Investment in Unconsolidated Subsidiary (Assets, Liabilities and members' equity) (Details) - USD ($) $ in Thousands	Jun. 30, 2020	Jun. 27, 2020	Mar. 28, 2020	Dec. 31, 2019	Dec. 28, 2019	Jun. 29, 2019	Mar. 30, 2019	Dec. 29, 2018
ASSETS
Assets, Current		$ 931,051			$ 917,288
Property, plant and equipment, net		1,773,329			1,802,411
Other assets		41,651			47,400
Segment Assets		5,327,154			5,345,258
LIABILITIES AND STOCKHOLDERS’ EQUITY
Current portion of long-term debt		42,758			90,996
Other non-current liabilities		109,046			115,785
Total stockholders’ equity		2,698,354	$ 2,608,442		2,643,350	$ 2,406,635	$ 2,356,699	$ 2,335,821
Liabilities and Equity		$ 5,327,154			$ 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	$ 581,334
Property, plant and equipment, net	894,415
Other assets	27,959
Segment Assets	1,503,708
LIABILITIES AND STOCKHOLDERS’ EQUITY
Current portion of long-term debt	495
Other Liabilities, Current	89,533
Long-term Debt, Excluding Current Maturities	8,969
Other non-current liabilities	4,023
Total stockholders’ equity	1,400,688
Liabilities and Equity	$ 1,503,708