Hologic (HOLX) 10-K 20 Nov 18 2018 FY Annual report Financial data

Document and Entity Information

Document and Entity Information - USD ($)	12 Months Ended
	Sep. 29, 2018	Nov. 15, 2018	Mar. 31, 2018
Document And Entity Information [Abstract]
Document Type	10-K
Amendment Flag	false
Document Period End Date	Sep. 29, 2018
Document Fiscal Year Focus	2,018
Document Fiscal Period Focus	FY
Entity Registrant Name	HOLOGIC INC
Entity Central Index Key	859,737
Current Fiscal Year End Date	--09-29
Entity Filer Category	Large Accelerated Filer
Entity Common Stock, Shares Outstanding		289,212,857
Entity Well-known Seasoned Issuer	Yes
Entity Voluntary Filers	No
Entity Current Reporting Status	Yes
Entity Public Float			$ 10,174,623,483

Consolidated Statements of Inco

Consolidated Statements of Income - USD ($) shares in Thousands, $ in Millions	12 Months Ended
	Sep. 29, 2018	Sep. 30, 2017	Sep. 24, 2016
Revenues:
Product	$ 2,643.9	$ 2,538	$ 2,379
Service and other	574	520.8	453.7
Revenues	3,217.9	3,058.8	2,832.7
Costs of revenues:
Product	886.6	881.8	756.8
Service and other	315.2	258.9	219.2
Gross Profit	1,696.7	1,621	1,563.3
Operating expenses:
Research and development	218.7	232.8	232.1
Selling and marketing	544.6	498.6	415.1
General and administrative	366.1	343.3	267.3
Cost of Goods Sold, Amortization	59.3	62.5	89.7
Amortization of intangible assets	319.4	297.1	293.4
Impairment of Intangible Assets, Indefinite-lived (Excluding Goodwill)	46	0	0
Goodwill impairment charge	685.7	0	0
Gain on sale of business	0	(899.7)	0
Restructuring charges	14.2	13.3	10.5
Operating expenses	1,934.6	250.8	1,014.7
(Loss) income from operations	(237.9)	1,370.2	548.6
Interest income	6.3	3.8	0.7
Interest expense	(148.7)	(153.2)	(155.3)
Debt extinguishment losses	(45.9)	(3.2)	(5.3)
Other income, net	7.6	12.9	26.6
(Loss) income before income taxes	(418.6)	1,230.5	415.3
(Benefit) provision for income taxes	(307.3)	475	84.5
Net (loss) income	$ (111.3)	$ 755.5	$ 330.8
Net (loss) income per common share:
Basic (in dollars per share)	$ (0.40)	$ 2.70	$ 1.18
Diluted (in dollars per share)	$ (0.40)	$ 2.64	$ 1.16
Weighted average number of shares outstanding:
Basic (in shares)	275,105	279,811	280,213
Diluted (in shares)	275,105	285,653	286,156

Consolidated Statements of Comp

Consolidated Statements of Comprehensive Income - USD ($) $ in Millions	12 Months Ended
	Sep. 29, 2018	Sep. 30, 2017	Sep. 24, 2016
Net (loss) income	$ (111.3)	$ 755.5	$ 330.8
Changes in foreign currency translation adjustment	(8.1)	7.6	(10.4)
Loss recognized in accumulated other comprehensive (loss) income	0	2.3	(1.1)
Loss (gain) reclassified from accumulated other comprehensive (loss) income to the statement of operations	0.4	(2.4)	(6.1)
Changes in pension plans, net of taxes of ($0.6) in 2018, $1.1 in 2017, and $0.3 in 2016	0.5	0.9	(0.7)
(Gain) loss recognized in other comprehensive (loss) income, net	(5.7)	0.8	(3.4)
Loss reclassified from accumulated other comprehensive loss to the statement of operations, net	3.6	6.9	3.9
Other comprehensive (loss) income	(9.3)	16.1	(17.8)
Comprehensive (loss) income	(120.6)	771.6	313
Accumulated Deficit [Member]
Net (loss) income	$ (111.3)	$ 755.5	$ 330.8

Consolidated Statements of Co_2

Consolidated Statements of Comprehensive Income (Parenthetical) - USD ($) $ in Millions	12 Months Ended
	Sep. 29, 2018	Sep. 30, 2017	Sep. 24, 2016
Statement of Comprehensive Income [Abstract]
Changes in unrealized holding gains and losses on available-for-sale securities, tax	$ 0.2	$ 0.1
Changes in pension plans, taxes	(0.6)	1.1	$ 0.3
Changes in value of hedged interest rate caps, tax	$ (5)	$ 0.6	$ 2

Consolidated Balance Sheets

Consolidated Balance Sheets - USD ($) $ in Millions	Sep. 29, 2018	Sep. 30, 2017
Current assets:
Cash and cash equivalents	$ 666.7	$ 540.6
Accounts receivable, less reserves of $16.2 and $9.8, respectively	579.2	533.5
Inventories	384.1	331.6
Prepaid income taxes	31.7	22.4
Prepaid expenses and other current assets	61.5	50.5
Total current assets	1,723.2	1,478.6
Property, plant and equipment, net	478.2	472.8
Intangible assets, net	2,398.6	2,772.3
Goodwill	2,533.2	3,171.2
Other assets	97.7	84.7
Total assets	7,230.9	7,979.6
Current liabilities:
Current portion of long-term debt	599.7	1,150.8
Accounts payable	192.2	166.6
Accrued expenses	436.1	375.3
Deferred revenue	172.9	171.2
Current portion of capital lease obligations	1.7	1.6
Total current liabilities	1,402.6	1,865.5
Long-term debt, net of current portion	2,704.6	2,172.1
Capital lease obligations, net of current portion	20.9	22.7
Deferred income tax liabilities	498.2	973.6
Deferred revenue	18.2	20.8
Other long-term liabilities	157.6	140.2
Commitments and contingencies (Note 11)
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; 289,900 and 287,853 shares issued, respectively	2.9	2.9
Additional paid-in-capital	5,671.3	5,630.8
Accumulated deficit	(2,494)	(2,382.7)
Treasury stock, at cost – 19,812 and 12,560 shares, respectively	(725.9)	(450.1)
Accumulated other comprehensive loss	(25.5)	(16.2)
Total stockholders’ equity	2,428.8	2,784.7
Total liabilities and stockholders’ equity	$ 7,230.9	$ 7,979.6

Consolidated Balance Sheets (Pa

Consolidated Balance Sheets (Parenthetical) - USD ($) $ in Millions	Sep. 29, 2018	Sep. 30, 2017
Statement of Financial Position [Abstract]
Accounts receivable, reserves	$ 16.2	$ 9.8
Preferred stock, par value (in dollars per share)	$ 0.01	$ 0.01
Preferred stock, shares authorized	1,623,000	1,623,000
Preferred stock, shares issued	0	0
Common stock, par value (in dollars per share)	$ 0.01	$ 0.01
Common stock, shares authorized	750,000,000	750,000,000
Common stock, shares issued	289,900,000	287,853,000
Treasury stock, shares	19,812,000	12,560,000

Consolidated Statements of Stoc

Consolidated Statements of Stockholders' Equity - USD ($) shares in Thousands, $ in Millions	Total	Common Stock [Member]	Additional Paid-in-Capital [Member]	Accumulated Deficit [Member]	Accumulated Other Comprehensive Income [Member]	Treasury Stock [Member]
Balance (in shares) at Sep. 26, 2015		282,495				0
Balance at Sep. 26, 2015	$ 2,079.2	$ 2.8	$ 5,559.9	$ (3,469)	$ (14.5)	$ 0
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Exercise of stock options (in shares)		1,233
Exercise of stock options	24.1	$ 0.1	24
Vesting of restricted stock units, net of shares withheld for employee taxes (in shares)		820
Vesting of restricted stock units, net of shares withheld for employee taxes	(16.4)		(16.4)
Common stock issued under the employee stock purchase plan (in shares)		467
Common stock issued under the employee stock purchase plan	14.4		14.4
Stock-based compensation expense	62.3		62.3
Repurchase of common stock (in shares)						7,289
Repurchase of common stock	(250)					$ (250)
Excess tax benefit from equity awards	10.5		10.5
Reacquisition of equity component from convertible notes repurchase, net of taxes	(94.4)		(94.4)
Net (loss) income	330.8			330.8
Foreign currency translation adjustment	(10.4)				(10.4)
Adjustment to minimum pension liability, net	(0.7)				(0.7)
Unrealized losses on derivatives, net of taxes	(3.4)				(3.4)
Unrealized losses on marketable securities	(1.1)				(1.1)
Interest cost of interest rate cap reclassified to statement of operations	3.9				3.9
Net realized gains on marketable securities reclassified out of accumulated other comprehensive loss	(6.1)				(6.1)
Balance (in shares) at Sep. 24, 2016		285,015				7,289
Balance at Sep. 24, 2016	2,142.7	$ 2.9	5,560.3	(3,138.2)	(32.3)	$ (250)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Exercise of stock options (in shares)		1,427
Exercise of stock options	33.1		33.1
Vesting of restricted stock units, net of shares withheld for employee taxes (in shares)		939
Vesting of restricted stock units, net of shares withheld for employee taxes	(19.7)		(19.7)
Common stock issued under the employee stock purchase plan (in shares)		472
Common stock issued under the employee stock purchase plan	15		15
Stock-based compensation expense	68.2		68.2
Repurchase of common stock (in shares)						5,271
Repurchase of common stock	(200.1)					$ (200.1)
Reclassification of liability award to equity	7.8		7.8
Reacquisition of equity component from convertible notes repurchase, net of taxes	(33.9)		(33.9)
Net (loss) income	755.5			755.5
Foreign currency translation adjustment	7.6				7.6
Adjustment to minimum pension liability, net	0.9				0.9
Unrealized losses on derivatives, net of taxes	0.8				0.8
Unrealized losses on marketable securities	2.3				2.3
Interest cost of interest rate cap reclassified to statement of operations	6.9				6.9
Net realized gains on marketable securities reclassified out of accumulated other comprehensive loss	(2.4)				(2.4)
Balance (in shares) at Sep. 30, 2017		287,853				12,560
Balance at Sep. 30, 2017	$ 2,784.7	$ 2.9	5,630.8	(2,382.7)	(16.2)	$ (450.1)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Exercise of stock options (in shares)	800	795
Exercise of stock options	$ 17.3	$ 0	17.3
Vesting of restricted stock units, net of shares withheld for employee taxes (in shares)		804
Vesting of restricted stock units, net of shares withheld for employee taxes	(16.7)		(16.7)
Common stock issued under the employee stock purchase plan (in shares)		448
Common stock issued under the employee stock purchase plan	15.6		15.6
Stock-based compensation expense	65		65
Repurchase of common stock (in shares)						7,252
Repurchase of common stock	(275.8)					$ (275.8)
Reacquisition of equity component from convertible notes repurchase, net of taxes	(40.7)		(40.7)
Net (loss) income	(111.3)			(111.3)
Foreign currency translation adjustment	(8.1)				(8.1)
Adjustment to minimum pension liability, net	0.5				0.5
Unrealized losses on derivatives, net of taxes	(5.7)				(5.7)
Unrealized losses on marketable securities	0
Interest cost of interest rate cap reclassified to statement of operations	3.6				3.6
Net realized gains on marketable securities reclassified out of accumulated other comprehensive loss	0.4				0.4
Balance (in shares) at Sep. 29, 2018		289,900				19,812
Balance at Sep. 29, 2018	$ 2,428.8	$ 2.9	$ 5,671.3	$ (2,494)	$ (25.5)	$ (725.9)

Consolidated Statements of Cash

Consolidated Statements of Cash Flows - USD ($) $ in Millions	12 Months Ended
	Sep. 29, 2018	Sep. 30, 2017	Sep. 24, 2016
OPERATING ACTIVITIES
Net (loss) income	$ (111.3)	$ 755.5	$ 330.8
Adjustments to reconcile net (loss) income to net cash provided by operating activities:
Depreciation	101.6	89.6	82.3
Amortization	378.7	359.6	383.1
Non-cash interest expense	15	49.4	52.1
Stock-based compensation expense	65	68.2	65.4
Deferred income taxes and other non-cash taxes	(477.3)	(357.2)	(155.8)
Goodwill impairment charge	685.7	0	0
Impairment of Intangible Assets, Indefinite-lived (Excluding Goodwill)	46	0	0
Fair value write-up of inventory sold	1.1	39.7	0
Debt extinguishment losses	45.9	3.2	5.3
Gain on sale of business	0	(899.7)	0
Gain on sale of investments	0	(5.6)	(25.1)
Other adjustments and non-cash items	8.7	8.8	3.7
Changes in operating assets and liabilities, excluding the effect of acquisitions and dispositions:
Accounts receivable	(38.2)	(41.5)	(31.8)
Inventories	(50.6)	(11.6)	7.6
Prepaid income taxes	(9.4)	(8.7)	4.7
Prepaid expenses and other assets	(4.2)	(2.4)	(4.9)
Accounts payable	23.9	(10.6)	40.1
Accrued expenses and other liabilities	53.8	(17.8)	45.6
Deferred revenue	(1.5)	(10.6)	(4.9)
Net cash provided by operating activities	732.9	8.3	798.2
INVESTING ACTIVITIES
Acquisition of businesses, net of cash acquired	(76.5)	(1,558.1)	0
Proceeds from sale of business	0	1,865	0
Purchase of property and equipment	(58.4)	(57.8)	(47.3)
Increase in equipment under customer usage agreements	(47.2)	(49.8)	(47.2)
Proceeds from sale of available-for-sale marketable securities	0.1	87.1	31.1
Purchase of cost method investment	(6)	0	0
Purchases of insurance contracts	0	0	(5.2)
Sales of mutual funds	0	0	5.2
Other activity	(7.2)	(0.6)	(5)
Net cash (used in) provided by investing activities	(195.2)	285.8	(68.4)
FINANCING ACTIVITIES
Proceeds from long-term debt	1,500	0	0
Repayment of long-term debt	(1,359.4)	(84.4)	(75)
Proceeds from Senior Notes	1,350	0	0
Repayment of Senior Notes	(1,037.7)	0	0
Payments to extinguish convertible notes	(546.2)	(396.2)	(392.8)
Repayment of acquired debt	(3.3)	0	0
Proceeds from amounts borrowed under revolving credit line	1,150	345	50
Repayment of amounts borrowed under revolving credit line	(1,195)	0	(225)
Proceeds from accounts receivable securitization program	34	48	200
Repayments under accounts receivable securitization program	(9)	(48)	0
Repurchase of common stock	(275.8)	(200.1)	(250)
Payment of debt issuance costs	(23.5)	0	0
Purchase of interest rate caps	(3.7)	(1.9)	0
Net proceeds from issuance of common stock under employee stock plans	33.2	49	38.5
Payments under capital lease obligations	(1.7)	(0.9)	0
Payment of minimum tax withholdings on net share settlements of equity awards	(16.7)	(19.7)	(16.4)
Net cash used in financing activities	(404.8)	(309.2)	(670.7)
Effect of exchange rate changes on cash and cash equivalents	(6.8)	7.3	(2)
Net increase (decrease) in cash and cash equivalents	126.1	(7.8)	57.1
Cash and cash equivalents, beginning of period	540.6	548.4	491.3
Cash and cash equivalents, end of period	$ 666.7	$ 540.6	$ 548.4

Operations

Operations	12 Months Ended
	Sep. 29, 2018
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Operations	Operations Hologic, Inc. (the “Company” or “Hologic”) develops, manufactures and supplies premium diagnostics products, medical imaging systems, surgical products and light-based aesthetic and medical treatment systems with an emphasis on women's health. The Company operates in five segments: Diagnostics, Breast Health, Medical Aesthetics, GYN Surgical and Skeletal Health.

Summary of Significant Accounti

Summary of Significant Accounting Policies	12 Months Ended
	Sep. 29, 2018
Accounting Policies [Abstract]
Summary of Significant Accounting Policies	Summary of Significant Accounting Policies Principles of Consolidation 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 Company’s fiscal year ends on the last Saturday in September. Fiscal 2018 , 2017 and 2016 ended on September 29, 2018 , September 30, 2017 and September 24, 2016 , respectively. Fiscal 2017 is a 53-week year and fiscal 2018 and 2016 were 52-week years. 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 consolidated financial statements as of and for the year ended September 29, 2018, except for the settlement of patent infringement litigation with Smith & Nephew, Inc. for $34.8 million (refer to Note 12 for additional information), which was a subsequent event recognized as of September 29, 2018. In addition, the Company completed the acquisition of Focal Therapeutics, Inc. on October 1, 2018 for approximately $125.0 million (refer to Note 3 for additional information). Management’s Estimates and Uncertainties The preparation of financial statements in conformity with U.S. generally accepted accounting principles ("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. Significant estimates and assumptions by management affect the Company’s revenue recognition for multiple element arrangements, estimated fair value of cost-method equity investments, valuations, purchase price allocations and contingent consideration related to business combinations, expected future cash flows including growth rates, discount rates, terminal values and other assumptions and estimates used to evaluate the recoverability of long-lived assets and goodwill, estimated fair values of intangible assets and goodwill, amortization methods and periods, warranty reserves, certain accrued expenses, restructuring and other related charges, contingent liabilities, tax reserves, deferred tax rates and recoverability of the Company’s net deferred tax assets and related valuation allowances. Although the Company regularly assesses these estimates, actual results could differ materially from these estimates. Changes in estimates are recorded in the period in which they become known. The Company bases its estimates on historical experience and various other assumptions that it believes to be reasonable under the circumstances. The Company is subject to a number of risks similar to those of other companies of similar size in its industry, including dependence on third-party reimbursements to support the markets of the Company’s products, early stage of development of certain products, rapid technological changes, recoverability of long-lived assets (including intangible assets and goodwill), competition, stability of world financial markets, ability to obtain regulatory approvals, changes in the regulatory environment, limited number of suppliers, customer concentration, integration of acquisitions, substantial indebtedness, government regulations, management of international activities, protection of proprietary rights, patent and other litigation, dependence on contract manufacturers and dependence on key individuals. Cash Equivalents Cash equivalents are highly liquid investments with insignificant interest rate risk and maturities of three months or less at the time of acquisition. Marketable Securities In the first quarter of fiscal 2018, the Company sold its remaining marketable security, which was an investment in the stock of a publicly traded company, for a realized loss of $0.6 million . The Company had classified its equity securities as available-for-sale and were recorded at fair value with the unrealized gains or losses, net of tax, recorded within accumulated other comprehensive loss. The Company's various investments were liquidated over the last few years. In connection with the acquisition of Cynosure, Inc. in fiscal 2017, the Company assumed $82.9 million of short and long-term marketable securities, which were classified as available-for-sale and primarily comprised of state and municipal bonds and U.S. treasury notes. During fiscal 2017, the Company liquidated these investments. In the first quarter of fiscal 2016, the Company sold all of its shares in one of its marketable securities and recorded a realized gain of $25.1 million in other income (expense), net. No material impairment charges were recorded in 2018, 2017, or 2016. Concentrations of Credit Risk Financial instruments that subject the Company to credit risk primarily consist of cash and cash equivalents, cost-method equity investments, and trade accounts receivable. The Company invests its cash and cash equivalents with high credit quality financial institutions. The Company’s customers are principally located in the United States, Europe and Asia. The Company performs ongoing credit evaluations of the financial condition of its customers and generally does not require collateral. Although the Company is directly affected by the overall financial condition of the healthcare industry, as well as global economic conditions, management does not believe significant credit risk exists as of September 29, 2018 . The Company generally has not experienced any material losses related to receivables from individual customers or groups of customers in the healthcare industry. The Company maintains an allowance for doubtful accounts based on accounts past due and historical collection experience. There were no customers with balances greater than 10% of accounts receivable as of September 29, 2018 and September 30, 2017 , or any customers that represented greater than 10% of consolidated revenues for fiscal years 2018 , 2017 and 2016 . Supplemental Cash Flow Statement Information Years ended September 29, 2018 September 30, 2017 September 24, 2016 Cash paid during the period for income taxes $ 178.2 $ 867.8 $ 184.8 Cash paid during the period for interest $ 122.1 $ 102.4 $ 104.0 Inventories Inventories are valued at the lower of cost or market on a first in, first out basis. Work-in-process and finished goods inventories consist of materials, labor and manufacturing overhead. The valuation of inventory requires management to estimate excess and obsolete inventory. The Company employs a variety of methodologies to determine the net realizable value of its inventory. Provisions for excess and obsolete inventory are primarily based on management’s estimates of forecasted sales, usage levels and expiration dates, as applicable for disposable products. A significant change in the timing or level of demand for the Company’s products compared to forecasted amounts may result in recording additional charges for excess and obsolete inventory in the future. The Company records charges for excess and obsolete inventory within cost of product revenues. Inventories consisted of the following: September 29, 2018 September 30, 2017 Raw materials $ 134.9 $ 95.7 Work-in-process 52.1 45.0 Finished goods 197.1 190.9 $ 384.1 $ 331.6 Property, Plant and Equipment Property, plant and equipment is recorded at cost less allowances for depreciation. The straight-line method of depreciation is used for all property and equipment. Property, plant and equipment consisted of the following: September 29, 2018 September 30, 2017 Equipment $ 391.9 $ 357.9 Equipment under customer usage agreements 399.6 368.7 Buildings and improvements 175.1 172.0 Leasehold improvements 63.0 60.6 Land 46.3 46.3 Furniture and fixtures 18.4 20.8 1,094.3 1,026.3 Less - accumulated depreciation and amortization (616.1 ) (553.5 ) $ 478.2 $ 472.8 Property, plant and equipment are depreciated over the following estimated useful lives: Asset Classification Estimated Useful Life Building and improvements 20–35 years Equipment 3–10 years Equipment under customer usage agreements 3–8 years Furniture and fixtures 5–7 years Leasehold improvements Shorter of the Original Term of Lease or Estimated Useful Life Equipment under customer usage agreements primarily consists of diagnostic instrumentation and imaging equipment located at customer sites but owned by the Company. Generally, the customer has the right to use the equipment for a period of time provided they meet certain agreed to conditions. The Company recovers the cost of providing the equipment from the sale of disposables. The depreciation costs associated with equipment under customer usage agreements are charged to cost of product revenues over the estimated useful life of the equipment. The costs to maintain the equipment in the field are charged to cost of product revenue as incurred. Long-Lived Assets The Company reviews its long-lived assets, which includes property, plant and equipment and identifiable intangible assets (see below for discussion of intangible assets), for impairment whenever events or changes in circumstances indicate that the carrying amount of an asset may not be recoverable in accordance with ASC 360-10-35-15, Property, Plant and Equipment—Impairment or Disposal of Long-Lived Assets (ASC 360). Recoverability of these assets is evaluated by comparing the carrying value of the assets to the undiscounted cash flows estimated to be generated by those assets over their remaining economic life. If the undiscounted cash flows are not sufficient to recover the carrying value of the assets, the assets are considered impaired. The impairment loss is measured by comparing the fair value of the assets to their carrying value. Fair value is determined by either a quoted market price, if any, or a value determined by a discounted cash flow technique. Business Combinations and Acquisition of Intangible Assets The Company accounts for the acquisition of a business in accordance with ASC 805, Business Combinations (ASC 805). Amounts paid for each acquisition are allocated to the assets acquired and liabilities assumed based on their fair values at the date of acquisition. The Company determines the fair value of acquired intangible assets based on detailed valuations that use certain information and assumptions provided by management. The Company allocates any excess purchase price over the fair value of the net tangible and intangible assets acquired to goodwill. The Company uses the income approach to determine the fair value of developed technology and in-process research and development ("IPR&D") acquired in a business combination. This approach determines fair value by estimating the after-tax cash flows attributable to the respective asset over its useful life and then discounting these after-tax cash flows back to a present value. The Company bases its revenue assumptions on estimates of relevant market sizes, expected market growth rates, expected trends in technology and expected product introductions by competitors. Developed technology represents patented and unpatented technology and know-how. The value of the in-process projects is based on the project's stage of completion, the complexity of the work completed as of the acquisition date, the projected costs to complete, the contribution of core technologies and other acquired assets, the expected introduction date, the estimated cash flows to be generated upon commercial release and the estimated useful life of the technology. The Company believes that the estimated developed technology and IPR&D amounts represent the fair value at the date of acquisition and do not exceed the amount a third-party would pay for the assets. The Company also uses the income approach, as described above, to determine the estimated fair value of certain other identifiable intangible assets including customer relationships, distribution agreements, trade names and business licenses. Customer relationships represent established relationships with customers, which provide a ready channel for the sale of additional products and services. Trade names represent acquired company and product names, and distribution agreements generally pertain to exclusive distribution of certain products manufactured by third parties. Intangible Assets and Goodwill Intangible Assets Intangible assets are initially recorded at fair value and stated net of accumulated amortization and impairments. The Company amortizes its intangible assets that have finite lives using either the straight-line method, or if reliably determinable, based on the pattern in which the economic benefit of the asset is expected to be utilized. Amortization is recorded over the estimated useful lives ranging from 2 to 30 years. The Company evaluates the recoverability of its definite lived intangible assets whenever events or changes in circumstances or business conditions indicate that the carrying value of these assets may not be recoverable based on expectations of future undiscounted cash flows for each asset group. If the carrying value of an asset or asset group exceeds its undiscounted cash flows, the Company estimates the fair value of the assets, generally utilizing a discounted cash flow analysis based on the present value of estimated future cash flows to be generated by the assets using a risk-adjusted discount rate. To estimate the fair value of the assets, the Company uses market participant assumptions pursuant to ASC 820, Fair Value Measurements . Indefinite lived intangible assets, such as IPR&D assets, are required to be tested for impairment annually, or more frequently if indicators of impairment are present. The Company’s annual impairment test date is as of the first day of its fourth quarter. Intangible assets consisted of the following: September 29, 2018 September 30, 2017 Description Gross Carrying Value Accumulated Amortization Gross Carrying Value Accumulated Amortization Acquired intangible assets: Developed technology $ 4,573.3 $ 2,505.8 $ 4,528.7 $ 2,186.8 In-process research and development 5.5 — 46.0 — Customer relationships 556.5 428.1 552.8 393.8 Trade names 312.5 175.0 310.3 156.4 Distribution agreement 42.0 8.0 42.0 2.8 Non-competition agreements 1.5 0.5 1.5 0.1 Business licenses 2.4 2.2 2.4 2.2 Total acquired intangible assets $ 5,493.7 $ 3,119.6 $ 5,483.7 $ 2,742.1 Internal-use software 58.5 49.3 64.5 46.1 Capitalized software embedded in products 19.6 4.3 14.3 2.0 Total intangible assets $ 5,571.8 $ 3,173.2 $ 5,562.5 $ 2,790.2 During first quarter of fiscal 2018, the Company acquired Emsor S.A. and recorded $4.6 million of customer relationship intangible assets. In the fourth quarter of fiscal 2018, the Company acquired Faxitron Bipotics, LLC and recorded an aggregate of $53.4 million of intangible assets. During the second quarter of fiscal 2017, the Company divested its blood screening business and the net book value of $154.0 million of developed technology and $387.7 million of customer relationship assets were disposed of (see Note 13). In the second quarter of fiscal 2017, the Company acquired Cynosure and recorded an aggregate of $994.0 million of intangible assets (see Note 3). In the third quarter of fiscal 2017, the Company acquired Medicor and recorded $5.4 million of intangible assets. In addition, during the third quarter of fiscal 2017, the Company obtained CE approval for its last in-process research and development project acquired in the Gen-Probe Incorporated acquisition and transferred $3.7 million to developed technology. During the fourth quarter of fiscal 2017, the Company obtained regulatory approval for two of three projects from the Cynosure acquisition with an aggregate fair value of $61.0 million and these assets were reclassified to developed technology. The remaining project, which had an initial fair value of $46.0 million , was abandoned in the second quarter of fiscal 2018 due to unsuccessful clinical results. As a result, the Company recorded a $46.0 million impairment charge in the second quarter of fiscal 2018. The Company had identified certain software acquired in the Cynosure acquisition that would be abandoned in fiscal 2018 and shortened the useful life. As such, the Company accelerated depreciation of the asset resulting in an additional $5.9 million and $3.0 million of expense recorded in fiscal 2018 and 2017, respectively. Amortization expense related to developed technology is classified as a component of cost of product revenues—amortization of intangible assets. Amortization expense related to customer relationships, contracts, trade names, distribution agreements, and business licenses is classified as a component of amortization of intangible assets within operating expenses. The estimated amortization expense at September 29, 2018 for each of the five succeeding fiscal years was as follows: Fiscal 2019 $ 370.9 Fiscal 2020 $ 359.8 Fiscal 2021 $ 338.2 Fiscal 2022 $ 325.4 Fiscal 2023 $ 226.0 Goodwill In accordance with ASC 350, Intangibles—Goodwill and Other (ASC 350), the Company tests goodwill for impairment annually at the reporting unit level and between annual tests if events and circumstances indicate it is more likely than not that the fair value of a reporting unit is less than its carrying value. Events that could indicate impairment and trigger an interim impairment assessment include, but are not limited to, current economic and market conditions, including a decline in market capitalization, a significant adverse change in legal factors, business climate, operational performance of the business or key personnel, and an adverse action or assessment by a regulator. In performing the impairment test, the Company utilizes the two-step approach prescribed under ASC 350. The first step requires a comparison of the carrying value of each reporting unit to its estimated fair value. To estimate the fair value of its reporting units for Step 1, the Company primarily utilizes the income approach. The income approach is based on a DCF analysis and calculates the fair value by estimating the after-tax cash flows attributable to a reporting unit and then discounting the after-tax cash flows to present value using a risk-adjusted discount rate. Assumptions used in the DCF require significant judgment, including judgment about appropriate discount rates and terminal values, growth rates, and the amount and timing of expected future cash flows. The forecasted cash flows are based on the Company’s most recent budget and strategic plan and for years beyond this period, the Company’s estimates are based on assumed growth rates expected as of the measurement date. The Company believes its assumptions are consistent with the plans and estimates used to manage the underlying businesses. The discount rates used are intended to reflect the risks inherent in future cash flow projections and are based on estimates of the weighted-average cost of capital (“WACC”) of market participants relative to each respective reporting unit. The market approach considers comparable market data based on multiples of revenue or earnings before interest, taxes, depreciation and amortization (“EBITDA”) and is primarily used as a corroborative analysis to the results of the DCF analysis. The Company believes its assumptions used to determine the fair value of its reporting units are reasonable. If different assumptions were used, particularly with respect to forecasted cash flows, terminal values, WACCs, or market multiples, different estimates of fair value may result and there could be the potential that an impairment charge could result. Actual operating results and the related cash flows of the reporting units could differ from the estimated operating results and related cash flows. If the carrying value of a reporting unit exceeds its estimated fair value, the Company applies the single step approach under Accounting Standards Update No. 2017-04, Intangibles-Goodwill and Other (Topic 350): Simplifying the Test for Goodwill Impairment (ASU 2017-04). As a result of this simplified approach the goodwill impairment is calculated as the amount by which the carrying value of the reporting unit exceeds its fair value to the extent of the goodwill balance. The Company adopted this ASU in fiscal 2018. During the second quarter of fiscal 2018, in connection with commencing its company-wide annual budgeting and strategic planning process, evaluating its current operating performance of its Medical Aesthetics reporting unit, and abandoning an in-process research and development project, the Company reduced its short term and long term revenue and operating income forecasts and determined that indicators of impairment existed in its Medical Aesthetics reporting unit. The Medical Aesthetics reporting unit is solely comprised of the Cynosure business, which the Company acquired on March 22, 2017. The updated forecast reflected significantly reduced volume and market penetration projections resulting in lower short-term and long-term profitability than expected at the time of the Cynosure acquisition. As a result of these current events and circumstances, the Company determined that it was more likely than not that this change would reduce the fair value of the reporting unit below its carrying amount. To estimate the fair value of the reporting unit, the Company utilized the DCF analysis. The forecasted cash flows were based on the Company's most recent budget and strategic plan and for period beyond the strategic plan, the Company's estimates are based on assumed growth rates expected as of the measurement date. The Company believes its assumptions were consistent with the plans and estimates used to manage the underlying business. The discount rate used is intended to reflect the risks inherent in future cash flow projections and was based on an estimate of the weighted average cost of capital (WACC) of market participants relative to the reporting unit. The basis of fair value for Medical Aesthetics assumed the reporting unit would be purchased or sold in a non-taxable transaction, and the discount rate of 12.0% applied to the after-tax cash flows was consistent with that used in the purchase accounting performed in fiscal 2017. As a result of this analysis, the fair value of the Medical Aesthetic reporting unit was significantly below its carrying value, and the Company recorded a goodwill impairment charge of $685.7 million during the second quarter of fiscal 2018. This reporting unit now has a goodwill value of zero . Actual operating results and the related cash flows of the reporting units could differ from the estimated operating results and related cash flows. Due to the presence of impairment indicators, the Company also performed an impairment test of this reporting unit’s long-lived assets. This impairment evaluation was based on expectations of future undiscounted cash flows compared to the carrying value of the long-lived assets. The Company’s cash flow estimates were consistent with those used in the goodwill impairment test discussed above. Based on this analysis, the undiscounted cash flows of the Medical Aesthetics long-lived assets were in excess of their carrying value and thus deemed to not be impaired. The Company believes its procedures for estimating future cash flows were reasonable and consistent with market conditions at the time of estimation. The Company conducted its fiscal 2018 impairment test for its reporting units on the first day of the fourth quarter, and as noted above used DCF and market approaches to estimate the fair value of its reporting units as of July 1, 2018, and ultimately used the fair value determined by the DCF approach in making its impairment test conclusions. 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 this analysis, 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. For illustrative purposes, had the fair value of each of the reporting units been lower by 10% , all of the reporting units would still have passed Step 1 of the goodwill impairment test. At September 29, 2018 , the Company believes that its reporting units, with goodwill aggregating $2.5 billion , were not at risk of failing Step 1 of the goodwill impairment test based on its current forecasts. The Company conducted its fiscal 2017 and 2016 impairment tests on the first day of the respective year's fourth quarter, and as noted above used DCF and market approaches to estimate the fair value of its reporting units as of July 2, 2017 and June 26, 2016, respectively, and ultimately used the fair value determined by the DCF approach in making its impairment test conclusions. 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 under the applicable goodwill impairment standard at these dates was not required. A rollforward of goodwill activity by reportable segment from September 30, 2017 to September 29, 2018 is as follows: Diagnostics Breast Health Medical Aesthetics GYN Surgical Skeletal Health Total Balance at September 30, 2017 $ 823.0 $ 641.5 $ 683.5 $ 1,015.1 $ 8.1 $ 3,171.2 Faxitron acquisition — 41.6 — — — 41.6 Emsor acquisition — 5.7 — — — 5.7 Impairment charge — — (685.7 ) — — (685.7 ) Foreign currency and other adjustments (1.8 ) 0.7 2.2 (0.7 ) — 0.4 Balance at September 29, 2018 $ 821.2 $ 689.5 $ — $ 1,014.4 $ 8.1 $ 2,533.2 Other Assets Other assets consisted of the following: September 29, 2018 September 30, 2017 Other Assets Life insurance contracts $ 44.2 $ 41.0 Deferred tax assets 12.9 9.1 Cost-method equity investments 8.8 3.0 Manufacturing access fees 4.6 7.1 Other 27.2 24.5 $ 97.7 $ 84.7 Life insurance contracts were purchased in connection with the Company’s Nonqualified Deferred Compensation Plan (“DCP”) and are recorded at their cash surrender value (see Note 9 for further discussion). Research and Software Development Costs Costs incurred for the research and development of the Company’s products are expensed as incurred. Nonrefundable advance payments for goods or services to be received in the future by the Company for use in research and development activities are deferred. The deferred costs are expensed as the related goods are delivered or the services are performed. The Company accounts for the development costs of software embedded in the Company’s products in accordance with ASC 985, Software. Costs incurred in the research, design and development of software embedded in products to be sold to customers are charged to expense until technological feasibility of the ultimate product to be sold is established. The Company’s policy is that technological feasibility is achieved when a working model, with the key features and functions of the product, is available for customer testing. Software development costs incurred after the establishment of technological feasibility and until the product is available for general release are capitalized, provided recoverability is reasonably assured. Capitalized software development costs are amortized over their estimate useful life and recorded within cost of revenues - product. Foreign Currency Translation The financial statements of the Company’s foreign subsidiaries are translated in accordance with ASC 830, Foreign Currency Matters. The reporting currency for the Company is the U.S. dollar. The functional currency of the Company’s foreign subsidiaries is determined based on the guidance in ASC 830. The majority of the Company's foreign subsidiaries' functional currency is the applicable local currency, although certain of the Company's foreign subsidiaries' functional currency is the U.S. dollar based on the nature of their operations or functions. Assets and liabilities of subsidiaries whose functional currency is the local currency are translated at the exchange rate in effect at each balance sheet date. Before translation, the Company re-measures foreign currency denominated assets and liabilities, including inter-company accounts receivable and payable, into the functional currency of the respective entity, resulting in unrealized gains or losses recorded in other income, net in the Consolidated Statements of Operations. Revenues and expenses are translated using average exchange rates during the respective period. Foreign currency translation adjustments are accumulated as a component of other comprehensive income (loss) as a separate component of stockholders’ equity. Gains and losses arising from transactions denominated in foreign currencies are included in other income, net in the Consolidated Statements of Operations and were not significant in any of the reporting periods presented. Accumulated Other Comprehensive Loss Other comprehensive income (loss) includes certain transactions that have generally been reported in the statement of stockholders’ equity. The following tables summarize the components and changes in accumulated balances of other comprehensive income for the periods presented: Year Ended September 29, 2018 Year Ended September 30, 2017 Foreign Currency Translation Marketable Securities Pension Plans Hedged Interest Rate Caps Total Foreign Currency Translation Marketable Securities Pension Plans Hedged Interest Rate Caps Total Beginning Balance $ (18.5 ) $ (0.4 ) $ (1.6 ) $ 4.3 $ (16.2 ) $ (26.1 ) $ (0.3 ) $ (2.5 ) $ (3.4 ) $ (32.3 ) Other comprehensive loss before reclassifications (8.1 ) — 0.5 (5.7 ) (13.3 ) 7.6 2.3 0.9 0.8 11.6 Charges (gains) reclassified to statement of operations — 0.4 — 3.6 4.0 — (2.4 ) — 6.9 4.5 Ending Balance $ (26.6 ) $ — $ (1.1 ) $ 2.2 $ (25.5 ) $ (18.5 ) $ (0.4 ) $ (1.6 ) $ 4.3 $ (16.2 ) In the first quarter of fiscal 2016, the Company sold all of its shares in one of its marketable securities and recorded a realized gain of $25.1 million in other income, net and resulted in reclassifying a $7.2 million gain out of accumulated other comprehensive loss to other income, net. 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, net in the Consolidated Statements of Operations. 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 rate interest on its credit facilities under the term loan feature of its credit facilities (see Note 5). 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. Certain of these cap agreements expired during fiscal 2017. During fiscal 2017, 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 5). 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. During fiscal 2018, the Comp

