Hologic (HOLX) 10-Q 8 Feb 18 2018 Q1 Quarterly report Financial data

Document and Entity Information

Document and Entity Information - shares	3 Months Ended
	Dec. 30, 2017	Feb. 05, 2018
Document And Entity Information [Abstract]
Document Type	10-Q
Amendment Flag	false
Document Period End Date	Dec. 30, 2017
Document Fiscal Year Focus	2,018
Document Fiscal Period Focus	Q1
Entity Registrant Name	HOLOGIC INC
Entity Central Index Key	859,737
Current Fiscal Year End Date	--09-30
Entity Filer Category	Large Accelerated Filer
Entity Common Stock, Shares Outstanding		276,529,054

Consolidated Statements of Inco

Consolidated Statements of Income - USD ($) shares in Thousands, $ in Millions	3 Months Ended
	Dec. 30, 2017	Dec. 31, 2016
Revenues:
Product	$ 650.7	$ 613.4
Service and other	140.4	121
Revenues	791.1	734.4
Costs of revenues:
Product	213.7	198.3
Amortization of acquired intangible assets	79.8	73.5
Service and other	73.1	57.8
Gross Profit	424.5	404.8
Operating expenses:
Research and development	54.8	54.4
Selling and marketing	139.5	110
General and administrative	77.9	69.8
Amortization of acquired intangible assets	14.4	21.4
Restructuring charges	3.8	3.2
Operating expenses	290.4	258.8
Income from operations	134.1	146
Interest income	0.8	0.3
Interest expense	(41)	(40.4)
Debt extinguishment loss	(1)	0
Other income, net	2.9	10.2
Income before income taxes	95.8	116.1
(Benefit) provision for income taxes	(310.9)	29.6
Net income	$ 406.7	$ 86.5
Net income per common share:
Basic	$ 1.47	$ 0.31
Diluted	$ 1.45	$ 0.30
Weighted average number of shares outstanding:
Basic	276,856	278,663
Diluted	280,802	284,224

Consolidated Statements of Comp

Consolidated Statements of Comprehensive Income - USD ($) $ in Millions	3 Months Ended
	Dec. 30, 2017	Dec. 31, 2016
Statement of Comprehensive Income [Abstract]
Net income	$ 406.7	$ 86.5
Changes in foreign currency translation adjustment	5.5	(15.7)
Changes in unrealized holding gains and losses on available-for-sale securities, net of tax of $0.2 and $1.5 for the three months December 30, 2017 and December 31, 2016:	0	2.3
Loss reclassified from accumulated other comprehensive loss to the statements of income	0.4	0.1
Changes in pension plans, net of taxes of $0.6 for the three months ended December 30, 2017	0.6	0
Changes in value of hedged interest rate caps, net of tax of $(4.9) and $0.5 for the three months ended December 30, 2017 and December 31, 2016:	(4.3)	0.7
Loss reclassified from accumulated other comprehensive loss to the statements of income	2.3	2.1
Other comprehensive income (loss)	4.5	(10.5)
Comprehensive income	$ 411.2	$ 76

Consolidated Statements of Com4

Consolidated Statements of Comprehensive Income (Parenthetical) - USD ($) $ in Millions	3 Months Ended
	Dec. 30, 2017	Dec. 31, 2016
Statement of Comprehensive Income [Abstract]
Changes in unrealized holding gains and losses on available-for-sale securities. tax	$ 0.2	$ 1.5
Changes in pension plans, tax	0.6	0
Changes in value of hedged interest rate caps, tax	$ (4.9)	$ 0.5

Consolidated Balance Sheets

Consolidated Balance Sheets - USD ($) $ in Millions	Dec. 30, 2017	Sep. 30, 2017
Current assets:
Cash and cash equivalents	$ 664.4	$ 540.6
Accounts receivable, less reserves of $11.5 and $9.8, respectively	548	533.5
Inventories	358.2	331.6
Prepaid income taxes	14.3	22.4
Prepaid expenses and other current assets	53.5	50.5
Total current assets	1,638.4	1,478.6
Property, plant and equipment, net	467.1	472.8
Intangible assets, net	2,681.3	2,772.3
Goodwill	3,176.7	3,171.2
Other assets	84.8	84.7
Total assets	8,048.3	7,979.6
Current liabilities:
Current portion of long-term debt	572.1	1,150.8
Accounts payable	160.3	166.6
Accrued expenses	412.7	375.3
Deferred revenue	163.2	171.2
Current portion of capital lease obligations	1.6	1.6
Total current liabilities	1,309.9	1,865.5
Long-term debt, net of current portion	2,757.7	2,172.1
Capital lease obligations, net of current portion	22.3	22.7
Deferred income tax liabilities	586.4	973.6
Deferred revenue	18.8	20.8
Other long-term liabilities	159.2	140.2
Commitments and contingencies (Note 7)
Stockholders’ equity:
Preferred stock, $0.01 par value – 1,623 shares authorized; 0 shares issued	0	0
Common stock, $0.01 par value – 750,000 shares authorized; 288,750 and 287,853 shares issued, respectively	2.9	2.9
Additional paid-in-capital	5,628.9	5,630.8
Accumulated deficit	(1,976)	(2,382.7)
Treasury stock, at cost – 12,560 shares	(450.1)	(450.1)
Accumulated other comprehensive loss	(11.7)	(16.2)
Total stockholders’ equity	3,194	2,784.7
Total liabilities and stockholders’ equity	$ 8,048.3	$ 7,979.6

Consolidated Balance Sheets (Pa

Consolidated Balance Sheets (Parenthetical) - USD ($) $ in Millions	Dec. 30, 2017	Sep. 30, 2017
Statement of Financial Position [Abstract]
Accounts receivable, reserves	$ 11.5	$ 9.8
Preferred stock, par value (in dollars per share)	$ 0.01	$ 0.01
Preferred stock, authorized (in shares)	1,623,000	1,623,000
Preferred stock, issued (in shares)	0	0
Common stock, par value (in dollars per share)	$ 0.01	$ 0.01
Common stock, authorized (in shares)	750,000,000	750,000,000
Common stock, issued (in shares)	288,750,000	287,853,000
Treasury stock (in shares)	12,560,000	12,560,000

Consolidated Statements of Cash

Consolidated Statements of Cash Flows - USD ($) $ in Millions	3 Months Ended
	Dec. 30, 2017	Dec. 31, 2016
OPERATING ACTIVITIES
Net income	$ 406.7	$ 86.5
Adjustments to reconcile net income to net cash (used in) provided by operating activities:
Depreciation	27	20.4
Amortization of acquired intangibles	94.2	94.9
Non-cash interest expense	8.7	14.3
Stock-based compensation expense	16.4	19.2
Deferred income taxes	(390.7)	(24.6)
Debt extinguishment loss	1	0
Other adjustments and non-cash items	1.2	(6)
Changes in operating assets and liabilities, excluding the effect of acquisitions:
Accounts receivable	(6.4)	21.5
Inventories	(23.3)	(20.7)
Prepaid income taxes	8.1	(0.8)
Prepaid expenses and other assets	(5)	(17.4)
Accounts payable	(7.1)	(17.8)
Accrued expenses and other liabilities	48.9	14.6
Deferred revenue	(10.6)	(14.5)
Net cash provided by operating activities	169.1	169.6
INVESTING ACTIVITIES
Acquisition of businesses, net of cash acquired	(4.1)	0
Capital expenditures	(10.2)	(11.5)
Increase in equipment under customer usage agreements	(11.6)	(13.2)
Proceeds from sale of available-for-sale marketable securities	0.1	0.4
Other activity	(0.4)	(0.9)
Net cash used in investing activities	(26.2)	(25.2)
FINANCING ACTIVITIES
Repayment of long-term debt	(1,331.3)	(18.8)
Proceeds from long-term debt	1,500	0
Repayment of amounts borrowed under accounts receivable securitization program	0	(12)
Proceeds from senior notes	350	0
Payments to extinguish convertible notes	(296.9)	(6.4)
Proceeds from amounts borrowed under revolving credit line	495	0
Repayments of amounts borrowed under revolving credit line	(720)	0
Payment of debt issuance costs	(11.9)	0
Proceeds from issuance of common stock pursuant to employee stock plans	9.5	13.2
Payments under capital lease obligations	(0.4)	0
Payment of minimum tax withholdings on net share settlements of equity awards	(14.3)	(16.4)
Net cash used in financing activities	(20.3)	(40.4)
Effect of exchange rate changes on cash and cash equivalents	1.2	(6.4)
Net increase in cash and cash equivalents	123.8	97.6
Cash and cash equivalents, beginning of period	540.6	548.4
Cash and cash equivalents, end of period	$ 664.4	$ 646

Basis of Presentation

Basis of Presentation	3 Months Ended
	Dec. 30, 2017
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Basis of Presentation	Basis of Presentation The consolidated financial statements of Hologic, Inc. (“Hologic” or the “Company”) presented herein have been prepared pursuant to the rules of the Securities and Exchange Commission (“SEC”) for quarterly reports on Form 10-Q and do not include all of the information and disclosures required by U.S. generally accepted accounting principles (“GAAP”). These financial statements should be read in conjunction with the consolidated financial statements and related notes for the year ended September 30, 2017 included in the Company’s Form 10-K filed with the SEC on November 21, 2017. In the opinion of management, the financial statements and notes contain all adjustments (consisting of normal recurring accruals) considered necessary for a fair presentation of the Company’s financial position, results of operations and cash flows for the periods presented. The consolidated financial statements include the accounts of the Company and its wholly owned subsidiaries. All intercompany transactions and balances have been eliminated in consolidation. The preparation of financial statements in conformity with U.S. GAAP requires management to make significant estimates and assumptions that affect the reported amounts of assets and liabilities and disclosure of contingent assets and liabilities at the date of the financial statements and the reported amounts of revenues and expenses during the reporting periods. Actual results could differ from management’s estimates if past experience or other assumptions do not turn out to be substantially accurate. Operating results for the three months ended December 30, 2017 are not necessarily indicative of the results to be expected for any other interim period or the entire fiscal year ending September 29, 2018 . On March 22, 2017, the Company completed the acquisition of Cynosure, Inc. ("Cynosure"), which resulted in the Company expanding into the medical aesthetics market. Cynosure develops, manufactures and markets aesthetic treatment systems that enable medical practitioners to perform non-invasive and minimally invasive procedures. Cynosure's results of operations are reported within the Company's Medical Aesthetics reportable segment. The Company's acquisition of Cynosure is more fully described in Note 3. Recently Adopted Accounting Pronouncements In December 2016, the FASB issued Accounting Standards Update No. 2016-19, Technical Corrections and Improvements (ASU 2016-19). This guidance changes how companies classify internal-use software from classification within property, plant, and equipment to intangible assets. The amendments in the update are effective for annual periods beginning after December 15, 2016, and were applicable to the Company in fiscal 2018. The Company adopted ASU 2016-19 in the first quarter of fiscal 2018. As a result of the adoption, the Company has reclassified $17.6 million and $18.4 million of internal-use software from property, plant, and equipment to intangible assets as of December 30, 2017 and September 30, 2017, respectively. Additionally, the Company reclassified $12.9 million and $12.3 million of capitalized software embedded in its products from other assets to intangible assets as of December 30, 2017 and September 30, 2017, respectively. Subsequent Events Consideration The Company considers events or transactions that occur after the balance sheet date but prior to the issuance of the financial statements to provide additional evidence for certain estimates or to identify matters that may require additional disclosure. Subsequent events have been evaluated as required. There were no material recognized or unrecognized subsequent events recorded in the unaudited consolidated financial statements as of and for the three months ended December 30, 2017 . On January 19, 2018, the Company completed a private placement of $1.0 billion aggregate principal amount of senior notes, allocated between (i) $600 million of its 4.375% Senior Notes due 2025 (the “New 2025 Senior Notes”) at an offering price of 100% of the aggregate principal amount of the 2025 Senior Notes, plus accrued and unpaid interest from October 10, 2017, and (ii) $400 million of its new 4.625% Senior Notes due 2028 (the "2028 Senior Notes," and together with the New 2025 Senior Notes, the "New Notes") at an offering price of 100% of the aggregate principal amount of the 2028 Senior Notes. In connection with the offering of the New Notes, the Company has called all of its outstanding 5.250% Senior Notes due 2022 (the "2022 Senior Notes"), in aggregate principal amount of $1.0 billion , for redemption on February 15, 2018 at an aggregate redemption price equal to the principal amount of the outstanding 2022 Senior Notes, plus the applicable premium and accrued and unpaid interest through the day immediately preceding the redemption date. Additionally, on January 29, 2018, the Company announced that pursuant to the terms of the indenture for the 2.00% Convertible Senior Notes due 2042 (the “2042 Notes”), holders of the 2042 Notes had the option of requiring the Company to repurchase their 2042 Notes on March 1, 2018 at a repurchase price payable in cash equal to 100% of the accreted principal amount of the 2042 Notes, plus accrued and unpaid interest to, but not including the put date. The Company also announced on January 29, 2018 that it had elected to redeem, on March 6, 2018, all of the then outstanding 2042 Notes at a redemption price payable in cash equal to 100% of the accreted principal amount of the 2042 Notes, plus accrued and unpaid interest to, but not including the redemption date. Holders also have a right to convert their 2042 Notes. In connection with holders’ right to convert the 2042 Notes, the Company announced that it would settle all conversions of 2042 Notes entirely in cash.

Fair Value Measurements

Fair Value Measurements	3 Months Ended
	Dec. 30, 2017
Fair Value Disclosures [Abstract]
Fair Value Measurements	Fair Value Measurements Assets/Liabilities Measured and Recorded at Fair Value on a Recurring Basis The Company has investments in derivative instruments consisting of interest rate caps and forward foreign currency contracts, which are valued using analyses obtained from independent third party valuation specialists based on market observable inputs, representing Level 2 assets. The fair values of the Company's interest rate caps and forward foreign currency contracts represent the estimated amounts the Company would receive or pay to terminate the contracts. Refer to Note 6 for further discussion and information on the interest rate caps and forward foreign currency contracts. The Company has a payment obligation to the participants under its Nonqualified Deferred Compensation Plan (“DCP”). This liability is recorded at fair value based on the underlying value of certain hypothetical investments under the DCP as designated by each participant for their benefit. Since the value of the DCP obligation is based on market prices, the liability is classified within Level 1. Assets and liabilities measured and recorded at fair value on a recurring basis consisted of the following at December 30, 2017 : Fair Value at Reporting Date Using Balance as of December 30, 2017 Quoted Prices in Active Market for Identical Assets (Level 1) Significant Other Observable Inputs (Level 2) Significant Unobservable Inputs (Level 3) Assets: Interest rate cap - derivative 5.3 — 5.3 — Forward foreign currency contracts 0.4 — 0.4 — Total $ 5.7 $ — $ 5.7 $ — Liabilities: Deferred compensation liabilities $ 49.7 $ 49.7 $ — $ — Forward foreign currency contracts 2.6 — 2.6 — Total $ 52.3 $ 49.7 $ 2.6 $ — Assets Measured and Recorded at Fair Value on a Nonrecurring Basis The Company remeasures the fair value of certain assets and liabilities upon the occurrence of certain events. Such assets consist of cost-method equity investments and long-lived assets, including property, plant and equipment, intangible assets and goodwill. There were no such remeasurements for the three months ended December 30, 2017 and December 31, 2016. Disclosure of Fair Value of Financial Instruments The Company’s financial instruments mainly consist of cash and cash equivalents, accounts receivable, cost-method equity investments, interest rate caps, forward foreign currency contracts, insurance contracts, DCP liability, accounts payable and debt obligations. The carrying amounts of the Company’s cash equivalents, accounts receivable and accounts payable approximate their fair value due to the short-term nature of these instruments. The Company’s interest rate caps and forward foreign currency contracts are recorded at fair value. The carrying amount of the insurance contracts are recorded at the cash surrender value, as required by U.S. GAAP, which approximates fair value, and the related DCP liability is recorded at fair value. The Company believes the carrying amounts of its cost-method equity investments approximate fair value. Amounts outstanding under the Company’s Amended and Restated Credit Agreement and Securitization Program of $1.6 billion and $200.0 million aggregate principal, respectively, as of December 30, 2017 are subject to variable rates of interest based on current market rates, and as such, the Company believes the carrying amount of these obligations approximates fair value. The Company’s 2022 Senior Notes and 2025 Senior Notes had a fair value of approximately $1.1 billion and $358.6 million , respectively, as of December 30, 2017 based on their trading prices, representing a Level 1 measurement. The fair values of the Company’s Convertible Notes were based on the trading prices of the respective notes and represents a Level 1 measurement. Refer to Note 5 for the carrying amounts of the various components of the Company’s debt. The estimated fair values of the Company’s Convertible Notes at December 30, 2017 were as follows: 2042 Notes 284.8 2043 Notes 0.3 $ 285.1

