Fair Value Measurements (Assets And Liabilities Measured At Fair Value On A Recurring Basis) (Details) - USD ($) $ in Millions	Jun. 27, 2021	Sep. 27, 2020
Assets:
Total short-term investments	$ 153.6	$ 281.2
Total Assets	5,353.0	4,941.1
Liabilities:
Total liabilities	34.1	86.6
Cash and cash equivalents
Assets:
Cash and cash equivalents	4,753.1	4,350.9
Short-term Investments [Member]
Assets:
Available-for-sale debt securities	79.1	216.3
Marketable equity securities	74.5	64.9
Total short-term investments	153.6	281.2
Prepaid Expenses and Other Current Assets [Member]
Assets:
Derivative assets, Current	76.8	15.6
Long-term Investments [Member]
Assets:
Available-for-sale debt securities	285.9	206.1
Other Long-Term Assets [Member]
Assets:
Derivative assets, Noncurrent	83.6	87.3
Accrued Liabilities [Member]
Liabilities:
Derivative liabilities, Current	17.6	7.3
Other Long-Term Liabilities [Member]
Liabilities:
Derivative liabilities, Noncurrent	16.5	79.3
Auction rate securities | Long-term Investments [Member]
Assets:
Available-for-sale debt securities	5.8	5.7
Certificates of deposit | Short-term Investments [Member]
Assets:
Available-for-sale debt securities		1.6
Commercial paper | Short-term Investments [Member]
Assets:
Available-for-sale debt securities	57.0	66.8
Corporate debt securities | Short-term Investments [Member]
Assets:
Available-for-sale debt securities	22.1	123.6
Corporate debt securities | Long-term Investments [Member]
Assets:
Available-for-sale debt securities	164.0	82.6
Foreign government obligations | Long-term Investments [Member]
Assets:
Available-for-sale debt securities	4.0
Foreign Government Short-term Debt Securities | Short-term Investments [Member]
Assets:
Available-for-sale debt securities		8.5
Mortgage and other asset-backed securities | Short-term Investments [Member]
Assets:
Available-for-sale debt securities		15.8
Mortgage and other asset-backed securities | Long-term Investments [Member]
Assets:
Available-for-sale debt securities	25.1	19.3
State and local government obligations | Long-term Investments [Member]
Assets:
Available-for-sale debt securities	1.5	3.6
U.S. government treasury securities | Long-term Investments [Member]
Assets:
Available-for-sale debt securities	85.5	94.9
Fair Value, Inputs, Level 1 [Member]
Assets:
Total Assets	4,976.3	4,514.3
Liabilities:
Total liabilities	1.1	2.0
Fair Value, Inputs, Level 1 [Member] | Cash and cash equivalents
Assets:
Cash and cash equivalents	4,753.1	4,350.9
Fair Value, Inputs, Level 1 [Member] | Short-term Investments [Member]
Assets:
Available-for-sale debt securities	0.0	0.0
Marketable equity securities	74.5	64.9
Total short-term investments	74.5	64.9
Fair Value, Inputs, Level 1 [Member] | Prepaid Expenses and Other Current Assets [Member]
Assets:
Derivative assets, Current	63.2	3.6
Fair Value, Inputs, Level 1 [Member] | Long-term Investments [Member]
Assets:
Available-for-sale debt securities	85.5	94.9
Fair Value, Inputs, Level 1 [Member] | Other Long-Term Assets [Member]
Assets:
Derivative assets, Noncurrent	0.0	0.0
Fair Value, Inputs, Level 1 [Member] | Accrued Liabilities [Member]
Liabilities:
Derivative liabilities, Current	1.1	1.9
Fair Value, Inputs, Level 1 [Member] | Other Long-Term Liabilities [Member]
Liabilities:
Derivative liabilities, Noncurrent	0.0	0.1
Fair Value, Inputs, Level 1 [Member] | Auction rate securities | Long-term Investments [Member]
Assets:
Available-for-sale debt securities	0.0	0.0
Fair Value, Inputs, Level 1 [Member] | Certificates of deposit | Short-term Investments [Member]