Business Combinations

Business Combinations	12 Months Ended
	Sep. 29, 2018
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. Pursuant to the terms and conditions of the merger agreement, 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 less any applicable exercise price. The acquisition was funded through available cash, and the total purchase price was $1.66 billion . The Company incurred $18.8 million of direct transaction costs 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 platforms that offer both non-surgical and surgical aesthetic treatments and procedures. Cynosure's results of operations are reported in the Company's Medical Aesthetics reportable segment from the date of acquisition. The total purchase price was allocated to Cynosure’s 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 purchase price allocation is as follows: Cash $ 107.2 Marketable securities 82.9 Accounts receivable 40.2 Inventory 120.0 Property, plant and equipment 44.1 Other assets and liabilities, net 11.9 Accounts payable and accrued expenses (76.6 ) 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 (315.2 ) Goodwill 685.7 Purchase Price $ 1,657.8 In performing the 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. As part of the purchase price allocation, the Company determined the identifiable intangible assets were developed technology, in-process research and development ("IPR&D"), a distribution agreement, customer relationships, and trade names. The fair value of the intangible assets was 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 were 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 comprise the significant product families of Cynosure, primarily SculpSure, Icon, and PicoSure. IPR&D projects related to in-process projects that had not reached technological feasibility as of the acquisition date and had no alternative future use. The primary basis for determining technological feasibility of these projects is obtaining regulatory approval to market the underlying product or expected commercial release depending on the project. The Company recorded $107.0 million of IPR&D related to three projects, which were expected to be completed during fiscal 2018 and 2019 with a cost to complete of approximately $18.0 million . All of the IPR&D assets were valued using the multiple-period excess earnings method approach. 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, which had an initial fair value of $46.0 million , was abandoned in the second quarter of fiscal 2018 due to unsuccessful clinical results. As a result, the Company recorded a $46.0 million impairment charge in the second quarter of fiscal 2018. 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 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 goodwill were based on several strategic and synergistic benefits that were expected to be realized from the Cynosure acquisition. These benefits included the expectation that the Company's entry into the aesthetics market would significantly broaden the Company's offering in women's health. The combined company was 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. During the second quarter of fiscal 2018, the Company identified indicators of impairment and performed an interim goodwill impairment analysis. This analysis resulted in the Company recording a goodwill impairment charge of $685.7 million in the second quarter of fiscal 2018 (see Note 2). Cynosure's revenue and pre-tax loss, which excluded 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 included 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 (the first day of fiscal 2016): Twelve Months Ended Twelve Months Ended September 30, 2017 September 24, 2016 Revenue $ 3,241.4 $ 3,244.6 Net income $ 768.5 $ 252.3 Basic earnings per common share $ 2.75 $ 0.90 Diluted earnings per common share $ 2.69 $ 0.88 The pro forma information for fiscal 2017 and 2016 was calculated after applying the Company's accounting policies and the impact of acquisition date fair value adjustments. Fiscal 2017 pro forma net income was adjusted to exclude acquisition-related transaction costs and restructuring costs solely related to the consolidation of the Medical Aesthetics business, which would have been included in fiscal 2016 pro forma net income. In addition, the fiscal 2017 pro forma net income was adjusted to exclude expenses related to the fair value adjustments associated with the acquisition of Cynosure that were recorded by the Company. 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 valuation, it has allocated $5.4 million of the purchase price to the 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 was allocated to the acquired tangible 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 $16.3 million , which includes a hold-back of $0.5 million that is payable eighteen months from the date of acquisition, and contingent consideration which the Company has estimated at $4.9 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 $4.6 million of the purchase price to the preliminary value of customer relationship intangible assets and $5.7 million to goodwill. The remaining $6.0 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. Faxitron On July 31, 2018, the Company completed the acquisition of Faxitron Bioptics, LLC ("Faxitron") and acquired all of the outstanding shares of Faxitron. The acquisition was funded through available cash, and the total purchase price was $89.0 million , which include hold-backs of $11.7 million that are payable up to one year from the date of acquisition, and contingent consideration which the Company has estimated at $2.9 million . The contingent consideration is payable upon meeting certain revenue growth metrics. Faxitron, headquartered in Tucson, Arizona, develops, manufactures, and markets digital radiography systems. Faxitron's results of operations are reported in the Company's Breast Health reportable segment from the date of acquisition. The total purchase price was allocated to Faxitron's preliminary tangible and identifiable intangible assets and liabilities based on the estimated fair values of those assets as of July 31, 2018, as set forth below. The preliminary purchase price allocation is as follows: Cash $ 2.4 Accounts receivable 4.0 Inventory 6.0 Other assets 3.1 Accounts payable and accrued expenses (4.9 ) Deferred revenue (1.9 ) Long-term debt (3.3 ) Identifiable intangible assets: Developed technology 44.9 In-process research and development 5.5 Customer relationships 0.7 Trade names 2.3 Deferred income taxes, net (11.4 ) Goodwill 41.6 Purchase Price $ 89.0 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 Faxitron'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"), 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 17% to 19% . 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 weighted average life of developed technology and customer relationships is 9 years the for trade names it is 7 years . 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 synergistic benefits that are expected to be realized from this acquisition. Benefits include the expectation of broadening the Company's Breath Health portfolio of products and technology. None of the goodwill is expected to be deductible for income tax purposes. Focal Therapeutics On October 1, 2018, the Company completed the acquisition of Focal Therapeutics, Inc. ("Focal") for an initial purchase price of approximately $125.0 million and paid $108.0 million in initial consideration, which is less certain holdbacks. Focal, headquartered in California, has commercialized its BioZorb marker, which is an implantable three-dimensional marker that helps clinicians overcome challenges in breast conserving surgery, or lumpectomy. Given that the acquisition closed on October 1, 2018, the Company determined it was impractical to provide all the disclosure required for a business combination pursuant to ASC 805.

Restructuring Charges

Restructuring Charges	12 Months Ended
	Sep. 29, 2018
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. As a result of these assessments, the Company has undertaken various restructuring actions which are described below. The following table displays charges taken related to restructuring actions in fiscal 2018 , 2017 and 2016 and a rollforward of the charges to the accrued balances as of September 29, 2018 : Fiscal 2018 Actions Fiscal 2017 Actions Fiscal 2016 Actions Total Restructuring Charges Fiscal 2016 charges: Workforce reductions $ — $ — $ 10.5 $ 10.5 Fiscal 2016 restructuring charges $ — $ — $ 10.5 $ 10.5 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 $ 11.7 $ — $ — $ 11.7 Facility closure costs 0.9 — 1.6 2.5 Fiscal 2018 restructuring charges $ 12.6 $ — $ 1.6 $14.2 Fiscal 2018 Actions Fiscal 2017 Actions Fiscal 2016 Actions Previous Other Charges Total Rollforward of Accrued Restructuring Balance as of September 26, 2015 $ — $ — $ — $ 5.7 $ 5.7 Fiscal 2016 restructuring charges $ — $ — $ 10.5 $ — $ 10.5 Stock-based compensation — — (0.4 ) — (0.4 ) Severance payments — — (4.6 ) (4.4 ) (9.0 ) Other payments — — — (0.5 ) (0.5 ) Balance as of September 24, 2016 $ — $ — $ 5.5 $ 0.8 $ 6.3 Fiscal 2017 restructuring charges $ — $ 8.5 $ 4.8 $ — $ 13.3 Severance payments — (1.0 ) (5.4 ) (0.2 ) (6.6 ) Other payments — — (1.2 ) (0.3 ) (1.5 ) Balance as of September 30, 2017 $ — $ 7.5 $ 3.7 $ 0.3 $ 11.5 Fiscal 2018 restructuring charges $ 12.6 $ — $ 1.6 $ — $ 14.2 Stock-based compensation (1.3 ) — — — (1.3 ) Severance payments and adjustments (6.8 ) (6.7 ) (0.2 ) — (13.7 ) Other payments (0.2 ) — (1.2 ) (0.2 ) (1.6 ) Balance as of September 29, 2018 $ 4.3 $ 0.8 $ 3.9 $ 0.1 $ 9.1 Fiscal 2018 Actions During the first, second and third quarters of fiscal 2018, the Company decided to terminate certain employees across the organization, including a corporate executive and primarily 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 $9.0 million in fiscal 2018. Included within the charge is $1.3 million related to the modification of equity awards. During fiscal 2018, the Company finalized its decision and plan to consolidate its legacy international accounting and customer service organizations into its Manchester, UK location and will be eliminating these positions in Belgium, France, Italy, Spain and Germany. This transition is expected to be completed in the first quarter of fiscal 2019 and upon completion these employees will be terminated. During fiscal 2018, the Company recorded $2.2 million for severance and benefits pursuant to both ASC 712 and ASC 420 depending on the legal requirements on a country by country basis. The Company expects to record an additional $0.6 million in the first quarter of fiscal 2019 for the remaining pro-rata charges. During the third quarter of fiscal 2018, the Company decided to close its Hicksville, New York facility where it manufactured the Cynosure element products. In connection with this plan, certain employees, primarily in manufacturing, were terminated. The employees were notified of termination and related benefits in the third quarter of fiscal 2018, and the Company recorded these charges pursuant to ASC 420. Employees were required to remain employed during this transition period and charges were recorded ratably over the required service period, which is expected to continue through the first quarter of fiscal 2019. The Company recorded a total of $0.5 million in severance and benefits charges in fiscal 2018. The Company expects to record an additional $0.3 million in the first quarter of fiscal 2019 for the remaining pro-rata charges. Fiscal 2017 Actions During the second quarter of fiscal 2017, the Company completed its acquisition of Cynosure. In connection with the acquisition, 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. The charges were recorded pursuant to ASC 712 and ASC 420 depending on the executive. During the fourth quarter of fiscal 2017, the decision was made to reduce headcount and related costs in R&D within Breast Health and to eliminate certain manufacturing personnel, primarily in Diagnostics. The majority of employees were notified of termination and related benefits in the fourth quarter of fiscal 2017, and the Company recorded these charges pursuant to ASC 420 as the benefits qualify as one-time termination benefits. As such, the Company recorded a charge for severance and benefits for these employees of $1.4 million in the fourth quarter. Fiscal 2016 Actions During the third quarter of fiscal 2015, the Company decided to close its Bedford, Massachusetts facility where it manufactured its Skeletal Health products and provided certain support manufacturing services for its Breast Health segment. The manufacturing of the Skeletal Health products was outsourced to a third-party, and the Breast Health manufacturing services were moved to the Company's Danbury, Connecticut and Marlborough, Massachusetts facilities. In addition, research and development, sales and services support and administrative functions were moved to both Marlborough and Danbury. The transition was substantially completed by the end of calendar year 2016. In connection with this plan, certain employees, primarily in manufacturing, were terminated. The employees were notified of termination and related benefits in the first quarter of fiscal 2016, and the Company recorded these charges pursuant to ASC 420. Employees were required to remain employed during this transition period and charges were recorded ratably over the required service period. The Company recorded $1.7 million in severance and benefits charges related to this action in fiscal 2016. This action was completed in the first quarter of fiscal 2017. In connection with the closure of the Bedford location, during the first quarter of fiscal 2017 the Company recorded $3.5 million for lease obligation charges related to the first floor of the facility as the Company determined it had 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 could obtain. During the third quarter of fiscal 2017, the Company updated its assumption regarding the time period it would take to obtain a subtenant at the Bedford location and as a result recorded an additional $1.3 million lease obligation charge. During the third quarter of fiscal 2018, the Company further adjusted its assumptions and lowered the estimate of the sublease income rate and extended the time period to obtain a sub-tenant. As a result, the Company recorded an additional charge of $1.6 million . 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. During the first quarter of fiscal 2016, the Company began implementing a second plan to consolidate and improve operational efficiency of its international sales and marketing and field services operations and certain support functions. As a result, the Company identified and terminated certain employees during each quarter in fiscal 2016. Severance and benefits under this action were recorded pursuant to ASC 712, and ASC 420 depending on the circumstances. The Company recorded severance and benefit charges of $7.9 million in fiscal 2016 related to this plan.

Borrowings and Credit Arrangeme

Borrowings and Credit Arrangements	12 Months Ended
	Sep. 29, 2018
Debt Disclosure [Abstract]
Borrowings and Credit Agreements	Borrowings and Credit Agreements The Company’s borrowings consisted of the following: September 29, September 30, Current debt obligations, net of debt discount and deferred issuance costs: Term Loan $ 74.7 $ 121.3 Revolver 300.0 345.0 Securitization Program 225.0 200.0 Convertible Notes — 484.5 Total current debt obligations 599.7 1,150.8 Long-term debt obligations, net of debt discount and issuance costs: Term Loan 1,376.3 1,190.5 2022 Senior Notes — 981.6 2025 Senior Notes 935.2 — 2028 Senior Notes 393.1 — Total long-term debt obligations 2,704.6 2,172.1 Total debt obligations $ 3,304.3 $ 3,322.9 The debt maturity schedule for the Company’s obligations as of September 29, 2018 is as follows: 2019 2020 2021 2022 2023 2024 and Thereafter Total Term Loan $ 75.0 $ 75.0 $ 112.5 $ 150.0 $ 1,050.0 $ — $ 1,462.5 Revolver 300.0 — — — — — 300.0 Securitization Program 225.0 — — — — — 225.0 2025 Senior Notes — — — — — 950.0 950.0 2028 Senior Notes — — — — — 400.0 400.0 $ 600.0 $ 75.0 $ 112.5 $ 150.0 $ 1,050.0 $ 1,350.0 $ 3,337.5 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 amended and restated 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. The 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 Company may borrow up to $1.5 billion , subject to certain sublimits, with a maturity date of October 3, 2022. Among other uses, the Company has used its Amended Revolver to make payments on its outstanding debt, to fund acquisitions, and to fund repurchases of its common stock. During the third quarter of fiscal 2018, the Company borrowed $250.0 million under its Amended Revolver to cash settle the conversions of its 2.00% Convertible Senior Notes due 2042 of which $165.0 million was repaid. As of September 29, 2018 , the Company had $300.0 million outstanding under the Amended Revolver. Subsequent to September 29, 2018, the Company borrowed an additional $50.0 million . 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. Interest expense, non-cash interest expense, weighted average interest rate, and interest rate at the end of period under the Amended and Restated Credit Agreement, in fiscal 2018, and Prior Credit Agreement, in fiscal 2017 and 2016, is as follows: September 29, 2018 September 30, 2017 September 24, 2016 Interest expense (1) $ 60.8 $ 42.3 $ 40.4 Non-cash interest expense $ 2.6 $ 4.2 $ 4.4 Weighted average interest rate 3.23 % 2.39 % 2.08 % Interest rate at end of period 3.74 % 2.73 % 2.05 % (1) Interest expense includes 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 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 September 29, 2018. 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 September 29, 2018. Pursuant to ASC 470, Debt (ASC 470), the accounting for entering into the Amended and Restated Credit Agreement and using the proceeds to pay off the Prior Credit Agreement was evaluated on a creditor-by-creditor basis to determine whether each transaction should be accounted for as a modification or extinguishment. Certain creditors under the Prior 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 debt discount for fees paid directly to the lenders. Prior Credit Agreement On May 29, 2015, the Company and certain of its domestic subsidiaries entered into a Credit and Guaranty Agreement (the “ Prior 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 party thereto. This Prior Credit Agreement replaced the Company's previous senior secured credit facility with Goldman Sachs Bank USA, in its capacity as administrative agent and collateral agent and the lenders party thereto ("August 2012 Credit Agreement") entered into on August 1, 2012, and the proceeds under the Prior Credit Agreement of $1.68 billion were used to pay off the amounts outstanding under the August 2012 Credit Agreement. The credit facilities ("Credit Facilities") under the Credit Agreement consisted of: • A $1.5 billion secured term loan to the Company with a final maturity date of May 29, 2020 (the “Term Loan”); and • A secured revolving credit facility under which the Borrowers (as defined below) may borrow up to $1 billion , subject to certain sublimits, with a final maturity date of May 29, 2020 (the “Revolver”). Senior Notes 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. On January 19, 2018, the Company completed a private placement and allocated an additional $600 million in aggregate principal amount to 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. As a result, the total aggregate principal balance of 2025 Senior Notes is $950 million . The 2025 Senior Notes are general senior unsecured obligations of the Company and are guaranteed on a senior unsecured basis by certain domestic subsidiaries. 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 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 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. The Company evaluated the 2025 Senior Notes for derivatives pursuant to ASC 815 and did not identify any embedded derivatives that require bifurcation. All features were deemed to be clearly and closely related to the host instrument. 2028 Senior Notes On January 19, 2018, the Company completed a private placement of $1.0 billion aggregate principal amount of senior notes and allocated $400 million in aggregate principal amount to 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 2028 Senior Notes are general senior unsecured obligations of the Company and are guaranteed on a senior unsecured basis by certain domestic subsidiaries. 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 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 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. The Company evaluated the 2028 Senior Notes for derivatives pursuant to ASC 815 and did not identify any embedded derivatives that require bifurcation. All features were deemed to be clearly and closely related to the host instrument. Interest expense for the 2028 Senior Notes, 2025 Senior Notes and 2022 Senior Notes is as follows: September 29, 2018 September 30, 2017 September 24, 2016 Interest Rate Interest Expense (1) Non-Cash Interest Expense Interest Expense (1) Non-Cash Interest Expense Interest Expense (1) Non-Cash Interest Expense 2028 Senior Notes 4.625 % $ 13.3 $ 0.5 $ — $ — $ — $ — 2025 Senior Notes 4.375 % 34.7 1.6 — — — — 2022 Senior Notes 5.250 % 21.2 1.5 57.3 3.9 56.0 3.8 Total $ 69.2 $ 3.6 $ 57.3 $ 3.9 $ 56.0 $ 3.8 (1) Interest expense includes non-cash interest expense related to the amortization of the deferred issuance costs and accretion of the debt discount. 2022 Senior Notes The Company had 5.250% Senior Notes due 2022 (the “2022 Senior Notes”) outstanding and bore interest at the rate of 5.250% per year, payable semi-annually on January 15 and July 15 of each year. The Company used the net proceeds of the 2025 Senior Notes and the 2028 Senior Notes offering in January 2018 to redeem in full the 2022 Senior Notes in the aggregate principal amount of $1.0 billion on February 15, 2018 at an aggregate redemption price of $1.04 billion , including a make-whole provision payment $37.7 million . Since the Company planned to use the proceeds from the 2025 Senior Notes and the 2028 Senior Notes offering to redeem the 2022 Senior Notes, the Company evaluated the accounting for this transaction under ASC 470 to determine modification versus extinguishment accounting on a creditor-by-creditor basis. Certain 2022 Senior Note holders either did not participate in this refinancing transaction or reduced their holdings and these transactions were accounted for as extinguishments. As a result, the Company recorded a debt extinguishment loss in the second quarter of fiscal 2018 of $44.9 million , which comprised pro-rata amounts of the make-whole provision premium payment, debt discount and debt issuance costs. For the remaining 2022 Senior Notes holders who participated in the refinancing, these transactions were accounted for as modifications because on a creditor-by-creditor basis the present value of the cash flows between the debt instruments before and after the transaction was less than 10% . The Company recorded a portion of the transaction expenses of $2.6 million to interest expense pursuant to ASC 470, subtopic 50-40. The remaining debt issuance costs of $1.5 million and debt discount of $1.5 million related to the modified debt were allocated between the 2025 Senior Notes and 2028 Senior Notes on a pro-rata basis, and will be amortized over the life of the debt using the effective interest method. Convertible Notes As of September 29, 2018, the Company had no Convertible Notes outstanding. The following describes the Convertible Note transactions during fiscal 2018, 2017, and 2016. On December 10, 2007, the Company issued and sold $1.725 billion , at par, of 2.00% Convertible Senior Notes due December 15, 2037 (“2007 Notes”). On November 18, 2010, the Company entered into separate, privately-negotiated exchange agreements under which it retired $450.0 million in aggregate principal of its 2007 Notes for $450.0 million in aggregate principal of new 2.00% Convertible Exchange Senior Notes due December 15, 2037 (“2010 Notes”). On February 29, 2012, the Company entered into separate, privately-negotiated exchange agreements under which it retired $500.0 million in aggregate principal of the 2007 Notes for $500.0 million in aggregate principal of new 2.00% Convertible Senior Notes due March 1, 2042 (“2012 Notes”). On February 14, 2013, the Company entered into separate, privately-negotiated exchange agreements under which it retired $370.0 million in aggregate principal of the 2007 Notes for $370.0 million in aggregate principal of new 2.00% Convertible Senior Notes due December 15, 2043 (“2013 Notes”). The remaining 2007 Notes were redeemed in fiscal 2014. On November 9, 2016, the Company announced that pursuant to the terms of the indenture for the 2010 Notes, holders of the 2010 Notes had the option of requiring the Company to repurchase their 2010 Notes on December 16, 2016 at a repurchase price payable in cash equal to 100% of the original principal amount of the 2010 Notes. None of the 2010 Notes were surrendered for repurchase pursuant to the option. In addition, the Company also announced on November 9, 2016 that, pursuant to the terms of the indenture, it had elected to redeem, on December 19, 2016, all of the then outstanding 2010 Notes at a redemption price payable in cash equal to 100% of the accreted principal amount of the 2010 Notes. Holders of the 2010 Notes also had a right to convert their 2010 Notes. During the first quarter of fiscal 2017, all of the outstanding 2010 Notes were either converted or surrendered for conversion in aggregate principal of $12.3 million , which was paid out over the first and second quarters of fiscal 2017. The payouts included an additional $8.7 million of premium payments due to the Company's stock price exceeding the conversion price. The 2012 Notes and the 2013 Notes are collectively referred to herein as the “Convertible Notes.” On January 29, 2018, the Company announced that pursuant to the terms of the indenture for the 2012 Notes, holders of the 2012 Notes had the option of requiring the Company to repurchase their 2012 Notes on March 1, 2018 at a repurchase price payable in cash equal to 100% of the accreted principal amount of the 2012 Notes, plus accrued and unpaid interest. The Company also announced on January 29, 2018 that, it had elected to redeem, on March 6, 2018, all of the then outstanding 2012 Notes at a redemption price payable in cash equal to 100% of the accreted principal amount of the 2012 Notes, plus accrued and unpaid interest. Holders also had the right to convert their 2012 Notes. During the second quarter of fiscal 2018, 2012 Notes in aggregate original principal amount of $200.5 million were surrendered for conversion and the Company cash settled these conversions for $243.3 million during April 2018. As a result, on a gross basis, $42.8 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 $12.0 million within additional paid-in-capital. The remaining $5.5 million in original principal amount of the 2012 Notes was redeemed by the Company on March 6, 2018. On December 15, 2017, pursuant to the provisions of the indenture governing the Company's 2013 Notes, the Company redeemed or repurchased an aggregate of $201.7 million in original principal amount of the 2013 Notes then outstanding for an aggregate repurchase price of $244.1 million , representing the then accreted principal amount of the 2013 Notes. The remaining $0.3 million in original principal amount of the 2013 Notes were converted, and the Company settled these conversions in cash in the second quarter of fiscal 2018. 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 2012 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 various dates during the fourth quarter of fiscal 2017, the Company entered into privately negotiated repurchase transactions and extinguished $17.9 million and $68.0 million principal amount of the 2012 Notes and 2013 Notes, respectively, for total payments of $23.1 million and $82.9 million , respectively. These amounts include 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 and $38.59 , respectively, and on the 2013 Notes accreted principal of $13.3 million . Under ASC 470, these transactions were accounted for as an extinguishment and derecognition of the 2012 Notes and 2013 Notes and resulted in an aggregate debt loss extinguishment of $0.6 million . On various dates during the third quarter of fiscal 2017, the Company entered into privately negotiated repurchase transactions and extinguished $100.0 million principal amount of each of its 2012 Notes and 2013 Notes, for total payments of $269.1 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 and $38.59 , respectively, and on the 2013 Notes accreted principal of $18.5 million . Under ASC 470, these transactions were accounted for as an extinguishment and derecognition of the 2012 Notes and 2013 Notes and resulted in an aggregate debt loss extinguishment of $2.6 million . On various dates during the fourth quarter of fiscal 2016, the Company entered into privately negotiated repurchase transactions and extinguished $46.3 million principal amount of the 2010 Notes for total payments of $79.2 million . These amounts include the conversion premium resulting from the Company's stock price on the date of the transactions being in excess of the conversion price of $23.03 for the 2010 Notes. Under ASC 470, these transactions were accounted for as an extinguishment and derecognition of the 2010 Notes and resulted in a debt loss extinguishment of $0.8 million . In addition, $1.3 million principal was put to the Company during the quarter. On various dates during the second quarter of fiscal 2016, the Company entered into privately negotiated repurchase transactions and extinguished $90.0 million and $136.6 million principal amount of the 2010 Notes and 2012 Notes, respectively, for total payments of $140.1 million and $171.3 million , respectively. These amounts include the conversion premium resulting from the Company's stock price on the date of the transactions being in excess of the conversion price of $23.03 and $31.175 for the 2010 Notes and 2012 Notes, respectively. Under ASC 470, these transactions were accounted for as an extinguishment and derecognition of the 2010 and 2012 Notes and resulted in an aggregate debt loss extinguishment of $4.5 million . Accounting for the Convertible Notes The Convertible Notes were recorded pursuant to FASB Staff Position (“FSP”) APB 14-1, Accounting for Convertible Debt Instruments That May Be Settled in Cash upon Conversion (Including Partial Cash Settlement) (FSP APB 14-1) (codified within ASC 470) since they can be settled in cash or partially in cash upon conversion. FSP APB 14-1 requires the liability and equity components of the convertible debt instrument to be separately accounted for in a manner that reflects the entity’s nonconvertible debt borrowing rate when interest expense is subsequently recognized. The excess of the debt’s principal amount over the amount allocated to the liability component was recognized as the value of the embedded conversion feature (“equity component”) within additional-paid-in capital in stockholders’ equity and amortized to interest expense over the expected life of the liability component (typically the date of the earliest redemption) using the effective interest method. The liability component was initially recorded at its fair value, which was calculated using a discounted cash flow technique. Key inputs used to estimate the fair value of the liability component included the Company’s estimated nonconvertible debt borrowing rate as of the measurement date (i.e., the date the Convertible Notes are issued), the amount and timing of cash flows, and the expected life of the Convertible Notes. The effective interest rate was estimated by comparing other companies’ debt issuances that had features similar to the Company’s debt excluding the conversion feature and who had similar credit ratings during the same annual period as the Company. In addition, third-party transaction costs were required to be allocated to the liability and equity components based on their relative values. The original issuance of the 2007 Notes and both exchange transactions for the 2010 Notes and 2012 Notes, which each included a derecognition and re-recognition, were accounted for under this accounting guidance. The 2013 Notes exchange transaction was accounted for as a modification pursuant to ASC 470-50 and not an extinguishment because the terms of the two debt instruments were not substantially different. The Company accounted for the 2012 Notes and 2013 Notes extinguishments in fiscal 2017, discussed above, under the derecognition provisions of subtopic ASC 470-20-40, which requires the allocations of the fair value of the consideration transferred and transaction costs incurred to the extinguishment of the liability component and the reacquisition of the equity component. In connection with these transactions, the Company recorded a debt extinguishment loss on the 2012 Notes of $0.9 million and a debt extinguishment loss on the 2013 Notes of $2.3 million , for a total debt extinguishment loss of $3.2 million in fiscal 2017. The loss on the debt was calculated as the difference between the fair value of the liability component immediately before the respective transactions and their related carrying values, which includes any debt discount and deferred issuance costs. The fair value of the liability component was calculated using a discounted cash flow technique and incorporates an estimated rate for non-convertible debt (with similar features as the 2012 and 2013 Notes excluding the conversion feature) issued by a company with a credit rating similar to the Company. In addition, under this accounting standard, a portion of the fair value of the consideration transferred is allocated to the reacquisition of the equity component, which is the difference between the fair value of the consideration transferred and the fair value of the liability component immediately before the extinguishment. As a result, on a gross basis, $58.6 million related to the 2012 and 2013 Notes was allocated to the reacquisition of the equity component of the original instrument, which was recorded net of deferred taxes of $31.1 million within additional paid-in-capital. The Company accounted for the 2010 Notes and 2012 Notes extinguishments in fiscal 2016, discussed above, under the derecognition provisions of subtopic ASC 470-20-40, which requires the allocation of the fair value of the consideration transferred and transaction costs incurred to the extinguishment of the liability component and the reacquisition of the equity component. In connection with these transactions, the Company recorded a debt extinguishment loss on the 2010 Notes of $4.6 million and a debt extinguishment loss on the 2012 Notes of $0.7 million , for a total debt extinguishment loss of $5.3 million in fiscal 2016. On a gross basis, $122.6 million related to the 2010 and 2012 Notes was allocated to the reacquisition of the equity component of the original instrument, which was recorded net of deferred taxes of $28.2 million within additional paid-in-capital. As of September 29, 2018 the Convertible Notes were fully settled and for September 30, 2017 , the Convertible Notes and related equity components (recorded in additional paid-in-capital, net of deferred taxes) consisted of the following: 2017 2012 Notes principal amount $ 245.4 Unamortized discount and issuance costs (1.9 ) Net carrying amount $ 243.5 Equity component, net of taxes $ 24.1 2013 Notes principal amount $ 202.0 Principal accretion 40.8 Unamortized discount and issuance costs (1.8 ) Net carrying amount $ 241.0 Equity component, net of taxes $ 71.8 Interest expense under the Convertible Notes is as follows: Years Ended September 29, September 30, September 24, Amortization of debt discount $ 3.5 $ 17.9 $ 22.3 Amortization of deferred financing costs 0.2 0.8 1.1 Principal accretion 1.6 15.6 16.6 Non-cash interest expense 5.3 34.3 40.0 2.00% accrued interest (cash) 1.8 6.7 10.0 $ 7.