Business Combinations

Business Combinations	3 Months Ended
	Dec. 30, 2017
Business Combinations [Abstract]
Business Combinations	Business Combinations Cynosure Inc. On March 22, 2017, the Company completed the acquisition of Cynosure and acquired all of the outstanding shares of Cynosure. Each share of common stock of Cynosure outstanding immediately prior to the effective time of the acquisition was canceled and converted into the right to receive $66.00 in cash. In addition, all outstanding restricted stock units, performance stock units, and stock options were canceled and converted into the right to receive $66.00 per share in cash less the applicable exercise price, as applicable. The acquisition was funded through available cash, and the total purchase price was $1.66 billion . The Company incurred $18.8 million of transaction costs, which were recorded within general and administrative expenses. Cynosure, headquartered in Westford, Massachusetts, develops, manufactures, and markets aesthetic treatment systems that enable plastic surgeons, dermatologists and other medical practitioners to perform non-invasive and minimally invasive procedures to remove hair, treat vascular and benign pigmented lesions, remove multi-colored tattoos, revitalize the skin, reduce fat through laser lipolysis, reduce cellulite, clear nails infected by toe fungus, ablate sweat glands and improve women’s health. Cynosure also markets radiofrequency (RF) energy-sourced medical devices for precision surgical applications such as facial plastic and general surgery, gynecology, ear, nose, and throat procedures, ophthalmology, oral and maxillofacial surgery, podiatry and proctology. Cynosure's results of operations are reported in the Company's Medical Aesthetics reportable segment from the date of acquisition and the goodwill within this reportable segment is solely related to Cynosure. The total purchase price was allocated to Cynosure’s preliminary tangible and identifiable intangible assets and liabilities based on the estimated fair values of those assets as of March 22, 2017, as set forth below. The preliminary purchase price allocation is as follows: Cash $ 107.2 Marketable securities 82.9 Accounts receivable 40.2 Inventory 121.1 Property, plant and equipment 44.1 Other assets and liabilities, net 12.2 Accounts payable and accrued expenses (75.3 ) Deferred revenue (11.2 ) Capital lease obligation (25.2 ) Identifiable intangible assets: Developed technology 736.0 In-process research and development 107.0 Distribution agreement 42.0 Customer relationships 35.0 Trade names 74.0 Deferred income taxes, net (315.7 ) Goodwill 683.5 Purchase Price $ 1,657.8 In performing the preliminary purchase price allocation, the Company considered, among other factors, the intended future use of acquired assets, analysis of historical financial performance and estimates of future performance of Cynosure’s business. The Company has not yet obtained all of the information related to the fair value of the acquired assets and liabilities, primarily taxes, to finalize the purchase price allocation. As part of the preliminary purchase price allocation, the Company has determined the identifiable intangible assets are developed technology, in-process research and development ("IPR&D"), a distribution agreement, customer relationships, and trade names. The preliminary fair value of the intangible assets has been estimated using the income approach, and the cash flow projections were discounted using rates ranging from 11% to 12% , except for the IPR&D assets in which the Company used a range of 14% to 22% . The cash flows are based on estimates used to price the transaction, and the discount rates applied were benchmarked with reference to the implied rate of return from the transaction model and the weighted average cost of capital. The developed technology assets are comprised of know-how, patents and technologies embedded in Cynosure's products and relate to currently marketed products. The developed technology assets primarily comprise the significant product families of Cynosure, primarily SculpSure, Icon, and PicoSure. IPR&D projects relate to in-process projects that have not reached technological feasibility as of the acquisition date and have no alternative future use. The primary basis for determining technological feasibility of these projects is obtaining regulatory approval to market the underlying project or expected commercial release depending on the project. The Company recorded, on a preliminary basis, $107.0 million of IPR&D related to three projects, which were expected to be completed during fiscal 2018 and 2019 with a preliminary cost to complete of approximately $18.0 million . During the fourth quarter of fiscal 2017, the Company obtained regulatory approval for two projects with an aggregate fair value of $61.0 million and these assets were reclassified to developed technology. The remaining project is expected to be completed during fiscal 2019 with an estimated cost to complete of approximately $4.0 million . Given the uncertainties inherent with product development and introduction, there can be no assurance that any of the Company's product development efforts will be successful, completed on a timely basis or within budget, if at all. All of the IPR&D assets were valued using the multiple-period excess earnings method approach. The distribution agreement intangible asset relates to Cynosure's exclusive distribution rights for the MonaLisa Touch device in certain geographic regions. The customer relationships intangible asset pertains to Cynosure's relationships with its end customers and related service arrangements and distributors throughout the world. Trade names relate to the Cynosure corporate name and primary product names, and the Company used the Relief-from-Royalty Method to estimate the fair value of this asset. Developed technology, distribution agreement, customer relationships and trade names are being amortized on a straight-line basis over a weighted average period of 11.8 years, 8 years, 7.7 years and 8.9 years, respectively. The preliminary calculation of the excess of the purchase price over the estimated fair value of the tangible net assets and intangible assets acquired was recorded to goodwill. The factors contributing to the recognition of the preliminary amount of goodwill are based on several strategic and synergistic benefits that are expected to be realized from the Cynosure acquisition. These benefits include the expectation that the Company's entry into the aesthetics market will significantly broaden the Company's offering in women's health. The combined company is expected to benefit from a broader global presence, synergistic utilization of Hologic's direct sales force, primarily its GYN Surgical sales force, with certain Cynosure products, and the Company's entry into an adjacent cash-pay segment. None of the goodwill is expected to be deductible for income tax purposes. In fiscal 2017, Cynosure's revenue and pre-tax loss, which excludes acquisition expenses incurred by the Company, for the period from the acquisition date to September 30, 2017 were $207.5 million and $96.4 million , respectively. The pre-tax loss includes amortization expense, the impact of the step-up in inventory, retention and integration expenses including legal and consulting fees, and restructuring charges. The following unaudited pro forma information presents the combined financial results for the Company and Cynosure as if the acquisition of Cynosure had been completed at the beginning of the prior fiscal year, September 26, 2015 (fiscal 2016): Three Months Ended December 31, 2016 (unaudited) Revenue $ 856.3 Net income $ 74.1 Basic earnings per common share $ 0.27 Diluted earnings per common share $ 0.26 The unaudited pro forma information for the three months ended December 31, 2016 (the first quarter of fiscal 2017) was calculated after applying the Company's accounting policies and the impact of acquisition date fair value adjustments. The pro forma condensed consolidated financial results have been prepared for comparative purposes only and include certain adjustments to reflect pro forma results of operations as if the acquisition occurred on September 27, 2015 (the beginning of fiscal 2016), such as increased amortization for the fair value of acquired intangible assets. The pro forma information does not reflect the effect of costs or synergies that would have been expected to result from the integration of the acquisition. The pro forma information does not purport to be indicative of the results of operations that actually would have resulted had the combination occurred at the beginning of the period presented, or of future results of the consolidated entities. Medicor Medical Supply On April 7, 2017, the Company completed the acquisition of MMS Medicor Medical Supplies GmbH ("Medicor") for a purchase price of approximately $19.0 million , which includes a working capital adjustment of $2.0 million that was paid in the fourth quarter of fiscal 2017, and a holdback of $1.9 million that is payable two years from the date of acquisition. Medicor was a long-standing distributor of the Company's Breast and Skeletal Health products in Germany, Austria and Switzerland. Based on the Company's preliminary valuation, it has allocated $5.4 million of the purchase price to the preliminary value of intangible assets, which have a weighted average life of 7.7 years, and $8.9 million to goodwill. The remaining $4.7 million of purchase price has been allocated to the acquired tangible assets and liabilities. The allocation of the purchase price is preliminary as the Company continues to gather information supporting the acquired assets and liabilities. Emsor, S.A. On December 11, 2017, the Company completed the acquisition of Emsor S.A. ("Emsor") for a purchase price of approximately $13.1 million , which includes a holdback of $0.5 million that is payable eighteen months from the date of acquisition, and contingent consideration which the Company has estimated at $2.0 million . The contingent consideration is payable upon Emsor achieving predefined amounts of cumulative revenue over a two year period from the date of acquisition. Emsor was a distributor of the Company's Breast and Skeletal Health products in Spain and Portugal. Based on the Company's preliminary valuation, it has allocated $2.8 million of the purchase price to the preliminary value of intangible assets and $3.5 million to goodwill. The remaining $6.8 million of purchase price has been allocated to acquired tangible assets and liabilities. The allocation of the purchase price is preliminary as the Company continues to gather information supporting the acquired assets and liabilities.

Restructuring Charges

Restructuring Charges	3 Months Ended
	Dec. 30, 2017
Restructuring and Related Activities [Abstract]
Restructuring Charges	Restructuring Charges The Company evaluates its operations for opportunities to improve operational effectiveness and efficiency, including facility and operations consolidation, and to better align expenses with revenues. In addition, the Company continually assesses its management and organizational structure. As a result of these assessments, the Company has undertaken various restructuring actions, which are described below. The following table displays charges related to these actions recorded in the fiscal 2018 year to date period ( three months ended December 30, 2017 ) and fiscal 2017 (the year ended September 30, 2017) and a rollforward of the accrued balances from September 30, 2017 to December 30, 2017 : Fiscal 2018 Actions Fiscal 2017 Actions Fiscal 2016 Actions Total Restructuring Charges Fiscal 2017 charges: Workforce reductions $ — $ 8.5 $ — $ 8.5 Facility closure costs — — 4.8 4.8 Fiscal 2017 restructuring charges $ — $ 8.5 $ 4.8 $ 13.3 Fiscal 2018 charges: Workforce reductions $ 3.8 $ — $ — $ 3.8 Fiscal 2018 restructuring charges $ 3.8 $ — $ — $ 3.8 Fiscal 2018 Actions Fiscal 2017 Actions Fiscal 2016 Actions Other Total Rollforward of Accrued Restructuring Balance as of September 30, 2017 $ — $ 7.5 $ 3.7 $ 0.3 $ 11.5 Fiscal 2018 charges 3.8 — — — 3.8 Stock-based compensation (1.3 ) — — — (1.3 ) Severance payments and adjustments (0.9 ) (2.3 ) (0.2 ) — (3.4 ) Other payments — — (0.3 ) (0.1 ) (0.4 ) Balance as of December 30, 2017 $ 1.6 $ 5.2 $ 3.2 $ 0.2 $ 10.2 Fiscal 2018 Actions During the first quarter of fiscal 2018, the Company decided to terminate certain employees across the organization, including a corporate executive and sales and marketing personnel in its Diagnostics and Medical Aesthetics reportable segments. The charges were recorded pursuant to ASC 712, Compensation-Nonretirement Postemployment Benefits (ASC 712) or ASC 420, Exit or Disposal Cost Obligations (ASC 420) depending on the employee. As such, the Company recorded severance and benefits charges of $3.8 million in the first quarter. Included within this charge is $1.3 million related to the modification of equity awards. Fiscal 2017 Actions In connection with its acquisition of Cynosure, the Company decided to terminate certain Cynosure executives in the second quarter of fiscal 2017 and recorded $1.5 million in severance and benefits charges. During the third and fourth quarters of fiscal 2017, the Company terminated additional executives and employees and recorded $4.3 million and $1.3 million , respectively, in severance and benefits charges. Fiscal 2016 Actions In connection with the closure of the Bedford, Massachusetts facility, during the first quarter of fiscal 2017 the Company recorded $3.5 million for lease obligation charges related to a section of the facility that the Company had determined met the cease-use date criteria. The Company made certain assumptions regarding the time period it would take to obtain a subtenant and the sublease rates it can obtain. During the third quarter of fiscal 2017, the Company updated its assumption regarding the time period it will take to obtain a subtenant at the Bedford location and as a result recorded an additional $1.3 million lease obligation charge. These estimates may vary from the actual sublease agreements executed, if at all, resulting in an adjustment to the charge. The Company has vacated other portions of the building but not the entire facility, and at this time does not meet the cease-use date criteria to record additional restructuring charges.

Borrowings and Credit Arrangeme

Borrowings and Credit Arrangements	3 Months Ended
	Dec. 30, 2017
Debt Disclosure [Abstract]
Borrowings and Credit Arrangements	Borrowings and Credit Arrangements The Company’s borrowings consisted of the following: December 30, September 30, Current debt obligations, net of debt discount and deferred issuance costs: Term Loan $ 46.7 $ 121.3 Revolver 120.0 345.0 Securitization Program 200.0 200.0 Convertible Notes 205.4 484.5 Total current debt obligations $ 572.1 $ 1,150.8 Long-term debt obligations, net of debt discount and deferred issuance costs: Term Loan 1,430.1 1,190.5 2022 Senior Notes 982.6 981.6 2025 Senior Notes 345.0 — Total long-term debt obligations $ 2,757.7 $ 2,172.1 Total debt obligations $ 3,329.8 $ 3,322.9 Amended and Restated Credit Agreement On October 3, 2017, the Company and certain of its domestic subsidiaries entered into an Amended and Restated Credit and Guaranty Agreement (the "Amended and Restated Credit Agreement") with Bank of America, N.A. in its capacity as Administrative Agent, Swing Line Lender and L/C Issuer, and certain other lenders from time to time party thereto. The Amended and Restated Credit Agreement amends and restates the Company's prior credit and guaranty agreement, originally dated as of May 29, 2015 (the "Prior Credit Agreement"). The proceeds under the Amended and Restated Credit Agreement of $1.8 billion were used, among other things, to pay off the Term Loan of $1.32 billion and the Revolver then outstanding under the Company's Prior Credit Agreement. Borrowings under the Amended and Restated Credit Agreement are secured by first-priority liens on, and a first-priority security interest in, substantially all of the assets of the Company's U.S. subsidiaries, with certain exceptions. The credit facilities (the “Amended and Restated Credit Facilities”) under the Amended and Restated Credit Agreement consist of: • A $1.5 billion secured term loan to the Company ("Amended Term Loan") with a maturity date of October 3, 2022; and • A secured revolving credit facility (the "Amended Revolver") under which the the Company may borrow up to $1.5 billion , subject to certain sublimits, with a maturity date of October 3, 2022. At the closing, the Company borrowed $345 million under the Amended Revolver, which was fully repaid during October 2017. As of December 30, 2017, the Company had $120.0 million outstanding under the Amended Revolver. Borrowings under the Amended and Restated Credit Facilities bear interest, at the Company's option and in each case plus an applicable margin as follows: • Amended Term Loan : at the Base Rate, Eurocurrency Rate or LIBOR Daily Floating Rate (as defined in the Amended and Restated Credit Agreement), • Amended Revolver : if funded in U.S. dollars, the Base Rate, Eurocurrency Rate, or LIBOR Daily Floating Rate, and, if funded in an alternative currency, the Eurocurrency Rate; and if requested under the swing line sublimit, the Base Rate. The applicable margin to the Base Rate, Eurocurrency Rate, or LIBOR Daily Floating Rate is subject to specified changes depending on the total net leverage ratio as defined in the Amended and Restated Credit Agreement. The borrowings of the Amended Term Loan initially bear interest at an annual rate equal to the Eurocurrency Rate (i.e., the LIBOR rate) plus an Applicable Rate equal to 1.50% . The borrowings of the Amended Revolver initially bear interest at a rate equal to the LIBOR Daily Floating Rate plus an Applicable Rate equal to 1.50% . The Company is also required to pay a quarterly commitment fee calculated on the undrawn committed amount available under the Amended Revolver. The Company is required to make scheduled principal payments under the Amended Term Loan in increasing amounts ranging from $9.375 million per three -month period commencing with the three-month period ending on December 29, 2017 to $37.5 million per three-month period commencing with the three-month period ending on December 23, 2021. The remaining balance of the Amended Term Loan and any amounts outstanding under the Amended Revolver are due at maturity. In addition, subject to the terms and conditions set forth in the Amended and Restated Credit Agreement, the Company is required to make certain mandatory prepayments from the net proceeds of specified types of asset sales (subject to certain reinvestment rights), debt issuances and insurance recoveries (subject to certain reinvestment rights). These mandatory prepayments are required to be applied by the Company, first, to the Amended Term Loan, second, to any outstanding amount under any Swing Line Loans (as defined in the Amended and Restated Credit Agreement), third, to the Amended Revolver, fourth to prepay any outstanding reimbursement obligations with respect to Letters of Credit (as defined in the Amended and Restated Credit Agreement) and fifth, to cash collateralize any Letters of Credit. Subject to certain limitations, the Company may voluntarily prepay any of the Amended and Restated Credit Facilities without premium or penalty. Borrowings outstanding under the Amended and Restated Credit Agreement and the Prior Credit Agreement for the three months ended December 30, 2017 and December 31, 2016 had weighted-average interest rates of 2.75% and 2.05% , respectively. The interest rate on the outstanding Amended Term Loan borrowing at December 30, 2017 was 3.07% . Interest expense under the Amended and Restated Credit Agreement aggregated $12.4 million for the three months ended December 30, 2017 , which includes non-cash interest expense of $0.7 million related to the amortization of the deferred issuance costs and accretion of the debt discount. Interest expense under the Prior Credit Agreement aggregated $9.8 million for the three months ended December 31, 2016 , which includes $1.1 million of non-cash interest expense related to the amortization of the deferred issuance costs and accretion of the debt discount. The Amended and Restated Credit Agreement contains affirmative and negative covenants customarily applicable to senior secured credit facilities, including covenants restricting the ability of the Company, subject to negotiated exceptions, to incur additional indebtedness and grant additional liens on its assets, engage in mergers or acquisitions or dispose of assets, enter into sale-leaseback transactions, pay dividends or make other distributions, voluntarily prepay other indebtedness, enter into transactions with affiliated persons, make investments, and change the nature of their businesses. In addition, the Amended and Restated Credit Agreement requires the the Company to maintain certain financial ratios. The Amended and Restated Credit Agreement also contains customary representations and warranties and events of default, including payment defaults, breach of representations and warranties, covenant defaults, cross defaults and an event of default upon a change of control of the Company. Borrowings are secured by first-priority liens on, and a first-priority security interest in, substantially all of the assets of the Company, with certain exceptions. For example, borrowings under the Amended and Restated Credit Agreement are not secured by those accounts receivable that are transferred to the special purpose entity under the Company's Accounts Receivable Securitization program. The Amended and Restated Credit Agreement contains total net leverage ratio and interest coverage ratio financial covenants measured as of the last day of each fiscal quarter and an excess cash flow prepayment requirement measured as of the end of each fiscal year. The total net leverage ratio was 5.00 :1.00 beginning on the Company's fiscal quarter ended December 30, 2017, and then decreases over time to 4.50 :1.00 for the quarter ending March 27, 2021. The interest coverage ratio was 3.75 :1.00 beginning on the Company's fiscal quarter ended December 30, 2017, and remains as such for each quarter thereafter. The total net leverage ratio is defined as the ratio of the Company's consolidated net debt as of the quarter end to its consolidated adjusted EBITDA (as defined in the Amended and Restated Credit Agreement) for the four -fiscal quarter period ending on the measurement date. The interest coverage ratio is defined as the ratio of the Company's consolidated adjusted EBITDA for the prior four-fiscal quarter period ending on the measurement date to adjusted consolidated cash interest expense (as defined in the Amended and Restated Credit Agreement) for the same measurement period. The Company was in compliance with these covenants as of December 30, 2017. The Company evaluated the Amended and Restated Credit Agreement for derivatives pursuant to ASC 815, Derivatives and Hedging , and identified embedded derivatives that required bifurcation as the features are not clearly and closely related to the host instrument. The embedded derivatives were a default provision, which could require additional interest payments, and a provision requiring contingent payments to compensate the lenders for changes in tax deductions. The Company determined that the fair value of these embedded derivatives was nominal as of December 30, 2017. Pursuant to ASC 470, Debt (ASC 470), the accounting for the Amended and Restated Credit Agreement was evaluated on a creditor-by-creditor basis with regard to the Amended and Restated Credit Agreement to determine whether each transaction should be accounted for as a modification or extinguishment. Certain creditors under the Amended and Restated Credit Agreement did not participate in this refinancing transaction and ceased being creditors of the Company. As a result, the Company recorded a debt extinguishment loss of $1.0 million in the first quarter of fiscal 2018 to write-off the pro-rata amount of unamortized debt discount and deferred issuance costs related to these creditors. For the remainder of the creditors, this transaction was accounted for as a modification because on a creditor-by-creditor basis the present value of the cash flows between the two debt instruments before and after the transaction was less than 10% . Pursuant to ASC 470, subtopic 50-40, third-party costs of $1.7 million related to this transaction were recorded as interest expense and $4.9 million was recorded as a reduction to debt representing deferred issuance costs and fees paid directly to the lenders. 2025 Senior Notes On October 10, 2017, the Company completed a private placement of $350 million aggregate principal amount of its 4.375% Senior Notes due 2025 (the “2025 Senior Notes”) at an offering price of 100% of the aggregate principal amount of the 2025 Senior Notes. The 2025 Senior Notes are general senior unsecured obligations of the Company and are guaranteed on a senior unsecured basis by certain domestic subsidiaries of Hologic (the “ 2025 Domestic Guarantors”). The 2025 Senior Notes mature on October 15, 2025 and bear interest at the rate of 4.375% per year, payable semi-annually on April 15 and October 15 of each year, commencing on April 15, 2018. The Company recorded interest expense of $3.5 million for the three months ended December 30, 2017 which includes non-cash interest expense of $0.1 million related to the amortization of the deferred issuance costs and accretion of the debt discount. The Company may redeem the 2025 Senior Notes at any time prior to October 15, 2020 at a price equal to 100% of the aggregate principal amount so redeemed, plus accrued and unpaid interest, if any, to the redemption date and a make-whole premium set forth in the Indenture. The Company may also redeem up to 35% of the aggregate principal amount of the 2025 Senior Notes with the net cash proceeds of certain equity offerings at any time and from time to time before October 15, 2020, at a redemption price equal to 104.375% of the aggregate principal amount so redeemed, plus accrued and unpaid interest, if any, to the redemption date. The Company also has the option to redeem the 2025 Senior Notes on or after: October 15, 2020 through October 14, 2021 at 102.188% of par; October 15, 2021 through October 14, 2022 at 101.094% of par; and October 15, 2022 and thereafter at 100% of par. In addition, if the Company undergoes a change of control coupled with a decline in ratings, as provided in the 2025 Indenture, the Company will be required to make an offer to purchase each holder’s 2025 Senior Notes at a price equal to 101% of their principal amount, plus accrued and unpaid interest, if any, to the repurchase date. On January 19, 2018, the Company completed a private placement of $1.0 billion aggregate principal amount of senior notes, which included $600 million of additional 4.375% Senior Notes due 2025 (the “New 2025 Senior Notes”), issued under a supplement to the 2025 Indenture. See “Subsequent Events” below. 2022 Senior Notes The Company's 5.250% Senior Notes due 2022 (the “2022 Senior Notes”) mature on July 15, 2022 and bear interest at the rate of 5.250% per year, payable semi-annually on January 15 and July 15 of each year, commencing on January 15, 2016. The Company recorded interest expense of $14.0 million and $15.1 million for the three months ended December 30, 2017 and December 31, 2016, respectively, which includes non-cash interest expense of $1.0 million and $1.0 million , respectively, related to the amortization of the deferred issuance costs and accretion of the debt discount. In connection with the offering of the New 2025 Senior Notes and the Company’s 4.625% Senior Notes due 2028, the Company has called all of its outstanding 2022 Senior Notes, in the aggregate principal amount of $1.0 billion , for redemption on February 15, 2018 at an aggregate redemption price equal to the principal amount of the outstanding 2022 Senior Notes, plus the applicable premium and accrued and unpaid interest through the day immediately preceding the redemption date. See “Subsequent Events” below. Convertible Notes On various dates during the first quarter of fiscal 2018, the Company entered into privately negotiated repurchase transactions and extinguished $39.3 million principal amount of its 2.00% Convertible Senior Notes due 2042 (the "2042 Notes") for total payments of $52.8 million . This amount includes the conversion premium resulting from the Company's stock price on the date of the transactions being in excess of the conversion prices of $31.175 . As a result, on a gross basis, $13.4 million of the consideration paid was allocated to the reacquisition of the equity component of the original instrument, which was recorded net of deferred taxes of $3.8 million within additional paid-in-capital. On December 15, 2017, pursuant to the provisions of the indenture governing the Company's 2.00% Convertible Senior Notes due December 15, 2043 (the "2043 Notes"), the Company redeemed or repurchased an aggregate of $201.7 million in original principal amount of the 2043 Notes then outstanding for an aggregate repurchase price of approximately $244.1 million , representing the then accreted principal amount of the 2043 Notes. The remaining $0.3 million in original principal amount of the 2043 Notes were converted, and the Company elected to settle these conversions, which will occur in the second quarter of fiscal 2018. The term "Convertible Notes" refers to the 2042 Notes and the 2043 Notes. Interest expense under the Convertible Notes was as follows: Three Months Ended December 30, December 31, Amortization of debt discount $ 2.9 $ 5.2 Amortization of deferred financing costs 0.1 0.2 Principal accretion 1.6 4.6 Non-cash interest expense 4.6 10.0 2.00% accrued interest (cash) 1.1 2.0 $ 5.7 $ 12.0 Subsequent Events 2025 Senior Notes and 2028 Senior Notes On January 19, 2018, the Company completed a private placement of $1.0 billion aggregate principal amount of senior notes, allocated between (i) an additional $600 million aggregate principal amounts of its 2025 Senior Notes pursuant to a supplement to the indenture governing the Company's existing 2025 Senior Notes, at an offering price of 100% of the aggregate principal amount of the 2025 Senior Notes, plus accrued and unpaid interest from October 10, 2017 and (ii) $400 million aggregate principal amounts of its 4.625% Senior Notes due 2028 (the "2028 Senior Notes") at an offering price of 100% of the aggregate principal amount of the 2028 Senior Notes. The new 2025 Senior Notes have the same terms as the existing 2025 Senior Notes. The 2028 Senior Notes are general senior unsecured obligations of the Company and are guaranteed on a senior unsecured basis by certain domestic subsidiaries of Hologic (the “2028 Domestic Guarantors”). The 2028 Senior Notes were issued pursuant to an indenture (the “2028 Indenture”), dated as of January 19, 2018 among the Company, the 2028 Domestic Guarantors and Wells Fargo Bank, National Association, as trustee. The 2028 Senior Notes mature on February 1, 2028 and bear interest at the rate of 4.625% per year, payable semi-annually on February 1 and August 1 of each year, commencing on August 1, 2018. The 2028 Indenture contains covenants which limit, among other things, the ability of the Company and the Guarantors to create liens and engage in certain sale and leaseback transactions. These covenants are subject to a number exceptions and qualifications. The Company may redeem the 2028 Senior Notes at any time prior to February 1, 2023 at a price equal to 100% of the aggregate principal amount so redeemed, plus accrued and unpaid interest, if any, to the redemption date and a make-whole premium set forth in the Indenture. The Company may also redeem up to 35% of the aggregate principal amount of the 2028 Senior Notes with the net cash proceeds of certain equity offerings at any time and from time to time before February 1, 2021, at a redemption price equal to 104.625% of the aggregate principal amount so redeemed, plus accrued and unpaid interest, if any, to the redemption date. The Company also has the option to redeem the 2028 Senior Notes on or after: February 1, 2023 through February 1, 2024 at 102.312% of par; February 1, 2024 through February 1, 2025 at 101.541% of par; February 1, 2025 through February 1, 2026 at 100.770% of par; and February 1, 2026 and thereafter at 100% of par. In addition, if the Company undergoes a change of control coupled with a decline in ratings, as provided in the 2028 Indenture, the Company will be required to make an offer to purchase each holder’s 2028 Senior Notes at a price equal to 101% of their principal amount, plus accrued and unpaid interest, if any, to the repurchase date. 2042 Notes On January 29, 2018, the Company announced that pursuant to the terms of the indenture for the 2.00% Convertible Senior Notes due 2042 (the “2042 Notes”), holders of the 2042 Notes had the option of requiring the Company to repurchase their 2042 Notes on March 1, 2018 at a repurchase price payable in cash equal to 100% of the accreted principal amount of the 2042 Notes, plus accrued and unpaid interest to, but not including the put date. The accreted principal amount of the 2042 notes will be $206.0 million as of the repurchase date. The Company also announced on January 29, 2018 that, it had elected to redeem, on March 6, 2018, all of the then outstanding 2042 Notes at a redemption price payable in cash equal to 100% of the accreted principal amount of the 2042 Notes, plus accrued and unpaid interest to, but not including the redemption date. Holders also have a right to convert their 2042 Notes. Based on a closing price of the Company’s common stock of $42.75 per share (the closing price for the Company’s common stock on December 29, 2017), the conversion value for the outstanding 2042 notes would be $1,371 per $1,000 of original principal amount of the notes, or $282.6 million in the aggregate. The conversion value of the notes would increase or decrease to the extent that the trading price of the Company’s common stock increases or decreases. The Company has elected to settle any conversion of the 2042 Notes entirely in cash.

