized related to the opening balance of deferred revenue (543,995 ) Balance, March 31, 2020 $ 1,281,104

Fair Value Measurements (Tables

Fair Value Measurements (Tables)	6 Months Ended
	Mar. 31, 2020
Fair Value Disclosures [Abstract]
Schedule of Financial Assets Measured at Fair Value on a Recurring Basis	The Company's financial assets measured at fair value on a recurring basis subject to the disclosure requirements at March 31, 2020 , were as follows (in thousands): Fair Value Measurements at Reporting Date Using Quoted Prices in Active Markets for Identical Securities (Level 1) Significant Other Observable Inputs (Level 2) Significant Unobservable Inputs (Level 3) Fair Value at Cash equivalents $ 100,355 $ — $ — $ 100,355 Short-term investments Available-for-sale securities — certificates of deposits — 493 — 493 Available-for-sale securities — corporate bonds and notes — 201,811 — 201,811 Available-for-sale securities — municipal bonds and notes — 8,057 — 8,057 Available-for-sale securities — U.S. government securities — 27,232 — 27,232 Available-for-sale securities — U.S. government agency securities — 10,664 — 10,664 Long-term investments Available-for-sale securities — corporate bonds and notes — 180,625 — 180,625 Available-for-sale securities — U.S. government agency securities — 24,344 — 24,344 Total $ 100,355 $ 453,226 $ — $ 553,581 The Company's financial assets measured at fair value on a recurring basis subject to the disclosure requirements at September 30, 2019 , were as follows (in thousands): Fair Value Measurements at Reporting Date Using Quoted Prices in Active Markets for Identical Securities (Level 1) Significant Other Observable Inputs (Level 2) Significant Unobservable Inputs (Level 3) Fair Value at September 30, 2019 Cash equivalents $ 140,238 $ 153,404 $ — $ 293,642 Short-term investments Available-for-sale securities — certificates of deposits — 249 — 249 Available-for-sale securities — corporate bonds and notes — 259,547 — 259,547 Available-for-sale securities — municipal bonds and notes — 12,129 — 12,129 Available-for-sale securities — U.S. government securities — 78,992 — 78,992 Available-for-sale securities — U.S. government agency securities — 22,146 — 22,146 Long-term investments Available-for-sale securities — corporate bonds and notes — 298,916 — 298,916 Available-for-sale securities — municipal bonds and notes — 2,524 — 2,524 Available-for-sale securities — U.S. government securities — 5,515 — 5,515 Available-for-sale securities — U.S. government agency securities — 51,447 — 51,447 Total $ 140,238 $ 884,869 $ — $ 1,025,107

Short-Term and Long-Term Inve_2

Short-Term and Long-Term Investments (Tables)	6 Months Ended
	Mar. 31, 2020
Investments, Debt and Equity Securities [Abstract]
Schedule of Short-Term and Long-Term Investments	Short-term investments consist of the following (in thousands): March 31, 2020 Cost or Cost Gross Gains Gross Losses Fair Value Certificates of deposits $ 493 $ — $ — $ 493 Corporate bonds and notes 202,270 259 (718 ) 201,811 Municipal bonds and notes 8,056 10 (9 ) 8,057 U.S. government securities 27,007 225 — 27,232 U.S. government agency securities 10,627 37 — 10,664 $ 248,453 $ 531 $ (727 ) $ 248,257 September 30, 2019 Cost or Cost Gross Gains Gross Losses Fair Value Certificates of deposits $ 249 $ — $ — $ 249 Corporate bonds and notes 259,242 402 (97 ) 259,547 Municipal bonds and notes 12,128 6 (5 ) 12,129 U.S. government securities 78,988 18 (14 ) 78,992 U.S. government agency securities 22,138 9 (1 ) 22,146 $ 372,745 $ 435 $ (117 ) $ 373,063 Long-term investments consist of the following (in thousands): March 31, 2020 Cost or Cost Gross Gains Gross Losses Fair Value Corporate bonds and notes $ 183,265 $ 259 $ (2,899 ) $ 180,625 U.S. government agency securities 24,276 71 (3 ) 24,344 $ 207,541 $ 330 $ (2,902 ) $ 204,969 September 30, 2019 Cost or Cost Gross Gains Gross Losses Fair Value Corporate bonds and notes $ 298,888 $ 469 $ (441 ) $ 298,916 Municipal bonds and notes 2,528 2 (6 ) 2,524 U.S. government securities 5,515 3 (3 ) 5,515 U.S. government agency securities 51,463 5 (21 ) 51,447 $ 358,394 $ 479 $ (471 ) $ 358,402
Schedule of Investments That Have Been in a Continuous Unrealized Loss Position	The following table summarizes investments that have been in a continuous unrealized loss position for less than 12 months and those that have been in a continuous unrealized loss position for more than 12 months as of March 31, 2020 (in thousands): Less Than 12 Months 12 Months or Greater Total March 31, 2020 Fair Value Gross Unrealized Losses Fair Value Gross Unrealized Losses Fair Value Gross Unrealized Losses Corporate bonds and notes $ 254,910 $ (3,477 ) $ 11,732 $ (140 ) $ 266,642 $ (3,617 ) Municipal bonds and notes 2,911 (9 ) — — 2,911 (9 ) U.S. government agency securities 1,498 (3 ) — — 1,498 (3 ) Total $ 259,319 $ (3,489 ) $ 11,732 $ (140 ) $ 271,051 $ (3,629 ) The following table summarizes investments that have been in a continuous unrealized loss position for less than 12 months and those that have been in a continuous unrealized loss position for more than 12 months as of September 30, 2019 (in thousands): Less Than 12 Months 12 Months or Greater Total September 30, 2019 Fair Value Gross Unrealized Losses Fair Value Gross Unrealized Losses Fair Value Gross Unrealized Losses Corporate bonds and notes $ 237,747 $ (434 ) $ 109,613 $ (104 ) $ 347,360 $ (538 ) Municipal bonds and notes 864 — 7,800 (11 ) 8,664 (11 ) U.S. government securities 27,095 (12 ) 9,991 (5 ) 37,086 (17 ) U.S. government agency securities 30,946 (22 ) — — 30,946 (22 ) Total $ 296,652 $ (468 ) $ 127,404 $ (120 ) $ 424,056 $ (588 )