Fair Value Measurements

Fair Value Measurements	12 Months Ended
	Sep. 29, 2018
Fair Value Disclosures [Abstract]
Fair Value Measurements	Fair Value Measurements The Company applies the provisions of ASC 820 for its financial assets and liabilities that are re-measured and reported at fair value each reporting period and its nonfinancial assets and liabilities that are re-measured and reported at fair value on a non-recurring basis. Fair value is the price that would be received from selling an asset or paid to transfer a liability in an orderly transaction between market participants at the measurement date. When determining fair value, the Company considers the principal or most advantageous market in which it would transact and considers assumptions that market participants would use when pricing the asset or liability. Fair Value Hierarchy ASC 820 establishes a three-level valuation hierarchy for disclosure of fair value measurements. Financial assets and liabilities are categorized within the valuation hierarchy based upon the lowest level of input that is significant to the measurement of fair value. The three levels of the hierarchy are defined as follows: • Level 1—Inputs to the valuation methodology are quoted market prices for identical assets or liabilities. • Level 2—Inputs to the valuation methodology are other observable inputs, including quoted market prices for similar assets or liabilities and market-corroborated inputs. • Level 3—Inputs to the valuation methodology are unobservable inputs based on management’s best estimate of inputs market participants would use in pricing the asset or liability at the measurement date, including assumptions about risk. Assets/Liabilities Measured and Recorded at Fair Value on a Recurring Basis The Company had investments in publicly-traded companies, which were valued using quoted market prices, representing Level 1 assets, and has investments in derivative instruments comprised 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 2 for further discussion and information on the equity investments, the interest rate caps and forward foreign currency contracts. In addition, the Company has contingent consideration liabilities related to its acquisitions that are recorded at fair value and were based on Level 3 inputs (see Note 3). Assets and liabilities measured and recorded at fair value on a recurring basis consisted of the following: Fair Value Measurements at September 29, 2018 Carrying Value Quoted Prices in Active Market for Identical Assets (Level 1) Significant Other Observable Inputs (Level 2) Significant Unobservable Inputs (Level 3) Assets: Interest rate caps - derivative 7.7 — 7.7 — Forward foreign currency contracts 3.2 — 3.2 — Total $ 10.9 $ — $ 10.9 $ — Liabilities: Contingent consideration $ 7.8 $ — $ — $ 7.8 Forward foreign currency contracts 0.2 — 0.2 — Total $ 8.0 $ — $ 0.2 $ 7.8 Fair Value Measurements at September 30, 2017 Carrying Value Quoted Prices in Active Market for Identical Assets (Level 1) Significant Other Observable Inputs (Level 2) Significant Unobservable Inputs (Level 3) Assets: Equity securities $ 0.1 $ 0.1 $ — $ — Interest rate caps - derivative 4.8 — 4.8 — Forward foreign currency contracts 0.4 — 0.4 — Total $ 5.3 $ 0.1 $ 5.2 $ — Liabilities: Forward foreign currency contracts 4.0 — 4.0 — Total $ 4.0 $ — $ 4.0 $ — There were no Level 3 assets or liabilities outstanding during fiscal 2017. 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 are comprised of cost-method equity investments and long-lived assets, including property, plant and equipment, intangible assets and goodwill. There were no such remeasurements to cost-method equity investments and property, plant and equipment for the year ended September 29, 2018. There were no impairments to assets measured using level 3 inputs in fiscal 2017 and 2016. Refer to Note 5 for disclosure of the nonrecurring fair value measurement related to the debt extinguishment losses recorded in fiscal 2018 , 2017 and 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, accounts payable and debt obligations. The carrying amounts of the Company’s cash and 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. 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 $1.76 billion and $225.0 million aggregate principal, respectively, as of September 29, 2018 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 2025 Senior Notes and 2028 Senior Notes had a fair values of approximately $909.6 million and $377.0 million as of September 29, 2018 based on their trading price, representing a Level 1 measurement. The Company's 2022 Senior Notes had a fair value of approximately $1.05 billion as of September 30, 2017 based on their trading price, representing a Level 1 measurement. The fair value of the Company’s Convertible Notes is based on the trading prices of the respective notes and represents a Level 1 measurement. The Convertible Notes were not outstanding as of September 29, 2018. The estimated fair values of the Company’s Convertible Notes at September 30, 2017 were as follows: 2017 2012 Notes 297.3 2013 Notes 244.4 $ 541.7

Income Taxes

Income Taxes	12 Months Ended
	Sep. 29, 2018
Income Tax Disclosure [Abstract]
Income Taxes	Income Taxes The Company’s income before income taxes consisted of the following: Years ended September 29, 2018 September 30, 2017 September 24, 2016 Domestic $ (581.9 ) $ 1,105.8 $ 310.7 Foreign 163.3 124.7 104.6 $ (418.6 ) $ 1,230.5 $ 415.3 The (benefit) provision for income taxes contained the following components: Years ended September 29, 2018 September 30, 2017 September 24, 2016 Federal: Current $ 137.1 $ 701.1 $ 209.0 Deferred (461.9 ) (276.9 ) (122.7 ) (324.8 ) 424.2 86.3 State: Current 11.0 53.1 16.6 Deferred (11.3 ) (15.9 ) (22.7 ) (0.3 ) 37.2 (6.1 ) Foreign: Current 21.9 13.9 14.7 Deferred (4.1 ) (0.3 ) (10.4 ) 17.8 13.6 4.3 $ (307.3 ) $ 475.0 $ 84.5 The income tax (benefit) provision differed from the tax (benefit) provision computed at the U.S. federal statutory rate due to the following: Years ended September 29, 2018 September 30, 2017 September 24, 2016 Income tax (benefit) provision at federal statutory rate (24.5 )% 35.0 % 35.0 % Increase (decrease) in tax resulting from: Domestic production activities deduction (3.1 ) (1.7 ) (5.0 ) State income taxes, net of federal benefit 0.7 2.3 2.0 Non-deductible goodwill 39.4 9.2 — Tax credits (1.9 ) (0.8 ) (3.2 ) Tax reform (82.7 ) — — Unrecognized tax benefits 1.8 (1.4 ) 2.4 Compensation 0.3 (0.5 ) 0.1 Foreign rate differential (5.2 ) (2.6 ) (6.1 ) Change in deferred tax rate 1.2 0.2 (1.8 ) Change in valuation allowance (0.5 ) (1.5 ) (3.4 ) Other 1.1 0.4 0.3 (73.4 )% 38.6 % 20.3 % On December 22, 2017, the U.S. government enacted the Tax Cuts and Jobs Act (the "Act"), which significantly revised the U.S. system of corporate taxation by, among other things, lowering the U.S. corporate income tax rate from 35% to 21%, implementing a new international tax system, broadening the tax base and imposing a tax on deemed repatriated earnings of foreign subsidiaries. The decrease in the U.S. federal corporate tax rate from 35% to 21% resulted in a blended statutory rate of 24.5% for the Company’s fiscal year 2018. The Company’s effective tax rate in fiscal 2018, applied to an overall pre-tax loss, resulting in a benefit, is higher than the statutory rate primarily due to the favorable impact of the Act, which required the Company to remeasure its U.S. net deferred tax liabilities at a lower rate, partially offset by the unfavorable impact of the Medical Aesthetic goodwill impairment charge, substantially all of which is non-deductible. 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 Act 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 Company recorded an estimated net income tax benefit of $346.2 million , representing the Company’s best estimate based on its interpretation of the Act. The $346.2 million income tax benefit is primarily related to the remeasurement of deferred tax assets and liabilities based on the tax rates at which they are expected to reverse in the future partially offset by additional tax expense pertaining to the deductibility of certain executive compensation pursuant to the Act. In the fourth quarter, the Company reduced the benefit related to the Act by $8.3 million primarily due to the impact of guidance issued during the quarter affecting the deductibility of certain executive compensation pursuant to the Act and the remeasurement of certain deferred tax assets and liabilities based on the tax rates at which they are expected to reverse in the future. The Company is still accumulating data regarding certain provisional tax estimates in order to finalize the underlying calculations and the U.S. Treasury is expected to issue further guidance on the application of certain provisions of the Act, which could further impact the effect of the Act on the Company’s financial statements. The Company's effective tax rate in fiscal 2017 was higher than the statutory rate primarily due to non-deductible goodwill related to the sale of the Blood Screening business, partially offset by the release of valuation allowances for capital losses utilized against the capital gain generated on the sale of the Blood Screening business, earnings in jurisdictions subject to lower tax rates, the domestic production activities deduction benefit, the release of reserves for uncertain tax positions due to statutes of limitations expirations and audit settlements, stock compensation benefits, and federal and state tax credits. The Company's effective tax rate in fiscal 2016 was lower than the statutory rate primarily due to earnings in jurisdictions subject to lower tax rates, the domestic production activities deduction benefit, and a change in the valuation allowance related to the sale of a marketable security with a higher tax than book basis. The Company uses the asset and liability method to account for income taxes in accordance with ASC 740, Income Taxes . Under this method, deferred income taxes are recognized for the future tax consequences of differences between the tax and financial accounting bases of assets and liabilities at each reporting period. Deferred income taxes are based on enacted tax laws and statutory tax rates applicable to the period in which these differences are expected to affect taxable income. A valuation allowance is established when necessary to reduce deferred tax assets to the amounts expected to be realized. The Company’s significant deferred tax assets and liabilities were as follows: September 29, 2018 September 30, 2017 Deferred tax assets Net operating loss carryforwards $ 30.9 $ 50.1 Capital losses 6.5 7.1 Non-deductible accruals 30.7 50.6 Non-deductible reserves 22.1 30.0 Stock-based compensation 24.0 39.3 Research and other credits 13.3 13.6 Nonqualified deferred compensation plan 12.3 16.4 Other temporary differences 11.5 16.5 151.3 223.6 Less: valuation allowance (25.5 ) (28.2 ) $ 125.8 $ 195.4 Deferred tax liabilities Depreciation and amortization $ (606.6 ) $ (1,071.5 ) Debt discounts and deferrals (4.5 ) (88.4 ) $ (611.1 ) $ (1,159.9 ) $ (485.3 ) $ (964.5 ) Under ASC 740, the Company can only recognize a deferred tax asset for the future benefit to the extent that it is “more likely than not” that these assets will be realized. After considering all available positive and negative evidence, the Company established a valuation allowance against specifically identified deferred tax assets because it is more-likely-than-not that these assets will not be realized. In making this determination, the Company considered numerous factors including historical profitability, estimated future taxable income and the character of such income. The valuation allowance decreased $2.7 million in fiscal 2018 from fiscal 2017 primarily due to tax reform and attribute expiration and utilization. At September 29, 2018 , the Company had $9.8 million , $46.9 million , and $35.9 million in gross federal, state, and foreign net operating losses, respectively, and $4.6 million , $9.4 million , and $1.2 million in federal, state, and foreign credit carryforwards, respectively. These losses and credits expire between 2019 and 2038 , except for $34.5 million in losses and $2.0 million in credits that have unlimited carryforward periods. The federal, state, and foreign net operating losses exclude $4.5 million , $85.1 million , and $46.4 million , respectively, in net operating losses, that the Company expects will expire unutilized. At September 29, 2018 , the Company had $89.5 million in gross unrecognized tax benefits excluding interest, of which $79.0 million , if recognized, would reduce the Company's effective tax rate. At September 30, 2017 , the Company had $90.3 million in gross unrecognized tax benefits excluding interest, of which $70.3 million , if recognized, would have reduced the Company's effective tax rate. The gross unrecognized tax benefits decreased by $0.8 million from fiscal 2017, of which $10.4 million was the reversal in fiscal 2018 of reserves for uncertain tax positions related to the convertible debt exchange that occurred in fiscal 2013 and $9.6 million was the net expense recorded to the income tax provision primarily from current year tax positions partially offset by audit settlements and the expiration of statutes of limitations. In the next twelve months it is reasonably possible that the Company will reduce its gross unrecognized tax benefits by up to $4.8 million due to expiring statutes of limitations. The Company’s unrecognized income tax benefits activity for fiscal 2018 and 2017 was as follows: 2018 2017 Balance at beginning of fiscal year $ 90.3 $ 163.6 Tax positions related to current year: Additions 9.0 21.8 Reductions — — Tax positions related to prior years: Additions related to change in estimate 6.6 1.1 Reductions (15.4 ) (77.3 ) Payments — (1.6 ) Lapses in statutes of limitations (1.4 ) (19.9 ) Acquired tax positions: Additions related to reserves acquired from acquisitions 0.4 2.6 Balance as of the end of the fiscal year $ 89.5 $ 90.3 The Company’s policy is to include accrued interest and penalties related to unrecognized tax benefits and income tax liabilities, when applicable, in income tax expense. As of September 29, 2018 and September 30, 2017 , gross accrued interest was $9.0 million and $5.3 million , respectively. At September 29, 2018 , no significant penalties have been accrued. The Company and its subsidiaries are subject to various federal, state, and foreign income taxes. The Company is undergoing a tax examination in the United Kingdom (fiscal year 2016). The Company’s U.S. Federal income tax returns are generally no longer subject to examination prior to tax year 2015; however, one federal income tax examination is ongoing for Cynosure Inc. and subsidiaries (fiscal years 2015-2017). State income tax returns are generally no longer subject to examination prior to fiscal year 2014. The Company is undergoing tax examinations in Massachusetts (fiscal years 2014-2015) and New York (fiscal years 2013-2015). During fiscal 2017, the Internal Revenue Service completed its audit for fiscal years 2013 and 2014. The Company made a cash payment of $1.7 million and recorded an income tax benefit of $10.9 million , including interest, related to the reversal of unrecognized tax benefits. Transition Tax

Stockholders' Equity and Stock-

Stockholders' Equity and Stock-Based Compensation	12 Months Ended
	Sep. 29, 2018
Disclosure of Compensation Related Costs, Share-based Payments [Abstract]
Stockholders' Equity and Stock-Based Compensation	Stockholders' Equity and Stock-Based Compensation Stock Repurchase Program On November 11, 2013, the Company announced that its Board of Directors authorized the repurchase of up to $250 million of the Company’s outstanding common stock over a three -year period. During fiscal 2016, the Company repurchased 7.3 million shares of its common stock for total consideration of $250.0 million . This share repurchase authorization was fully utilized. On June 21, 2016, the Company's Board of Directors authorized the repurchase of up to an additional $500.0 million of the Company's outstanding common stock over the next five years . During fiscal 2017, the Company repurchased 5.3 million shares of its common stock for total consideration of $200.1 million , and in fiscal 2018, the Company repurchased an additional 5.0 million shares of its common stock for a total consideration of $187.3 million under this authorization. On June 13, 2018, the Board of Directors authorized another share repurchase plan to repurchase up to $500.0 million of our outstanding common stock. This share repurchase plan, which replaces the prior plan, was effective August 1, 2018 and expires on June 13, 2023. Under this authorization, during the fourth quarter of 2018, the Company repurchased 2.3 million shares of its common stock for a total consideration of $88.5 million . As of September 28, 2019, $411.5 million was available under this authorization. Subsequent to September 29, 2018, the Company repurchased 1.5 million shares of its common stock for total consideration of $60.6 million . Stock-Based Compensation Equity Compensation Plans The Company has one share-based compensation plan pursuant to which awards are currently being issued—the 2008 amended and restated Equity Incentive Plan (“2008 Equity Plan”). The purpose of the 2008 Equity Plan is to provide stock options, restricted stock units and other equity interests in the Company to employees, officers, directors, consultants and advisors of the Company and any other person who is determined by the Board of Directors to have made (or is expected to make) contributions to the Company. The 2008 Equity Plan is administered by the Board of Directors of the Company, and a total of 31.5 million shares were reserved for issuance under this plan. As of September 29, 2018 , the Company had 8.6 million shares available for future grant under the 2008 Equity Plan. The following presents stock-based compensation expense in the Company’s Consolidated Statements of Operations in fiscal 2018 , 2017 and 2016 : 2018 2017 2016 Cost of revenues $ 8.3 $ 10.7 $ 10.5 Research and development 9.5 11.2 10.8 Selling and marketing 10.3 11.9 10.9 General and administrative 35.6 34.4 32.8 Restructuring and divestiture 1.3 — 0.4 $ 65.0 $ 68.2 $ 65.4 Grant-Date Fair Value The Company uses a binomial model to determine the fair value of its stock options. The Company considers a number of factors to determine the fair value of options including the assistance of an outside valuation adviser. Information pertaining to stock options granted during fiscal 2018 , 2017 and 2016 and related assumptions are noted in the following table: Years ended September 29, 2018 September 30, 2017 September 24, 2016 Options granted (in millions) 1.7 1.0 1.1 Weighted-average exercise price $ 40.76 $ 38.07 $ 39.32 Weighted-average grant date fair value $ 12.98 $ 12.33 $ 12.91 Assumptions: Risk-free interest rates 2.1 % 1.8 % 1.6 % Expected life (in years) 4.7 4.7 4.7 Expected volatility 35.3 % 36.6 % 37.8 % Dividend yield — — — The risk-free interest rate is based on a treasury instrument whose term is consistent with the expected life of the stock options. In projecting expected stock price volatility, the Company uses a combination of historical stock price volatility and implied volatility from observable market prices of similar equity instruments. The Company estimated the expected life of stock options based on historical experience using employee exercise and option expiration data. In connection with appointing Stephen P. MacMillan as the new President and Chief Executive Officer in December 2013, per the terms of his employment agreement, the Company granted 0.2 million restricted stock units ("RSUs") to match Mr. MacMillan’s purchase of 0.2 million shares of the Company’s common stock on the open market in the second quarter of fiscal 2014. The RSUs cliff vest three years from the date of grant, and the Company accounted for this grant as a liability award pursuant to ASC 718 because this RSU award contained an additional vesting condition (the requirement that Mr. MacMillan retain the matching shares during the vesting period) that was not service, performance or market based. As such, this award was marked-to-market at each reporting period and vested during fiscal 2017 at which time the liability of $7.8 million was reclassified to additional paid-in-capital. Stock-Based Compensation Expense Attribution The Company uses the straight-line attribution method to recognize stock-based compensation expense for stock options and RSUs. The vesting term of stock options is generally four or five years with annual vesting of 25% and 20% per year, respectively, on the anniversary of the grant date, and RSUs generally vest over three or four years with annual vesting at 33% and 25% per year, respectively, on the anniversary of the grant date. The amount of stock-based compensation recognized during a period is based on the value of the portion of the awards that are ultimately expected to vest. Under ASC 718, the Company has made an accounting policy to estimate forfeitures at the time awards are granted and revises, if necessary, in subsequent periods if actual forfeitures differ from those estimates. Based on an analysis of historical forfeitures, the Company has determined a specific forfeiture rate for certain employee groups and has applied forfeiture rates ranging from 0% to 7.0% as of September 29, 2018 depending on the specific employee group. This analysis is re-evaluated annually and the forfeiture rate will be adjusted as necessary. Ultimately, the actual stock-based compensation expense recognized will only be for those stock options and RSUs that vest. Stock-based compensation expense related to stock options was $14.3 million , $12.2 million , and $10.9 million in fiscal 2018 , 2017 and 2016 , respectively. Stock compensation expense related to stock units, including RSUs, performance stock units ("PSUs") and market stock units ("MSUs") was $46.5 million , $51.6 million , and $50.5 million in fiscal 2018 , 2017 and 2016 , respectively. The related tax benefit recorded in the Consolidated Statements of Operations was $11.7 million , $22.6 million and $23.1 million in fiscal 2018, 2017 and 2016 , respectively. At September 29, 2018 , there was $25.4 million and $58.7 million of unrecognized compensation expense related to stock options and RSUs, respectively, to be recognized over a weighted average period of 2.6 years and 1.9 years, respectively. Share Based Payment Activity The following table summarizes all stock option activity under the Company’s stock option plans for the year ended September 29, 2018 : Number of Shares (in millions) Weighted- Average Exercise Price Weighted- Average Remaining Contractual Life (in Years) Aggregate Intrinsic Value (in millions) Options outstanding at September 30, 2017 5.5 $ 28.15 5.4 $ 50.3 Granted 1.7 40.76 Canceled/ forfeited (0.4 ) 36.22 Exercised (0.8 ) 21.72 15.2 Options outstanding at September 29, 2018 6.0 $ 32.13 5.9 $ 53.3 Options exercisable at September 29, 2018 2.8 $ 26.47 3.7 $ 40.8 Options vested and expected to vest at September 29, 2018 (1) 5.9 $ 32.08 5.9 $ 52.8 (1) This represents the number of vested stock options as of September 29, 2018 plus the unvested outstanding options at September 29, 2018 expected to vest in the future, adjusted for estimated forfeitures. During fiscal 2017 and 2016 , the total intrinsic value of options exercised (i.e., the difference between the market price on the date of exercise and the price paid by the employee to exercise the options) was $25.9 million and $21.6 million , respectively. A summary of the Company’s RSU, PSU and MSU activity during the year ended September 29, 2018 is presented below: Non-vested Shares Number of Shares (in millions) Weighted-Average Grant-Date Fair Value Non-vested at September 30, 2017 3.0 $ 34.58 Granted 1.7 42.49 Vested (1.6 ) 34.10 Forfeited (0.4 ) 38.28 Non-vested at September 29, 2018 2.7 $ 40.02 The number of RSUs vested includes shares withheld on behalf of employees to satisfy minimum statutory tax withholding requirements. The Company pays the minimum statutory tax withholding requirement on behalf of its employees. During fiscal 2018 , 2017 and 2016 the total fair value of RSUs and PSUs vested was $38.9 million , $39.5 million and $28.4 million , respectively. Included in the above chart, the Company granted 0.6 million and 0.2 million and 0.3 million PSUs during fiscal 2018 , 2017 , and 2015, respectively, to members of the Company's senior management team, which includes additional shares issued upon achieving metrics within the performance criteria. Each recipient of the 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 year performance period provided the Company’s defined Return on Invested Capital metrics are achieved. These awards cliff-vest three years from the date of grant, and the Company recognizes compensation expense ratably over the required service period based on its estimate of the number of shares will vest upon achieving the measurement criteria. 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 MSUs during fiscal 2018 and 2017, respectively, to its senior management team. 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 year performance period based upon achieving a certain total shareholder return relative to a defined peer group. The MSUs were valued at $49.44 and $48.98 per share using the Monte Carlo simulation model in fiscal 2018 and 2017, respectively. These awards cliff-vest three years from the date of grant, and the Company recognizes compensation expense for the MSUs ratably over the service period. Employee Stock Purchase Plan The Hologic, Inc. 2012 Employee Stock Purchase Plan (“2012 ESPP”) provides for the granting of up to 2.5 million shares of the Company’s common stock to eligible employees. The 2012 ESPP plan period is semi-annual and allows participants to purchase the Company’s common stock at 85% of the lower of (i) the market value per share of the common stock on the first day of the offering period or (ii) the market value per share of the common stock on the purchase date. Stock-based compensation expense in fiscal 2018 , 2017 and 2016 was $4.0 million , $4.4 million and $4.0 million , respectively. The Company uses the Black-Scholes model to estimate the fair value of shares to be issued as of the grant date using the following weighted average assumptions: September 29, 2018 September 30, 2017 September 24, 2016 Assumptions: Risk-free interest rates 1.62 % 0.72 % 0.34 % Expected life (in years) 0.5 0.5 0.5 Expected volatility 25.0 % 24.9 % 27.2 % Dividend yield — — —

Profit Sharing 401(k) Plan

Profit Sharing 401(k) Plan	12 Months Ended
	Sep. 29, 2018
Defined Contribution Plan [Abstract]
Profit Sharing 401(k) Plan	Profit Sharing 401(k) Plan The Company has a qualified profit sharing plan covering substantially all of its employees. The Company made contributions of $18.6 million , $20.2 million and $16.2 million for fiscal 2018 , 2017 and 2016 , respectively.

Deferred Compensation Plan

Deferred Compensation Plan	12 Months Ended
	Sep. 29, 2018
Compensation Related Costs [Abstract]
Deferred Compensation Plan	Deferred Compensation Plans Nonqualified Deferred Compensation Plan Effective March 15, 2006, the Company adopted its DCP to provide non-qualified retirement benefits to a select group of executive officers, senior management and highly compensated employees of the Company. Eligible employees may elect to contribute up to 75% of their annual base salary and 100% of their annual bonus to the DCP and such employee contributions are 100% vested. In addition, the Company may elect to make annual discretionary contributions on behalf of participants in the DCP. Each Company contribution is subject to a three -year vesting schedule, such that each contribution vests one third annually. Employee contributions are recorded within accrued expenses. Upon enrollment into the DCP, employees make investment elections for both their voluntary contributions and discretionary contributions, if any, made by the Company. Earnings and losses on contributions based on these investment elections are recorded as a component of compensation expense in the period earned. Annually, the Compensation Committee of the Board of Directors has approved a discretionary cash contribution to the DCP for each year. Discretionary contributions by the Company to the DCP are held in a Rabbi Trust. The Company is recording compensation expense for the DCP discretionary contributions ratably over the three -year vesting period of each annual contribution, unless the participant meets the plan retirement provision of reaching a certain age and years of service criteria in which case the expense is accelerated to match the required service period to receive such benefit. Under the DCP, the Company recorded compensation expense related to Company contributions of $2.9 million , $3.4 million and $3.1 million in fiscal 2018 , 2017 and 2016 , respectively. The full amount of the discretionary contribution, net of forfeitures, along with employee deferrals is recorded within accrued expenses and totaled $49.8 million and $43.2 million at September 29, 2018 and September 30, 2017 , respectively. The Company has purchased Company-owned group life insurance contracts, in which both voluntary and discretionary Company DCP contributions are invested, to partially fund payment of the Company’s obligation to the DCP participants. The total amount invested at September 29, 2018 and September 30, 2017 was $44.2 million and $41.0 million , respectively. The values of these life insurance contracts are recorded in other long-term assets. Changes in the cash surrender value of life insurance contracts, which were not significant in fiscal 2018 , 2017 and 2016 , are recorded within other income (expense), net. Deferred Equity Plan Effective September 17, 2015, the Company adopted the Hologic, Inc. Deferred Equity Plan (the “DEP”). The DEP is designed to allow executives and non-employee Directors to accumulate Company stock in a tax-efficient manner to meet their long-term equity accumulation goals and shareholder ownership guidelines. Under the DEP, eligible participants may elect to defer the settlement of RSUs and PSUs granted under the 2008 Equity Plan until separation from service or separation from service plus a fixed number of years. Participants may defer settlement by vesting tranche. Although the equity will vest on schedule, if deferral of settlement is elected, no shares will be issued until the settlement date. The settlement date will be the earlier of death, disability, change in control of the Company or separation from service plus the number of years of deferral elected by the participant. While these shares upon vesting are not distributed to the individuals and are not outstanding, these shares will be included in basic weighted average shares outstanding used to calculate earnings per share.

Commitments and Contingencies

Commitments and Contingencies	12 Months Ended
	Sep. 29, 2018
Commitments and Contingencies Disclosure [Abstract]
Commitments and Contingencies	Commitments and Contingencies Finance Lease Obligations The Company has two non-cancelable lease agreements for buildings that are primarily used for manufacturing. The Company was responsible for a significant portion of the construction costs, and in accordance with ASC 840, Leases, Subsection 40-15-5, the Company was deemed to be the owner of the respective buildings during the construction period. At the completion of the construction period, the Company reviewed the lease for potential sale-leaseback treatment in accordance with ASC 840, Subsection 40, Sale-Leaseback Transactions. Based on its analysis, the Company determined that the lease did not qualify for sale-leaseback treatment. Therefore, the building, leasehold improvements and associated liabilities remain on the Company’s financial statements throughout the lease term, and the building and leasehold improvements are being depreciated on a straight line basis over their estimated useful lives of 35 years. The Company recorded the fair market value of the buildings and land aggregating $28.3 million within property and equipment on its Consolidated Balance Sheets. Depreciation expense related to the buildings and land is recorded within depreciation in the Company's Consolidated Statements of Cash Flows. During fiscal 2018, the Company executed an amendment to one of the leases extending the term to 2028. During fiscal 2016, the Company executed an amendment to other leases extending the term to 2024 , and a renewal option was removed. There were no other significant provisions to the terms of the lease agreements. At September 29, 2018 , the Company has recorded $1.6 million in accrued expenses and $34.7 million in other long-term liabilities related to these obligations. The current term of the leases is for a period of approximately 10 and 6 years, respectively, with the option to extend for one lease for two consecutive 5 -year terms and the other for one 5 -year term. Future minimum lease payments, including principal and interest, under these leases were as follows at September 29, 2018 : Fiscal 2019 $ 2.9 Fiscal 2020 3.0 Fiscal 2021 3.0 Fiscal 2022 3.1 Fiscal 2023 3.2 Thereafter 10.6 Total minimum payments 25.8 Less-amount representing interest (14.4 ) Total $ 11.4 As a result of the Cynosure acquisition, the Company has capital leases the for the buildings at its primary U.S. operating facility and certain equipment and vehicles with payments due through May 2028. Future minimum lease payments, including principal and interest, under these leases were as follows at September 29, 2018 : Fiscal 2019 $ 2.8 Fiscal 2020 2.8 Fiscal 2021 2.8 Fiscal 2022 3.0 Fiscal 2023 3.0 Thereafter 14.4 Total minimum lease payments $ 28.8 Less-amount representing interest (6.2 ) Present value of obligations under capital lease $ 22.6 Current portion of capital lease obligations 1.7 Capital lease obligations, net of current portion $ 20.9 Non-cancelable Purchase and Royalty Commitments The Company has certain non-cancelable purchase obligations primarily related to inventory purchases and diagnostics instruments, primarily Panther systems, and to a lesser extent other operating expense commitments. These obligations are not recorded in the Consolidated Balance Sheets. For reasons of quality assurance, sole source availability or cost effectiveness, certain key components and raw materials and instruments are available only from a sole supplier and the Company has certain long-term supply contracts to assure continuity of supply. At September 29, 2018 , non-cancelable purchase commitments are as follows: Fiscal 2019 $ 341.7 Fiscal 2020 3.1 Fiscal 2021 0.9 Total $ 345.7 Concentration of Suppliers The Company purchases certain components of its products from a single or small number of suppliers. A change in or loss of these suppliers could cause a delay in filling customer orders and a possible loss of sales, which could adversely affect results of operations; however, management believes that suitable replacement suppliers could be obtained in such an event. Operating Leases The Company conducts its operations in leased facilities under operating lease agreements that expire through fiscal 2035 . Substantially all of the Company’s lease agreements require the Company to maintain the facilities during the term of the lease and to pay all taxes, insurance, utilities and other costs associated with those facilities. The Company makes customary representations and warranties and agrees to certain financial covenants and indemnities. In the event the Company defaults on a lease, typically the landlord may terminate the lease, accelerate payments and collect liquidated damages. As of September 29, 2018 , the Company was not in default of any covenants contained in its lease agreements. Certain of the Company’s lease agreements provide for renewal options. Such renewal options are at rates similar to the current rates under the agreements. Future minimum lease payments under all of the Company’s operating leases at September 29, 2018 are as follows: Fiscal 2019 $ 21.0 Fiscal 2020 16.9 Fiscal 2021 13.9 Fiscal 2022 11.2 Fiscal 2023 6.7 Thereafter 17.9 Total $ 87.6 Rent expense, net of sublease income from these locations, was $23.1 million , $19.3 million , and $17.9 million for fiscal 2018 , 2017 and 2016 , respectively. The Company subleases a portion of a building it owns and some of its rented facilities and has received aggregate rental income of $2.6 million , $2.3 million and $2.4 million in fiscal 2018 , 2017 and 2016 , respectively, which has been recorded as an offset to rent expense. The future minimum annual rental income payments under these sublease agreements at September 29, 2018 are as follows: Fiscal 2019 $ 2.5 Fiscal 2020 1.8 Fiscal 2021 0.6 Fiscal 2022 0.6 Fiscal 2023 0.6 Thereafter 1.2 Total $ 7.3

Litigation and Related Matters

Litigation and Related Matters	12 Months Ended
	Sep. 29, 2018
Commitments and Contingencies Disclosure [Abstract]
Litigation and Related Matters	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, alleging 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 alleging 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 $4.0 million in damages. On June 27, 2013, the Court denied the Company’s motions related to inequitable conduct and allowed Smith & Nephew’s request for an 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. On January 30, 2018, the United States Court of Appeals for the Federal Circuit (“Court of Appeals”) issued a decision in the '459 patent appeal that affirmed as invalid the claims at issue and remanded the matter to the PTAB for further proceedings. On March 14, 2018, the Court of Appeals issued a decision in the ‘359 patent appeal that affirmed the PTAB ruling, holding that the claims at issue are not invalid. In a status report filed on June 18, 2018, Smith & Nephew notified the Court that it would not seek injunctive relief. On July 11, 2018, during a status conference, the Court invited the parties to file a supplemental briefing to address the impact of the ‘359 patent reexamination on liability issues and whether there is a need for a new trial on damages. On October 26, 2018, the parties entered into a Settlement and License Agreement to resolve the litigation. Under the agreement, in consideration of licenses, releases, non-asserts and other immunities granted by Smith & Nephew, the Company agreed to pay Smith & Nephew $34.8 million related to sales of the MyoSure tissue removal system through September 30, 2018, plus an ongoing royalty of 1% for such sales through September 26, 2020. The Company accrued the $34.8 million payment as a charge within general and administrative expenses in the fourth quarter of fiscal 2018, and the payment was made in the first quarter of fiscal 2019. On November 6, 2015, the Company filed a suit against Minerva Surgical, Inc. (“Minerva”) in the United States District Court for the District of Delaware, alleging that Minerva’s endometrial ablation device infringes U.S. Patents 6,872,183 (the '183 patent), 8,998,898 (the '898 patent) and 9,095,348 (the '348 patent). On January 25, 2016, the Company amended the complaint to include claims against Minerva for unfair competition, deceptive trade practices and tortious interference with business relationships. On February 5, 2016, the Company filed a second amended complaint to additionally allege that Minerva’s endometrial ablation device infringes U.S. Patent 9,247,989 (the '989 patent). On March 4, 2016, Minerva filed an answer and counterclaims against the Company, seeking declaratory judgment on the Company’s claims and asserting claims against the Company for unfair competition, deceptive trade practices, interference with contractual relationships, breach of contract and trade libel. On June 2, 2016, the Court denied the Company’s motion for a preliminary injunction on its patent claims and denied Minerva’s request for preliminary injunction related to the Company’s alleged false and deceptive statements regarding the Minerva product. On June 28, 2018, the Court granted the Company's summary judgment motions on infringement and no invalidity with respect to the ‘183 and ‘348 patents. The Court also granted the Company’s motion for summary judgment on assignor estoppel, which bars Minerva’s invalidity defenses or any reliance on collateral findings regarding invalidity from inter partes review proceedings. The Court also denied all of Minerva’s defenses, including its motions for summary judgment on invalidity, non-infringement, no willfulness, and no unfair competition. On July 27, 2018, after a two-week trial, a jury returned a verdict that: (1) awarded the Company $4.8 million in damages for Minerva’s infringement of the ‘183 and ‘348 patents; (2) found that Minerva’s infringement was not willful; and (3) found for the Company regarding Minerva’s counterclaims. Damages will continue to accrue until Minerva ceases its infringing conduct. Further, the Company will seek a permanent injunction prohibiting Minerva from selling infringing devices. On March 4, 2016, Minerva filed two petitions at the USPTO for inter partes review of the '348 patent. On September 12, 2016, the PTAB declined both petitions to review patentability of the ‘348 patent. On April 11, 2016, Minerva filed a petition for inter partes review of the '183 patent. On October 6, 2016, the PTAB granted the petition and instituted a review of the '183 patent. On December 15, 2017, the PTAB issued a final written decision invalidating all claims of the ‘183 patent. On February 9, 2018 the Company appealed this decision to the United States Court of Appeals for the Federal Circuit (“Court of Appeals”), which appeal is pending. On November 2, 2016, Minerva filed a petition for post-grant review of the '989 patent. On May 10, 2017, the PTAB granted the petition and instituted a review of the ‘989 patent. On May 8, 2018, the PTAB issued a final written decision invalidating all claims of the ‘989 patent. On July 10, 2018 the Company appealed this decision to the Court of Appeals. On April 11, 2017, 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 lost profits, price erosion and/or royalty. On January 5, 2018, the Court denied Minerva's motion for a preliminary injunction. On February 2, 2018, at the parties’ joint request, this action was transferred to the District of Delaware. Trial is scheduled for July 20, 2020. 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 January 30, 2012, and on March 6, 2012, Enzo Life Sciences, Inc. ("Enzo") filed suit against the Company and its 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), infringe Enzo’s U.S. Patent 6,992,180 (the '180 patent) and that products based on the Company's Invader chemistry platform infringe the '180 patent. On July 16, 2012, Enzo amended its complaint to include additional products that include HPA or TaqMan reagent chemistry. Both complaints sought preliminary and permanent injunctive relief and unspecified damages. On June 28, 2017, in ruling on the Company’s motion for summary judgment, the Court held that the '180 patent was invalid for nonenablement. On August 18, 2017, Enzo filed a notice of appeal with the Court of Appeals for the Federal Circuit, which appeal remains pending. 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, alleging that certain additional Company molecular diagnostic products also infringe the '180 patent. The complaint further alleges that certain of the Company’s molecular diagnostic productsusing 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. On March 30, 2016, the Company petitioned 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. 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. On November 29, 2017, Enzo appealed the PTAB decisions to the United States Court of Appeals for the Federal Circuit, which appeals remain pending. 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, alleging that products employing the Company’s proprietary target capture technologies infringe U.S. Patent 6,221,581 (the '581 patent). The Court granted Enzo’s motion to file an amended complaint adding Grifols Diagnostic Solutions Inc. and Grifols, S.A. (“Grifols”) as parties on November 9, 2017. On October 4, 2017, the Company filed for inter partes review of the ‘581 patent with the USPTO based on Enzo’s asserted claims. On April 18, 2018, the USPTO denied the Company’s petition for inter partes review. On May 18, 2018, the Company filed a request for rehearing of the USPTO denial order, which remains pending. On October 15, 2018, the Court issued a Memorandum Opinion and Order regarding claim construction of the '581 patent, ruling in favor of the Company and Grifols on nearly all disputed claim terms. On November 5, 2018, the Court entered final judgment in favor of the Company and Grifols following the filing of a Joint Stipulation of Noninfringement. Enzo intends to appeal the Court's claim construction ruling. 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 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(“MDNC”), alleging that the Company’s HIV products, including blood screening products previously manufactured by the Company for its former blood screening partner Grifols and Grifols Diagnostic Solutions Inc. (“Grifols USA”), infringe U.S. Patents 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. On June 9, 2017, the Company filed a supplemental motion to dismiss for improper venue. On January 3, 2018, the MDNC Court granted the parties’ consent motion to transfer the case to the United States District Court for the District of Delaware. On May 31, 2018, the Company filed a motion to sever and stay their arbitrable license defense. On September 25, 2018, the Court denied the Company’s motion to dismiss for failure to state a claim. The Company filed petitions for inter partes review of the asserted patents on February 6, 2018. The USPTO denied the Company’s petitions for inter partes review in August and September, 2018. The Company filed requests for rehearing of the denial orders, which requests are pending. 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 continues to be accrued as of September 28, 2018. 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 the Company. 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. On August 24, 2018, following the plaintiff’s counsel decision not to pursue the action, the parties filed a Stipulation of Dismissal with Prejudice to conclude the case. On June 26 and 28, 2017, the Company filed suit against FUJIFILM Corp., FUJIFILM Medical Systems USA, Inc., and FUJIFILM Techno Products Co., Ltd. (collectively “Fujifilm”) in the United States District Court for the District of Connecticut and the United States International Trade Commission (“ITC”), respectively, alleging that Fujifilm’s Aspire Cristalle mammography system infringes U.S. Patent Nos. 7,831,296; 8,452,379; 7,688,940; and 7,986,765. The Company seeks preliminary and permanent injunctions and an exclusion order against Fujifilm from making, using, selling, offering for sale, or importing into the United States allegedly infringing product and also seeks enhanced damages and interest. A hearing was held at the ITC before an Administrative Law Judge (“ALJ”) from April 9, 2018 to April 13, 2018. On July 26, 2018, the ALJ issued an initial determination finding that Fujifilm infringed all of the patents brought to trial and rejected Fujifilm’s defenses against these patents. The ALJ recommended an exclusion order that prevents the importation of infringing Fujifilm products into the United States, as well as a cease-and-desist order preventing the further sale and marketing of infringing Fujifilm products in the United States. A final determination by the ITC is scheduled to issue by January 25, 2019. On March 2, 2018, FUJIFILM Corporation and FUJIFILM Medical Systems U.S.A., Inc. (collectively “Fujifilm2”) filed suit against the Company in the United States District Court for the District of Delaware alleging that certain of the Company’s mammography systems infringe U.S. Patent Nos. 7,453,979; 7,639,779; RE44,367; and 8,684,948. Fujifilm2 further alleges that the Company violated United States antitrust laws and Delaware competition laws regarding the sale of certain of the Company’s mammography systems. Fujifilm2 seeks injunctive relief and unspecified monetary damages including statutory treble damages for certain claims. 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. 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.