Assets:
Available-for-sale debt securities		0.0
Fair Value, Inputs, Level 1 [Member] | Commercial paper | Short-term Investments [Member]
Assets:
Available-for-sale debt securities	0.0	0.0
Fair Value, Inputs, Level 1 [Member] | Corporate debt securities | Short-term Investments [Member]
Assets:
Available-for-sale debt securities	0.0	0.0
Fair Value, Inputs, Level 1 [Member] | Corporate debt securities | Long-term Investments [Member]
Assets:
Available-for-sale debt securities	0.0	0.0
Fair Value, Inputs, Level 1 [Member] | Foreign government obligations | Long-term Investments [Member]
Assets:
Available-for-sale debt securities	0.0
Fair Value, Inputs, Level 1 [Member] | Foreign Government Short-term Debt Securities | Short-term Investments [Member]
Assets:
Available-for-sale debt securities		0.0
Fair Value, Inputs, Level 1 [Member] | Mortgage and other asset-backed securities | Short-term Investments [Member]
Assets:
Available-for-sale debt securities		0.0
Fair Value, Inputs, Level 1 [Member] | Mortgage and other asset-backed securities | Long-term Investments [Member]
Assets:
Available-for-sale debt securities	0.0	0.0
Fair Value, Inputs, Level 1 [Member] | State and local government obligations | Long-term Investments [Member]
Assets:
Available-for-sale debt securities	0.0	0.0
Fair Value, Inputs, Level 1 [Member] | U.S. government treasury securities | Long-term Investments [Member]
Assets:
Available-for-sale debt securities	85.5	94.9
Fair Value, Inputs, Level 2 [Member]
Assets:
Total Assets	370.9	421.1
Liabilities:
Total liabilities	33.0	84.6
Fair Value, Inputs, Level 2 [Member] | Cash and cash equivalents
Assets:
Cash and cash equivalents	0.0	0.0
Fair Value, Inputs, Level 2 [Member] | Short-term Investments [Member]
Assets:
Available-for-sale debt securities	79.1	216.3
Marketable equity securities	0.0	0.0
Total short-term investments	79.1	216.3
Fair Value, Inputs, Level 2 [Member] | Prepaid Expenses and Other Current Assets [Member]
Assets:
Derivative assets, Current	13.6	12.0
Fair Value, Inputs, Level 2 [Member] | Long-term Investments [Member]
Assets:
Available-for-sale debt securities	194.6	105.5
Fair Value, Inputs, Level 2 [Member] | Other Long-Term Assets [Member]
Assets:
Derivative assets, Noncurrent	83.6	87.3
Fair Value, Inputs, Level 2 [Member] | Accrued Liabilities [Member]
Liabilities:
Derivative liabilities, Current	16.5	5.4
Fair Value, Inputs, Level 2 [Member] | Other Long-Term Liabilities [Member]
Liabilities:
Derivative liabilities, Noncurrent	16.5	79.2
Fair Value, Inputs, Level 2 [Member] | Auction rate securities | Long-term Investments [Member]
Assets:
Available-for-sale debt securities	0.0	0.0
Fair Value, Inputs, Level 2 [Member] | Certificates of deposit | Short-term Investments [Member]
Assets:
Available-for-sale debt securities		1.6
Fair Value, Inputs, Level 2 [Member] | Commercial paper | Short-term Investments [Member]
Assets:
Available-for-sale debt securities	57.0	66.8
Fair Value, Inputs, Level 2 [Member] | Corporate debt securities | Short-term Investments [Member]
Assets:
Available-for-sale debt securities	22.1	123.6
Fair Value, Inputs, Level 2 [Member] | Corporate debt securities | Long-term Investments [Member]
Assets:
Available-for-sale debt securities	164.0	82.6
Fair Value, Inputs, Level 2 [Member] | Foreign government obligations | Long-term Investments [Member]
Assets:
Available-for-sale debt securities	4.0
