Fair Value Measurements - Narrative (Details) - USD ($) $ in Millions			3 Months Ended		9 Months Ended
	Sep. 27, 2020	Aug. 09, 2018	Sep. 27, 2020	Sep. 29, 2019	Sep. 27, 2020	Sep. 29, 2019
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Unrealized gain (loss) on investments			$ 155.4	$ 28.5	$ 274.4	$ 129.0
Enphase Shares
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Shares issuable to the Company at closing of agreement	4,500,000	7,500,000
Investment shares sold (in shares)			1,000,000		2,000,000	1,000,000
Proceeds from sale of equity investment			$ 73.3		$ 117.0