Disposition

Disposition	12 Months Ended
	Sep. 29, 2018
Disposal Groups, Including Discontinued Operations and Collaborative Agreement [Abstract]
Disposition	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 Operations. 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 following two to three years depending on the nature of the respective service, including the manufacture of inventory. The Company has 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 noted 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 2 to 3 year period from the date of disposal. Income from operations of the disposed business prior to the divestiture for the years ended September 30, 2017 and September 24, 2016 was as follows: Years Ended September 30, 2017 September 24, 2016 Income from operations $ 45.8 $ 99.1 Under the long term supply agreement, transition services agreement to manufacture assays and research and development services, the Company recognized revenue of $55.4 million and $44.0 million , respectively, in fiscal 2018 and 2017. Prior Collaboration Agreement with Grifols Under its prior collaboration agreement with Grifols, the Company manufactured blood screening products, while Grifols was responsible for marketing, sales and service of those products, which Grifols sold under its trademarks. The Company was entitled to recover 50% of its manufacturing costs incurred in connection with the collaboration and received a percentage of the blood screening assay revenue generated under the collaboration. The Company’s share of revenue from assays it sold to Grifols was 50% . The Company recognized product revenue, and collaborative research and license revenue, which is included within services and other revenues, under the prior collaboration agreement. The Company recognized revenue of $96.5 million and $235.4 million under this collaboration agreement in fiscal 2017 and 2016 , respectively.

Business Segments and Geographi

Business Segments and Geographic Information	12 Months Ended
	Sep. 29, 2018
Segment Reporting [Abstract]
Business Segments and Geographic Information	Business Segments and Geographic Information The Company reports segment information in accordance with ASC 280, Segment Reporting. Operating segments are identified as components of an enterprise about which separate, discrete financial information is available for evaluation by the chief operating decision maker, or decision-making group, in making decisions about how to allocate resources and assess performance. The Company’s chief operating decision maker is its chief executive officer, and the Company’s reportable segments have been identified based on the types of products manufactured and the end markets to which the products are sold. Each reportable segment generates revenue from either the sale of medical equipment and related services and/or sale of disposable supplies, primarily used for diagnostic testing and surgical procedures. 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, goodwill and intangible asset impairment charges, transaction and integration expenses for acquisitions, restructuring, consolidation and divestiture charges, litigation charges, and other one-time or unusual items. Identifiable assets for the five reportable 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 intersegment revenues. Segment information for fiscal 2018 , 2017 , and 2016 was as follows: Years ended September 29, September 30, September 24, Total revenues: Diagnostics $ 1,147.4 $ 1,197.1 $ 1,236.9 Breast Health 1,218.2 1,138.3 1,112.8 Medical Aesthetics 339.1 207.5 — GYN Surgical 422.0 427.1 393.1 Skeletal Health 91.2 88.8 89.9 $ 3,217.9 $ 3,058.8 $ 2,832.7 Operating (loss) income: Diagnostics $ 145.5 $ 1,054.2 $ 126.0 Breast Health 399.7 373.4 350.5 Medical Aesthetics (844.7 ) (115.9 ) — GYN Surgical 58.3 65.0 69.1 Skeletal Health 3.3 (6.5 ) 3.0 $ (237.9 ) $ 1,370.2 $ 548.6 Depreciation and amortization: Diagnostics $ 257.3 $ 278.9 $ 341.8 Breast Health 22.7 19.7 22.6 Medical Aesthetics 108.1 54.2 — GYN Surgical 91.6 95.7 99.9 Skeletal Health 0.6 0.7 1.1 $ 480.3 $ 449.2 $ 465.4 Capital expenditures: Diagnostics $ 57.7 $ 50.9 $ 53.5 Breast Health 14.8 12.0 10.6 Medical Aesthetics 9.4 7.3 — GYN Surgical 13.1 15.2 17.7 Skeletal Health 3.3 1.2 0.4 Corporate 7.3 21.0 12.3 $ 105.6 $ 107.6 $ 94.5 September 29, September 30, September 24, Identifiable assets: Diagnostics $ 2,442.9 $ 2,621.6 $ 3,771.9 Breast Health 972.4 824.0 809.1 Medical Aesthetics 913.3 1,751.2 — GYN Surgical 1,414.9 1,494.6 1,570.7 Skeletal Health 30.3 25.5 30.9 Corporate 1,457.1 1,262.7 1,134.4 $ 7,230.9 $ 7,979.6 $ 7,317.0 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, the United Kingdom and Germany. 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: Years ended September 29, September 30, September 24, United States 75.1 % 77.6 % 78.9 % Europe 11.7 % 10.0 % 10.2 % Asia-Pacific 8.6 % 8.1 % 7.6 % Rest of world 4.6 % 4.3 % 3.3 % 100.0 % 100.0 % 100.0 % The Company’s property, plant and equipment, net are geographically located as follows: September 29, 2018 September 30, 2017 September 24, 2016 United States $ 366.5 $ 368.1 $ 362.4 Costa Rica 30.9 30.1 28.1 Europe 62.0 57.1 49.2 Rest of world 18.8 17.5 12.2 $ 478.2 $ 472.8 $ 451.9

Accrued Expenses and Other Long

Accrued Expenses and Other Long-Term Liabilities	12 Months Ended
	Sep. 29, 2018
Payables and Accruals [Abstract]
Accrued Expenses and Other Long-Term Liabilities	Accrued Expenses and Other Long-Term Liabilities Accrued expenses and other long-term liabilities consisted of the following: September 29, 2018 September 30, 2017 Accrued Expenses Compensation and employee benefits $ 196.0 $ 176.7 Income and other taxes 57.2 66.9 Other 182.9 131.7 $ 436.1 $ 375.3 September 29, 2018 September 30, 2017 Other Long-Term Liabilities Reserve for income tax uncertainties $ 92.6 $ 88.3 Accrued lease obligation—long-term 35.5 34.1 Pension liabilities 9.9 10.0 Other 19.6 7.8 $ 157.6 $ 140.2

Pension and Other Employee Bene

Pension and Other Employee Benefits	12 Months Ended
	Sep. 29, 2018
Retirement Benefits [Abstract]
Pension and Other Employee Benefits	Pension and Other Employee Benefits The Company has certain defined benefit pension plans covering the employees of its Hitec Imaging German subsidiary (the “Pension Benefits”). As of September 29, 2018 and September 30, 2017 , the Company’s pension liability was $9.7 million and $9.9 million , respectively, which is primarily recorded as a component of long-term liabilities in the Consolidated Balance Sheets. Under German law, there are no rules governing investment or statutory supervision of the pension plan. As such, there is no minimum funding requirement imposed on employers. Pension benefits are safeguarded by the Pension Guaranty Fund, a form of compulsory reinsurance that guarantees an employee will receive vested pension benefits in the event of insolvency. The pension plans were closed on December 31, 1997 and only eligible employees at that date could participate in the plans prior to closing to new participants. The tables below provide a reconciliation of benefit obligations, plan assets, funded status, and related actuarial assumptions of the Company’s German Pension Benefits. Change in Benefit Obligation Years ended September 29, 2018 September 30, 2017 September 24, 2016 Benefit obligation at beginning of year $ (9.9 ) $ (11.0 ) $ (10.0 ) Service cost — — — Interest cost (0.2 ) (0.1 ) (0.2 ) Plan participants’ contributions — — — Actuarial gain (loss) (0.1 ) 1.5 (1.2 ) Foreign exchange gain 0.2 (0.6 ) 0.1 Benefits paid 0.3 0.3 0.3 Benefit obligation at end of year (9.7 ) (9.9 ) (11.0 ) Plan assets — — — Benefit obligation at end of year $ (9.7 ) $ (9.9 ) $ (11.0 ) The tables below outline the components of the net periodic benefit cost and related actuarial assumptions of the Company’s German Pension Benefits. Components of Net Periodic Benefit Cost Years ended September 29, 2018 September 30, 2017 September 24, 2016 Service cost $ — $ — $ — Interest cost 0.2 0.1 0.4 Expected return on plan assets — — — Amortization of prior service cost — — Recognized net actuarial gain 0.1 0.4 (0.2 ) Net periodic benefit cost $ 0.3 $ 0.5 $ 0.2 Weighted-Average Net Periodic Benefit Cost Assumptions 2018 2017 2016 Discount rate 1.95 % 2.15 % 1.30 % Expected return on plan assets — % — % — % Rate of compensation increase — % — % — % The projected benefit obligation for the German Pension Benefits with projected benefit obligations in excess of plan assets was $9.7 million and $9.9 million at September 29, 2018 and September 30, 2017 , respectively, and the accumulated benefit obligation for the German Pension Benefits was $9.7 million and $9.9 million at September 29, 2018 and September 30, 2017 , respectively. The Company is also obligated to pay long-term service award benefits under the German Pension Benefits. The projected benefit obligation for long-term service awards was $0.1 million at both September 29, 2018 and September 30, 2017 , respectively. The table below reflects the total Pension Benefits expected to be paid for the German Pension Benefits each fiscal year as of September 29, 2018 : 2019 $ 0.4 2020 $ 0.4 2021 $ 0.4 2022 $ 0.4 2023 $ 0.4 2023 to 2027 $ 2.1 The Company also maintains additional contractual pension benefits for its top German executive officers in the form of a defined contribution plan. These contributions were insignificant in fiscal 2018 , 2017 and 2016 . Additionally, the Company has Swiss pension plans, which were insignificant in fiscal 2018 , 2017 , and 2016 .

Quarterly Statement of Operatio

Quarterly Statement of Operations Information (Unaudited)	12 Months Ended
	Sep. 29, 2018
Quarterly Financial Information Disclosure [Abstract]
Quarterly Statement of Operations Information (Unaudited)	Quarterly Statement of Operations Information (Unaudited) The following table presents a summary of quarterly results of operations for fiscal 2018 and 2017 : 2018 First Quarter Second Quarter Third Quarter Fourth Quarter Total revenue $ 791.1 $ 789.3 $ 824.0 $ 813.5 Gross profit 424.5 415.1 436.0 421.1 Net income (loss) (1) 406.7 (681.4 ) 112.9 50.5 Diluted net income (loss) per common share $ 1.45 $ (2.46 ) $ 0.41 $ 0.18 2017 First Quarter Second Quarter Third Quarter Fourth Quarter Total revenue $ 734.4 $ 715.4 $ 806.1 $ 802.9 Gross profit 404.8 388.7 409.6 417.9 Net income (2) 86.5 526.8 59.5 82.7 Diluted net income per common share $ 0.30 $ 1.84 $ 0.21 $ 0.29 (1) Net income in the first quarter of fiscal 2018 included the impact of implementing tax reform, which resulted in a provisional net tax benefit of $329.2 million . Net loss in the second quarter of fiscal 2018 included a goodwill impairment charge of $685.7 million , an in-process research and development intangible asset charge of $46.0 million and a debt extinguishment loss of $44.9 million . Net income in the fourth quarter of fiscal 2018 included a litigation settlement charge of $34.8 million . (2) Net income in the second quarter of fiscal 2017 included a gain on the sale of the blood screening business of $899.7 million and acquisition transaction expenses of $19.4 million .

Summary of Significant Accoun_2

Summary of Significant Accounting Policies (Policies)	12 Months Ended
	Sep. 29, 2018
Accounting Policies [Abstract]
Principles of Consolidation	Principles of Consolidation 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 Company’s fiscal year ends on the last Saturday in September. Fiscal 2018 , 2017 and 2016 ended on September 29, 2018 , September 30, 2017 and September 24, 2016 , respectively. Fiscal 2017 is a 53-week year and fiscal 2018 and 2016 were 52-week years.
Management's Estimates	Management’s Estimates and Uncertainties The preparation of financial statements in conformity with U.S. generally accepted accounting principles ("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. Significant estimates and assumptions by management affect the Company’s revenue recognition for multiple element arrangements, estimated fair value of cost-method equity investments, valuations, purchase price allocations and contingent consideration related to business combinations, expected future cash flows including growth rates, discount rates, terminal values and other assumptions and estimates used to evaluate the recoverability of long-lived assets and goodwill, estimated fair values of intangible assets and goodwill, amortization methods and periods, warranty reserves, certain accrued expenses, restructuring and other related charges, contingent liabilities, tax reserves, deferred tax rates and recoverability of the Company’s net deferred tax assets and related valuation allowances. Although the Company regularly assesses these estimates, actual results could differ materially from these estimates. Changes in estimates are recorded in the period in which they become known. The Company bases its estimates on historical experience and various other assumptions that it believes to be reasonable under the circumstances. The Company is subject to a number of risks similar to those of other companies of similar size in its industry, including dependence on third-party reimbursements to support the markets of the Company’s products, early stage of development of certain products, rapid technological changes, recoverability of long-lived assets (including intangible assets and goodwill), competition, stability of world financial markets, ability to obtain regulatory approvals, changes in the regulatory environment, limited number of suppliers, customer concentration, integration of acquisitions, substantial indebtedness, government regulations, management of international activities, protection of proprietary rights, patent and other litigation, dependence on contract manufacturers and dependence on key individuals.
Cash Equivalents	Cash Equivalents Cash equivalents are highly liquid investments with insignificant interest rate risk and maturities of three months or less at the time of acquisition.
Marketable Securities	Marketable Securities In the first quarter of fiscal 2018, the Company sold its remaining marketable security, which was an investment in the stock of a publicly traded company, for a realized loss of $0.6 million . The Company had classified its equity securities as available-for-sale and were recorded at fair value with the unrealized gains or losses, net of tax, recorded within accumulated other comprehensive loss. The Company's various investments were liquidated over the last few years. In connection with the acquisition of Cynosure, Inc. in fiscal 2017, the Company assumed $82.9 million of short and long-term marketable securities, which were classified as available-for-sale and primarily comprised of state and municipal bonds and U.S. treasury notes. During fiscal 2017, the Company liquidated these investments. In the first quarter of fiscal 2016, the Company sold all of its shares in one of its marketable securities and recorded a realized gain of $25.1 million in other income (expense), net. No material impairment charges were recorded in 2018, 2017, or 2016.
Concentrations of Credit Risk	Concentrations of Credit Risk Financial instruments that subject the Company to credit risk primarily consist of cash and cash equivalents, cost-method equity investments, and trade accounts receivable. The Company invests its cash and cash equivalents with high credit quality financial institutions. The Company’s customers are principally located in the United States, Europe and Asia. The Company performs ongoing credit evaluations of the financial condition of its customers and generally does not require collateral. Although the Company is directly affected by the overall financial condition of the healthcare industry, as well as global economic conditions, management does not believe significant credit risk exists as of September 29, 2018 . The Company generally has not experienced any material losses related to receivables from individual customers or groups of customers in the healthcare industry. The Company maintains an allowance for doubtful accounts based on accounts past due and historical collection experience. There were no customers with balances greater than 10% of accounts receivable as of September 29, 2018 and September 30, 2017 , or any customers that represented greater than 10% of consolidated revenues for fiscal years 2018 , 2017 and 2016
Inventories	Inventories Inventories are valued at the lower of cost or market on a first in, first out basis. Work-in-process and finished goods inventories consist of materials, labor and manufacturing overhead. The valuation of inventory requires management to estimate excess and obsolete inventory. The Company employs a variety of methodologies to determine the net realizable value of its inventory. Provisions for excess and obsolete inventory are primarily based on management’s estimates of forecasted sales, usage levels and expiration dates, as applicable for disposable products. A significant change in the timing or level of demand for the Company’s products compared to forecasted amounts may result in recording additional charges for excess and obsolete inventory in the future. The Company records charges for excess and obsolete inventory within cost of product revenues. Inventories consisted of the following: September 29, 2018 September 30, 2017 Raw materials $ 134.9 $ 95.7 Work-in-process 52.1 45.0 Finished goods 197.1 190.9 $ 384.1 $ 331.6
Property, Plant and Equipment	Property, Plant and Equipment Property, plant and equipment is recorded at cost less allowances for depreciation. The straight-line method of depreciation is used for all property and equipment. Property, plant and equipment consisted of the following: September 29, 2018 September 30, 2017 Equipment $ 391.9 $ 357.9 Equipment under customer usage agreements 399.6 368.7 Buildings and improvements 175.1 172.0 Leasehold improvements 63.0 60.6 Land 46.3 46.3 Furniture and fixtures 18.4 20.8 1,094.3 1,026.3 Less - accumulated depreciation and amortization (616.1 ) (553.5 ) $ 478.2 $ 472.8 Property, plant and equipment are depreciated over the following estimated useful lives: Asset Classification Estimated Useful Life Building and improvements 20–35 years Equipment 3–10 years Equipment under customer usage agreements 3–8 years Furniture and fixtures 5–7 years Leasehold improvements Shorter of the Original Term of Lease or Estimated Useful Life Equipment under customer usage agreements primarily consists of diagnostic instrumentation and imaging equipment located at customer sites but owned by the Company. Generally, the customer has the right to use the equipment for a period of time provided they meet certain agreed to conditions. The Company recovers the cost of providing the equipment from the sale of disposables. The depreciation costs associated with equipment under customer usage agreements are charged to cost of product revenues over the estimated useful life of the equipment. The costs to maintain the equipment in the field are charged to cost of product revenue as incurred.
Long-Lived Assets	Long-Lived Assets The Company reviews its long-lived assets, which includes property, plant and equipment and identifiable intangible assets (see below for discussion of intangible assets), for impairment whenever events or changes in circumstances indicate that the carrying amount of an asset may not be recoverable in accordance with ASC 360-10-35-15, Property, Plant and Equipment—Impairment or Disposal of Long-Lived Assets (ASC 360). Recoverability of these assets is evaluated by comparing the carrying value of the assets to the undiscounted cash flows estimated to be generated by those assets over their remaining economic life. If the undiscounted cash flows are not sufficient to recover the carrying value of the assets, the assets are considered impaired. The impairment loss is measured by comparing the fair value of the assets to their carrying value. Fair value is determined by either a quoted market price, if any, or a value determined by a discounted cash flow technique.
Business Combinations and Acquisition of Intangible Assets	Business Combinations and Acquisition of Intangible Assets The Company accounts for the acquisition of a business in accordance with ASC 805, Business Combinations (ASC 805). Amounts paid for each acquisition are allocated to the assets acquired and liabilities assumed based on their fair values at the date of acquisition. The Company determines the fair value of acquired intangible assets based on detailed valuations that use certain information and assumptions provided by management. The Company allocates any excess purchase price over the fair value of the net tangible and intangible assets acquired to goodwill. The Company uses the income approach to determine the fair value of developed technology and in-process research and development ("IPR&D") acquired in a business combination. This approach determines fair value by estimating the after-tax cash flows attributable to the respective asset over its useful life and then discounting these after-tax cash flows back to a present value. The Company bases its revenue assumptions on estimates of relevant market sizes, expected market growth rates, expected trends in technology and expected product introductions by competitors. Developed technology represents patented and unpatented technology and know-how. The value of the in-process projects is based on the project's stage of completion, the complexity of the work completed as of the acquisition date, the projected costs to complete, the contribution of core technologies and other acquired assets, the expected introduction date, the estimated cash flows to be generated upon commercial release and the estimated useful life of the technology. The Company believes that the estimated developed technology and IPR&D amounts represent the fair value at the date of acquisition and do not exceed the amount a third-party would pay for the assets. The Company also uses the income approach, as described above, to determine the estimated fair value of certain other identifiable intangible assets including customer relationships, distribution agreements, trade names and business licenses. Customer relationships represent established relationships with customers, which provide a ready channel for the sale of additional products and services. Trade names represent acquired company and product names, and distribution agreements generally pertain to exclusive distribution of certain products manufactured by third parties
Intangible Assets and Goodwill	Intangible Assets and Goodwill Intangible Assets Intangible assets are initially recorded at fair value and stated net of accumulated amortization and impairments. The Company amortizes its intangible assets that have finite lives using either the straight-line method, or if reliably determinable, based on the pattern in which the economic benefit of the asset is expected to be utilized. Amortization is recorded over the estimated useful lives ranging from 2 to 30 years. The Company evaluates the recoverability of its definite lived intangible assets whenever events or changes in circumstances or business conditions indicate that the carrying value of these assets may not be recoverable based on expectations of future undiscounted cash flows for each asset group. If the carrying value of an asset or asset group exceeds its undiscounted cash flows, the Company estimates the fair value of the assets, generally utilizing a discounted cash flow analysis based on the present value of estimated future cash flows to be generated by the assets using a risk-adjusted discount rate. To estimate the fair value of the assets, the Company uses market participant assumptions pursuant to ASC 820, Fair Value Measurements . Indefinite lived intangible assets, such as IPR&D assets, are required to be tested for impairment annually, or more frequently if indicators of impairment are present. The Company’s annual impairment test date is as of the first day of its fourth quarter. Intangible assets consisted of the following: September 29, 2018 September 30, 2017 Description Gross Carrying Value Accumulated Amortization Gross Carrying Value Accumulated Amortization Acquired intangible assets: Developed technology $ 4,573.3 $ 2,505.8 $ 4,528.7 $ 2,186.8 In-process research and development 5.5 — 46.0 — Customer relationships 556.5 428.1 552.8 393.8 Trade names 312.5 175.0 310.3 156.4 Distribution agreement 42.0 8.0 42.0 2.8 Non-competition agreements 1.5 0.5 1.5 0.1 Business licenses 2.4 2.2 2.4 2.2 Total acquired intangible assets $ 5,493.7 $ 3,119.6 $ 5,483.7 $ 2,742.1 Internal-use software 58.5 49.3 64.5 46.1 Capitalized software embedded in products 19.6 4.3 14.3 2.0 Total intangible assets $ 5,571.8 $ 3,173.2 $ 5,562.5 $ 2,790.2 During first quarter of fiscal 2018, the Company acquired Emsor S.A. and recorded $4.6 million of customer relationship intangible assets. In the fourth quarter of fiscal 2018, the Company acquired Faxitron Bipotics, LLC and recorded an aggregate of $53.4 million of intangible assets. During the second quarter of fiscal 2017, the Company divested its blood screening business and the net book value of $154.0 million of developed technology and $387.7 million of customer relationship assets were disposed of (see Note 13). In the second quarter of fiscal 2017, the Company acquired Cynosure and recorded an aggregate of $994.0 million of intangible assets (see Note 3). In the third quarter of fiscal 2017, the Company acquired Medicor and recorded $5.4 million of intangible assets. In addition, during the third quarter of fiscal 2017, the Company obtained CE approval for its last in-process research and development project acquired in the Gen-Probe Incorporated acquisition and transferred $3.7 million to developed technology. During the fourth quarter of fiscal 2017, the Company obtained regulatory approval for two of three projects from the Cynosure acquisition with an aggregate fair value of $61.0 million and these assets were reclassified to developed technology. The remaining project, which had an initial fair value of $46.0 million , was abandoned in the second quarter of fiscal 2018 due to unsuccessful clinical results. As a result, the Company recorded a $46.0 million impairment charge in the second quarter of fiscal 2018. The Company had identified certain software acquired in the Cynosure acquisition that would be abandoned in fiscal 2018 and shortened the useful life. As such, the Company accelerated depreciation of the asset resulting in an additional $5.9 million and $3.0 million of expense recorded in fiscal 2018 and 2017, respectively. Amortization expense related to developed technology is classified as a component of cost of product revenues—amortization of intangible assets. Amortization expense related to customer relationships, contracts, trade names, distribution agreements, and business licenses is classified as a component of amortization of intangible assets within operating expenses. The estimated amortization expense at September 29, 2018 for each of the five succeeding fiscal years was as follows: Fiscal 2019 $ 370.9 Fiscal 2020 $ 359.8 Fiscal 2021 $ 338.2 Fiscal 2022 $ 325.4 Fiscal 2023 $ 226.0 Goodwill In accordance with ASC 350, Intangibles—Goodwill and Other (ASC 350), the Company tests goodwill for impairment annually at the reporting unit level and between annual tests if events and circumstances indicate it is more likely than not that the fair value of a reporting unit is less than its carrying value. Events that could indicate impairment and trigger an interim impairment assessment include, but are not limited to, current economic and market conditions, including a decline in market capitalization, a significant adverse change in legal factors, business climate, operational performance of the business or key personnel, and an adverse action or assessment by a regulator. In performing the impairment test, the Company utilizes the two-step approach prescribed under ASC 350. The first step requires a comparison of the carrying value of each reporting unit to its estimated fair value. To estimate the fair value of its reporting units for Step 1, the Company primarily utilizes the income approach. The income approach is based on a DCF analysis and calculates the fair value by estimating the after-tax cash flows attributable to a reporting unit and then discounting the after-tax cash flows to present value using a risk-adjusted discount rate. Assumptions used in the DCF require significant judgment, including judgment about appropriate discount rates and terminal values, growth rates, and the amount and timing of expected future cash flows. The forecasted cash flows are based on the Company’s most recent budget and strategic plan and for years beyond this period, the Company’s estimates are based on assumed growth rates expected as of the measurement date. The Company believes its assumptions are consistent with the plans and estimates used to manage the underlying businesses. The discount rates used are intended to reflect the risks inherent in future cash flow projections and are based on estimates of the weighted-average cost of capital (“WACC”) of market participants relative to each respective reporting unit. The market approach considers comparable market data based on multiples of revenue or earnings before interest, taxes, depreciation and amortization (“EBITDA”) and is primarily used as a corroborative analysis to the results of the DCF analysis. The Company believes its assumptions used to determine the fair value of its reporting units are reasonable. If different assumptions were used, particularly with respect to forecasted cash flows, terminal values, WACCs, or market multiples, different estimates of fair value may result and there could be the potential that an impairment charge could result. Actual operating results and the related cash flows of the reporting units could differ from the estimated operating results and related cash flows. If the carrying value of a reporting unit exceeds its estimated fair value, the Company applies the single step approach under Accounting Standards Update No. 2017-04, Intangibles-Goodwill and Other (Topic 350): Simplifying the Test for Goodwill Impairment (ASU 2017-04). As a result of this simplified approach the goodwill impairment is calculated as the amount by which the carrying value of the reporting unit exceeds its fair value to the extent of the goodwill balance. The Company adopted this ASU in fiscal 2018. During the second quarter of fiscal 2018, in connection with commencing its company-wide annual budgeting and strategic planning process, evaluating its current operating performance of its Medical Aesthetics reporting unit, and abandoning an in-process research and development project, the Company reduced its short term and long term revenue and operating income forecasts and determined that indicators of impairment existed in its Medical Aesthetics reporting unit. The Medical Aesthetics reporting unit is solely comprised of the Cynosure business, which the Company acquired on March 22, 2017. The updated forecast reflected significantly reduced volume and market penetration projections resulting in lower short-term and long-term profitability than expected at the time of the Cynosure acquisition. As a result of these current events and circumstances, the Company determined that it was more likely than not that this change would reduce the fair value of the reporting unit below its carrying amount. To estimate the fair value of the reporting unit, the Company utilized the DCF analysis. The forecasted cash flows were based on the Company's most recent budget and strategic plan and for period beyond the strategic plan, the Company's estimates are based on assumed growth rates expected as of the measurement date. The Company believes its assumptions were consistent with the plans and estimates used to manage the underlying business. The discount rate used is intended to reflect the risks inherent in future cash flow projections and was based on an estimate of the weighted average cost of capital (WACC) of market participants relative to the reporting unit. The basis of fair value for Medical Aesthetics assumed the reporting unit would be purchased or sold in a non-taxable transaction, and the discount rate of 12.0% applied to the after-tax cash flows was consistent with that used in the purchase accounting performed in fiscal 2017. As a result of this analysis, the fair value of the Medical Aesthetic reporting unit was significantly below its carrying value, and the Company recorded a goodwill impairment charge of $685.7 million during the second quarter of fiscal 2018. This reporting unit now has a goodwill value of zero . Actual operating results and the related cash flows of the reporting units could differ from the estimated operating results and related cash flows. Due to the presence of impairment indicators, the Company also performed an impairment test of this reporting unit’s long-lived assets. This impairment evaluation was based on expectations of future undiscounted cash flows compared to the carrying value of the long-lived assets. The Company’s cash flow estimates were consistent with those used in the goodwill impairment test discussed above. Based on this analysis, the undiscounted cash flows of the Medical Aesthetics long-lived assets were in excess of their carrying value and thus deemed to not be impaired. The Company believes its procedures for estimating future cash flows were reasonable and consistent with market conditions at the time of estimation. The Company conducted its fiscal 2018 impairment test for its reporting units on the first day of the fourth quarter, and as noted above used DCF and market approaches to estimate the fair value of its reporting units as of July 1, 2018, and ultimately used the fair value determined by the DCF approach in making its impairment test conclusions. 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 this analysis, 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. For illustrative purposes, had the fair value of each of the reporting units been lower by 10% , all of the reporting units would still have passed Step 1 of the goodwill impairment test. At September 29, 2018 , the Company believes that its reporting units, with goodwill aggregating $2.5 billion , were not at risk of failing Step 1 of the goodwill impairment test based on its current forecasts. The Company conducted its fiscal 2017 and 2016 impairment tests on the first day of the respective year's fourth quarter, and as noted above used DCF and market approaches to estimate the fair value of its reporting units as of July 2, 2017 and June 26, 2016, respectively, and ultimately used the fair value determined by the DCF approach in making its impairment test conclusions. 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 under the applicable goodwill impairment standard at these dates was not required. A rollforward of goodwill activity by reportable segment from September 30, 2017 to September 29, 2018 is as follows: Diagnostics Breast Health Medical Aesthetics GYN Surgical Skeletal Health Total Balance at September 30, 2017 $ 823.0 $ 641.5 $ 683.5 $ 1,015.1 $ 8.1 $ 3,171.2 Faxitron acquisition — 41.6 — — — 41.6 Emsor acquisition — 5.7 — — — 5.7 Impairment charge — — (685.7 ) — — (685.7 ) Foreign currency and other adjustments (1.8 ) 0.7 2.2 (0.7 ) — 0.4 Balance at September 29, 2018 $ 821.2 $ 689.5 $ — $ 1,014.4 $ 8.1 $ 2,533.2
Other Assets	Other Assets Other assets consisted of the following: September 29, 2018 September 30, 2017 Other Assets Life insurance contracts $ 44.2 $ 41.0 Deferred tax assets 12.9 9.1 Cost-method equity investments 8.8 3.0 Manufacturing access fees 4.6 7.1 Other 27.2 24.5 $ 97.7 $ 84.7 Life insurance contracts were purchased in connection with the Company’s Nonqualified Deferred Compensation Plan (“DCP”) and are recorded at their cash surrender value (see Note 9 for further discussion).
Research and Software Development Costs	Research and Software Development Costs Costs incurred for the research and development of the Company’s products are expensed as incurred. Nonrefundable advance payments for goods or services to be received in the future by the Company for use in research and development activities are deferred. The deferred costs are expensed as the related goods are delivered or the services are performed. The Company accounts for the development costs of software embedded in the Company’s products in accordance with ASC 985, Software. Costs incurred in the research, design and development of software embedded in products to be sold to customers are charged to expense until technological feasibility of the ultimate product to be sold is established. The Company’s policy is that technological feasibility is achieved when a working model, with the key features and functions of the product, is available for customer testing. Software development costs incurred after the establishment of technological feasibility and until the product is available for general release are capitalized, provided recoverability is reasonably assured. Capitalized software development costs are amortized over their estimate useful life and recorded within cost of revenues - product.
Foreign Currency Translation	Foreign Currency Translation The financial statements of the Company’s foreign subsidiaries are translated in accordance with ASC 830, Foreign Currency Matters. The reporting currency for the Company is the U.S. dollar. The functional currency of the Company’s foreign subsidiaries is determined based on the guidance in ASC 830. The majority of the Company's foreign subsidiaries' functional currency is the applicable local currency, although certain of the Company's foreign subsidiaries' functional currency is the U.S. dollar based on the nature of their operations or functions. Assets and liabilities of subsidiaries whose functional currency is the local currency are translated at the exchange rate in effect at each balance sheet date. Before translation, the Company re-measures foreign currency denominated assets and liabilities, including inter-company accounts receivable and payable, into the functional currency of the respective entity, resulting in unrealized gains or losses recorded in other income, net in the Consolidated Statements of Operations. Revenues and expenses are translated using average exchange rates during the respective period. Foreign currency translation adjustments are accumulated as a component of other comprehensive income (loss) as a separate component of stockholders’ equity. Gains and losses arising from transactions denominated in foreign currencies are included in other income, net in the Consolidated Statements of Operations and were not significant in any of the reporting periods presented.
Accumulated Other Comprehensive Income	Accumulated Other Comprehensive Loss Other comprehensive income (loss) includes certain transactions that have generally been reported in the statement of stockholders’ equity. The following tables summarize the components and changes in accumulated balances of other comprehensive income for the periods presented: Year Ended September 29, 2018 Year Ended September 30, 2017 Foreign Currency Translation Marketable Securities Pension Plans Hedged Interest Rate Caps Total Foreign Currency Translation Marketable Securities Pension Plans Hedged Interest Rate Caps Total Beginning Balance $ (18.5 ) $ (0.4 ) $ (1.6 ) $ 4.3 $ (16.2 ) $ (26.1 ) $ (0.3 ) $ (2.5 ) $ (3.4 ) $ (32.3 ) Other comprehensive loss before reclassifications (8.1 ) — 0.5 (5.7 ) (13.3 ) 7.6 2.3 0.9 0.8 11.6 Charges (gains) reclassified to statement of operations — 0.4 — 3.6 4.0 — (2.4 ) — 6.9 4.5 Ending Balance $ (26.6 ) $ — $ (1.1 ) $ 2.2 $ (25.5 ) $ (18.5 ) $ (0.4 ) $ (1.6 ) $ 4.3 $ (16.2 ) In the first quarter of fiscal 2016, the Company sold all of its shares in one of its marketable securities and recorded a realized gain of $25.1 million in other income, net and resulted in reclassifying a $7.2 million gain out of accumulated other comprehensive loss to other income, net.
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, net in the Consolidated Statements of Operations. 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 rate interest on its credit facilities under the term loan feature of its credit facilities (see Note 5). 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. Certain of these cap agreements expired during fiscal 2017. During fiscal 2017, 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 5). 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. During fiscal 2018, 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 these interest rate cap agreements was $3.7 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 will end on December 30, 2018 and December 27, 2019 for the interest rate cap agreements entered into in fiscal 2017 and fiscal 2018, respectively. As of September 29, 2018 , 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 Loss as a component of AOCI. During fiscal 2018 , 2017 and 2016, interest expense of $3.6 million , $6.9 million and $3.9 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 approximately $3.1 million from AOCI to the Consolidated Statements of Operations in the next twelve months. The aggregate fair value of these interest rate caps was $7.7 million and $4.8 million at September 29, 2018 and September 30, 2017 , respectively, and is included in both Prepaid expenses and other current assets and Other assets on the Company’s Consolidated Balance Sheet. Refer to Note 6 “Fair Value Measurements” below 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, the Chinese Yuan 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 did not elect hedge accounting for these forward foreign currency contracts; 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, net. During fiscal 2018 , 2017 and 2016, the Company recorded net realized losses of $1.3 million , and net realized gains of $3.1 million and $1.5 million , respectively from settling forward foreign currency contracts, and net unrealized gains of $6.6 million and net unrealized losses of $3.6 million and $1.1 million in fiscal 2018, 2017 and 2016, respectively, on outstanding contracts. As of September 30, 2018, the Company had outstanding forward foreign currency contracts that were not designated for hedge accounting and are used to hedge fluctuations in the U.S dollar of forecasted transactions denominated in the Euro, UK Pound, Australian Dollar, Canadian Dollar, Chinese Yuan and Japanese Yen with a notional amount of $288.4 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 September 29, 2018 : Balance Sheet Location September 29, 2018 September 30, 2017 Assets: Derivative instruments designated as a cash flow hedge: Interest rate cap agreements Prepaid expenses and other current assets $ 6.0 $ 3.6 Interest rate cap agreements Other Assets 1.7 1.2 $ 7.7 $ 4.8 Derivatives not designated as hedging instruments: Forward foreign currency contracts Prepaid expenses and other current assets $ 3.2 $ 0.4 Liabilities: Derivatives not designated as hedging instruments: Forward foreign currency contracts Accrued expenses $ 0.2 $ 4.0 The following table presents the unrealized (gain) loss recognized in AOCI related to the interest rate caps for the following reporting periods: Year Ended Year Ended Year Ended Amount of (gain) loss recognized in other comprehensive (loss) income, net of taxes: Interest rate cap agreements $ (5.7 ) $ 0.8 $ (3.4 ) The following table presents the adjustment to fair value (realized and unrealized) recorded within the Consolidated Statements of Operations for derivative instruments for which the Company did not elect hedge accounting: Derivatives not classified as hedging instruments Location of Gain Recognized in Income Year Ended Year Ended Year Ended Forward foreign currency contracts $ 5.3 $ 0.5 $ 0.4 Other income, net
Revenue Recognition	Revenue Recognition The Company generates revenue from the sale of its products, primarily medical imaging systems, aesthetic treatment systems and diagnostic and surgical disposable products, and related services, which are primarily support and maintenance services on its medical imaging systems. The Company recognizes product revenue upon shipment provided that there is persuasive evidence of an arrangement, there are no uncertainties regarding acceptance, the sales price is fixed or determinable, and collection of the resulting receivable is reasonably assured. Generally, the Company’s product arrangements for capital equipment sales, primarily in its Breast Health, Medical Aesthetics and Skeletal Health reporting segments, are multiple-element arrangements, including services, such as installation, training and support and maintenance, and multiple products. Based on the terms and conditions of the product arrangements, the Company believes that these services and undelivered products can be accounted for separately from the delivered product element as the Company’s delivered products have value to its customers on a stand-alone basis. Accordingly, revenue for services not yet performed at the time of product delivery are deferred and recognized as such services are performed. The relative selling price of any undelivered products is also deferred at the time of shipment and recognized as revenue when these products are delivered. There is no customer right of return in the Company’s sales agreements for its capital equipment. Service revenues primarily consist of amounts recorded under service and maintenance contracts and repairs not covered under warranty, installation and training, and shipping and handling costs billed to customers. Service and maintenance contract revenues are recognized ratably over the term of the contract. Other service revenues are recognized as the services are completed using the specific performance method. Service and other revenue also includes royalties which are recognized in the period the payments are due to the Company. For revenue arrangements with multiple deliverables, the Company records revenue as separate units of accounting if the delivered items have value to the customer on a stand-alone basis and the delivery or performance of the undelivered items is considered probable and substantially within the Company’s control. Some of the Company’s products have both software and non-software components that function together to deliver the product’s essential functionality. The Company determined that except for its computer-aided detection (“CAD”) products and C-View and Intelligent 2D products, the software element in its other products is not within the scope of the software revenue recognition rules, ASC 985-605, Software—Revenue Recognition . The Company determined that given the significance of the software component’s functionality to its CAD, C-View and Intelligent 2D components, which are sold by its Breast Health segment, these products are within the scope of the software revenue recognition rules. The Company evaluated the appropriate revenue recognition treatment of it hardware products, including its Dimensions digital mammography systems, which have both software and non-software components that function together to deliver the products’ essential functionality (i.e., it is a tangible product), and determined they are not within the scope of ASC 985-605. The Company is required to allocate revenue to its multiple element arrangements based on the relative fair value of each element’s selling price. The Company typically determines the selling price of its products based on its best estimate of selling prices (“ESP”) and services based on vendor-specific objective evidence of selling price (“VSOE”). The Company determines VSOE based on its normal pricing and discounting practices for the specific product or service when sold on a stand-alone basis. In determining VSOE, the Company’s policy requires a substantial majority of selling prices for a product or service to be within a reasonably narrow range. The Company also considers the class of customer, method of distribution, and the geographies into which its products and services are sold when determining VSOE. If VSOE cannot be established, which may occur in instances when a product or service has not been sold separately, stand-alone sales are too infrequent, or product pricing is not within a relatively narrow range, the Company will generally establish the selling price using ESP to allocate arrangement consideration. The objective of ESP is to determine the price at which the Company would typically transact a stand-alone sale of the product or service. ESP is determined by considering a number of factors including Company pricing policies, internal costs and gross margin objectives, method of distribution, information gathered from experience in customer negotiations, market research and information, recent technological trends, competitive landscape and geographies. For those arrangements accounted for under the software revenue recognition rules, ASC 985-605 generally requires revenue earned on software arrangements involving multiple elements to be allocated to each element based on their relative VSOE of fair value. If VSOE does not exist for a delivered element, the residual method is applied in which the arrangement consideration is allocated to the undelivered elements based on their VSOE with the remaining consideration recognized as revenue for the delivered elements. For multiple-element software arrangements where VSOE of fair value of Post-Contract Customer Support (“PCS”) has been established, the Company recognizes revenue using the residual method at the time all other revenue recognition criteria have been met. Within its Diagnostics segment, the Company manufactured blood screening products according to demand schedules provided by its former collaboration partner, Grifols, S.A. (“Grifols”). In the second quarter of fiscal 2017, the Company sold its assets in the blood screening business to Grifols. 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 for the Company to provide 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, and the Company is in effect serving as a contract manufacturer of assays to Grifols for a two to three year period. The Company also agreed to sell Panther instrumentation and certain supplies to Grifols as part of a long term supply agreement. As such, the Company will generate a level of revenues, but much lower than historical trends prior to fiscal 2017. Prior to the divestiture, the Company’s agreement provided that it would share a portion of Grifols’s revenue from screening blood donations. Upon shipment to Grifols, the Company recognized product revenue at an agreed upon fixed transfer price, which was not refundable, and recorded the related cost of products sold. Based on the terms of the Company’s prior collaboration agreement with Grifols, the Company’s ultimate share of the net revenue from sales to the end user in excess of the transfer price was not known until it was reported to the Company by Grifols. On a monthly basis, Grifols reported net revenue generated during the prior month and remitted an additional corresponding net payment to the Company, which was recorded as revenue at that time. This payment combined with the transfer price revenues previously recognized represented the Company’s ultimate share of net revenue under the prior agreement. While the majority of its instruments are placed at customer sites, in certain instances the Company sells instruments to its clinical diagnostics customers and records sales of these instruments upon shipment or delivery, depending on the terms of the arrangement. Within its Diagnostics business, and to a lesser extent, its GYN Surgical business, the Company provides its instrumentation (for example, the ThinPrep Processor, ThinPrep Imaging System, and the Panther and Tigris systems) and certain other hardware to customers without requiring them to purchase the equipment or enter into a lease. The Company installs the instrumentation or equipment at the customer’s site and recovers the cost of providing the instrumentation or equipment in the amount it charges for its diagnostic tests, assays and other disposables. Customers enter into a customer usage agreement and typically commit to purchasing minimum quantities of disposable products at a stated price over a defined contract term, which is typically between three and five years. Revenue is recognized over the term of the customer usage agreement as tests, assays and other disposable products are shipped or delivered, depending on the customer's arrangement.
Accounts Receivable and Reserves	Accounts Receivable and Reserves The Company records reserves for doubtful accounts based upon a specific review of all outstanding invoices, known collection issues and historical experience. The Company regularly evaluates the collectability of its trade accounts receivables and performs ongoing credit evaluations of its customers and adjusts credit limits based upon payment history and its assessment of the customer’s current credit worthiness. Accounts receivable reserve activity for fiscal 2018 , 2017 and 2016 was as follows: Balance at Beginning of Period Charged to Costs and Expenses Write- offs and Payments Balance at End of Period Period Ended: September 29, 2018 $ 9.8 $ 7.0 $ (0.6 ) $ 16.2 September 30, 2017 $ 12.7 $ 1.8 $ (4.7 ) $ 9.8 September 24, 2016 $ 11.1 $ 2.0 $ (0.4 ) $ 12.7
Cost of Service and Other Revenues	Cost of Service and Other Revenues Cost of service and other revenues primarily represents payroll and related costs associated with the Company’s professional services’ employees, consultants, infrastructure costs and overhead allocations, including depreciation, rent and materials consumed in providing the service.
Stock-Based Compensation	Stock-Based Compensation The Company accounts for share-based payments in accordance with ASC 718, Stock Compensation (ASC 718) . As such, all share-based payments to employees, including grants of stock options, restricted stock units, performance stock units and market stock units and shares issued under the Company’s employee stock purchase plan, are recognized in the Consolidated Statements of Operations based on their fair values on the date of grant. In addition as a result of the adoption of ASU 2016-09 in fiscal 2017, all excess tax benefits and deficiencies are recognized as a component of the provision for income taxes on a discrete basis in the period in which the equity awards vest and/or are settled.
Net Income Per Share	Net (Loss) Income Per Share Basic net (loss) income per share is computed by dividing net income by the weighted average number of common shares outstanding. Diluted net income per share is computed by dividing net income by the weighted average number of common shares and the dilutive effect of potential future issuances of common stock from outstanding stock options, restricted stock units and convertible debt for the period outstanding determined by applying the treasury stock method. In accordance with ASC 718, the assumed proceeds under the treasury stock method include the average unrecognized compensation expense of in-the-money stock options and restricted stock units. This results in the assumed buyback of additional shares, thereby reducing the dilutive impact of equity awards. The Company applied the provisions of ASC 260, Earnings Per Share, Subsection 10-45-44, to determine the diluted weighted average shares outstanding as it related to its convertible notes, and due to the type of debt instrument issued and its accounting policy, the Company applied the treasury stock method and not the if-converted method. The dilutive impact of the Company’s convertible notes was based on the difference between the Company’s current period average stock price and the conversion price of the convertible notes, provided there was a premium. As such, dilution related to the conversion premium on the 2010 Notes, 2012 Notes and 2013 Notes was included in the calculation of diluted weighted-average shares outstanding in all years 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.
Product Warranties	Product Warranties The Company generally offers a one -year warranty for its products. The Company provides for the estimated cost of product warranties at the time product revenue is recognized. Factors that affect the Company’s warranty reserves include the number of units sold, historical and anticipated rates of warranty repairs and the cost per repair. The Company periodically assesses the adequacy of the warranty reserve and adjusts the amount as necessary. Product warranty activity for fiscal 2018 and 2017 was as follows: Balance at Beginning of Period Acquired Provisions Settlements/ Adjustments Balance at End of Period Period ended: September 29, 2018 $ 17.0 $ — $ 18.3 $ (19.4 ) $ 15.9 September 30, 2017 $ 5.0 $ 9.9 $ 15.3 $ (13.2 ) $ 17.0
Advertising Costs	Advertising Costs Advertising costs are charged to operations as incurred. The Company does not have any direct-response advertising. Advertising costs, which include trade shows and conventions, were approximately $26.9 million , $22.5 million and $20.2 million for fiscal 2018 , 2017 and 2016 , respectively, and were included in selling and marketing expense in the Consolidated Statements of Income.
Recently Issued Accounting Pronouncements	Recently Adopted Accounting Pronouncements In August 2018, the FASB issued Accounting Standards Update No. 2018-15, Intangibles-Goodwill and Other - Internal Use Software (Subtopic 350-40): Customer's Accounting for Implementation Costs Incurred in a Cloud Computing Arrangement That is a Service Contract (ASU 2018-15). This guidance reduces diversity in practice and requires companies to apply the internal-use software guidance in ASC 350-40 to implementation costs incurred in a hosting arrangement that is a service contract to determine whether to capitalize certain implementation costs or expense them as incurred. The amendments in the update are effective for annual periods beginning after December 15, 2019, and is applicable to the Company in fiscal 2021. Early adoption is allowed, and the Company adopted ASU 2018-15 in the fourth quarter of fiscal 2018. The adoption of this standard had an immaterial impact. In January 2017, the FASB issued Accounting Standards Update No. 2017-04, Intangibles-Goodwill and Other (Topic 350): Simplifying the Test for Goodwill Impairment (ASU 2017-04). 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. This ASU is effective for annual periods beginning after December 15, 2019, and is applicable to the Company in fiscal 2021. Early adoption is allowed, and the Company adopted ASU 2017-04 in the second quarter of fiscal 2018. The Company applied this standard to the interim goodwill impairment test it performed on its Medical Aesthetics reporting unit in the second quarter of fiscal 2018. The interim goodwill impairment test is more fully described in Note 14. In December 2016, the FASB issued Accounting Standard 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 and reclassified $18.4 million of internal-use software from property, plant, and equipment to intangible assets as of September 30, 2017. Additionally, the Company reclassified $12.3 million of capitalized software embedded in its products from other assets to intangible assets as of September 30, 2017. Recently Issued Accounting Pronouncements In August 2018, the FASB issued ASU No. 2018-13, Fair Value Measurement (Topic 820) . The guidance modifies disclosure requirements for fair value measurements under ASC 820. The guidance is effective for annual periods beginning after December 15, 2019, and is applicable to the Company in fiscal 2021. 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 2018-13 on its consolidated financial position and results of operations. In July 2018, the FASB issued ASU No. 2018-09 , Codification Improvements . The guidance provides clarifications and improvements to the Codification to help eliminate inconsistencies or incorrect application of various standards. The transition and effective date guidance is based on the facts and circumstances of each amendment. However, many of the amendments in ASU 2018-09 are effective for annual periods beginning after December 15, 2018, and are applicable to the Company in fiscal 2020. The Company is currently evaluating the impact of the adoption of ASU 2018-09 on its consolidated financial position and results of operations. 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. In July 2018, the FASB issued ASU No. 2018-10, Codification Improvements to Topic 842, Leases , to clarify specific guidance issued in ASC 2016-02. The guidance for both ASU 2016-02 and ASU 2018-10 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 and ASU 2018-10 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 (e.g. cost method investments), 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, and has been subsequently updated. 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. Topic 606 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. Topic 606, as amended, 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 using the modified retrospective method effective September 30, 2018. The Company is in the process of completing its evaluation of the anticipated impact of the adoption of this standard on its consolidated financial position and results of operations. As a result of its implementation efforts to date, the Company believes the most significant effect of adopting Topic 606 will be to transactions which have historically been deferred as a result of extended payment terms (i.e., the fees were not fixed or determinable) and collectability concerns under ASC 605. Under the ASC 606, the Company expects that it will be able to estimate the transaction price, subject to a constraint if the Company determines it is probable a significant revenue reversal may occur in the future. The Company believes in many cases this will result in revenue being recognized earlier upon the satisfaction of performance obligations to which the transaction price is allocated. Upon adoption of Topic 606, the Company will provide additional disclosures in the notes to the consolidated financial statements for the first quarter of fiscal 2019.