Business Combinations (Tables)

Business Combinations (Tables)	6 Months Ended
	Mar. 31, 2020
Business Combinations [Abstract]
Schedule of Recognized Identified Assets Acquired and Liabilities Assumed	The preliminary purchase price allocation is as follows (in thousands): Estimated Useful Life Assets acquired Cash, cash equivalents, and restricted cash $ 53,934 Fair value of tangible assets: Accounts receivable 21,077 Deferred tax assets 24,619 Operating lease right-of-use assets 29,644 Other tangible assets 22,571 Identifiable intangible assets: Developed technologies 120,000 7 years Customer relationships 21,000 4 years Trade name 9,500 5 years Goodwill 799,611 Total assets acquired $ 1,101,956 Liabilities assumed Deferred revenue $ (39,000 ) Operating lease liabilities (30,773 ) Other assumed liabilities (18,571 ) Total liabilities assumed $ (88,344 ) Net assets acquired $ 1,013,612 The preliminary purchase price allocation is as follows (in thousands): Estimated Useful Life Assets acquired Cash and cash equivalents $ 29,911 Fair value of tangible assets: Other tangible assets 23,699 Identifiable intangible assets: Developed technologies 62,500 7 years Customer relationships 12,000 15 years Trade name 14,500 7 years Non-competition agreements 300 2 years Goodwill 509,414 Total assets acquired $ 652,324 Liabilities assumed Other assumed liabilities $ (9,116 ) Total liabilities assumed $ (9,116 ) Net assets acquired $ 643,208

Balance Sheet Details (Tables)

Balance Sheet Details (Tables)	6 Months Ended
	Mar. 31, 2020
Balance Sheet Details [Abstract]
Cash and Cash Equivalents	The following table provides a reconciliation of the Company's cash and cash equivalents and restricted cash reported within the consolidated balance sheets that sum to the total cash, cash equivalents and restricted cash shown in the Company's consolidated statements of cash flows for the periods presented (in thousands): March 31, September 30, Cash and cash equivalents $ 572,888 $ 599,219 Restricted cash included in other assets, net 6,477 3,035 Total cash, cash equivalents and restricted cash $ 579,365 $ 602,254
Inventories	Inventories consist of the following (in thousands): March 31, September 30, Finished goods $ 20,102 $ 22,441 Raw materials 10,840 11,960 $ 30,942 $ 34,401
Other Current Assets	Other current assets consist of the following (in thousands): March 31, September 30, Contract assets $ 101,049 $ 79,407 Prepaid expenses 53,569 49,051 Capitalized contract acquisition costs 27,202 28,228 Other 36,169 26,188 $ 217,989 $ 182,874
Other Assets, Noncurrent	Other assets, net consist of the following (in thousands): March 31, September 30, Intangible assets $ 246,182 $ 108,903 Contract assets 56,335 53,085 Capitalized contract acquisition costs 37,108 31,218 Other 15,989 10,575 $ 355,614 $ 203,781
Accrued Liabilities	Accrued liabilities consist of the following (in thousands): March 31, September 30, Payroll and benefits $ 141,076 $ 138,453 Operating lease liabilities, current 46,840 — Income and other tax accruals 32,007 31,801 Other 66,979 65,615 $ 286,902 $ 235,869
Noncurrent Liabilities	Other long-term liabilities consist of the following (in thousands): March 31, September 30, Income taxes payable $ 41,340 $ 42,324 Deferred rent — 66,103 Other 21,411 23,426 $ 62,751 $ 131,853

Debt Facilities (Tables)

Debt Facilities (Tables)	6 Months Ended
	Mar. 31, 2020
Debt Disclosure [Abstract]
Schedule of Maturities of Long-term Debt	The following table presents the scheduled principal maturities as of March 31, 2020 (in thousands): Fiscal Years Ending September 30: Amount 2020 (remainder) $ 5,000 2021 20,000 2022 20,000 2023 355,000 Total $ 400,000

Leases (Tables)

Leases (Tables)	6 Months Ended
	Mar. 31, 2020
Leases [Abstract]
Lease, Cost	The components of the Company's operating lease expenses for the three and six months ended March 31, 2020 were as follows (in thousands): Three months ended Six months ended Operating lease expense $ 12,975 $ 24,293 Short-term lease expense 813 1,627 Variable lease expense 4,262 10,101 Total lease expense $ 18,050 $ 36,021
Assets And Liabilities Lessee	Supplemental balance sheet information related to the Company's operating leases was as follows (in thousands, except lease term and discount rate): March 31, 2020 Operating lease right-of-use assets, net $ 327,436 Operating lease liabilities, current 1 46,840 Operating lease liabilities, long-term 357,645 Total operating lease liabilities $ 404,485 Weighted average remaining lease term (in years) 10.5 Weighted average discount rate 2.60 % (1) Current portion of operating lease liabilities is included in accrued liabilities on the Company's consolidated balance sheet.
Lessee, Operating Lease, Liability, Maturity	Maturities of lease liabilities as of March 31, 2020 were as follows (in thousands): Fiscal Years Ending September 30: Operating Lease Payments 2020 (remainder) $ 26,897 2021 59,217 2022 56,041 2023 43,029 2024 38,334 2025 32,119 Thereafter 215,923 Total lease payments 471,560 Less: imputed interest (67,075 ) Total lease liabilities $ 404,485
Future Minimum Rental Payments for Operating Leases	Prior to the adoption of the Leasing Standard, future minimum operating lease payments, net of sublease income, were as follows as of September 30, 2019 (in thousands): Fiscal Year Gross Lease Payments Sublease Income Net Lease Payments 2020 $ 54,046 $ 683 $ 53,363 2021 50,712 1,051 49,661 2022 47,550 1,082 46,468 2023 36,514 368 36,146 2024 33,971 — 33,971 Thereafter 242,826 — 242,826 $ 465,619 $ 3,184 $ 462,435