Derivatives

Derivatives	3 Months Ended
	Dec. 30, 2017
Derivative Instruments and Hedging Activities Disclosure [Abstract]
Derivatives	Derivatives Interest Rate Cap - Cash Flow Hedge The Company is exposed to certain risks arising from both its business operations and economic conditions. The Company manages its exposure to some of its interest rate risk through the use of interest rate caps, which are derivative financial instruments. The Company does not use derivatives for speculative purposes. For a derivative that is designated as a cash flow hedge, changes in the fair value of the derivative are recognized in accumulated other comprehensive income ("AOCI") to the extent the derivative is effective at offsetting the changes in the cash flows being hedged until the hedged item affects earnings. To the extent there is any hedge ineffectiveness, changes in fair value relating to the ineffective portion are immediately recognized in earnings in other income (expense) in the Consolidated Statements of Income. During fiscal 2015, the Company entered into separate interest rate cap agreements with multiple counter-parties to help mitigate the interest rate volatility associated with the variable interest rate on amounts borrowed under the term loan feature of its credit facilities (see Note 6). Interest rate cap agreements provide the right to receive cash if the reference interest rate rises above a contractual rate. The aggregate premium paid for the interest rate cap agreements was $13.2 million , which was the initial fair value of the instruments recorded in the Company's financial statements. During fiscal 2017, the Company entered into new separate interest rate cap agreements with multiple counter-parties to extend the expiration date of its hedges by an additional year. The aggregate premium paid for the interest rate cap agreements was $1.9 million , which was the initial fair value of the instruments recorded in the Company's financial statements. The critical terms of the interest rate caps were designed to mirror the terms of the Company’s LIBOR-based borrowings under its Prior Credit Agreement and Amended and Restated Credit Agreement and therefore are highly effective at offsetting the cash flows being hedged. The Company designated these derivatives as cash flow hedges of the variability of the LIBOR-based interest payments on $1.0 billion of principal, which ended on December 29, 2017 and which will end on December 30, 2018 for the interest rate cap agreements entered into in fiscal 2015 and fiscal 2017, respectively. As of December 30, 2017 , the Company determined that the existence of hedge ineffectiveness, if any, was immaterial, and all changes in the fair value of the interest rate caps were recorded in the Consolidated Statements of Comprehensive Income as a component of AOCI. During the three months ended December 30, 2017 and December 31, 2016 , $2.3 million and $2.1 million , respectively, was reclassified from AOCI to the Company’s Consolidated Statements of Income related to the interest rate cap agreements. The Company expects to similarly reclassify a loss of approximately $1.9 million from AOCI to the Consolidated Statements of Income in the next twelve months. The aggregate fair value of these interest rate caps was $5.3 million and $4.8 million at December 30, 2017 and September 30, 2017 , respectively, and is included in Prepaid expenses and other current assets on the Company’s Consolidated Balance Sheet. Refer to Note 2 “Fair Value Measurements” above for related fair value disclosures. Forward Foreign Currency Contracts The Company enters into forward foreign currency exchange contracts to mitigate certain operational exposures from the impact of changes in foreign currency exchange rates. Such exposures result from the portion of the Company's operations that are denominated in currencies other than the U.S. dollar, primarily the Euro, the UK Pound, the Australian dollar, the Canadian dollar and the Japanese Yen. These foreign currency exchange contracts are entered into to support transactions made in the ordinary course of business and are not speculative in nature. The contracts are generally for periods of one year or less. The Company has not elected hedge accounting for any of the forward foreign currency contracts it has executed; however, the Company may seek to apply hedge accounting in future scenarios. The change in the fair value of these contracts is recognized directly in earnings as a component of other income (expense), net. During the three months ended December 30, 2017 and December 31, 2016 , the Company recorded net realized loss of $0.2 million and a net realized gain of $1.2 million , respectively, from settling forward foreign currency contracts and unrealized gains of $1.5 million and $8.4 million , respectively, on the mark-to-market for its outstanding forward foreign currency contracts. As of December 30, 2017 , the Company had outstanding forward foreign currency contracts that were not designated for hedge accounting and were used to hedge fluctuations in the U.S. dollar of forecasted transactions denominated in the Euro, UK Pound, Australian dollar, Canadian Dollar and Japanese Yen with an aggregate notional amount of $157.4 million . Financial Instrument Presentation The table below presents the fair value of the Company's derivative financial instruments as well as their classification on the balance sheet as of December 30, 2017 : Balance Sheet Location December 30, 2017 September 30, 2017 Assets: Derivative instruments designated as a cash flow hedge: Interest rate cap agreements Prepaid expenses and other current assets $ 5.3 $ 3.6 Interest rate cap agreements Other assets — 1.2 $ 5.3 $ 4.8 Derivatives not designated as hedging instruments: Forward foreign currency contracts Prepaid expenses and other current assets $ 0.4 $ 0.4 Liabilities: Derivatives not designated as hedging instruments: Forward foreign currency contracts Accrued expenses $ 2.6 $ 4.0 The following table presents the unrealized gain recognized in AOCI related to the interest rate caps for the following reporting periods: Three Months Ended December 30, 2017 December 31, 2016 Amount of gain (loss) recognized in other comprehensive income, net of taxes: Interest rate cap agreements $ (4.3 ) $ 0.7 The following table presents the adjustment to fair value (realized and unrealized) recorded within the Consolidated Statements of Income for derivative instruments for which the Company did not elect hedge accounting: Derivatives not classified as hedging instruments Amount of Gain (Loss) Recognized in Income Location of Gain (Loss) Recognized in Income Three Months Ended December 30, 2017 Three Months Ended December 31, 2016 Forward foreign currency contracts $ 1.2 $ 9.6 Other income, net

Commitments and Contingencies

Commitments and Contingencies	3 Months Ended
	Dec. 30, 2017
Commitments and Contingencies Disclosure [Abstract]
Commitments and Contingencies	Commitments and Contingencies Litigation and Related Matters On June 9, 2010, Smith & Nephew, Inc. ("Smith & Nephew") filed suit against Interlace Medical, Inc. ("Interlace"), which the Company acquired on January 6, 2011, in the United States District Court for the District of Massachusetts. The complaint alleged that the Interlace MyoSure hysteroscopic tissue removal device infringed U.S. patent 7,226,459 (the '459 patent). On November 22, 2011, Smith & Nephew filed suit against the Company in the United States District Court for the District of Massachusetts. The complaint alleged that use of the MyoSure tissue removal system infringed U.S. patent 8,061,359 (the '359 patent). Both complaints sought preliminary and permanent injunctive relief and unspecified damages. On September 4, 2012, following a two week trial, the jury returned a verdict of infringement of both the '459 and '359 patents and assessed damages of $4.0 million . A two-day bench trial regarding the Company’s assertion of inequitable conduct on the part of Smith & Nephew with regard to the '359 patent began on December 10, 2012 and oral arguments on the issue of inequitable conduct were presented on February 27, 2013. On June 27, 2013, the Court denied the Company’s motions related to inequitable conduct and allowed Smith & Nephew’s request for injunction, but ordered that enforcement of the injunction be stayed until final resolution, including appeal, of the current re-examinations of both patents at the United States Patent and Trademark Office (“USPTO”). The Court also rejected the jury’s damage award and ordered the parties to identify a mechanism for resolving the damages issue. The USPTO issued final decisions that the claims of the '459 and the '359 patents asserted as part of the litigation are not patentable, which decisions Smith & Nephew appealed to the U.S. Patent Trial and Appeal Board ("PTAB"). In 2016, the PTAB (i) affirmed the USPTO decision with respect to the '459 patent, holding that the claims at issue are invalid, and (ii) reversed the USPTO decision with respect to the '359 patent, holding that the claims at issue are not invalid. The Company and Smith & Nephew have appealed the decisions by the Patent Trial and Appeal Board on the '359 patent and the '459 patent, respectively, to the U.S. Court of Appeals for the Federal Circuit ("Court of Appeals"). Briefing on both appeals is completed. Oral arguments were held in the '459 patent appeal on October 24, 2017 and in the '359 patent appeal on December 7, 2017. On January 30, 2018, the Court of Appeals issued a decision in the '459 patent appeal that affirmed-in-part and reversed-in-part the PTAB ruling and remanded the matter to the PTAB for further proceedings. At this time, based on available information regarding this litigation, the Company is unable to reasonably assess the ultimate outcome of this case or determine an estimate, or a range of estimates, of potential losses. On April 11, 2017, Minerva Surgical, Inc. (“Minerva”) filed suit against the Company and Cytyc Surgical Products, LLC (“Cytyc”) in the United States District Court for the Northern District of California alleging that the Company’s and Cytyc’s NovaSure ADVANCED endometrial ablation device infringes Minerva’s U.S. patent 9,186,208. Minerva is seeking a preliminary and permanent injunction against the Company and Cytyc from selling this NovaSure device as well as enhanced damages and interest, including in lost profits, price erosion and/or royalty. On January 5, 2018, the Court denied Minerva's motion for a preliminary injunction. At this time, based on available information regarding this litigation, the Company is unable to reasonably assess the ultimate outcome of this case or determine an estimate, or a range of estimates, of potential losses. In January 2012, Enzo Life Sciences, Inc. ("Enzo") filed suit against the Company's subsidiary, Gen-Probe Incorporated ("Gen-Probe"), in the United States District Court for the District of Delaware, alleging that certain of Gen-Probe’s diagnostics products, including products that incorporate Gen-Probe’s hybridization protection assay technology (HPA), which include the Aptima line of products, infringe Enzo’s U.S. patent 6,992,180 (the '180 patent). On March 6, 2012, Enzo filed suit against the Company in the United States District Court for the District of Delaware, alleging that products based on the Company's Invader chemistry platform, such as Cervista HPV HR and Cervista HPV 16/18, infringe the '180 patent. On July 16, 2012, Enzo amended its complaint to include additional products that include HPA or TaqMan reagent chemistry, including the Progensa, AccuProbe and Prodesse product lines. The Company counter-claimed for non-infringement, invalidity and unenforceability of the '180 patent. On September 30, 2013, Enzo filed its infringement contentions which added products including "Torch" probes (e.g., MilliPROBE Real-Time Detection System for Mycoplasma), PACE and certain Procleix assays. Both complaints sought preliminary and permanent injunctive relief and unspecified damages. Summary judgment and Daubert motions were filed by the parties on December 15, 2016. A hearing on the summary judgment motions was held on April 4, 2017, and on June 28, 2017, the Court ruled that the '180 patent is invalid for nonenablement. Final judgment was entered on July 19, 2017, and on August 18, 2017, Enzo filed a notice of appeal with the Court of Appeals for the Federal Circuit. Enzo’s opening appeal brief was filed on November 28, 2017, and the Company’s responsive brief is due March 8, 2018. At this time, based on available information regarding this litigation, the Company is unable to reasonably assess the ultimate outcome of this case or determine an estimate, or a range of estimates, of potential losses. On March 27, 2015, Enzo filed an additional suit against the Company in the United States District Court for the District of Delaware. The complaint alleges that certain additional Company molecular diagnostic products, including, inter alia, the Procleix Parvo/HAV assays and coagulation products, including the Invader Factor II test and the Invader Factor V test, also infringe the '180 patent. The complaint further alleged that certain of the Company’s molecular diagnostic products, including the Company’s Progensa PCA3, Aptima and Procleix products using target capture technology infringe Enzo’s U. S. Patent 7,064,197 (the '197 patent). On June 11, 2015, this matter was stayed pending the resolution of summary judgment motions in the other related suits involving the '197 patent. The litigation remains stayed. On March 30, 2016, Hologic filed two requests for inter partes review of the ‘197 patent at the USPTO. The USPTO instituted the two inter partes reviews on all challenged claims on October 4, 2016. Combined oral arguments for the two inter partes reviews were held on June 1, 2017. On September 28 and October 2, 2017, the PTAB issued final written decisions in the two inter partes reviews finding that all of the challenged claims of the ‘197 patent are unpatentable. In response to the final written decisions, Enzo filed notices of appeal on November 29, 2017, and the United States Court of Appeals for the Federal Circuit consolidated Enzo’s appeals on December 14, 2017. Enzo’s opening brief is due March 12, 2018. At this time, based on available information regarding this litigation and the related inter partes reviews, the Company is unable to reasonably assess the ultimate outcome of this case or determine an estimate, or a range of estimates, of potential losses. On October 3, 2016, Enzo filed an additional suit against the Company in the United States District Court for the District of Delaware. The complaint alleges that all of the Company's Progensa PCA3, Aptima and Procleix products infringe U.S. Patent 6,221,581 (the '581 patent). On November 28, 2016, the Company filed an answer and counterclaims of non-infringement, invalidity and unenforceability. On June 30, 2017, Hologic filed its initial invalidity contentions, which provide support for finding that the asserted claims of the '581 patent are invalid based on anticipation, obviousness, lack of adequate written description and enablement, and indefiniteness. On August 31, 2017, the Company and Enzo filed supplemental invalidity charts and supplemental infringement charts, respectively. The parties filed their proposed claim constructions on September 28, 2017. The parties’ claim construction briefs are due in April 2018. On October 4, 2017, the Company filed for inter partes review of the ‘581 patent with the USPTO based on Enzo’s asserted claims. Enzo filed its preliminary response on January 19, 2018. A decision on whether to institute inter partes review is expected in April 2018. At this time, based on available information regarding this litigation, the Company is unable to reasonably assess the ultimate outcome of this case or determine an estimate, or a range of estimates, of potential losses. On February 3, 2017, bioMérieux, S.A. and bioMérieux, Inc. (collectively “bioMérieux”) filed suit against the Company in the United States District Court for the Middle District of North Carolina. The complaint alleged that the Company’s Aptima HIV-1 RNA Qualitative assay and Aptima HIV-1 Quant Dx assay, as well as products manufactured by the Company and sold to Grifols, S.A. and Grifols Diagnostic Solutions Inc. (“Grifols USA”) for resale under the names Procleix HIV-1/HCV assay, Procleix Ultrio assay, and Procleix Ultrio Plus assay, infringe U.S. Patent Nos. 8,697,352 and 9,074,262. On April 3, 2017, the Company and Grifols USA filed a Motion to dismiss asking the Court to dismiss the complaint in its entirety for bioMérieux’s failure to state a claim upon which relief can be granted. On June 9, 2017, Hologic and Grifols USA filed a supplemental motion to dismiss for improper venue. bioMérieux filed a response to the venue motion on June 30, 2017, and Hologic and Grifols USA responded by filing a brief in further support of their motion to dismiss for improper venue on July 14, 2017. On January 3, 2018, the district court judge for the Middle District of North Carolina granted the parties’ consent motion to transfer the case to Delaware. At this time, based on available information regarding this litigation, the Company is unable to reasonably assess the ultimate outcome of this case or determine an estimate, or range of estimates, of potential losses. On July 27, 2016, plaintiff ARcare, Inc., individually and as putative representative of a purported nationwide class, filed a complaint against Cynosure. The plaintiff alleges that Cynosure violated the Telephone Consumer Protection Act by: (i) sending fax advertisements that did not comply with statutory and Federal Communications Commission requirements that senders provide recipients with certain information about how to opt out from receiving faxed advertisements in the future; and (ii) sending unsolicited fax advertisements. The complaint sought damages, declaratory and injunctive relief, and attorneys’ fees on behalf of a purported class of all recipients of purported fax advertisements that the plaintiff alleges did not receive an adequate opt-out notice. On September 30, 2016, Cynosure answered the complaint and denied liability. On September 7, 2016, the plaintiff sent a demand letter seeking a class settlement for statutory damages under Massachusetts General Laws, Chapter 93A § 9 (“Chapter 93A”). On October 7, 2016, Cynosure responded denying any liability under Chapter 93A, but offering the plaintiff statutory damages of $25 on an individual basis. In March 2017, Cynosure and ARcare entered into a settlement agreement, subject to court approval, which requires Cynosure to pay settlement compensation of $8.5 million notwithstanding the number of claims filed. If approved, Cynosure would receive a full release from the settlement class concerning the conduct alleged in the complaint. As a result of the settlement agreement, Cynosure recorded a charge of $9.2 million , in the period ended December 31, 2016, which is still accrued on the Company's balance sheet as of December 30, 2017 . On March 17, 2017, a purported shareholder of Cynosure, Michael Guido, filed an action against Cynosure in the Court of Chancery of the State of Delaware pursuant to Section 220 of the Delaware General Corporation Law seeking the production of certain books and records, including books and records related to the acquisition of Cynosure by Hologic. The action follows Cynosure’s rejection of Mr. Guido’s demand for these books and records on the ground that he had not met the requirements of the statute. In addition to books and records, the complaint seeks reasonable attorneys’ fees. The Company filed an answer to the complaint on April 10, 2017. At this time, based on available information regarding this matter, the Company is unable to reasonably assess the ultimate outcome of this case or determine an estimate, or range of estimates, of potential losses. The Company is a party to various other legal proceedings and claims arising out of the ordinary course of its business. The Company believes that except for those matters described above there are no other proceedings or claims pending against it the ultimate resolution of which could have a material adverse effect on its financial condition or results of operations. In all cases, at each reporting period, the Company evaluates whether or not a potential loss amount or a potential range of loss is probable and reasonably estimable under ASC 450, Contingencies. Legal costs are expensed as incurred.