Summary of Significant Accoun_3

Summary of Significant Accounting Policies (Tables)	12 Months Ended
	Sep. 29, 2018
Accounting Policies [Abstract]
Supplemental Cash Flow Statement Information	Supplemental Cash Flow Statement Information Years ended September 29, 2018 September 30, 2017 September 24, 2016 Cash paid during the period for income taxes $ 178.2 $ 867.8 $ 184.8 Cash paid during the period for interest $ 122.1 $ 102.4 $ 104.0
Schedule of Inventories	Inventories consisted of the following: September 29, 2018 September 30, 2017 Raw materials $ 134.9 $ 95.7 Work-in-process 52.1 45.0 Finished goods 197.1 190.9 $ 384.1 $ 331.6
Schedule of Property, Plant and Equipment	Property, plant and equipment consisted of the following: September 29, 2018 September 30, 2017 Equipment $ 391.9 $ 357.9 Equipment under customer usage agreements 399.6 368.7 Buildings and improvements 175.1 172.0 Leasehold improvements 63.0 60.6 Land 46.3 46.3 Furniture and fixtures 18.4 20.8 1,094.3 1,026.3 Less - accumulated depreciation and amortization (616.1 ) (553.5 ) $ 478.2 $ 472.8 Property, plant and equipment are depreciated over the following estimated useful lives: Asset Classification Estimated Useful Life Building and improvements 20–35 years Equipment 3–10 years Equipment under customer usage agreements 3–8 years Furniture and fixtures 5–7 years Leasehold improvements Shorter of the Original Term of Lease or Estimated Useful Life
Schedule of Intangible Assets	Intangible assets consisted of the following: September 29, 2018 September 30, 2017 Description Gross Carrying Value Accumulated Amortization Gross Carrying Value Accumulated Amortization Acquired intangible assets: Developed technology $ 4,573.3 $ 2,505.8 $ 4,528.7 $ 2,186.8 In-process research and development 5.5 — 46.0 — Customer relationships 556.5 428.1 552.8 393.8 Trade names 312.5 175.0 310.3 156.4 Distribution agreement 42.0 8.0 42.0 2.8 Non-competition agreements 1.5 0.5 1.5 0.1 Business licenses 2.4 2.2 2.4 2.2 Total acquired intangible assets $ 5,493.7 $ 3,119.6 $ 5,483.7 $ 2,742.1 Internal-use software 58.5 49.3 64.5 46.1 Capitalized software embedded in products 19.6 4.3 14.3 2.0 Total intangible assets $ 5,571.8 $ 3,173.2 $ 5,562.5 $ 2,790.2
Schedule of Estimated Amortization Expense	The estimated amortization expense at September 29, 2018 for each of the five succeeding fiscal years was as follows: Fiscal 2019 $ 370.9 Fiscal 2020 $ 359.8 Fiscal 2021 $ 338.2 Fiscal 2022 $ 325.4 Fiscal 2023 $ 226.0
Rollforward of Goodwill Activity by Reportable Segment	A rollforward of goodwill activity by reportable segment from September 30, 2017 to September 29, 2018 is as follows: Diagnostics Breast Health Medical Aesthetics GYN Surgical Skeletal Health Total Balance at September 30, 2017 $ 823.0 $ 641.5 $ 683.5 $ 1,015.1 $ 8.1 $ 3,171.2 Faxitron acquisition — 41.6 — — — 41.6 Emsor acquisition — 5.7 — — — 5.7 Impairment charge — — (685.7 ) — — (685.7 ) Foreign currency and other adjustments (1.8 ) 0.7 2.2 (0.7 ) — 0.4 Balance at September 29, 2018 $ 821.2 $ 689.5 $ — $ 1,014.4 $ 8.1 $ 2,533.2
Schedule of Other Assets	Other assets consisted of the following: September 29, 2018 September 30, 2017 Other Assets Life insurance contracts $ 44.2 $ 41.0 Deferred tax assets 12.9 9.1 Cost-method equity investments 8.8 3.0 Manufacturing access fees 4.6 7.1 Other 27.2 24.5 $ 97.7 $ 84.7
Changes in accumulated balances of other comprehensive income	The following tables summarize the components and changes in accumulated balances of other comprehensive income for the periods presented: Year Ended September 29, 2018 Year Ended September 30, 2017 Foreign Currency Translation Marketable Securities Pension Plans Hedged Interest Rate Caps Total Foreign Currency Translation Marketable Securities Pension Plans Hedged Interest Rate Caps Total Beginning Balance $ (18.5 ) $ (0.4 ) $ (1.6 ) $ 4.3 $ (16.2 ) $ (26.1 ) $ (0.3 ) $ (2.5 ) $ (3.4 ) $ (32.3 ) Other comprehensive loss before reclassifications (8.1 ) — 0.5 (5.7 ) (13.3 ) 7.6 2.3 0.9 0.8 11.6 Charges (gains) reclassified to statement of operations — 0.4 — 3.6 4.0 — (2.4 ) — 6.9 4.5 Ending Balance $ (26.6 ) $ — $ (1.1 ) $ 2.2 $ (25.5 ) $ (18.5 ) $ (0.4 ) $ (1.6 ) $ 4.3 $ (16.2 )
Schedule of Derivative Instruments on the Consolidated Balance Sheets	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 September 29, 2018 : Balance Sheet Location September 29, 2018 September 30, 2017 Assets: Derivative instruments designated as a cash flow hedge: Interest rate cap agreements Prepaid expenses and other current assets $ 6.0 $ 3.6 Interest rate cap agreements Other Assets 1.7 1.2 $ 7.7 $ 4.8 Derivatives not designated as hedging instruments: Forward foreign currency contracts Prepaid expenses and other current assets $ 3.2 $ 0.4 Liabilities: Derivatives not designated as hedging instruments: Forward foreign currency contracts Accrued expenses $ 0.2 $ 4.0
Schedule of Unrealized Loss Recognized in AOCI	The following table presents the unrealized (gain) loss recognized in AOCI related to the interest rate caps for the following reporting periods: Year Ended Year Ended Year Ended Amount of (gain) loss recognized in other comprehensive (loss) income, net of taxes: Interest rate cap agreements $ (5.7 ) $ 0.8 $ (3.4 )
Gain (Loss) on Fair Value Hedges Recognized in Earnings	The following table presents the adjustment to fair value (realized and unrealized) recorded within the Consolidated Statements of Operations for derivative instruments for which the Company did not elect hedge accounting: Derivatives not classified as hedging instruments Location of Gain Recognized in Income Year Ended Year Ended Year Ended Forward foreign currency contracts $ 5.3 $ 0.5 $ 0.4 Other income, net
Accounts Receivable Reserve Activity	Accounts receivable reserve activity for fiscal 2018 , 2017 and 2016 was as follows: Balance at Beginning of Period Charged to Costs and Expenses Write- offs and Payments Balance at End of Period Period Ended: September 29, 2018 $ 9.8 $ 7.0 $ (0.6 ) $ 16.2 September 30, 2017 $ 12.7 $ 1.8 $ (4.7 ) $ 9.8 September 24, 2016 $ 11.1 $ 2.0 $ (0.4 ) $ 12.7
Schedule of Reconciliation of Basic and Diluted Share Amounts	A reconciliation of basic and diluted share amounts for fiscal 2018 , 2017 , and 2016 was as follows: September 29, 2018 September 30, 2017 September 24, 2016 Basic weighted average common shares outstanding 275,105 279,811 280,213 Weighted average common stock equivalents from assumed exercise of stock options and restricted stock units — 2,885 2,631 Incremental shares from convertible notes premium — 2,957 3,312 Diluted weighted average common shares outstanding 275,105 285,653 286,156 Weighted-average anti-dilutive shares related to: Outstanding stock options and stock units 5,073 1,677 1,029 Convertible notes 703 12 62
Schedule of Product Warranty Activity	Product warranty activity for fiscal 2018 and 2017 was as follows: Balance at Beginning of Period Acquired Provisions Settlements/ Adjustments Balance at End of Period Period ended: September 29, 2018 $ 17.0 $ — $ 18.3 $ (19.4 ) $ 15.9 September 30, 2017 $ 5.0 $ 9.9 $ 15.3 $ (13.2 ) $ 17.0

Business Combinations (Tables)

Business Combinations (Tables)	12 Months Ended
	Sep. 29, 2018
Business Combinations [Abstract]
Schedule of Purchase Price	The purchase price allocation is as follows: Cash $ 107.2 Marketable securities 82.9 Accounts receivable 40.2 Inventory 120.0 Property, plant and equipment 44.1 Other assets and liabilities, net 11.9 Accounts payable and accrued expenses (76.6 ) 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 (315.2 ) Goodwill 685.7 Purchase Price $ 1,657.8
Schedule of 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 (the first day of fiscal 2016): Twelve Months Ended Twelve Months Ended September 30, 2017 September 24, 2016 Revenue $ 3,241.4 $ 3,244.6 Net income $ 768.5 $ 252.3 Basic earnings per common share $ 2.75 $ 0.90 Diluted earnings per common share $ 2.69 $ 0.88

Restructuring Charges (Tables)

Restructuring Charges (Tables)	12 Months Ended
	Sep. 29, 2018
Restructuring and Related Activities [Abstract]
Charges Taken Related to Restructuring Actions	The following table displays charges taken related to restructuring actions in fiscal 2018 , 2017 and 2016 and a rollforward of the charges to the accrued balances as of September 29, 2018 : Fiscal 2018 Actions Fiscal 2017 Actions Fiscal 2016 Actions Total Restructuring Charges Fiscal 2016 charges: Workforce reductions $ — $ — $ 10.5 $ 10.5 Fiscal 2016 restructuring charges $ — $ — $ 10.5 $ 10.5 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 $ 11.7 $ — $ — $ 11.7 Facility closure costs 0.9 — 1.6 2.5 Fiscal 2018 restructuring charges $ 12.6 $ — $ 1.6 $14.2
Charges Taken Related to Accrued Restructuring Actions	Fiscal 2018 Actions Fiscal 2017 Actions Fiscal 2016 Actions Previous Other Charges Total Rollforward of Accrued Restructuring Balance as of September 26, 2015 $ — $ — $ — $ 5.7 $ 5.7 Fiscal 2016 restructuring charges $ — $ — $ 10.5 $ — $ 10.5 Stock-based compensation — — (0.4 ) — (0.4 ) Severance payments — — (4.6 ) (4.4 ) (9.0 ) Other payments — — — (0.5 ) (0.5 ) Balance as of September 24, 2016 $ — $ — $ 5.5 $ 0.8 $ 6.3 Fiscal 2017 restructuring charges $ — $ 8.5 $ 4.8 $ — $ 13.3 Severance payments — (1.0 ) (5.4 ) (0.2 ) (6.6 ) Other payments — — (1.2 ) (0.3 ) (1.5 ) Balance as of September 30, 2017 $ — $ 7.5 $ 3.7 $ 0.3 $ 11.5 Fiscal 2018 restructuring charges $ 12.6 $ — $ 1.6 $ — $ 14.2 Stock-based compensation (1.3 ) — — — (1.3 ) Severance payments and adjustments (6.8 ) (6.7 ) (0.2 ) — (13.7 ) Other payments (0.2 ) — (1.2 ) (0.2 ) (1.6 ) Balance as of September 29, 2018 $ 4.3 $ 0.8 $ 3.9 $ 0.1 $ 9.1

Borrowings and Credit Arrange_2

Borrowings and Credit Arrangements (Tables)	12 Months Ended
	Sep. 29, 2018
Debt Disclosure [Abstract]
Company's Borrowings and Interest Expense	The Company’s borrowings consisted of the following: September 29, September 30, Current debt obligations, net of debt discount and deferred issuance costs: Term Loan $ 74.7 $ 121.3 Revolver 300.0 345.0 Securitization Program 225.0 200.0 Convertible Notes — 484.5 Total current debt obligations 599.7 1,150.8 Long-term debt obligations, net of debt discount and issuance costs: Term Loan 1,376.3 1,190.5 2022 Senior Notes — 981.6 2025 Senior Notes 935.2 — 2028 Senior Notes 393.1 — Total long-term debt obligations 2,704.6 2,172.1 Total debt obligations $ 3,304.3 $ 3,322.9 Interest expense for the 2028 Senior Notes, 2025 Senior Notes and 2022 Senior Notes is as follows: September 29, 2018 September 30, 2017 September 24, 2016 Interest Rate Interest Expense (1) Non-Cash Interest Expense Interest Expense (1) Non-Cash Interest Expense Interest Expense (1) Non-Cash Interest Expense 2028 Senior Notes 4.625 % $ 13.3 $ 0.5 $ — $ — $ — $ — 2025 Senior Notes 4.375 % 34.7 1.6 — — — — 2022 Senior Notes 5.250 % 21.2 1.5 57.3 3.9 56.0 3.8 Total $ 69.2 $ 3.6 $ 57.3 $ 3.9 $ 56.0 $ 3.8 (1) Interest expense includes non-cash interest expense related to the amortization of the deferred issuance costs and accretion of the debt discount.
Schedule of Credit Agreements	Interest expense, non-cash interest expense, weighted average interest rate, and interest rate at the end of period under the Amended and Restated Credit Agreement, in fiscal 2018, and Prior Credit Agreement, in fiscal 2017 and 2016, is as follows: September 29, 2018 September 30, 2017 September 24, 2016 Interest expense (1) $ 60.8 $ 42.3 $ 40.4 Non-cash interest expense $ 2.6 $ 4.2 $ 4.4 Weighted average interest rate 3.23 % 2.39 % 2.08 % Interest rate at end of period 3.74 % 2.73 % 2.05 % (1) Interest expense includes non-cash interest expense related to the amortization of the deferred issuance costs and accretion of the debt discount.
Schedule Of Long Term Debt By Maturity Table	The debt maturity schedule for the Company’s obligations as of September 29, 2018 is as follows: 2019 2020 2021 2022 2023 2024 and Thereafter Total Term Loan $ 75.0 $ 75.0 $ 112.5 $ 150.0 $ 1,050.0 $ — $ 1,462.5 Revolver 300.0 — — — — — 300.0 Securitization Program 225.0 — — — — — 225.0 2025 Senior Notes — — — — — 950.0 950.0 2028 Senior Notes — — — — — 400.0 400.0 $ 600.0 $ 75.0 $ 112.5 $ 150.0 $ 1,050.0 $ 1,350.0 $ 3,337.5
Schedule Of Convertible Notes And Related Equity Components Recorded In Capital In Excess Of Par Value Net Of Deferred Taxes Table	As of September 29, 2018 the Convertible Notes were fully settled and for September 30, 2017 , the Convertible Notes and related equity components (recorded in additional paid-in-capital, net of deferred taxes) consisted of the following: 2017 2012 Notes principal amount $ 245.4 Unamortized discount and issuance costs (1.9 ) Net carrying amount $ 243.5 Equity component, net of taxes $ 24.1 2013 Notes principal amount $ 202.0 Principal accretion 40.8 Unamortized discount and issuance costs (1.8 ) Net carrying amount $ 241.0 Equity component, net of taxes $ 71.8
Interest Expense under Convertible Notes	Interest expense under the Convertible Notes is as follows: Years Ended September 29, September 30, September 24, Amortization of debt discount $ 3.5 $ 17.9 $ 22.3 Amortization of deferred financing costs 0.2 0.8 1.1 Principal accretion 1.6 15.6 16.6 Non-cash interest expense 5.3 34.3 40.0 2.00% accrued interest (cash) 1.8 6.7 10.0 $ 7.1 $ 41.0 $ 50.0

Fair Value Measurements (Tables

Fair Value Measurements (Tables)	12 Months Ended
	Sep. 29, 2018
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: Fair Value Measurements at September 29, 2018 Carrying Value Quoted Prices in Active Market for Identical Assets (Level 1) Significant Other Observable Inputs (Level 2) Significant Unobservable Inputs (Level 3) Assets: Interest rate caps - derivative 7.7 — 7.7 — Forward foreign currency contracts 3.2 — 3.2 — Total $ 10.9 $ — $ 10.9 $ — Liabilities: Contingent consideration $ 7.8 $ — $ — $ 7.8 Forward foreign currency contracts 0.2 — 0.2 — Total $ 8.0 $ — $ 0.2 $ 7.8 Fair Value Measurements at September 30, 2017 Carrying Value Quoted Prices in Active Market for Identical Assets (Level 1) Significant Other Observable Inputs (Level 2) Significant Unobservable Inputs (Level 3) Assets: Equity securities $ 0.1 $ 0.1 $ — $ — Interest rate caps - derivative 4.8 — 4.8 — Forward foreign currency contracts 0.4 — 0.4 — Total $ 5.3 $ 0.1 $ 5.2 $ — Liabilities: Forward foreign currency contracts 4.0 — 4.0 — Total $ 4.0 $ — $ 4.0 $ —
Estimated Fair Values of Convertible Notes	The estimated fair values of the Company’s Convertible Notes at September 30, 2017 were as follows: 2017 2012 Notes 297.3 2013 Notes 244.4 $ 541.7

Income Taxes (Tables)

Income Taxes (Tables)	12 Months Ended
	Sep. 29, 2018
Income Tax Disclosure [Abstract]
Income (Loss) Before Income Taxes	The Company’s income before income taxes consisted of the following: Years ended September 29, 2018 September 30, 2017 September 24, 2016 Domestic $ (581.9 ) $ 1,105.8 $ 310.7 Foreign 163.3 124.7 104.6 $ (418.6 ) $ 1,230.5 $ 415.3
Provision for Income Taxes	The (benefit) provision for income taxes contained the following components: Years ended September 29, 2018 September 30, 2017 September 24, 2016 Federal: Current $ 137.1 $ 701.1 $ 209.0 Deferred (461.9 ) (276.9 ) (122.7 ) (324.8 ) 424.2 86.3 State: Current 11.0 53.1 16.6 Deferred (11.3 ) (15.9 ) (22.7 ) (0.3 ) 37.2 (6.1 ) Foreign: Current 21.9 13.9 14.7 Deferred (4.1 ) (0.3 ) (10.4 ) 17.8 13.6 4.3 $ (307.3 ) $ 475.0 $ 84.5
Reconciliation of Income Tax (Benefit) at U.S. Federal Statutory Rate to Company's Effective Tax Rate	The income tax (benefit) provision differed from the tax (benefit) provision computed at the U.S. federal statutory rate due to the following: Years ended September 29, 2018 September 30, 2017 September 24, 2016 Income tax (benefit) provision at federal statutory rate (24.5 )% 35.0 % 35.0 % Increase (decrease) in tax resulting from: Domestic production activities deduction (3.1 ) (1.7 ) (5.0 ) State income taxes, net of federal benefit 0.7 2.3 2.0 Non-deductible goodwill 39.4 9.2 — Tax credits (1.9 ) (0.8 ) (3.2 ) Tax reform (82.7 ) — — Unrecognized tax benefits 1.8 (1.4 ) 2.4 Compensation 0.3 (0.5 ) 0.1 Foreign rate differential (5.2 ) (2.6 ) (6.1 ) Change in deferred tax rate 1.2 0.2 (1.8 ) Change in valuation allowance (0.5 ) (1.5 ) (3.4 ) Other 1.1 0.4 0.3 (73.4 )% 38.6 % 20.3 %
Significant Components of the Company's Deferred Tax Assets and Liabilities	The Company’s significant deferred tax assets and liabilities were as follows: September 29, 2018 September 30, 2017 Deferred tax assets Net operating loss carryforwards $ 30.9 $ 50.1 Capital losses 6.5 7.1 Non-deductible accruals 30.7 50.6 Non-deductible reserves 22.1 30.0 Stock-based compensation 24.0 39.3 Research and other credits 13.3 13.6 Nonqualified deferred compensation plan 12.3 16.4 Other temporary differences 11.5 16.5 151.3 223.6 Less: valuation allowance (25.5 ) (28.2 ) $ 125.8 $ 195.4 Deferred tax liabilities Depreciation and amortization $ (606.6 ) $ (1,071.5 ) Debt discounts and deferrals (4.5 ) (88.4 ) $ (611.1 ) $ (1,159.9 ) $ (485.3 ) $ (964.5 )
Activity of the Company's Unrecognized Income Tax Benefits	The Company’s unrecognized income tax benefits activity for fiscal 2018 and 2017 was as follows: 2018 2017 Balance at beginning of fiscal year $ 90.3 $ 163.6 Tax positions related to current year: Additions 9.0 21.8 Reductions — — Tax positions related to prior years: Additions related to change in estimate 6.6 1.1 Reductions (15.4 ) (77.3 ) Payments — (1.6 ) Lapses in statutes of limitations (1.4 ) (19.9 ) Acquired tax positions: Additions related to reserves acquired from acquisitions 0.4 2.6 Balance as of the end of the fiscal year $ 89.5 $ 90.3

Stockholders' Equity and Stoc_2

Stockholders' Equity and Stock-Based Compensation (Tables)	12 Months Ended
	Sep. 29, 2018
Disclosure of Compensation Related Costs, Share-based Payments [Abstract]
Stock-Based Compensation Expense in Consolidated Statement of Operations	The following presents stock-based compensation expense in the Company’s Consolidated Statements of Operations in fiscal 2018 , 2017 and 2016 : 2018 2017 2016 Cost of revenues $ 8.3 $ 10.7 $ 10.5 Research and development 9.5 11.2 10.8 Selling and marketing 10.3 11.9 10.9 General and administrative 35.6 34.4 32.8 Restructuring and divestiture 1.3 — 0.4 $ 65.0 $ 68.2 $ 65.4
Information Pertaining to Stock Options Granted and Related Assumptions	Information pertaining to stock options granted during fiscal 2018 , 2017 and 2016 and related assumptions are noted in the following table: Years ended September 29, 2018 September 30, 2017 September 24, 2016 Options granted (in millions) 1.7 1.0 1.1 Weighted-average exercise price $ 40.76 $ 38.07 $ 39.32 Weighted-average grant date fair value $ 12.98 $ 12.33 $ 12.91 Assumptions: Risk-free interest rates 2.1 % 1.8 % 1.6 % Expected life (in years) 4.7 4.7 4.7 Expected volatility 35.3 % 36.6 % 37.8 % Dividend yield — — —
Stock Option Activity	The following table summarizes all stock option activity under the Company’s stock option plans for the year ended September 29, 2018 : Number of Shares (in millions) Weighted- Average Exercise Price Weighted- Average Remaining Contractual Life (in Years) Aggregate Intrinsic Value (in millions) Options outstanding at September 30, 2017 5.5 $ 28.15 5.4 $ 50.3 Granted 1.7 40.76 Canceled/ forfeited (0.4 ) 36.22 Exercised (0.8 ) 21.72 15.2 Options outstanding at September 29, 2018 6.0 $ 32.13 5.9 $ 53.3 Options exercisable at September 29, 2018 2.8 $ 26.47 3.7 $ 40.8 Options vested and expected to vest at September 29, 2018 (1) 5.9 $ 32.08 5.9 $ 52.8 (1) This represents the number of vested stock options as of September 29, 2018 plus the unvested outstanding options at September 29, 2018 expected to vest in the future, adjusted for estimated forfeitures.
Restricted Stock Unit Activity	A summary of the Company’s RSU, PSU and MSU activity during the year ended September 29, 2018 is presented below: Non-vested Shares Number of Shares (in millions) Weighted-Average Grant-Date Fair Value Non-vested at September 30, 2017 3.0 $ 34.58 Granted 1.7 42.49 Vested (1.6 ) 34.10 Forfeited (0.4 ) 38.28 Non-vested at September 29, 2018 2.7 $ 40.02
Black-Scholes Model Weighted Average Assumptions Used to Estimate Fair Value of Shares to Be Issued as of Grant Date	The Company uses the Black-Scholes model to estimate the fair value of shares to be issued as of the grant date using the following weighted average assumptions: September 29, 2018 September 30, 2017 September 24, 2016 Assumptions: Risk-free interest rates 1.62 % 0.72 % 0.34 % Expected life (in years) 0.5 0.5 0.5 Expected volatility 25.0 % 24.9 % 27.2 % Dividend yield — — —