Net Income Per Share (Tables)

Net Income Per Share (Tables)	6 Months Ended
	Mar. 31, 2020
Net Income Per Share [Abstract]
Schedule of Earnings Per Share, Basic and Diluted	The following table sets forth the computation of basic and diluted net income per share (in thousands, except per share data): Three months ended Six months ended 2020 2019 2020 2019 Numerator Net income $ 61,379 $ 116,087 $ 159,906 $ 246,992 Denominator Weighted average shares outstanding — basic 60,869 59,686 60,758 59,954 Dilutive effect of common shares from stock options and restricted stock units 215 343 259 420 Weighted average shares outstanding — diluted 61,084 60,029 61,017 60,374 Basic net income per share $ 1.01 $ 1.94 $ 2.63 $ 4.12 Diluted net income per share $ 1.00 $ 1.93 $ 2.62 $ 4.09

Restructuring Charges (Tables)

Restructuring Charges (Tables)	6 Months Ended
	Mar. 31, 2020
Restructuring Charges [Abstract]
Restructuring and Related Costs	During the six months ended March 31, 2020, the following activity was recorded (in thousands): Employee Severance, Benefits and Related Costs Accrued expenses, October 1, 2019 $ — Restructuring charges 7,800 Cash payments (6,956 ) Non-cash items — Accrued expenses, March 31, 2020 $ 844

Segment Information (Tables)

Segment Information (Tables)	6 Months Ended
	Mar. 31, 2020
Segment Reporting [Abstract]
Schedule of Revenues by Geographic Region	The following presents revenues by geographic region (in thousands): Three months ended Six months ended 2020 2019 2020 2019 Americas: United States $ 302,192 $ 282,037 $ 577,691 $ 546,788 Other 23,094 25,375 49,157 52,268 Total Americas 325,286 307,412 626,848 599,056 EMEA 147,985 136,549 303,937 285,533 Asia Pacific 110,178 100,934 221,969 204,076 $ 583,449 $ 544,895 $ 1,152,754 $ 1,088,665
Schedule of Revenue by Major Customers by Reporting Segments	The following distributors of the Company's products accounted for more than 10% of total net revenue: Three months ended Six months ended 2020 2019 2020 2019 Ingram Micro, Inc. 17.3 % 20.0 % 16.9 % 18.4 % Westcon Group, Inc. — — — 10.5 % Arrow ECS — 10.3 % — 10.6 % Tech Data — 10.0 % — —
Long-lived Assets by Geographic Areas	The Company tracks assets by physical location. Long-lived assets consist of property and equipment, net, and are shown below (in thousands): March 31, September 30, United States $ 200,035 $ 194,176 EMEA 16,244 13,451 Other countries 15,727 15,799 $ 232,006 $ 223,426

Revenue from Contracts with C_3

Revenue from Contracts with Customers - Capitalized contract acquisition costs (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Mar. 31, 2020	Mar. 31, 2019	Mar. 31, 2020	Mar. 31, 2019
Changes In Capitalized Contract Cost [Roll Forward]
Beginning Balance			$ 59,446
Additional capitalized contract acquisition costs deferred			21,836
Amortization of capitalized contract acquisition costs	$ (8,300)	$ (7,200)	(16,972)	$ (14,400)
Ending Balance	$ 64,310		$ 64,310

Revenue from Contracts with C_4

Revenue from Contracts with Customers - Narrative (Details) - USD ($)	3 Months Ended		6 Months Ended
	Mar. 31, 2020	Mar. 31, 2019	Mar. 31, 2020	Mar. 31, 2019
Revenue from Contract with Customer [Abstract]
Amortization of capitalized contract acquisition costs	$ 8,300,000	$ 7,200,000	$ 16,972,000	$ 14,400,000
Capitalized Contract Cost, Impairment Loss	$ 0	$ 0	$ 0	$ 0

Revenue from Contracts with C_5

Revenue from Contracts with Customers - Contract Assets and Liabilities (Details) $ in Thousands	6 Months Ended
	Mar. 31, 2020USD ($)
Change in Contract with Customer, Asset [Roll Forward]
Beginning Balance	$ 132,492
Revenue recognized during period but not yet billed	13,998
Contract asset additions	38,060
Contract assets acquired through the purchase of Shape	6,045
Contract assets reclassified to accounts receivable	(33,211)
Ending Balance	157,384
Change in Contract with Customer, Liability [Roll Forward]
Beginning Balance	1,198,116
Amounts billed but not recognized as revenues	587,983
Amounts acquired through the purchase of Shape	39,000
Revenues recognized related to the opening balance of deferred revenue	(543,995)
Ending Balance	$ 1,281,104