Net Income Per Share

Net Income Per Share	3 Months Ended
	Dec. 30, 2017
Earnings Per Share [Abstract]
Net Income Per Share	Net Income Per Share A reconciliation of basic and diluted share amounts is as follows: Three Months Ended December 30, December 31, Basic weighted average common shares outstanding 276,856 278,663 Weighted average common stock equivalents from assumed exercise of stock options and stock units 2,212 3,143 Incremental shares from Convertible Notes premium 1,734 2,418 Diluted weighted average common shares outstanding 280,802 284,224 Weighted-average anti-dilutive shares related to: Outstanding stock options 2,272 1,442 Stock units 216 13 The Company has outstanding Convertible Notes, and the principal balance and any conversion premium may be satisfied, at the Company’s option, by issuing shares of common stock, cash or a combination of shares and cash. The Company's current policy is that it will settle the principal balance of the Convertible Notes in cash. As such, the Company applies the treasury stock method to these securities and the dilution related to the conversion premium of the 2042 and 2043 Notes is included in the calculation of diluted weighted-average shares outstanding to the extent each issuance is dilutive based on the average stock price during each reporting period being greater than the conversion price of the respective Notes.

Stock-Based Compensation

Stock-Based Compensation	3 Months Ended
	Dec. 30, 2017
Disclosure of Compensation Related Costs, Share-based Payments [Abstract]
Stock-Based Compensation	Stock-Based Compensation The following presents stock-based compensation expense in the Company’s Consolidated Statements of Income: Three Months Ended December 30, December 31, Cost of revenues $ 2.2 $ 2.8 Research and development 2.5 2.8 Selling and marketing 2.9 2.7 General and administrative 7.5 10.9 Restructuring 1.3 — $ 16.4 $ 19.2 The Company granted 1.6 million and 0.9 million stock options during the three months ended December 30, 2017 and December 31, 2016 , respectively, with weighted-average exercise prices of $40.82 and $37.62 , respectively. There were 6.7 million options outstanding at December 30, 2017 with a weighted-average exercise price of $31.20 . The Company uses a binomial model to determine the fair value of its stock options. The weighted-average assumptions utilized to value these stock options are indicated in the following table: Three Months Ended December 30, December 31, Risk-free interest rate 2.1 % 1.8 % Expected volatility 35.3 % 36.6 % Expected life (in years) 4.7 4.7 Dividend yield — — Weighted average fair value of options granted $ 13.00 $ 12.18 The Company granted 0.8 million and 0.9 million restricted stock units (RSUs) during each of the three months ended December 30, 2017 and December 31, 2016 , respectively, with weighted-average grant date fair values of $40.79 and $37.58 per unit, respectively. As of December 30, 2017 , there were 2.0 million unvested RSUs outstanding with a weighted-average grant date fair value of $37.72 per unit. In addition, the Company granted 0.4 million and 0.1 million performance stock units (PSUs) during the three months ended December 30, 2017 and December 31, 2016 , respectively, to members of its senior management team, which have a weighted-average grant date fair value of $40.86 and $37.64 per unit, respectively. Each recipient of PSUs is eligible to receive between zero and 200% of the target number of shares of the Company’s common stock at the end of three years provided the Company’s defined Return on Invested Capital metrics are achieved. The Company is recognizing compensation expense ratably over the required service period based on its estimate of the number of shares that will vest. If there is a change in the estimate of the number of shares that are probable of vesting, the Company will cumulatively adjust compensation expense in the period that the change in estimate is made. The Company also granted 0.3 million and 0.1 million market based awards (MSUs) to its senior management team during the three months ended December 30, 2017 and December 31, 2016 , respectively. Each recipient of MSUs is eligible to receive between zero and 200% of the target number of shares of the Company’s common stock at the end of three years based upon achieving a certain total shareholder return relative to a defined peer group. The MSUs were valued at $49.45 and $48.90 per share using the Monte Carlo simulation model. The Company is recognizing compensation expense for the MSUs ratably over the service period. At December 30, 2017 , there was $37.0 million and $98.4 million of unrecognized compensation expense related to stock options and stock units (comprised of RSUs and PSUs), respectively, to be recognized over a weighted-average period of 3.1 and 2.1 years, respectively.

Disposition

Disposition	3 Months Ended
	Dec. 30, 2017
Discontinued Operations and Disposal Groups [Abstract]
Dispositions	Disposition Blood Screening Business On December 14, 2016, the Company entered into a definitive agreement to sell the assets of its blood screening business to its long-time commercial partner, Grifols for a sales price of $1.85 billion in cash, subject to adjustment based on an estimated closing amount of inventory. The divestiture was completed on January 31, 2017, and the Company received $1.865 billion . The sale resulted in a gain of $899.7 million recorded in the second quarter of fiscal 2017 within operations in the Consolidated Statements of Income. As a result of this disposition and proceeds received, the Company recorded a tax obligation of $649.5 million , which was paid in fiscal 2017. Upon the closing of the transaction, the Company's existing collaboration agreement with Grifols terminated, and a new collaboration agreement was executed as part of this transaction pursuant to which the Company provides certain research and development services to Grifols. In addition, the Company agreed to provide transition services to Grifols over the next two to three years depending on the nature of the respective service, including the manufacture of inventory. The Company also agreed to sell Panther instrumentation and certain supplies to Grifols as part of a long term supply agreement. In determining the accounting for the multiple elements of the overall arrangement, the Company allocated $13.1 million of the proceeds to these elements based on their estimated fair values. The Company determined this disposal did not qualify to be reported as a discontinued operation as the blood screening business was deemed not to be strategic to the Company and has not had and will not have a major effect on the Company's operations and financial results. Under the previous collaboration agreement, the Company performed research and development activities and manufacturing, while Grifols performed the commercial and distribution activities. The blood screening business was embedded within the Company's molecular diagnostics business, and the Company retains ownership and will continue to use the intellectual property for the underlying technology of its molecular diagnostics assays and instrumentation. Income from operations of the disposed business presented below represents the pretax profit of the business as it was operated prior to the date of disposition. The operating expenses include only those that were incurred directly by and were retained by the disposed business and are now incurred by Grifols. As noted above, the Company is performing a number of transition services and the financial impact from these services are not included in income from operations presented below. The Company is in effect serving as a contract manufacturer of assays for Grifols for a two to three year period from the date of disposal. Revenue and income from operations of the disposed business for the three month period ended December 31, 2016 was $65.2 million and $28.6 million , respectively. Under the long term supply agreement, transition services agreement to manufacture assays and research and development services, the Company recorded revenue of $12.6 million for the three months ended December 30, 2017.

Other Balance Sheet Information

Other Balance Sheet Information	3 Months Ended
	Dec. 30, 2017
Balance Sheet Related Disclosures [Abstract]
Other Balance Sheet Information	Other Balance Sheet Information December 30, September 30, Inventories Raw materials $ 114.2 $ 95.7 Work-in-process 44.6 45.0 Finished goods 199.4 190.9 $ 358.2 $ 331.6 Property, plant and equipment Equipment $ 363.7 $ 357.9 Equipment under customer usage agreements 379.0 368.7 Building and improvements 172.7 172.0 Leasehold improvements 61.1 60.6 Land 46.4 46.3 Furniture and fixtures 21.0 20.8 1,043.9 1,026.3 Less – accumulated depreciation and amortization (576.8 ) (553.5 ) $ 467.1 $ 472.8

Business Segments and Geographi

Business Segments and Geographic Information	3 Months Ended
	Dec. 30, 2017
Segment Reporting [Abstract]
Business Segments and Geographic Information	Business Segments and Geographic Information The Company has five reportable segments: Diagnostics, Breast Health, Medical Aesthetics, GYN Surgical and Skeletal Health. Certain reportable segments represent an aggregation of operating units within each segment. The Company measures and evaluates its reportable segments based on segment revenues and operating income adjusted to exclude the effect of non-cash charges, such as intangible asset amortization expense, intangible asset and goodwill impairment charges, acquisition related fair value adjustments and integration expenses, restructuring, divestiture and facility consolidation charges and other one-time or unusual items. Identifiable assets for the five principal operating segments consist of inventories, intangible assets, goodwill, and property, plant and equipment. The Company fully allocates depreciation expense to its five reportable segments. The Company has presented all other identifiable assets as corporate assets. There were no inter-segment revenues during the three months ended December 30, 2017 and December 31, 2016 . Segment information is as follows: Three Months Ended December 30, December 31, Total revenues: Diagnostics $ 284.6 $ 325.4 Breast Health 288.0 273.3 Medical Aesthetics 91.3 — GYN Surgical 107.5 114.8 Skeletal Health 19.7 20.9 $ 791.1 $ 734.4 Income (loss) from operations: Diagnostics $ 36.5 $ 41.1 Breast Health 89.7 85.2 Medical Aesthetics (23.0 ) — GYN Surgical 30.2 25.5 Skeletal Health 0.7 (5.8 ) $ 134.1 $ 146.0 Depreciation and amortization: Diagnostics $ 64.7 $ 84.9 Breast Health 4.9 5.1 Medical Aesthetics 28.5 — GYN Surgical 22.9 25.1 Skeletal Health 0.2 0.2 $ 121.2 $ 115.3 Capital expenditures: Diagnostics $ 11.9 $ 10.3 Breast Health 3.5 2.2 Medical Aesthetics 1.6 — GYN Surgical 2.4 4.1 Skeletal Health 0.7 0.3 Corporate 1.7 7.8 $ 21.8 $ 24.7 December 30, September 30, Identifiable assets: Diagnostics $ 2,583.0 $ 2,621.6 Breast Health 840.5 824.0 Medical Aesthetics 1,723.9 1,751.2 GYN Surgical 1,477.8 1,494.6 Skeletal Health 26.8 25.5 Corporate 1,396.3 1,262.7 $ 8,048.3 $ 7,979.6 The Company had no customers that represented greater than 10% of consolidated revenues during the three months ended December 30, 2017 and December 31, 2016 . The Company operates in the following major geographic areas as noted in the below chart. Revenue data is based upon customer location. Other than the United States, no single country accounted for more than 10% of consolidated revenues. The Company’s sales in Europe are predominantly derived from France, Germany and the United Kingdom. The Company’s sales in Asia-Pacific are predominantly derived from China, Australia and Japan. The “Rest of World” designation includes Canada, Latin America and the Middle East. Revenues by geography as a percentage of total revenues were as follows: Three Months Ended December 30, December 31, United States 75.5 % 77.9 % Europe 11.5 % 10.7 % Asia-Pacific 8.7 % 8.4 % Rest of World 4.3 % 3.0 % 100.0 % 100.0 %

Income Taxes

Income Taxes	3 Months Ended
	Dec. 30, 2017
Income Tax Disclosure [Abstract]
Income Taxes	Income Taxes In accordance with ASC 740, Income Taxes (ASC 740), each interim period is considered integral to the annual period, and tax expense is measured using an estimated annual effective tax rate. An entity is required to record income tax expense each quarter based on its annual effective tax rate estimated for the full fiscal year and use that rate to provide for income taxes on a current year-to-date basis, adjusted for discrete taxable events that occur during the interim period. The Company’s effective tax rate for the three months ended December 30, 2017 was (324.5)% compared to 25.5% for the corresponding period in the prior year. The benefit recorded in the current quarter is primarily due to the impact of the Tax Cuts and Jobs Act (the "Act") enacted on December 22, 2017. As a result of this law, US corporations are subject to lower income tax rates, and the Company is required to remeasure its US net deferred tax liabilities at a lower rate, resulting in a net benefit of $355.2 million recorded in the provision for income taxes. Partially offsetting this benefit, the Company recorded a charge of $26.0 million for transition taxes related to the deemed repatriation of foreign earnings. For the current quarter, in addition to the items noted, the effective tax rate was lower than the statutory tax rate primarily due to the impact of earnings in jurisdictions subject to lower tax rates, and the domestic production activities deduction benefit. For the three months ended December 31, 2016, the effective tax rate was lower than the statutory tax rate primarily due to the tax benefit from restricted stock units upon vesting, earnings in jurisdictions subject to lower tax rates, and the domestic production activities deduction benefit. US Tax Reform The Act reduces the US federal corporate income tax rate from 35% to 21% , requires companies to pay a one-time transition tax on earnings of certain foreign subsidiaries that were previously tax deferred, and creates new taxes on certain foreign sourced earnings. At December 30, 2017, the Company has not completed its accounting for the tax effects of enactment of the Act; however, as described below, the Company has made a reasonable estimate of the effects on its existing deferred tax balances and the one-time transition tax, and recognized a provisional net benefit of $329.2 million , which is included in income tax expense. On December 22, 2017, the SEC issued Staff Accounting Bulletin No. 118, Income Tax Accounting Implications of the Tax Cuts and Jobs Act (“SAB 118”) directing SEC registrants to consider the impact of the US legislation as “provisional” when it does not have the necessary information available, prepared or analyzed (including computations) in reasonable detail to complete its accounting for the change in tax law. In accordance with SAB 118, the additional estimated net income tax benefit of $329.2 million represents the Company’s best estimate based on its interpretation of the US legislation as the Company is still accumulating data to finalize the underlying calculations, or in certain cases, the US Treasury is expected to issue further guidance on the application of certain provisions of the US legislation. In the three months ended December 30, 2017, the Company revised its estimated annual effective rate to reflect a change in the federal statutory income tax rate from 35% to 21% . The rate change is administratively effective at the beginning of the Company’s fiscal year, using a blended rate for the annual period. The Company's blended statutory income tax rate for fiscal 2018 is 24.5% . Deferred tax assets and liabilities : The Company re-measured certain deferred tax assets and liabilities based on the rates at which they are expected to reverse in the future, which is 24.5% for fiscal 2018 reversals and 21% for post-fiscal 2018 reversals. However, the Company is still analyzing certain aspects of the Act and refining its calculations, which could potentially affect the measurement of these balances or potentially give rise to new deferred tax amounts. The provisional net benefit amount recorded related to the re-measurement of the Company’s deferred tax balance was $355.2 million . Foreign tax effects : The one-time transition tax is based on the Company’s total post-1986 earnings and profits (E&P) which were previously deferred from US income taxes. The Company recorded a provisional amount for its one-time transition tax liability related to the deemed repatriation of the earnings of its foreign subsidiaries, resulting in an increase in income tax expense of $26.0 million . The Company has not yet finalized its calculation of the total post-1986 foreign E&P for these foreign subsidiaries. Further, the transition tax is based in part on the amount of those earnings held in cash and other specified assets. This amount may change when the Company finalizes the calculation of its post-1986 foreign E&P previously deferred from US federal taxation and finalizes the amounts held in cash or other specified assets. No additional income taxes have been provided for any remaining undistributed foreign earnings not subject to the transition tax and any additional outside basis difference inherent in these entities as these amounts continue to be indefinitely reinvested in foreign operations. The Company continues to evaluate this assertion in its ongoing analysis of the effects of tax reform on the Company's strategic initiatives. The Company believes that determining the amount of unrecognized deferred tax liability related to any remaining undistributed foreign earnings not subject to the transition tax and additional outside basis difference in these entities (i.e., basis difference in excess of that subject to the one time transition tax) is not practicable. Further, starting in fiscal 2019, the Act subjects a US shareholder of a controlled foreign corporation to current tax on “global intangible low-taxed income” (GILTI) and establishes a tax on certain payments from corporations subject to US tax to related foreign persons, also referred to as base erosion and anti-abuse tax (BEAT). Because of the complexity of the new international tax provisions not applicable to the Company until fiscal 2019, the Company is continuing to evaluate these provisions of the Act and the application of ASC 740. Non-Income Tax Matters The Company is subject to tax examinations for value added, sales-based, payroll and other non-income tax items. A number of these examinations are ongoing in various jurisdictions. The Company takes certain non-income tax positions in the jurisdictions in which it operates pursuant to ASC 450. In the normal course of business, the Company's positions and conclusions related to its non-income tax positions could be challenged, resulting in assessments by governmental authorities. In January 2018, the Company settled an ongoing state tax audit for approximately $11.0 million , resulting in a reversal of $4.0 million recorded to general and administrative expenses in the first quarter of fiscal 2018.