Commitments and Contingencies (

Commitments and Contingencies (Tables)	12 Months Ended
	Sep. 29, 2018
Commitments and Contingencies Disclosure [Abstract]
Schedule of Future Minimum Lease Payments for Capital Leases	Future minimum lease payments, including principal and interest, under these leases were as follows at September 29, 2018 : Fiscal 2019 $ 2.9 Fiscal 2020 3.0 Fiscal 2021 3.0 Fiscal 2022 3.1 Fiscal 2023 3.2 Thereafter 10.6 Total minimum payments 25.8 Less-amount representing interest (14.4 ) Total $ 11.4
Unrecorded Unconditional Purchase Obligations Disclosure	At September 29, 2018 , non-cancelable purchase commitments are as follows: Fiscal 2019 $ 341.7 Fiscal 2020 3.1 Fiscal 2021 0.9 Total $ 345.7
Schedule of Future Minimum Rental Payments for Operating Leases	Future minimum lease payments under all of the Company’s operating leases at September 29, 2018 are as follows: Fiscal 2019 $ 21.0 Fiscal 2020 16.9 Fiscal 2021 13.9 Fiscal 2022 11.2 Fiscal 2023 6.7 Thereafter 17.9 Total $ 87.6
Schedule Of Future Minimum Annual Rental Income Payments Under Sublease Agreements	The future minimum annual rental income payments under these sublease agreements at September 29, 2018 are as follows: Fiscal 2019 $ 2.5 Fiscal 2020 1.8 Fiscal 2021 0.6 Fiscal 2022 0.6 Fiscal 2023 0.6 Thereafter 1.2 Total $ 7.3

Disposition (Tables)

Disposition (Tables)	12 Months Ended
	Sep. 29, 2018
Disposal Groups, Including Discontinued Operations and Collaborative Agreement [Abstract]
Schedule of Disposed Business, Income from Operations	for the years ended September 30, 2017 and September 24, 2016 was as follows: Years Ended September 30, 2017 September 24, 2016 Income from operations $ 45.8 $ 99.1

Business Segments and Geograp_2

Business Segments and Geographic Information (Tables)	12 Months Ended
	Sep. 29, 2018
Segment Reporting [Abstract]
Segment Information	Segment information for fiscal 2018 , 2017 , and 2016 was as follows: Years ended September 29, September 30, September 24, Total revenues: Diagnostics $ 1,147.4 $ 1,197.1 $ 1,236.9 Breast Health 1,218.2 1,138.3 1,112.8 Medical Aesthetics 339.1 207.5 — GYN Surgical 422.0 427.1 393.1 Skeletal Health 91.2 88.8 89.9 $ 3,217.9 $ 3,058.8 $ 2,832.7 Operating (loss) income: Diagnostics $ 145.5 $ 1,054.2 $ 126.0 Breast Health 399.7 373.4 350.5 Medical Aesthetics (844.7 ) (115.9 ) — GYN Surgical 58.3 65.0 69.1 Skeletal Health 3.3 (6.5 ) 3.0 $ (237.9 ) $ 1,370.2 $ 548.6 Depreciation and amortization: Diagnostics $ 257.3 $ 278.9 $ 341.8 Breast Health 22.7 19.7 22.6 Medical Aesthetics 108.1 54.2 — GYN Surgical 91.6 95.7 99.9 Skeletal Health 0.6 0.7 1.1 $ 480.3 $ 449.2 $ 465.4 Capital expenditures: Diagnostics $ 57.7 $ 50.9 $ 53.5 Breast Health 14.8 12.0 10.6 Medical Aesthetics 9.4 7.3 — GYN Surgical 13.1 15.2 17.7 Skeletal Health 3.3 1.2 0.4 Corporate 7.3 21.0 12.3 $ 105.6 $ 107.6 $ 94.5 September 29, September 30, September 24, Identifiable assets: Diagnostics $ 2,442.9 $ 2,621.6 $ 3,771.9 Breast Health 972.4 824.0 809.1 Medical Aesthetics 913.3 1,751.2 — GYN Surgical 1,414.9 1,494.6 1,570.7 Skeletal Health 30.3 25.5 30.9 Corporate 1,457.1 1,262.7 1,134.4 $ 7,230.9 $ 7,979.6 $ 7,317.0
Revenues by Geography	Revenues by geography as a percentage of total revenues were as follows: Years ended September 29, September 30, September 24, United States 75.1 % 77.6 % 78.9 % Europe 11.7 % 10.0 % 10.2 % Asia-Pacific 8.6 % 8.1 % 7.6 % Rest of world 4.6 % 4.3 % 3.3 % 100.0 % 100.0 % 100.0 %
Schedule of Revenue from External Customers and Long-Lived Assets, by Geographical Areas [Table Text Block]	The Company’s property, plant and equipment, net are geographically located as follows: September 29, 2018 September 30, 2017 September 24, 2016 United States $ 366.5 $ 368.1 $ 362.4 Costa Rica 30.9 30.1 28.1 Europe 62.0 57.1 49.2 Rest of world 18.8 17.5 12.2 $ 478.2 $ 472.8 $ 451.9

Accrued Expenses and Other Lo_2

Accrued Expenses and Other Long-Term Liabilities (Tables)	12 Months Ended
	Sep. 29, 2018
Payables and Accruals [Abstract]
Schedule of Accrued Expenses	Accrued expenses and other long-term liabilities consisted of the following: September 29, 2018 September 30, 2017 Accrued Expenses Compensation and employee benefits $ 196.0 $ 176.7 Income and other taxes 57.2 66.9 Other 182.9 131.7 $ 436.1 $ 375.3
Schedule of Other Long-Term Liabilities	September 29, 2018 September 30, 2017 Other Long-Term Liabilities Reserve for income tax uncertainties $ 92.6 $ 88.3 Accrued lease obligation—long-term 35.5 34.1 Pension liabilities 9.9 10.0 Other 19.6 7.8 $ 157.6 $ 140.2

Pension and Other Employee Be_2

Pension and Other Employee Benefits (Tables)	12 Months Ended
	Sep. 29, 2018
Retirement Benefits [Abstract]
Schedule of Reconciliation of Benefit Obligations, Plan Assets, Funded Status and Related Actuarial Assumptions	The tables below provide a reconciliation of benefit obligations, plan assets, funded status, and related actuarial assumptions of the Company’s German Pension Benefits. Change in Benefit Obligation Years ended September 29, 2018 September 30, 2017 September 24, 2016 Benefit obligation at beginning of year $ (9.9 ) $ (11.0 ) $ (10.0 ) Service cost — — — Interest cost (0.2 ) (0.1 ) (0.2 ) Plan participants’ contributions — — — Actuarial gain (loss) (0.1 ) 1.5 (1.2 ) Foreign exchange gain 0.2 (0.6 ) 0.1 Benefits paid 0.3 0.3 0.3 Benefit obligation at end of year (9.7 ) (9.9 ) (11.0 ) Plan assets — — — Benefit obligation at end of year $ (9.7 ) $ (9.9 ) $ (11.0 )
Components of Net Periodic Benefit Cost and Related Actuarial Assumptions	The tables below outline the components of the net periodic benefit cost and related actuarial assumptions of the Company’s German Pension Benefits. Components of Net Periodic Benefit Cost Years ended September 29, 2018 September 30, 2017 September 24, 2016 Service cost $ — $ — $ — Interest cost 0.2 0.1 0.4 Expected return on plan assets — — — Amortization of prior service cost — — Recognized net actuarial gain 0.1 0.4 (0.2 ) Net periodic benefit cost $ 0.3 $ 0.5 $ 0.2
Schedule of Weighted-Average Net Periodic Benefit Cost Assumptions	Weighted-Average Net Periodic Benefit Cost Assumptions 2018 2017 2016 Discount rate 1.95 % 2.15 % 1.30 % Expected return on plan assets — % — % — % Rate of compensation increase — % — % — %
Schedule of Expected Pension Benefit	The table below reflects the total Pension Benefits expected to be paid for the German Pension Benefits each fiscal year as of September 29, 2018 : 2019 $ 0.4 2020 $ 0.4 2021 $ 0.4 2022 $ 0.4 2023 $ 0.4 2023 to 2027 $ 2.1

Quarterly Statement of Operat_2

Quarterly Statement of Operations Information (Unaudited) (Tables)	12 Months Ended
	Sep. 29, 2018
Quarterly Financial Information Disclosure [Abstract]
Summary of Quarterly Results of Operations	The following table presents a summary of quarterly results of operations for fiscal 2018 and 2017 : 2018 First Quarter Second Quarter Third Quarter Fourth Quarter Total revenue $ 791.1 $ 789.3 $ 824.0 $ 813.5 Gross profit 424.5 415.1 436.0 421.1 Net income (loss) (1) 406.7 (681.4 ) 112.9 50.5 Diluted net income (loss) per common share $ 1.45 $ (2.46 ) $ 0.41 $ 0.18 2017 First Quarter Second Quarter Third Quarter Fourth Quarter Total revenue $ 734.4 $ 715.4 $ 806.1 $ 802.9 Gross profit 404.8 388.7 409.6 417.9 Net income (2) 86.5 526.8 59.5 82.7 Diluted net income per common share $ 0.30 $ 1.84 $ 0.21 $ 0.29 (1) Net income in the first quarter of fiscal 2018 included the impact of implementing tax reform, which resulted in a provisional net tax benefit of $329.2 million . Net loss in the second quarter of fiscal 2018 included a goodwill impairment charge of $685.7 million , an in-process research and development intangible asset charge of $46.0 million and a debt extinguishment loss of $44.9 million . Net income in the fourth quarter of fiscal 2018 included a litigation settlement charge of $34.8 million . (2) Net income in the second quarter of fiscal 2017 included a gain on the sale of the blood screening business of $899.7 million and acquisition transaction expenses of $19.4 million .

Operations (Details)

Operations (Details)	Mar. 22, 2017Segment
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Number of operating segments	5

Summary of Significant Accoun_4

Summary of Significant Accounting Policies - Additional Information (Detail)	Oct. 01, 2018USD ($)	Jul. 31, 2018USD ($)	Dec. 11, 2017USD ($)	Mar. 22, 2017USD ($)	Sep. 29, 2018USD ($)Customer	Mar. 31, 2018USD ($)	Dec. 30, 2017USD ($)	Sep. 30, 2017USD ($)projectCustomer	Apr. 01, 2017USD ($)	Dec. 31, 2016USD ($)	Dec. 26, 2015USD ($)	Sep. 29, 2018USD ($)Customer	Sep. 30, 2017USD ($)projectCustomer	Sep. 24, 2016USD ($)	Sep. 26, 2015USD ($)	Jul. 01, 2017USD ($)	Apr. 07, 2017USD ($)
Significant Accounting Policies [Line Items]
Goodwill impairment charge						$ 685,700,000						$ 685,700,000	$ 0	$ 0
Marketable Securities, Realized Gain (Loss)							$ 600,000
Litigation settlement expense					$ 34,800,000					$ 9,200,000
Cash Equivalents Maturity Period												three months or less
Gross Carrying Value					$ 5,571,800,000			$ 5,562,500,000				$ 5,571,800,000	5,562,500,000
Net gain reclassified from accumulated other comprehensive income to the statement of income											$ 7,200,000	$ (400,000)	$ 2,400,000	6,100,000
Number of customers with balance greater than specified percentage | Customer					0			0				0	0
Accumulated Amortization					$ 3,173,200,000			$ 2,790,200,000				$ 3,173,200,000	$ 2,790,200,000
Sensitivity Change To Fair Value By Percent												10.00%
Goodwill					2,533,200,000			3,171,200,000				$ 2,533,200,000	3,171,200,000
Other-than-temporary impairment charges								0
Purchase of interest rate caps												3,700,000	1,900,000	0	$ 13,200,000
Principal amount of borrowings					1,000,000,000							1,000,000,000
Loss reclassified from accumulated other comprehensive loss to the statement of operations, net								6,900,000				3,600,000	6,900,000	3,900,000
Derivative Instruments, Gain (Loss) Reclassification from Accumulated OCI to Income, Estimated Net Amount to be Transferred												3,100,000
Gain (Loss) on Foreign Currency Derivative Instruments Not Designated as Hedging Instruments												1,300,000	3,100,000	1,500,000
Unrealized Gain (Loss) on Foreign Currency Derivatives, Net, before Tax								3,600,000				6,600,000		1,100,000
Notional Amount					288,400,000							$ 288,400,000
Product Warranty Term												1 year
Advertising cost												$ 26,900,000	22,500,000	20,200,000
Reclassification from Accumulated Other Comprehensive Income, Current Period, Net of Tax												4,000,000	4,500,000
Increase to cash flows used in financing activities												195,200,000	(285,800,000)	$ 68,400,000
Accelerated Depreciation												5,900,000	3,000,000
Developed Technology Rights [Member]
Significant Accounting Policies [Line Items]
Gross Carrying Value					4,573,300,000			4,528,700,000				4,573,300,000	4,528,700,000
Accumulated Amortization					2,505,800,000			2,186,800,000				2,505,800,000	2,186,800,000
Trade Names [Member]
Significant Accounting Policies [Line Items]
Gross Carrying Value					312,500,000			310,300,000				312,500,000	310,300,000
Accumulated Amortization					175,000,000			156,400,000				175,000,000	156,400,000
In-process research and development
Significant Accounting Policies [Line Items]
Gross Carrying Value					5,500,000			46,000,000				5,500,000	46,000,000
Accumulated Amortization					0			$ 0				$ 0	0
Minimum
Significant Accounting Policies [Line Items]
Intangible assets useful life												2 years
Defined contract term												3 years
Transition services agreement term									2 years
Minimum | Accounts receivable [Member]
Significant Accounting Policies [Line Items]
Concentration risk, percentage								10.00%				10.00%
Minimum | Total revenues [Member]
Significant Accounting Policies [Line Items]
Concentration risk, percentage								10.00%				10.00%		10.00%
Maximum
Significant Accounting Policies [Line Items]
Intangible assets useful life												30 years
Defined contract term												5 years
Transition services agreement term									3 years
Other Nonoperating Income (Expense) [Member]
Significant Accounting Policies [Line Items]
Gain on Sale of Investments											25,100,000
Interest Rate Cap [Member]
Significant Accounting Policies [Line Items]
Interest rate caps - derivative					7,700,000			$ 4,800,000				$ 7,700,000	4,800,000
Equity Securities [Member]
Significant Accounting Policies [Line Items]
Realized Gain (Loss) on Marketable Securities, Cost Method Investments, and Other Investments											$ 25,100,000
Other than Temporary Impairment Losses, Investments, Portion Recognized in Earnings, Net													0
Cynosure
Significant Accounting Policies [Line Items]
Goodwill impairment charge						685,700,000
Business Combination, Recognized Identifiable Assets Acquired And Liabilities Assumed, Marketable Securities				$ 82,900,000
Intangible assets									$ 994,000,000
Goodwill				685,700,000
Total purchase price				1,660,000,000
Cynosure | Developed Technology Rights [Member]
Significant Accounting Policies [Line Items]
Gross Carrying Value								$ 61,000,000					$ 61,000,000
Impairment of intangible assets						46,000,000
Cynosure | In-process research and development
Significant Accounting Policies [Line Items]
Intangible assets				$ 107,000,000
Number of Projects | project								2					2
Cynosure | Goodwill [Member]
Significant Accounting Policies [Line Items]
Goodwill impairment charge						$ 685,700,000
Cynosure | Minimum | Other intangible assets
Significant Accounting Policies [Line Items]
Discount rate (as a percent)				11.00%
Cynosure | Minimum | In-process research and development
Significant Accounting Policies [Line Items]
Discount rate (as a percent)				14.00%
Cynosure | Maximum | Other intangible assets
Significant Accounting Policies [Line Items]
Discount rate (as a percent)				12.00%
Cynosure | Maximum | In-process research and development
Significant Accounting Policies [Line Items]
Discount rate (as a percent)				22.00%
Emsor
Significant Accounting Policies [Line Items]
Intangible assets			$ 4,600,000
Goodwill			5,700,000
Total purchase price			$ 16,300,000
Faxitron
Significant Accounting Policies [Line Items]
Intangible assets					53,400,000							53,400,000
Goodwill		$ 41,600,000
Total purchase price		$ 89,000,000
Faxitron | Minimum | In-process research and development
Significant Accounting Policies [Line Items]
Discount rate (as a percent)		17.00%
Faxitron | Maximum | In-process research and development
Significant Accounting Policies [Line Items]
Discount rate (as a percent)		19.00%
Medicor Medical Supply
Significant Accounting Policies [Line Items]
Intangible assets																$ 5,400,000	$ 5,400,000
Goodwill																	$ 8,900,000
Gen-Probe Incorporated [Member] | Developed Technology Rights [Member]
Significant Accounting Policies [Line Items]
Intangible assets																$ 3,700,000
Discontinued Operations, Disposed of by Sale [Member] | Blood Screening Business | Developed Technology Rights [Member]
Significant Accounting Policies [Line Items]
Disposal Group, Including Discontinued Operation, Intangible Assets									154,000,000
Discontinued Operations, Disposed of by Sale [Member] | Blood Screening Business | Customer relationships
Significant Accounting Policies [Line Items]
Disposal Group, Including Discontinued Operation, Intangible Assets									$ 387,700,000
Medical Aesthetics [Member]
Significant Accounting Policies [Line Items]
Goodwill impairment charge												685,700,000
Goodwill					0			$ 683,500,000				0	$ 683,500,000
Medical Aesthetics [Member] | Cynosure | Maximum | Other intangible assets
Significant Accounting Policies [Line Items]
Discount rate (as a percent)				12.00%
Operating Segments [Member]
Significant Accounting Policies [Line Items]
Goodwill					$ 2,500,000,000							$ 2,500,000,000
Accounting Standards Update 2016-09 [Member]
Significant Accounting Policies [Line Items]
Increase to cash flows used in financing activities								$ 11,000,000						$ 10,700,000
Forward foreign currency contracts
Significant Accounting Policies [Line Items]
Derivative contract period, or less												1 year
Subsequent Event | Focal Therapeutics [Member]
Significant Accounting Policies [Line Items]
Total purchase price	$ 125,000,000

Summary of Significant Accoun_5

Summary of Significant Accounting Policies - Supplemental Cash Flow Statement Information (Detail) - USD ($) $ in Millions	12 Months Ended
	Sep. 29, 2018	Sep. 30, 2017	Sep. 24, 2016
Accounting Policies [Abstract]
Cash paid during the period for income taxes	$ 178.2	$ 867.8	$ 184.8
Cash paid during the period for interest	$ 122.1	$ 102.4	$ 104

Summary of Significant Accoun_6

Summary of Significant Accounting Policies - Schedule of Inventories (Detail) - USD ($) $ in Millions	Sep. 29, 2018	Sep. 30, 2017
Accounting Policies [Abstract]
Raw materials	$ 134.9	$ 95.7
Work-in-process	52.1	45
Finished goods	197.1	190.9
Inventories	$ 384.1	$ 331.6

Summary of Significant Accoun_7

Summary of Significant Accounting Policies - Estimated Useful Lives of Property, Plant and Equipments (Detail) - USD ($) $ in Millions	12 Months Ended
	Sep. 29, 2018	Sep. 30, 2017	Sep. 24, 2016
Property, Plant and Equipment [Line Items]
Manufacturing Equipment And Software	$ 391.9	$ 357.9
Equipment Under Customer Usage Agreements	399.6	368.7
Buildings and Improvements, Gross	175.1	172
Leasehold Improvements, Gross	63	60.6
Land	46.3	46.3
Furniture and Fixtures, Gross	18.4	20.8
Property, Plant and Equipment, Gross	1,094.3	1,026.3
Less - accumulated depreciation and amortization	(616.1)	(553.5)
Property, plant and equipment, net	$ 478.2	$ 472.8	$ 451.9
Building and Improvements [Member] | Minimum
Property, Plant and Equipment [Line Items]
Property, plant and equipment, estimated useful life	20 years
Building and Improvements [Member] | Maximum
Property, Plant and Equipment [Line Items]
Property, plant and equipment, estimated useful life	35 years
Equipment and Software [Member] | Minimum
Property, Plant and Equipment [Line Items]
Property, plant and equipment, estimated useful life	3 years
Equipment and Software [Member] | Maximum
Property, Plant and Equipment [Line Items]
Property, plant and equipment, estimated useful life	10 years
Equipment Under Customer Usage Agreements [Member] | Minimum
Property, Plant and Equipment [Line Items]
Property, plant and equipment, estimated useful life	3 years
Equipment Under Customer Usage Agreements [Member] | Maximum
Property, Plant and Equipment [Line Items]
Property, plant and equipment, estimated useful life	8 years
Furniture and Fixtures [Member] | Minimum
Property, Plant and Equipment [Line Items]
Property, plant and equipment, estimated useful life	5 years
Furniture and Fixtures [Member] | Maximum
Property, Plant and Equipment [Line Items]
Property, plant and equipment, estimated useful life	7 years

Summary of Significant Accoun_8

Summary of Significant Accounting Policies - Schedule of Intangible Assets (Detail) - USD ($) $ in Millions	Sep. 29, 2018	Sep. 30, 2017
Finite-Lived Intangible Assets [Line Items]
Gross Carrying Value	$ 5,571.8	$ 5,562.5
Accumulated Amortization	3,173.2	2,790.2
Developed technology
Finite-Lived Intangible Assets [Line Items]
Gross Carrying Value	4,573.3	4,528.7
Accumulated Amortization	2,505.8	2,186.8
In-process research and development
Finite-Lived Intangible Assets [Line Items]
Gross Carrying Value	5.5	46
Accumulated Amortization	0	0
Customer relationships
Finite-Lived Intangible Assets [Line Items]
Gross Carrying Value	556.5	552.8
Accumulated Amortization	428.1	393.8
Trade names
Finite-Lived Intangible Assets [Line Items]
Gross Carrying Value	312.5	310.3
Accumulated Amortization	175	156.4
Distribution agreement
Finite-Lived Intangible Assets [Line Items]
Gross Carrying Value	42	42
Accumulated Amortization	8	2.8
Non-competition agreements
Finite-Lived Intangible Assets [Line Items]
Gross Carrying Value	1.5	1.5
Accumulated Amortization	0.5	0.1
Business licenses
Finite-Lived Intangible Assets [Line Items]
Gross Carrying Value	2.4	2.4
Accumulated Amortization	2.2	2.2
Acquired intangible assets [Member]
Finite-Lived Intangible Assets [Line Items]
Gross Carrying Value	5,493.7	5,483.7
Accumulated Amortization	3,119.6	2,742.1
Internal-use software [Member]
Finite-Lived Intangible Assets [Line Items]
Gross Carrying Value	58.5	64.5
Accumulated Amortization	49.3	46.1
Capitalized software [Member]
Finite-Lived Intangible Assets [Line Items]
Gross Carrying Value	19.6	14.3
Accumulated Amortization	$ 4.3	$ 2

Summary of Significant Accoun_9

Summary of Significant Accounting Policies - Schedule of Estimated Amortization Expense (Detail) $ in Millions	Sep. 29, 2018USD ($)
Accounting Policies [Abstract]
Fiscal 2,019	$ 370.9
Fiscal 2,020	359.8
Fiscal 2,021	338.2
Fiscal 2,022	325.4
Fiscal 2,023	$ 226

Summary of Significant Accou_10

Summary of Significant Accounting Policies - Rollforward of Goodwill Activity by Reportable Segments (Detail) - USD ($)	3 Months Ended	12 Months Ended
	Mar. 31, 2018	Sep. 29, 2018	Sep. 30, 2017	Sep. 24, 2016
Goodwill [Roll Forward]
Balance at September 30, 2017		$ 3,171,200,000
Goodwill, Impairment Loss	$ (685,700,000)	(685,700,000)	$ 0	$ 0
Foreign currency and other adjustments		400,000
Balance at September 29, 2018		2,533,200,000	3,171,200,000
Diagnostics
Goodwill [Roll Forward]
Balance at September 30, 2017		823,000,000
Goodwill, Impairment Loss		0
Foreign currency and other adjustments		(1,800,000)
Balance at September 29, 2018		821,200,000	823,000,000
Breast Health
Goodwill [Roll Forward]
Balance at September 30, 2017		641,500,000
Goodwill, Impairment Loss		0
Foreign currency and other adjustments		700,000
Balance at September 29, 2018		689,500,000	641,500,000
Medical Aesthetics
Goodwill [Roll Forward]
Balance at September 30, 2017		683,500,000
Goodwill, Impairment Loss		(685,700,000)
Foreign currency and other adjustments		2,200,000
Balance at September 29, 2018		0	683,500,000
GYN Surgical
Goodwill [Roll Forward]
Balance at September 30, 2017		1,015,100,000
Goodwill, Impairment Loss		0
Foreign currency and other adjustments		(700,000)
Balance at September 29, 2018		1,014,400,000	1,015,100,000
Skeletal Health
Goodwill [Roll Forward]
Balance at September 30, 2017		8,100,000
Goodwill, Impairment Loss		0
Foreign currency and other adjustments		0
Balance at September 29, 2018		8,100,000	$ 8,100,000
Faxitron
Goodwill [Roll Forward]
Faxitron acquisition		41,600,000
Faxitron | Diagnostics
Goodwill [Roll Forward]
Faxitron acquisition		0
Faxitron | Breast Health
Goodwill [Roll Forward]
Faxitron acquisition		41,600,000
Faxitron | Medical Aesthetics
Goodwill [Roll Forward]
Faxitron acquisition		0
Faxitron | GYN Surgical
Goodwill [Roll Forward]
Faxitron acquisition		0
Faxitron | Skeletal Health
Goodwill [Roll Forward]
Faxitron acquisition		0
Emsor
Goodwill [Roll Forward]
Faxitron acquisition		5,700,000
Emsor | Diagnostics
Goodwill [Roll Forward]
Faxitron acquisition		0
Emsor | Breast Health
Goodwill [Roll Forward]
Faxitron acquisition		5,700,000
Emsor | Medical Aesthetics
Goodwill [Roll Forward]
Faxitron acquisition		0
Emsor | GYN Surgical
Goodwill [Roll Forward]
Faxitron acquisition		0
Emsor | Skeletal Health
Goodwill [Roll Forward]
Faxitron acquisition		$ 0

Summary of Significant Accou_11

Summary of Significant Accounting Policies - Schedule of Other Assets (Detail) - USD ($) $ in Millions	Sep. 29, 2018	Sep. 30, 2017
Accounting Policies [Abstract]
Life insurance contracts	$ 44.2	$ 41
Manufacturing access fees	4.6	7.1
Cost-method equity investments	8.8	3
Manufacturing access fees	12.9	9.1
Other	27.2	24.5
Other assets	$ 97.7	$ 84.7

Summary of Significant Accou_12

Summary of Significant Accounting Policies - Changes in accumulated balances of other comprehensive income (Details) - USD ($) $ in Millions	12 Months Ended
	Sep. 29, 2018	Sep. 30, 2017	Sep. 24, 2016
Accumulated Other Comprehensive Income (Loss) [Line Items]
Accumulated Other Comprehensive Income (Loss), Foreign Currency Translation Adjustment, Net of Tax	$ (26.6)	$ (18.5)	$ (26.1)
Accumulated Other Comprehensive Income (Loss), Available-for-sale Securities Adjustment, Net of Tax	0	(0.4)	(0.3)
Accumulated Other Comprehensive (Income) Loss, Defined Benefit Plan, after Tax	(1.1)	(1.6)	(2.5)
Accumulated other comprehensive Income loss Hedge	2.2	4.3	(3.4)
Accumulated Other Comprehensive Income (Loss), Net of Tax	(25.5)	(16.2)	(32.3)
Other Comprehensive Income (Loss), Foreign Currency Transaction and Translation Adjustment, Net of Tax, Portion Attributable to Parent	(8.1)	7.6	(10.4)
Other Comprehensive Income (Loss), Available-for-sale Securities Adjustment, Net of Tax	0	2.3	(1.1)
Other Comprehensive (Income) Loss, Defined Benefit Plan, after Tax and Reclassification Adjustment, Attributable to Parent	(0.5)	(0.9)	$ 0.7
Derivative Instruments, Gain (Loss) Recognized in Other Comprehensive Income (Loss), Effective Portion, Net	(5.7)	0.8
Other Comprehensive Income (Loss), before Reclassifications, before Tax	(13.3)	11.6
Reclassification from Accumulated Other Comprehensive Income, Current Period, Net of Tax	4	4.5
Accumulated Foreign Currency Adjustment Attributable to Parent [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Reclassification from Accumulated Other Comprehensive Income, Current Period, Net of Tax	0	0
Pension in Accumulated Other Comprehensive Income [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Reclassification from Accumulated Other Comprehensive Income, Current Period, Net of Tax	0	0
Equity Securities [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Reclassification from Accumulated Other Comprehensive Income, Current Period, Net of Tax	0.4	(2.4)
Interest Rate Cap [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Reclassification from Accumulated Other Comprehensive Income, Current Period, Net of Tax	$ 3.6	$ 6.9

Summary of Significant Accou_13

Summary of Significant Accounting Policies - Schedule of Derivative Instruments on the Consolidated Balance Sheets (Details) - USD ($) $ in Millions	12 Months Ended
	Sep. 29, 2018	Sep. 30, 2017
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Derivative Instruments, Gain (Loss) Recognized in Other Comprehensive Income (Loss), Effective Portion, Net	$ (5.7)	$ 0.8
Interest rate caps - derivative
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Cash Flow Hedge Derivative Instrument Assets at Fair Value	7.7	4.8
Interest rate caps - 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	6	3.6
Interest rate caps - derivative | Other Assets [Member]
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Cash Flow Hedge Derivative Instrument Assets at Fair Value	1.7	1.2
Forward foreign currency contracts | Prepaid Expenses and Other Current Assets [Member]
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Cash Flow Hedge Derivative Instrument Assets at Fair Value	3.2	0.4
Forward foreign currency contracts | Accrued Liabilities [Member]
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Cash Flow Hedge Derivative Instrument Assets at Fair Value	$ 0.2	$ 4

Summary of Significant Accou_14

Summary of Significant Accounting Policies - Amount of loss recognized in other comprehensive income, net of taxes (Details) - USD ($) $ in Millions	12 Months Ended
	Sep. 29, 2018	Sep. 30, 2017
Reclassification Adjustment out of Accumulated Other Comprehensive Income on Derivatives [Line Items]
Reclassification from Accumulated Other Comprehensive Income, Current Period, Net of Tax	$ 4	$ 4.5
Derivative Instruments, Gain (Loss) Recognized in Other Comprehensive Income (Loss), Effective Portion, Net	(5.7)	0.8
Accumulated Foreign Currency Adjustment Attributable to Parent [Member]
Reclassification Adjustment out of Accumulated Other Comprehensive Income on Derivatives [Line Items]
Reclassification from Accumulated Other Comprehensive Income, Current Period, Net of Tax	0	0
Equity securities
Reclassification Adjustment out of Accumulated Other Comprehensive Income on Derivatives [Line Items]
Reclassification from Accumulated Other Comprehensive Income, Current Period, Net of Tax	0.4	(2.4)
Interest rate caps - derivative
Reclassification Adjustment out of Accumulated Other Comprehensive Income on Derivatives [Line Items]
Reclassification from Accumulated Other Comprehensive Income, Current Period, Net of Tax	$ 3.6	$ 6.9

Summary of Significant Accou_15

Summary of Significant Accounting Policies - Schedule of Unrealized Loss Recognized in AOCI (Details) - USD ($) $ in Millions	12 Months Ended
	Sep. 29, 2018	Sep. 30, 2017	Sep. 24, 2016
Accounting Policies [Abstract]
(Gain) loss recognized in other comprehensive (loss) income, net	$ (5.7)	$ 0.8	$ (3.4)

Summary of Significant Accou_16

Summary of Significant Accounting Policies - Gain (Loss) on Fair Value Hedges Recognized in Earnings (Details) - USD ($) $ in Millions	12 Months Ended
	Sep. 29, 2018	Sep. 30, 2017	Sep. 24, 2016
Forward foreign currency contracts
Derivative Instruments, Gain (Loss) [Line Items]
Gain (Loss) on Fair Value Hedges Recognized in Earnings	$ 5.3	$ 0.5	$ 0.4

Summary of Significant Accou_17

Summary of Significant Accounting Policies - Accounts Receivable Reserve Activity (Detail) - USD ($) $ in Millions	12 Months Ended
	Sep. 29, 2018	Sep. 30, 2017	Sep. 24, 2016
Allowance for Doubtful Accounts Receivable [Roll Forward]
Balance at Beginning of Period	$ 9.8	$ 12.7	$ 11.1
Charged to Costs and Expenses	7	1.8	2
Write- offs and Payments	(0.6)	(4.7)	(0.4)
Balance at End of Period	$ 16.2	$ 9.8	$ 12.7

Summary of Significant Accou_18

Summary of Significant Accounting Policies - Reconciliation of Basic and Diluted Share Amounts (Detail) - shares shares in Thousands	12 Months Ended
	Sep. 29, 2018	Sep. 30, 2017	Sep. 24, 2016
Earnings Per Share [Line Items]
Basic weighted average common shares outstanding (in shares)	275,105	279,811	280,213
Weighted average common stock equivalents from assumed exercise of stock options and restricted stock units (in shares)	0	2,885	2,631
Incremental shares from convertible notes premium (in shares)	0	2,957	3,312
Diluted weighted average common shares outstanding (in shares)	275,105	285,653	286,156
Outstanding Stock Options and stock units [Member]
Weighted-average anti-dilutive shares related to:
Weighted-average anti-dilutive shares (in shares)	5,073	1,677	1,029
Convertible Notes
Weighted-average anti-dilutive shares related to:
Weighted-average anti-dilutive shares (in shares)	703	12	62

Summary of Significant Accou_19

Summary of Significant Accounting Policies - Product Warranty (Detail) - USD ($) $ in Millions	12 Months Ended
	Sep. 29, 2018	Sep. 30, 2017
Movement in Standard Product Warranty Accrual [Roll Forward]
Balance at Beginning of Period	$ 17	$ 5
Acquired	0	9.9
Provisions	18.3	15.3
Settlements/ Adjustments	(19.4)	(13.2)
Balance at End of Period	$ 15.9	$ 17

Business Combinations - Narrati

Business Combinations - Narrative (Details) - USD ($) $ / shares in Units, $ in Millions

Oct. 01, 2018

Jul. 31, 2018

Dec. 11, 2017

Apr. 07, 2017

Mar. 22, 2017

Sep. 29, 2018

Jun. 30, 2018

Mar. 31, 2018

Dec. 30, 2017

Sep. 30, 2017

Jul. 01, 2017

Apr. 01, 2017

Dec. 31, 2016

Sep. 30, 2017

Sep. 29, 2018

Sep. 30, 2017

Sep. 24, 2016

Business Acquisition [Line Items]

Goodwill impairment

$ 685.7

$ 685.7

$ 0

$ 0

Revenues

$ 813.5

$ 824

789.3

$ 791.1

$ 0.8

$ 0.8

$ 0.7

$ 0.7

3,217.9

3,058.8

2,832.7

Pre-tax loss

237.9

(1,370.2)

$ (548.6)

Goodwill

2,533.2

3,171.2

$ 3,171.2

2,533.2

$ 3,171.2

Cynosure

Business Acquisition [Line Items]

Purchase price (in dollars per share)