Revenue from Contracts with C_6

Revenue from Contracts with Customers - Remaining Performance Obligations (Details) $ in Billions	Mar. 31, 2020USD ($)
Revenue from Contract with Customer [Abstract]
Revenue, remaining performance obligation, amount	$ 1.3
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2020-04-01
Revenue from Contract with Customer [Abstract]
Revenue, remaining performance obligation, percentage	69.40%
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Revenue, remaining performance obligation, expected timing of satisfaction, period	12 months
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2021-04-01
Revenue from Contract with Customer [Abstract]
Revenue, remaining performance obligation, percentage	18.60%
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Revenue, remaining performance obligation, expected timing of satisfaction, period	12 months

Fair Value Measurements - Sched

Fair Value Measurements - Schedule of Financial Assets Measured at Fair Value on a Recurring Basis (Details) - Fair Value, Recurring - USD ($) $ in Thousands	Mar. 31, 2020	Sep. 30, 2019
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis, Valuation Techniques [Line Items]
Cash equivalents, fair value	$ 100,355	$ 293,642
Investments, fair value	553,581	1,025,107
Certificates of Deposit
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis, Valuation Techniques [Line Items]
Debt Securities, Available-for-sale, Current	493	249
Corporate Bonds and Notes
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis, Valuation Techniques [Line Items]
Debt Securities, Available-for-sale, Current	201,811	259,547
Debt Securities, Available-for-sale, Noncurrent	180,625	298,916
Municipal Bonds and Notes
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis, Valuation Techniques [Line Items]
Debt Securities, Available-for-sale, Current	8,057	12,129
Debt Securities, Available-for-sale, Noncurrent		2,524
U.S. Government Securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis, Valuation Techniques [Line Items]
Debt Securities, Available-for-sale, Current	27,232	78,992
Debt Securities, Available-for-sale, Noncurrent		5,515
U.S. Government Agency Securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis, Valuation Techniques [Line Items]
Debt Securities, Available-for-sale, Current	10,664	22,146
Debt Securities, Available-for-sale, Noncurrent	24,344	51,447
Level 1
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis, Valuation Techniques [Line Items]
Cash equivalents, fair value	100,355	140,238
Investments, fair value	100,355	140,238
Level 1 | Certificates of Deposit
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis, Valuation Techniques [Line Items]
Debt Securities, Available-for-sale, Current	0	0
Level 1 | Corporate Bonds and Notes
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis, Valuation Techniques [Line Items]
Debt Securities, Available-for-sale, Current	0	0
Debt Securities, Available-for-sale, Noncurrent	0	0
Level 1 | Municipal Bonds and Notes
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis, Valuation Techniques [Line Items]
Debt Securities, Available-for-sale, Current	0	0
Debt Securities, Available-for-sale, Noncurrent		0
Level 1 | U.S. Government Securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis, Valuation Techniques [Line Items]
Debt Securities, Available-for-sale, Current	0	0
Debt Securities, Available-for-sale, Noncurrent		0
Level 1 | U.S. Government Agency Securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis, Valuation Techniques [Line Items]
Debt Securities, Available-for-sale, Current	0	0
Debt Securities, Available-for-sale, Noncurrent	0	0
Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis, Valuation Techniques [Line Items]
Cash equivalents, fair value	0	153,404
Investments, fair value	453,226	884,869
Level 2 | Certificates of Deposit
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis, Valuation Techniques [Line Items]
Debt Securities, Available-for-sale, Current	493	249
Level 2 | Corporate Bonds and Notes
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis, Valuation Techniques [Line Items]
Debt Securities, Available-for-sale, Current	201,811	259,547
Debt Securities, Available-for-sale, Noncurrent	180,625	298,916
Level 2 | Municipal Bonds and Notes
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis, Valuation Techniques [Line Items]
Debt Securities, Available-for-sale, Current	8,057	12,129
Debt Securities, Available-for-sale, Noncurrent		2,524
Level 2 | U.S. Government Securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis, Valuation Techniques [Line Items]
Debt Securities, Available-for-sale, Current	27,232	78,992
Debt Securities, Available-for-sale, Noncurrent		5,515
Level 2 | U.S. Government Agency Securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis, Valuation Techniques [Line Items]
Debt Securities, Available-for-sale, Current	10,664	22,146
Debt Securities, Available-for-sale, Noncurrent	24,344	51,447
Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis, Valuation Techniques [Line Items]
Cash equivalents, fair value	0	0
Investments, fair value	0	0
Level 3 | Certificates of Deposit
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis, Valuation Techniques [Line Items]
Debt Securities, Available-for-sale, Current	0	0
Level 3 | Corporate Bonds and Notes
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis, Valuation Techniques [Line Items]
Debt Securities, Available-for-sale, Current	0	0
Debt Securities, Available-for-sale, Noncurrent	0	0
Level 3 | Municipal Bonds and Notes
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis, Valuation Techniques [Line Items]
Debt Securities, Available-for-sale, Current	0	0
Debt Securities, Available-for-sale, Noncurrent		0
Level 3 | U.S. Government Securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis, Valuation Techniques [Line Items]
Debt Securities, Available-for-sale, Current	0	0
Debt Securities, Available-for-sale, Noncurrent		0
Level 3 | U.S. Government Agency Securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis, Valuation Techniques [Line Items]
Debt Securities, Available-for-sale, Current	0	0
Debt Securities, Available-for-sale, Noncurrent	$ 0	$ 0

