Restricted Investments (Details) $ in Thousands		3 Months Ended
	Oct. 01, 2020	Mar. 31, 2020 USD ($)	Dec. 31, 2019 USD ($)
Restricted Investments
Guaranteed interest rate on deposit (as a percent)		0.05
Restricted investments		$ 540,223	$ 533,590
Restricted investments, long-term		$ 408,974	$ 461,757
Forecast
Restricted Investments
Guaranteed interest rate on deposit (as a percent)	0.04