Intangible Assets and Goodwill

Intangible Assets and Goodwill	3 Months Ended
	Dec. 30, 2017
Goodwill and Intangible Assets Disclosure [Abstract]
Intangible Assets and Goodwill	Intangible Assets and Goodwill Intangible assets consisted of the following: Description As of December 30, 2017 As of September 30, 2017 Gross Carrying Value Accumulated Amortization Gross Carrying Value Accumulated Amortization Acquired intangible assets: Developed technology $ 4,528.8 $ 2,266.7 $ 4,528.7 $ 2,186.8 In-process research and development 46.0 — 46.0 — Customer relationships 556.7 402.8 552.8 393.8 Trade names 310.3 161.1 310.3 156.4 Distribution agreement 42.0 4.1 42.0 2.8 Non-competition agreements 1.5 0.1 1.5 0.1 Business licenses 2.5 2.2 2.4 2.2 Total acquired intangible assets $ 5,487.8 $ 2,837.0 $ 5,483.7 $ 2,742.1 Internal-use software 65.8 48.2 64.5 46.1 Capitalized software embedded in products 15.5 2.6 14.3 2.0 Total intangible assets $ 5,569.1 $ 2,887.8 $ 5,562.5 $ 2,790.2 The estimated remaining amortization expense of the Company's acquired intangible assets as of December 30, 2017 for each of the five succeeding fiscal years is as follows: Remainder of Fiscal 2018 $ 283.1 Fiscal 2019 $ 366.0 Fiscal 2020 $ 354.8 Fiscal 2021 $ 333.2 Fiscal 2022 $ 320.3 The Company conducted its fiscal 2017 impairment test on the first day of the fourth quarter, and used a discounted cash flow method (DCF) to estimate the fair value of its reporting units as of July 2, 2017. The Company believes it used reasonable estimates and assumptions about future revenue, cost projections, cash flows, market multiples and discount rates as of the measurement date. As a result of completing Step 1, all of the Company's reporting units had fair values exceeding their carrying values, and as such, Step 2 of the impairment test was not required. However, one of its reporting units, Medical Aesthetics, had a fair value as of the measurement date that exceeded its carrying value by 2% with goodwill of $683.5 million . The Medical Aesthetics reporting unit is solely comprised of the Cynosure, Inc. business, which the Company acquired on March 22, 2017. In connection with the Company's annual strategic planning process and annual goodwill impairment test, it lowered its estimated financial projections for this business as a result of its then current operating performance being below expectations, which the Company primarily attributed to the significant turnover in the U.S. sales force in 2017 following the date of acquisition. The Company is continuing its efforts to rebuild the U.S. sales force and this continues to affect short term performance. The Company’s long-term outlook for the Medical Aesthetics business has not materially changed. The Company is continuing to monitor the operating performance of this reporting unit compared to the projections used in the annual impairment test, as well as current market and business conditions, to determine if an event has occurred or circumstances change that would more likely than not reduce the fair value of the reporting unit below its carrying amount. The Company has evaluated these factors and determined that no significant events occurred or circumstances changed during the period ended December 30, 2017 that would suggest it is more likely than not that the fair value of the reporting unit has declined below its carrying value. In the event the Company is unsuccessful in its efforts to rebuild the U.S. sales force or its efforts take significantly longer than expected, or other adverse conditions are identified, future operating performance may be below forecasted projections. If this occurs, the Company may need to revise its long-term growth rates or increase discount rates, and these factors could result in a decline in the fair value of the reporting unit and the Company may be required to record a goodwill impairment charge.

Product Warranties

Product Warranties	3 Months Ended
	Dec. 30, 2017
Guarantees [Abstract]
Product Warranties	Product Warranties Product warranty activity was as follows: Balance at Beginning of Period Provisions Settlements/ Adjustments Balance at End of Period Three Months Ended: December 30, 2017 $ 17.0 $ 4.3 $ (5.1 ) $ 16.2 December 31, 2016 $ 5.0 $ 2.6 $ (1.7 ) $ 5.9

Accumulated Other Comprehensive

Accumulated Other Comprehensive Loss	3 Months Ended
	Dec. 30, 2017
Accumulated Other Comprehensive Income [Abstract]
Accumulated Other Comprehensive Loss	Accumulated Other Comprehensive Loss The following tables summarize the changes in accumulated balances of other comprehensive loss for the periods presented: Three Months Ended December 30, 2017 Foreign Currency Translation Marketable Securities Pension Plans Hedged Interest Rate Caps Total Beginning Balance $ (18.5 ) $ (0.4 ) $ (1.6 ) $ 4.3 $ (16.2 ) Other comprehensive income (loss) before reclassifications 5.5 — 0.6 (4.3 ) 1.8 Amounts reclassified to statement of income — 0.4 — 2.3 2.7 Ending Balance $ (13.0 ) $ — $ (1.0 ) $ 2.3 $ (11.7 ) Three Months Ended December 31, 2016 Foreign Currency Translation Marketable Securities Pension Plans Hedged Interest Rate Caps Total Beginning Balance $ (26.1 ) $ (0.3 ) $ (2.5 ) $ (3.4 ) $ (32.3 ) Other comprehensive income (loss) before reclassifications (15.7 ) 2.3 — 0.7 (12.7 ) Amounts reclassified to statement of income — 0.1 — 2.1 2.2 Ending Balance $ (41.8 ) $ 2.1 $ (2.5 ) $ (0.6 ) $ (42.8 ) In the first quarter of fiscal 2017, one of the Company's cost-method equity investments became a marketable security, and the Company recorded the increase in value on a gross basis of $4.0 million to other comprehensive income.

New Accounting Pronouncements

New Accounting Pronouncements	3 Months Ended
	Dec. 30, 2017
Accounting Policies [Abstract]
New Accounting Pronouncements	New Accounting Pronouncements In January 2017, the FASB issued ASU No. 2017-04, Intangibles-Goodwill and Other (Topic 350) . This guidance simplifies how companies calculate goodwill impairments by eliminating Step 2 of the impairment test. The guidance requires companies to compare the fair value of a reporting unit to its carrying amount and recognize an impairment charge for the amount by which the carrying amount exceeds the reporting unit's fair value. The guidance is effective for annual periods beginning after December 15, 2019, and is applicable to the Company in fiscal 2020. Early adoption is permitted. In October 2016, the FASB issued ASU No. 2016-16, Income Taxes (Topic 740). The guidance requires companies to recognize the income tax effects of intercompany sales and transfers of assets, other than inventory, in the income statement as income tax expense (or benefit) in the period in which the transfer occurs. The guidance is effective for annual periods beginning after December 15, 2017, and is applicable to the Company in fiscal 2019. Early adoption is permitted as of the beginning of an annual reporting period. The Company is currently evaluating the impact of the adoption of ASU 2016-16 on its consolidated financial position and results of operations. In August 2016, the FASB issued ASU No. 2016-15, Statement of Cash Flow (Topic 230) . The guidance reduces diversity in how certain cash receipts and cash payments are presented and classified in the Statements of Cash Flows. Certain of ASU 2016-15 requirements are as follows: 1) cash payments for debt prepayment or debt extinguishment costs should be classified as cash outflows for financing activities, 2) contingent consideration payments made soon after a business combination should be classified as cash outflows for investing activities and cash payment made thereafter should be classified as cash outflows for financing up to the amount of the contingent consideration liability recognized at the acquisition date with any excess classified as operating activities, 3) cash proceeds from the settlement of insurance claims should be classified on the basis of the nature of the loss, 4) cash proceeds from the settlement of Corporate-Owned Life Insurance (COLI) Policies should be classified as cash inflows from investing activities and cash payments for premiums on COLI policies may be classified as cash outflows for investing activities, operating activities, or a combination of investing and operating activities, and 5) cash paid to a tax authority by an employer when withholding shares from an employee's award for tax-withholding purposes should be classified as cash outflows for financing activities. The guidance is effective for annual periods beginning after December 15, 2017, and is applicable to the Company in fiscal 2019. Early adoption is permitted. The adoption of ASU 2016-15 is not expected to have a material effect on the Company's consolidated financial statements. In June 2016, the FASB issued ASU No. 2016-13, Financial Instruments - Credit Losses (Topic 326) . The guidance requires that financial assets measured at amortized cost be presented at the net amount expected to be collected. The allowance for credit losses is a valuation account that is deducted from the amortized cost basis. The income statement reflects the measurement of credit losses for newly recognized financial assets, as well as the expected credit losses during the period. The measurement of expected credit losses is based upon historical experience, current conditions, and reasonable and supportable forecasts that affect the collectability of the reported amount. Credit losses relating to available-for-sale debt securities will be recorded through an allowance for credit losses rather than as a direct write-down to the security. The updated guidance is effective for annual periods beginning after December 15, 2019, and is applicable to the Company in fiscal 2021. Early adoption is permitted. The Company is currently evaluating the impact of the adoption of ASU 2016-13 on its consolidated financial position and results of operations. In February 2016, the FASB issued ASU No. 2016-02, Leases (Topic 842). The guidance requires an entity to recognize a right-of-use asset and a lease liability for virtually all of its leases with terms of more than 12 months. Recognition, measurement and presentation of expenses will depend on classification as a finance or operating lease. The amendments also require certain quantitative and qualitative disclosures about leasing arrangements. The guidance is effective for annual periods beginning after December 15, 2018, and is applicable to the Company in fiscal 2020. Early adoption is permitted. The updated guidance requires a modified retrospective adoption. The Company is currently evaluating the anticipated impact of the adoption of ASU 2016-02 on its consolidated financial position and results of operations. In January 2016, the FASB issued ASU No. 2016-01, Financial Instruments - Overall (Subtopic 825-10): Recognition and Measurement of Financial Assets and Financial Liabilities . This guidance changes how entities measure equity investments that do not result in consolidation and are not accounted for under the equity method. Entities will be required to measure these investments at fair value at the end of each reporting period and recognize changes in fair value in net income. A practicability exception will be available for equity investments that do not have readily determinable fair values, however; the exception requires the Company to consider relevant transactions that can be reasonably known to identify any observable price changes that would impact the fair value . This guidance also changes certain disclosure requirements and other aspects of current U.S. GAAP. This guidance is effective for annual periods beginning after December 15, 2017, and is applicable to the Company in fiscal 2019 . Early adoption is permitted. The Company is currently evaluating the anticipated impact of the adoption of ASU 2016-01 on its consolidated financial position and results of operations. In May 2014, the FASB issued ASU No. 2014-09, Revenue from Contracts with Customers (Topic 606) , which provides guidance for revenue recognition. This ASU is applicable to any entity that either enters into contracts with customers to transfer goods or services or enters into contracts for the transfer of nonfinancial assets. ASU 2014-09 will supersede the revenue recognition requirements in Topic 605, Revenue Recognition , and most industry-specific guidance. The standard’s core principle is that a company will recognize revenue when it transfers promised goods or services to customers in an amount that reflects the consideration to which the company expects to be entitled to receive in exchange for those goods or services. In doing so, companies will need to use more judgment and make more estimates than under current U.S. GAAP. These judgments may include identifying performance obligations in the contract, estimating the amount of variable consideration to include in the transaction price and allocating the transaction price to each separate performance obligation. ASU 2014-09 is effective prospectively for fiscal years, and interim reporting periods within those years, beginning after December 15, 2017, which is fiscal 2019 for the Company. The Company will adopt Topic 606 effective September 30, 2018 and has established a cross-functional team to evaluate and implement the new revenue recognition rules. The Company will adopt Topic 606 using the modified retrospective method but has not finalized evaluating the anticipated impact of the adoption of ASU 2014-09 on its consolidated financial position and results of operations.

New Accounting Pronouncements N

New Accounting Pronouncements New Accounting Pronouncements (Policies)	3 Months Ended
	Dec. 30, 2017
Accounting Policies [Abstract]
New Accounting Pronouncements	New Accounting Pronouncements In January 2017, the FASB issued ASU No. 2017-04, Intangibles-Goodwill and Other (Topic 350) . This guidance simplifies how companies calculate goodwill impairments by eliminating Step 2 of the impairment test. The guidance requires companies to compare the fair value of a reporting unit to its carrying amount and recognize an impairment charge for the amount by which the carrying amount exceeds the reporting unit's fair value. The guidance is effective for annual periods beginning after December 15, 2019, and is applicable to the Company in fiscal 2020. Early adoption is permitted. In October 2016, the FASB issued ASU No. 2016-16, Income Taxes (Topic 740). The guidance requires companies to recognize the income tax effects of intercompany sales and transfers of assets, other than inventory, in the income statement as income tax expense (or benefit) in the period in which the transfer occurs. The guidance is effective for annual periods beginning after December 15, 2017, and is applicable to the Company in fiscal 2019. Early adoption is permitted as of the beginning of an annual reporting period. The Company is currently evaluating the impact of the adoption of ASU 2016-16 on its consolidated financial position and results of operations. In August 2016, the FASB issued ASU No. 2016-15, Statement of Cash Flow (Topic 230) . The guidance reduces diversity in how certain cash receipts and cash payments are presented and classified in the Statements of Cash Flows. Certain of ASU 2016-15 requirements are as follows: 1) cash payments for debt prepayment or debt extinguishment costs should be classified as cash outflows for financing activities, 2) contingent consideration payments made soon after a business combination should be classified as cash outflows for investing activities and cash payment made thereafter should be classified as cash outflows for financing up to the amount of the contingent consideration liability recognized at the acquisition date with any excess classified as operating activities, 3) cash proceeds from the settlement of insurance claims should be classified on the basis of the nature of the loss, 4) cash proceeds from the settlement of Corporate-Owned Life Insurance (COLI) Policies should be classified as cash inflows from investing activities and cash payments for premiums on COLI policies may be classified as cash outflows for investing activities, operating activities, or a combination of investing and operating activities, and 5) cash paid to a tax authority by an employer when withholding shares from an employee's award for tax-withholding purposes should be classified as cash outflows for financing activities. The guidance is effective for annual periods beginning after December 15, 2017, and is applicable to the Company in fiscal 2019. Early adoption is permitted. The adoption of ASU 2016-15 is not expected to have a material effect on the Company's consolidated financial statements. In June 2016, the FASB issued ASU No. 2016-13, Financial Instruments - Credit Losses (Topic 326) . The guidance requires that financial assets measured at amortized cost be presented at the net amount expected to be collected. The allowance for credit losses is a valuation account that is deducted from the amortized cost basis. The income statement reflects the measurement of credit losses for newly recognized financial assets, as well as the expected credit losses during the period. The measurement of expected credit losses is based upon historical experience, current conditions, and reasonable and supportable forecasts that affect the collectability of the reported amount. Credit losses relating to available-for-sale debt securities will be recorded through an allowance for credit losses rather than as a direct write-down to the security. The updated guidance is effective for annual periods beginning after December 15, 2019, and is applicable to the Company in fiscal 2021. Early adoption is permitted. The Company is currently evaluating the impact of the adoption of ASU 2016-13 on its consolidated financial position and results of operations. In February 2016, the FASB issued ASU No. 2016-02, Leases (Topic 842). The guidance requires an entity to recognize a right-of-use asset and a lease liability for virtually all of its leases with terms of more than 12 months. Recognition, measurement and presentation of expenses will depend on classification as a finance or operating lease. The amendments also require certain quantitative and qualitative disclosures about leasing arrangements. The guidance is effective for annual periods beginning after December 15, 2018, and is applicable to the Company in fiscal 2020. Early adoption is permitted. The updated guidance requires a modified retrospective adoption. The Company is currently evaluating the anticipated impact of the adoption of ASU 2016-02 on its consolidated financial position and results of operations. In January 2016, the FASB issued ASU No. 2016-01, Financial Instruments - Overall (Subtopic 825-10): Recognition and Measurement of Financial Assets and Financial Liabilities . This guidance changes how entities measure equity investments that do not result in consolidation and are not accounted for under the equity method. Entities will be required to measure these investments at fair value at the end of each reporting period and recognize changes in fair value in net income. A practicability exception will be available for equity investments that do not have readily determinable fair values, however; the exception requires the Company to consider relevant transactions that can be reasonably known to identify any observable price changes that would impact the fair value . This guidance also changes certain disclosure requirements and other aspects of current U.S. GAAP. This guidance is effective for annual periods beginning after December 15, 2017, and is applicable to the Company in fiscal 2019 . Early adoption is permitted. The Company is currently evaluating the anticipated impact of the adoption of ASU 2016-01 on its consolidated financial position and results of operations. In May 2014, the FASB issued ASU No. 2014-09, Revenue from Contracts with Customers (Topic 606) , which provides guidance for revenue recognition. This ASU is applicable to any entity that either enters into contracts with customers to transfer goods or services or enters into contracts for the transfer of nonfinancial assets. ASU 2014-09 will supersede the revenue recognition requirements in Topic 605, Revenue Recognition , and most industry-specific guidance. The standard’s core principle is that a company will recognize revenue when it transfers promised goods or services to customers in an amount that reflects the consideration to which the company expects to be entitled to receive in exchange for those goods or services. In doing so, companies will need to use more judgment and make more estimates than under current U.S. GAAP. These judgments may include identifying performance obligations in the contract, estimating the amount of variable consideration to include in the transaction price and allocating the transaction price to each separate performance obligation. ASU 2014-09 is effective prospectively for fiscal years, and interim reporting periods within those years, beginning after December 15, 2017, which is fiscal 2019 for the Company. The Company will adopt Topic 606 effective September 30, 2018 and has established a cross-functional team to evaluate and implement the new revenue recognition rules. The Company will adopt Topic 606 using the modified retrospective method but has not finalized evaluating the anticipated impact of the adoption of ASU 2014-09 on its consolidated financial position and results of operations.