Short-Term and Long-Term Inve_3

Short-Term and Long-Term Investments - Schedule of Short-Term and Long-Term Investments (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Mar. 31, 2020	Mar. 31, 2019	Mar. 31, 2020	Mar. 31, 2019	Sep. 30, 2019
Schedule of Investments [Line Items]
Interest income from investments	$ 3,300	$ 7,500	$ 8,900	$ 14,400
Short-Term Investments
Schedule of Investments [Line Items]
Cost or amortized cost	248,453		248,453		$ 372,745
Gross unrealized gains	531		531		435
Gross unrealized losses	(727)		(727)		(117)
Fair value	248,257		248,257		373,063
Short-Term Investments | Certificates of Deposit
Schedule of Investments [Line Items]
Cost or amortized cost	493		493		249
Gross unrealized gains	0		0		0
Gross unrealized losses	0		0		0
Fair value	493		493		249
Short-Term Investments | Corporate Bonds and Notes
Schedule of Investments [Line Items]
Cost or amortized cost	202,270		202,270		259,242
Gross unrealized gains	259		259		402
Gross unrealized losses	(718)		(718)		(97)
Fair value	201,811		201,811		259,547
Short-Term Investments | Municipal Bonds and Notes
Schedule of Investments [Line Items]
Cost or amortized cost	8,056		8,056		12,128
Gross unrealized gains	10		10		6
Gross unrealized losses	(9)		(9)		(5)
Fair value	8,057		8,057		12,129
Short-Term Investments | U.S. Government Securities
Schedule of Investments [Line Items]
Cost or amortized cost	27,007		27,007		78,988
Gross unrealized gains	225		225		18
Gross unrealized losses	0		0		(14)
Fair value	27,232		27,232		78,992
Short-Term Investments | U.S. Government Agency Securities
Schedule of Investments [Line Items]
Cost or amortized cost	10,627		10,627		22,138
Gross unrealized gains	37		37		9
Gross unrealized losses	0		0		(1)
Fair value	10,664		10,664		22,146
Long-Term Investments
Schedule of Investments [Line Items]
Cost or amortized cost	207,541		207,541		358,394
Gross unrealized gains	330		330		479
Gross unrealized losses	(2,902)		(2,902)		(471)
Fair value	204,969		204,969		358,402
Long-Term Investments | Corporate Bonds and Notes
Schedule of Investments [Line Items]
Cost or amortized cost	183,265		183,265		298,888
Gross unrealized gains	259		259		469
Gross unrealized losses	(2,899)		(2,899)		(441)
Fair value	180,625		180,625		298,916
Long-Term Investments | Municipal Bonds and Notes
Schedule of Investments [Line Items]
Cost or amortized cost					2,528
Gross unrealized gains					2
Gross unrealized losses					(6)
Fair value					2,524
Long-Term Investments | U.S. Government Securities
Schedule of Investments [Line Items]
Cost or amortized cost					5,515
Gross unrealized gains					3
Gross unrealized losses					(3)
Fair value					5,515
Long-Term Investments | U.S. Government Agency Securities
Schedule of Investments [Line Items]
Cost or amortized cost	24,276		24,276		51,463
Gross unrealized gains	71		71		5
Gross unrealized losses	(3)		(3)		(21)
Fair value	$ 24,344		$ 24,344		$ 51,447

Short-Term and Long-Term Inve_4

Short-Term and Long-Term Investments - Schedule of Investments That Have Been in a Continuous Unrealized Loss Position (Details) - USD ($) $ in Thousands	Mar. 31, 2020	Sep. 30, 2019
Fair Value
Less than 12 months	$ 259,319	$ 296,652
12 months or greater	11,732	127,404
Total	271,051	424,056
Gross Unrealized Losses
Less than 12 months	(3,489)	(468)
12 months or greater	(140)	(120)
Total	(3,629)	(588)
Corporate Bonds and Notes
Fair Value
Less than 12 months	254,910	237,747
12 months or greater	11,732	109,613
Total	266,642	347,360
Gross Unrealized Losses
Less than 12 months	(3,477)	(434)
12 months or greater	(140)	(104)
Total	(3,617)	(538)
Municipal Bonds and Notes
Fair Value
Less than 12 months	2,911	864
12 months or greater	0	7,800
Total	2,911	8,664
Gross Unrealized Losses
Less than 12 months	(9)	0
12 months or greater	0	(11)
Total	(9)	(11)
U.S. Government Securities
Fair Value
Less than 12 months		27,095
12 months or greater		9,991
Total		37,086
Gross Unrealized Losses
Less than 12 months		(12)
12 months or greater		(5)
Total		(17)
U.S. Government Agency Securities
Fair Value
Less than 12 months	1,498	30,946
12 months or greater	0	0
Total	1,498	30,946
Gross Unrealized Losses
Less than 12 months	(3)	(22)
12 months or greater	0	0
Total	$ (3)	$ (22)

Business Combinations - Narrati

Business Combinations - Narrative (Details) - USD ($) $ in Millions	Jan. 24, 2020	May 08, 2019	Mar. 31, 2020	Mar. 31, 2020
Shape Security, Inc.
Business Acquisition [Line Items]
Total purchase price	$ 1,000
Transaction costs	$ 23.2
Identifiable intangible assets useful life	6 years 6 months
Shape Security, Inc. | General and Administrative Expense
Business Acquisition [Line Items]
Business combination, acquisition related costs			$ 11.4	$ 15.3
F5 Networks Acquisition of Nginx
Business Acquisition [Line Items]
Total purchase price		$ 643.2
Transaction costs		$ 19
Identifiable intangible assets useful life		8 years 1 month 6 days
Tax deductible goodwill		$ 450.7
F5 Networks Acquisition of Nginx | General and Administrative Expense
Business Acquisition [Line Items]
Transaction costs		$ 1
Developed Technology Rights | Shape Security, Inc.
Business Acquisition [Line Items]
Identifiable intangible assets useful life	7 years
Developed Technology Rights | F5 Networks Acquisition of Nginx
Business Acquisition [Line Items]
Identifiable intangible assets useful life		7 years
Trade Names | Shape Security, Inc.
Business Acquisition [Line Items]
Identifiable intangible assets useful life	5 years
Trade Names | F5 Networks Acquisition of Nginx
Business Acquisition [Line Items]
Identifiable intangible assets useful life		7 years
Customer Relationships | Shape Security, Inc.
Business Acquisition [Line Items]
Identifiable intangible assets useful life	4 years
Customer Relationships | F5 Networks Acquisition of Nginx
Business Acquisition [Line Items]
Identifiable intangible assets useful life		15 years

