Fair Value Measurements - Narrative (Details) - USD ($)		3 Months Ended		6 Months Ended
	Aug. 09, 2018	Jun. 28, 2020	Jun. 30, 2019	Jun. 28, 2020	Jun. 30, 2019	Dec. 29, 2019
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Unrealized gain (loss) on investments		$ 71,100,000	$ 67,500,000	$ 119,000,000.0	$ 100,500,000
Equity method investments		292,235,000		292,235,000		$ 226,602,000
Government bonds		6,300,000		6,300,000		6,200,000
Other-than-temporary impairment loss				$ 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	7,500,000
Investment shares sold (in shares)				1,000,000	1,000,000
Proceeds from sale of equity investment		43,700,000
Total equity method investments
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Equity method investments		$ 25,800,000		$ 25,800,000		$ 26,500,000