Fair Value Measurements (Assets and Liabilities Measured at Fair Value on a Recurring Basis) (Details) - USD ($) $ in Millions	Sep. 27, 2015	Sep. 28, 2014
Assets [Abstract]
Total short-term investments	$ 81.3	$ 135.4
Long-term investments: Available-for-sale securities	312.5	318.4
Total assets	2,029.4	2,208.9
Liabilities [Abstract]
Total liabilities	33.7
Cash and cash equivalents [Member]
Assets [Abstract]
Cash and cash equivalents	1,530.1	1,708.4
Short-term investments [Member]
Assets [Abstract]
Short-term investments: Available-for-sale securities	15.5	63.2
Short-term investments: Trading securities	65.8	72.2
Total short-term investments	81.3	135.4
Prepaid expenses and other current assets [Member]
Assets [Abstract]
Prepaid expenses and other current assets: Derivative assets	50.8	28.7
Long-term investments [Member]
Assets [Abstract]
Long-term investments: Available-for-sale securities	312.5	318.4
Other long-term assets [Member]
Assets [Abstract]
Other long-term assets: Derivative assets	54.7	18.0
Accrued liabilities [Member]
Liabilities [Abstract]
Accrued liabilities: Derivative liabilities	19.2	2.4
Other long-term liabilities [Member]
Liabilities [Abstract]
Other long-term liabilities: Derivative liabilities	14.5
Quoted Prices In Active Markets for Identical Assets (Level 1) [Member]
Assets [Abstract]
Total assets	1,700.7	1,887.2
Liabilities [Abstract]
Total liabilities	3.6
Quoted Prices In Active Markets for Identical Assets (Level 1) [Member] | Cash and cash equivalents [Member]
Assets [Abstract]
Cash and cash equivalents	1,530.1	1,708.4
Quoted Prices In Active Markets for Identical Assets (Level 1) [Member] | Short-term investments [Member]
Assets [Abstract]
Short-term investments: Available-for-sale securities	0.0	10.9
Short-term investments: Trading securities	65.8	72.2
Total short-term investments	65.8	83.1
Quoted Prices In Active Markets for Identical Assets (Level 1) [Member] | Prepaid expenses and other current assets [Member]
Assets [Abstract]
Prepaid expenses and other current assets: Derivative assets	0.0	0.9
Quoted Prices In Active Markets for Identical Assets (Level 1) [Member] | Long-term investments [Member]
Assets [Abstract]
Long-term investments: Available-for-sale securities	104.8	94.8
Quoted Prices In Active Markets for Identical Assets (Level 1) [Member] | Other long-term assets [Member]
Assets [Abstract]
Other long-term assets: Derivative assets	0.0	0.0
Quoted Prices In Active Markets for Identical Assets (Level 1) [Member] | Accrued liabilities [Member]
Liabilities [Abstract]
Accrued liabilities: Derivative liabilities	3.6	0.4
Quoted Prices In Active Markets for Identical Assets (Level 1) [Member] | Other long-term liabilities [Member]
Liabilities [Abstract]
Other long-term liabilities: Derivative liabilities	0.0
Significant Other Observable Inputs (Level 2) [Member]
Assets [Abstract]
Total assets	322.8	307.9
Liabilities [Abstract]
Total liabilities	30.1
Significant Other Observable Inputs (Level 2) [Member] | Cash and cash equivalents [Member]
Assets [Abstract]
Cash and cash equivalents	0.0	0.0
Significant Other Observable Inputs (Level 2) [Member] | Short-term investments [Member]
Assets [Abstract]
Short-term investments: Available-for-sale securities	15.5	52.3
Short-term investments: Trading securities	0.0	0.0
Total short-term investments	15.5	52.3
Significant Other Observable Inputs (Level 2) [Member] | Prepaid expenses and other current assets [Member]
Assets [Abstract]
Prepaid expenses and other current assets: Derivative assets	50.8	27.8
Significant Other Observable Inputs (Level 2) [Member] | Long-term investments [Member]
Assets [Abstract]
Long-term investments: Available-for-sale securities	201.8	209.8
Significant Other Observable Inputs (Level 2) [Member] | Other long-term assets [Member]