Fair Value, Inputs, Level 2 [Member] | Foreign Government Short-term Debt Securities | Short-term Investments [Member]
Assets:
Available-for-sale debt securities		8.5
Fair Value, Inputs, Level 2 [Member] | Mortgage and other asset-backed securities | Short-term Investments [Member]
Assets:
Available-for-sale debt securities		15.8
Fair Value, Inputs, Level 2 [Member] | Mortgage and other asset-backed securities | Long-term Investments [Member]
Assets:
Available-for-sale debt securities	25.1	19.3
Fair Value, Inputs, Level 2 [Member] | State and local government obligations | Long-term Investments [Member]
Assets:
Available-for-sale debt securities	1.5	3.6
Fair Value, Inputs, Level 2 [Member] | U.S. government treasury securities | Long-term Investments [Member]
Assets:
Available-for-sale debt securities	0.0	0.0
Fair Value, Inputs, Level 3 [Member]
Assets:
Total Assets	5.8	5.7
Liabilities:
Total liabilities	0.0	0.0
Fair Value, Inputs, Level 3 [Member] | Cash and cash equivalents
Assets:
Cash and cash equivalents	0.0	0.0
Fair Value, Inputs, Level 3 [Member] | Short-term Investments [Member]
Assets:
Available-for-sale debt securities	0.0	0.0
Marketable equity securities	0.0	0.0
Total short-term investments	0.0	0.0
Fair Value, Inputs, Level 3 [Member] | Prepaid Expenses and Other Current Assets [Member]
Assets:
Derivative assets, Current	0.0	0.0
Fair Value, Inputs, Level 3 [Member] | Long-term Investments [Member]
Assets:
Available-for-sale debt securities	5.8	5.7
Fair Value, Inputs, Level 3 [Member] | Other Long-Term Assets [Member]
Assets:
Derivative assets, Noncurrent	0.0	0.0
Fair Value, Inputs, Level 3 [Member] | Accrued Liabilities [Member]
Liabilities:
Derivative liabilities, Current	0.0	0.0
Fair Value, Inputs, Level 3 [Member] | Other Long-Term Liabilities [Member]
Liabilities:
Derivative liabilities, Noncurrent	0.0	0.0
Fair Value, Inputs, Level 3 [Member] | Auction rate securities | Long-term Investments [Member]
Assets:
Available-for-sale debt securities	5.8	5.7
Fair Value, Inputs, Level 3 [Member] | Certificates of deposit | Short-term Investments [Member]
Assets:
Available-for-sale debt securities		0.0
Fair Value, Inputs, Level 3 [Member] | Commercial paper | Short-term Investments [Member]
Assets:
Available-for-sale debt securities	0.0	0.0
Fair Value, Inputs, Level 3 [Member] | Corporate debt securities | Short-term Investments [Member]
Assets:
Available-for-sale debt securities	0.0	0.0
Fair Value, Inputs, Level 3 [Member] | Corporate debt securities | Long-term Investments [Member]
Assets:
Available-for-sale debt securities	0.0	0.0
Fair Value, Inputs, Level 3 [Member] | Foreign government obligations | Long-term Investments [Member]
Assets:
Available-for-sale debt securities	0.0
Fair Value, Inputs, Level 3 [Member] | Foreign Government Short-term Debt Securities | Short-term Investments [Member]
Assets:
Available-for-sale debt securities		0.0
Fair Value, Inputs, Level 3 [Member] | Mortgage and other asset-backed securities | Short-term Investments [Member]
Assets:
Available-for-sale debt securities		0.0
Fair Value, Inputs, Level 3 [Member] | Mortgage and other asset-backed securities | Long-term Investments [Member]
Assets:
Available-for-sale debt securities	0.0	0.0
Fair Value, Inputs, Level 3 [Member] | State and local government obligations | Long-term Investments [Member]
Assets:
Available-for-sale debt securities	0.0	0.0
Fair Value, Inputs, Level 3 [Member] | U.S. government treasury securities | Long-term Investments [Member]
Assets:
Available-for-sale debt securities	$ 0.0	$ 0.0