Investment in Unconsolidated Subsidiary (Assets, Liabilities and members' equity) (Details) - USD ($) $ in Thousands	Sep. 30, 2020	Sep. 26, 2020	Jun. 27, 2020	Mar. 28, 2020	Dec. 31, 2019	Dec. 28, 2019	Sep. 28, 2019	Jun. 29, 2019	Mar. 30, 2019	Dec. 29, 2018
ASSETS
Assets, Current		$ 931,174				$ 917,288
Property, plant and equipment, net		1,789,172				1,802,411
Other assets		45,598				47,400
Segment Assets		5,380,986				5,345,258
LIABILITIES AND STOCKHOLDERS’ EQUITY
Current portion of long-term debt		26,185				90,996
Other non-current liabilities		102,559				115,785
Total stockholders’ equity		2,835,189	$ 2,698,354	$ 2,608,442		2,643,350	$ 2,372,892	$ 2,406,635	$ 2,356,699	$ 2,335,821
Liabilities and Equity		$ 5,380,986				$ 5,345,258
Diamond Green Diesel Holdings LLC Joint Venture [Member] | Equity Method Investment, Nonconsolidated Investee or Group of Investees
ASSETS
Assets, Current					$ 668,026
Property, plant and equipment, net					713,489
Other assets					30,710
Segment Assets					1,412,225
LIABILITIES AND STOCKHOLDERS’ EQUITY
Current portion of long-term debt					341
Other Liabilities, Current					75,802
Long-term Debt, Excluding Current Maturities					8,742
Other non-current liabilities					4,422
Total stockholders’ equity					1,322,918
Liabilities and Equity					$ 1,412,225
Diamond Green Diesel Holdings LLC Joint Venture [Member] | Equity Method Investment, Nonconsolidated Investee or Group of Investees | Subsequent Event
ASSETS
Assets, Current	$ 465,669
Property, plant and equipment, net	1,039,802
Other assets	32,813
Segment Assets	1,538,284
LIABILITIES AND STOCKHOLDERS’ EQUITY
Current portion of long-term debt	506
Other Liabilities, Current	98,618
Long-term Debt, Excluding Current Maturities	8,839
Other non-current liabilities	3,875
Total stockholders’ equity	1,426,446
Liabilities and Equity	$ 1,538,284