Investments & Fair Value Measurements (Schedule Of Financial Assets and Liabilities Carried At Fair Value) (Details) - USD ($) $ in Thousands | 3 Months Ended | 12 Months Ended |
Dec. 25, 2020 | Sep. 25, 2020 |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] | | |
Cash Equivalents, at Carrying Value | $ 1,110,024 | |
Cash and Cash Equivalents, Fair Value Disclosure | | $ 1,071,876 |
Cash and cash equivalents | 1,110,024 | 1,071,876 |
Debt Securities, Available-for-sale, Unrealized Loss | 0 | 0 |
Debt Securities, Available-for-sale, Amortized Cost | 229,269 | 309,067 |
Debt Securities, Available-for-sale | 230,090 | 310,058 |
Debt Securities, Available-for-sale, Unrealized Gain | 0 | |
Investment Owned, Unrecognized Unrealized Depreciation | (8) | (16) |
Cash Cash Equivalents And Investments Total | 1,211,622 | 1,170,973 |
Financial assets carried at fair value | 1,110,024 | 1,071,876 |
Restricted Cash and Cash Equivalents | 9,401 | 8,103 |
Long-term investments | 49,337 | 52,149 |
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than Twelve Months, Fair Value | 17,929 | 9,581 |
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss | (8) | (16) |
Debt Securities, Available-for-sale, Maturity, Allocated and Single Maturity Date, within One Year, Amortized Cost | 185,371 | 261,839 |
Debt Securities, Available-for-sale, Maturity, Allocated and Single Maturity Date, within One Year, Fair Value | 185,581 | 262,085 |
Available For Sale Securities Debt Maturities After One Through Two Years Amortized Cost | 27,538 | 29,328 |
Available For Sale Securities Debt Maturities After One Through Two Years Fair Value | 28,003 | 29,814 |
Available For Sale Securities Debt Maturities After Two Through Three Years Amortized Cost | 16,360 | 17,900 |
Available For Sale Securities Debt Maturities After Two Through Three Years Fair Value | 16,506 | 18,159 |
Investment Owned, at Cost | 1,210,800 | 1,169,983 |
Investment Owned, Unrecognized Unrealized Appreciation | 830 | 1,006 |
Level 1 [Member] | | |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] | | |
Cash and Cash Equivalents, Fair Value Disclosure | 1,109,324 | 1,070,976 |
Financial assets carried at fair value | 1,111,474 | 1,073,979 |
Derivative Asset | | 0 |
Derivative Liability | | 0 |
Level 2 [Member] | | |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] | | |
Cash and Cash Equivalents, Fair Value Disclosure | 700 | 900 |
Financial assets carried at fair value | 95,320 | 92,818 |
Derivative Asset | | 4,267 |
Derivative Liability | | (79) |
Fair Value, Inputs, Level 3 [Member] | | |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] | | |
Derivative Asset | | 0 |
Derivative Liability | | 0 |
Cash [Member] | | |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] | | |
Cash Equivalents, at Carrying Value | 976,704 | |
Cash and Cash Equivalents, Fair Value Disclosure | 976,704 | 856,740 |
Cash [Member] | Level 1 [Member] | | |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] | | |
Cash and Cash Equivalents, Fair Value Disclosure | 976,704 | 856,740 |
Commercial Paper [Member] | | |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] | | |
Cash and Cash Equivalents, Fair Value Disclosure | | 900 |
Money Market Funds [Member] | | |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] | | |
Cash Equivalents, at Carrying Value | 132,620 | |
Cash and Cash Equivalents, Fair Value Disclosure | 132,620 | 214,111 |
Money Market Funds [Member] | Level 1 [Member] | | |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] | | |
Cash and Cash Equivalents, Fair Value Disclosure | 132,620 | 214,111 |
Certificates of Deposit [Member] | | |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] | | |
Cash Equivalents, at Carrying Value | 700 | |
Cash and Cash Equivalents, Fair Value Disclosure | 700 | |
Certificates of Deposit [Member] | Level 2 [Member] | | |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] | | |
Cash and Cash Equivalents, Fair Value Disclosure | 700 | |
Money Market Funds [Member] | | |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] | | |
Cash and Cash Equivalents, Fair Value Disclosure | | 214,111 |
U.S. Agency Securities [Member] | Level 1 [Member] | | |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] | | |
Investments, Noncurrent, Fair Value Disclosure | | 0 |
US Government Agencies Short-term Debt Securities [Member] | | |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] | | |
Debt Securities, Available-for-sale, Unrealized Loss | 0 | |
Debt Securities, Available-for-sale | 1,308 | 1,011 |