Fair Value Measurements (Tables

Fair Value Measurements (Tables)	3 Months Ended
	Dec. 30, 2017
Fair Value Disclosures [Abstract]
Fair Value Assets and Liabilities Measured on Recurring Basis	Assets and liabilities measured and recorded at fair value on a recurring basis consisted of the following at December 30, 2017 : Fair Value at Reporting Date Using Balance as of December 30, 2017 Quoted Prices in Active Market for Identical Assets (Level 1) Significant Other Observable Inputs (Level 2) Significant Unobservable Inputs (Level 3) Assets: Interest rate cap - derivative 5.3 — 5.3 — Forward foreign currency contracts 0.4 — 0.4 — Total $ 5.7 $ — $ 5.7 $ — Liabilities: Deferred compensation liabilities $ 49.7 $ 49.7 $ — $ — Forward foreign currency contracts 2.6 — 2.6 — Total $ 52.3 $ 49.7 $ 2.6 $ —
Estimated Fair Values of Convertible Notes	The estimated fair values of the Company’s Convertible Notes at December 30, 2017 were as follows: 2042 Notes 284.8 2043 Notes 0.3 $ 285.1

Business Combinations (Tables)

Business Combinations (Tables)	3 Months Ended
	Dec. 30, 2017
Business Combinations [Abstract]
Purchase Price Allocation	The total purchase price was allocated to Cynosure’s preliminary tangible and identifiable intangible assets and liabilities based on the estimated fair values of those assets as of March 22, 2017, as set forth below. The preliminary purchase price allocation is as follows: Cash $ 107.2 Marketable securities 82.9 Accounts receivable 40.2 Inventory 121.1 Property, plant and equipment 44.1 Other assets and liabilities, net 12.2 Accounts payable and accrued expenses (75.3 ) Deferred revenue (11.2 ) Capital lease obligation (25.2 ) Identifiable intangible assets: Developed technology 736.0 In-process research and development 107.0 Distribution agreement 42.0 Customer relationships 35.0 Trade names 74.0 Deferred income taxes, net (315.7 ) Goodwill 683.5 Purchase Price $ 1,657.8
Pro Forma Information	The following unaudited pro forma information presents the combined financial results for the Company and Cynosure as if the acquisition of Cynosure had been completed at the beginning of the prior fiscal year, September 26, 2015 (fiscal 2016): Three Months Ended December 31, 2016 (unaudited) Revenue $ 856.3 Net income $ 74.1 Basic earnings per common share $ 0.27 Diluted earnings per common share $ 0.26

Restructuring Charges (Tables)

Restructuring Charges (Tables)	3 Months Ended
	Dec. 30, 2017
Restructuring and Related Activities [Abstract]
Charges Taken Related to Restructuring Actions	The following table displays charges related to these actions recorded in the fiscal 2018 year to date period ( three months ended December 30, 2017 ) and fiscal 2017 (the year ended September 30, 2017) and a rollforward of the accrued balances from September 30, 2017 to December 30, 2017 : Fiscal 2018 Actions Fiscal 2017 Actions Fiscal 2016 Actions Total Restructuring Charges Fiscal 2017 charges: Workforce reductions $ — $ 8.5 $ — $ 8.5 Facility closure costs — — 4.8 4.8 Fiscal 2017 restructuring charges $ — $ 8.5 $ 4.8 $ 13.3 Fiscal 2018 charges: Workforce reductions $ 3.8 $ — $ — $ 3.8 Fiscal 2018 restructuring charges $ 3.8 $ — $ — $ 3.8
Charges Taken Related to Accrued Restructuring Actions	Fiscal 2018 Actions Fiscal 2017 Actions Fiscal 2016 Actions Other Total Rollforward of Accrued Restructuring Balance as of September 30, 2017 $ — $ 7.5 $ 3.7 $ 0.3 $ 11.5 Fiscal 2018 charges 3.8 — — — 3.8 Stock-based compensation (1.3 ) — — — (1.3 ) Severance payments and adjustments (0.9 ) (2.3 ) (0.2 ) — (3.4 ) Other payments — — (0.3 ) (0.1 ) (0.4 ) Balance as of December 30, 2017 $ 1.6 $ 5.2 $ 3.2 $ 0.2 $ 10.2

Borrowings and Credit Arrange29

Borrowings and Credit Arrangements (Tables)	3 Months Ended
	Dec. 30, 2017
Debt Disclosure [Abstract]
Company's Borrowings	The Company’s borrowings consisted of the following: December 30, September 30, Current debt obligations, net of debt discount and deferred issuance costs: Term Loan $ 46.7 $ 121.3 Revolver 120.0 345.0 Securitization Program 200.0 200.0 Convertible Notes 205.4 484.5 Total current debt obligations $ 572.1 $ 1,150.8 Long-term debt obligations, net of debt discount and deferred issuance costs: Term Loan 1,430.1 1,190.5 2022 Senior Notes 982.6 981.6 2025 Senior Notes 345.0 — Total long-term debt obligations $ 2,757.7 $ 2,172.1 Total debt obligations $ 3,329.8 $ 3,322.9
Interest Expense under Convertible Notes	Interest expense under the Convertible Notes was as follows: Three Months Ended December 30, December 31, Amortization of debt discount $ 2.9 $ 5.2 Amortization of deferred financing costs 0.1 0.2 Principal accretion 1.6 4.6 Non-cash interest expense 4.6 10.0 2.00% accrued interest (cash) 1.1 2.0 $ 5.7 $ 12.0

Derivatives Schedule of Derivat

Derivatives Schedule of Derivative Assets at Fair Value (Tables)	3 Months Ended
	Dec. 30, 2017
Derivative Instruments and Hedging Activities Disclosure [Abstract]
Schedule of Derivative Assets at Fair Value	The table below presents the fair value of the Company's derivative financial instruments as well as their classification on the balance sheet as of December 30, 2017 : Balance Sheet Location December 30, 2017 September 30, 2017 Assets: Derivative instruments designated as a cash flow hedge: Interest rate cap agreements Prepaid expenses and other current assets $ 5.3 $ 3.6 Interest rate cap agreements Other assets — 1.2 $ 5.3 $ 4.8 Derivatives not designated as hedging instruments: Forward foreign currency contracts Prepaid expenses and other current assets $ 0.4 $ 0.4 Liabilities: Derivatives not designated as hedging instruments: Forward foreign currency contracts Accrued expenses $ 2.6 $ 4.0
Schedule of Unrealized Loss Recognized in AOCI	The following table presents the unrealized gain recognized in AOCI related to the interest rate caps for the following reporting periods: Three Months Ended December 30, 2017 December 31, 2016 Amount of gain (loss) recognized in other comprehensive income, net of taxes: Interest rate cap agreements $ (4.3 ) $ 0.7
Schedule of Adjustment to Fair Value within the Consolidated Statements of Income	The following table presents the adjustment to fair value (realized and unrealized) recorded within the Consolidated Statements of Income for derivative instruments for which the Company did not elect hedge accounting: Derivatives not classified as hedging instruments Amount of Gain (Loss) Recognized in Income Location of Gain (Loss) Recognized in Income Three Months Ended December 30, 2017 Three Months Ended December 31, 2016 Forward foreign currency contracts $ 1.2 $ 9.6 Other income, net

Net Income Per Share (Tables)

Net Income Per Share (Tables)	3 Months Ended
	Dec. 30, 2017
Earnings Per Share [Abstract]
Reconciliation of Basic and Diluted Share Amounts	A reconciliation of basic and diluted share amounts is as follows: Three Months Ended December 30, December 31, Basic weighted average common shares outstanding 276,856 278,663 Weighted average common stock equivalents from assumed exercise of stock options and stock units 2,212 3,143 Incremental shares from Convertible Notes premium 1,734 2,418 Diluted weighted average common shares outstanding 280,802 284,224 Weighted-average anti-dilutive shares related to: Outstanding stock options 2,272 1,442 Stock units 216 13

Stock-Based Compensation (Table

Stock-Based Compensation (Tables)	3 Months Ended
	Dec. 30, 2017
Disclosure of Compensation Related Costs, Share-based Payments [Abstract]
Stock-Based Compensation Expense in Consolidated Statements of Operations	The following presents stock-based compensation expense in the Company’s Consolidated Statements of Income: Three Months Ended December 30, December 31, Cost of revenues $ 2.2 $ 2.8 Research and development 2.5 2.8 Selling and marketing 2.9 2.7 General and administrative 7.5 10.9 Restructuring 1.3 — $ 16.4 $ 19.2
Weighted-Average Assumptions Utilized to Value Stock Options	The Company uses a binomial model to determine the fair value of its stock options. The weighted-average assumptions utilized to value these stock options are indicated in the following table: Three Months Ended December 30, December 31, Risk-free interest rate 2.1 % 1.8 % Expected volatility 35.3 % 36.6 % Expected life (in years) 4.7 4.7 Dividend yield — — Weighted average fair value of options granted $ 13.00 $ 12.18

Other Balance Sheet Informati33

Other Balance Sheet Information (Tables)	3 Months Ended
	Dec. 30, 2017
Balance Sheet Related Disclosures [Abstract]
Other Balance Sheet Information of Inventories	December 30, September 30, Inventories Raw materials $ 114.2 $ 95.7 Work-in-process 44.6 45.0 Finished goods 199.4 190.9 $ 358.2 $ 331.6
Other Balance Sheet Information of Property, Plant and Equipment	Property, plant and equipment Equipment $ 363.7 $ 357.9 Equipment under customer usage agreements 379.0 368.7 Building and improvements 172.7 172.0 Leasehold improvements 61.1 60.6 Land 46.4 46.3 Furniture and fixtures 21.0 20.8 1,043.9 1,026.3 Less – accumulated depreciation and amortization (576.8 ) (553.5 ) $ 467.1 $ 472.8

Business Segments and Geograp34

Business Segments and Geographic Information (Tables)	3 Months Ended
	Dec. 30, 2017
Segment Reporting [Abstract]
Segment Information	Segment information is as follows: Three Months Ended December 30, December 31, Total revenues: Diagnostics $ 284.6 $ 325.4 Breast Health 288.0 273.3 Medical Aesthetics 91.3 — GYN Surgical 107.5 114.8 Skeletal Health 19.7 20.9 $ 791.1 $ 734.4 Income (loss) from operations: Diagnostics $ 36.5 $ 41.1 Breast Health 89.7 85.2 Medical Aesthetics (23.0 ) — GYN Surgical 30.2 25.5 Skeletal Health 0.7 (5.8 ) $ 134.1 $ 146.0 Depreciation and amortization: Diagnostics $ 64.7 $ 84.9 Breast Health 4.9 5.1 Medical Aesthetics 28.5 — GYN Surgical 22.9 25.1 Skeletal Health 0.2 0.2 $ 121.2 $ 115.3 Capital expenditures: Diagnostics $ 11.9 $ 10.3 Breast Health 3.5 2.2 Medical Aesthetics 1.6 — GYN Surgical 2.4 4.1 Skeletal Health 0.7 0.3 Corporate 1.7 7.8 $ 21.8 $ 24.7 December 30, September 30, Identifiable assets: Diagnostics $ 2,583.0 $ 2,621.6 Breast Health 840.5 824.0 Medical Aesthetics 1,723.9 1,751.2 GYN Surgical 1,477.8 1,494.6 Skeletal Health 26.8 25.5 Corporate 1,396.3 1,262.7 $ 8,048.3 $ 7,979.6
Revenues by Geography	Revenues by geography as a percentage of total revenues were as follows: Three Months Ended December 30, December 31, United States 75.5 % 77.9 % Europe 11.5 % 10.7 % Asia-Pacific 8.7 % 8.4 % Rest of World 4.3 % 3.0 % 100.0 % 100.0 %

Intangible Assets and Goodwill

Intangible Assets and Goodwill (Tables)	3 Months Ended
	Dec. 30, 2017
Goodwill and Intangible Assets Disclosure [Abstract]
Schedule of Intangible Assets	Intangible assets consisted of the following: Description As of December 30, 2017 As of September 30, 2017 Gross Carrying Value Accumulated Amortization Gross Carrying Value Accumulated Amortization Acquired intangible assets: Developed technology $ 4,528.8 $ 2,266.7 $ 4,528.7 $ 2,186.8 In-process research and development 46.0 — 46.0 — Customer relationships 556.7 402.8 552.8 393.8 Trade names 310.3 161.1 310.3 156.4 Distribution agreement 42.0 4.1 42.0 2.8 Non-competition agreements 1.5 0.1 1.5 0.1 Business licenses 2.5 2.2 2.4 2.2 Total acquired intangible assets $ 5,487.8 $ 2,837.0 $ 5,483.7 $ 2,742.1 Internal-use software 65.8 48.2 64.5 46.1 Capitalized software embedded in products 15.5 2.6 14.3 2.0 Total intangible assets $ 5,569.1 $ 2,887.8 $ 5,562.5 $ 2,790.2
Schedule of Estimated Amortization Expense	The estimated remaining amortization expense of the Company's acquired intangible assets as of December 30, 2017 for each of the five succeeding fiscal years is as follows: Remainder of Fiscal 2018 $ 283.1 Fiscal 2019 $ 366.0 Fiscal 2020 $ 354.8 Fiscal 2021 $ 333.2 Fiscal 2022 $ 320.3

Product Warranties (Tables)

Product Warranties (Tables)	3 Months Ended
	Dec. 30, 2017
Guarantees [Abstract]
Product Warranty Activity	Product warranty activity was as follows: Balance at Beginning of Period Provisions Settlements/ Adjustments Balance at End of Period Three Months Ended: December 30, 2017 $ 17.0 $ 4.3 $ (5.1 ) $ 16.2 December 31, 2016 $ 5.0 $ 2.6 $ (1.7 ) $ 5.9

Accumulated Other Comprehensi37

Accumulated Other Comprehensive Loss (Tables)	3 Months Ended
	Dec. 30, 2017
Accumulated Other Comprehensive Income [Abstract]
Changes in Accumulated Other Comprehensive Income	The following tables summarize the changes in accumulated balances of other comprehensive loss for the periods presented: Three Months Ended December 30, 2017 Foreign Currency Translation Marketable Securities Pension Plans Hedged Interest Rate Caps Total Beginning Balance $ (18.5 ) $ (0.4 ) $ (1.6 ) $ 4.3 $ (16.2 ) Other comprehensive income (loss) before reclassifications 5.5 — 0.6 (4.3 ) 1.8 Amounts reclassified to statement of income — 0.4 — 2.3 2.7 Ending Balance $ (13.0 ) $ — $ (1.0 ) $ 2.3 $ (11.7 ) Three Months Ended December 31, 2016 Foreign Currency Translation Marketable Securities Pension Plans Hedged Interest Rate Caps Total Beginning Balance $ (26.1 ) $ (0.3 ) $ (2.5 ) $ (3.4 ) $ (32.3 ) Other comprehensive income (loss) before reclassifications (15.7 ) 2.3 — 0.7 (12.7 ) Amounts reclassified to statement of income — 0.1 — 2.1 2.2 Ending Balance $ (41.8 ) $ 2.1 $ (2.5 ) $ (0.6 ) $ (42.8 )

Basis of Presentation (Details)

Basis of Presentation (Details) - USD ($) $ in Millions	Jan. 29, 2018	Jan. 19, 2018	Dec. 30, 2017	Sep. 30, 2017
Subsequent Event [Line Items]
Internal-use software			$ 17.6	$ 18.4
Capitalized Computer Software, Net			$ 12.9	$ 12.3
Subsequent Event Type [Member]
Subsequent Event [Line Items]
Senior Notes		$ 1,000
2025 Senior Notes
Subsequent Event [Line Items]
Debt Instrument, Interest Rate During Period			4.375%
2025 Senior Notes | Subsequent Event Type [Member]
Subsequent Event [Line Items]
Senior Notes		$ 600
Offering Price of Principal Amount		100.00%
2028 Senior Notes
Subsequent Event [Line Items]
Debt Instrument, Interest Rate During Period			4.625%
2028 Senior Notes | Subsequent Event Type [Member]
Subsequent Event [Line Items]
Senior Notes		$ 400
Offering Price of Principal Amount		100.00%
Stated interest rate		4.625%
2022 Notes
Subsequent Event [Line Items]
Debt Instrument, Interest Rate During Period			5.25%
2022 Notes | Subsequent Event Type [Member]
Subsequent Event [Line Items]
Senior Notes		$ 1,000
2042 Notes
Subsequent Event [Line Items]
Senior Notes			$ 39.3
2042 Notes | Subsequent Event Type [Member]
Subsequent Event [Line Items]
Stated interest rate	2.00%
Redemption price (as a percent)	100.00%	100.00%

Fair Value Measurements - Fair

Fair Value Measurements - Fair Value Assets and Liabilities Measured on Recurring Basis (Detail) - USD ($) $ in Millions	Dec. 30, 2017	Sep. 30, 2017
Assets:
Assets measured at fair value on a recurring basis	$ 5.7
Interest Rate Cash Flow Hedge Asset at Fair Value		$ 4.8
Liabilities:
Liabilities measured at fair value on a recurring basis	52.3
Foreign Exchange Contract [Member]
Assets:
Foreign Currency Contract, Asset, Fair Value Disclosure	0.4
Deferred compensation liabilities
Liabilities:
Liabilities measured at fair value on a recurring basis	49.7
Quoted Prices in Active Market for Identical Assets (Level 1)
Assets:
Assets measured at fair value on a recurring basis	0
Liabilities:
Liabilities measured at fair value on a recurring basis	49.7
Quoted Prices in Active Market for Identical Assets (Level 1) | Interest rate cap - derivative
Assets:
Assets measured at fair value on a recurring basis	0
Interest Rate Cash Flow Hedge Asset at Fair Value	5.3
Quoted Prices in Active Market for Identical Assets (Level 1) | Foreign Exchange Contract [Member]
Assets:
Assets measured at fair value on a recurring basis	0
Quoted Prices in Active Market for Identical Assets (Level 1) | Deferred compensation liabilities
Liabilities:
Liabilities measured at fair value on a recurring basis	49.7
Quoted Prices in Active Market for Identical Assets (Level 1) | Forward Contracts [Member]
Liabilities:
Foreign Currency Contracts, Liability, Fair Value Disclosure	0
Significant Other Observable Inputs (Level 2)
Assets:
Assets measured at fair value on a recurring basis	5.7
Liabilities:
Liabilities measured at fair value on a recurring basis	2.6
Significant Other Observable Inputs (Level 2) | Interest rate cap - derivative
Assets:
Assets measured at fair value on a recurring basis	5.3
Significant Other Observable Inputs (Level 2) | Foreign Exchange Contract [Member]
Assets:
Assets measured at fair value on a recurring basis	0.4
Significant Other Observable Inputs (Level 2) | Deferred compensation liabilities
Liabilities:
Liabilities measured at fair value on a recurring basis	0
Significant Other Observable Inputs (Level 2) | Forward Contracts [Member]
Liabilities:
Foreign Currency Contracts, Liability, Fair Value Disclosure	2.6
Significant Unobservable Inputs (Level 3)
Assets:
Assets measured at fair value on a recurring basis	0
Liabilities:
Liabilities measured at fair value on a recurring basis	0
Significant Unobservable Inputs (Level 3) | Interest rate cap - derivative
Assets:
Assets measured at fair value on a recurring basis	0
Significant Unobservable Inputs (Level 3) | Foreign Exchange Contract [Member]
Assets:
Assets measured at fair value on a recurring basis	0
Significant Unobservable Inputs (Level 3) | Deferred compensation liabilities
Liabilities:
Liabilities measured at fair value on a recurring basis	0
Significant Unobservable Inputs (Level 3) | Forward Contracts [Member]
Liabilities:
Foreign Currency Contracts, Liability, Fair Value Disclosure	$ 0

Fair Value Measurements - Addit

Fair Value Measurements - Additional Information (Detail) $ in Millions	Dec. 30, 2017USD ($)
Fair Value, Off-balance Sheet Risks, Disclosure Information [Line Items]
Borrowed principal	$ 1,000
Credit Agreement
Fair Value, Off-balance Sheet Risks, Disclosure Information [Line Items]
Borrowed principal	1,600
Accounts Receivable Securitization [Member]
Fair Value, Off-balance Sheet Risks, Disclosure Information [Line Items]
Borrowed principal	200
2022 Senior Notes
Fair Value, Off-balance Sheet Risks, Disclosure Information [Line Items]
Fair value of debt instrument	1,100
2025 Senior Notes
Fair Value, Off-balance Sheet Risks, Disclosure Information [Line Items]
Fair value of debt instrument	$ 358.6

Fair Value Measurements - Estim

Fair Value Measurements - Estimated Fair Values of Convertible Notes (Detail) $ in Millions	Dec. 30, 2017USD ($)
Estimated Fair Value Of Financial Instruments [Line Items]
Estimated fair values of debt instruments	$ 285.1
2042 Notes
Estimated Fair Value Of Financial Instruments [Line Items]
Estimated fair values of debt instruments	284.8
2043 Notes
Estimated Fair Value Of Financial Instruments [Line Items]
Estimated fair values of debt instruments	$ 0.3