Assets [Abstract]
Other long-term assets: Derivative assets	54.7	18.0
Significant Other Observable Inputs (Level 2) [Member] | Accrued liabilities [Member]
Liabilities [Abstract]
Accrued liabilities: Derivative liabilities	15.6	2.0
Significant Other Observable Inputs (Level 2) [Member] | Other long-term liabilities [Member]
Liabilities [Abstract]
Other long-term liabilities: Derivative liabilities	14.5
Significant Unobservable Inputs (Level 3) [Member]
Assets [Abstract]
Total assets	5.9	13.8
Liabilities [Abstract]
Total liabilities	0.0
Significant Unobservable Inputs (Level 3) [Member] | Cash and cash equivalents [Member]
Assets [Abstract]
Cash and cash equivalents	0.0	0.0
Significant Unobservable Inputs (Level 3) [Member] | Short-term investments [Member]
Assets [Abstract]
Short-term investments: Available-for-sale securities	0.0	0.0
Short-term investments: Trading securities	0.0	0.0
Total short-term investments	0.0	0.0
Significant Unobservable Inputs (Level 3) [Member] | Prepaid expenses and other current assets [Member]
Assets [Abstract]
Prepaid expenses and other current assets: Derivative assets	0.0	0.0
Significant Unobservable Inputs (Level 3) [Member] | Long-term investments [Member]
Assets [Abstract]
Long-term investments: Available-for-sale securities	5.9	13.8
Significant Unobservable Inputs (Level 3) [Member] | Other long-term assets [Member]
Assets [Abstract]
Other long-term assets: Derivative assets	0.0	0.0
Significant Unobservable Inputs (Level 3) [Member] | Accrued liabilities [Member]
Liabilities [Abstract]
Accrued liabilities: Derivative liabilities	0.0	0.0
Significant Unobservable Inputs (Level 3) [Member] | Other long-term liabilities [Member]
Liabilities [Abstract]
Other long-term liabilities: Derivative liabilities	0.0
Agency obligations [Member] | Long-term investments [Member]
Assets [Abstract]
Long-term investments: Available-for-sale securities	8.6	8.9
Agency obligations [Member] | Quoted Prices In Active Markets for Identical Assets (Level 1) [Member] | Long-term investments [Member]
Assets [Abstract]
Long-term investments: Available-for-sale securities	0.0	0.0
Agency obligations [Member] | Significant Other Observable Inputs (Level 2) [Member] | Long-term investments [Member]
Assets [Abstract]
Long-term investments: Available-for-sale securities	8.6	8.9
Agency obligations [Member] | Significant Unobservable Inputs (Level 3) [Member] | Long-term investments [Member]
Assets [Abstract]
Long-term investments: Available-for-sale securities	0.0	0.0
Corporate debt securities [Member] | Short-term investments [Member]
Assets [Abstract]
Short-term investments: Available-for-sale securities	10.2	4.9
Corporate debt securities [Member] | Long-term investments [Member]
Assets [Abstract]
Long-term investments: Available-for-sale securities	121.8	130.9
Corporate debt securities [Member] | Quoted Prices In Active Markets for Identical Assets (Level 1) [Member] | Short-term investments [Member]
Assets [Abstract]
Short-term investments: Available-for-sale securities	0.0	0.0
Corporate debt securities [Member] | Quoted Prices In Active Markets for Identical Assets (Level 1) [Member] | Long-term investments [Member]
Assets [Abstract]
Long-term investments: Available-for-sale securities	0.0	0.0
Corporate debt securities [Member] | Significant Other Observable Inputs (Level 2) [Member] | Short-term investments [Member]
Assets [Abstract]
Short-term investments: Available-for-sale securities	10.2	4.9
Corporate debt securities [Member] | Significant Other Observable Inputs (Level 2) [Member] | Long-term investments [Member]
Assets [Abstract]
Long-term investments: Available-for-sale securities	121.8	130.9
Corporate debt securities [Member] | Significant Unobservable Inputs (Level 3) [Member] | Short-term investments [Member]