Debt Securities, Available-for-sale, Unrealized Gain | 11 | |
US Government Agencies Short-term Debt Securities [Member] | Level 2 [Member] | | |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] | | |
Investments, Fair Value Disclosure | 1,308 | |
Government Bonds [Member] | | |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] | | |
Cash and Cash Equivalents, Fair Value Disclosure | | 125 |
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than Twelve Months, Fair Value | 1,043 | 0 |
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss | 0 | 0 |
Government Bonds [Member] | Level 1 [Member] | | |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] | | |
Cash and Cash Equivalents, Fair Value Disclosure | | 125 |
Government Bonds [Member] | Level 2 [Member] | | |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] | | |
Cash and Cash Equivalents, Fair Value Disclosure | | 0 |
Commercial Paper [Member] | Level 2 [Member] | | |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] | | |
Cash and Cash Equivalents, Fair Value Disclosure | | 900 |
Corporate Debt Securities [Member] | | |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] | | |
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than Twelve Months, Fair Value | 12,628 | 7,076 |
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss | (7) | (10) |
Municipal Bonds [Member] | | |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] | | |
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss | (1) | (6) |
Investment Owned, at Cost | 4,258 | 2,505 |
Short-term Investments [Member] | | |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] | | |
Debt Securities, Available-for-sale, Unrealized Gain | | 248 |
Other Long-term Investments [Member] | | |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] | | |
Investments, Noncurrent, Fair Value Disclosure | 4,800 | 4,200 |
Investments Held In Supplemental Retirement Plan [Member] | Level 1 [Member] | | |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] | | |
Financial assets carried at fair value | 4,396 | 4,279 |
Financial liabilities carried at fair value | 4,396 | 4,279 |
Short-term Investments [Member] | | |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] | | |
Debt Securities, Available-for-sale, Unrealized Loss | | (3) |
Debt Securities, Available-for-sale, Amortized Cost | | 46,703 |
Debt Securities, Available-for-sale | | 46,948 |
Short-term Investments [Member] | Level 1 [Member] | | |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] | | |
Investments, Fair Value Disclosure | 520 | 1,370 |
Short-term Investments [Member] | Level 2 [Member] | | |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] | | |
Investments, Fair Value Disclosure | 51,741 | 45,578 |
Short-term Investments [Member] | Certificates of Deposit [Member] | | |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] | | |
Debt Securities, Available-for-sale, Unrealized Loss | 0 | 0 |
Debt Securities, Available-for-sale, Amortized Cost | 2,175 | 2,277 |
Debt Securities, Available-for-sale | 2,176 | |
Debt Securities, Available-for-sale, Unrealized Gain | 1 | 1 |
Available-for-sale Securities | | 2,278 |
Short-term Investments [Member] | Certificates of Deposit [Member] | Level 2 [Member] | | |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] | | |
Investments, Fair Value Disclosure | 2,176 | 2,278 |
Short-term Investments [Member] | U.S. Agency Securities [Member] | | |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] | | |
Debt Securities, Available-for-sale, Amortized Cost | | 999 |
Short-term Investments [Member] | US Government Agencies Short-term Debt Securities [Member] | | |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] | | |
Debt Securities, Available-for-sale, Unrealized Loss | | 0 |
Debt Securities, Available-for-sale, Amortized Cost | 1,297 | |
Debt Securities, Available-for-sale, Unrealized Gain | | 12 |
Short-term Investments [Member] | US Government Agencies Short-term Debt Securities [Member] | Level 2 [Member] | | |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] | | |
Investments, Fair Value Disclosure | | 1,011 |
Short-term Investments [Member] | Government Bonds [Member] | | |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] | | |
Debt Securities, Available-for-sale, Unrealized Loss | 0 | 0 |
Debt Securities, Available-for-sale, Amortized Cost | 3,905 | 5,118 |
Debt Securities, Available-for-sale | 3,938 | 5,165 |
Debt Securities, Available-for-sale, Unrealized Gain | 33 | 47 |