$ 66

Total purchase price

$ 1,660

Transaction costs

18.8

Intangible assets

$ 994

Goodwill impairment

685.7

Revenues

207.5

Pre-tax loss

$ 96.4

Goodwill

685.7

Property, plant and equipment

44.1

Cynosure | In-process research and development

Business Acquisition [Line Items]

Intangible assets

107

Estimated costs to complete

$ 18

Cynosure | Developed technology

Business Acquisition [Line Items]

Project fair value

$ 61

Impairment charge

$ 46

Weighted average period

11 years 9 months 18 days

Cynosure | Distribution agreement

Business Acquisition [Line Items]

Weighted average period

8 years

Cynosure | Customer relationships

Business Acquisition [Line Items]

Weighted average period

7 years 8 months 12 days

Cynosure | Trade names

Business Acquisition [Line Items]

Weighted average period

8 years 10 months 24 days

Cynosure | Minimum | Other intangible assets

Business Acquisition [Line Items]

Discount rate (as a percent)

11.00%

Cynosure | Minimum | In-process research and development

Business Acquisition [Line Items]

Discount rate (as a percent)

14.00%

Cynosure | Maximum | Other intangible assets

Business Acquisition [Line Items]

Discount rate (as a percent)

12.00%

Cynosure | Maximum | In-process research and development

Business Acquisition [Line Items]

Discount rate (as a percent)

22.00%

Medicor Medical Supply

Business Acquisition [Line Items]

Cash paid

$ 19

Intangible assets

$ 5.4

$ 5.4

Weighted average period

7 years 8 months 12 days

Acquisition price adjustment

$ 2

Purchase price withheld

1.9

Goodwill

8.9

Property, plant and equipment

$ 4.7

Emsor

Business Acquisition [Line Items]

Total purchase price

$ 16.3

Intangible assets

4.6

Purchase price withheld

$ 0.5

4.9

4.9

Payment period for contingent consideration

18 months

Goodwill

$ 5.7

Property, plant and equipment

$ 6

Faxitron

Business Acquisition [Line Items]

Total purchase price

$ 89

Intangible assets

53.4

53.4

Purchase price withheld

$ 11.7

$ 2.9

$ 2.9

Payment period for contingent consideration

1 year

Goodwill

$ 41.6

Faxitron | Customer relationships

Business Acquisition [Line Items]

Weighted average period

9 years

Faxitron | Trade names

Business Acquisition [Line Items]

Weighted average period

7 years

Faxitron | Minimum | In-process research and development

Business Acquisition [Line Items]

Discount rate (as a percent)

17.00%

Faxitron | Maximum | In-process research and development

Business Acquisition [Line Items]

Discount rate (as a percent)

19.00%

Subsequent Event | Focal

Business Acquisition [Line Items]

Total purchase price

$ 125

Cash paid

$ 108

Business Combinations - Purchas

Business Combinations - Purchase Price Allocation (Details) - USD ($) $ in Millions	Sep. 29, 2018	Jul. 31, 2018	Sep. 30, 2017	Mar. 22, 2017
Business Acquisition [Line Items]
Goodwill	$ 2,533.2		$ 3,171.2
Cynosure
Business Acquisition [Line Items]
Cash				$ 107.2
Marketable securities				82.9
Accounts receivable				40.2
Inventory				120
Property, plant and equipment				44.1
Other assets and liabilities, net				11.9
Accounts payable and accrued expenses				(76.6)
Deferred revenue				(11.2)
Capital lease obligation				(25.2)
Deferred income taxes, net				(315.2)
Goodwill				685.7
Purchase Price				1,657.8
Cynosure | Developed technology
Business Acquisition [Line Items]
Identifiable intangible assets				736
Cynosure | In-process research and development
Business Acquisition [Line Items]
Identifiable intangible assets				107
Cynosure | Distribution agreement
Business Acquisition [Line Items]
Identifiable intangible assets				42
Cynosure | Customer relationships
Business Acquisition [Line Items]
Identifiable intangible assets				35
Cynosure | Trade names
Business Acquisition [Line Items]
Identifiable intangible assets				$ 74
Faxitron
Business Acquisition [Line Items]
Cash		$ 2.4
Accounts receivable		4
Inventory		6
Other assets and liabilities, net		3.1
Accounts payable and accrued expenses		(4.9)
Deferred revenue		(1.9)
Deferred income taxes, net		(11.4)
Long-term debt		(3.3)
Goodwill		41.6
Purchase Price		89
Faxitron | Developed technology
Business Acquisition [Line Items]
Identifiable intangible assets		44.9
Faxitron | In-process research and development
Business Acquisition [Line Items]
Identifiable intangible assets		5.5
Faxitron | Customer relationships
Business Acquisition [Line Items]
Identifiable intangible assets		0.7
Faxitron | Trade names
Business Acquisition [Line Items]
Identifiable intangible assets		$ 2.3

Business Combinations Business

Business Combinations Business Combinations - Pro Forma (Details) - Cynosure - USD ($) $ / shares in Units, $ in Millions	12 Months Ended
	Sep. 30, 2017	Sep. 24, 2016
Business Acquisition [Line Items]
Revenue	$ 3,241.4	$ 3,244.6
Net income	$ 768.5	$ 252.3
Basic earnings per common share (in dollars per share)	$ 2.75	$ 0.90
Diluted earnings per common share (in dollars per share)	$ 2.69	$ 0.88

Restructuring Charges - Charges

Restructuring Charges - Charges Taken Related to Restructuring Actions (Detail) - Restructuring Charges - USD ($) $ in Millions	12 Months Ended
	Sep. 29, 2018	Sep. 30, 2017	Sep. 24, 2016
Fiscal 2016 charges:
Restructuring Cost and Reserve [Line Items]
Workforce reductions			$ 10.5
Fiscal restructuring charges			10.5
Fiscal 2017 charges:
Restructuring Cost and Reserve [Line Items]
Workforce reductions		$ 8.5
Facility closure costs		4.8
Fiscal restructuring charges		13.3
Fiscal 2018 charges:
Restructuring Cost and Reserve [Line Items]
Workforce reductions	$ 11.7
Facility closure costs	2.5
Fiscal restructuring charges	14.2
Fiscal 2018 Actions | Fiscal 2016 charges:
Restructuring Cost and Reserve [Line Items]
Workforce reductions			0
Fiscal restructuring charges			0
Fiscal 2018 Actions | Fiscal 2017 charges:
Restructuring Cost and Reserve [Line Items]
Workforce reductions		0
Facility closure costs		0
Fiscal restructuring charges		0
Fiscal 2018 Actions | Fiscal 2018 charges:
Restructuring Cost and Reserve [Line Items]
Workforce reductions	11.7
Facility closure costs	0.9
Fiscal restructuring charges	12.6
Fiscal 2017 Actions | Fiscal 2016 charges:
Restructuring Cost and Reserve [Line Items]
Workforce reductions			0
Fiscal restructuring charges			0
Fiscal 2017 Actions | Fiscal 2017 charges:
Restructuring Cost and Reserve [Line Items]
Workforce reductions		8.5
Facility closure costs		0
Fiscal restructuring charges		8.5
Fiscal 2017 Actions | Fiscal 2018 charges:
Restructuring Cost and Reserve [Line Items]
Workforce reductions	0
Facility closure costs	0
Fiscal restructuring charges	0
Fiscal 2016 Actions | Fiscal 2016 charges:
Restructuring Cost and Reserve [Line Items]
Workforce reductions			10.5
Fiscal restructuring charges			$ 10.5
Fiscal 2016 Actions | Fiscal 2017 charges:
Restructuring Cost and Reserve [Line Items]
Workforce reductions		0
Facility closure costs		4.8
Fiscal restructuring charges		$ 4.8
Fiscal 2016 Actions | Fiscal 2018 charges:
Restructuring Cost and Reserve [Line Items]
Workforce reductions	0
Facility closure costs	1.6
Fiscal restructuring charges	$ 1.6

Restructuring Charges - Charg_2

Restructuring Charges - Charges Taken Related to Accrued Restructuring Actions (Detail) - Restructuring Charges - USD ($) $ in Millions	12 Months Ended
	Sep. 29, 2018	Sep. 30, 2017	Sep. 24, 2016
Fiscal 2018 charges:
Restructuring Reserve [Roll Forward]
Fiscal restructuring charges	$ 14.2
Stock-based compensation	(1.3)
Severance payments	(13.7)
Other payments	(1.6)
Balance	9.1
Fiscal 2018 charges: | Fiscal 2018 Actions
Restructuring Reserve [Roll Forward]
Fiscal restructuring charges	12.6
Stock-based compensation	(1.3)
Severance payments	(6.8)
Other payments	(0.2)
Balance	4.3
Fiscal 2018 charges: | Fiscal 2017 Actions
Restructuring Reserve [Roll Forward]
Fiscal restructuring charges	0
Stock-based compensation	0
Severance payments	(6.7)
Other payments	0
Balance	0.8
Fiscal 2018 charges: | Fiscal 2016 Actions
Restructuring Reserve [Roll Forward]
Fiscal restructuring charges	1.6
Stock-based compensation	0
Severance payments	(0.2)
Other payments	(1.2)
Balance	3.9
Fiscal 2018 charges: | Previous Other Charges
Restructuring Reserve [Roll Forward]
Fiscal restructuring charges	0
Stock-based compensation	0
Severance payments	0
Other payments	(0.2)
Balance	0.1
Fiscal 2017 charges:
Restructuring Reserve [Roll Forward]
Balance	11.5
Fiscal restructuring charges		$ 13.3
Severance payments		(6.6)
Other payments		(1.5)
Balance		11.5
Fiscal 2017 charges: | Fiscal 2018 Actions
Restructuring Reserve [Roll Forward]
Balance	0
Fiscal restructuring charges		0
Severance payments		0
Other payments		0
Balance		0
Fiscal 2017 charges: | Fiscal 2017 Actions
Restructuring Reserve [Roll Forward]
Balance	7.5
Fiscal restructuring charges		8.5
Severance payments		(1)
Other payments		0
Balance		7.5
Fiscal 2017 charges: | Fiscal 2016 Actions
Restructuring Reserve [Roll Forward]
Balance	3.7
Fiscal restructuring charges		4.8
Severance payments		(5.4)
Other payments		(1.2)
Balance		3.7
Fiscal 2017 charges: | Previous Other Charges
Restructuring Reserve [Roll Forward]
Balance	$ 0.3
Fiscal restructuring charges		0
Severance payments		(0.2)
Other payments		(0.3)
Balance		0.3
Fiscal 2016 charges:
Restructuring Reserve [Roll Forward]
Balance		6.3
Fiscal restructuring charges			$ 10.5
Stock-based compensation			(0.4)
Severance payments			(9)
Other payments			(0.5)
Balance			6.3
Fiscal 2016 charges: | Fiscal 2018 Actions
Restructuring Reserve [Roll Forward]
Balance		0
Fiscal restructuring charges			0
Stock-based compensation			0
Severance payments			0
Other payments			0
Balance			0
Fiscal 2016 charges: | Fiscal 2017 Actions
Restructuring Reserve [Roll Forward]
Balance		0
Fiscal restructuring charges			0
Stock-based compensation			0
Severance payments			0
Other payments			0
Balance			0
Fiscal 2016 charges: | Fiscal 2016 Actions
Restructuring Reserve [Roll Forward]
Balance		5.5
Fiscal restructuring charges			10.5
Stock-based compensation			(0.4)
Severance payments			(4.6)
Other payments			0
Balance			5.5
Fiscal 2016 charges: | Previous Other Charges
Restructuring Reserve [Roll Forward]
Balance		$ 0.8
Fiscal restructuring charges			0
Stock-based compensation			0
Severance payments			(4.4)
Other payments			(0.5)
Balance			0.8
Fiscal 2015 charges:
Restructuring Reserve [Roll Forward]
Balance			5.7
Fiscal 2015 charges: | Fiscal 2018 Actions
Restructuring Reserve [Roll Forward]
Balance			0
Fiscal 2015 charges: | Fiscal 2017 Actions
Restructuring Reserve [Roll Forward]
Balance			0
Fiscal 2015 charges: | Fiscal 2016 Actions
Restructuring Reserve [Roll Forward]
Balance			0
Fiscal 2015 charges: | Previous Other Charges
Restructuring Reserve [Roll Forward]
Balance			$ 5.7

Restructuring Charges - Additio

Restructuring Charges - Additional Information (Detail) - USD ($) $ in Millions	3 Months Ended					12 Months Ended
	Jun. 30, 2018	Sep. 30, 2017	Jul. 01, 2017	Apr. 01, 2017	Dec. 31, 2016	Sep. 29, 2018
Restructuring Cost and Reserve [Line Items]
Severance charges						$ 9
Incremental cost						1.3
Cynosure
Restructuring Cost and Reserve [Line Items]
Severance charges		$ 1.3	$ 4.3	$ 1.5
Bedford
Restructuring Cost and Reserve [Line Items]
Facility closure costs	$ 1.6		$ 1.3		$ 3.5
International
Restructuring Cost and Reserve [Line Items]
Severance charges						0.6
Estimated severance and benefits future costs						2.2
Hicksville
Restructuring Cost and Reserve [Line Items]
Severance charges						0.3
Estimated severance and benefits future costs						0.5
Restructuring Charges | San Diego
Restructuring Cost and Reserve [Line Items]
Severance charges		1.4
Restructuring Charges | Bedford
Restructuring Cost and Reserve [Line Items]
Severance charges						$ 1.7
Restructuring Charges | International
Restructuring Cost and Reserve [Line Items]
Severance charges		$ 7.9

Borrowings and Credit Arrange_3

Borrowings and Credit Arrangements - Company's Borrowings (Detail) - USD ($) $ in Millions	Sep. 29, 2018	Sep. 30, 2017
Debt Instrument [Line Items]
Current debt obligations, net of debt discount	$ 599.7	$ 1,150.8
Convertible Notes	0	484.5
Total long-term debt obligations	2,704.6	2,172.1
Total debt obligations	3,304.3	3,322.9
Term Loan
Debt Instrument [Line Items]
Current debt obligations, net of debt discount	74.7	121.3
Long-term debt obligations, net of debt discount	1,376.3	1,190.5
Revolver
Debt Instrument [Line Items]
Current debt obligations, net of debt discount	300	345
Securitization Program
Debt Instrument [Line Items]
Current debt obligations, net of debt discount	225	200
2022 Senior Notes
Debt Instrument [Line Items]
Long-term debt obligations, net of debt discount	0	981.6
2025 Senior Notes
Debt Instrument [Line Items]
Long-term debt obligations, net of debt discount	935.2	0
2028 Senior Notes
Debt Instrument [Line Items]
Long-term debt obligations, net of debt discount	$ 393.1	$ 0

Borrowings and Credit Arrange_4

Borrowings and Credit Arrangements - Interest Expense Credit Agreement (Details) - USD ($) $ in Millions	12 Months Ended
	Sep. 29, 2018	Sep. 30, 2017	Sep. 24, 2016
Line of Credit Facility [Line Items]
Non-cash interest expense	$ 15	$ 49.4	$ 52.1
Amended and Restated Credit Agreement
Line of Credit Facility [Line Items]
Interest expense	60.8	42.3	40.4
Non-cash interest expense	$ 2.6	$ 4.2	$ 4.4
Weighted average interest rate	3.23%	2.39%	2.08%
Interest rate at end of period	3.74%	2.73%	2.05%

Borrowings and Credit Arrange_5

Borrowings and Credit Arrangements - Debt Maturity Schedule for Components of Company's Obligations (Details) $ in Millions	Sep. 29, 2018USD ($)
Debt Instrument [Line Items]
2,018	$ 600
2,019	75
2,020	112.5
2,021	150
2,022	1,050
2024 and Thereafter	1,350
Total	3,337.5
Term Loan
Debt Instrument [Line Items]
2,018	75
2,019	75
2,020	112.5
2,021	150
2,022	1,050
2024 and Thereafter	0
Total	1,462.5
Revolver
Debt Instrument [Line Items]
2,018	300
2,019	0
2,020	0
2,021	0
2,022	0
2024 and Thereafter	0
Total	300
Securitization Program
Debt Instrument [Line Items]
2,018	225
2,019	0
2,020	0
2,021	0
2,022	0
2024 and Thereafter	0
Total	225
2025 Senior Notes
Debt Instrument [Line Items]
2,018	0
2,019	0
2,020	0
2,021	0
2,022	0
2024 and Thereafter	950
Total	950
2028 Senior Notes
Debt Instrument [Line Items]
2,018	0
2,019	0
2,020	0
2,021	0
2,022	0
2024 and Thereafter	400
Total	$ 400

Borrowings and Credit Arrange_6

Borrowings and Credit Arrangements - Additional Information (Detail)	Oct. 01, 2018USD ($)	Jan. 19, 2018USD ($)	Dec. 19, 2016	Nov. 09, 2016	Feb. 14, 2013USD ($)	Feb. 29, 2012USD ($)	Dec. 10, 2007USD ($)	Dec. 10, 2007USD ($)	Jun. 30, 2018USD ($)	Mar. 31, 2018USD ($)	Dec. 30, 2017USD ($)$ / shares	Sep. 30, 2017USD ($)	Jul. 01, 2017USD ($)$ / shares	Dec. 31, 2016USD ($)	Sep. 24, 2016USD ($)	Mar. 26, 2016USD ($)$ / shares	Dec. 25, 2010	Apr. 01, 2017USD ($)	Sep. 29, 2018USD ($)$ / shares	Sep. 30, 2017USD ($)	Sep. 24, 2016USD ($)	Apr. 20, 2018USD ($)	Feb. 15, 2018USD ($)	Oct. 10, 2017USD ($)	Oct. 03, 2017USD ($)	Apr. 21, 2017USD ($)	May 29, 2015USD ($)	Nov. 18, 2010USD ($)
Debt Instrument [Line Items]
Proceeds from issuance of senior long-term debt		$ 1,000,000,000
Proceeds from amounts borrowed under revolving credit line																			$ 1,150,000,000	$ 345,000,000	$ 50,000,000
Notes principal amount													$ 100,000,000
Senior Notes		$ 600,000,000																						$ 350,000,000
Non-cash interest expense amortization of debt discount and deferred financing costs																			15,000,000	49,400,000	52,100,000
Debt extinguishment loss										$ 44,900,000			2,600,000						45,900,000	3,200,000	5,300,000
Payment of debt issuance costs																			23,500,000	0	0
Principal amount of borrowings																			1,000,000,000
Repayments of convertible debt													269,100,000	$ 12,300,000					546,200,000	396,200,000	392,800,000
Current portion of long-term debt												$ 1,150,800,000							599,700,000	1,150,800,000
Conversion premium																		$ 8,700,000
Deferred taxes, reacquisition of equity component											$ 3,800,000
Adjustments to APIC, equity component of convertible debt											13,400,000								(40,700,000)	(33,900,000)	(94,400,000)
Maximum borrowing under securitization program									$ 225,000,000
Accretion expense													$ 18,500,000
Debt issuance costs, net																			1,500,000
Debt discount																			$ 1,500,000
Amended Credit Agreement
Debt Instrument [Line Items]
Leverage ratio maximum																			5
Interest coverage ratio																			3.75
Decreased net leverage ratio																			4.50
Debt extinguishment loss											1,000,000
Maximum range of present value of cash flow, percentage										10.00%									10.00%
Third-party costs											1,700,000
Payment of debt issuance costs											4,900,000
Amended Term Loan
Debt Instrument [Line Items]
Proceeds from issuance of debt																			$ 1,800,000,000
Amended Term Loan | Percentage Added to Eurodollar Rate
Debt Instrument [Line Items]
Basis spread on variable rate																			1.50%
2013 Notes
Debt Instrument [Line Items]
Notes principal amount																			$ 68,000,000
Debt extinguishment loss																			(2,300,000)
Repayments of convertible debt												82,900,000
Conversion price (in dollars per share) | $ / shares													$ 38.59
Accretion expense												13,300,000
Credit Agreement
Debt Instrument [Line Items]
Repayments of secured debt																			1,320,000,000
Proceeds under credit agreement																											$ 1,680,000,000
Principal amount of borrowings																			$ 1,760,000,000
2025 Senior Notes
Debt Instrument [Line Items]
Interest rate																			4.375%
2022 Notes
Debt Instrument [Line Items]
Senior Notes																							$ 1,000,000,000
Debt extinguishment loss										$ 44,900,000
Third-party costs										2,600,000
Interest rate																			5.25%
Offering price, percentage of principal amount																							1,040,000,000
Make whole provision																							$ 37,700,000
Convertible Notes | 2007 Notes
Debt Instrument [Line Items]
Notes principal amount					$ 370,000,000	$ 500,000,000	$ 1,725,000,000	$ 1,725,000,000																				$ 450,000,000
Interest rate							2.00%	2.00%
Proceeds from issuance of convertible debt							$ 1,725,000,000
Convertible Notes Payable
Debt Instrument [Line Items]
Repayments of convertible debt									165,000,000
Securitization Program
Debt Instrument [Line Items]
Basis spread on variable rate																			0.70%
Weighted average interest rate																			2.42%
Interest expense																			$ 5,400,000	3,300,000	1,100,000
Principal amount of borrowings																			$ 225,000,000
Term of accounts receivable securitization program																			1 year
Accounts receivable from securitization																			$ 200,000,000
Maximum borrowing under securitization program																						$ 200,000,000
Securitization Program | Maximum
Debt Instrument [Line Items]
Accounts receivable from securitization																			200,000,000							$ 200,000,000
2012 Notes
Debt Instrument [Line Items]
Notes principal amount																			17,900,000
Debt extinguishment loss																			$ (900,000)
Repayments of convertible debt												23,100,000
Conversion price (in dollars per share) | $ / shares													$ 31.175
Revolver
Debt Instrument [Line Items]
Proceeds from amounts borrowed under revolving credit line									250,000,000
Amended Revolver
Debt Instrument [Line Items]
Amount of credit outstanding																									$ 1,500,000,000
Amended Revolver | Percentage Added to Eurodollar Rate
Debt Instrument [Line Items]
Basis spread on variable rate																			1.50%
2012 Notes
Debt Instrument [Line Items]
Notes principal amount											39,300,000
Repayments of convertible debt									$ 243,300,000		52,800,000
Repurchase amount										200,500,000
Deferred taxes, reacquisition of equity component										12,000,000
Debt instrument remaining to be redeemed											$ 5,500,000
Adjustments to APIC, equity component of convertible debt										$ 42,800,000
Conversion price (in dollars per share) | $ / shares											$ 31.175
2013 Notes
Debt Instrument [Line Items]
Notes principal amount											$ 300,000
Repayments of convertible debt											244,100,000
Repurchase amount											$ 201,700,000
2012 and 2013 Notes
Debt Instrument [Line Items]
Debt extinguishment loss												(600,000)
2010 Original Notes | Convertible Notes
Debt Instrument [Line Items]
Notes principal amount																			$ 46,300,000
Debt extinguishment loss															$ 800,000
Repayments of convertible debt															79,200,000
Conversion price of notes (in dollars per share) | $ / shares																			$ 23.03
Principle convertible debt put during period															$ 1,300,000
2010 Original Notes | Convertible Notes Payable
Debt Instrument [Line Items]
Repayments of convertible debt																$ 140,100,000
Conversion price of notes (in dollars per share) | $ / shares																$ 23.03
2012 Notes | Convertible Notes Payable
Debt Instrument [Line Items]
Notes principal amount																$ 136,600,000
Debt extinguishment loss																			$ (700,000)
Repayments of convertible debt																$ 171,300,000
Conversion price of notes (in dollars per share) | $ / shares																$ 31.175
2028 Senior Notes
Debt Instrument [Line Items]
Notes principal amount																			400,000,000
Principal amount of borrowings																			$ 950,000,000
Offering price, percent of face value																			100.00%
Long-term debt obligations												0							$ 393,100,000	0
Amended Term Loan | Amended Credit Agreement | Minimum
Debt Instrument [Line Items]
Periodic payment, principal																			$ 9,375,000
Periodic payment, principal, period																			3 months
Amended Term Loan | Amended Credit Agreement | Maximum
Debt Instrument [Line Items]
Periodic payment, principal																			$ 37,500,000
Secured Term Loan | Amended Term Loan
Debt Instrument [Line Items]
Amount of credit outstanding																									$ 1,500,000,000
Securitization Program
Debt Instrument [Line Items]
Notes principal amount																			$ 225,000,000
Weighted average interest rate																			2.24%
Current portion of long-term debt												200,000,000							$ 225,000,000	200,000,000
Convertible Notes Payable
Debt Instrument [Line Items]
Interest expense																			7,100,000	41,000,000	50,000,000
Non-cash interest expense amortization of debt discount and deferred financing costs																			5,300,000	34,300,000	40,000,000
Debt extinguishment loss																$ (4,500,000)			(5,300,000)
Convertible Notes Payable | 2012 and 2013 Notes
Debt Instrument [Line Items]
Deferred taxes, reacquisition of equity component																			31,100,000
Adjustments to APIC, equity component of convertible debt																			58,600,000
Convertible Notes Payable | 2010 Original Notes
Debt Instrument [Line Items]
Debt extinguishment loss																			(4,600,000)
Convertible Notes Payable | 2010 and 2012 Notes
Debt Instrument [Line Items]
Deferred taxes, reacquisition of equity component																			28,200,000
Adjustments to APIC, equity component of convertible debt																			122,600,000
Term Loan
Debt Instrument [Line Items]
Long-term debt obligations												1,190,500,000							1,376,300,000	1,190,500,000
Current portion of long-term debt												121,300,000							74,700,000	121,300,000
Term Loan | Credit Agreement
Debt Instrument [Line Items]
Amount of credit outstanding																			$ 1,500,000,000
Debt instrument, maturity date																			May 29, 2020
Revolver
Debt Instrument [Line Items]
Current portion of long-term debt												$ 345,000,000							$ 300,000,000	345,000,000
Revolver | Credit Agreement
Debt Instrument [Line Items]
Amount of credit outstanding																			$ 1,000,000,000
Debt instrument, maturity date																			May 29, 2020
2007 Notes | Convertible Notes
Debt Instrument [Line Items]
Debt instrument, maturity period								2,037
November 18, 2010 Original Notes | Convertible Notes
Debt Instrument [Line Items]
Notes principal amount																												$ 450,000,000
Interest rate																												2.00%
Debt instrument, maturity period																	2,037
November 18, 2010 Original Notes | Convertible Notes Payable
Debt Instrument [Line Items]
Notes principal amount																$ 90,000,000
February 29, 2012 Original Notes | Convertible Notes
Debt Instrument [Line Items]
Notes principal amount						$ 500,000,000
Interest rate						2.00%
Debt instrument, maturity period						2,042
February 14, 2013 Original Notes | Convertible Notes
Debt Instrument [Line Items]
Notes principal amount					$ 370,000,000
Interest rate					2.00%
Debt instrument, maturity period					2,043
Convertible Debt | 2042 Notes
Debt Instrument [Line Items]
Interest rate									2.00%
Convertible Debt | 2010 Notes
Debt Instrument [Line Items]
Redemption price, percentage			100.00%	100.00%
Senior Notes
Debt Instrument [Line Items]
Non-cash interest expense amortization of debt discount and deferred financing costs																			$ 3,600,000	3,900,000	3,800,000
Senior Notes | 2025 Senior Notes
Debt Instrument [Line Items]
Non-cash interest expense amortization of debt discount and deferred financing costs																			$ 1,600,000	0	0
Interest rate																			4.375%
Offering price, percent of face value		100.00%																	100.00%					100.00%
Redemption price, percentage																			35.00%
Percentage of redemption price, second period																			104.375%
Percentage of redemption price, third period																			102.188%
Percentage of redemption price, fourth period																			101.094%
Percentage redemption price, sixth period																			100.00%
Percentage price of principal amount for repurchase of senior notes																			101.00%
Senior Notes | 2028 Senior Notes
Debt Instrument [Line Items]
Non-cash interest expense amortization of debt discount and deferred financing costs																			$ 500,000	$ 0	$ 0
Interest rate																			4.625%
Offering price, percent of face value																			100.00%
Redemption price, percentage																			35.00%
Percentage of redemption price, second period																			104.625%
Percentage of redemption price, third period																			102.312%
Percentage of redemption price, fourth period																			101.541%
Percentage of redemption price, fifth period																			100.77%
Percentage redemption price, sixth period																			100.00%
Percentage price of principal amount for repurchase of senior notes																			101.00%
Subsequent Event | Convertible Notes Payable
Debt Instrument [Line Items]
Repayments of convertible debt	$ 50,000,000
March 1, 2018 | 2012 Notes
Debt Instrument [Line Items]
Redemption price as percentage of principle amount plus accrued and unpaid interest																			100.00%
March 6, 2018 | 2012 Notes
Debt Instrument [Line Items]
Redemption price as percentage of principle amount plus accrued and unpaid interest																			100.00%

Borrowings and Credit Arrange_7

Borrowings and Credit Arrangements - Convertible Notes and Related Equity Components (Details) - USD ($)	12 Months Ended
	Sep. 30, 2017	Jul. 01, 2017
Schedule Of Borrowings [Line Items]
Notes principal amount		$ 100,000,000
2012 Notes
Schedule Of Borrowings [Line Items]
Notes principal amount	$ 245,400,000
Unamortized discount and issuance costs	(1,900,000)
Net carrying amount	243,500,000
Equity component, net of taxes	24,100,000
Two Thousand And Thirteen Notes [Member]
Schedule Of Borrowings [Line Items]
Notes principal amount	202,000,000
Unamortized discount and issuance costs	(1,800,000)
Net carrying amount	241,000,000
Equity component, net of taxes	71,800,000
Principal accretion	$ 40,800,000

Borrowings and Credit Arrange_8

Borrowings and Credit Arrangements - Interest Expense under Convertible Notes (Detail) - USD ($) $ in Millions	12 Months Ended
	Sep. 29, 2018	Sep. 30, 2017	Sep. 24, 2016
Debt Conversion [Line Items]
Non-cash interest expense	$ 15	$ 49.4	$ 52.1
Convertible Notes Payable
Debt Conversion [Line Items]
Amortization of debt discount	3.5	17.9	22.3
Amortization of deferred financing costs	0.2	0.8	1.1
Principal accretion	1.6	15.6	16.6
Non-cash interest expense	5.3	34.3	40
2.00% accrued interest	1.8	6.7	10
Interest expense, net	$ 7.1	$ 41	$ 50

Borrowings and Credit Arrange_9

Borrowings and Credit Arrangements - Interest Expense Senior Notes (Details) - USD ($) $ in Millions	12 Months Ended
	Sep. 29, 2018	Sep. 30, 2017	Sep. 24, 2016
Debt Instrument [Line Items]
Non-cash interest expense	$ 15	$ 49.4	$ 52.1
2025 Senior Notes
Debt Instrument [Line Items]
Interest rate	4.375%
Senior Notes
Debt Instrument [Line Items]
Interest expense	$ 69.2	57.3	56
Non-cash interest expense	3.6	3.9	3.8
Senior Notes | 2028 Senior Notes
Debt Instrument [Line Items]
Interest expense	13.3	0	0
Non-cash interest expense	$ 0.5	0	0
Interest rate	4.625%
Senior Notes | 2025 Senior Notes
Debt Instrument [Line Items]
Interest expense	$ 34.7	0	0
Non-cash interest expense	$ 1.6	0	0
Interest rate	4.375%
Senior Notes | 2022 Senior Notes
Debt Instrument [Line Items]
Interest expense	$ 21.2	57.3	56
Non-cash interest expense	$ 1.5	$ 3.9	$ 3.8
Interest rate	5.25%

Fair Value Measurements - Fair

Fair Value Measurements - Fair Value Assets and Liabilities Measured on Recurring Basis (Detail) - USD ($)	Sep. 29, 2018	Sep. 30, 2017
Assets:
Assets measured at fair value on a recurring basis	$ 10,900,000	$ 5,300,000
Liabilities:
Liabilities measured at fair value on a recurring basis	8,000,000	4,000,000
Quoted Prices in Active Market for Identical Assets (Level 1)
Assets:
Assets measured at fair value on a recurring basis	0	100,000
Liabilities:
Liabilities measured at fair value on a recurring basis	0	0
Significant Other Observable Inputs (Level 2)
Assets:
Assets measured at fair value on a recurring basis	10,900,000	5,200,000
Liabilities:
Liabilities measured at fair value on a recurring basis	200,000	4,000,000
Significant Unobservable Inputs (Level 3)
Assets:
Assets measured at fair value on a recurring basis	0	0
Liabilities:
Liabilities measured at fair value on a recurring basis	7,800,000	0
Equity securities
Assets:
Assets measured at fair value on a recurring basis		100,000
Equity securities | Quoted Prices in Active Market for Identical Assets (Level 1)
Assets:
Assets measured at fair value on a recurring basis		100,000
Equity securities | Significant Other Observable Inputs (Level 2)
Assets:
Assets measured at fair value on a recurring basis		0
Equity securities | Significant Unobservable Inputs (Level 3)
Assets:
Assets measured at fair value on a recurring basis		0
Interest rate caps - derivative
Assets:
Interest rate caps - derivative	7,700,000	4,800,000
Interest rate caps - derivative | Quoted Prices in Active Market for Identical Assets (Level 1)
Assets:
Assets measured at fair value on a recurring basis		0
Interest rate caps - derivative	0
Interest rate caps - derivative | Significant Other Observable Inputs (Level 2)
Assets:
Assets measured at fair value on a recurring basis		4,800,000
Interest rate caps - derivative	7,700,000
Interest rate caps - derivative | Significant Unobservable Inputs (Level 3)
Assets:
Assets measured at fair value on a recurring basis		0
Interest rate caps - derivative	0
Forward foreign currency contracts
Liabilities:
Liabilities measured at fair value on a recurring basis		4,000,000
Forward foreign currency contracts | Quoted Prices in Active Market for Identical Assets (Level 1)
Liabilities:
Liabilities measured at fair value on a recurring basis		0
Forward foreign currency contracts | Significant Other Observable Inputs (Level 2)
Liabilities:
Liabilities measured at fair value on a recurring basis		4,000,000
Forward foreign currency contracts | Significant Unobservable Inputs (Level 3)
Liabilities:
Liabilities measured at fair value on a recurring basis		0
Forward foreign currency contracts | Assets
Assets:
Interest rate caps - derivative		4,800,000
Forward foreign currency contracts	3,200,000	400,000
Forward foreign currency contracts | Assets | Quoted Prices in Active Market for Identical Assets (Level 1)
Assets:
Interest rate caps - derivative		0
Forward foreign currency contracts	0
Forward foreign currency contracts | Assets | Significant Other Observable Inputs (Level 2)
Assets:
Interest rate caps - derivative		400,000
Forward foreign currency contracts	3,200,000
Forward foreign currency contracts | Assets | Significant Unobservable Inputs (Level 3)
Assets:
Interest rate caps - derivative		$ 0
Forward foreign currency contracts	0
Forward foreign currency contracts | Liability
Liabilities:
Liabilities measured at fair value on a recurring basis	200,000
Forward foreign currency contracts | Liability | Quoted Prices in Active Market for Identical Assets (Level 1)
Liabilities:
Liabilities measured at fair value on a recurring basis	0
Forward foreign currency contracts | Liability | Significant Other Observable Inputs (Level 2)
Liabilities:
Liabilities measured at fair value on a recurring basis	200,000
Forward foreign currency contracts | Liability | Significant Unobservable Inputs (Level 3)
Liabilities:
Liabilities measured at fair value on a recurring basis	0
Contingent Consideration Type [Domain]
Liabilities:
Liabilities measured at fair value on a recurring basis	7,800,000
Contingent Consideration Type [Domain] | Quoted Prices in Active Market for Identical Assets (Level 1)
Liabilities:
Liabilities measured at fair value on a recurring basis	0
Contingent Consideration Type [Domain] | Significant Other Observable Inputs (Level 2)
Liabilities:
Liabilities measured at fair value on a recurring basis	0
Contingent Consideration Type [Domain] | Significant Unobservable Inputs (Level 3)
Liabilities:
Liabilities measured at fair value on a recurring basis	$ 7,800,000