Business Combination - Narrativ

Business Combination - Narrative (Details) $ / shares in Units, $ in Millions	Dec. 11, 2017USD ($)	Apr. 07, 2017USD ($)	Mar. 22, 2017USD ($)project$ / shares	Dec. 30, 2017USD ($)	Jul. 01, 2017USD ($)	Dec. 31, 2016USD ($)	Sep. 30, 2017USD ($)project
Business Acquisition [Line Items]
Gross Carrying Value				$ 5,569.1			$ 5,562.5
Revenues				791.1		$ 734.4
Operating Income (Loss)				134.1		$ 146
Goodwill				3,176.7			3,171.2
Cynosure
Business Acquisition [Line Items]
Purchase price (in dollars per share) | $ / shares			$ 66
Transaction costs			$ 18.8
Revenues					$ 207.5
Operating Income (Loss)					96.4
Goodwill			683.5		$ 683.5
Property, plant and equipment			44.1
Medicor Medical Supply
Business Acquisition [Line Items]
Cash paid		$ 19
Intangible Assets		$ 5.4
Weighted average period		7 years 8 months 12 days
Purchase price withheld		$ 1.9
Period for payment of contingent consideration liabilities		2 years
Goodwill		$ 8.9
Property, plant and equipment		$ 4.7
Emsor
Business Acquisition [Line Items]
Intangible Assets	$ 2.8
Purchase price withheld	$ 0.5			2
Period for payment of contingent consideration liabilities	18 months
Period of cumulative revenue to trigger payment of contingent consideration liability	2 years
Goodwill				3.5
Property, plant and equipment				6.8
Business Combination, Consideration Transferred	$ 13.1
In-process research and development
Business Acquisition [Line Items]
Gross Carrying Value				46			$ 46
In-process research and development | Cynosure
Business Acquisition [Line Items]
Intangible Assets			$ 107
Number of projects | project			3				2
Estimated costs to complete			$ 18
Developed technology | Cynosure
Business Acquisition [Line Items]
Intangible Assets			$ 736
Estimated costs to complete							$ 4
Gross Carrying Value							61
Weighted average period			11 years 9 months 18 days
Distribution agreement
Business Acquisition [Line Items]
Gross Carrying Value				42			42
Distribution agreement | Cynosure
Business Acquisition [Line Items]
Intangible Assets			$ 42
Weighted average period			8 years
Customer relationships | Cynosure
Business Acquisition [Line Items]
Intangible Assets			$ 35
Weighted average period			7 years 8 months 12 days
Trade names
Business Acquisition [Line Items]
Gross Carrying Value				$ 310.3			$ 310.3
Trade names | Cynosure
Business Acquisition [Line Items]
Intangible Assets			$ 74
Weighted average period			8 years 10 months 24 days
Minimum | Other Intangible Assets | Cynosure
Business Acquisition [Line Items]
Discount rate (as a percent)			11.00%
Minimum | In-process research and development | Cynosure
Business Acquisition [Line Items]
Discount rate (as a percent)			14.00%
Maximum | Other Intangible Assets | Cynosure
Business Acquisition [Line Items]
Discount rate (as a percent)			12.00%
Maximum | In-process research and development | Cynosure
Business Acquisition [Line Items]
Discount rate (as a percent)			22.00%
Cynosure Shareholders | Cynosure
Business Acquisition [Line Items]
Cash paid			$ 1,660

Business Combination - Purchase

Business Combination - Purchase Price Consideration (Details) - Medicor Medical Supply $ in Millions	Apr. 07, 2017USD ($)
Business Acquisition [Line Items]
Acquisition Price Adjustment	$ 2
Purchase price withheld	1.9
Cash paid	$ 19

Business Combination - Purcha44

Business Combination - Purchase Price Allocation (Details) - USD ($) $ in Millions	Dec. 30, 2017	Sep. 30, 2017	Jul. 01, 2017	Mar. 22, 2017
Purchase Price Allocation [Line Items]
Goodwill	$ 3,176.7	$ 3,171.2
Cynosure
Purchase Price Allocation [Line Items]
Cash				$ 107.2
Marketable securities				82.9
Accounts receivable				40.2
Inventory				121.1
Property, plant and equipment				44.1
Other assets and liabilities, net				12.2
Accounts payable and accrued expenses				(75.3)
Deferred revenue				(11.2)
Capital lease obligation				(25.2)
Deferred income taxes, net				(315.7)
Goodwill			$ 683.5	683.5
Purchase Price				1,657.8
Cynosure | Developed technology
Purchase Price Allocation [Line Items]
Intangible Assets				736
Cynosure | In-process research and development
Purchase Price Allocation [Line Items]
Intangible Assets				107
Cynosure | Distribution agreement
Purchase Price Allocation [Line Items]
Intangible Assets				42
Cynosure | Customer relationships
Purchase Price Allocation [Line Items]
Intangible Assets				35
Cynosure | Trade names
Purchase Price Allocation [Line Items]
Intangible Assets				$ 74

Business Combination - Pro Form

Business Combination - Pro Forma Information (Details) - Cynosure $ / shares in Units, $ in Millions	3 Months Ended
	Dec. 30, 2017USD ($)$ / shares
Business Acquisition [Line Items]
Revenue | $	$ 856.3
Net income | $	$ 74.1
Basic earnings per common share (in dollars per share) | $ / shares	$ 270
Diluted earnings per common share (in dollars per share) | $ / shares	$ 260

Restructuring Charges - Charges

Restructuring Charges - Charges Taken Related to Restructuring Actions (Detail) - USD ($) $ in Millions	3 Months Ended			12 Months Ended
	Dec. 30, 2017	Jul. 01, 2017	Dec. 31, 2016	Sep. 30, 2017
Bedford [Member]
Restructuring Cost and Reserve [Line Items]
Facility closure costs		$ 1.3	$ 3.5
Restructuring | Two Thousand Seventeen [Member]
Restructuring Cost and Reserve [Line Items]
Workforce reductions				$ 8.5
Facility closure costs				4.8
Fiscal restructuring charges				13.3
Restructuring | Two thousand eighteen [Member]
Restructuring Cost and Reserve [Line Items]
Workforce reductions	$ 3.8
Fiscal restructuring charges	3.8
Restructuring | Fiscal 2018 Action [Member] | Two Thousand Seventeen [Member]
Restructuring Cost and Reserve [Line Items]
Workforce reductions				0
Facility closure costs				0
Fiscal restructuring charges				0
Restructuring | Fiscal 2018 Action [Member] | Two thousand eighteen [Member]
Restructuring Cost and Reserve [Line Items]
Workforce reductions	3.8
Fiscal restructuring charges	3.8
Restructuring | Fiscal 2017 Actions [Member] | Two Thousand Seventeen [Member]
Restructuring Cost and Reserve [Line Items]
Workforce reductions				8.5
Facility closure costs				0
Fiscal restructuring charges				8.5
Restructuring | Fiscal 2017 Actions [Member] | Two thousand eighteen [Member]
Restructuring Cost and Reserve [Line Items]
Workforce reductions	0
Fiscal restructuring charges	0
Restructuring | Fiscal 2016 Actions | Two Thousand Seventeen [Member]
Restructuring Cost and Reserve [Line Items]
Workforce reductions				0
Facility closure costs				4.8
Fiscal restructuring charges				$ 4.8
Restructuring | Fiscal 2016 Actions | Two thousand eighteen [Member]
Restructuring Cost and Reserve [Line Items]
Workforce reductions	0
Fiscal restructuring charges	$ 0

Restructuring Charges - Charg47

Restructuring Charges - Charges Taken Related to Accrued Restructuring Actions (Detail) $ in Millions	3 Months Ended
	Dec. 30, 2017USD ($)
Restructuring Reserve [Roll Forward]
Stock-based compensation	$ (1.3)
Restructuring | Two Thousand Seventeen [Member]
Restructuring Reserve [Roll Forward]
Period beginning balance	11.5
Restructuring | Two Thousand Seventeen [Member] | Fiscal 2018 Action [Member]
Restructuring Reserve [Roll Forward]
Period beginning balance	0
Restructuring | Two Thousand Seventeen [Member] | Fiscal 2017 Actions [Member]
Restructuring Reserve [Roll Forward]
Period beginning balance	7.5
Restructuring | Two Thousand Seventeen [Member] | Fiscal 2016 Actions
Restructuring Reserve [Roll Forward]
Period beginning balance	3.7
Restructuring | Two Thousand Seventeen [Member] | Other Restructuring [Member]
Restructuring Reserve [Roll Forward]
Period beginning balance	0.3
Restructuring | Two thousand eighteen [Member]
Restructuring Reserve [Roll Forward]
Fiscal 2018 charges	3.8
Severance payments and adjustments	(3.4)
Other payments	(0.4)
Period end balance	10.2
Restructuring | Two thousand eighteen [Member] | Fiscal 2018 Action [Member]
Restructuring Reserve [Roll Forward]
Fiscal 2018 charges	3.8
Stock-based compensation	(1.3)
Severance payments and adjustments	(0.9)
Other payments	0
Period end balance	1.6
Restructuring | Two thousand eighteen [Member] | Fiscal 2017 Actions [Member]
Restructuring Reserve [Roll Forward]
Fiscal 2018 charges	0
Stock-based compensation	0
Severance payments and adjustments	(2.3)
Other payments	0
Period end balance	5.2
Restructuring | Two thousand eighteen [Member] | Fiscal 2016 Actions
Restructuring Reserve [Roll Forward]
Fiscal 2018 charges	0
Stock-based compensation	0
Severance payments and adjustments	(0.2)
Other payments	(0.3)
Period end balance	3.2
Restructuring | Two thousand eighteen [Member] | Other Restructuring [Member]
Restructuring Reserve [Roll Forward]
Fiscal 2018 charges	0
Stock-based compensation	0
Severance payments and adjustments	0
Other payments	(0.1)
Period end balance	$ 0.2

Restructuring Charges - Additio

Restructuring Charges - Additional Information (Detail) - USD ($) $ in Millions	3 Months Ended
	Dec. 30, 2017	Sep. 30, 2017	Jul. 01, 2017	Apr. 01, 2017	Dec. 31, 2016
Restructuring Cost and Reserve [Line Items]
Severance charges	$ 3.8
Share-based Compensation Arrangement by Share-based Payment Award, Plan Modification, Incremental Compensation Cost	$ 1.3
Cynosure
Restructuring Cost and Reserve [Line Items]
Severance charges		$ 1.3	$ 4.3	$ 1.5
Bedford [Member]
Restructuring Cost and Reserve [Line Items]
Facility closure costs			$ 1.3		$ 3.5

Borrowings and Credit Arrange49

Borrowings and Credit Arrangements - Company's Borrowings (Detail) $ in Millions	3 Months Ended
	Dec. 30, 2017USD ($)	Sep. 30, 2017USD ($)
Debt Instrument [Line Items]
Current portion of long-term debt	$ 572.1	$ 1,150.8
Convertible Notes	205.4	484.5
Total long-term debt obligations	2,757.7	2,172.1
Total debt obligations	$ 3,329.8	3,322.9
Amended Credit Agreement [Member]
Debt Instrument [Line Items]
Debt Instrument, Number of Fiscal Quarters Ending on Measurement Date	4
Term Loan [Member]
Debt Instrument [Line Items]
Current portion of long-term debt	$ 46.7	121.3
Long term debt obligations. excluding convertible notes	1,430.1	1,190.5
Revolver [Member]
Debt Instrument [Line Items]
Current portion of long-term debt	120	345
Accounts Receivable Securitization [Member]
Debt Instrument [Line Items]
Current portion of long-term debt	200	200
2022 Notes
Debt Instrument [Line Items]
Long term debt obligations. excluding convertible notes	982.6	981.6
2025 Senior Notes
Debt Instrument [Line Items]
Long term debt obligations. excluding convertible notes	$ 345	$ 0

Borrowings and Credit Arrange50

Borrowings and Credit Arrangements - Additional Information (Detail)	Jan. 29, 2018USD ($)	Jan. 19, 2018USD ($)	Dec. 29, 2017USD ($)$ / shares	Oct. 10, 2017USD ($)	Dec. 30, 2017USD ($)$ / shares	Dec. 31, 2016USD ($)	Jun. 25, 2016USD ($)	Oct. 03, 2017USD ($)	Sep. 30, 2017USD ($)	Dec. 19, 2016
Debt Instrument [Line Items]
Current portion of long-term debt					$ 572,100,000				$ 1,150,800,000
Non-cash interest expense amortization of debt discount and deferred financing costs					8,700,000	$ 14,300,000
Debt extinguishment loss					1,000,000	0
Payments of Debt Issuance Costs					11,900,000	0
Cash paid for conversion of debt					296,900,000	$ 6,400,000
Adjustments to Additional Paid in Capital, Equity Component of Convertible Debt					13,400,000
Deferred Taxes, Reacquisition of Equity Component					3,800,000
Principal Amount Of Borrowings					1,000,000,000
Share Price | $ / shares			$ 42.75
Subsequent Event Type [Member]
Debt Instrument [Line Items]
Senior Notes		$ 1,000,000,000
Senior Notes		1,000,000,000
Amended Term Loan [Member]
Debt Instrument [Line Items]
Proceeds from Issuance of Debt					$ 1,800,000,000
Amended Term Loan [Member] | Percentage Added to Eurodollar Rate [Member]
Debt Instrument [Line Items]
Debt Instrument, Basis Spread on Variable Rate					1.50%
Amended Revolver [Member]
Debt Instrument [Line Items]
Line of Credit Facility, Maximum Borrowing Capacity								$ 1,500,000,000
Line of Credit, Current								345,000,000
Amended Revolver [Member] | Percentage Added to Eurodollar Rate [Member]
Debt Instrument [Line Items]
Debt Instrument, Basis Spread on Variable Rate					1.50%
Amended Credit Agreement [Member]
Debt Instrument [Line Items]
Leverage Ratio Maximum					5
Decreased Net Leverage Ratio Pursuant To Senior Secured Credit Facility					4.50
Interest Coverage Ratio					3.75
Debt extinguishment loss					$ 1,000,000
Maximum Range of Present Value of Cash Flow Percentage					10.00%
Direct Third Party Costs interest Expense					$ 1,700,000
Payments of Debt Issuance Costs					4,900,000
2043 Notes [Member]
Debt Instrument [Line Items]
Senior Notes					300,000
Cash paid for conversion of debt					244,100,000
Debt Instrument, Repurchase Amount					$ 201,700,000
2028 Senior Notes
Debt Instrument [Line Items]
Senior note interest rate per year					4.625%
2028 Senior Notes | Subsequent Event Type [Member]
Debt Instrument [Line Items]
Senior Notes		$ 400,000,000
Stated interest rate		4.625%
Offering Price of Principal Amount		100.00%
2042 Notes
Debt Instrument [Line Items]
Senior Notes					$ 39,300,000
Cash paid for conversion of debt					$ 52,800,000
2042 Notes | Subsequent Event Type [Member]
Debt Instrument [Line Items]
Stated interest rate	2.00%
Redemption price (as a percent)	100.00%	100.00%
Debt Instrument, Repurchase Amount	$ 206,000,000
Two Thousand And Twelve Notes [Member]
Debt Instrument [Line Items]
Debt Instrument, Convertible, Conversion Price | $ / shares					$ 31.175
Credit Agreement
Debt Instrument [Line Items]
Repayments of Secured Debt					$ 1,320,000,000
Weighted average interest rates					2.75%	2.05%
Interest rate					3.069%
Interest expense					$ 12,400,000		$ 9,800,000
Non-cash interest expense amortization of debt discount and deferred financing costs					700,000		$ 1,100,000
Principal Amount Of Borrowings					1,600,000,000
2025 Senior Notes
Debt Instrument [Line Items]
Interest expense					3,500,000
Non-cash interest expense amortization of debt discount and deferred financing costs					$ 100,000
Senior note interest rate per year					4.375%
2025 Senior Notes | Subsequent Event Type [Member]
Debt Instrument [Line Items]
Senior Notes		$ 600,000,000
Offering Price of Principal Amount		100.00%
2022 Notes
Debt Instrument [Line Items]
Interest expense					$ 14,000,000
Non-cash interest expense amortization of debt discount and deferred financing costs					$ 1,000,000
Senior note interest rate per year					5.25%
2022 Notes | Subsequent Event Type [Member]
Debt Instrument [Line Items]
Senior Notes		$ 1,000,000,000
Senior Notes		1,000,000,000
2022 Senior Notes
Debt Instrument [Line Items]
Interest expense					$ 15,100,000
Accounts Receivable Securitization [Member]
Debt Instrument [Line Items]
Principal Amount Of Borrowings					$ 200,000,000
2028 Senior Notes
Debt Instrument [Line Items]
Stated interest rate					4.625%
2028 Senior Notes | Subsequent Event Type [Member]
Debt Instrument [Line Items]
Senior Notes		$ 400,000,000
Stated interest rate		4.625%
Offering Price of Principal Amount		100.00%
Redemption price (as a percent)		100.00%
Secured Term Loan [Member] | Amended Term Loan [Member]
Debt Instrument [Line Items]
Line of Credit Facility, Maximum Borrowing Capacity								$ 1,500,000,000
2025 Senior Notes | Subsequent Event Type [Member]
Debt Instrument [Line Items]
Senior Notes		$ 600,000,000
Offering Price of Principal Amount		100.00%
Principal Amount Of Borrowings		$ 600,000,000
Revolver [Member]
Debt Instrument [Line Items]
Current portion of long-term debt					$ 120,000,000				345,000,000
2022 Senior Notes | 2028 Senior Notes | Subsequent Event Type [Member]
Debt Instrument [Line Items]
Debt Instrument, Redemption Price, Percentage of Principal Amount Redeemed		35.00%
Debt Instrument Percentage Of Redemption Price Second Period		104.625%
Debt Instrument Percentage Of Redemption Price Third Period		102.312%
Debt Instrument Percentage Of Redemption Price Fourth Period		101.541%
Debt Instrument Percentage Of Redemption Price Fifth Period		100.77%
Percentage Price of Principal Amount for Repurchase of Senior Notes		101.00%
Debt Instrument Percentage Redemption Price Sixth Period		100.00%
2022 Senior Notes | 2025 Senior Notes
Debt Instrument [Line Items]
Senior Notes				$ 350,000,000
Stated interest rate				4.375%
Offering Price of Principal Amount				100.00%
Redemption price (as a percent)					35.00%
Debt Instrument Percentage Of Redemption Price Second Period				104.375%
Debt Instrument Percentage Of Redemption Price Third Period				102.188%
Debt Instrument Percentage Of Redemption Price Fourth Period				101.094%
Debt Instrument Percentage Of Redemption Price Fifth Period				100.00%
Percentage Price of Principal Amount for Repurchase of Senior Notes				101.00%
2022 Senior Notes | 2025 Senior Notes | Subsequent Event Type [Member]
Debt Instrument [Line Items]
Stated interest rate		4.375%
Convertible Debt [Member] | 2042 Notes
Debt Instrument [Line Items]
Cash Per Original Principal Amount of Exchange Notes			$ 1,371
Principal Convertible To Common Stock			1,000
Debt Instrument, Convertible, If-converted Value in Excess of Principal			$ 282,600,000
Convertible Debt [Member] | 2042 Notes | Subsequent Event Type [Member]
Debt Instrument [Line Items]
Stated interest rate	2.00%
Convertible Debt [Member] | Two Thousand And Twelve Notes [Member]
Debt Instrument [Line Items]
Stated interest rate										2.00%
Convertible Notes Payable [Member]
Debt Instrument [Line Items]
Interest expense					$ 5,700,000	$ 12,000,000
Non-cash interest expense amortization of debt discount and deferred financing costs					4,600,000	$ 10,000,000
Accounts Receivable Securitization [Member]
Debt Instrument [Line Items]
Current portion of long-term debt					200,000,000				$ 200,000,000
Amended Term Loan [Member] | Amended Credit Agreement [Member] | Minimum
Debt Instrument [Line Items]
Debt Instrument, Periodic Payment, Principal					$ 9,375,000
Debt Instrument, Periodic Payment, Principal, Period					3 months
Amended Term Loan [Member] | Amended Credit Agreement [Member] | Maximum
Debt Instrument [Line Items]
Debt Instrument, Periodic Payment, Principal					$ 37,500,000

Borrowings and Credit Arrange51

Borrowings and Credit Arrangements - Interest Expense under Convertible Notes (Detail) - USD ($) $ in Millions	3 Months Ended
	Dec. 30, 2017	Dec. 31, 2016
Debt Conversion [Line Items]
Non-cash interest expense	$ 8.7	$ 14.3
Cash accrued interest percentage	2.00%	2.00%
Convertible Notes Payable
Debt Conversion [Line Items]
Amortization of debt discount	$ 2.9	$ 5.2
Amortization of deferred financing costs	0.1	0.2
Principal accretion	1.6	4.6
Non-cash interest expense	4.6	10
2.00% accrued interest (cash)	1.1	2
Interest expense, net	$ 5.7	$ 12

