Fair Value (Schedule Of Financial Instruments Measured At Fair Value On Recurring Basis) (Details) - USD ($) $ in Millions	Sep. 28, 2018	Sep. 29, 2017
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Contingent consideration liability recorded for business combinations	$ 3.1
Available-for-sale Securities	316.9
Fair Value, Measurements, Recurring [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Money market	79.3	$ 592.6
Total	396.2	592.6
Contingent consideration liability recorded for business combinations	3.1	11.9
Total	3.1	11.9
Fair Value, Inputs, Level 1 [Member] | Fair Value, Measurements, Recurring [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Money market	29.7	592.6
Total	44.7	592.6
Contingent consideration liability recorded for business combinations	0.0	0.0
Total	0.0	0.0
Fair Value, Inputs, Level 2 [Member] | Fair Value, Measurements, Recurring [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Money market	49.6	0.0
Total	351.5	0.0
Contingent consideration liability recorded for business combinations	0.0	0.0
Total	0.0	0.0
Fair Value, Inputs, Level 3 [Member] | Fair Value, Measurements, Recurring [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Money market	0.0	0.0
Total	0.0	0.0
Contingent consideration liability recorded for business combinations	3.1	11.9
Total	3.1	11.9
US Treasury and Government [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale Securities	65.0
US Treasury and Government [Member] | Fair Value, Measurements, Recurring [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale Securities		0.0
US Treasury and Government [Member] | Fair Value, Inputs, Level 1 [Member] | Fair Value, Measurements, Recurring [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale Securities	15.0	0.0
US Treasury and Government [Member] | Fair Value, Inputs, Level 2 [Member] | Fair Value, Measurements, Recurring [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale Securities	50.0	0.0
US Treasury and Government [Member] | Fair Value, Inputs, Level 3 [Member] | Fair Value, Measurements, Recurring [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale Securities	0.0	0.0
Corporate Debt Securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale Securities	216.0
Corporate Debt Securities [Member] | Fair Value, Measurements, Recurring [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale Securities		0.0
Corporate Debt Securities [Member] | Fair Value, Inputs, Level 1 [Member] | Fair Value, Measurements, Recurring [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale Securities	0.0	0.0
Corporate Debt Securities [Member] | Fair Value, Inputs, Level 2 [Member] | Fair Value, Measurements, Recurring [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale Securities	216.0	0.0
Corporate Debt Securities [Member] | Fair Value, Inputs, Level 3 [Member] | Fair Value, Measurements, Recurring [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale Securities	0.0	0.0
US States and Political Subdivisions Debt Securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale Securities	2.8
US States and Political Subdivisions Debt Securities [Member] | Fair Value, Measurements, Recurring [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale Securities		0.0
US States and Political Subdivisions Debt Securities [Member] | Fair Value, Inputs, Level 1 [Member] | Fair Value, Measurements, Recurring [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale Securities	0.0	0.0
US States and Political Subdivisions Debt Securities [Member] | Fair Value, Inputs, Level 2 [Member] | Fair Value, Measurements, Recurring [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale Securities	2.8	0.0
US States and Political Subdivisions Debt Securities [Member] | Fair Value, Inputs, Level 3 [Member] | Fair Value, Measurements, Recurring [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale Securities	0.0	0.0
Foreign Government Debt Securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale Securities	33.1
Foreign Government Debt Securities [Member] | Fair Value, Measurements, Recurring [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale Securities		0.0
Foreign Government Debt Securities [Member] | Fair Value, Inputs, Level 1 [Member] | Fair Value, Measurements, Recurring [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale Securities	0.0	0.0
Foreign Government Debt Securities [Member] | Fair Value, Inputs, Level 2 [Member] | Fair Value, Measurements, Recurring [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale Securities	33.1	0.0
Foreign Government Debt Securities [Member] | Fair Value, Inputs, Level 3 [Member] | Fair Value, Measurements, Recurring [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale Securities	$ 0.0	$ 0.0