Fair Value Measurements - Addit

Fair Value Measurements - Additional Information (Detail) - USD ($)	3 Months Ended	12 Months Ended
	Mar. 31, 2018	Sep. 29, 2018	Sep. 30, 2017	Sep. 24, 2016
Fair Value, Off-balance Sheet Risks, Disclosure Information [Line Items]
Investments, fair value		$ 10,900,000	$ 5,300,000
Borrowed principal under credit agreement		1,000,000,000
Impairment of Intangible Assets, Indefinite-lived (Excluding Goodwill)	$ 46,000,000	46,000,000	0	$ 0
Goodwill impairment charge	$ 685,700,000	685,700,000	0	$ 0
Credit Agreement
Fair Value, Off-balance Sheet Risks, Disclosure Information [Line Items]
Borrowed principal under credit agreement		1,760,000,000
Securitization Program
Fair Value, Off-balance Sheet Risks, Disclosure Information [Line Items]
Borrowed principal under credit agreement		225,000,000
Significant Unobservable Inputs (Level 3)
Fair Value, Off-balance Sheet Risks, Disclosure Information [Line Items]
Investments, fair value		0	$ 0
2028 Senior Notes
Fair Value, Off-balance Sheet Risks, Disclosure Information [Line Items]
Fair value of debt instrument		377,000,000
2025 Senior Notes
Fair Value, Off-balance Sheet Risks, Disclosure Information [Line Items]
Fair value of debt instrument		$ 909,600,000

Fair Value Measurements - Estim

Fair Value Measurements - Estimated Fair Values of Convertible Notes (Detail) $ in Millions	Sep. 30, 2017USD ($)
Estimated Fair Value Of Financial Instruments [Line Items]
Estimated fair values of debt instruments	$ 541.7
2012 Notes
Estimated Fair Value Of Financial Instruments [Line Items]
Estimated fair values of debt instruments	297.3
2013 Notes
Estimated Fair Value Of Financial Instruments [Line Items]
Estimated fair values of debt instruments	$ 244.4

Income Taxes - Income (Loss) Be

Income Taxes - Income (Loss) Before Income Taxes (Detail) - USD ($) $ in Millions	3 Months Ended	12 Months Ended
	Sep. 30, 2017	Sep. 29, 2018	Sep. 30, 2017	Sep. 24, 2016
Income Tax Disclosure [Abstract]
Domestic	$ 1,105.8	$ (581.9)		$ 310.7
Foreign	124.7	163.3		104.6
(Loss) income before income taxes	$ 1,230.5	$ (418.6)	$ 1,230.5	$ 415.3

Income Taxes - Provision for In

Income Taxes - Provision for Income Taxes (Detail) - USD ($) $ in Millions	3 Months Ended	12 Months Ended
	Dec. 30, 2017	Sep. 29, 2018	Sep. 30, 2017	Sep. 24, 2016
Federal:
Current		$ 137.1	$ 701.1	$ 209
Deferred		(461.9)	(276.9)	(122.7)
Federal, Total		(324.8)	424.2	86.3
State:
Current		11	53.1	16.6
Deferred		(11.3)	(15.9)	(22.7)
State, Total		(0.3)	37.2	(6.1)
Foreign:
Current		21.9	13.9	14.7
Deferred		(4.1)	(0.3)	(10.4)
Foreign, Total		17.8	13.6	4.3
Provision for income taxes	$ 329.2	$ (307.3)	$ 475	$ 84.5

Income Taxes - Reconciliation o

Income Taxes - Reconciliation of Income Tax (Benefit) at U.S. Federal Statutory Rate to Company's Effective Tax Rate (Detail)	12 Months Ended
	Sep. 29, 2018	Sep. 30, 2017	Sep. 24, 2016
Income Tax Disclosure [Abstract]
Income tax (benefit) provision at federal statutory rate	24.50%	35.00%	35.00%
Increase (decrease) in tax resulting from:
Domestic production activities deduction	3.10%	(1.70%)	(5.00%)
State income taxes, net of federal benefit	(0.70%)	2.30%	2.00%
Non-deductible goodwill	(39.40%)	9.20%	0.00%
Tax credits	1.90%	(0.80%)	(3.20%)
Tax reform	82.70%	0.00%	0.00%
Unrecognized tax benefits	(1.80%)	(1.40%)	2.40%
Compensation	(0.30%)	(0.50%)	0.10%
Foreign rate differential	5.20%	(2.60%)	(6.10%)
Change in deferred tax rate	(1.20%)	0.20%	(1.80%)
Change in valuation allowance	0.50%	(1.50%)	(3.40%)
Other	(1.10%)	0.40%	0.30%
Effective income tax rate	73.40%	38.60%	20.30%

Income Taxes - Significant Comp

Income Taxes - Significant Components of Company's Deferred Tax Assets and Liabilities (Detail) - USD ($) $ in Millions	Sep. 29, 2018	Sep. 30, 2017
Deferred tax assets
Net operating loss carryforwards	$ 30.9	$ 50.1
Capital losses	6.5	7.1
Non-deductible accruals	30.7	50.6
Non-deductible reserves	22.1	30
Stock-based compensation	24	39.3
Research and other credits	13.3	13.6
Nonqualified deferred compensation plan	12.3	16.4
Other temporary differences	11.5	16.5
Deferred tax assets, gross	151.3	223.6
Less: valuation allowance	(25.5)	(28.2)
Deferred tax assets, net	125.8	195.4
Deferred tax liabilities
Depreciation and amortization	(606.6)	(1,071.5)
Debt discounts and deferrals	(4.5)	(88.4)
Deferred tax liabilities, net	(611.1)	(1,159.9)
Net deferred tax liabilities	$ (485.3)	$ (964.5)

Income Taxes - Additional Infor

Income Taxes - Additional Information (Detail) - USD ($)	1 Months Ended	3 Months Ended		12 Months Ended
	Jan. 31, 2018	Sep. 29, 2018	Dec. 30, 2017	Sep. 29, 2018	Sep. 30, 2017
Income Taxes [Line Items]
Additional estimated net income tax benefit				$ 346,200,000
Decrease in valuation allowance				2,700,000
Federal net operating loss expected to be expired unutilized		$ 4,500,000		4,500,000
State net operating loss expected to be expired unutilized		85,100,000		85,100,000
Foreign net operating loss expected to be expired unutilized		46,400,000		46,400,000
Gross unrecognized tax benefits, excluding interest		89,500,000		89,500,000	$ 90,300,000
Unrecognized tax benefit that would impact effective tax rate		79,000,000		79,000,000	70,300,000
Unrecognized tax benefits, period decrease				(800,000)
Interest accrued on unrecognized tax benefits		9,000,000		9,000,000	$ 5,300,000
Income tax penalties accrued		0		0
Payments for other taxes				1,700,000
Recognized tax benefit due to reversal of unrecognized tax benefit				10,900,000
Non-income tax loss				35,600,000
Effective Income Tax Rate Reconciliation, Tax Settlement, State and Local, Amount	$ 11,000,000
Reduction in tax benefit		8,000,000
General and Administrative Expense
Income Taxes [Line Items]
Non-income tax loss			$ (4,000,000)
Income tax refund		12,400,000		12,400,000
Convertible Debt Securities
Income Taxes [Line Items]
Unrecognized tax benefits, period decrease				10,400,000
Settlement with Taxing Authority
Income Taxes [Line Items]
Unrecognized tax benefits, period decrease				9,600,000
Net Operating Losses Carryforwards
Income Taxes [Line Items]
Amount with unlimited carry forward periods				34,500,000
Tax Credit Carryforward
Income Taxes [Line Items]
Amount with unlimited carry forward periods				2,000,000
Maximum
Income Taxes [Line Items]
Decrease in unrecognized tax benefits is reasonably possible		4,800,000		4,800,000
Domestic Tax Authority
Income Taxes [Line Items]
Net operating losses		9,800,000		9,800,000
Credit carry forwards		4,600,000		4,600,000
State and Local Jurisdiction
Income Taxes [Line Items]
Net operating losses		46,900,000		46,900,000
Credit carry forwards		9,400,000		9,400,000
Foreign Tax Authority
Income Taxes [Line Items]
Net operating losses		35,900,000		35,900,000
Credit carry forwards		$ 1,200,000		$ 1,200,000

Income Taxes - Activity of Comp

Income Taxes - Activity of Company's Unrecognized Income Tax Benefits (Detail) - USD ($) $ in Millions	12 Months Ended
	Sep. 29, 2018	Sep. 30, 2017
Income Tax Disclosure [Abstract]
Balance at beginning of fiscal year	$ 90.3	$ 163.6
Tax positions related to current year:
Additions	9	21.8
Reductions	0	0
Tax positions related to prior years:
Additions related to change in estimate	6.6	1.1
Reductions	(15.4)	(77.3)
Payments	0	(1.6)
Lapses in statutes of limitations	(1.4)	(19.9)
Acquired tax positions:
Additions related to reserves acquired from acquisitions	0.4	2.6
Balance as of the end of the fiscal year	$ 89.5	$ 90.3

Stockholders' Equity and Stoc_3

Stockholders' Equity and Stock-Based Compensation - Additional Information (Detail) - USD ($) $ / shares in Units, shares in Millions	1 Months Ended		2 Months Ended	3 Months Ended		12 Months Ended
	Dec. 31, 2013	Mar. 31, 2012	Nov. 20, 2018	Sep. 29, 2018	Sep. 30, 2017	Sep. 29, 2018	Sep. 30, 2017	Sep. 24, 2016	Jun. 21, 2016	Jun. 13, 2016	Nov. 11, 2013
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Remaining authorized repurchase amount				$ 411,500,000		$ 411,500,000
Authorized value of common shares to be repurchased										$ 500,000,000
Percentage of award vested upon meeting defined market based criteria	33.33%
Restricted stock units liability award	0.2
Stock purchased by employees	0.2
Share-based compensation liabilities paid						$ 7,800,000
Stock-based compensation, period of vest term granted to employees, years						3 years
Cliff vesting period from grant date						3 years
Tax benefit related to stock based compensation					$ 22,600,000	$ 11,700,000		$ 23,100,000
Intrinsic value of option exercised					25,900,000	$ 15,200,000		21,600,000
Granted						1.7
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%
Stock-based compensation expense					68,200,000	$ 65,000,000	$ 68,200,000	65,400,000
Shares repurchased (in shares)				2.3		5
Common stock repurchases				$ 88,500,000		$ 187,300,000
Minimum
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Percentage of forfeiture rates						0.00%
Maximum
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Percentage of forfeiture rates						7.00%
Stock Options
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock-based compensation expense					12,200,000	$ 14,300,000		10,900,000
Unrecognized compensation expense				25,400,000		$ 25,400,000
Weighted average period of unrecognized stock-based compensation, years						2 years 7 months 8 days
Stock Options | Minimum
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock-based compensation, period of vest term granted to employees, years						4 years
Percentage of vesting for stock options granted to employees						25.00%
Stock Options | Maximum
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock-based compensation, period of vest term granted to employees, years						5 years
Percentage of vesting for stock options granted to employees						20.00%
Convertible notes
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Restricted stock vesting period	3 years
Stock-based compensation expense					51,600,000	$ 46,500,000		50,500,000
Unrecognized compensation expense				$ 58,700,000		$ 58,700,000
Weighted average period of unrecognized stock-based compensation, years						1 year 11 months 5 days
Fair value of RSUs vested					$ 39,500,000	$ 38,900,000		$ 28,400,000
Convertible notes | Minimum
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock-based compensation, period of vest term granted to employees, years						3 years
Percentage of vesting for RSUs granted to employees						25.00%
Convertible notes | Maximum
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock-based compensation, period of vest term granted to employees, years						4 years
Percentage of vesting for RSUs granted to employees						33.00%
Performance Shares
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Granted					0.2	0.6		0.3
Market Based Stock Units
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Cliff vesting period from grant date						3 years
Granted						0.3	0.1
Vested, weighted average grant date fair value (in usd per share)						$ 49.44	$ 48.98
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%
2008 Equity Plan
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Common stock, shares authorized				31.5		31.5
Shares available for grant				8.6		8.6
2012 Employee Stock Purchase Plan
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of shares that may be issued under Employee Stock Purchase Plan		2.5
Percentage of common stock price for ESPP		85.00%
Stock-based compensation expense					$ 4,400,000	$ 4,000,000		$ 4,000,000
Nov 11, 2013
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Authorized value of common shares to be repurchased											$ 250,000,000
Period available for common stock to be repurchased						3 years
Repurchase of common stock (in shares)					7.3
Total consideration						$ 250,000,000
Jun 21 2016
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Authorized value of common shares to be repurchased									$ 500,000,000
Period available for common stock to be repurchased						5 years
June 21, 2016
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Repurchase of common stock (in shares)						5.3
Repurchased of stock, value						$ 200,100,000
Subsequent Event
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares repurchased (in shares)			1.5
Common stock repurchases			$ 60,600,000

Stockholders' Equity and Stoc_4

Stockholders' Equity and Stock-Based Compensation - Stock-Based Compensation Expense in Consolidated Statement of Operations (Detail) - USD ($) $ in Millions	3 Months Ended	12 Months Ended
	Sep. 30, 2017	Sep. 29, 2018	Sep. 30, 2017	Sep. 24, 2016
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock-based compensation expense	$ 68.2	$ 65	$ 68.2	$ 65.4
Cost of revenues
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock-based compensation expense	10.7	8.3		10.5
Research and development
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock-based compensation expense	11.2	9.5		10.8
Selling and marketing
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock-based compensation expense	11.9	10.3		10.9
General and Administrative Expense
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock-based compensation expense	34.4	35.6		32.8
Restructuring Charges
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock-based compensation expense	$ 0	$ 1.3		$ 0.4

Stockholders' Equity and Stoc_5

Stockholders' Equity and Stock-Based Compensation - Information Pertaining to Stock Options Granted and Related Assumptions (Detail) - USD ($) $ / shares in Units, shares in Millions, $ in Millions	3 Months Ended	12 Months Ended
	Sep. 30, 2017	Sep. 29, 2018	Sep. 24, 2016
Disclosure of Compensation Related Costs, Share-based Payments [Abstract]
Options granted (in shares)	1	1.7	1.1
Weighted-average exercise price	$ 38.07	$ 40.76	$ 39.32
Weighted average grant date fair value (in usd per share)	$ 12.33	$ 12.98	$ 12.91
Assumptions:
Risk-free interest rates	1.80%	2.10%	1.60%
Expected life (in years)	4 years 8 months 15 days	4 years 8 months 15 days	4 years 8 months 15 days
Expected volatility	36.60%	35.30%	37.80%
Dividend yield	$ 0	$ 0	$ 0

Stockholders' Equity and Stoc_6

Stockholders' Equity and Stock-Based Compensation - Stock Option Activity (Detail) - USD ($) $ / shares in Units, shares in Millions, $ in Millions	3 Months Ended	12 Months Ended
	Sep. 30, 2017	Sep. 29, 2018	Sep. 30, 2017	Sep. 24, 2016
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Granted		1.7
Number of Shares (in millions)
Options outstanding at September 30, 2017		5.5
Granted	1	1.7		1.1
Canceled/ forfeited		(0.4)
Exercised		(0.8)
Options outstanding at September 29, 2018	5.5	6	5.5
Options exercisable at September 29, 2018		2.8
Options vested and expected to vest at September 29, 2018 (1)		5.9
Weighted- Average Exercise Price
Options outstanding at September 30, 2017		$ 28.15
Granted	$ 38.07	40.76		$ 39.32
Canceled/ forfeited		36.22
Exercised		21.72
Options outstanding at September 29, 2018	$ 28.15	32.13	$ 28.15
Options exercisable at September 29, 2018		26.47
Options vested and expected to vest at September 29, 2018 (1)		$ 32.08
Weighted- Average Remaining Contractual Life (in Years)
Options outstanding at September 30, 2017	5 years 5 months 11 days	5 years 10 months 11 days
Options exercisable at September 29, 2018		3 years 8 months 12 days
Options vested and expected to vest at September 29, 2018 (1)		5 years 10 months 29 days
Options outstanding at September 29, 2018	5 years 5 months 11 days	5 years 10 months 11 days
Aggregate Intrinsic Value (in millions)
Options outstanding at September 30, 2017		$ 50.3
Exercised	$ 25.9	15.2		$ 21.6
Options outstanding at September 29, 2018	$ 50.3	53.3	$ 50.3
Options exercisable at September 29, 2018		40.8
Options vested and expected to vest at September 29, 2018 (1)		$ 52.8
Performance Shares
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Granted	0.2	0.6		0.3
Market Based Stock Units
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Granted		0.3	0.1

Stockholders' Equity and Stoc_7

Stockholders' Equity and Stock-Based Compensation - Restricted Stock Unit Activity (Detail) - USD ($) $ / shares in Units, shares in Millions, $ in Millions	3 Months Ended	12 Months Ended
	Sep. 30, 2017	Sep. 29, 2018	Sep. 24, 2016
Disclosure of Compensation Related Costs, Share-based Payments [Abstract]
Tax benefit related to stock based compensation	$ 22.6	$ 11.7	$ 23.1
Number of Shares (in millions)
Non-vested at September 30, 2017		3
Granted		1.7
Vested		(1.6)
Forfeited		(0.4)
Non-vested at September 29, 2018	3	2.7
Weighted-Average Grant-Date Fair Value
Non-vested at September 30, 2017		$ 34.58
Granted		42.49
Vested		34.10
Forfeited		38.28
Non-vested at September 29, 2018	$ 34.58	$ 40.02

Stockholders' Equity and Stoc_8

Stockholders' Equity and Stock-Based Compensation - Assumptions to Value Stock Options (Detail) - USD ($)	3 Months Ended	12 Months Ended
	Sep. 30, 2017	Sep. 29, 2018	Sep. 24, 2016
Assumptions:
Risk-free interest rates	1.80%	2.10%	1.60%
Expected life (in years)	4 years 8 months 15 days	4 years 8 months 15 days	4 years 8 months 15 days
Expected volatility	36.60%	35.30%	37.80%
Dividend yield	$ 0	$ 0	$ 0
ESPP
Assumptions:
Risk-free interest rates	0.72%	1.62%	0.34%
Expected life (in years)	6 months	6 months	6 months
Expected volatility	24.90%	25.00%	27.20%
Dividend yield	$ 0	$ 0	$ 0

Profit Sharing 401(k) Plan - Ad

Profit Sharing 401(k) Plan - Additional Information (Detail) - USD ($) $ in Millions	12 Months Ended
	Sep. 29, 2018	Sep. 30, 2017	Sep. 24, 2016
Defined Contribution Plan [Abstract]
Contributions made by company	$ 18.6	$ 20.2	$ 16.2

Deferred Compensation Plan - Ad

Deferred Compensation Plan - Additional Information (Detail) - USD ($) $ in Millions	12 Months Ended
	Sep. 29, 2018	Sep. 30, 2017	Sep. 24, 2016
Gen-Probe Incorporated [Member]
Deferred Compensation Arrangement with Individual, Postretirement Benefits [Line Items]
Compensation expense for the DCP discretionary contributions	$ 49.8	$ 43.2
Nonqualified Deferred Compensation Plan [Member]
Deferred Compensation Arrangement with Individual, Postretirement Benefits [Line Items]
Maximum employee contributions from base salary, percentage	75.00%
Maximum employee contributions from annual bonus, percentage	100.00%
Employee contributions vested, percentage	100.00%
Percent vested annually	33.33%
Contributions, vesting period, years	3 years
Compensation expense for the DCP discretionary contributions	$ 2.9	3.4	$ 3.1
Investment in group life insurance contracts	$ 44.2	$ 41
Nonqualified Deferred Compensation Plan [Member] | One Third Annually [Member]
Deferred Compensation Arrangement with Individual, Postretirement Benefits [Line Items]
Contributions, vesting period, years	3 years

Commitments and Contingencies -

Commitments and Contingencies - Additional Information (Detail) $ in Millions	3 Months Ended	12 Months Ended
	Sep. 30, 2017USD ($)	Sep. 29, 2018USD ($)Leaseterm	Sep. 24, 2016USD ($)
Contingent Consideration Earn-Out Payments [Line Items]
Accrued expenses	$ 375.3	$ 436.1
Operating lease expiration year		2,035
Rent expense net of sublease income	19.3	$ 23.1	$ 17.9
Rent expense on sublease rentals	$ 2.3	$ 2.6	$ 2.4
Finance Leases [Member]
Contingent Consideration Earn-Out Payments [Line Items]
Number of finance leases | Lease		2
Fair value		$ 28.3
Finance lease expiration year		2,024
Accrued expenses		$ 1.6
Accrued lease obligation-long-term		$ 34.7
Optional lease extension period		10 years
Number of optional lease extensions | term		2
Lease extension period		5 years
Finance Lease 2 [Member]
Contingent Consideration Earn-Out Payments [Line Items]
Optional lease extension period		6 years
Number of optional lease extensions | term		1
Lease extension period		5 years
Finance Leases [Member] | Leasehold Improvements [Member]
Contingent Consideration Earn-Out Payments [Line Items]
Property, plant and equipment, estimated useful life		35 years

Commitments and Contingencies_2

Commitments and Contingencies - Future Minimum Lease Payments, Including Principal and Interest (Details) - USD ($) $ in Millions	Sep. 29, 2018	Sep. 30, 2017
Other Commitments [Line Items]
Fiscal 2,019	$ 2.9
Fiscal 2,020	3
Fiscal 2,021	3
Fiscal 2,022	3.1
Fiscal 2,023	3.2
Thereafter	10.6
Total minimum payments	25.8
Less-amount representing interest	(14.4)
Present value of obligations under capital lease	11.4
Current portion of capital lease obligations	1.7	$ 1.6
Capital lease obligations, net of current portion	20.9	$ 22.7
Cynosure
Other Commitments [Line Items]
Fiscal 2,019	2.8
Fiscal 2,020	2.8
Fiscal 2,021	2.8
Fiscal 2,022	3
Fiscal 2,023	3
Thereafter	14.4
Total minimum payments	28.8
Less-amount representing interest	(6.2)
Present value of obligations under capital lease	$ 22.6

Commitments and Contingencies_3

Commitments and Contingencies - Summary of Purchase Commitments (Details) $ in Millions	Sep. 29, 2018USD ($)
Commitments and Contingencies Disclosure [Abstract]
Fiscal 2,019	$ 341.7
Fiscal 2,020	3.1
Fiscal 2,021	0.9
Total	$ 345.7

Commitments and Contingencies_4

Commitments and Contingencies - Future Minimum Lease Payments Under All Operating Leases (Details) $ in Millions	Sep. 29, 2018USD ($)
Commitments and Contingencies Disclosure [Abstract]
Fiscal 2,019	$ 21
Fiscal 2,020	16.9
Fiscal 2,021	13.9
Fiscal 2,022	11.2
Fiscal 2,023	6.7
Thereafter	17.9
Total	$ 87.6

Commitments and Contingencies_5

Commitments and Contingencies - Future Minimum Annual Rental Income Payments Under Sublease Agreements (Details) $ in Millions	Sep. 29, 2018USD ($)
Commitments and Contingencies Disclosure [Abstract]
Fiscal 2,019	$ 2.5
Fiscal 2,020	1.8
Fiscal 2,021	0.6
Fiscal 2,022	0.6
Fiscal 2,023	0.6
Thereafter	1.2
Total	$ 7.3

Litigation and Other Matters -

Litigation and Other Matters - Additional Information (Detail) - USD ($)	Oct. 26, 2018	Jul. 27, 2018	Oct. 07, 2016	Sep. 29, 2018	Apr. 01, 2017	Dec. 31, 2016	Sep. 04, 2012
Loss Contingencies [Line Items]
Assessed damages							$ 4,000,000
Plaintiff statutory damages offer, individual basis			$ 25
Litigation settlement amount					$ 8,500,000
Litigation settlement expense				$ 34,800,000		$ 9,200,000
Smith & Nephew vs. Interlace Medical, Inc. | Subsequent Event | Settled Litigation
Loss Contingencies [Line Items]
Paid damages	$ 34,800,000
Company Vs. Minerva Surgical, Inc. | Judicial Ruling
Loss Contingencies [Line Items]
Awarded damages		$ 4,800,000

Disposition - Additional Inform

Disposition - Additional Information (Details) - USD ($) $ in Millions	Dec. 14, 2016	Apr. 01, 2017	Sep. 29, 2018	Sep. 30, 2017	Sep. 24, 2016
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Proceeds from divestiture of businesses			$ 0	$ 1,865	$ 0
Blood Screening Business | Disposed of by Sale
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Sales price	$ 1,850
Proceeds from divestiture of businesses		$ 1,865
Gain on disposal		899.7
Tax obligation		649.5
Proceeds allocated to manufacture of inventory		$ 13.1
Disposal group, revenue			$ 55.4	$ 44
Minimum
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Transition services agreement term		2 years
Minimum | Blood Screening Business | Disposed of by Sale
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Transition services agreement term	2 years
Maximum
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Transition services agreement term		3 years
Maximum | Blood Screening Business | Disposed of by Sale
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Transition services agreement term	3 years

Disposition - Income from Opera

Disposition - Income from Operations (Details) - USD ($) $ in Millions	12 Months Ended
	Sep. 30, 2017	Sep. 24, 2016
Blood Screening Business | Disposed of by Sale
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Income from operations	$ 45.8	$ 99.1

Disposition - Prior Collaborati

Disposition - Prior Collaboration Agreement (Details) - USD ($) $ in Millions	1 Months Ended	12 Months Ended
	Jul. 31, 2009	Sep. 30, 2017	Sep. 24, 2016
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Collaboration agreements revenue		$ 96.5	$ 235.4
Grifols [Member] | Blood screening [Member] | Collaboration Agreement [Member]
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Manufacturing costs entitled to recover	50.00%
Share of Revenue from Any Assay	50.00%

Business Segments and Geograp_3

Business Segments and Geographic Information - Additional Information (Detail)	3 Months Ended								12 Months Ended
	Sep. 29, 2018USD ($)	Jun. 30, 2018USD ($)	Mar. 31, 2018USD ($)	Dec. 30, 2017USD ($)	Sep. 30, 2017USD ($)	Jul. 01, 2017USD ($)	Apr. 01, 2017USD ($)	Dec. 31, 2016USD ($)	Sep. 29, 2018USD ($)Segment	Sep. 30, 2017USD ($)	Sep. 24, 2016USD ($)
Segment Reporting Disclosure [Line Items]
Number of reportable segments | Segment									5
Revenues	$ 813,500,000	$ 824,000,000	$ 789,300,000	$ 791,100,000	$ 800,000	$ 800,000	$ 700,000	$ 700,000	$ 3,217,900,000	$ 3,058,800,000	$ 2,832,700,000
Intersegment
Segment Reporting Disclosure [Line Items]
Revenues					$ 0				$ 0		$ 0

Business Segments and Geograp_4

Business Segments and Geographic Information - Segment Information (Detail) - USD ($) $ in Millions	3 Months Ended								12 Months Ended
	Sep. 29, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 30, 2017	Sep. 30, 2017	Jul. 01, 2017	Apr. 01, 2017	Dec. 31, 2016	Sep. 29, 2018	Sep. 30, 2017	Sep. 24, 2016
Segment Reporting Information [Line Items]
Total revenue	$ 813.5	$ 824	$ 789.3	$ 791.1	$ 0.8	$ 0.8	$ 0.7	$ 0.7	$ 3,217.9	$ 3,058.8	$ 2,832.7
Operating income									(237.9)	1,370.2	548.6
Depreciation and amortization									480.3	449.2	465.4
Capital expenditures									105.6	107.6	94.5
Identifiable assets	7,230.9				7,979.6				7,230.9	7,979.6	7,317
Corporate
Segment Reporting Information [Line Items]
Capital expenditures									7.3	21	12.3
Identifiable assets	1,457.1				1,262.7				1,457.1	1,262.7	1,134.4
Diagnostics
Segment Reporting Information [Line Items]
Total revenue									1,147.4	1,197.1	1,236.9
Operating income									145.5	1,054.2	126
Depreciation and amortization									257.3	278.9	341.8
Capital expenditures									57.7	50.9	53.5
Identifiable assets	2,442.9				2,621.6				2,442.9	2,621.6	3,771.9
Breast Health
Segment Reporting Information [Line Items]
Total revenue									1,218.2	1,138.3	1,112.8
Operating income									399.7	373.4	350.5
Depreciation and amortization									22.7	19.7	22.6
Capital expenditures									14.8	12	10.6
Identifiable assets	972.4				824				972.4	824	809.1
Medical Aesthetics
Segment Reporting Information [Line Items]
Total revenue									339.1	207.5	0
Operating income									(844.7)	(115.9)	0
Depreciation and amortization									108.1	54.2	0
Capital expenditures									9.4	7.3	0
Identifiable assets	913.3				1,751.2				913.3	1,751.2	0
GYN Surgical
Segment Reporting Information [Line Items]
Total revenue									422	427.1	393.1
Operating income									58.3	65	69.1
Depreciation and amortization									91.6	95.7	99.9
Capital expenditures									13.1	15.2	17.7
Identifiable assets	1,414.9				1,494.6				1,414.9	1,494.6	1,570.7
Skeletal Health
Segment Reporting Information [Line Items]
Total revenue									91.2	88.8	89.9
Operating income									3.3	(6.5)	3
Depreciation and amortization									0.6	0.7	1.1
Capital expenditures									3.3	1.2	0.4
Identifiable assets	$ 30.3				$ 25.5				$ 30.3	$ 25.5	$ 30.9

Business Segments and Geograp_5

Business Segments and Geographic Information - Revenues by Geography (Detail)	12 Months Ended
	Sep. 29, 2018	Sep. 30, 2017	Sep. 24, 2016
Schedule Of Geographical Segments [Line Items]
Revenues	100.00%	100.00%	100.00%
United States
Schedule Of Geographical Segments [Line Items]
Revenues	75.10%	77.60%	78.90%
Europe
Schedule Of Geographical Segments [Line Items]
Revenues	11.70%	10.00%	10.20%
Asia-Pacific
Schedule Of Geographical Segments [Line Items]
Revenues	8.60%	8.10%	7.60%
Rest of world
Schedule Of Geographical Segments [Line Items]
Revenues	4.60%	4.30%	3.30%

Business Segments and Geograp_6

Business Segments and Geographic Information - Schedule of Geographically Located Property and Equipment, Net (Details) - USD ($) $ in Millions	Sep. 29, 2018	Sep. 30, 2017	Sep. 24, 2016
Geographic Information For Property Plant And Equipment [Line Items]
Property, plant and equipment, net	$ 478.2	$ 472.8	$ 451.9
United States
Geographic Information For Property Plant And Equipment [Line Items]
Property, plant and equipment, net	366.5	368.1	362.4
Costa Rica
Geographic Information For Property Plant And Equipment [Line Items]
Property, plant and equipment, net	30.9	30.1	28.1
Europe
Geographic Information For Property Plant And Equipment [Line Items]
Property, plant and equipment, net	62	57.1	49.2
Rest of world
Geographic Information For Property Plant And Equipment [Line Items]
Property, plant and equipment, net	$ 18.8	$ 17.5	$ 12.2

Accrued Expenses and Other Lo_3

Accrued Expenses and Other Long-Term Liabilities - Schedule of Accrued Expenses (Detail) - USD ($) $ in Millions	Sep. 29, 2018	Sep. 30, 2017
Accrued Expenses
Compensation and employee benefits	$ 196	$ 176.7
Income and other taxes	57.2	66.9
Other	182.9	131.7
Total	$ 436.1	$ 375.3

Accrued Expenses and Other Lo_4

Accrued Expenses and Other Long-Term Liabilities - Schedule of Other Long-Term Liabilities (Detail) - USD ($) $ in Millions	Sep. 29, 2018	Sep. 30, 2017
Other Long-Term Liabilities
Reserve for income tax uncertainties	$ 92.6	$ 88.3
Accrued lease obligation—long-term	35.5	34.1
Pension liabilities	9.9	10
Other	19.6	7.8
Total	$ 157.6	$ 140.2

Pension and Other Employee Be_3

Pension and Other Employee Benefits - Additional Information (Detail) - USD ($) $ in Millions	Sep. 29, 2018	Sep. 30, 2017
Other Liabilities Disclosure [Abstract]
Defined benefit pension plan, liabilities	$ (9.7)	$ (9.9)
Projected benefit obligations in excess of plan assets	(9.7)	(9.9)
Accumulated benefit obligation	(9.7)	(9.9)
Projected benefit obligation for long-term service awards	$ 0.1	$ 0.1

Pension and Other Employee Be_4

Pension and Other Employee Benefits - Schedule of Reconciliation of Benefit Obligations, Plan Assets Funded Status (Detail) - USD ($) $ in Millions	12 Months Ended
	Sep. 29, 2018	Sep. 30, 2017	Sep. 24, 2016
Other Liabilities Disclosure [Abstract]
Benefit obligation at beginning of year	$ (9.9)	$ (11)	$ (10)
Service cost	0	0	0
Interest cost	(0.2)	(0.1)	(0.2)
Plan participants’ contributions	0	0	0
Actuarial gain (loss)	(0.1)	1.5	(1.2)
Foreign exchange gain	0.2	(0.6)	0.1
Benefits paid	0.3	0.3	0.3
Benefit obligation at end of year	(9.7)	(9.9)	(11)
Plan assets	0	0	0
Benefit obligation at end of year	$ (9.7)	$ (9.9)	$ (11)

Pension and Other Employee Be_5

Pension and Other Employee Benefits - Components of Net Periodic Benefit Cost and Related Actuarial Assumptions (Detail) - USD ($) $ in Millions	12 Months Ended
	Sep. 29, 2018	Sep. 30, 2017	Sep. 24, 2016
Other Liabilities Disclosure [Abstract]
Service cost	$ 0	$ 0	$ 0
Interest cost	0.2	0.1	0.4
Expected return on plan assets	0	0	0
Amortization of prior service cost		0	0
Recognized net actuarial gain	0.1	0.4	(0.2)
Net periodic benefit cost	$ 0.3	$ 0.5	$ 0.2

Pension and Other Employee Be_6

Pension and Other Employee Benefits - Schedule of Weighted-Average Net Periodic Benefit Cost Assumptions (Detail)	12 Months Ended
	Sep. 29, 2018	Sep. 30, 2017	Sep. 24, 2016
Defined Benefit Plan, Assumptions Used in Calculations [Abstract]
Discount rate	1.95%	2.15%	1.30%
Expected return on plan assets	0.00%	0.00%	0.00%
Rate of compensation increase	0.00%	0.00%	0.00%

Pension and Other Employee Be_7

Pension and Other Employee Benefits - Schedule of Expected Pension Benefit (Detail) $ in Millions	Sep. 29, 2018USD ($)
Defined Benefit Plan, Expected Future Benefit Payment [Abstract]
2,017	$ 0.4
2,018	0.4
2,019	0.4
2,020	0.4
2,021	0.4
2023 to 2027	$ 2.1

Quarterly Statement of Operat_3

Quarterly Statement of Operations Information (Unaudited) - (Detail) - USD ($) $ / shares in Units, $ in Millions	3 Months Ended								12 Months Ended
	Sep. 29, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 30, 2017	Sep. 30, 2017	Jul. 01, 2017	Apr. 01, 2017	Dec. 31, 2016	Sep. 29, 2018	Sep. 30, 2017	Sep. 24, 2016
Quarterly Financial Information Disclosure [Abstract]
(Benefit) provision for income taxes				$ 329.2					$ (307.3)	$ 475	$ 84.5
Litigation settlement expense	$ 34.8							$ 9.2
Goodwill impairment charge			$ 685.7						685.7	0	0
Impairment of Intangible Assets, Indefinite-lived (Excluding Goodwill)			46						46	0	0
Gain (Loss) on Disposition of Business							$ 899.7		0	899.7	0
Total revenue	813.5	$ 824	789.3	791.1	$ 0.8	$ 0.8	0.7	0.7	3,217.9	3,058.8	2,832.7
Gross profit	421.1	436	415.1	424.5	0.4	0.4	0.4	0.4	1,696.7	1,621	1,563.3
Net (loss) income	$ 50.5	$ 112.9	$ (681.4)	$ 406.7	$ 0.1	$ 0.1	$ 0.5	$ 0.1	$ (111.3)	$ 755.5	$ 330.8
Diluted net income per common share (in dollars per share)	$ 0.18	$ 0.41	$ (2.46)	$ 1.45	$ 0.29	$ 0.21	$ 1.84	$ 0.30	$ (0.40)	$ 2.64	$ 1.16
Acquisition charges							$ 19.4

Quarterly Statement of Operat_4

Quarterly Statement of Operations Information (Unaudited) - (Narrative) (Detail) - USD ($) $ in Millions	3 Months Ended			12 Months Ended
	Mar. 31, 2018	Jul. 01, 2017	Apr. 01, 2017	Sep. 29, 2018	Sep. 30, 2017	Sep. 24, 2016
Quarterly Financial Information Disclosure [Abstract]
Restructuring charges				$ 14.2	$ 13.3	$ 10.5
Acquisition charges			$ 19.4
Gain on sale of investments				0	5.6	25.1
Debt extinguishment loss	$ 44.9	$ 2.6		$ 45.9	$ 3.2	$ 5.3