Fair Value Measurements (Tables)

3 Months Ended

12 Months Ended

Dec. 29, 2019

Sep. 29, 2019

Fair Value Disclosures [Abstract]

Assets And Liabilities Measured At Fair Value On A Recurring Basis

			Fair Value Measurements at Reporting Date Using
	Balance at December 29,2019		Quoted Prices in Active Markets for  Identical Assets (Level 1)		Significant  Other Observable  Inputs (Level 2)		Significant Unobservable  Inputs (Level 3)
Assets:
Cash and cash equivalents	$	3,040.5	$	3,040.5	$	—	$	—
Short-term investments:
Available-for-sale debt securities
Commercial paper	0.5		—		0.5		—
Corporate debt securities	3.5		—		3.5		—
Total available-for-sale debt securities	4.0		—		4.0		—
Marketable equity securities	64.4		64.4		—		—
Total short-term investments	68.4		64.4		4.0		—
Prepaid expenses and other current assets:
Derivative assets	23.2		9.8		13.4		—
Long-term investments:
Available-for-sale debt securities
Corporate debt securities	91.1		—		91.1		—
Auction rate securities	5.8		—		—		5.8
U.S. government treasury securities	98.6		98.6		—		—
State and local government obligations	3.6		—		3.6		—
Mortgage and other asset-backed securities	0.7		—		0.7		—
Total long-term investments	199.8		98.6		95.4		5.8
Other long-term assets:
Derivative assets	42.6		0.1		42.5		—
Total assets	$	3,374.5	$	3,213.4	$	155.3	$	5.8
Liabilities:
Accrued liabilities:
Derivative liabilities	$	3.4	$	—	$	3.4	$	—
Other long-term liabilities:
Derivative liabilities	8.5		—		8.5		—
Total liabilities	$	11.9	$	—	$	11.9	$	—

			Fair Value Measurements at Reporting Date Using
	Balance at September 29, 2019		Quoted Prices in Active Markets for  Identical Assets (Level 1)		Significant  Other Observable  Inputs (Level 2)		Significant Unobservable  Inputs (Level 3)
Assets:
Cash and cash equivalents	$	2,686.6	$	2,686.6	$	—	$	—
Short-term investments:
Available-for-sale debt securities
Commercial paper	0.5		—		0.5		—
Corporate debt securities	3.5		—		3.5		—
Total available-for-sale debt securities	4.0		—		4.0		—
Marketable equity securities	66.5		66.5		—		—
Total short-term investments	70.5		66.5		4.0		—
Prepaid expenses and other current assets:
Derivative assets	12.6		—		12.6		—
Long-term investments:
Available-for-sale debt securities
Corporate debt securities	101.2		—		101.2		—
Auction rate securities	5.8		—		—		5.8
U.S. government treasury securities	106.5		106.5		—		—
State and local government obligations	4.9		—		4.9		—
Mortgage and other asset-backed	1.6		—		1.6		—
Total long-term investments	220.0		106.5		107.7		5.8
Other long-term assets:
Derivative assets	26.3		—		26.3		—
Total assets	$	3,016.0	$	2,859.6	$	150.6	$	5.8
Liabilities:
Accrued liabilities:
Derivative liabilities	$	5.7	$	1.1	$	4.6	$	—
Other long-term liabilities:
Derivative liabilities	12.5		—		12.5		—
Total liabilities	$	18.2	$	1.1	$	17.1	$	—