Business Combinations - Purchas

Business Combinations - Purchase Price Allocation (Details) - USD ($) $ in Thousands	Jan. 24, 2020	May 08, 2019	Mar. 31, 2020	Sep. 30, 2019
Fair value of tangible assets:
Goodwill			$ 1,864,991	$ 1,065,379
Shape Security, Inc.
Assets acquired
Cash and cash equivalents	$ 53,934
Fair value of tangible assets:
Accounts receivable	21,077
Deferred tax assets	24,619
Operating lease right-of-use assets	29,644
Other tangible assets	$ 22,571
Identifiable intangible assets useful life	6 years 6 months
Goodwill	$ 799,611
Total assets acquired	1,101,956
Liabilities assumed
Deferred revenue	(39,000)
Operating lease liabilities	(30,773)
Other assumed liabilities	(18,571)
Total liabilities assumed	(88,344)
Net assets acquired	1,013,612
Shape Security, Inc. | Developed Technology Rights
Fair value of tangible assets:
Identifiable intangible assets:	$ 120,000
Identifiable intangible assets useful life	7 years
Shape Security, Inc. | Customer Relationships
Fair value of tangible assets:
Identifiable intangible assets:	$ 21,000
Identifiable intangible assets useful life	4 years
Shape Security, Inc. | Trade Names
Fair value of tangible assets:
Identifiable intangible assets:	$ 9,500
Identifiable intangible assets useful life	5 years
F5 Networks Acquisition of Nginx
Assets acquired
Cash and cash equivalents		$ 29,911
Fair value of tangible assets:
Other tangible assets		$ 23,699
Identifiable intangible assets useful life		8 years 1 month 6 days
Goodwill		$ 509,414
Total assets acquired		652,324
Liabilities assumed
Other assumed liabilities		(9,116)
Total liabilities assumed		(9,116)
Net assets acquired		643,208
F5 Networks Acquisition of Nginx | Developed Technology Rights
Fair value of tangible assets:
Identifiable intangible assets:		$ 62,500
Identifiable intangible assets useful life		7 years
F5 Networks Acquisition of Nginx | Customer Relationships
Fair value of tangible assets:
Identifiable intangible assets:		$ 12,000
Identifiable intangible assets useful life		15 years
F5 Networks Acquisition of Nginx | Trade Names
Fair value of tangible assets:
Identifiable intangible assets:		$ 14,500
Identifiable intangible assets useful life		7 years
F5 Networks Acquisition of Nginx | Non-competition Agreements
Fair value of tangible assets:
Identifiable intangible assets:		$ 300
Identifiable intangible assets useful life		2 years

Balance Sheet Details - Cash an

Balance Sheet Details - Cash and Cash Equivalent (Details) - USD ($) $ in Thousands	Mar. 31, 2020	Sep. 30, 2019	Mar. 31, 2019	Sep. 30, 2018
Balance Sheet Details [Abstract]
Cash and cash equivalents	$ 572,888	$ 599,219
Restricted cash included in other assets, net	6,477	3,035
Total cash, cash equivalents and restricted cash	$ 579,365	$ 602,254	$ 727,850	$ 425,894

Balance Sheet Details - Invento

Balance Sheet Details - Inventories (Details) - USD ($) $ in Thousands	Mar. 31, 2020	Sep. 30, 2019
Balance Sheet Details [Abstract]
Finished goods	$ 20,102	$ 22,441
Raw materials	10,840	11,960
Inventories	$ 30,942	$ 34,401

Balance Sheet Details - Other C

Balance Sheet Details - Other Current Assets (Details) - USD ($) $ in Thousands	Mar. 31, 2020	Sep. 30, 2019
Balance Sheet Details [Abstract]
Contract assets	$ 101,049	$ 79,407
Prepaid expenses	53,569	49,051
Capitalized contract acquisition costs	27,202	28,228
Other	36,169	26,188
Other Assets, Current	$ 217,989	$ 182,874

Balance Sheet Details - Other A

Balance Sheet Details - Other Assets (Details) - USD ($) $ in Thousands	Mar. 31, 2020	Sep. 30, 2019
Balance Sheet Details [Abstract]
Intangible assets	$ 246,182	$ 108,903
Contract assets	56,335	53,085
Capitalized contract acquisition costs	37,108	31,218
Other	15,989	10,575
Other Assets, Noncurrent	$ 355,614	$ 203,781

Balance Sheet Details - Accrued

Balance Sheet Details - Accrued Liabilities (Details) - USD ($) $ in Thousands	Mar. 31, 2020	Sep. 30, 2019
Balance Sheet Details [Abstract]
Payroll and benefits	$ 141,076	$ 138,453
Operating lease liabilities, current	46,840	0
Income and other tax accruals	32,007	31,801
Other	66,979	65,615
Accrued Liabilities, Current	$ 286,902	$ 235,869

