Fair Value (Schedule Of Financial Instruments Measured At Fair Value On Recurring Basis) (Details) - USD ($) $ in Millions | Dec. 28, 2018 | Sep. 28, 2018 | Sep. 29, 2017 |
Fair Value, Measurements, Recurring [Member] | | | |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | | | |
Cash and cash equivalents | $ 1,085.7 | $ 79.3 | |
Assets, Fair Value Disclosure, Recurring | 1,101.8 | 396.2 | |
Contingent consideration | 3.1 | 3.1 | |
Total | 3.1 | 3.1 | |
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 1 [Member] | | | |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | | | |
Cash and cash equivalents | 1,084.7 | 29.7 | |
Assets, Fair Value Disclosure, Recurring | 1,084.7 | 44.7 | |
Contingent consideration | 0 | 0 | |
Total | 0 | 0 | |
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 2 [Member] | | | |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | | | |
Cash and cash equivalents | 1 | 49.6 | |
Assets, Fair Value Disclosure, Recurring | 17.1 | 351.5 | |
Contingent consideration | 0 | 0 | |
Total | 0 | 0 | |
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 3 [Member] | | | |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | | | |
Cash and cash equivalents | 0 | | $ 0 |
Assets, Fair Value Disclosure, Recurring | 0 | 0 | |
Contingent consideration | 3.1 | 3.1 | |
Total | 3.1 | 3.1 | |
US Treasury and Government [Member] | | | |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | | | |
Available-for-sale Securities | 8 | | |
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 | | 65 | |
US Treasury and Government [Member] | Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 1 [Member] | | | |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | | | |
Available-for-sale Securities | 0 | 15 | |
US Treasury and Government [Member] | Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 2 [Member] | | | |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | | | |
Available-for-sale Securities | 8 | 50 | |
US Treasury and Government [Member] | Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 3 [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, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | | | |
Available-for-sale Securities | 1.4 | | |
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 | | 216 | |
Corporate Debt Securities [Member] | Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 1 [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, Measurements, Recurring [Member] | Fair Value, Inputs, Level 2 [Member] | | | |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | | | |
Available-for-sale Securities | 1.4 | 216 | |
Corporate Debt Securities [Member] | Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 3 [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, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | | | |
Available-for-sale Securities | 4.8 | | |
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 | | 2.8 | |
US States and Political Subdivisions Debt Securities [Member] | Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 1 [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, Measurements, Recurring [Member] | Fair Value, Inputs, Level 2 [Member] | | | |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | | | |
Available-for-sale Securities | 4.8 | 2.8 | |
US States and Political Subdivisions Debt Securities [Member] | Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 3 [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, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | | | |
Available-for-sale Securities | 1.9 | | |
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 | | 33.1 | |
Foreign Government Debt Securities [Member] | Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 1 [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, Measurements, Recurring [Member] | Fair Value, Inputs, Level 2 [Member] | | | |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | | | |
Available-for-sale Securities | 1.9 | $ 33.1 | |
Foreign Government Debt Securities [Member] | Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 3 [Member] | | | |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | | | |
Available-for-sale Securities | $ 0 | | $ 0 |