Debt - Future maturities of long-term debt and amortization of debt issuance cost (Details) - USD ($) $ in Thousands	Sep. 26, 2021	Dec. 31, 2020	Dec. 31, 2019
Debt Disclosure [Abstract]
2021 (remaining three months)	$ 2,765
2021	5,528	$ 5,528
2022	5,528	5,528
2023	5,528	5,528
2024	519,853	5,528
2025		519,857
Thereafter	49,320	149,701
Long-term Debt, Total	588,522	691,670
Debt Issuance Costs, Net [Abstract]
2021 (remaining three months)	703
2021	2,899	3,911
2022	3,019	3,618
2023	3,148	3,344
2024	2,746	3,092
2025		2,450
Thereafter	85	269
Debt Issuance Costs	$ 12,600	$ 16,684	$ 15,065

Amortization of debt issuance costs after year four.

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Amortization of debt issuance costs remainder of fiscal year.

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Amortization of debt issuance costs year five.

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Amortization of debt issuance costs year four.

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Amortization of debt issuance costs year one.

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Amortization of debt issuance costs year three.

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Amortization of debt issuance costs year two.

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Amount, after accumulated amortization, of debt issuance costs. Includes, but is not limited to, legal, accounting, underwriting, printing, and registration costs.

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Amount, after unamortized (discount) premium and debt issuance costs, of long-term debt. Includes, but not limited to, notes payable, bonds payable, debentures, mortgage loans and commercial paper. Excludes capital lease obligations.

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Amount of long-term debt payable, sinking fund requirement, and other securities issued that are redeemable by holder at fixed or determinable price and date, maturing after fifth fiscal year following current fiscal year. Excludes interim and annual periods when interim periods are reported from current statement of financial position date (rolling approach).

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Amount of long-term debt payable, sinking fund requirement, and other securities issued that are redeemable by holder at fixed or determinable price and date, maturing in next fiscal year following current fiscal year. Excludes interim and annual periods when interim periods are reported from current statement of financial position date (rolling approach).

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Amount of long-term debt payable, sinking fund requirement, and other securities issued that are redeemable by holder at fixed or determinable price and date, maturing in fifth fiscal year following current fiscal year. Excludes interim and annual periods when interim periods are reported from current statement of financial position date (rolling approach).

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Amount of long-term debt payable, sinking fund requirement, and other securities issued that are redeemable by holder at fixed or determinable price and date, maturing in fourth fiscal year following current fiscal year. Excludes interim and annual periods when interim periods are reported from current statement of financial position date (rolling approach).

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Amount of long-term debt payable, sinking fund requirement, and other securities issued that are redeemable by holder at fixed or determinable price and date, maturing in third fiscal year following current fiscal year. Excludes interim and annual periods when interim periods are reported from current statement of financial position date (rolling approach).

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Amount of long-term debt payable, sinking fund requirement, and other securities issued that are redeemable by holder at fixed or determinable price and date, maturing in second fiscal year following current fiscal year. Excludes interim and annual periods when interim periods are reported from current statement of financial position date (rolling approach).

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Amount of long-term debt payable, sinking fund requirement, and other securities issued that are redeemable by holder at fixed or determinable price and date, maturing in remainder of current fiscal year.

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