Balance Sheet Details - Other L

Balance Sheet Details - Other Long-term Liabilities (Details) - USD ($) $ in Thousands	Mar. 31, 2020	Sep. 30, 2019
Balance Sheet Details [Abstract]
Income taxes payable	$ 41,340	$ 42,324
Deferred rent	0	66,103
Other	21,411	23,426
Other long-term liabilities	$ 62,751	$ 131,853

Debt Facilities - Narrative (De

Debt Facilities - Narrative (Details)	Jan. 31, 2020USD ($)	Jan. 24, 2020USD ($)	Mar. 31, 2020USD ($)extension
Term Loan Facility
Debt Instrument [Line Items]
Aggregate principal amount		$ 400,000,000
Debt issuance costs		$ 2,200,000	$ 2,000,000
Redemption percentage		1.25%
Long-term line of credit			$ 400,000,000
Interest rate at end of period			2.765%
Term Loan Facility | London Interbank Offered Rate (LIBOR)
Debt Instrument [Line Items]
Basis spread on variable rate			1.125%
Term Loan Facility | London Interbank Offered Rate (LIBOR) | Minimum
Debt Instrument [Line Items]
Basis spread on variable rate		1.125%
Term Loan Facility | London Interbank Offered Rate (LIBOR) | Maximum
Debt Instrument [Line Items]
Basis spread on variable rate		1.75%
Term Loan Facility | Alternate Base Rate
Debt Instrument [Line Items]
Basis spread on variable rate			0.125%
Term Loan Facility | Alternate Base Rate | Minimum
Debt Instrument [Line Items]
Basis spread on variable rate		0.125%
Term Loan Facility | Alternate Base Rate | Maximum
Debt Instrument [Line Items]
Basis spread on variable rate		0.75%
Revolving Credit Facility
Debt Instrument [Line Items]
Aggregate principal amount	$ 350,000,000
Long-term line of credit			$ 0
Conditional increase in borrowing capacity	$ 150,000,000
Number of extensions | extension			2
Length of extension period			1 year
Outstanding line of credit balance			$ 350,000,000
Revolving Credit Facility | Minimum
Debt Instrument [Line Items]
Commitment fee percentage	0.125%
Revolving Credit Facility | Maximum
Debt Instrument [Line Items]
Commitment fee percentage	0.30%
Revolving Credit Facility | London Interbank Offered Rate (LIBOR) | Minimum
Debt Instrument [Line Items]
Basis spread on variable rate		1.125%
Revolving Credit Facility | London Interbank Offered Rate (LIBOR) | Maximum
Debt Instrument [Line Items]
Basis spread on variable rate	1.75%
Revolving Credit Facility | Alternate Base Rate | Minimum
Debt Instrument [Line Items]
Basis spread on variable rate	0.125%
Revolving Credit Facility | Alternate Base Rate | Maximum
Debt Instrument [Line Items]
Basis spread on variable rate	0.75%

Debt Facilities - Long-term Deb

Debt Facilities - Long-term Debt Maturities (Details) - Term Loan Facility $ in Thousands	Mar. 31, 2020USD ($)
Debt Instrument [Line Items]
2020 (remainder)	$ 5,000
2021	20,000
2022	20,000
2023	355,000
Total	$ 400,000

Leases - Narrative (Details)

Leases - Narrative (Details) ft² in Thousands, $ in Thousands	3 Months Ended	6 Months Ended
	Mar. 31, 2020USD ($)ft²	Mar. 31, 2020USD ($)	Sep. 30, 2019USD ($)
Lessee, Lease, Description [Line Items]
Operating lease right-of-use assets	$ 327,436	$ 327,436	$ 0
Sublease Income		12,500
Sublease income payment remainder of fiscal year	2,300	2,300
Payment to be received between year two and four	$ 10,200	10,200
Office Building
Lessee, Lease, Description [Line Items]
Operating lease, number of square feet | ft²	515
Accounting Standards Update 2016-02
Lessee, Lease, Description [Line Items]
Operating lease right-of-use assets	$ 304,800	304,800
Lease liabilities	$ 386,400	$ 386,400

Leases - Operating Lease Expens

Leases - Operating Lease Expense (Details) - USD ($) $ in Thousands	3 Months Ended	6 Months Ended
	Mar. 31, 2020	Mar. 31, 2020
Leases [Abstract]
Operating lease expense	$ 12,975	$ 24,293
Short-term lease expense	813	1,627
Variable lease expense	4,262	10,101
Total lease expense	$ 18,050	$ 36,021

Leases - Supplemental Balance S

Leases - Supplemental Balance Sheet (Details) - USD ($) $ in Thousands	Mar. 31, 2020	Sep. 30, 2019
Leases [Abstract]
Operating lease right-of-use assets	$ 327,436	$ 0
Operating lease liabilities, current	46,840	0
Operating lease liabilities, long-term	357,645	$ 0
Total lease liabilities	$ 404,485
Weighted average remaining lease term (in years)	10 years 6 months
Weighted average discount rate	2.60%

Leases - Maturities of Lease Li

Leases - Maturities of Lease Liabilities (Details) $ in Thousands	Mar. 31, 2020USD ($)
Leases [Abstract]
2020 (remainder)	$ 26,897
2021	59,217
2022	56,041
2023	43,029
2024	38,334
2025	32,119
Thereafter	215,923
Total lease payments	471,560
Less: imputed interest	(67,075)
Total lease liabilities	$ 404,485

