Senior Secured Notes (Details) - USD ($) $ in Thousands		3 Months Ended		6 Months Ended
	Jul. 01, 2021	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020	Dec. 31, 2020	Jun. 17, 2020
Senior Notes [Line Items]
Secured Long-term Debt, Noncurrent		$ 467,807		$ 467,807		$ 460,656
1.50% Senior Secured Convertible Notes Due 2021 [Member]
Senior Notes [Line Items]
Senior Notes, interest rate, stated percentage		1.50%		1.50%		1.50%
Senior Notes, Principal amount		$ 65,485		$ 65,485		$ 65,485
Senior Secured Notes, Unamortized Debt Discount		0		0		1,828
Senior Notes, unamortized deferred financing costs		0		0		175
Secured Long-term Debt, Noncurrent		65,485		65,485		$ 63,482
Interest Expense, Debt		$ 1,100	$ 2,600	$ 2,300	$ 5,400
1.50% Senior Secured Convertible Notes Due 2021 [Member] | Subsequent Event [Member]
Senior Notes [Line Items]
Repayment of 1.50% Senior Convertible Notes due 2021	$ 65,500
10.0% Senior Secured Notes due 2025 [Member]
Senior Notes [Line Items]
Senior Notes, interest rate, stated percentage		10.00%		10.00%		10.00%
Senior Notes, Principal amount		$ 446,675		$ 446,675		$ 446,675	$ 446,700
Senior Secured Notes, Unamortized Debt Discount		34,208		34,208		37,943
Senior Notes, unamortized deferred financing costs		10,145		10,145		11,558
Secured Long-term Debt, Noncurrent		402,322		402,322		397,174
Senior Secured Notes [Member]
Senior Notes [Line Items]
Senior Notes, Principal amount		512,160		512,160		512,160
Senior Secured Notes, Unamortized Debt Discount		34,208		34,208		39,771
Senior Notes, unamortized deferred financing costs		$ 10,145		$ 10,145		$ 11,733