Derivatives Additional Informat

Derivatives Additional Information (Details) - USD ($) $ in Millions	3 Months Ended		12 Months Ended
	Dec. 30, 2017	Dec. 31, 2016	Sep. 30, 2017	Sep. 26, 2015
Derivative Instruments and Hedging Activities Disclosure [Abstract]
Interest Rate Cap Agreements Aggregate Premium Payable			$ 1.9	$ 13.2
Principal Amount Of Borrowings	$ 1,000
Loss reclassified from accumulated other comprehensive loss to the statement of income	(2.3)	$ (2.1)
Derivative Instruments, Gain (Loss) Reclassification from Accumulated OCI to Income, Estimated Net Amount to be Transferred	1.9
Interest Rate Cash Flow Hedge Asset at Fair Value			$ 4.8
Gain (Loss) on Foreign Currency Derivative Instruments Not Designated as Hedging Instruments	0.2	1.2
Unrealized Gain (Loss) on Foreign Currency Derivatives, Net, before Tax	1.5	$ 8.4
Notional Amount	$ 157.4

Derivatives Fair Value of Deriv

Derivatives Fair Value of Derivative Financial Instruments (Details) - USD ($) $ in Millions	Dec. 30, 2017	Sep. 30, 2017
Designated as Hedging Instrument [Member] | Interest rate cap - derivative
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Cash Flow Hedge Derivative Instrument Assets at Fair Value	$ 5.3	$ 4.8
Designated as Hedging Instrument [Member] | Interest rate cap - derivative | Prepaid Expenses and Other Current Assets [Member]
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Cash Flow Hedge Derivative Instrument Assets at Fair Value	5.3	3.6
Designated as Hedging Instrument [Member] | Interest rate cap - derivative | Other Assets [Member]
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Cash Flow Hedge Derivative Instrument Assets at Fair Value	0	1.2
Not Designated as Hedging Instrument [Member] | Foreign Exchange Forward [Member] | Prepaid Expenses and Other Current Assets [Member]
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Cash Flow Hedge Derivative Instrument Assets at Fair Value	0.4	0.4
Not Designated as Hedging Instrument [Member] | Foreign Exchange Forward [Member] | Accrued Liabilities [Member]
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Cash Flow Hedge Derivative Instrument Assets at Fair Value	$ 2.6	$ 4

Derivatives Schedule of Cash Fl

Derivatives Schedule of Cash Flow Hedges Included in Accumulated Other Comprehensive Income (Details) - USD ($) $ in Millions	3 Months Ended
	Dec. 30, 2017	Dec. 31, 2016
Derivative Instruments, Gain (Loss) [Line Items]
Changes in value of hedged interest rate caps, net of tax of $(4.9) and $0.5 for the three months ended December 30, 2017 and December 31, 2016:	$ (4.3)	$ 0.7
Interest rate cap - derivative
Derivative Instruments, Gain (Loss) [Line Items]
Changes in value of hedged interest rate caps, net of tax of $(4.9) and $0.5 for the three months ended December 30, 2017 and December 31, 2016:		$ 0.7

Derivatives Gain (Loss) on Fair

Derivatives Gain (Loss) on Fair Value Hedges Recognized in Earnings (Details) - USD ($) $ in Millions	3 Months Ended
	Dec. 30, 2017	Dec. 31, 2016
Foreign Exchange Forward [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Forward foreign currency contracts	$ 1.2	$ 9.6

Commitments and Contingencies -

Commitments and Contingencies - Additional Information (Detail) - USD ($) $ in Millions	3 Months Ended
	Apr. 01, 2017	Dec. 31, 2016	Sep. 04, 2012
Commitments and Contingencies Disclosure [Abstract]
Assessed damages			$ 4
Payment of settlement compensation	$ 8.5
Litigation Settlement, Expense		$ 9.2

Net Income Per Share - Reconcil

Net Income Per Share - Reconciliation of Basic and Diluted Share Amounts (Detail) - shares shares in Thousands	3 Months Ended
	Dec. 30, 2017	Dec. 31, 2016
Earnings Per Share [Line Items]
Basic weighted average common shares outstanding	276,856	278,663
Weighted average common stock equivalents from assumed exercise of stock options and stock units	2,212	3,143
Incremental shares from Convertible Notes premium	1,734	2,418
Diluted weighted average common shares outstanding	280,802	284,224
Outstanding Stock Options
Weighted-average anti-dilutive shares related to:
Weighted-average anti-dilutive shares (in shares)	2,272	1,442
Restricted stock units
Weighted-average anti-dilutive shares related to:
Weighted-average anti-dilutive shares (in shares)	216	13

Stock-Based Compensation - Stoc

Stock-Based Compensation - Stock-Based Compensation Expense in Consolidated Statements of Operations (Detail) - USD ($) $ in Millions	3 Months Ended
	Dec. 30, 2017	Dec. 31, 2016
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock-based compensation expense	$ 16.4	$ 19.2
Cost of Sales [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock-based compensation expense	2.2	2.8
Research and development
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock-based compensation expense	2.5	2.8
Selling and marketing
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock-based compensation expense	2.9	2.7
General and administrative
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock-based compensation expense	7.5	10.9
Restructuring
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock-based compensation expense	$ 1.3	$ 0

Stock-Based Compensation - Addi

Stock-Based Compensation - Additional Information (Detail) - USD ($) $ / shares in Units, shares in Millions, $ in Millions	3 Months Ended
	Dec. 30, 2017	Dec. 31, 2016
Stock option plans
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Options granted	1.6	0.9
Weighted-average exercise prices	$ 40.82	$ 37.62
Share-based compensation, stock option outstanding	6.7
Weighted-average exercise price of options outstanding	$ 31.20
Unrecognized compensation expense	$ 37
Weighted-average period for recognition of unrecognized stock-based compensation, years	3 years 1 month 22 days
Restricted stock units
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares granted	0.8	0.9
Restricted stock units (RSUs), weighted average grant date fair values	$ 40.79	$ 37.58
Unvested RSUs outstanding	2
Unvested RSUs weighted-average grant date fair value	$ 37.72
Unrecognized compensation expense	$ 98.4
Weighted-average period for recognition of unrecognized stock-based compensation, years	2 years 1 month 22 days
Performance shares
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares granted	0.4	0.1
Restricted stock units (RSUs), weighted average grant date fair values	$ 40.86	$ 37.64
Market Based Awards
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares granted	0.3	0.1
Restricted stock units (RSUs), weighted average grant date fair values	$ 49.45	$ 48.90
Minimum eligible percentage to receive target number of shares of company's common stock	0.00%
Maximum eligible percentage to receive target number of shares of company's common stock	200.00%
Performance stock units vesting period	3 years

Stock-Based Compensation - Weig

Stock-Based Compensation - Weighted-Average Assumptions Utilized to Value Stock Options (Detail) - USD ($)	3 Months Ended
	Dec. 30, 2017	Dec. 31, 2016
Disclosure of Compensation Related Costs, Share-based Payments [Abstract]
Risk-free interest rate	2.10%	1.80%
Expected volatility	35.30%	36.60%
Expected life (in years)	4 years 8 months 8 days	4 years 8 months 8 days
Dividend yield	$ 0	$ 0
Weighted average fair value of options granted	$ 13	$ 12.18

Disposition (Details)

Disposition (Details) - Blood Screening Business [Member] - USD ($) $ in Millions	Dec. 14, 2016	Dec. 30, 2017	Apr. 01, 2017	Dec. 31, 2016	Sep. 30, 2017
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Gross proceeds on sale	$ 1,850
Proceeds from sale of business			$ 1,865
Gain on sale of business			$ 899.7
Accrued Income Taxes					$ 649.5
Proceeds allocated to manufacture of inventory					$ 13.1
Disposal Group, Including Discontinued Operation, Revenue		$ 12.6		$ 65.2
Disposal Group, Including Discontinued Operation, Operating Income (Loss)				$ 28.6
Grifols [Member] | Minimum
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Disposal Group, Including Discontinued Operations, Period to Provide Transition Services After Disposal			2 years
Grifols [Member] | Maximum
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Disposal Group, Including Discontinued Operations, Period to Provide Transition Services After Disposal			3 years

Other Balance Sheet Informati62

Other Balance Sheet Information - Other Balance Sheet Information of Inventories (Detail) - USD ($) $ in Millions	Dec. 30, 2017	Sep. 30, 2017
Balance Sheet Related Disclosures [Abstract]
Raw materials	$ 114.2	$ 95.7
Work-in-process	44.6	45
Finished goods	199.4	190.9
Inventories	$ 358.2	$ 331.6

Other Balance Sheet Informati63

Other Balance Sheet Information - Other Balance Sheet Information of Property, Plant and Equipment (Detail) - USD ($) $ in Millions	Dec. 30, 2017	Sep. 30, 2017
Balance Sheet Related Disclosures [Abstract]
Equipment	$ 363.7	$ 357.9
Equipment under customer usage agreements	379	368.7
Building and improvements	172.7	172
Leasehold improvements	61.1	60.6
Land	46.4	46.3
Furniture and fixtures	21	20.8
Property, plant and equipment, gross	1,043.9	1,026.3
Less – accumulated depreciation and amortization	(576.8)	(553.5)
Property, plant and equipment, net	$ 467.1	$ 472.8

Business Segments and Geograp64

Business Segments and Geographic Information - Additional Information (Detail)	3 Months Ended
	Dec. 30, 2017USD ($)SegmentCustomer	Dec. 31, 2016USD ($)
Segment Reporting Disclosure [Line Items]
Number of operating segments | Segment	5
Number of reportable segments | Segment	5
Revenues | $	$ 791,100,000	$ 734,400,000
Customer represented greater than 10% of consolidated revenues	0	0
Countries with greater than 10% of consolidated revenue | Customer	0
Intersegment
Segment Reporting Disclosure [Line Items]
Revenues | $	$ 0	$ 0

Business Segments and Geograp65

Business Segments and Geographic Information - Segment Information (Detail) - USD ($) $ in Millions	3 Months Ended
	Dec. 30, 2017	Dec. 31, 2016	Sep. 30, 2017
Segment Reporting Information [Line Items]
Total revenues	$ 791.1	$ 734.4
Operating income (loss)	134.1	146
Depreciation and amortization	121.2	115.3
Capital expenditures	21.8	24.7
Identifiable assets	8,048.3		$ 7,979.6
Diagnostics
Segment Reporting Information [Line Items]
Total revenues	284.6	325.4
Operating income (loss)	36.5	41.1
Depreciation and amortization	64.7	84.9
Capital expenditures	11.9	10.3
Identifiable assets	2,583		2,621.6
Breast Health
Segment Reporting Information [Line Items]
Total revenues	288	273.3
Operating income (loss)	89.7	85.2
Depreciation and amortization	4.9	5.1
Capital expenditures	3.5	2.2
Identifiable assets	840.5		824
GYN Surgical
Segment Reporting Information [Line Items]
Total revenues	107.5	114.8
Operating income (loss)	30.2	25.5
Depreciation and amortization	22.9	25.1
Capital expenditures	2.4	4.1
Identifiable assets	1,477.8		1,494.6
Skeletal Health
Segment Reporting Information [Line Items]
Total revenues	19.7	20.9
Operating income (loss)	0.7	(5.8)
Depreciation and amortization	0.2	0.2
Capital expenditures	0.7	0.3
Identifiable assets	26.8		25.5
Medical Aesthetics
Segment Reporting Information [Line Items]
Total revenues	91.3	0
Operating income (loss)	(23)	0
Depreciation and amortization	28.5	0
Capital expenditures	1.6	0
Identifiable assets	1,723.9		1,751.2
Corporate
Segment Reporting Information [Line Items]
Capital expenditures	1.7	$ 7.8
Identifiable assets	$ 1,396.3		$ 1,262.7

Business Segments and Geograp66

Business Segments and Geographic Information - Revenues by Geography (Detail)	3 Months Ended
	Dec. 30, 2017	Dec. 31, 2016
Schedule Of Geographical Segments [Line Items]
Revenues	100.00%	100.00%
United States
Schedule Of Geographical Segments [Line Items]
Revenues	75.50%	77.90%
Europe
Schedule Of Geographical Segments [Line Items]
Revenues	11.50%	10.70%
Asia-Pacific
Schedule Of Geographical Segments [Line Items]
Revenues	8.70%	8.40%
Rest of World
Schedule Of Geographical Segments [Line Items]
Revenues	4.30%	3.00%

Income Taxes (Details)

Income Taxes (Details) - USD ($) $ in Millions	3 Months Ended		12 Months Ended
	Dec. 30, 2017	Dec. 31, 2016	Sep. 30, 2018	Oct. 01, 2018	Jan. 31, 2018
Income Tax Examination [Line Items]
Company's effective tax rate	(324.50%)	25.50%
Income tax benefit for remeasurements of deferred tax deferred tax liability as result of change in tax rate	$ 355.2
Charge for transition taxes related to the deemed repatriation of foreign earnings	26
Estimated net benefit effect of existing deferred tax balances and transition tax due to change in tax rate	329.2
Provisional net benefit amount recorded for remeasurements of deferred tax balance due to change in rate	355.2
State and Local Jurisdiction [Member] | Selling, General and Administrative Expenses [Member]
Income Tax Examination [Line Items]
Reversal of selling and administrative expense due to settlement of state tax audit	$ 4
Subsequent Event Type [Member] | State and Local Jurisdiction [Member]
Income Tax Examination [Line Items]
Settlement liability of state tax audit					$ 11
Scenario, Forecast [Member]
Income Tax Examination [Line Items]
Blended statutory income tax rate			24.50%
Projected tax rate at which deferred tax assets and liabilities positions will reverse			24.50%	21.00%

Intangible Assets and Goodwil68

Intangible Assets and Goodwill - Schedule of Intangible Assets (Detail) - USD ($) $ in Millions	Dec. 30, 2017	Sep. 30, 2017
Finite-Lived Intangible Assets [Line Items]
Gross Carrying Value	$ 5,569.1	$ 5,562.5
Accumulated Amortization	2,887.8	2,790.2
Developed technology
Finite-Lived Intangible Assets [Line Items]
Gross Carrying Value	4,528.8	4,528.7
Accumulated Amortization	2,266.7	2,186.8
In-process research and development
Finite-Lived Intangible Assets [Line Items]
Gross Carrying Value	46	46
Accumulated Amortization	0	0
Customer relationships
Finite-Lived Intangible Assets [Line Items]
Gross Carrying Value	556.7	552.8
Accumulated Amortization	402.8	393.8
Trade names
Finite-Lived Intangible Assets [Line Items]
Gross Carrying Value	310.3	310.3
Accumulated Amortization	161.1	156.4
Distribution agreement
Finite-Lived Intangible Assets [Line Items]
Gross Carrying Value	42	42
Accumulated Amortization	4.1	2.8
Non-competition agreements
Finite-Lived Intangible Assets [Line Items]
Gross Carrying Value	1.5	1.5
Accumulated Amortization	0.1	0.1
Business licenses
Finite-Lived Intangible Assets [Line Items]
Gross Carrying Value	2.5	2.4
Accumulated Amortization	2.2	2.2
Acquired intangible assets [Member]
Finite-Lived Intangible Assets [Line Items]
Gross Carrying Value	5,487.8	5,483.7
Accumulated Amortization	2,837	2,742.1
Internal-use software [Member]
Finite-Lived Intangible Assets [Line Items]
Gross Carrying Value	65.8	64.5
Accumulated Amortization	48.2	46.1
Capitalized software [Member]
Finite-Lived Intangible Assets [Line Items]
Gross Carrying Value	15.5	14.3
Accumulated Amortization	$ 2.6	$ 2

Intangible Assets and Goodwil69

Intangible Assets and Goodwill - Schedule of Estimated Amortization Expense (Detail) $ in Millions	Dec. 30, 2017USD ($)
Goodwill and Intangible Assets Disclosure [Abstract]
Remainder of Fiscal 2018	$ 283.1
Fiscal 2,019	366
Fiscal 2,020	354.8
Fiscal 2,021	333.2
Fiscal 2,022	$ 320.3

Intangible Assets and Goodwil70

Intangible Assets and Goodwill Additional Information (Details) $ in Millions	3 Months Ended
	Dec. 30, 2017USD ($)unit	Sep. 30, 2017USD ($)	Jul. 01, 2017USD ($)	Mar. 22, 2017USD ($)
Product Line [Line Items]
Goodwill	$ 3,176.7	$ 3,171.2
Cynosure
Product Line [Line Items]
Reporting Unit, Percentage of Fair Value in Excess of Carrying Amount			2.00%
Goodwill			$ 683.5	$ 683.5
Medical Aesthetics
Product Line [Line Items]
Number of reporting units | unit	1

Product Warranties - Product Wa

Product Warranties - Product Warranty Activity (Detail) - USD ($) $ in Millions	3 Months Ended
	Dec. 30, 2017	Dec. 31, 2016
Movement in Standard and Extended Product Warranty, Increase (Decrease) [Roll Forward]
Balance at Beginning of Period	$ 17	$ 5
Provisions	4.3	2.6
Settlements/ Adjustments	(5.1)	(1.7)
Balance at End of Period	$ 16.2	$ 5.9

Accumulated Other Comprehensi72

Accumulated Other Comprehensive Income (Detail) - USD ($) $ in Millions	3 Months Ended
	Dec. 30, 2017	Dec. 31, 2016	Sep. 30, 2017	Sep. 24, 2016
Accumulated Other Comprehensive Income (Loss) [Line Items]
Marketable Securities, Unrealized Gain (Loss)		$ 4
Changes in foreign currency translation adjustment	$ 5.5	(15.7)
Changes in unrealized holding gains and losses on available-for-sale securities, net of tax of $0.2 and $1.5 for the three months December 30, 2017 and December 31, 2016:	0	2.3
Other Comprehensive (Income) Loss, Defined Benefit Plan, after Tax and Reclassification Adjustment, Attributable to Parent	0.6	0
Changes in value of hedged interest rate caps, net of tax of $(4.9) and $0.5 for the three months ended December 30, 2017 and December 31, 2016:	(4.3)	0.7
Accumulated other comprehensive loss	(11.7)		$ (16.2)
Accumulated Foreign Currency Adjustment Attributable to Parent [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Changes in foreign currency translation adjustment	5.5	(15.7)
Restructuring Reserve, Translation and Other Adjustment	0	0
Accumulated Other Comprehensive Income (Loss), Foreign Currency Translation Adjustment, Net of Tax	(13)	(41.8)	(18.5)	$ (26.1)
Accumulated Net Investment Gain (Loss) Attributable to Parent [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Accumulated Other Comprehensive Income (Loss), Available-for-sale Securities Adjustment, Net of Tax	0	2.1	(0.4)	(0.3)
Changes in unrealized holding gains and losses on available-for-sale securities, net of tax of $0.2 and $1.5 for the three months December 30, 2017 and December 31, 2016:	0	2.3
Restructuring Reserve, Translation and Other Adjustment	0.4	0.1
Accumulated Defined Benefit Plans Adjustment Attributable to Parent [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Accumulated Other Comprehensive (Income) Loss, Defined Benefit Plan, after Tax	(1)	(2.5)	(1.6)	(2.5)
Other Comprehensive (Income) Loss, Defined Benefit Plan, after Tax and Reclassification Adjustment, Attributable to Parent	0.6
Restructuring Reserve, Translation and Other Adjustment	0	0
Accumulated Net Gain (Loss) from Cash Flow Hedges Attributable to Parent [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Accumulated other comprehensive Income loss Hedge	2.3	(0.6)	4.3	(3.4)
Changes in value of hedged interest rate caps, net of tax of $(4.9) and $0.5 for the three months ended December 30, 2017 and December 31, 2016:	(4.3)	0.7
Restructuring Reserve, Translation and Other Adjustment	2.3	2.1
AOCI Attributable to Parent [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Other Comprehensive Income (Loss) before Reclassifications, Tax	1.8	(12.7)
Restructuring Reserve, Translation and Other Adjustment	2.7	2.2
Accumulated other comprehensive loss	$ (11.7)	$ (42.8)	$ (16.2)	$ (32.3)