Earnings Per Share - Computation of Earnings Per Share (Details) - USD ($) $ / shares in Units, shares in Millions, $ in Millions	3 Months Ended				6 Months Ended
	Dec. 28, 2024	Sep. 28, 2024	Dec. 30, 2023	Sep. 30, 2023	Dec. 28, 2024	Dec. 30, 2023
Numerator:
Net loss	$ (60.9)	$ (82.4)	$ (99.1)	$ (67.9)	$ (143.3)	$ (167.0)
Net loss - basic	(60.9)		(99.1)		(143.3)	(167.0)
Net loss - diluted	$ (60.9)		$ (99.1)		$ (143.3)	$ (167.0)
Denominator:
Weighted average common shares outstanding - basic (in shares)	68.9		67.2		68.6	67.0
Weighted average common shares outstanding - diluted (in shares)	68.9		67.2		68.6	67.0
Net loss per share:
Basic (in usd per share)	$ (0.88)		$ (1.47)		$ (2.09)	$ (2.49)
Diluted (in usd per share)	$ (0.88)		$ (1.47)		$ (2.09)	$ (2.49)