Short-term Investments [Member] | Government Bonds [Member] | Level 1 [Member] | | |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] | | |
Investments, Fair Value Disclosure | 520 | 1,370 |
Short-term Investments [Member] | Government Bonds [Member] | Level 2 [Member] | | |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] | | |
Investments, Fair Value Disclosure | 3,418 | 3,795 |
Short-term Investments [Member] | Commercial Paper [Member] | | |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] | | |
Debt Securities, Available-for-sale, Unrealized Loss | 0 | 0 |
Debt Securities, Available-for-sale, Amortized Cost | 4,035 | 4,727 |
Debt Securities, Available-for-sale | 4,036 | 4,731 |
Debt Securities, Available-for-sale, Unrealized Gain | 1 | 4 |
Short-term Investments [Member] | Commercial Paper [Member] | Level 2 [Member] | | |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] | | |
Investments, Fair Value Disclosure | 4,036 | 4,731 |
Short-term Investments [Member] | Corporate Debt Securities [Member] | | |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] | | |
Debt Securities, Available-for-sale, Unrealized Loss | (5) | (3) |
Debt Securities, Available-for-sale, Amortized Cost | 19,057 | 18,754 |
Debt Securities, Available-for-sale | 19,104 | 18,838 |
Debt Securities, Available-for-sale, Unrealized Gain | 52 | 87 |
Short-term Investments [Member] | Corporate Debt Securities [Member] | Level 2 [Member] | | |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] | | |
Investments, Fair Value Disclosure | 19,104 | 18,838 |
Short-term Investments [Member] | Municipal Bonds [Member] | | |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] | | |
Debt Securities, Available-for-sale, Unrealized Loss | (1) | 0 |
Debt Securities, Available-for-sale, Amortized Cost | 21,582 | 14,828 |
Debt Securities, Available-for-sale | 21,699 | 14,925 |
Debt Securities, Available-for-sale, Unrealized Gain | 118 | 97 |
Short-term Investments [Member] | Municipal Bonds [Member] | Level 2 [Member] | | |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] | | |
Investments, Fair Value Disclosure | 21,699 | 14,925 |
Short-term Investments [Member] | Short-term Investments [Member] | | |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] | | |
Debt Securities, Available-for-sale, Unrealized Loss | (6) | |
Debt Securities, Available-for-sale, Amortized Cost | 52,051 | |
Debt Securities, Available-for-sale | 52,261 | |
Debt Securities, Available-for-sale, Unrealized Gain | 216 | |
Long-term Investments [Member] | | |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] | | |
Available-for-sale Securities, Amortized Cost Basis | | 51,404 |
Available-for-sale Securities, Accumulated Gross Unrealized Gain, before Tax | | 758 |
Available-for-sale Securities, Accumulated Gross Unrealized Loss, before Tax | | (13) |
Available-for-sale Securities | | 52,149 |
Long-term Investments [Member] | Level 1 [Member] | | |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] | | |
Investments, Noncurrent, Fair Value Disclosure | 1,630 | 1,633 |
Long-term Investments [Member] | Level 2 [Member] | | |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] | | |
Investments, Noncurrent, Fair Value Disclosure | 42,879 | 46,340 |
Long-term Investments [Member] | U.S. Agency Securities [Member] | | |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] | | |
Available-for-sale Securities, Amortized Cost Basis | 1,915 | 2,214 |
Available-for-sale Securities | 1,957 | 2,270 |
Available-for-sale Securities, Gross Unrealized Gain | 42 | 56 |
Available-for-sale Securities, Gross Unrealized Loss | 0 | 0 |
Long-term Investments [Member] | U.S. Agency Securities [Member] | Level 2 [Member] | | |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] | | |
Investments, Noncurrent, Fair Value Disclosure | 1,957 | 2,270 |
Long-term Investments [Member] | Government Bonds [Member] | | |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] | | |
Available-for-sale Securities, Amortized Cost Basis | 5,872 | 5,137 |
Available-for-sale Securities | 5,938 | 5,217 |
Available-for-sale Securities, Gross Unrealized Gain | 66 | 80 |
Available-for-sale Securities, Gross Unrealized Loss | 0 | 0 |
Long-term Investments [Member] | Government Bonds [Member] | Level 1 [Member] | | |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] | | |
Investments, Noncurrent, Fair Value Disclosure | 1,630 | 1,633 |
Long-term Investments [Member] | Government Bonds [Member] | Level 2 [Member] | | |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] | | |
