Consolidated Statements of Comprehensive Operations - USD ($) $ in Millions	3 Months Ended								12 Months Ended
	Dec. 27, 2019	Sep. 27, 2019	Jun. 28, 2019	Mar. 29, 2019	Dec. 28, 2018	Sep. 28, 2018	Jun. 29, 2018	Mar. 30, 2018	Dec. 27, 2019	Dec. 28, 2018	Dec. 29, 2017
Net (loss) income	$ (1,157.1)	$ (1.1)	$ 6.8	$ 154.9	$ (3,718.4)	$ 113.8	$ 15.6	$ (18.0)	$ (996.5)	$ (3,607.0)	$ 2,134.4
Other comprehensive income (loss), net of tax
Unrecognized gain on investments									0.0	0.0	1.5
Currency translation adjustments									18.3	(12.2)	11.3
Unrecognized gain on derivatives, net of tax expense of $0.6, $0.2, and $0.3									1.8	0.7	1.0
Unrecognized (loss) gain on benefit plans, net of tax (benefit) expense of $(1.1), $0.5, and $30.8									(4.2)	1.6	45.8
Total other comprehensive income (loss), net of tax									15.9	(9.9)	59.6
Comprehensive (loss) income									$ (980.6)	$ (3,616.9)	$ 2,194.0