Marketable Securities (Details) - USD ($) $ in Millions	Jun. 28, 2024	Sep. 29, 2023
Current assets
Debt Securities, Available-for-sale [Line Items]
Marketable securities, current	$ 5.6	$ 15.6
Noncurrent assets
Debt Securities, Available-for-sale [Line Items]
Marketable securities, noncurrent	14.9	4.1
U.S. Treasury and government securities | Current assets
Debt Securities, Available-for-sale [Line Items]
Marketable securities, current	5.2	15.1
U.S. Treasury and government securities | Noncurrent assets
Debt Securities, Available-for-sale [Line Items]
Marketable securities, noncurrent	14.9	4.1
Corporate bonds and notes | Current assets
Debt Securities, Available-for-sale [Line Items]
Marketable securities, current	0.3	0.0
Corporate bonds and notes | Noncurrent assets
Debt Securities, Available-for-sale [Line Items]
Marketable securities, noncurrent	0.0	0.0
Municipal bonds | Current assets
Debt Securities, Available-for-sale [Line Items]
Marketable securities, current	0.1	0.5
Municipal bonds | Noncurrent assets
Debt Securities, Available-for-sale [Line Items]
Marketable securities, noncurrent	$ 0.0	$ 0.0