CONDENSED CONSOLIDATED STATEMENTS OF CASH FLOWS - USD ($) $ in Millions		3 Months Ended
		Dec. 29, 2017	Dec. 30, 2016
Statement of Cash Flows [Abstract]
Net earnings (loss)		$ (112.2)	$ 14.5
Adjustments to reconcile net earnings to net cash provided by operating activities:
Share-based compensation expense		10.7	11.5
Depreciation		12.8	17.2
Amortization of intangible assets		6.3	5.1
Deferred taxes		44.9	(20.9)
Provision for doubtful accounts receivable		1.5	38.1
Impairment charges		0.0	38.3
Other, net		(0.8)	(0.6)
Changes in assets and liabilities:
Trade and unbilled receivables		65.9	32.4
Inventories		(11.7)	(30.1)
Prepaid expenses and other assets		28.2	(10.1)
Accounts payable		(10.3)	(20.7)
Accrued liabilities and other long-term liabilities		125.1	(20.3)
Deferred revenues		18.6	27.8
Net cash provided by operating activities		179.0	82.2
Cash flows from investing activities:
Purchases of property, plant and equipment		(9.3)	(17.2)
Issuance of notes receivable		0.0	(11.4)
Investment in available-for-sale securities		(6.0)	(0.6)
Loans to CPTC		(4.6)	0.0
Escrow deposit		(2.6)	0.0
Investment in privately-held company		(2.5)	0.0
Amounts paid to deferred compensation plan trust account		(1.3)	(3.4)
Principal payments on notes receivable		0.5	0.0
Other, net		0.0	0.8
Net cash used in investing activities		(25.8)	(31.8)
Cash flows from financing activities:
Repurchases of common stock		(56.7)	(49.5)
Proceeds from issuance of common stock to employees		24.2	16.1
Employees' taxes withheld and paid for restricted stock and restricted stock units		(0.3)	(1.2)
Borrowings under credit facility agreement		166.4	10.0
Repayments under credit facility agreement		(166.4)	(10.0)
Net (repayments) borrowings under the credit facility agreements with maturities less than 90 days		(10.0)	(55.0)
Net cash used in financing activities		(42.8)	(89.6)
Effects of exchange rate changes on cash and cash equivalents		(4.0)	10.4
Net increase (decrease) in cash and cash equivalents		106.4	(28.8)
Cash and cash equivalents at beginning of period	[1]	716.2	843.5
Cash and cash equivalents at end of period	[1]	$ 822.6	814.7
Cash and cash equivalents classified as discontinued operations			$ 32.7

[1] Cash and cash equivalents includes $32.7 million at December 30, 2016 classified as discontinued operations. See Note 2, "Discontinued Operations" for more information.