Assets [Abstract]
Short-term investments: Available-for-sale securities	0.0	0.0
Corporate debt securities [Member] | Significant Unobservable Inputs (Level 3) [Member] | Long-term investments [Member]
Assets [Abstract]
Long-term investments: Available-for-sale securities	0.0	0.0
Auction rate securities [Member] | Long-term investments [Member]
Assets [Abstract]
Long-term investments: Available-for-sale securities	5.9	13.8
Auction rate securities [Member] | Quoted Prices In Active Markets for Identical Assets (Level 1) [Member] | Long-term investments [Member]
Assets [Abstract]
Long-term investments: Available-for-sale securities	0.0	0.0
Auction rate securities [Member] | Significant Other Observable Inputs (Level 2) [Member] | Long-term investments [Member]
Assets [Abstract]
Long-term investments: Available-for-sale securities	0.0	0.0
Auction rate securities [Member] | Significant Unobservable Inputs (Level 3) [Member] | Long-term investments [Member]
Assets [Abstract]
Long-term investments: Available-for-sale securities	5.9	13.8
Foreign government obligations [Member] | Short-term investments [Member]
Assets [Abstract]
Short-term investments: Available-for-sale securities	2.0	33.7
Foreign government obligations [Member] | Long-term investments [Member]
Assets [Abstract]
Long-term investments: Available-for-sale securities	18.5	17.4
Foreign government obligations [Member] | Quoted Prices In Active Markets for Identical Assets (Level 1) [Member] | Short-term investments [Member]
Assets [Abstract]
Short-term investments: Available-for-sale securities	0.0	0.0
Foreign government obligations [Member] | Quoted Prices In Active Markets for Identical Assets (Level 1) [Member] | Long-term investments [Member]
Assets [Abstract]
Long-term investments: Available-for-sale securities	0.0	0.0
Foreign government obligations [Member] | Significant Other Observable Inputs (Level 2) [Member] | Short-term investments [Member]
Assets [Abstract]
Short-term investments: Available-for-sale securities	2.0	33.7
Foreign government obligations [Member] | Significant Other Observable Inputs (Level 2) [Member] | Long-term investments [Member]
Assets [Abstract]
Long-term investments: Available-for-sale securities	18.5	17.4
Foreign government obligations [Member] | Significant Unobservable Inputs (Level 3) [Member] | Short-term investments [Member]
Assets [Abstract]
Short-term investments: Available-for-sale securities	0.0	0.0
Foreign government obligations [Member] | Significant Unobservable Inputs (Level 3) [Member] | Long-term investments [Member]
Assets [Abstract]
Long-term investments: Available-for-sale securities	0.0	0.0
U.S. government treasury securities [Member] | Short-term investments [Member]
Assets [Abstract]
Short-term investments: Available-for-sale securities		10.9
U.S. government treasury securities [Member] | Long-term investments [Member]
Assets [Abstract]
Long-term investments: Available-for-sale securities	104.8	94.8
U.S. government treasury securities [Member] | Quoted Prices In Active Markets for Identical Assets (Level 1) [Member] | Short-term investments [Member]
Assets [Abstract]
Short-term investments: Available-for-sale securities		10.9
U.S. government treasury securities [Member] | Quoted Prices In Active Markets for Identical Assets (Level 1) [Member] | Long-term investments [Member]
Assets [Abstract]
Long-term investments: Available-for-sale securities	104.8	94.8
U.S. government treasury securities [Member] | Significant Other Observable Inputs (Level 2) [Member] | Short-term investments [Member]
Assets [Abstract]
Short-term investments: Available-for-sale securities		0.0
U.S. government treasury securities [Member] | Significant Other Observable Inputs (Level 2) [Member] | Long-term investments [Member]
