Fair Value Measurements (Tables)

3 Months Ended

12 Months Ended

Dec. 27, 2020

Sep. 27, 2020

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 27, 2020		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	$	5,028.1	$	5,028.1	$	—	$	—
Short-term investments:
Available-for-sale debt securities
Certificates of deposit	1.6		—		1.6		—
Commercial paper	71.8		—		71.8		—
Corporate debt securities	78.5		—		78.5		—
Mortgage and other asset-backed securities	16.7		—		16.7		—
State and local government obligations	1.0		—		1.0		—
Total available-for-sale debt securities	169.6		—		169.6		—
Marketable equity securities	65.9		65.9		—		—
Total short-term investments	235.5		65.9		169.6		—
Prepaid expenses and other current assets:
Derivative assets	24.7		14.6		10.1		—
Long-term investments:
Available-for-sale debt securities
Auction rate securities	5.7		—		—		5.7
Corporate debt securities	82.6		—		82.6		—
Mortgage and other asset-backed securities	9.8		—		9.8		—
State and local government obligations	2.6		—		2.6		—
U.S. government treasury securities	90.2		90.2		—		—
Total long-term investments	190.9		90.2		95.0		5.7
Other long-term assets:
Derivative assets	53.5		—		53.5		—
Total assets	$	5,532.7	$	5,198.8	$	328.2	$	5.7
Liabilities:
Accrued liabilities:
Derivative liabilities	$	13.2	$	0.8	$	12.4	$	—
Other long-term liabilities:
Derivative liabilities	67.4		—		67.4		—
Total liabilities	$	80.6	$	0.8	$	79.8	$	—

			Fair Value Measurements at Reporting Date Using
	Balance at September 27, 2020		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	$	4,350.9	$	4,350.9	$	—	$	—
Short-term investments:
Available-for-sale debt securities
Certificates of deposit	1.6		—		1.6		—
Commercial paper	66.8		—		66.8		—
Corporate debt securities	123.6		—		123.6		—
Foreign government obligations	8.5		—		8.5		—
Mortgage and other asset-backed securities	15.8		—		15.8		—
Total available-for-sale debt securities	216.3		—		216.3		—
Marketable equity securities	64.9		64.9		—		—
Total short-term investments	281.2		64.9		216.3		—
Prepaid expenses and other current assets:
Derivative assets	15.6		3.6		12.0		—
Long-term investments:
Available-for-sale debt securities
Auction rate securities	5.7		—		—		5.7
Corporate debt securities	82.6		—		82.6		—
Mortgage and other asset-backed securities	19.3		—		19.3		—
State and local government obligations	3.6		—		3.6		—
U.S. government treasury securities	94.9		94.9		—		—
Total long-term investments	206.1		94.9		105.5		5.7
Other long-term assets:
Derivative assets	87.3		—		87.3		—
Total assets	$	4,941.1	$	4,514.3	$	421.1	$	5.7
Liabilities:
Accrued liabilities:
Derivative liabilities	$	7.3	$	1.9	$	5.4	$	—
Other long-term liabilities:
Derivative liabilities	79.3		0.1		79.2		—
Total liabilities	$	86.6	$	2.0	$	84.6	$	—