Leases - Operating Lease Future

Leases - Operating Lease Future MInimum ASC 840 (Details) $ in Thousands	Sep. 30, 2019USD ($)
Operating Leases, Future Minimum Payments Due, Fiscal Year Maturity [Abstract]
2020	$ 54,046
2021	50,712
2022	47,550
2023	36,514
2024	33,971
Thereafter	242,826
Operating leases, future minimum payments due	465,619
Operating Leases, Future Minimum Payments Receivable [Abstract]
2020	683
2021	1,051
2022	1,082
2023	368
2024	0
Thereafter	0
Operating leases, future minimum payments receivable	3,184
Future Minimum Operating Net Lease Payments Fiscal Year Maturity [Abstract]
2020	53,363
2021	49,661
2022	46,468
2023	36,146
2024	33,971
Thereafter	242,826
Future minimum operating net lease payments	$ 462,435

Commitments And Contingencies (

Commitments And Contingencies (Details)	6 Months Ended
	Mar. 31, 2020
Commitments and Contingencies Disclosure [Abstract]
Product warranty period	1 year

Income Taxes (Details)

Income Taxes (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Mar. 31, 2020	Mar. 31, 2019	Mar. 31, 2020	Mar. 31, 2019
Income Tax Disclosure [Abstract]
Effective tax rate	26.50%	22.70%	24.30%	21.70%
Unrecognized tax benefit	$ 42.3		$ 42.3

Net Income Per Share (Details)

Net Income Per Share (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended		6 Months Ended
	Mar. 31, 2020	Mar. 31, 2019	Mar. 31, 2020	Mar. 31, 2019
Numerator
Net income	$ 61,379	$ 116,087	$ 159,906	$ 246,992
Denominator
Weighted average shares outstanding — basic (shares)	60,869	59,686	60,758	59,954
Dilutive effect of common shares from stock options and restricted stock units	215	343	259	420
Weighted average shares outstanding — diluted (shares)	61,084	60,029	61,017	60,374
Basic net income per share (dollars per share)	$ 1.01	$ 1.94	$ 2.63	$ 4.12
Diluted net income per share (dollars per share)	$ 1	$ 1.93	$ 2.62	$ 4.09

Restructuring Charges - Narrati

Restructuring Charges - Narrative (Details) $ in Thousands	3 Months Ended			6 Months Ended
	Mar. 31, 2020USD ($)	Dec. 31, 2019USD ($)employee	Mar. 31, 2019USD ($)	Mar. 31, 2020USD ($)	Mar. 31, 2019USD ($)
Restructuring Charges [Abstract]
Number of employees in reduction of force program | employee		75
Restructuring charges | $	$ 0	$ 7,800	$ 0	$ 7,800	$ 0

Segment Information (Details)

Segment Information (Details) $ in Thousands	3 Months Ended		6 Months Ended
	Mar. 31, 2020USD ($)	Mar. 31, 2019USD ($)	Mar. 31, 2020USD ($)geographic_regionsegment	Mar. 31, 2019USD ($)	Sep. 30, 2019USD ($)
Segment Reporting Information [Line Items]
Number of reportable segments | segment			1
Number of geographic regions | geographic_region			3
Net revenues	$ 583,449	$ 544,895	$ 1,152,754	$ 1,088,665
Long-lived assets	232,006		232,006		$ 223,426
United States
Segment Reporting Information [Line Items]
Net revenues	302,192	282,037	577,691	546,788
Long-lived assets	200,035		200,035		194,176
Other
Segment Reporting Information [Line Items]
Net revenues	23,094	25,375	49,157	52,268
Total Americas
Segment Reporting Information [Line Items]
Net revenues	325,286	307,412	626,848	599,056
EMEA
Segment Reporting Information [Line Items]
Net revenues	147,985	136,549	303,937	285,533
Long-lived assets	16,244		16,244		13,451
Asia Pacific
Segment Reporting Information [Line Items]
Net revenues	110,178	$ 100,934	221,969	$ 204,076
Other countries
Segment Reporting Information [Line Items]
Long-lived assets	$ 15,727		$ 15,727		$ 15,799
Ingram Micro, Inc. | Net Revenue | Geographic Concentration
Segment Reporting Information [Line Items]
Concentration risk percentage	17.30%	20.00%	16.90%	18.40%
Westcon Group, Inc. | Net Revenue | Geographic Concentration
Segment Reporting Information [Line Items]
Concentration risk percentage	0.00%	0.00%	0.00%	10.50%
Arrow ECS | Net Revenue | Geographic Concentration
Segment Reporting Information [Line Items]
Concentration risk percentage	0.00%	10.30%	0.00%	10.60%
Tech Data | Net Revenue | Geographic Concentration
Segment Reporting Information [Line Items]
Concentration risk percentage	0.00%	10.00%	0.00%	0.00%

Restructuring Charges - Restruc

Restructuring Charges - Restrucutring Activity (Details) - USD ($) $ in Thousands	3 Months Ended			6 Months Ended
	Mar. 31, 2020	Dec. 31, 2019	Mar. 31, 2019	Mar. 31, 2020	Mar. 31, 2019
Restructuring Reserve [Roll Forward]
Accrued expenses (Beginning balance)		$ 0		$ 0
Restructuring charges	$ 0	$ 7,800	$ 0	7,800	$ 0
Cash payments				(6,956)
Non-cash items				0
Accrued expenses (Ending balance)	$ 844			$ 844

Uncategorized Items - ffiv10q33

Label	Element	Value
Accounting Standards Update 2014-09 [Member]
Cumulative Effect of New Accounting Principle in Period of Adoption	us-gaap_CumulativeEffectOfNewAccountingPrincipleInPeriodOfAdoption	$ 36,048,000
Accounting Standards Update 2014-09 [Member] | Retained Earnings [Member]
Cumulative Effect of New Accounting Principle in Period of Adoption	us-gaap_CumulativeEffectOfNewAccountingPrincipleInPeriodOfAdoption	$ 36,048,000