CONDENSED CONSOLIDATED STATEMENTS OF CASH FLOWS - USD ($) $ in Millions	6 Months Ended
	Mar. 29, 2019	Mar. 30, 2018
Statement of Cash Flows [Abstract]
Net earnings (loss)	$ 192.3	$ (39.0)
Adjustments to reconcile net earnings (loss) to net cash provided by operating activities:
Share-based compensation expense	23.0	21.2
Depreciation	25.8	25.4
Amortization of intangible assets	11.4	10.4
Gain on sale of equity investments, net	(21.8)	0.0
Deferred taxes	7.4	41.8
Impairment charges	0.0	11.1
Loss on hedges related to acquisition-related activities	0.0	16.4
Loss on equity investments	2.2	0.9
Provision for doubtful accounts receivable	4.0	2.0
Other, net	(1.9)	(0.9)
Changes in assets and liabilities, net of effects of acquisitions:
Trade and unbilled receivables	(58.6)	28.4
Inventories	(41.9)	(10.9)
Prepaid expenses and other assets	(19.3)	0.0
Accounts payable	23.7	0.9
Accrued liabilities and other long-term liabilities	(74.2)	125.3
Deferred revenues	55.4	11.5
Net cash provided by operating activities	127.5	244.5
Cash flows from investing activities:
Purchases of property, plant and equipment	(25.2)	(17.8)
Acquisitions, net of cash acquired	(25.0)	(29.6)
Purchase of equity investments	(11.8)	(3.1)
Sale of equity investment	29.9	0.0
Principal payments on notes receivable	0.1	5.2
Investment in available-for-sale security	0.0	(6.0)
Sale of available-for-sale security	0.0	8.0
Loans to CPTC	(1.1)	(5.3)
Purchase of foreign currency option related to acquisition-related activities	0.0	(5.5)
Amounts paid to deferred compensation plan trust account	(2.5)	(1.3)
Other, net	1.0	0.4
Net cash used in investing activities	(34.6)	(55.0)
Cash flows from financing activities:
Repurchases of common stock	(85.6)	(92.7)
Proceeds from issuance of common stock to employees	38.6	44.6
Tax withholdings on vesting of equity awards	(13.9)	(11.1)
Cash received from Varex Imaging Corporation	4.1	0.0
Borrowings under credit facility agreement	0.0	234.3
Repayments under credit facility agreement	0.0	(209.3)
Net repayments under the credit facility agreements with maturities less than 90 days	0.0	(120.0)
Other	(0.1)	0.0
Net cash used in financing activities	(56.9)	(154.2)
Effects of exchange rate changes on cash, cash equivalents, and restricted cash	6.5	(11.5)
Net increase in cash, cash equivalents, and restricted cash	42.5	23.8
Cash, cash equivalents, and restricted cash at beginning of period	516.4	718.5
Cash, cash equivalents, and restricted cash at end of period	$ 558.9	$ 742.3