Debt - Interest expense (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Oct. 02, 2021	Oct. 03, 2020	Oct. 02, 2021	Oct. 03, 2020
Interest expense related to the notes
Interest Expense, Total	$ 6,595	$ 8,604	$ 24,405	$ 25,923
Convertible Senior Notes
Interest expense related to the notes
Contractual interest expense	836	1,365	2,835	4,206
Amortization of debt discount	5,076	6,041	16,005	13,419
Amortization of debt issuance costs	380	546	1,273	1,527
Interest Expense, Total	$ 6,292	$ 7,952	$ 20,113	$ 19,152