Fair Value (Tables)

6 Months Ended

Mar. 29, 2019

Fair Value Disclosures [Abstract]

Schedule of Fair Value Assets and Liabilities Measured on Recurring Basis

Assets and liabilities recorded at fair value on a recurring basis consisted of the following (in millions):         

	As of March 29, 2019								As of September 28, 2018
			Fair Value Measurements								Fair Value Measurements
	Total		Level 1		Level 2		Level 3		Total		Level 1		Level 2		Level 3
Assets
Cash and cash equivalents*	$	816.3	$	707.8	$	108.5	$	—	$	733.3	$	683.7	$	49.6	$	—
U.S. Treasury and government securities	32.4		10.5		21.9		—		65.0		15.0		50.0		—
Corporate bonds and notes	65.6		—		65.6		—		216.0		—		216		—
Municipal bonds	73.8		—		73.8		—		2.8		—		2.8		—
Other government securities	3.2		—		3.2		—		33.1		—		33.1		—
Total	$	991.3	$	718.3	$	273.0	$	—	$	1,050.2	$	698.7	$	351.5	$	—
Liabilities
Contingent consideration	$	3.1	$	—	$	—	$	3.1	$	3.1	$	—	$	—	$	3.1
Total	$	3.1	$	—	$	—	$	3.1	$	3.1	$	—	$	—	$	3.1

Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation