Basis of Presentation and New Accounting Standards - Narrative (Details) $ / shares in Units, $ in Millions	3 Months Ended		12 Months Ended
	Sep. 26, 2021 USD ($) segment $ / shares	Sep. 27, 2020 USD ($) $ / shares	Jun. 27, 2021
Basis of Presentation and Changes in Significant Accounting Policies [Line Items]
Number of reportable segments | segment	1
Gross profit	$ 49.4	$ 35.5
Loss before income taxes	(69.8)	(76.1)
Net loss	$ (70.1)	$ (184.1)
Net loss attributable to controlling interest, basic (USD per share) | $ / shares	$ (0.60)	$ (1.68)
Net loss attributable to controlling interest, diluted (USD per share) | $ / shares	$ (0.60)	$ (1.68)
Service Life
Basis of Presentation and Changes in Significant Accounting Policies [Line Items]
Useful life (in years)	5 years		2 years
Decrease in depreciation expense	$ (8.4)
Change in deprecation expense effect on earnings	1.3
Gross profit	0.5
Loss before income taxes	1.3
Net loss	$ 1.3
Net loss attributable to controlling interest, basic (USD per share) | $ / shares	$ 0.01
Net loss attributable to controlling interest, diluted (USD per share) | $ / shares	$ 0.01
Inventories | Service Life
Basis of Presentation and Changes in Significant Accounting Policies [Line Items]
Inventory adjustments	$ (7.1)