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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 |

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