Investments, Noncurrent, Fair Value Disclosure | 4,308 | 3,584 |
Long-term Investments [Member] | Corporate Debt Securities [Member] | | |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] | | |
Available-for-sale Securities, Amortized Cost Basis | 26,082 | 24,657 |
Available-for-sale Securities | 26,461 | 25,069 |
Available-for-sale Securities, Gross Unrealized Gain | 381 | 419 |
Available-for-sale Securities, Gross Unrealized Loss | (2) | (7) |
Long-term Investments [Member] | Corporate Debt Securities [Member] | Level 2 [Member] | | |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] | | |
Investments, Noncurrent, Fair Value Disclosure | 26,461 | 25,069 |
Long-term Investments [Member] | Municipal Bonds [Member] | | |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] | | |
Available-for-sale Securities, Amortized Cost Basis | 10,028 | 15,220 |
Available-for-sale Securities | 10,153 | 15,417 |
Available-for-sale Securities, Gross Unrealized Gain | 125 | 203 |
Available-for-sale Securities, Gross Unrealized Loss | 0 | (6) |
Long-term Investments [Member] | Municipal Bonds [Member] | Level 2 [Member] | | |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] | | |
Investments, Noncurrent, Fair Value Disclosure | 10,153 | 15,417 |
Long-term Investments [Member] | Other Long-term Investments [Member] | | |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] | | |
Available-for-sale Securities, Amortized Cost Basis | 4,828 | 4,176 |
Available-for-sale Securities | 4,828 | 4,176 |
Available-for-sale Securities, Gross Unrealized Gain | 0 | 0 |
Available-for-sale Securities, Gross Unrealized Loss | 0 | 0 |
Long-term Investments [Member] | Other Long-term Investments [Member] | Level 1 [Member] | | |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] | | |
Investments, Noncurrent, Fair Value Disclosure | 0 | 0 |
Long-term Investments [Member] | Long-term Investments [Member] | | |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] | | |
Available-for-sale Securities, Amortized Cost Basis | 48,725 | |
Available-for-sale Securities | 49,337 | |
Available-for-sale Securities, Gross Unrealized Gain | 614 | |
Available-for-sale Securities, Gross Unrealized Loss | (2) | |
Other Current Assets [Member] | Level 1 [Member] | | |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] | | |
Derivative Asset | 0 | |
Other Current Assets [Member] | Level 2 [Member] | | |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] | | |
Derivative Asset | 7,495 | |
Other Current Assets [Member] | Fair Value, Inputs, Level 3 [Member] | | |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] | | |
Derivative Asset | 0 | |
Other Noncurrent Assets [Member] | Level 1 [Member] | | |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] | | |
Derivative Asset | | 0 |
Other Noncurrent Assets [Member] | Level 2 [Member] | | |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] | | |
Derivative Asset | | 369 |
Other Noncurrent Assets [Member] | Fair Value, Inputs, Level 3 [Member] | | |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] | | |
Derivative Asset | | 0 |
Derivative Financial Instruments, Assets [Member] | | |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] | | |
Derivative Financial Instruments, Assets, Amortized Cost Basis | | 0 |
Derivative Financial Instruments, Unrealized Gain | | 4,267 |
Derivative Financial Instruments, Unrealized Loss | | 0 |
Derivative Asset | | 4,267 |
Derivative Financial Instruments, Assets [Member] | Other Current Assets [Member] | | |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] | | |
Derivative Financial Instruments, Assets, Amortized Cost Basis | 0 | |
Derivative Financial Instruments, Unrealized Gain | 7,495 | |
Derivative Financial Instruments, Unrealized Loss | 0 | |
Derivative Asset | $ 7,495 | |
Derivative Financial Instruments, Assets [Member] | Other Noncurrent Assets [Member] | | |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] | | |
Derivative Financial Instruments, Assets, Amortized Cost Basis | | 0 |
Derivative Financial Instruments, Unrealized Gain | | 369 |
Derivative Financial Instruments, Unrealized Loss | | 0 |
Derivative Asset | | 369 |
Derivative Financial Instruments, Liabilities [Member] | | |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] | | |
Derivative Financial Instruments, Unrealized Gain | | 0 |
Derivative Financial Instruments, Unrealized Loss | | (79) |
Derivative Financial Instruments, Liabilities, Amortized Cost Basis | | 0 |
Derivative Liability | | $ (79) |