Assets [Abstract]
Long-term investments: Available-for-sale securities	0.0	0.0
U.S. government treasury securities [Member] | Significant Unobservable Inputs (Level 3) [Member] | Short-term investments [Member]
Assets [Abstract]
Short-term investments: Available-for-sale securities		0.0
U.S. government treasury securities [Member] | Significant Unobservable Inputs (Level 3) [Member] | Long-term investments [Member]
Assets [Abstract]
Long-term investments: Available-for-sale securities	0.0	0.0
State and local government obligations [Member] | Short-term investments [Member]
Assets [Abstract]
Short-term investments: Available-for-sale securities	3.3	12.7
State and local government obligations [Member] | Long-term investments [Member]
Assets [Abstract]
Long-term investments: Available-for-sale securities	9.7	6.7
State and local government obligations [Member] | Quoted Prices In Active Markets for Identical Assets (Level 1) [Member] | Short-term investments [Member]
Assets [Abstract]
Short-term investments: Available-for-sale securities	0.0	0.0
State and local government obligations [Member] | Quoted Prices In Active Markets for Identical Assets (Level 1) [Member] | Long-term investments [Member]
Assets [Abstract]
Long-term investments: Available-for-sale securities	0.0	0.0
State and local government obligations [Member] | Significant Other Observable Inputs (Level 2) [Member] | Short-term investments [Member]
Assets [Abstract]
Short-term investments: Available-for-sale securities	3.3	12.7
State and local government obligations [Member] | Significant Other Observable Inputs (Level 2) [Member] | Long-term investments [Member]
Assets [Abstract]
Long-term investments: Available-for-sale securities	9.7	6.7
State and local government obligations [Member] | Significant Unobservable Inputs (Level 3) [Member] | Short-term investments [Member]
Assets [Abstract]
Short-term investments: Available-for-sale securities	0.0	0.0
State and local government obligations [Member] | Significant Unobservable Inputs (Level 3) [Member] | Long-term investments [Member]
Assets [Abstract]
Long-term investments: Available-for-sale securities	0.0	0.0
Certificates of deposit [Member] | Short-term investments [Member]
Assets [Abstract]
Short-term investments: Available-for-sale securities		1.0
Certificates of deposit [Member] | Quoted Prices In Active Markets for Identical Assets (Level 1) [Member] | Short-term investments [Member]
Assets [Abstract]
Short-term investments: Available-for-sale securities		0.0
Certificates of deposit [Member] | Significant Other Observable Inputs (Level 2) [Member] | Short-term investments [Member]
Assets [Abstract]
Short-term investments: Available-for-sale securities		1.0
Certificates of deposit [Member] | Significant Unobservable Inputs (Level 3) [Member] | Short-term investments [Member]
Assets [Abstract]
Short-term investments: Available-for-sale securities		0.0
Mortgage and other asset-backed securities [Member] | Long-term investments [Member]
Assets [Abstract]
Long-term investments: Available-for-sale securities	43.2	45.9
Mortgage and other asset-backed securities [Member] | Quoted Prices In Active Markets for Identical Assets (Level 1) [Member] | Long-term investments [Member]
Assets [Abstract]
Long-term investments: Available-for-sale securities	0.0	0.0
Mortgage and other asset-backed securities [Member] | Significant Other Observable Inputs (Level 2) [Member] | Long-term investments [Member]
Assets [Abstract]
Long-term investments: Available-for-sale securities	43.2	45.9
Mortgage and other asset-backed securities [Member] | Significant Unobservable Inputs (Level 3) [Member] | Long-term investments [Member]
Assets [Abstract]
Long-term investments: Available-for-sale securities	$ 0.0	$ 0.0